Comparative study of cocurrent and countercurrent modes of operation for a thermal hydrolyzer in an industrial urea wastewater treatment loop / M. R. Rahimpour in Industrial & engineering chemistry research, Vol. 49 N° 19 (Octobre 2010)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 49 N° 19 (Octobre 2010) . - pp. 9289–9299 Titre : Comparative study of cocurrent and countercurrent modes of operation for a thermal hydrolyzer in an industrial urea wastewater treatment loop Type de document : texte imprimé Auteurs : M. R. Rahimpour, Auteur ; H. R. Mottaghi, Auteur Année de publication : 2010 Article en page(s) : pp. 9289–9299 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Waste water purification Countercurrent flow Cocurrent Comparative study Résumé : In this work, a comparison of cocurrent and countercurrent modes of operation for an industrial wastewater treatment loop of an industrial urea plant has been carried out. In both modes of operation, a loop with a thermal hydrolyzer is used for urea decomposition, and two desorbers are used for the removal of ammonia and carbon dioxide. In the proposed model, the extended electrolytic UNIQUAC equation is used to describe the nonideality of the liquid phase of the NH3-CO2-H2O-urea system, and the perturbed-hard-sphere (PHS) equation of state is applied to predict the vapor fugacity coefficients. Also, the urea hydrolysis reactors are divided into several continuously stirred tank reactors (CSTRs) and the equilibrium-stage model is applied for modeling of both kinds of reactors and of the desorbers. The simulation results show that countercurrent mode of operation is necessary to achieve new environmental standards and complete treatment. The data predicted using the model were consistent with available plant data, indicating the validity of the model. The impact of different parameters on the performance of the urea wastewater treatment loops has been examined. Overall, this study results in beneficial information about the use of the cocurrent and countercurrent hydrolysis reactors in the urea wastewater treatment process. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23289663 [article] Comparative study of cocurrent and countercurrent modes of operation for a thermal hydrolyzer in an industrial urea wastewater treatment loop [texte imprimé] / M. R. Rahimpour, Auteur ; H. R. Mottaghi, Auteur . - 2010 . - pp. 9289–9299. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 19 (Octobre 2010) . - pp. 9289–9299 Mots-clés : Waste water purification Countercurrent flow Cocurrent Comparative study Résumé : In this work, a comparison of cocurrent and countercurrent modes of operation for an industrial wastewater treatment loop of an industrial urea plant has been carried out. In both modes of operation, a loop with a thermal hydrolyzer is used for urea decomposition, and two desorbers are used for the removal of ammonia and carbon dioxide. In the proposed model, the extended electrolytic UNIQUAC equation is used to describe the nonideality of the liquid phase of the NH3-CO2-H2O-urea system, and the perturbed-hard-sphere (PHS) equation of state is applied to predict the vapor fugacity coefficients. Also, the urea hydrolysis reactors are divided into several continuously stirred tank reactors (CSTRs) and the equilibrium-stage model is applied for modeling of both kinds of reactors and of the desorbers. The simulation results show that countercurrent mode of operation is necessary to achieve new environmental standards and complete treatment. The data predicted using the model were consistent with available plant data, indicating the validity of the model. The impact of different parameters on the performance of the urea wastewater treatment loops has been examined. Overall, this study results in beneficial information about the use of the cocurrent and countercurrent hydrolysis reactors in the urea wastewater treatment process. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23289663

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Comparative study of two different hydrogen redistribution strategies along a fluidized-red hydrogen permselective membrane reactor for methanol synthesis / M. R. Rahimpour in Industrial & engineering chemistry research, Vol. 49 N° 2 (Janvier 2010)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 49 N° 2 (Janvier 2010) . - pp 472–480 Titre : Comparative study of two different hydrogen redistribution strategies along a fluidized-red hydrogen permselective membrane reactor for methanol synthesis Type de document : texte imprimé Auteurs : M. R. Rahimpour, Auteur ; Bayat, M., Auteur Année de publication : 2010 Article en page(s) : pp 472–480 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Hydrogen Permselective membrane reactor. Résumé : In this work, two different hydrogen redistribution strategies along a bubbling fluidized-bed hydrogen permselective membrane reactor have been compared. In the first strategy, fresh synthesis gas flows in the tube side of the fluidized-bed membrane reactor in cocurrent mode with reacting material in the shell side, so that more hydrogen is provided in the first segments of the reactor. In the second strategy, fresh synthesis gas flows in the tube side of the fluidized-bed membrane reactor in countercurrent mode with reacting material in the shell side, so that more hydrogen is provided in the last segments of the reactor. A dynamic two-phase theory in the bubbling regime of fluidization was developed to model and compare two strategies from different points of view. Comparison between cocurrent and countercurrent modes of operation shows that the reactor in the countercurrent configuration operates with higher conversion of methanol, longer catalyst life, and higher carbon dioxide removal, whereas the reactor in the cocurrent configuration operates with higher carbon monoxide removal, lower water production, and higher hydrogen permeation rate. Enhancement of the carbon dioxide removal in countercurrent mode and the carbon monoxide removal in cocurrent mode causes a lower environmental impact. The lower water production rate in cocurrent mode reduces catalyst recrystallization. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9005113 [article] Comparative study of two different hydrogen redistribution strategies along a fluidized-red hydrogen permselective membrane reactor for methanol synthesis [texte imprimé] / M. R. Rahimpour, Auteur ; Bayat, M., Auteur . - 2010 . - pp 472–480. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 2 (Janvier 2010) . - pp 472–480 Mots-clés : Hydrogen Permselective membrane reactor. Résumé : In this work, two different hydrogen redistribution strategies along a bubbling fluidized-bed hydrogen permselective membrane reactor have been compared. In the first strategy, fresh synthesis gas flows in the tube side of the fluidized-bed membrane reactor in cocurrent mode with reacting material in the shell side, so that more hydrogen is provided in the first segments of the reactor. In the second strategy, fresh synthesis gas flows in the tube side of the fluidized-bed membrane reactor in countercurrent mode with reacting material in the shell side, so that more hydrogen is provided in the last segments of the reactor. A dynamic two-phase theory in the bubbling regime of fluidization was developed to model and compare two strategies from different points of view. Comparison between cocurrent and countercurrent modes of operation shows that the reactor in the countercurrent configuration operates with higher conversion of methanol, longer catalyst life, and higher carbon dioxide removal, whereas the reactor in the cocurrent configuration operates with higher carbon monoxide removal, lower water production, and higher hydrogen permeation rate. Enhancement of the carbon dioxide removal in countercurrent mode and the carbon monoxide removal in cocurrent mode causes a lower environmental impact. The lower water production rate in cocurrent mode reduces catalyst recrystallization. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9005113

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Modeling and simulation of an industrial ethylene oxide (EO) reactor using artificial neural networks (ANN) / M. R. Rahimpour in Industrial & engineering chemistry research, Vol. 50 N° 10 (Mai 2011)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 50 N° 10 (Mai 2011) . - pp. 6044–6052 Titre : Modeling and simulation of an industrial ethylene oxide (EO) reactor using artificial neural networks (ANN) Type de document : texte imprimé Auteurs : M. R. Rahimpour, Auteur ; M. Shayanmehr, Auteur ; M. Nazari, Auteur Année de publication : 2011 Article en page(s) : pp. 6044–6052 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Ethylene oxide Artificial neural networks Résumé : In the present work, a one-dimensional heterogeneous model was used for dynamic simulation of an industrial fixed-bed catalytic ethylene oxide (EO) reactor in the presence of long-term catalyst deactivation. In order to determine the level of optimum ethylene dichloride (EDC), a multilayer perceptron (MLP) neural network was used. In addition, the effect of inlet gas velocity on EO mole fraction of gas and solid phases was investigated. The model validation was carried out by comparison of model results with corresponding industrial conditions and over a period of three operating years. A good agreement was found between the simulation results of the dynamic model and historical process data. The error of simulation was found to be less than 5%. The results of the artificial neural network (ANN) modeling showed that the maximum selectivity occurs in the range of 0.37–0.42 ppm of EDC. Also, it was observed that with decrease of gas velocity the difference between the EO mole fraction of gas phase and solid phase increases. This behavior was attributed to the distinct resistances of kinetically controlled and the mass transfer resistance of gas film around the catalyst pellets. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101319d [article] Modeling and simulation of an industrial ethylene oxide (EO) reactor using artificial neural networks (ANN) [texte imprimé] / M. R. Rahimpour, Auteur ; M. Shayanmehr, Auteur ; M. Nazari, Auteur . - 2011 . - pp. 6044–6052. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 10 (Mai 2011) . - pp. 6044–6052 Mots-clés : Ethylene oxide Artificial neural networks Résumé : In the present work, a one-dimensional heterogeneous model was used for dynamic simulation of an industrial fixed-bed catalytic ethylene oxide (EO) reactor in the presence of long-term catalyst deactivation. In order to determine the level of optimum ethylene dichloride (EDC), a multilayer perceptron (MLP) neural network was used. In addition, the effect of inlet gas velocity on EO mole fraction of gas and solid phases was investigated. The model validation was carried out by comparison of model results with corresponding industrial conditions and over a period of three operating years. A good agreement was found between the simulation results of the dynamic model and historical process data. The error of simulation was found to be less than 5%. The results of the artificial neural network (ANN) modeling showed that the maximum selectivity occurs in the range of 0.37–0.42 ppm of EDC. Also, it was observed that with decrease of gas velocity the difference between the EO mole fraction of gas phase and solid phase increases. This behavior was attributed to the distinct resistances of kinetically controlled and the mass transfer resistance of gas film around the catalyst pellets. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101319d

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Simultaneous removal of urea, ammonia, and carbon dioxide from industrial wastewater using a thermal hydrolyzer−separator loop / M. R. Rahimpour in Industrial & engineering chemistry research, Vol. 48 N° 22 (Novembre 2009)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 48 N° 22 (Novembre 2009) . - pp. 10037–10046 Titre : Simultaneous removal of urea, ammonia, and carbon dioxide from industrial wastewater using a thermal hydrolyzer−separator loop Type de document : texte imprimé Auteurs : M. R. Rahimpour, Auteur ; H. R. Mottaghi, Auteur Année de publication : 2010 Article en page(s) : pp. 10037–10046 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Industrial wastewater Hydrolyzer−  separator loop Résumé : In this work, simultaneous removal of urea, ammonia, and carbon dioxide from industrial wastewater was studied via modeling and simulation of a hydrolyzer−separator loop. The extended electrolytic UNIQUAC equation has been used to describe the nonideality of the liquid phase and the perturbed-hard-sphere (PHS) equation of state has been applied to predict the vapor fugacity coefficients. This work also uses a multistage well-mixed model for the liquid and vapor flows with a nonideal rate-based model for urea thermal hydrolyzer. Our study incorporates the reaction rate of urea hydrolysis and takes into account the effects of solution nonideality and backmixing on the reactor performance. The rates of urea reaction are written in terms of activity of reactants. The model provides temperature and flow rate distributions of different components along the height of the hydrolysis reactor and the desorbers. The simulation results have been found to be in good agreement with the plant data indicating the validity of the model. The impact of different parameters on the performance of the wastewater treatment loop has been examined. The results of this work showed that an increase in the inlet temperature of the wastewater and steam flow rate and also decrease the reflux ratio would improve the urea and ammonia removal efficiency. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900751g [article] Simultaneous removal of urea, ammonia, and carbon dioxide from industrial wastewater using a thermal hydrolyzer−separator loop [texte imprimé] / M. R. Rahimpour, Auteur ; H. R. Mottaghi, Auteur . - 2010 . - pp. 10037–10046. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 22 (Novembre 2009) . - pp. 10037–10046 Mots-clés : Industrial wastewater Hydrolyzer−  separator loop Résumé : In this work, simultaneous removal of urea, ammonia, and carbon dioxide from industrial wastewater was studied via modeling and simulation of a hydrolyzer−separator loop. The extended electrolytic UNIQUAC equation has been used to describe the nonideality of the liquid phase and the perturbed-hard-sphere (PHS) equation of state has been applied to predict the vapor fugacity coefficients. This work also uses a multistage well-mixed model for the liquid and vapor flows with a nonideal rate-based model for urea thermal hydrolyzer. Our study incorporates the reaction rate of urea hydrolysis and takes into account the effects of solution nonideality and backmixing on the reactor performance. The rates of urea reaction are written in terms of activity of reactants. The model provides temperature and flow rate distributions of different components along the height of the hydrolysis reactor and the desorbers. The simulation results have been found to be in good agreement with the plant data indicating the validity of the model. The impact of different parameters on the performance of the wastewater treatment loop has been examined. The results of this work showed that an increase in the inlet temperature of the wastewater and steam flow rate and also decrease the reflux ratio would improve the urea and ammonia removal efficiency. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900751g

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