Nos Abonnements
Ressources Électroniques
|
[n° ou bulletin]
[n° ou bulletin]
Vol. 49 N° 11 - Juin 2010 [texte imprimé] . - 2010 . - p. 5027-5488 : ill. ; 28 cm. Chemical engineering Langues : Français (fre)
|
Exemplaires
| Code-barres | Cote | Support | Localisation | Section | Disponibilité |
|---|---|---|---|---|---|
| aucun exemplaire | |||||
|
Dépouillements
Ajouter le résultat dans votre panierInnovative method using magnetic particle tracking to measure solids circulation in a spouted fluidized bed / Emily E. Patterson in Industrial & engineering chemistry research, Vol. 49 N° 11 (Juin 2010)
Titre : Innovative method using magnetic particle tracking to measure solids circulation in a spouted fluidized bed Type de document : texte imprimé Auteurs : Emily E. Patterson, Auteur ; Jack Halow, Auteur Année de publication : 2010 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Magnetic Particle Fluidized Bed Résumé : We describe an innovative method for measuring particle motion inside spouted fluidized beds. The method uses a magnetic tracer particle, which follows the bulk particle flow and is continuously tracked by multiple magnetic field detectors located outside the bed. We analyze signals from the detectors to determine the tracer position at each instant in time. From statistical analysis of the tracer trajectory, characteristic measures of the bulk particle flow, such as the average recirculation frequency, can be determined as a function of operating conditions. For experiments with a range of particle sizes and densities in a 3.9-cm-diameter spouted bed, we find that average solids recirculation rates correlate with excess velocity (superficial minus minimum spouting velocity), particle density, and bed depth. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9008698
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010)[article] Innovative method using magnetic particle tracking to measure solids circulation in a spouted fluidized bed [texte imprimé] / Emily E. Patterson, Auteur ; Jack Halow, Auteur . - 2010.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010)
Mots-clés : Magnetic Particle Fluidized Bed Résumé : We describe an innovative method for measuring particle motion inside spouted fluidized beds. The method uses a magnetic tracer particle, which follows the bulk particle flow and is continuously tracked by multiple magnetic field detectors located outside the bed. We analyze signals from the detectors to determine the tracer position at each instant in time. From statistical analysis of the tracer trajectory, characteristic measures of the bulk particle flow, such as the average recirculation frequency, can be determined as a function of operating conditions. For experiments with a range of particle sizes and densities in a 3.9-cm-diameter spouted bed, we find that average solids recirculation rates correlate with excess velocity (superficial minus minimum spouting velocity), particle density, and bed depth. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9008698 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Effect of asymmetric manipulations in autocatalytic networks Type de document : texte imprimé Auteurs : Sukanya Balasubramanian, Auteur ; Ali Cinar, Auteur ; Fouad Teymour, Auteur Année de publication : 2010 Article en page(s) : pp. 5044–5052 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Autocatalytic Networks Résumé : In this paper, we show that heterogeneous networks can be configured and reconfigured to operate in flexible spatial patterns. The concept is demonstrated by using a square grid of continuous stirred tank reactors with nearest neighbor interactions and hosting multiple cubic autocatalytic species. Asymmetry is introduced in the system by allowing for different feed flow rates in the reactors. A heterogeneous system offers expanded phase space, improved stability, and coexistence characteristics. The advantages of asymmetry are studied using bifurcation diagrams, continuation studies, and dynamics. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901096v
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5044–5052[article] Effect of asymmetric manipulations in autocatalytic networks [texte imprimé] / Sukanya Balasubramanian, Auteur ; Ali Cinar, Auteur ; Fouad Teymour, Auteur . - 2010 . - pp. 5044–5052.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5044–5052
Mots-clés : Autocatalytic Networks Résumé : In this paper, we show that heterogeneous networks can be configured and reconfigured to operate in flexible spatial patterns. The concept is demonstrated by using a square grid of continuous stirred tank reactors with nearest neighbor interactions and hosting multiple cubic autocatalytic species. Asymmetry is introduced in the system by allowing for different feed flow rates in the reactors. A heterogeneous system offers expanded phase space, improved stability, and coexistence characteristics. The advantages of asymmetry are studied using bifurcation diagrams, continuation studies, and dynamics. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901096v Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : CFD simulation of spouted beds using a pressure source term Type de document : texte imprimé Auteurs : Zhiguo Wang, Auteur ; H. T. Bi, Auteur ; C. J. Lim, Auteur Année de publication : 2010 Article en page(s) : pp. 5053–5060 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Granular phase solids phase. Résumé : An integrated granular phase source term was introduced into the vertical momentum balance equation of the solids phase in the annulus region to simulate different flow patterns in the conical spouted bed described in our previous work (Wang et al. Particuology 2006, 4, 194), as well as in a cylindrical spouted bed. This article shows a simple way to estimate the source term from the measured overall pressure drop over the spouted bed. The simulated results were found to agree very well with observed flow patterns and measured local velocity and voidage data, providing a new approach for predicting the flow structure in spouted beds. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901119v?journalCode=iecred
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5053–5060[article] CFD simulation of spouted beds using a pressure source term [texte imprimé] / Zhiguo Wang, Auteur ; H. T. Bi, Auteur ; C. J. Lim, Auteur . - 2010 . - pp. 5053–5060.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5053–5060
Mots-clés : Granular phase solids phase. Résumé : An integrated granular phase source term was introduced into the vertical momentum balance equation of the solids phase in the annulus region to simulate different flow patterns in the conical spouted bed described in our previous work (Wang et al. Particuology 2006, 4, 194), as well as in a cylindrical spouted bed. This article shows a simple way to estimate the source term from the measured overall pressure drop over the spouted bed. The simulated results were found to agree very well with observed flow patterns and measured local velocity and voidage data, providing a new approach for predicting the flow structure in spouted beds. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901119v?journalCode=iecred Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Double X - ray tomography of a bubbling fluidized bed Type de document : texte imprimé Auteurs : R. F. Mudde, Auteur Année de publication : 2010 Article en page(s) : pp. 5061–5065 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : X-ray tomography Fluidized bed Résumé : This paper discusses the measurement of bubbles moving through a fluidized bed imaged with a double X-ray tomographic scanner. The scanner is made of 3 X-ray sources equipped with two rings of 90 CdWO4 detectors. The fluidized bed has a diameter of 23 cm and is filled with a Geldart B powder. The scanner measures the attenuation in two thin parallel slices separated by a small vertical distance. This allows the estimate of the velocity of individual bubbles rising through the bed. Data are collected at a frequency of 2500 Hz. To remove the noise, data are averaged over 10 samples before tomographic reconstruction is performed, resulting in 250 independent frames per second. From the measured bubble velocity and the passage time through the reconstruction planes, the vertical dimensions of the bubbles are found. This allows imaging of the real shape of the bubbles and calculation of the volume of each individual bubble. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901537z
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5061–5065[article] Double X - ray tomography of a bubbling fluidized bed [texte imprimé] / R. F. Mudde, Auteur . - 2010 . - pp. 5061–5065.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5061–5065
Mots-clés : X-ray tomography Fluidized bed Résumé : This paper discusses the measurement of bubbles moving through a fluidized bed imaged with a double X-ray tomographic scanner. The scanner is made of 3 X-ray sources equipped with two rings of 90 CdWO4 detectors. The fluidized bed has a diameter of 23 cm and is filled with a Geldart B powder. The scanner measures the attenuation in two thin parallel slices separated by a small vertical distance. This allows the estimate of the velocity of individual bubbles rising through the bed. Data are collected at a frequency of 2500 Hz. To remove the noise, data are averaged over 10 samples before tomographic reconstruction is performed, resulting in 250 independent frames per second. From the measured bubble velocity and the passage time through the reconstruction planes, the vertical dimensions of the bubbles are found. This allows imaging of the real shape of the bubbles and calculation of the volume of each individual bubble. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901537z Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Superstructure - based optimal synthesis of pressure swing adsorption cycles for precombustion CO2 capture Type de document : texte imprimé Auteurs : Agarwal, Anshul, Auteur ; Lorenz T. Biegler, Auteur ; Stephen E. Zitney, Auteur Année de publication : 2010 Article en page(s) : pp. 5066–5079 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Adsorption Precombustion Résumé : Pressure/vacuum swing adsorption (PSA/VSA) technology has been widely applied for H2 production from the effluent streams of a shift converter, which predominantly comprises H2 and CO2 with other trace components. It also offers significant advantages for precombustion CO2 capture in terms of performance, energy requirements, and operating costs since the shifted synthesis gas (syngas) is available for separation at a high pressure with a high CO2 concentration. Most commercial PSA cycles have been developed to recover H2 at very high purity and do not focus on enriching the strongly adsorbed CO2. Thus, a major limitation exists with the use of these conventional PSA cycles for high purity CO2 capture. Furthermore, complex dynamic behavior of PSA processes together with the numerical difficulties of the model governed by partial differential and algebraic equations (PDAEs) makes the evaluation and assessment of different operating steps and cycle configurations difficult and time-consuming. Therefore, a systematic methodology is essential to design and optimize PSA cycles to recover both H2 and CO2 at a high purity. Recent advances in large-scale optimization strategies for process synthesis have enabled us to address this issue with the help of a systematic optimization-based formulation. In particular, we present a superstructure-based approach to simultaneously determine optimal cycle configurations and design parameters for PSA units. The superstructure is capable to predict a rich set of different PSA operating steps, which are accomplished by manipulating the bed connections with the help of time dependent control variables. An optimal sequence of operating steps is achieved through the formulation of an optimal control problem with the PDAEs of the PSA system. Numerical results for case-studies related to precombustion CO2 capture from a shifted syngas feed mixture having hydrogen and carbon dioxide are presented. In particular, optimal PSA cycles are synthesized which maximize CO2 recovery or minimize overall power consumption. The results show the potential of the superstructure to predict PSA cycles with purities as high as 99% for H2 and 96% for CO2. Moreover, these cycles can recover more than 92% of CO2 with a power consumption as low as 46.8 kW h/tonne CO2 captured. The approach presented is therefore quite useful for evaluating the suitability of different operating strategies for PSA processes. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900873j
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5066–5079[article] Superstructure - based optimal synthesis of pressure swing adsorption cycles for precombustion CO2 capture [texte imprimé] / Agarwal, Anshul, Auteur ; Lorenz T. Biegler, Auteur ; Stephen E. Zitney, Auteur . - 2010 . - pp. 5066–5079.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5066–5079
Mots-clés : Adsorption Precombustion Résumé : Pressure/vacuum swing adsorption (PSA/VSA) technology has been widely applied for H2 production from the effluent streams of a shift converter, which predominantly comprises H2 and CO2 with other trace components. It also offers significant advantages for precombustion CO2 capture in terms of performance, energy requirements, and operating costs since the shifted synthesis gas (syngas) is available for separation at a high pressure with a high CO2 concentration. Most commercial PSA cycles have been developed to recover H2 at very high purity and do not focus on enriching the strongly adsorbed CO2. Thus, a major limitation exists with the use of these conventional PSA cycles for high purity CO2 capture. Furthermore, complex dynamic behavior of PSA processes together with the numerical difficulties of the model governed by partial differential and algebraic equations (PDAEs) makes the evaluation and assessment of different operating steps and cycle configurations difficult and time-consuming. Therefore, a systematic methodology is essential to design and optimize PSA cycles to recover both H2 and CO2 at a high purity. Recent advances in large-scale optimization strategies for process synthesis have enabled us to address this issue with the help of a systematic optimization-based formulation. In particular, we present a superstructure-based approach to simultaneously determine optimal cycle configurations and design parameters for PSA units. The superstructure is capable to predict a rich set of different PSA operating steps, which are accomplished by manipulating the bed connections with the help of time dependent control variables. An optimal sequence of operating steps is achieved through the formulation of an optimal control problem with the PDAEs of the PSA system. Numerical results for case-studies related to precombustion CO2 capture from a shifted syngas feed mixture having hydrogen and carbon dioxide are presented. In particular, optimal PSA cycles are synthesized which maximize CO2 recovery or minimize overall power consumption. The results show the potential of the superstructure to predict PSA cycles with purities as high as 99% for H2 and 96% for CO2. Moreover, these cycles can recover more than 92% of CO2 with a power consumption as low as 46.8 kW h/tonne CO2 captured. The approach presented is therefore quite useful for evaluating the suitability of different operating strategies for PSA processes. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900873j Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Statistical Monitoring of Complex Chemical Processes Using Agent-Based Systems Type de document : texte imprimé Auteurs : Sinem Perk, Auteur ; Fouad Teymour, Auteur ; Ali Cinar, Auteur Année de publication : 2010 Article en page(s) : pp. 5080–5093 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Chemical Processes Résumé : It is highly desirable to have a statistical process monitoring (SPM) system that detects the abnormalities in process operations quickly with as few missed and false alarms as possible while the process operates under various operating conditions. An agent-based combined monitoring and fault detection framework is proposed in this study. In this framework, different SPM techniques compete with and complement each other to enhance detection speed and accuracy. SPM techniques from literature such as principal component analysis (PCA), multiblock PCA (MBPCA), and dynamic PCA (DPCA) techniques are implemented in this agent-based process supervision system. An agent performance assessment and agent management layer provides dynamic adaptation of the supervision system and improves the performance of SPM. The statistical information coming from each of the statistical techniques is summarized through a consensus mechanism. The performance of the agent-based consensus mechanism using different consensus criteria is tested for system disturbances of various magnitudes. The effectiveness of the proposed agent-based framework with different consensus criteria is evaluated based on fault detection times and missed alarm rates and the adaptation of the supervision system is illustrated. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901368j
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5080–5093[article] Statistical Monitoring of Complex Chemical Processes Using Agent-Based Systems [texte imprimé] / Sinem Perk, Auteur ; Fouad Teymour, Auteur ; Ali Cinar, Auteur . - 2010 . - pp. 5080–5093.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5080–5093
Mots-clés : Chemical Processes Résumé : It is highly desirable to have a statistical process monitoring (SPM) system that detects the abnormalities in process operations quickly with as few missed and false alarms as possible while the process operates under various operating conditions. An agent-based combined monitoring and fault detection framework is proposed in this study. In this framework, different SPM techniques compete with and complement each other to enhance detection speed and accuracy. SPM techniques from literature such as principal component analysis (PCA), multiblock PCA (MBPCA), and dynamic PCA (DPCA) techniques are implemented in this agent-based process supervision system. An agent performance assessment and agent management layer provides dynamic adaptation of the supervision system and improves the performance of SPM. The statistical information coming from each of the statistical techniques is summarized through a consensus mechanism. The performance of the agent-based consensus mechanism using different consensus criteria is tested for system disturbances of various magnitudes. The effectiveness of the proposed agent-based framework with different consensus criteria is evaluated based on fault detection times and missed alarm rates and the adaptation of the supervision system is illustrated. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901368j Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Subpilot demonstration of the carbonation − calcination reaction (CCR) process : high - temperature CO2 and sulfur capture from coal - fired power plants Type de document : texte imprimé Auteurs : William Wang, Auteur ; Shwetha Ramkumar, Auteur ; Songgeng Li, Auteur Année de publication : 2010 Article en page(s) : pp. 5094–5101 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Carbonation calcination reaction High temperature. Résumé : Increasing concerns over growing CO2 levels in the atmosphere have led to a worldwide demand for efficient, cost-effective, and clean carbon capture technologies. One of these technologies is the Carbonation−Calcination Reaction (CCR) process, which utilizes a calcium-based sorbent in a high-temperature reaction (carbonation) to capture the CO2 from the flue gas stream and releases a pure stream of CO2 in the subsequent calcination reaction that can be sequestered. A 120 KWth subpilot-scale combustion plant utilizing coal at 20 pph along with natural gas has been established at The Ohio State University to test the CCR process. Experimental studies on CO2 capture using calcium-based sorbents have been performed at this facility. Greater than 99% CO2 and SO2 capture has been achieved at the subpilot-scale facility on a once-through basis at a Ca:C mole ratio of 1.6. In addition, the sorbent reactivity is maintained over multiple cycles by the incorporation of a sorbent reactivation hydration step in the carbonation−calcination cycle. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901509k
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5094–5101[article] Subpilot demonstration of the carbonation − calcination reaction (CCR) process : high - temperature CO2 and sulfur capture from coal - fired power plants [texte imprimé] / William Wang, Auteur ; Shwetha Ramkumar, Auteur ; Songgeng Li, Auteur . - 2010 . - pp. 5094–5101.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5094–5101
Mots-clés : Carbonation calcination reaction High temperature. Résumé : Increasing concerns over growing CO2 levels in the atmosphere have led to a worldwide demand for efficient, cost-effective, and clean carbon capture technologies. One of these technologies is the Carbonation−Calcination Reaction (CCR) process, which utilizes a calcium-based sorbent in a high-temperature reaction (carbonation) to capture the CO2 from the flue gas stream and releases a pure stream of CO2 in the subsequent calcination reaction that can be sequestered. A 120 KWth subpilot-scale combustion plant utilizing coal at 20 pph along with natural gas has been established at The Ohio State University to test the CCR process. Experimental studies on CO2 capture using calcium-based sorbents have been performed at this facility. Greater than 99% CO2 and SO2 capture has been achieved at the subpilot-scale facility on a once-through basis at a Ca:C mole ratio of 1.6. In addition, the sorbent reactivity is maintained over multiple cycles by the incorporation of a sorbent reactivation hydration step in the carbonation−calcination cycle. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901509k Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Experimental and computational fluid dynamics study of dense - phase, transition region, and dilute - phase spouting Type de document : texte imprimé Auteurs : Marcos A. S. Barrozo, Auteur ; Claudio R. Duarte, Auteur ; Norman Epstein, Auteur Année de publication : 2010 Article en page(s) : pp. 5102–5109 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Fluid dynamics Résumé : In this work, the transition between conventional dense-phase spouting and dilute-phase spouting is quantified and characterized on the basis of experimental particle velocity and bed voidage data, obtained with an optical fiber probe, as well as from the evolution of pressure with air velocity. The high gas velocities associated with the dilute-phase spouted bed (DSB) flow regime result in voidages exceeding 0.9 over the entire bed, with no discernible distinction between spout and annulus. The downward particle velocities for the DSB regime differ in magnitude from those in the dense-phase spouting regime. Computational fluid dynamics simulations using the Eulerian granular multiphase model show good agreement with experimental data for the three reproducible flow regimes: dense-phase spouting, transition regime, and dilute-phase spouting. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004892
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5102–5109[article] Experimental and computational fluid dynamics study of dense - phase, transition region, and dilute - phase spouting [texte imprimé] / Marcos A. S. Barrozo, Auteur ; Claudio R. Duarte, Auteur ; Norman Epstein, Auteur . - 2010 . - pp. 5102–5109.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5102–5109
Mots-clés : Fluid dynamics Résumé : In this work, the transition between conventional dense-phase spouting and dilute-phase spouting is quantified and characterized on the basis of experimental particle velocity and bed voidage data, obtained with an optical fiber probe, as well as from the evolution of pressure with air velocity. The high gas velocities associated with the dilute-phase spouted bed (DSB) flow regime result in voidages exceeding 0.9 over the entire bed, with no discernible distinction between spout and annulus. The downward particle velocities for the DSB regime differ in magnitude from those in the dense-phase spouting regime. Computational fluid dynamics simulations using the Eulerian granular multiphase model show good agreement with experimental data for the three reproducible flow regimes: dense-phase spouting, transition regime, and dilute-phase spouting. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004892 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Computational and experimental study of heat transfer and hydrodynamics in a 2D gas − solid fluidized bed reactor Type de document : texte imprimé Auteurs : Mahdi Hamzehei, Auteur ; Hassan Rahimzadeh, Auteur ; Goodarz Ahmadi, Auteur Année de publication : 2010 Article en page(s) : pp. 5110–5121 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Heat Transfer Hydrodynamics. Résumé : The heat transfer and hydrodynamics of a two-dimensional nonreactive gas−solid fluidized bed reactor were studied experimentally and computationally. A multifluid Eulerian computational model incorporating the kinetic theory for solid particles coupled with the k−ε turbulence model was developed and used to simulate the heat conducting gas−solid flows in a fluidized bed configuration. Momentum exchange coefficients were evaluated using the Syamlal−O’Brien, Gidaspow, and Cao−Ahmadi drag functions. Temperature distributions of different phases in the reactor were also computed. Good agreement was found between the model predictions and the experimentally obtained data for the bed expansion ratio as well as the qualitative gas−solid flow patterns. The simulation and experimental results showed that the gas temperature decreases as it moves upward in the reactor, while the solid particle temperature increases. Pressure drop and temperature distribution predicted by the simulations were in good agreement with the experimental measurements at superficial gas velocities higher than the minimum fluidization velocity. Also, the predicted time-average local voidage profiles were in reasonable agreement with the experimental results. The study showed that the computational model was capable of predicting the heat-transfer and the hydrodynamic behavior of gas−solid fluidized bed flows with reasonable accuracy. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900510a
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5110–5121[article] Computational and experimental study of heat transfer and hydrodynamics in a 2D gas − solid fluidized bed reactor [texte imprimé] / Mahdi Hamzehei, Auteur ; Hassan Rahimzadeh, Auteur ; Goodarz Ahmadi, Auteur . - 2010 . - pp. 5110–5121.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5110–5121
Mots-clés : Heat Transfer Hydrodynamics. Résumé : The heat transfer and hydrodynamics of a two-dimensional nonreactive gas−solid fluidized bed reactor were studied experimentally and computationally. A multifluid Eulerian computational model incorporating the kinetic theory for solid particles coupled with the k−ε turbulence model was developed and used to simulate the heat conducting gas−solid flows in a fluidized bed configuration. Momentum exchange coefficients were evaluated using the Syamlal−O’Brien, Gidaspow, and Cao−Ahmadi drag functions. Temperature distributions of different phases in the reactor were also computed. Good agreement was found between the model predictions and the experimentally obtained data for the bed expansion ratio as well as the qualitative gas−solid flow patterns. The simulation and experimental results showed that the gas temperature decreases as it moves upward in the reactor, while the solid particle temperature increases. Pressure drop and temperature distribution predicted by the simulations were in good agreement with the experimental measurements at superficial gas velocities higher than the minimum fluidization velocity. Also, the predicted time-average local voidage profiles were in reasonable agreement with the experimental results. The study showed that the computational model was capable of predicting the heat-transfer and the hydrodynamic behavior of gas−solid fluidized bed flows with reasonable accuracy. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900510a Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : On the effect of subgrid drag closures Type de document : texte imprimé Auteurs : Sofiane Benyahia, Auteur Année de publication : 2010 Article en page(s) : pp. 5122–5131 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Gas solids Résumé : The effect of two subgrid drag closures on the flow of air and Geldart group A particles is presented in this study. A subgrid drag model based on fitting simulation data obtained from finely resolved simulations and a drag model based on the energy minimization approach are both used to solve a gas−solids flow in the riser section of a circulating fluidized bed. The numerical results using a coarse computational grid obtained with these subgrid models are compared with those using a standard drag model as well as experimental data obtained in a pilot-scale riser. Numerical predictions using both subgrid models showed higher solids hold-up in the riser indicated by the radial solids density and axial pressure drop profiles in the 2D and 3D system geometries considered in this study. These subgrid models are demonstrated to be both needed and useful as large-scale numerical simulations commonly use coarse computational grids that are unable to resolve the smallest heterogeneous structures observed in the fluidization of small particles. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900658k?journalCode=iecred
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5122–5131[article] On the effect of subgrid drag closures [texte imprimé] / Sofiane Benyahia, Auteur . - 2010 . - pp. 5122–5131.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5122–5131
Mots-clés : Gas solids Résumé : The effect of two subgrid drag closures on the flow of air and Geldart group A particles is presented in this study. A subgrid drag model based on fitting simulation data obtained from finely resolved simulations and a drag model based on the energy minimization approach are both used to solve a gas−solids flow in the riser section of a circulating fluidized bed. The numerical results using a coarse computational grid obtained with these subgrid models are compared with those using a standard drag model as well as experimental data obtained in a pilot-scale riser. Numerical predictions using both subgrid models showed higher solids hold-up in the riser indicated by the radial solids density and axial pressure drop profiles in the 2D and 3D system geometries considered in this study. These subgrid models are demonstrated to be both needed and useful as large-scale numerical simulations commonly use coarse computational grids that are unable to resolve the smallest heterogeneous structures observed in the fluidization of small particles. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900658k?journalCode=iecred Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Computations of fluid dynamics of a 50 MWe circulating fluidized bed combustor Type de document : texte imprimé Auteurs : Liu Guodong, Auteur ; Sun Dan, Auteur ; Huilin Lu, Auteur Année de publication : 2010 Article en page(s) : pp. 5132–5140 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Fluid dynamics Résumé : Gas−particle two-phase turbulent flows are numerically studied in a 50 MWe circulating fluidized bed combustor. The dense flow of particles is modeled by the frictional stress models adopted from solid mechanics theory, and the dilute flow in the so-called rapid granular flow regime is modeled from the kinetic theory of granular flow. At low concentrations the viscosity due to the effect of the presence of particles is modeled by means of a semiempirical viscosity for fluidized catalytic cracking particles. The distribution of the velocity and concentration of particles in a circulating fluidized bed combustor is predicted. Simulations indicate that the dense regime with a high concentration of particles is in the bottom part and the dilute regime with a low concentration in the upper part of the furnace. The effect of secondary air on the flow behavior is analyzed, and the penetration length of the secondary air jet is computed in a 50 MWe circulating fluidized bed combustor. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901103t
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5132–5140[article] Computations of fluid dynamics of a 50 MWe circulating fluidized bed combustor [texte imprimé] / Liu Guodong, Auteur ; Sun Dan, Auteur ; Huilin Lu, Auteur . - 2010 . - pp. 5132–5140.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5132–5140
Mots-clés : Fluid dynamics Résumé : Gas−particle two-phase turbulent flows are numerically studied in a 50 MWe circulating fluidized bed combustor. The dense flow of particles is modeled by the frictional stress models adopted from solid mechanics theory, and the dilute flow in the so-called rapid granular flow regime is modeled from the kinetic theory of granular flow. At low concentrations the viscosity due to the effect of the presence of particles is modeled by means of a semiempirical viscosity for fluidized catalytic cracking particles. The distribution of the velocity and concentration of particles in a circulating fluidized bed combustor is predicted. Simulations indicate that the dense regime with a high concentration of particles is in the bottom part and the dilute regime with a low concentration in the upper part of the furnace. The effect of secondary air on the flow behavior is analyzed, and the penetration length of the secondary air jet is computed in a 50 MWe circulating fluidized bed combustor. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901103t Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Direct quadrature method of moments for the mixing of inert polydisperse fluidized powders and the role of numerical diffusion Type de document : texte imprimé Auteurs : Luca Mazzei, Auteur ; Daniele L. Marchisio, Auteur ; Paola Lettieri, Auteur Année de publication : 2010 Article en page(s) : pp 5141–5152 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Numerical diffusion Résumé : Computational fluid dynamics (CFD) is extensively employed to investigate dense fluidized suspensions. Most mathematical models assume that the powder is monodisperse or is formed by few solid phases of particles with constant size. Real powders, nevertheless, are polydisperse, with their particle size distribution continuously changing in time and space. To account for this important feature, models have to include a population balance equation (PBE), which needs to be solved along with the customary fluid dynamic transport equations. The recently developed direct quadrature method of moments (DQMOM) permits solving PBEs in commercial CFD codes at relatively low computational cost. This technique, nevertheless, still needs testing in the context of dense multiphase flows. In this work we implement DQMOM within the CFD code Fluent to study the mixing of two polydisperse fluidized suspensions initially segregated. Each node of the quadrature represents a distinct solid phase advected with its own velocity. Simulating this apparently simple system highlights a problem related to the numerical solution of the DQMOM transport equations: these do not feature diffusive terms, but the numerical diffusion generated by the finite-volume integration method alters the model predictions, leading to wrong results. To solve this, the PBE needs to account for diffusion: this yields source terms in the transport equations of the quadrature weights and nodes that ensure the latter are correctly predicted. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901116y
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp 5141–5152[article] Direct quadrature method of moments for the mixing of inert polydisperse fluidized powders and the role of numerical diffusion [texte imprimé] / Luca Mazzei, Auteur ; Daniele L. Marchisio, Auteur ; Paola Lettieri, Auteur . - 2010 . - pp 5141–5152.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp 5141–5152
Mots-clés : Numerical diffusion Résumé : Computational fluid dynamics (CFD) is extensively employed to investigate dense fluidized suspensions. Most mathematical models assume that the powder is monodisperse or is formed by few solid phases of particles with constant size. Real powders, nevertheless, are polydisperse, with their particle size distribution continuously changing in time and space. To account for this important feature, models have to include a population balance equation (PBE), which needs to be solved along with the customary fluid dynamic transport equations. The recently developed direct quadrature method of moments (DQMOM) permits solving PBEs in commercial CFD codes at relatively low computational cost. This technique, nevertheless, still needs testing in the context of dense multiphase flows. In this work we implement DQMOM within the CFD code Fluent to study the mixing of two polydisperse fluidized suspensions initially segregated. Each node of the quadrature represents a distinct solid phase advected with its own velocity. Simulating this apparently simple system highlights a problem related to the numerical solution of the DQMOM transport equations: these do not feature diffusive terms, but the numerical diffusion generated by the finite-volume integration method alters the model predictions, leading to wrong results. To solve this, the PBE needs to account for diffusion: this yields source terms in the transport equations of the quadrature weights and nodes that ensure the latter are correctly predicted. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901116y Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Unsteady shear of dense assemblies of cohesive granular materials under constant volume conditions Type de document : texte imprimé Auteurs : Lee R. Aarons, Auteur ; Jin Sun, Auteur ; Sankaran Sundaresan, Auteur Année de publication : 2010 Article en page(s) : pp. 5153–5165 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Granular materials Résumé : The response characteristics of dense assemblies of cohesive granular materials to unsteady simple shear in the quasi-static regime are investigated through discrete element method (DEM) simulations of monodisperse spherical and frictional particles in periodic domains at constant volume. The dynamics of the volume-averaged normal and shear stresses in materials, undergoing stop-and-go shearing and oscillatory shear, are studied in detail. Furthermore, the evolution of microstructure anisotropy has been quantified through a fabric tensor. The stresses and the microstructure anisotropy depend on the strain extent but not on the shear rate. They both undergo a transition following reversal of shear direction, which requires a shear strain of order unity to fully adapt. The results reveal a correlation between the stress evolution and the microstructure anisotropy development. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901187w
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5153–5165[article] Unsteady shear of dense assemblies of cohesive granular materials under constant volume conditions [texte imprimé] / Lee R. Aarons, Auteur ; Jin Sun, Auteur ; Sankaran Sundaresan, Auteur . - 2010 . - pp. 5153–5165.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5153–5165
Mots-clés : Granular materials Résumé : The response characteristics of dense assemblies of cohesive granular materials to unsteady simple shear in the quasi-static regime are investigated through discrete element method (DEM) simulations of monodisperse spherical and frictional particles in periodic domains at constant volume. The dynamics of the volume-averaged normal and shear stresses in materials, undergoing stop-and-go shearing and oscillatory shear, are studied in detail. Furthermore, the evolution of microstructure anisotropy has been quantified through a fabric tensor. The stresses and the microstructure anisotropy depend on the strain extent but not on the shear rate. They both undergo a transition following reversal of shear direction, which requires a shear strain of order unity to fully adapt. The results reveal a correlation between the stress evolution and the microstructure anisotropy development. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901187w Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Experimental and CFD analyses of bubble parameters in a variable - thickness fluidized bed Type de document : texte imprimé Auteurs : Lyczkowski, Robert W., Auteur ; Jacques X. Bouillard, Auteur ; Isaac K. Gamwo, Auteur Année de publication : 2010 Article en page(s) : pp. 5166–5173 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Analyse Fluidized Bed Résumé : Bubble characteristics in a variable-thickness fluidized bed containing nine tubes were experimentally investigated by analyzing absolute and differential pressure fluctuations. The latter were obtained from vertically aligned probes traversing the bed interior for three bed thicknesses: thin, square, and full. The important bubble parameters, namely, frequencies, effective diameters, and velocities, were determined by analyzing autocorrelations and cross-correlations obtained from these differential pressure signals for the thin and square beds. Wall effects were assessed by comparing the pressure fluctuations as the bed thickness was increased from thin to square. It was found that bubbles move faster within and above the tube bank than below it. This behavior was also found to be more pronounced in the wall regions of the full bed, which might explain why some commercial fluidized-bed combustors experience unusual metal wastage near their tube supports. Although bubble sizes consistently agreed between thin and square beds, bubble velocity reduction was observed for the thin bed. The experimental thin-bed differential pressure measurements were analyzed using a two-phase computational fluid dynamics (CFD) hydrodynamic model. Excellent agreement was obtained between the experimental results and predictions from our hydrodynamic model for autocorrelations, cross-correlations, power spectral densities, and bubble parameters. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901294e
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5166–5173[article] Experimental and CFD analyses of bubble parameters in a variable - thickness fluidized bed [texte imprimé] / Lyczkowski, Robert W., Auteur ; Jacques X. Bouillard, Auteur ; Isaac K. Gamwo, Auteur . - 2010 . - pp. 5166–5173.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5166–5173
Mots-clés : Analyse Fluidized Bed Résumé : Bubble characteristics in a variable-thickness fluidized bed containing nine tubes were experimentally investigated by analyzing absolute and differential pressure fluctuations. The latter were obtained from vertically aligned probes traversing the bed interior for three bed thicknesses: thin, square, and full. The important bubble parameters, namely, frequencies, effective diameters, and velocities, were determined by analyzing autocorrelations and cross-correlations obtained from these differential pressure signals for the thin and square beds. Wall effects were assessed by comparing the pressure fluctuations as the bed thickness was increased from thin to square. It was found that bubbles move faster within and above the tube bank than below it. This behavior was also found to be more pronounced in the wall regions of the full bed, which might explain why some commercial fluidized-bed combustors experience unusual metal wastage near their tube supports. Although bubble sizes consistently agreed between thin and square beds, bubble velocity reduction was observed for the thin bed. The experimental thin-bed differential pressure measurements were analyzed using a two-phase computational fluid dynamics (CFD) hydrodynamic model. Excellent agreement was obtained between the experimental results and predictions from our hydrodynamic model for autocorrelations, cross-correlations, power spectral densities, and bubble parameters. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901294e Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Quadrature - based moment model for moderately dense polydisperse gas − particle flows Type de document : texte imprimé Auteurs : Rodney O. Fox, Auteur ; Prakash Vedula, Auteur Année de publication : 2010 Article en page(s) : pp. 5174–5187 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Gas particle flows Résumé : A quadrature-based moment model is derived for moderately dense polydisperse gas−particle flows starting from the inelastic Boltzmann−Enskog kinetic equation including terms for particle acceleration (e.g., gravity and fluid drag). The derivation is carried out for the joint number density function, f(t,x,m,u), of particle mass and velocity, and thus, the model can describe the transport of polydisperse particles with size and density differences. The transport equations for the integer moments of the velocity distribution function are derived in exact form for all values of the coefficient of restitution for particle−particle collisions. For particular limiting cases, the moment model is shown to be consistent with hydrodynamic models for gas−particle flows. However, the moment model is more general than the hydrodynamic models because its derivation does not require that the particle Knudsen number (and Mach number) be small. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9013138
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5174–5187[article] Quadrature - based moment model for moderately dense polydisperse gas − particle flows [texte imprimé] / Rodney O. Fox, Auteur ; Prakash Vedula, Auteur . - 2010 . - pp. 5174–5187.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5174–5187
Mots-clés : Gas particle flows Résumé : A quadrature-based moment model is derived for moderately dense polydisperse gas−particle flows starting from the inelastic Boltzmann−Enskog kinetic equation including terms for particle acceleration (e.g., gravity and fluid drag). The derivation is carried out for the joint number density function, f(t,x,m,u), of particle mass and velocity, and thus, the model can describe the transport of polydisperse particles with size and density differences. The transport equations for the integer moments of the velocity distribution function are derived in exact form for all values of the coefficient of restitution for particle−particle collisions. For particular limiting cases, the moment model is shown to be consistent with hydrodynamic models for gas−particle flows. However, the moment model is more general than the hydrodynamic models because its derivation does not require that the particle Knudsen number (and Mach number) be small. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9013138 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Boiling of dilute emulsions — toward a new modeling framework Type de document : texte imprimé Auteurs : Matthew L. Roesle, Auteur ; F. A. Kulacki, Auteur Année de publication : 2010 Article en page(s) : pp. 5188–5196 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Emulsions Boiling process Résumé : Boiling of emulsions is a field that has been studied little and is poorly understood. Experiments have shown that boiling in emulsion is a complex phenomenon and that a wide range of behaviors are possible. A model of boiling emulsions put forward by one group of researchers provides some explanation for the behavior of emulsions but seems to be insufficiently detailed to provide deeper insight into the boiling process or prediction of boiling. In this paper, a review of work to-date is presented. We also suggest an alternative set of mechanisms for boiling in dilute emulsions. It is shown how these mechanisms may be integrated into the Euler−Euler model of multiphase flow to describe the overall behavior of boiling emulsions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9013259
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5188–5196[article] Boiling of dilute emulsions — toward a new modeling framework [texte imprimé] / Matthew L. Roesle, Auteur ; F. A. Kulacki, Auteur . - 2010 . - pp. 5188–5196.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5188–5196
Mots-clés : Emulsions Boiling process Résumé : Boiling of emulsions is a field that has been studied little and is poorly understood. Experiments have shown that boiling in emulsion is a complex phenomenon and that a wide range of behaviors are possible. A model of boiling emulsions put forward by one group of researchers provides some explanation for the behavior of emulsions but seems to be insufficiently detailed to provide deeper insight into the boiling process or prediction of boiling. In this paper, a review of work to-date is presented. We also suggest an alternative set of mechanisms for boiling in dilute emulsions. It is shown how these mechanisms may be integrated into the Euler−Euler model of multiphase flow to describe the overall behavior of boiling emulsions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9013259 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Studies on speciation changes and mass distribution of mercury in a bituminous coal - fired power plant by combining field data and chemical equilibrium calculation Type de document : texte imprimé Auteurs : Jeong-Hun Kim, Auteur ; Deepak Pudasainee, Auteur ; Young-Sik Yoon, Auteur Année de publication : 2010 Article en page(s) : pp. 5197–5203 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Chemical equilibrium calculation Résumé : Transformation of mercury compounds in combustion flue gas and overall mercury mass balance in a typical bituminous coal-fired power plant were studied. Upon decreasing temperature and interaction with flue gas components, oxidized mercury increased across an electrostatic precipitator. A major fraction of particulate mercury was removed in the electrostatic precipitator, and oxidized mercury was removed in wet flue gas desulfurization. Hg was mainly speciated into elemental form in the stack emission. The measurement of mercury in a real facility and equilibrium calculation showed that coal composition, operating conditions, and flue gas components were the major factors affecting mercury emission and speciation. A reliable overall Hg mass balance was obtained from the field measurement. Mercury mainly entered from coal, and lime/limestone feeding was distributed in electrostatic precipitator fly ash (57.6−64.3%), gypsum (4.5 −12.9%), effluents (0.5−1.9%), and stack emission (15.2−27.0%). Further, the mass distribution and speciation of mercury in the power plant with simulated coal mixture feeds could be predicted with a chemical equilibrium code in combination with the measured results at the commercial plant. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901361q
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5197–5203[article] Studies on speciation changes and mass distribution of mercury in a bituminous coal - fired power plant by combining field data and chemical equilibrium calculation [texte imprimé] / Jeong-Hun Kim, Auteur ; Deepak Pudasainee, Auteur ; Young-Sik Yoon, Auteur . - 2010 . - pp. 5197–5203.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5197–5203
Mots-clés : Chemical equilibrium calculation Résumé : Transformation of mercury compounds in combustion flue gas and overall mercury mass balance in a typical bituminous coal-fired power plant were studied. Upon decreasing temperature and interaction with flue gas components, oxidized mercury increased across an electrostatic precipitator. A major fraction of particulate mercury was removed in the electrostatic precipitator, and oxidized mercury was removed in wet flue gas desulfurization. Hg was mainly speciated into elemental form in the stack emission. The measurement of mercury in a real facility and equilibrium calculation showed that coal composition, operating conditions, and flue gas components were the major factors affecting mercury emission and speciation. A reliable overall Hg mass balance was obtained from the field measurement. Mercury mainly entered from coal, and lime/limestone feeding was distributed in electrostatic precipitator fly ash (57.6−64.3%), gypsum (4.5 −12.9%), effluents (0.5−1.9%), and stack emission (15.2−27.0%). Further, the mass distribution and speciation of mercury in the power plant with simulated coal mixture feeds could be predicted with a chemical equilibrium code in combination with the measured results at the commercial plant. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901361q Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Using janus particles to control mixing and segregation of adhesive particle systems Type de document : texte imprimé Auteurs : I. Figueroa, Auteur ; J. J. McCarthy, Auteur Année de publication : 2010 Article en page(s) : pp. 5204–5214 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Particle systems Résumé : Processing of fine powders is a relevant operation in many industries, from pharmaceuticals to material synthesis. As the size of the particles decreases, adhesive forces become important and can have a nontrivial, but difficult to predict, impact on the mixing/segregation tendency of the material. The aim of this work is to control the final asymptotic state of adhesive systems through the addition of “helper” particles that can either promote mixing or segregation. These amphiphilic “helper” particles—also called Janus particles—act as bridges between particles, alternatively promoting mixing in a system that would otherwise segregate (surfactant particles) or separating a specific kind of particle from a mixture (extractant particles). Phase-space diagrams of the expected behavior are analytically identified by comparing the interaction forces in the system: the strengths of those that promote mixing are compared with the ones that enhance segregation (including those interactions bridged by Janus particles), and the final state of the system is determined by the interactions that predominate. The predictions are then tested against results obtained by two-dimensional discrete element method (DEM) simulations of the system including Janus particles, which are further compared to both the binary adhesive system and the free-flowing case. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9013716
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5204–5214[article] Using janus particles to control mixing and segregation of adhesive particle systems [texte imprimé] / I. Figueroa, Auteur ; J. J. McCarthy, Auteur . - 2010 . - pp. 5204–5214.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5204–5214
Mots-clés : Particle systems Résumé : Processing of fine powders is a relevant operation in many industries, from pharmaceuticals to material synthesis. As the size of the particles decreases, adhesive forces become important and can have a nontrivial, but difficult to predict, impact on the mixing/segregation tendency of the material. The aim of this work is to control the final asymptotic state of adhesive systems through the addition of “helper” particles that can either promote mixing or segregation. These amphiphilic “helper” particles—also called Janus particles—act as bridges between particles, alternatively promoting mixing in a system that would otherwise segregate (surfactant particles) or separating a specific kind of particle from a mixture (extractant particles). Phase-space diagrams of the expected behavior are analytically identified by comparing the interaction forces in the system: the strengths of those that promote mixing are compared with the ones that enhance segregation (including those interactions bridged by Janus particles), and the final state of the system is determined by the interactions that predominate. The predictions are then tested against results obtained by two-dimensional discrete element method (DEM) simulations of the system including Janus particles, which are further compared to both the binary adhesive system and the free-flowing case. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9013716 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Implicit continuum mechanics approach to heat conduction in granular materials Type de document : texte imprimé Auteurs : Mehrdad Massoudi, Auteur ; Morteza M. Mehrabadi, Auteur Année de publication : 2010 Article en page(s) : pp. 5215–5221 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Mechanics Granular materials Résumé : In this paper, we derive a properly frame-invariant implicit constitutive relationship for the heat flux vector for a granular medium (or a density-gradient-type fluid). The heat flux vector is commonly modeled by Fourier’s law of heat conduction, and for complex materials such as nonlinear fluids, porous media, or granular materials, the coefficient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematic parameters such as temperature, shear rate, porosity, concentration, etc. In this paper, we extend the approach of Massoudi [Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1585; Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1599], who provided explicit constitutive relations for the heat flux vector for flowing granular materials; in order to do so, we use the implicit scheme suggested by Fox [Fox, N. Int. J. Eng. Sci. 1969, 7, 437], who obtained implicit relations in thermoelasticity. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9014155
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5215–5221[article] Implicit continuum mechanics approach to heat conduction in granular materials [texte imprimé] / Mehrdad Massoudi, Auteur ; Morteza M. Mehrabadi, Auteur . - 2010 . - pp. 5215–5221.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5215–5221
Mots-clés : Mechanics Granular materials Résumé : In this paper, we derive a properly frame-invariant implicit constitutive relationship for the heat flux vector for a granular medium (or a density-gradient-type fluid). The heat flux vector is commonly modeled by Fourier’s law of heat conduction, and for complex materials such as nonlinear fluids, porous media, or granular materials, the coefficient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematic parameters such as temperature, shear rate, porosity, concentration, etc. In this paper, we extend the approach of Massoudi [Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1585; Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1599], who provided explicit constitutive relations for the heat flux vector for flowing granular materials; in order to do so, we use the implicit scheme suggested by Fox [Fox, N. Int. J. Eng. Sci. 1969, 7, 437], who obtained implicit relations in thermoelasticity. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9014155 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Solution of population balance equations by the finite size domain complete set of trial functions method of moments (FCMOM) for inhomogeneous systems Type de document : texte imprimé Auteurs : Matteo Strumendo, Auteur ; Hamid Arastoopour, Auteur Année de publication : 2010 Article en page(s) : pp. 5222–5230 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Inhomogeneous Systems Résumé : The FCMOM (finite size domain complete set of trial functions method of moments) is an efficient and accurate numerical technique to solve monovariate and bivariate population balance equations. It was previously formulated for homogeneous systems. In this paper, the FCMOM approach is extended to solve monovariate population balance equations for inhomogeneous (spatially not uniform) systems. In the FCMOM, the method of moments is formulated in a finite domain of the internal coordinates and the particle size distribution function is represented as a truncated series expansion by a complete system of orthonormal functions. The FCMOM is extended to inhomogeneous systems assuming that the particle-phase convective velocity is independent of the internal variables (particle size). The method is illustrated by applications to particle diffusion and to particle convection. In the case of particle convection, a gas−solid dilute flow in a pipe was simulated and the FCMOM equations were coupled with the governing equations (mass and momentum balances) of the gas phase. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901407x
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5222–5230[article] Solution of population balance equations by the finite size domain complete set of trial functions method of moments (FCMOM) for inhomogeneous systems [texte imprimé] / Matteo Strumendo, Auteur ; Hamid Arastoopour, Auteur . - 2010 . - pp. 5222–5230.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5222–5230
Mots-clés : Inhomogeneous Systems Résumé : The FCMOM (finite size domain complete set of trial functions method of moments) is an efficient and accurate numerical technique to solve monovariate and bivariate population balance equations. It was previously formulated for homogeneous systems. In this paper, the FCMOM approach is extended to solve monovariate population balance equations for inhomogeneous (spatially not uniform) systems. In the FCMOM, the method of moments is formulated in a finite domain of the internal coordinates and the particle size distribution function is represented as a truncated series expansion by a complete system of orthonormal functions. The FCMOM is extended to inhomogeneous systems assuming that the particle-phase convective velocity is independent of the internal variables (particle size). The method is illustrated by applications to particle diffusion and to particle convection. In the case of particle convection, a gas−solid dilute flow in a pipe was simulated and the FCMOM equations were coupled with the governing equations (mass and momentum balances) of the gas phase. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901407x Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Mathematical modeling and numerical simulation of methane production in a hydrate reservoir Type de document : texte imprimé Auteurs : Isaac K. Gamwo, Auteur Année de publication : 2010 Article en page(s) : pp. 5231–5245 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Methane Hydrate Reservoir Résumé : Methane hydrate, a potential future energy resource, is known to occur naturally in vast quantities beneath the ocean floor and in permafrost regions. It is important to evaluate how much methane is recoverable from these hydrate reserves. This article introduces the theoretical background of HydrateResSim, the National Energy Technology Laboratory (NETL) methane production simulator for hydrate-containing reservoirs, originally developed for NETL by Lawrence Berkeley National Laboratory (LBNL). It describes the mathematical model that governs the dissociation of methane hydrate by depressurization or thermal stimulation of the system, including the transport of multiple temperature-dependent components in multiple phases through a porous medium. The model equations are obtained by incorporating the multiphase Darcy’s law for gas and liquid into both the mass component balances and the energy conservation equations. Two submodels in HydrateResSim for hydrate dissociation are also considered: a kinetic model and a pure thermodynamic model. Contrary to more traditional reservoir simulations, the set of model unknowns or primary variables in HydrateResSim changes throughout the simulation as a result of the formation or dissociation of ice and hydrate phases during the simulation. The primary variable switch method (PVSM) is used to effectively track these phase changes. The equations are solved by utilizing the implicit time finite-difference method on the grid system, which can properly describe phase appearance or disappearance as well as the boundary conditions. The Newton−Raphson method is used to solve the linear equations after discretization and setup of the Jacobian matrix. We report here the application of HydrateResSim to a three-component, four-phase flow system in order to predict the methane produced from a laboratory-scale reservoir. The first results of HydrateResSim code in a peer-reviewed publication are presented in this article. The numerical solution was verified against the state-of-the art simulator TOUGH+Hydrate. The model was then used to compare two dissociation theories: kinetic and pure equilibrium. Generally, the kinetic model revealed a lower dissociation rate than the equilibrium model. The hydrate dissociation patterns differed significantly when the thermal boundary condition was shifted from adiabatic to constant-temperature. The surface area factor was found to have an important effect on the rate of hydrate dissociation for the kinetic model. The deviation between the kinetic and equilibrium models was found to increase with decreasing surface area factor. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901407x
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5231–5245[article] Mathematical modeling and numerical simulation of methane production in a hydrate reservoir [texte imprimé] / Isaac K. Gamwo, Auteur . - 2010 . - pp. 5231–5245.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5231–5245
Mots-clés : Methane Hydrate Reservoir Résumé : Methane hydrate, a potential future energy resource, is known to occur naturally in vast quantities beneath the ocean floor and in permafrost regions. It is important to evaluate how much methane is recoverable from these hydrate reserves. This article introduces the theoretical background of HydrateResSim, the National Energy Technology Laboratory (NETL) methane production simulator for hydrate-containing reservoirs, originally developed for NETL by Lawrence Berkeley National Laboratory (LBNL). It describes the mathematical model that governs the dissociation of methane hydrate by depressurization or thermal stimulation of the system, including the transport of multiple temperature-dependent components in multiple phases through a porous medium. The model equations are obtained by incorporating the multiphase Darcy’s law for gas and liquid into both the mass component balances and the energy conservation equations. Two submodels in HydrateResSim for hydrate dissociation are also considered: a kinetic model and a pure thermodynamic model. Contrary to more traditional reservoir simulations, the set of model unknowns or primary variables in HydrateResSim changes throughout the simulation as a result of the formation or dissociation of ice and hydrate phases during the simulation. The primary variable switch method (PVSM) is used to effectively track these phase changes. The equations are solved by utilizing the implicit time finite-difference method on the grid system, which can properly describe phase appearance or disappearance as well as the boundary conditions. The Newton−Raphson method is used to solve the linear equations after discretization and setup of the Jacobian matrix. We report here the application of HydrateResSim to a three-component, four-phase flow system in order to predict the methane produced from a laboratory-scale reservoir. The first results of HydrateResSim code in a peer-reviewed publication are presented in this article. The numerical solution was verified against the state-of-the art simulator TOUGH+Hydrate. The model was then used to compare two dissociation theories: kinetic and pure equilibrium. Generally, the kinetic model revealed a lower dissociation rate than the equilibrium model. The hydrate dissociation patterns differed significantly when the thermal boundary condition was shifted from adiabatic to constant-temperature. The surface area factor was found to have an important effect on the rate of hydrate dissociation for the kinetic model. The deviation between the kinetic and equilibrium models was found to increase with decreasing surface area factor. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901407x Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Numerical Analysis of Solids Mixing in Pressurized Fluidized Beds Type de document : texte imprimé Auteurs : Niels G. Deen, Auteur ; Godlieb Willem, Auteur ; Gorter Sander, Auteur Année de publication : 2010 Article en page(s) : pp. 5246–5253 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Fluidized Beds Numerical Analysis Résumé : In the production and processing of granular matter, mixing of solids plays an important role. Granular materials such as sand, polymeric particles, and fertilizers are processed in different apparatuses such as fluidized beds, rotary kilns, and spouted beds. In the operation of these apparatuses, proper mixing is essential, as it helps to prevent the formation of hot spots, off-specification products, and undesired agglomerates. In this article, we discuss various methods that are available to give quantitative information on the solids mixing state in granular systems based on a discrete description of the solids phase. We apply the different methods to two-fluid model simulations. It is found that some of these methods are grid-dependent; not reproducible; sensitive to macroscopic flow patterns; and/or able to calculate only overall mixing indices, rather than indices for each direction. We compare some methods described in the literature, and in addition, we propose two new methods that do not suffer from the disadvantages mentioned above. Simulations are performed for seven different operating pressures. It is found that mixing improves with operating pressure as a result of increased porosity in the dense phase. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9014843
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5246–5253[article] Numerical Analysis of Solids Mixing in Pressurized Fluidized Beds [texte imprimé] / Niels G. Deen, Auteur ; Godlieb Willem, Auteur ; Gorter Sander, Auteur . - 2010 . - pp. 5246–5253.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5246–5253
Mots-clés : Fluidized Beds Numerical Analysis Résumé : In the production and processing of granular matter, mixing of solids plays an important role. Granular materials such as sand, polymeric particles, and fertilizers are processed in different apparatuses such as fluidized beds, rotary kilns, and spouted beds. In the operation of these apparatuses, proper mixing is essential, as it helps to prevent the formation of hot spots, off-specification products, and undesired agglomerates. In this article, we discuss various methods that are available to give quantitative information on the solids mixing state in granular systems based on a discrete description of the solids phase. We apply the different methods to two-fluid model simulations. It is found that some of these methods are grid-dependent; not reproducible; sensitive to macroscopic flow patterns; and/or able to calculate only overall mixing indices, rather than indices for each direction. We compare some methods described in the literature, and in addition, we propose two new methods that do not suffer from the disadvantages mentioned above. Simulations are performed for seven different operating pressures. It is found that mixing improves with operating pressure as a result of increased porosity in the dense phase. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9014843 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Slugging flow of water draining from the bottom of a nonvented container Type de document : texte imprimé Auteurs : Charles W. Solbrig, Auteur ; Jeffrey B. Sherman, Auteur Année de publication : 2010 Article en page(s) : pp. 5254–5262 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Water Nonvented Container Résumé : Experiments were run to measure the slugging frequency and drain rate of water exiting through an orifice at the bottom of a nonvented container into an infinite atmosphere. Initially, the container is nearly full of water with a small air space on top. Upon initially opening the orifice, water drains out until the air pressure above the water reduces enough that the air pressure drop from inside to outside of the container supports the water column and the water stops flowing. Air then enters the container through the orifice forming a bubble, which grows until it detaches and bubbles up through the water to reach the air space. Once the bubble enters, this added air increases the pressure in the air space enough to allow the water to start flowing out again. This cycle of flow out, flow stoppage, air inflow, and bubble breakoff continues over and over until the hole is closed or the container empties. This is referred to as the “slugging cycle.” A simple model is presented here which can be used to calculate water flow rate out of and air flow into a nonvented container. This paper presents the description of experiments, data obtained, the model, and comparison of the model to the data. The model predicts outflow rates close to experimental values. Measurements showed that flow rates from nonvented containers are more than 10 to 20 times less than vented containers. For nonvented flow, the bubbles which must enter the container periodically to increase the internal air pressure stop the water flow momentarily so are responsible for this large decrease in flow rate. Swirl induced in the nonvented container allows flow rates to increase by a factor of 2. The flow rate out of a nonvented container is independent of water height which differs from a vented container where the flow rate is proportional to the square root of the water height. The constant rate is due to the container air pressure because the higher the water level is, the lower the air pressure is. This analytical model requires input of the bubble size. The volume recommended is the volume of a cylinder with the base of the orifice area and length of 3.3 cm. Slugging frequency varies only a small amount falling in the range of 2−4 cycles/s. Preliminary work with other containers indicates that larger containers, larger orifices, and nozzle exit shapes produce higher flow rates per unit area but similar slugging rates. An interesting observation is the following: The air pressure in the container is always negative and can be observed without a gauge. It equals the negative of the water height. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901498d
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5254–5262[article] Slugging flow of water draining from the bottom of a nonvented container [texte imprimé] / Charles W. Solbrig, Auteur ; Jeffrey B. Sherman, Auteur . - 2010 . - pp. 5254–5262.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5254–5262
Mots-clés : Water Nonvented Container Résumé : Experiments were run to measure the slugging frequency and drain rate of water exiting through an orifice at the bottom of a nonvented container into an infinite atmosphere. Initially, the container is nearly full of water with a small air space on top. Upon initially opening the orifice, water drains out until the air pressure above the water reduces enough that the air pressure drop from inside to outside of the container supports the water column and the water stops flowing. Air then enters the container through the orifice forming a bubble, which grows until it detaches and bubbles up through the water to reach the air space. Once the bubble enters, this added air increases the pressure in the air space enough to allow the water to start flowing out again. This cycle of flow out, flow stoppage, air inflow, and bubble breakoff continues over and over until the hole is closed or the container empties. This is referred to as the “slugging cycle.” A simple model is presented here which can be used to calculate water flow rate out of and air flow into a nonvented container. This paper presents the description of experiments, data obtained, the model, and comparison of the model to the data. The model predicts outflow rates close to experimental values. Measurements showed that flow rates from nonvented containers are more than 10 to 20 times less than vented containers. For nonvented flow, the bubbles which must enter the container periodically to increase the internal air pressure stop the water flow momentarily so are responsible for this large decrease in flow rate. Swirl induced in the nonvented container allows flow rates to increase by a factor of 2. The flow rate out of a nonvented container is independent of water height which differs from a vented container where the flow rate is proportional to the square root of the water height. The constant rate is due to the container air pressure because the higher the water level is, the lower the air pressure is. This analytical model requires input of the bubble size. The volume recommended is the volume of a cylinder with the base of the orifice area and length of 3.3 cm. Slugging frequency varies only a small amount falling in the range of 2−4 cycles/s. Preliminary work with other containers indicates that larger containers, larger orifices, and nozzle exit shapes produce higher flow rates per unit area but similar slugging rates. An interesting observation is the following: The air pressure in the container is always negative and can be observed without a gauge. It equals the negative of the water height. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901498d Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : In situ measurements of gas fluidized nanoagglomerates Type de document : texte imprimé Auteurs : Jose A. Quevedo, Auteur ; Robert Pfeffer, Auteur Année de publication : 2010 Article en page(s) : pp. 5263–5269 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Gas Fluidized Résumé : The size of fluidized agglomerates of nanoparticles was successfully measured in situ in conventional and microjet assisted gas fluidized beds by using Lasentec Focused Beam Reflectance Method (FBRM) and Particle Vision Measurement (PVM) probes. In situ particle size distributions and agglomerate images of Aerosil R974 and Aerosil 90 nanopowders were obtained. This was achieved by reducing the electrostatic charge in the fluidized bed by bubbling the gas through an alcohol−water solution before entering the bed. Failure to remove electrostatic charges resulted in blocking of the probe lenses and blurred images or spiky size distributions. The agglomerate size distributions show that Aerosil R974 agglomerates (APF-type nanopowder) are smaller and less dense than Aerosil 90 agglomerates (ABF-type nanopowder). These observations match their respective fluidization behavior and confirm that the APF−ABF classification is dependent on the size and density of the agglomerates. The application of the microjet assisting method results in a further reduction in the mean size and density of the agglomerates and explains the higher quality of fluidization and larger bed expansion observed with the microjet. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9015446
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5263–5269[article] In situ measurements of gas fluidized nanoagglomerates [texte imprimé] / Jose A. Quevedo, Auteur ; Robert Pfeffer, Auteur . - 2010 . - pp. 5263–5269.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5263–5269
Mots-clés : Gas Fluidized Résumé : The size of fluidized agglomerates of nanoparticles was successfully measured in situ in conventional and microjet assisted gas fluidized beds by using Lasentec Focused Beam Reflectance Method (FBRM) and Particle Vision Measurement (PVM) probes. In situ particle size distributions and agglomerate images of Aerosil R974 and Aerosil 90 nanopowders were obtained. This was achieved by reducing the electrostatic charge in the fluidized bed by bubbling the gas through an alcohol−water solution before entering the bed. Failure to remove electrostatic charges resulted in blocking of the probe lenses and blurred images or spiky size distributions. The agglomerate size distributions show that Aerosil R974 agglomerates (APF-type nanopowder) are smaller and less dense than Aerosil 90 agglomerates (ABF-type nanopowder). These observations match their respective fluidization behavior and confirm that the APF−ABF classification is dependent on the size and density of the agglomerates. The application of the microjet assisting method results in a further reduction in the mean size and density of the agglomerates and explains the higher quality of fluidization and larger bed expansion observed with the microjet. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9015446 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Verification of continuum models for solids momentum transfer by means of discrete element method Type de document : texte imprimé Auteurs : Payman Jalali, Auteur ; Timo Hyppanen, Auteur Année de publication : 2010 Article en page(s) : pp. 5270–5278 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Solids Momentum Transfer Résumé : This paper focuses on the study of momentum transfer rate between granular phases in particulate flows that interact in low and moderate volume fractions. Two systems have been created and simulated. The first system included two granular phases initially mixed homogeneously in a vessel with rectangular cross section. The second system included two granular phases as two concentric cylinders initially separated, but one phase was stationary and the other phase penetrated across a circular opening to the other phase. In one hand, discrete element method (DEM) was employed as the particle trajectory following method, and on the other hand, an Eulerian approach was used as the continuum model to study the momentum transfer between granular phases. The results are also assessed based on the formula derived by Syamlal [Syamlal, M. The Particle−Particle Drag Term in a Multiparticle Model of Fluidization. Topical Report, DOE/MC/21353-2373, NTIS/DE87006500, National Technical Information Service, Springfield, VA. 1987] for the solid−solid momentum transfer rate. This formula yields solid−solid drag forces larger than those obtained from the DEM simulations especially as volume fraction grows. Our results revealed that in the Eulerian model (in FLUENT) the relative velocity of granular phases during the interacting period may not be influenced only by the solid−solid drag force. Though the two approaches calculate qualitatively similar results in time, there are quantitative differences in calculation of phase volume fractions and the momentum of phases. The interacting phases are highly scattered in the Eulerian model predictions, which may be due to larger drag forces and a lower energy dissipation rate existing in the model. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901538w
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5270–5278[article] Verification of continuum models for solids momentum transfer by means of discrete element method [texte imprimé] / Payman Jalali, Auteur ; Timo Hyppanen, Auteur . - 2010 . - pp. 5270–5278.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5270–5278
Mots-clés : Solids Momentum Transfer Résumé : This paper focuses on the study of momentum transfer rate between granular phases in particulate flows that interact in low and moderate volume fractions. Two systems have been created and simulated. The first system included two granular phases initially mixed homogeneously in a vessel with rectangular cross section. The second system included two granular phases as two concentric cylinders initially separated, but one phase was stationary and the other phase penetrated across a circular opening to the other phase. In one hand, discrete element method (DEM) was employed as the particle trajectory following method, and on the other hand, an Eulerian approach was used as the continuum model to study the momentum transfer between granular phases. The results are also assessed based on the formula derived by Syamlal [Syamlal, M. The Particle−Particle Drag Term in a Multiparticle Model of Fluidization. Topical Report, DOE/MC/21353-2373, NTIS/DE87006500, National Technical Information Service, Springfield, VA. 1987] for the solid−solid momentum transfer rate. This formula yields solid−solid drag forces larger than those obtained from the DEM simulations especially as volume fraction grows. Our results revealed that in the Eulerian model (in FLUENT) the relative velocity of granular phases during the interacting period may not be influenced only by the solid−solid drag force. Though the two approaches calculate qualitatively similar results in time, there are quantitative differences in calculation of phase volume fractions and the momentum of phases. The interacting phases are highly scattered in the Eulerian model predictions, which may be due to larger drag forces and a lower energy dissipation rate existing in the model. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901538w Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Coexistence of solidlike and fluidlike states in a deep gas - fluidized bed Type de document : texte imprimé Auteurs : Junwu Wang, Auteur ; M. A. van der Hoef, Auteur Année de publication : 2010 Article en page(s) : pp. 5279–5287 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Gas fluidized beds Résumé : Characterizing regime transition in gas-fluidized beds is of fundamental importance for the successful applications of fluidization technology. In this study, we show that a state-of-the-art two-fluid model has the ability to correctly predict the transition from packed bed to fully bubbling fluidized beds. To this end, we have studied a deep gas fluidized bed, in which the process of transition is shown much more clearly (see Figure 1) compared to relatively shallow fluidized beds. Particularly, we show that in the process of regime transition, the solidlike and fluidlike states can coexist. We conclude this on the basis of visual observation, global bed pressure drop signals, local solid volume fraction signals, cross-sectional averaged axial granular temperature profiles, and radial particle velocity profiles. The presence of the coexisting phases can be easily understood from the fact that the gas phase is compressible. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901555p
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5279–5287[article] Coexistence of solidlike and fluidlike states in a deep gas - fluidized bed [texte imprimé] / Junwu Wang, Auteur ; M. A. van der Hoef, Auteur . - 2010 . - pp. 5279–5287.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5279–5287
Mots-clés : Gas fluidized beds Résumé : Characterizing regime transition in gas-fluidized beds is of fundamental importance for the successful applications of fluidization technology. In this study, we show that a state-of-the-art two-fluid model has the ability to correctly predict the transition from packed bed to fully bubbling fluidized beds. To this end, we have studied a deep gas fluidized bed, in which the process of transition is shown much more clearly (see Figure 1) compared to relatively shallow fluidized beds. Particularly, we show that in the process of regime transition, the solidlike and fluidlike states can coexist. We conclude this on the basis of visual observation, global bed pressure drop signals, local solid volume fraction signals, cross-sectional averaged axial granular temperature profiles, and radial particle velocity profiles. The presence of the coexisting phases can be easily understood from the fact that the gas phase is compressible. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901555p Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Computational fluid dynamics simulation of fluid catalytic cracking in a rotating fluidized bed in a static geometry Type de document : texte imprimé Auteurs : Waldo Rosales Trujillo, Auteur ; Juray De Wilde, Auteur Année de publication : 2010 Article en page(s) : pp. 5288–5298 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Fluid Dynamics Résumé : The application of a rotating fluidized bed in a static geometry to fluid catalytic cracking is evaluated by means of computational fluid dynamics (CFD) simulations using an Eulerian−Eulerian model and the kinetic theory of granular flow. The reactions are described by a 10-lump model. First, the reaction kinetics is based on currently allowable cracking temperature and catalyst activity. Typical reactor dimensions required are presented, and an evaluation of the process intensification potential is made, based on a comparison with riser technology. Next, the possibility of using a higher cracking temperature or a more active catalyst is evaluated. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901610f
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5288–5298[article] Computational fluid dynamics simulation of fluid catalytic cracking in a rotating fluidized bed in a static geometry [texte imprimé] / Waldo Rosales Trujillo, Auteur ; Juray De Wilde, Auteur . - 2010 . - pp. 5288–5298.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5288–5298
Mots-clés : Fluid Dynamics Résumé : The application of a rotating fluidized bed in a static geometry to fluid catalytic cracking is evaluated by means of computational fluid dynamics (CFD) simulations using an Eulerian−Eulerian model and the kinetic theory of granular flow. The reactions are described by a 10-lump model. First, the reaction kinetics is based on currently allowable cracking temperature and catalyst activity. Typical reactor dimensions required are presented, and an evaluation of the process intensification potential is made, based on a comparison with riser technology. Next, the possibility of using a higher cracking temperature or a more active catalyst is evaluated. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901610f Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Emulsion stability in the presence of nonionic surfactant micelles : role of micellar ordering and ostwald ripening Type de document : texte imprimé Auteurs : Youngsun Kong, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur Année de publication : 2010 Article en page(s) : pp. 5299–5303 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Emulsion Micellar Ordering Résumé : The phenomenon of surfactant micelle ordering (i.e., stratification) in emulsion films was investigated using the reflected-light microinterferometric technique. In thinning films formed from a nonionic micellar solution of ethoxylated alcohol (1 wt %), it was found that the small droplets (i.e., less than 5 µm) are separated by thick (>0.1 µm) stable films containing surfactant micelles in multilayers that prevent droplet flocculation and coalescence. The Ostwald ripening process governs emulsion stability over a long-term. The direct microscopic observations of the evolution of the drop size distribution over time of hexadecane drops (25 vol %) dispersed in an aqueous micellar solution (≈ 120 times critical micellar concentration) was compared with that calculated from the Ostwald ripening model. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901825c
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5299–5303[article] Emulsion stability in the presence of nonionic surfactant micelles : role of micellar ordering and ostwald ripening [texte imprimé] / Youngsun Kong, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur . - 2010 . - pp. 5299–5303.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5299–5303
Mots-clés : Emulsion Micellar Ordering Résumé : The phenomenon of surfactant micelle ordering (i.e., stratification) in emulsion films was investigated using the reflected-light microinterferometric technique. In thinning films formed from a nonionic micellar solution of ethoxylated alcohol (1 wt %), it was found that the small droplets (i.e., less than 5 µm) are separated by thick (>0.1 µm) stable films containing surfactant micelles in multilayers that prevent droplet flocculation and coalescence. The Ostwald ripening process governs emulsion stability over a long-term. The direct microscopic observations of the evolution of the drop size distribution over time of hexadecane drops (25 vol %) dispersed in an aqueous micellar solution (≈ 120 times critical micellar concentration) was compared with that calculated from the Ostwald ripening model. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901825c Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Extraction of transport coefficients from molecular dynamics simulations of granular flows : A perspective Type de document : texte imprimé Auteurs : Christine M. Hrenya, Auteur Année de publication : 2010 Article en page(s) : pp 5304–5309 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Molecular Dynamics Résumé : Molecular dynamics (MD) simulations of solids flows provide a useful tool for extracting transport coefficients needed for the closure of continuum models. This “empirical” approach is particularly powerful for systems with complex interactions—nonspherical particles, cohesive particles, etc.—that are difficult to handle with first-principles (e.g., kinetic-theory-based) approaches. Nonetheless, the extraction of such quantities is characterized by several subtleties which may lead to inaccuracies if ignored. In this work, four such complexities are illustrated: (i) the presence of clustering instabilities, (ii) the a priori need for the general form of the flux law, (iii) the presence of more than one transport coefficient in a given flux law, and (iv) the presence of Knudsen (higher-order) effects. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901859v
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp 5304–5309[article] Extraction of transport coefficients from molecular dynamics simulations of granular flows : A perspective [texte imprimé] / Christine M. Hrenya, Auteur . - 2010 . - pp 5304–5309.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp 5304–5309
Mots-clés : Molecular Dynamics Résumé : Molecular dynamics (MD) simulations of solids flows provide a useful tool for extracting transport coefficients needed for the closure of continuum models. This “empirical” approach is particularly powerful for systems with complex interactions—nonspherical particles, cohesive particles, etc.—that are difficult to handle with first-principles (e.g., kinetic-theory-based) approaches. Nonetheless, the extraction of such quantities is characterized by several subtleties which may lead to inaccuracies if ignored. In this work, four such complexities are illustrated: (i) the presence of clustering instabilities, (ii) the a priori need for the general form of the flux law, (iii) the presence of more than one transport coefficient in a given flux law, and (iv) the presence of Knudsen (higher-order) effects. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901859v Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Numerical study on the effect of the air jets at the inlet distributor in the gas − solids circulating fluidized - bed risers Type de document : texte imprimé Auteurs : Botao Peng, Auteur ; Jesse Zhu, Auteur ; Chao Zhang, Auteur Année de publication : 2010 Article en page(s) : pp. 5310–5322 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Air Jets Gas solids Résumé : This work numerically conducted a comprehensive study on the jet effect of inlet distributor arrangements on the flow structure of gas−solids two-phase flow in circulating fluidized-bed risers. A computational fluid dynamics (CFD) model based on the Eulerian−Eulerian approach coupled with granular kinetics theory was adopted to carry out the simulation. Simulation results were compared with the experimental data. It was found that the inlet distributor has a great effect on the entire flow structure. The numerical results using jet inlet approaches predicted more distinct core-annulus flow structures mimicking the experimental results while the uniform inlet condition predicted a very flat flow structure. The jet effect of the inlet distributor is clearly revealed. A large lateral flow can be seen because of the jet effect. A reasonable CFD model needs to take into account the inlet distributor configuration and consider the jet effect at the inlet. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901902j
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5310–5322[article] Numerical study on the effect of the air jets at the inlet distributor in the gas − solids circulating fluidized - bed risers [texte imprimé] / Botao Peng, Auteur ; Jesse Zhu, Auteur ; Chao Zhang, Auteur . - 2010 . - pp. 5310–5322.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5310–5322
Mots-clés : Air Jets Gas solids Résumé : This work numerically conducted a comprehensive study on the jet effect of inlet distributor arrangements on the flow structure of gas−solids two-phase flow in circulating fluidized-bed risers. A computational fluid dynamics (CFD) model based on the Eulerian−Eulerian approach coupled with granular kinetics theory was adopted to carry out the simulation. Simulation results were compared with the experimental data. It was found that the inlet distributor has a great effect on the entire flow structure. The numerical results using jet inlet approaches predicted more distinct core-annulus flow structures mimicking the experimental results while the uniform inlet condition predicted a very flat flow structure. The jet effect of the inlet distributor is clearly revealed. A large lateral flow can be seen because of the jet effect. A reasonable CFD model needs to take into account the inlet distributor configuration and consider the jet effect at the inlet. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901902j Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : An updated review of synthesis parameters and growth mechanisms for carbon nanotubes in fluidized beds Type de document : texte imprimé Auteurs : Kieran J. MacKenzie, Auteur ; Oscar M. Dunens, Auteur ; Andrew T. Harris, Auteur Année de publication : 2010 Article en page(s) : pp. 5323–5338 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Carbon Nanotubes Résumé : Research published since 2006 on the synthesis of carbon nanotubes (CNTs) using chemical vapor deposition (CVD) in a fluidized bed reactor is reviewed. A complete account of experimental procedures, including upstream treatments (catalyst preparation, calcination, and reduction), synthesis conditions, and downstream processes (purification) is presented in an attempt to determine the effect of these variables on carbon nanotube morphology, diameter, yield, and quality. The formation and growth mechanisms of carbon nanotubes by CVD is reviewed in detail in an attempt to account for discrepancies in the properties of CNTs produced from experiments at superficially similar conditions. This reveals that the underlying variables that appear to control growth are not directly manipulated in the CVD process; rather they are determined by complex interactions between variables. Thus, the current “change-one-factor-at-a-time” experimental paradigm, which assumes orthogonal variables, is the most likely source of the conflicting experimental results reported in the literature, and does not give insight into CNT growth or permit “global” process optimization. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9019787
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5323–5338[article] An updated review of synthesis parameters and growth mechanisms for carbon nanotubes in fluidized beds [texte imprimé] / Kieran J. MacKenzie, Auteur ; Oscar M. Dunens, Auteur ; Andrew T. Harris, Auteur . - 2010 . - pp. 5323–5338.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5323–5338
Mots-clés : Carbon Nanotubes Résumé : Research published since 2006 on the synthesis of carbon nanotubes (CNTs) using chemical vapor deposition (CVD) in a fluidized bed reactor is reviewed. A complete account of experimental procedures, including upstream treatments (catalyst preparation, calcination, and reduction), synthesis conditions, and downstream processes (purification) is presented in an attempt to determine the effect of these variables on carbon nanotube morphology, diameter, yield, and quality. The formation and growth mechanisms of carbon nanotubes by CVD is reviewed in detail in an attempt to account for discrepancies in the properties of CNTs produced from experiments at superficially similar conditions. This reveals that the underlying variables that appear to control growth are not directly manipulated in the CVD process; rather they are determined by complex interactions between variables. Thus, the current “change-one-factor-at-a-time” experimental paradigm, which assumes orthogonal variables, is the most likely source of the conflicting experimental results reported in the literature, and does not give insight into CNT growth or permit “global” process optimization. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9019787 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Synthesis of an N , N - Bis(phosphonomethyl)glycine anion - intercalated layered double hydroxide and its selective infrared absorption effect in low density polyethylene films for use in agriculture Type de document : texte imprimé Auteurs : Lijing Wang, Auteur ; Xiangyu Xu, Auteur ; David G. Evans, Auteur Année de publication : 2010 Article en page(s) : pp. 5339–5346 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Hydroxide Résumé : Reaction under alkaline conditions of N,N-bis(phosphonomethyl)glycine (glyphosine, GLYP) with an MgAl-NO3-layered double hydroxide (LDH) precursor, prepared by a method involving separate nucleation and aging steps (SNAS) led to the replacement of the interlayer nitrate anions by GLYP3− anions. The resulting MgAl-GLYP-LDH was characterized by X-ray diffraction (XRD), Fourier transfrom infrared (FT-IR), thermogravimetry and differential therm analysis (TG-DTA), elemental analysis, and scanning electron microscopy (SEM). MgAl-GLYP-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filled with MgAl-GLYP-LDH showed a higher mid- to far-infrared absorption than films filled with MgAl-CO3-LDH in the 7−25 μm range, particularly in the key 9−11 μm range required for application in agricultural plastic films. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9016978
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5339–5346[article] Synthesis of an N , N - Bis(phosphonomethyl)glycine anion - intercalated layered double hydroxide and its selective infrared absorption effect in low density polyethylene films for use in agriculture [texte imprimé] / Lijing Wang, Auteur ; Xiangyu Xu, Auteur ; David G. Evans, Auteur . - 2010 . - pp. 5339–5346.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5339–5346
Mots-clés : Hydroxide Résumé : Reaction under alkaline conditions of N,N-bis(phosphonomethyl)glycine (glyphosine, GLYP) with an MgAl-NO3-layered double hydroxide (LDH) precursor, prepared by a method involving separate nucleation and aging steps (SNAS) led to the replacement of the interlayer nitrate anions by GLYP3− anions. The resulting MgAl-GLYP-LDH was characterized by X-ray diffraction (XRD), Fourier transfrom infrared (FT-IR), thermogravimetry and differential therm analysis (TG-DTA), elemental analysis, and scanning electron microscopy (SEM). MgAl-GLYP-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filled with MgAl-GLYP-LDH showed a higher mid- to far-infrared absorption than films filled with MgAl-CO3-LDH in the 7−25 μm range, particularly in the key 9−11 μm range required for application in agricultural plastic films. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9016978 Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Fundamentals of wet oxidation of bayer - process liquor : reactivity of malonates Type de document : texte imprimé Auteurs : Jackie Dong, Auteur ; Greg Power, Auteur ; Joanne Loh, Auteur Année de publication : 2010 Article en page(s) : pp. 5347–5352 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Oxidation Résumé : The application of wet oxidation to the removal of organic impurities from Bayer-process liquors has the potential to deliver major benefits to the alumina industry. Previous work has identified the malonate anion as especially reactive under WO conditions, a property ascribed to its ability to form a carbanion in alkaline conditions. Understanding of the reaction mechanism involved in this effect is of importance to the development of improved WO technology. The current work confirms carbanion formation as the first step in the reaction. Deuterium exchange experiments and 13C NMR spectroscopy are used to demonstrate the weak acidity of the α-hydrogen atoms which leads to carbanion formation. The acidity of the α-hydrogen atoms in malonate is induced by the electron-withdrawing effect of the two adjacent carboxylate groups. Substituting an electron-donating group such as methyl or ethyl at the α-position reduces this effect, resulting in reduced oxidation rates for the substituted malonates. The role of the carbanion in the reaction mechanism is confirmed by analysis of the products and reaction kinetics. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100128k
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5347–5352[article] Fundamentals of wet oxidation of bayer - process liquor : reactivity of malonates [texte imprimé] / Jackie Dong, Auteur ; Greg Power, Auteur ; Joanne Loh, Auteur . - 2010 . - pp. 5347–5352.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5347–5352
Mots-clés : Oxidation Résumé : The application of wet oxidation to the removal of organic impurities from Bayer-process liquors has the potential to deliver major benefits to the alumina industry. Previous work has identified the malonate anion as especially reactive under WO conditions, a property ascribed to its ability to form a carbanion in alkaline conditions. Understanding of the reaction mechanism involved in this effect is of importance to the development of improved WO technology. The current work confirms carbanion formation as the first step in the reaction. Deuterium exchange experiments and 13C NMR spectroscopy are used to demonstrate the weak acidity of the α-hydrogen atoms which leads to carbanion formation. The acidity of the α-hydrogen atoms in malonate is induced by the electron-withdrawing effect of the two adjacent carboxylate groups. Substituting an electron-donating group such as methyl or ethyl at the α-position reduces this effect, resulting in reduced oxidation rates for the substituted malonates. The role of the carbanion in the reaction mechanism is confirmed by analysis of the products and reaction kinetics. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100128k Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Comparative modeling study on the performance of solid foam as a structured catalyst support in multiphase reactors Type de document : texte imprimé Auteurs : Patrick W. A. M. Wenmakers, Auteur ; John Van Der Schaaf, Auteur ; Ben F. M. Kuster, Auteur Année de publication : 2010 Article en page(s) : pp. 5353–5366 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Catalyst Multiphase Reactors Résumé : In this paper, the performance of two types of advanced foam packings (viz., Hairy Foam and washcoated Solid Foam) is compared with that of a packed bed of porous spherical particles. The comparison is done for two different types of reactions (viz., the slow hydrogenation of cinnamaldehyde and the fast hydrogenation of 3-methyl-1-pentyn-3-ol) and under two flow conditions (viz., upflow and downflow), in terms of selectivity, conversion, pressure drop, and reactor height. Under similar operating conditions, the simulation results show that, for both reactions, the Hairy Foam and Solid Foam packings reach higher selectivities and conversions than the packed bed of particles. However, in the case of the slow reaction, the pressure drop for the Hairy and Solid Foam packings is significantly larger than that for the bed of particles. This is due to the lower solids holdup, and thus lower catalyst concentration, of the Hairy Foam and Solid Foam packings. Therefore, larger reactors are required for the hairy foam and solid foam packings, resulting in a higher total pressure drop. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100128k
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5353–5366[article] Comparative modeling study on the performance of solid foam as a structured catalyst support in multiphase reactors [texte imprimé] / Patrick W. A. M. Wenmakers, Auteur ; John Van Der Schaaf, Auteur ; Ben F. M. Kuster, Auteur . - 2010 . - pp. 5353–5366.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5353–5366
Mots-clés : Catalyst Multiphase Reactors Résumé : In this paper, the performance of two types of advanced foam packings (viz., Hairy Foam and washcoated Solid Foam) is compared with that of a packed bed of porous spherical particles. The comparison is done for two different types of reactions (viz., the slow hydrogenation of cinnamaldehyde and the fast hydrogenation of 3-methyl-1-pentyn-3-ol) and under two flow conditions (viz., upflow and downflow), in terms of selectivity, conversion, pressure drop, and reactor height. Under similar operating conditions, the simulation results show that, for both reactions, the Hairy Foam and Solid Foam packings reach higher selectivities and conversions than the packed bed of particles. However, in the case of the slow reaction, the pressure drop for the Hairy and Solid Foam packings is significantly larger than that for the bed of particles. This is due to the lower solids holdup, and thus lower catalyst concentration, of the Hairy Foam and Solid Foam packings. Therefore, larger reactors are required for the hairy foam and solid foam packings, resulting in a higher total pressure drop. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100128k Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : CFD modeling of metronidazole degradation in water by the UV / H2O2 process in single and multilamp photoreactors Type de document : texte imprimé Auteurs : Mehrab Mehrvar, Auteur ; Farhad Ein-Mozaffari, Auteur Année de publication : 2010 Article en page(s) : pp. 5367–5382 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Metronidazole Photoreactors Résumé : A dynamic model for the degradation of aqueous metronidazole by hydrogen peroxide and ultraviolet irradiation processes (UV/H2O2) as an advanced oxidation technology (AOT) in a single lamp tubular photoreactor as well as in a multilamp tubular photoreactor is developed. The model contains the main chemical and photochemical reactions in a medium flowing in the turbulent regime. The optimal hydrogen peroxide concentrations of 75, 150, and 200 mg L−1 were predicted for different alkalinity concentrations of 0, 1.5, and 3 μM, respectively. The model is validated with distilled water as well as alkaline water at different alkalinity concentrations. The model is validated by using the experimental data reported in the open literature. The velocity field and concentration profiles for the turbulent flow using the k−ε model are determined by computational fluid dynamics (CFD). ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900906e
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5367–5382[article] CFD modeling of metronidazole degradation in water by the UV / H2O2 process in single and multilamp photoreactors [texte imprimé] / Mehrab Mehrvar, Auteur ; Farhad Ein-Mozaffari, Auteur . - 2010 . - pp. 5367–5382.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5367–5382
Mots-clés : Metronidazole Photoreactors Résumé : A dynamic model for the degradation of aqueous metronidazole by hydrogen peroxide and ultraviolet irradiation processes (UV/H2O2) as an advanced oxidation technology (AOT) in a single lamp tubular photoreactor as well as in a multilamp tubular photoreactor is developed. The model contains the main chemical and photochemical reactions in a medium flowing in the turbulent regime. The optimal hydrogen peroxide concentrations of 75, 150, and 200 mg L−1 were predicted for different alkalinity concentrations of 0, 1.5, and 3 μM, respectively. The model is validated with distilled water as well as alkaline water at different alkalinity concentrations. The model is validated by using the experimental data reported in the open literature. The velocity field and concentration profiles for the turbulent flow using the k−ε model are determined by computational fluid dynamics (CFD). ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900906e Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Development of iron oxide carriers for chemical looping combustion using sol − gel Type de document : texte imprimé Auteurs : A. M. Kierzkowska, Auteur ; C. D. Bohn, Auteur ; S. A. Scott, Auteur Année de publication : 2010 Article en page(s) : pp. 5383–5391 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Iron Oxide Résumé : Composite particles with different mass ratios of Fe2O3 and Al2O3 were prepared using a sol−gel method and were examined for use in chemical looping combustion through repeated reduction and oxidation cycles in a packed bed reactor at 850 °C. Unlike traditional chemical looping combustion which reduces an oxygen carrier in methane and oxidizes it in air, the reducing gas here was a mixture of CO and N2. Oxidation was performed in a mixture of steam and N2 to produce H2, followed by oxidation in air in some cases. The results were as follows: (1) For reduction to the FeO phase, unsupported Fe2O3 gave stable conversions over 40 cycles and no Al2O3 support was needed. (2) For reduction to the Fe phase over 10 cycles, 10 wt % Al2O3 was sufficient to give stable conversions above 0.9. Over 30−40 cycles, however, the conversion for particles with 10−20 wt % Al2O3 dropped below 0.35. (3) For reduction to the Fe phase over 40 cycles, 40 wt % Al2O3 was required and gave stable conversions near 0.75. The formation of FeO·Al2O3 was confirmed using X-ray diffraction. Steam in N2, followed by air, is the recommended sequence for oxidizing the composite carriers, since temperature excursions and agglomeration of particles could be avoided and higher conversions could be achieved. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100046f
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5383–5391[article] Development of iron oxide carriers for chemical looping combustion using sol − gel [texte imprimé] / A. M. Kierzkowska, Auteur ; C. D. Bohn, Auteur ; S. A. Scott, Auteur . - 2010 . - pp. 5383–5391.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5383–5391
Mots-clés : Iron Oxide Résumé : Composite particles with different mass ratios of Fe2O3 and Al2O3 were prepared using a sol−gel method and were examined for use in chemical looping combustion through repeated reduction and oxidation cycles in a packed bed reactor at 850 °C. Unlike traditional chemical looping combustion which reduces an oxygen carrier in methane and oxidizes it in air, the reducing gas here was a mixture of CO and N2. Oxidation was performed in a mixture of steam and N2 to produce H2, followed by oxidation in air in some cases. The results were as follows: (1) For reduction to the FeO phase, unsupported Fe2O3 gave stable conversions over 40 cycles and no Al2O3 support was needed. (2) For reduction to the Fe phase over 10 cycles, 10 wt % Al2O3 was sufficient to give stable conversions above 0.9. Over 30−40 cycles, however, the conversion for particles with 10−20 wt % Al2O3 dropped below 0.35. (3) For reduction to the Fe phase over 40 cycles, 40 wt % Al2O3 was required and gave stable conversions near 0.75. The formation of FeO·Al2O3 was confirmed using X-ray diffraction. Steam in N2, followed by air, is the recommended sequence for oxidizing the composite carriers, since temperature excursions and agglomeration of particles could be avoided and higher conversions could be achieved. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100046f Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Selective oxidation of cyclohexane over transition - metal - incorporated HMS in a solvent - free system Type de document : texte imprimé Auteurs : Jun Li, Auteur ; Yong Shi, Auteur ; Xu, Li, Auteur Année de publication : 2010 Article en page(s) : pp. 5392–5399 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Cyclohexane Oxidation Résumé : Mesostructure materials A-HMS (A = Ce, Ti, Co, Al, Cr, V, Zr) were synthesized with cetylamine as the structure director and tetraethyl orthosilicalite as the silica source. CeO2/V-HMS and CeO2/Al-HMS were prepared by dipping-calcination method. The materials were characterized by X-ray diffraction (XRD), UV−vis, Fourier transform infrared (FT-IR), N2 adsorption−desorption, inductively coupled plasma−atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM), and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). The incorporated ions were mostly in the framework of the mesoporous materials, which were confirmed by the XRD, FT-IR, UV−vis, and 27Al MAS NMR analyses. The solids obtained were employed as heterogeneous catalysts for the selective oxidation of cyclohexane with oxygen (O2) as oxidant in a solvent-free system. The material CeO2/V-HMS exhibited the highest activity with about 18% conversion of cyclohexane but 68% total selectivity to cyclohexanol and cyclohexanone. The performance of Al(40)-HMS is satisfying for nearly 10% conversion of cyclohexane and 93% total selectivity to the desired products. Also, Al(40)-HMS is efficient for its excellent recyclable property in the oxidation of cyclohexane. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100092x
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5392–5399[article] Selective oxidation of cyclohexane over transition - metal - incorporated HMS in a solvent - free system [texte imprimé] / Jun Li, Auteur ; Yong Shi, Auteur ; Xu, Li, Auteur . - 2010 . - pp. 5392–5399.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5392–5399
Mots-clés : Cyclohexane Oxidation Résumé : Mesostructure materials A-HMS (A = Ce, Ti, Co, Al, Cr, V, Zr) were synthesized with cetylamine as the structure director and tetraethyl orthosilicalite as the silica source. CeO2/V-HMS and CeO2/Al-HMS were prepared by dipping-calcination method. The materials were characterized by X-ray diffraction (XRD), UV−vis, Fourier transform infrared (FT-IR), N2 adsorption−desorption, inductively coupled plasma−atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM), and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). The incorporated ions were mostly in the framework of the mesoporous materials, which were confirmed by the XRD, FT-IR, UV−vis, and 27Al MAS NMR analyses. The solids obtained were employed as heterogeneous catalysts for the selective oxidation of cyclohexane with oxygen (O2) as oxidant in a solvent-free system. The material CeO2/V-HMS exhibited the highest activity with about 18% conversion of cyclohexane but 68% total selectivity to cyclohexanol and cyclohexanone. The performance of Al(40)-HMS is satisfying for nearly 10% conversion of cyclohexane and 93% total selectivity to the desired products. Also, Al(40)-HMS is efficient for its excellent recyclable property in the oxidation of cyclohexane. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100092x Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Rheological behavior of pyrophyllite − water slurry in the presence of anionic, cationic, and nonionic surfactants Type de document : texte imprimé Auteurs : Himanshu Desai, Auteur ; Nihar Ranjan Biswal, Auteur ; Santanu Paria, Auteur Année de publication : 2010 Article en page(s) : pp. 5400–5406 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : surfactants Anionic Cationic Résumé : The rheological behavior of pyrophyllite−water clay slurry has been studied in the presence of three different types of surfactants: anionic, cationic, and nonionic. The slurry is non-Newtonian and thixotropic in nature, and the hysteresis area increases with increasing clay concentration. In the presence of acidic pH, surface potential is low and viscosity is high; the opposite is true for alkaline pH. The rheological behavior is different in the presence of three surfactants. The viscosity highly depends on the types of surfactant adsorbed on the clay surface and surface potential after the adsorption. The d(001) lattice spacing of the pyrophyllite clay does not change after the adsorption of surfactants, indicating that the surfactants are not adsorbing inside the clay spacing. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901643s
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5400–5406[article] Rheological behavior of pyrophyllite − water slurry in the presence of anionic, cationic, and nonionic surfactants [texte imprimé] / Himanshu Desai, Auteur ; Nihar Ranjan Biswal, Auteur ; Santanu Paria, Auteur . - 2010 . - pp. 5400–5406.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5400–5406
Mots-clés : surfactants Anionic Cationic Résumé : The rheological behavior of pyrophyllite−water clay slurry has been studied in the presence of three different types of surfactants: anionic, cationic, and nonionic. The slurry is non-Newtonian and thixotropic in nature, and the hysteresis area increases with increasing clay concentration. In the presence of acidic pH, surface potential is low and viscosity is high; the opposite is true for alkaline pH. The rheological behavior is different in the presence of three surfactants. The viscosity highly depends on the types of surfactant adsorbed on the clay surface and surface potential after the adsorption. The d(001) lattice spacing of the pyrophyllite clay does not change after the adsorption of surfactants, indicating that the surfactants are not adsorbing inside the clay spacing. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901643s Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Effect of midsynthesis addition of silica to the synthesis medium on the properties of MFI - type zeolite membranes Type de document : texte imprimé Auteurs : Belma Soydas, Auteur ; Halil Kalipcilar, Auteur ; Ali Culfaz, Auteur Année de publication : 2010 Article en page(s) : pp. 5407–5414 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Zeolite Membranes Résumé : Thin zeolite membranes of MFI type were prepared on α-Al2O3 supports by midsynthesis addition of silica in a recirculating flow system at 95 °C. The synthesis was started with the batch composition of 80SiO2:30TPAOH:1500H2O which was changed to 80SiO2:9TPAOH:1500H2O by addition of silica after 24, 48, or 72 h. Compared to synthesis at constant composition, it is possible to affect the rates of nucleation and crystal growth to obtain membranes with better quality by changing the overall composition of the medium during the membrane synthesis. The membranes produced with and without midsynthesis addition of silica have n-C4H10/i-C4H10 ideal selectivities of 47 and 8 at 100 °C, respectively. Among these membranes, the ones formed with midsynthesis addition of silica at 24 h yielded the highest n-C4H10/CH4 separation selectivities, which were over 20 at 25 °C. The time at which the silica is introduced to the synthesis medium is critical for the membrane quality. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902024h
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5407–5414[article] Effect of midsynthesis addition of silica to the synthesis medium on the properties of MFI - type zeolite membranes [texte imprimé] / Belma Soydas, Auteur ; Halil Kalipcilar, Auteur ; Ali Culfaz, Auteur . - 2010 . - pp. 5407–5414.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5407–5414
Mots-clés : Zeolite Membranes Résumé : Thin zeolite membranes of MFI type were prepared on α-Al2O3 supports by midsynthesis addition of silica in a recirculating flow system at 95 °C. The synthesis was started with the batch composition of 80SiO2:30TPAOH:1500H2O which was changed to 80SiO2:9TPAOH:1500H2O by addition of silica after 24, 48, or 72 h. Compared to synthesis at constant composition, it is possible to affect the rates of nucleation and crystal growth to obtain membranes with better quality by changing the overall composition of the medium during the membrane synthesis. The membranes produced with and without midsynthesis addition of silica have n-C4H10/i-C4H10 ideal selectivities of 47 and 8 at 100 °C, respectively. Among these membranes, the ones formed with midsynthesis addition of silica at 24 h yielded the highest n-C4H10/CH4 separation selectivities, which were over 20 at 25 °C. The time at which the silica is introduced to the synthesis medium is critical for the membrane quality. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902024h Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Maximum Sensitivity Based Robust Tuning for Two-Degree-of-Freedom Proportional−Integral Controllers Type de document : texte imprimé Auteurs : V. M. Alfaro, Auteur ; R. Vilanova, Auteur ; O. Arrieta, Auteur Année de publication : 2010 Article en page(s) : pp. 5415–5423 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Robust Tuning Integral Controllers Résumé : A tuning method for two-degree-of-freedom (2-DoF) proportional−integral (PI) controllers for first-order-plus-dead-time (FOPDT) models is presented. It allows the designer to deal with the closed-loop control system performance−robustness trade-off specifying the lowest robustness level allowed by selecting a maximum sensitivity in the 1.4−2.0 range. In addition, a smooth performance is obtained by forcing the regulatory and servo-control closed-loop transfer functions to perform as close as possible to a target nonoscillatory dynamics. Controller tuning rules are provided for FOPDT models with normalized dead-times from 0.1 to 2.0. Comparative examples show the effectiveness of the proposed tuning method. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901617y
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5415–5423[article] Maximum Sensitivity Based Robust Tuning for Two-Degree-of-Freedom Proportional−Integral Controllers [texte imprimé] / V. M. Alfaro, Auteur ; R. Vilanova, Auteur ; O. Arrieta, Auteur . - 2010 . - pp. 5415–5423.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5415–5423
Mots-clés : Robust Tuning Integral Controllers Résumé : A tuning method for two-degree-of-freedom (2-DoF) proportional−integral (PI) controllers for first-order-plus-dead-time (FOPDT) models is presented. It allows the designer to deal with the closed-loop control system performance−robustness trade-off specifying the lowest robustness level allowed by selecting a maximum sensitivity in the 1.4−2.0 range. In addition, a smooth performance is obtained by forcing the regulatory and servo-control closed-loop transfer functions to perform as close as possible to a target nonoscillatory dynamics. Controller tuning rules are provided for FOPDT models with normalized dead-times from 0.1 to 2.0. Comparative examples show the effectiveness of the proposed tuning method. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901617y Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Global optimization of large - scale eneralized pooling problems : quadratically constrained MINLP models Type de document : texte imprimé Auteurs : Ruth Misener, Auteur ; Christodoulos A. Floudas, Auteur Année de publication : 2010 Article en page(s) : pp. 5424–5438 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Quadratically constrained MINLP Résumé : The generalized pooling problem is a generic way of identifying a topology containing sources nodes, intermediate storage tanks, and sinks when monitoring specific stream qualities is imperative. One important application domain of the generalized pooling problem is wastewater treatment. Choosing among the wide array of available wastewater treatment technologies is a combinatorially complex optimization problem that requires nonconvex terms to monitor regulated stream qualities about a treatment plant. In this work, we address five instantiations of the generalized pooling problem to global optimality by introducing (i) a quadratically constrained MINLP model formulation that reduces the number of bilinear terms, (ii) novel piecewise underestimation methods for the nonconvex bilinear terms to tighten the relaxation [Gounaris et al. Ind. Eng. Chem. Res. 2009, 48, 5742−5766; Wicaksono and Karimi AIChE J. 2008, 54, 991−1008], and (iii) a branch-and-bound algorithm suited to address the combinatorial complexity of the problem. Extensive computational results are presented for small, medium, large, and two very large-scale case studies which feature 48, 300, 675, and 1260 distinct bilinear terms, respectively. We show that the small, medium, and large case studies can be solved to global optimality efficiently. The two very large case studies can be solved within 0.9% and 2.3% of the global optimum, and when the additional assumption of a limited number of plants is introduced, they can be solved to global optimality. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100025e
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5424–5438[article] Global optimization of large - scale eneralized pooling problems : quadratically constrained MINLP models [texte imprimé] / Ruth Misener, Auteur ; Christodoulos A. Floudas, Auteur . - 2010 . - pp. 5424–5438.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5424–5438
Mots-clés : Quadratically constrained MINLP Résumé : The generalized pooling problem is a generic way of identifying a topology containing sources nodes, intermediate storage tanks, and sinks when monitoring specific stream qualities is imperative. One important application domain of the generalized pooling problem is wastewater treatment. Choosing among the wide array of available wastewater treatment technologies is a combinatorially complex optimization problem that requires nonconvex terms to monitor regulated stream qualities about a treatment plant. In this work, we address five instantiations of the generalized pooling problem to global optimality by introducing (i) a quadratically constrained MINLP model formulation that reduces the number of bilinear terms, (ii) novel piecewise underestimation methods for the nonconvex bilinear terms to tighten the relaxation [Gounaris et al. Ind. Eng. Chem. Res. 2009, 48, 5742−5766; Wicaksono and Karimi AIChE J. 2008, 54, 991−1008], and (iii) a branch-and-bound algorithm suited to address the combinatorial complexity of the problem. Extensive computational results are presented for small, medium, large, and two very large-scale case studies which feature 48, 300, 675, and 1260 distinct bilinear terms, respectively. We show that the small, medium, and large case studies can be solved to global optimality efficiently. The two very large case studies can be solved within 0.9% and 2.3% of the global optimum, and when the additional assumption of a limited number of plants is introduced, they can be solved to global optimality. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100025e Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Energy requirements of distillation : exergy, pinch points, and the reversible column Type de document : texte imprimé Auteurs : Etienne Ayotte-Sauvé, Auteur ; Mikhail Sorin, Auteur Année de publication : 2010 Article en page(s) : pp. 5439–5449 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Distillation Pinch Points Résumé : This paper considers the problem of finding minimum energy requirements of a single-feed adiabatic distillation column for a given separation task. Over the years, many attempts to understand this problem have been made. This paper presents an approach which is at the intersection of the thermodynamic and geometric points of view. In it, an analysis of multicomponent distillation is carried out via the notion of power of separation, which is akin to compositional exergy. It is shown mathematically that this concept, although taking its roots in thermodynamics, has a strong link with the geometry of liquid composition trajectories in multicomponent distillation and is also related to the traditional McCabe−Thiele diagram for binary distillation. By considering pinch-point curves for adiabatic column sections and their link with reversible column profiles, a characterization of minimal energy requirements of the single-feed adiabatic distillation process is proposed. As a consequence, a shortcut method to determine minimal energy requirements of multicomponent distillation is introduced. Examples validating this approach for multicomponent distillation of ideal, nonideal, zeotropic, and azeotropic mixtures with up to six components are presented. These examples indicate that the new method can, in principle, treat any number of mixture components. All types of pinch behavior are covered, that is, the method can find minimal energy designs associated to feed, saddle, or tangent pinch points. Case studies where pinched minimum energy solutions exist, where pinched solutions can be reduced to nonpinched solutions, and where no pinched solutions exist are presented. In all these cases, the new method can find, if they exist, pinched and nonpinched solutions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100369f
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5439–5449[article] Energy requirements of distillation : exergy, pinch points, and the reversible column [texte imprimé] / Etienne Ayotte-Sauvé, Auteur ; Mikhail Sorin, Auteur . - 2010 . - pp. 5439–5449.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5439–5449
Mots-clés : Distillation Pinch Points Résumé : This paper considers the problem of finding minimum energy requirements of a single-feed adiabatic distillation column for a given separation task. Over the years, many attempts to understand this problem have been made. This paper presents an approach which is at the intersection of the thermodynamic and geometric points of view. In it, an analysis of multicomponent distillation is carried out via the notion of power of separation, which is akin to compositional exergy. It is shown mathematically that this concept, although taking its roots in thermodynamics, has a strong link with the geometry of liquid composition trajectories in multicomponent distillation and is also related to the traditional McCabe−Thiele diagram for binary distillation. By considering pinch-point curves for adiabatic column sections and their link with reversible column profiles, a characterization of minimal energy requirements of the single-feed adiabatic distillation process is proposed. As a consequence, a shortcut method to determine minimal energy requirements of multicomponent distillation is introduced. Examples validating this approach for multicomponent distillation of ideal, nonideal, zeotropic, and azeotropic mixtures with up to six components are presented. These examples indicate that the new method can, in principle, treat any number of mixture components. All types of pinch behavior are covered, that is, the method can find minimal energy designs associated to feed, saddle, or tangent pinch points. Case studies where pinched minimum energy solutions exist, where pinched solutions can be reduced to nonpinched solutions, and where no pinched solutions exist are presented. In all these cases, the new method can find, if they exist, pinched and nonpinched solutions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100369f Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Numerical study of gas − solid flow in a radial - inlet structure cyclone separator Type de document : texte imprimé Auteurs : Jie Cui, Auteur ; Xueli Chen, Auteur ; Xin Gong, Auteur Année de publication : 2010 Article en page(s) : pp. 5450–5460 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Gas solid flow Résumé : The development of a radial-inlet structure cyclone separator is reported in this paper, which is used as a primary device for gas-particle separation in an opposed multi-burner (OMB) gasification system. The radial-inlet cyclone is more suitable for a high-pressure industrial operation environment on the premise of higher efficiency. A model based on computational fluid dynamics (CFD) techniques was applied to study the performance of a new-type cyclone separator. In the approach, the turbulent flow was described by the Reynolds stress model, and the particle flow was described by the stochastic Lagrangian model. The validity of the proposed approach is verified by the good agreement between the measured and the predicted results. The results indicate that, though the velocity flow field is not geometry symmetrical and a three-dimensional unsteady state, it is quasi-periodic. Additionally, there exists a processing vortex core phenomenon in the cyclone. The particle concentration distribution is nonuniform because of the centrifugal force. The distribution area can be divided into three parts according to the particles’ motion feature. And the larger particles are easier to separate than the smaller ones. But particles with a size exceeding a critical value will not be collected at the bottom and stagnate on the conical wall of the cyclone. This will lead to serious erosion on the conical part in the cyclone. In addition, the separation efficiency increases with the particle size, and the cut-point diameter of the radial-inlet cyclone is smaller than the traditional cyclone under the same inlet conditions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901962r
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5450–5460[article] Numerical study of gas − solid flow in a radial - inlet structure cyclone separator [texte imprimé] / Jie Cui, Auteur ; Xueli Chen, Auteur ; Xin Gong, Auteur . - 2010 . - pp. 5450–5460.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5450–5460
Mots-clés : Gas solid flow Résumé : The development of a radial-inlet structure cyclone separator is reported in this paper, which is used as a primary device for gas-particle separation in an opposed multi-burner (OMB) gasification system. The radial-inlet cyclone is more suitable for a high-pressure industrial operation environment on the premise of higher efficiency. A model based on computational fluid dynamics (CFD) techniques was applied to study the performance of a new-type cyclone separator. In the approach, the turbulent flow was described by the Reynolds stress model, and the particle flow was described by the stochastic Lagrangian model. The validity of the proposed approach is verified by the good agreement between the measured and the predicted results. The results indicate that, though the velocity flow field is not geometry symmetrical and a three-dimensional unsteady state, it is quasi-periodic. Additionally, there exists a processing vortex core phenomenon in the cyclone. The particle concentration distribution is nonuniform because of the centrifugal force. The distribution area can be divided into three parts according to the particles’ motion feature. And the larger particles are easier to separate than the smaller ones. But particles with a size exceeding a critical value will not be collected at the bottom and stagnate on the conical wall of the cyclone. This will lead to serious erosion on the conical part in the cyclone. In addition, the separation efficiency increases with the particle size, and the cut-point diameter of the radial-inlet cyclone is smaller than the traditional cyclone under the same inlet conditions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901962r Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Supercritical fluid extraction and micronization of ginkgo flavonoids from ginkgo biloba leaves Type de document : texte imprimé Auteurs : Shi-Feng Miao, Auteur ; Jin-Peng Yu, Auteur ; Zhe Du, Auteur Année de publication : 2010 Article en page(s) : pp. 5461–5466 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Micronization Ginkgo flavonoids Résumé : Ginkgo flavonoids were extracted from Ginkgo biloba leaves using supercritical carbon dioxide extraction technology (SFE) with ethanol as the entrainer. The effects of important process parameters on SFE were examined, and the crude extracts were further refined. At optimized experimental conditions, i.e., 20 MPa of extraction pressure, a 40 °C extraction temperature, a 10 g/min CO2 flow rate, and a 6 mL/min ethanol flow rate, the extraction yield could reach 0.36%. Supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA-HCM) was used to obtain microparticles of Ginkgo flavonoids. The influences of the solute concentration as well as the mass flow ratio of the CO2/liquid solution on particle size (PS) and particle size distribution (PSD) were investigated. Well-defined, spherical, and separated particles with a controlled particle size ranging between 0.2 and 3.0 μm were successfully obtained in this work. The micronization of Ginkgo flavonoids can improve the drug absorption in the body and has great potential for use in drug delivery systems. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902001x
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5461–5466[article] Supercritical fluid extraction and micronization of ginkgo flavonoids from ginkgo biloba leaves [texte imprimé] / Shi-Feng Miao, Auteur ; Jin-Peng Yu, Auteur ; Zhe Du, Auteur . - 2010 . - pp. 5461–5466.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5461–5466
Mots-clés : Micronization Ginkgo flavonoids Résumé : Ginkgo flavonoids were extracted from Ginkgo biloba leaves using supercritical carbon dioxide extraction technology (SFE) with ethanol as the entrainer. The effects of important process parameters on SFE were examined, and the crude extracts were further refined. At optimized experimental conditions, i.e., 20 MPa of extraction pressure, a 40 °C extraction temperature, a 10 g/min CO2 flow rate, and a 6 mL/min ethanol flow rate, the extraction yield could reach 0.36%. Supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA-HCM) was used to obtain microparticles of Ginkgo flavonoids. The influences of the solute concentration as well as the mass flow ratio of the CO2/liquid solution on particle size (PS) and particle size distribution (PSD) were investigated. Well-defined, spherical, and separated particles with a controlled particle size ranging between 0.2 and 3.0 μm were successfully obtained in this work. The micronization of Ginkgo flavonoids can improve the drug absorption in the body and has great potential for use in drug delivery systems. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902001x Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Effect of blade speed on granular flow and mixing in a cylindrical mixer Type de document : texte imprimé Auteurs : G. R. Chandratilleke, Auteur ; Y. C. Zhou, Auteur ; A. B. Yu, Auteur Année de publication : 2010 Article en page(s) : pp.5467–5478 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Granular Flow Résumé : The discrete element method (DEM) offers the possibility of understanding mixing processes at a microscopic, particle level. In connection with previous studies, DEM is used in this work to investigate the mixing of monosized spherical particles with blade speeds in the range 2−100 rpm. Recirculating flows are observed in both horizontal and cylindrical sections of the bed, providing a mixing mechanism. The recirculating flows formed in front of the blade in cylindrical sections seem to disappear, bringing a reduction of mixing rate at high blade speeds. Viewed at the particle scale, a zone of large interparticle forces is present in front of the blade, and this zone moves toward the vessel walls at high speeds. These are the regions where particle breakage or fracture can happen. Interparticle forces in the bed as a whole increase with the blade speed. Moreover, particle mixing has been studied at both macroscopic and particle scales using conventional mixing index and coordination or contact numbers. One conventional mixing index shows a slight reduction in mixing rate in the transition mixing region up to a certain blade speed and a slight improvement thereafter. This improvement is probably caused by the toroidal motion of particles induced at high blade speeds. Coordination number is successful in capturing the mixing process, and indicates a new way of studying particle-scale mixing. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901581t
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp.5467–5478[article] Effect of blade speed on granular flow and mixing in a cylindrical mixer [texte imprimé] / G. R. Chandratilleke, Auteur ; Y. C. Zhou, Auteur ; A. B. Yu, Auteur . - 2010 . - pp.5467–5478.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp.5467–5478
Mots-clés : Granular Flow Résumé : The discrete element method (DEM) offers the possibility of understanding mixing processes at a microscopic, particle level. In connection with previous studies, DEM is used in this work to investigate the mixing of monosized spherical particles with blade speeds in the range 2−100 rpm. Recirculating flows are observed in both horizontal and cylindrical sections of the bed, providing a mixing mechanism. The recirculating flows formed in front of the blade in cylindrical sections seem to disappear, bringing a reduction of mixing rate at high blade speeds. Viewed at the particle scale, a zone of large interparticle forces is present in front of the blade, and this zone moves toward the vessel walls at high speeds. These are the regions where particle breakage or fracture can happen. Interparticle forces in the bed as a whole increase with the blade speed. Moreover, particle mixing has been studied at both macroscopic and particle scales using conventional mixing index and coordination or contact numbers. One conventional mixing index shows a slight reduction in mixing rate in the transition mixing region up to a certain blade speed and a slight improvement thereafter. This improvement is probably caused by the toroidal motion of particles induced at high blade speeds. Coordination number is successful in capturing the mixing process, and indicates a new way of studying particle-scale mixing. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901581t Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Predicting thermophysical properties of mono - and diglycerides with the chemical constituent fragment approach Type de document : texte imprimé Auteurs : Li Zong, Auteur ; Ramanathan, Sundaram, Auteur ; Chau-Chyun Chen, Auteur Année de publication : 2010 Article en page(s) : pp. 5479–5484 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Thermophysical properties Résumé : A novel chemical constituent fragment approach is used to estimate thermophysical properties for mono- and diglycerides from fragment composition and fragment-specific parameters. The monoglycerol and diglycerol fragment parameters are obtained from regressing against very limited available experimental data for mono- and diglycerides in the literature while fatty acid fragment parameters are obtained from an earlier investigation for estimating thermophysical properties of triglycerides [Zong et al. Ind. Eng. Chem. Res. 2010, 49, 876−886; Zong et al. Ind. Eng. Chem. Res. 2010, 49, 3022−3023]. Built on this methodology, we develop mono- and diglyceride thermophysical property parameters for vapor pressure, enthalpy and Gibbs free energy of vaporization, liquid heat capacity, heat of fusion, enthalpy of formation, and liquid molar volume. Combined with the results of the earlier investigation on triglycerides [Zong et al. Ind. Eng. Chem. Res. 2010, 49, 876−886; Zong et al. Ind. Eng. Chem. Res. 2010, 49, 3022−3023], the derived parameters and the corresponding databank enable reliable and efficient thermophysical property calculations in support of process modeling, simulation, design, and optimization of biodiesel production processes. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901948v
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5479–5484[article] Predicting thermophysical properties of mono - and diglycerides with the chemical constituent fragment approach [texte imprimé] / Li Zong, Auteur ; Ramanathan, Sundaram, Auteur ; Chau-Chyun Chen, Auteur . - 2010 . - pp. 5479–5484.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5479–5484
Mots-clés : Thermophysical properties Résumé : A novel chemical constituent fragment approach is used to estimate thermophysical properties for mono- and diglycerides from fragment composition and fragment-specific parameters. The monoglycerol and diglycerol fragment parameters are obtained from regressing against very limited available experimental data for mono- and diglycerides in the literature while fatty acid fragment parameters are obtained from an earlier investigation for estimating thermophysical properties of triglycerides [Zong et al. Ind. Eng. Chem. Res. 2010, 49, 876−886; Zong et al. Ind. Eng. Chem. Res. 2010, 49, 3022−3023]. Built on this methodology, we develop mono- and diglyceride thermophysical property parameters for vapor pressure, enthalpy and Gibbs free energy of vaporization, liquid heat capacity, heat of fusion, enthalpy of formation, and liquid molar volume. Combined with the results of the earlier investigation on triglycerides [Zong et al. Ind. Eng. Chem. Res. 2010, 49, 876−886; Zong et al. Ind. Eng. Chem. Res. 2010, 49, 3022−3023], the derived parameters and the corresponding databank enable reliable and efficient thermophysical property calculations in support of process modeling, simulation, design, and optimization of biodiesel production processes. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901948v Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
Titre : Novel Ethanol Synthesis Method via C1 Chemicals without Any Agriculture Feedstocks Type de document : texte imprimé Auteurs : Yi Zhang, Auteur ; Xiaoguang San, Auteur ; Noritatsu Tsubaki, Auteur Année de publication : 2010 Article en page(s) : pp. 5485–5488 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Ethanol Synthesis Résumé : A new method of ethanol synthesis from dimethyl ether (DME) and syngas was developed, which is via combined carbonylation of dimethyl ether and hydrogenation of methyl acetate. The conversion of DME is up to 100% and the selectivity of ethanol is as high as 48.5%. On the other hand, methanol as another main product of this study is formed as 47.6%, which can be recycled as a reactant of DME synthesis (MTD), leading to lower the cost of this new ethanol synthesis method. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901882s
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5485–5488[article] Novel Ethanol Synthesis Method via C1 Chemicals without Any Agriculture Feedstocks [texte imprimé] / Yi Zhang, Auteur ; Xiaoguang San, Auteur ; Noritatsu Tsubaki, Auteur . - 2010 . - pp. 5485–5488.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5485–5488
Mots-clés : Ethanol Synthesis Résumé : A new method of ethanol synthesis from dimethyl ether (DME) and syngas was developed, which is via combined carbonylation of dimethyl ether and hydrogenation of methyl acetate. The conversion of DME is up to 100% and the selectivity of ethanol is as high as 48.5%. On the other hand, methanol as another main product of this study is formed as 47.6%, which can be recycled as a reactant of DME synthesis (MTD), leading to lower the cost of this new ethanol synthesis method. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901882s Exemplaires
Code-barres Cote Support Localisation Section Disponibilité aucun exemplaire
