Documents disponibles écrits par cet auteur

Operating parameters and selectivity in batch reactive distillation / Wei Qi in Industrial & engineering chemistry research, Vol. 49 N° 22 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 22 (Novembre 2010) . - pp. 11547–11556 Titre : Operating parameters and selectivity in batch reactive distillation Type de document : texte imprimé Auteurs : Wei Qi, Auteur ; Michael F. Malone, Auteur Année de publication : 2011 Article en page(s) : pp. 11547–11556 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Reactive  distillation Résumé : This Article provides new predictions for selectivity in batch reactive distillation, identifying the reflux or reboil ratio and a Damköhler number (Da) as the key operating parameters. The dimensionless Da incorporates the influence of liquid holdup, vapor rate, and rate of reaction. Example results for a system of serial isomerization reactions and for the synthesis of ethylene glycol are provided. The results show that selectivity improvements in BRD are limited for high values of Da or for high values of the reflux or reboil ratio and that selectivity is enhanced as Da or reflux or reboil ratio is decreased. However, decreasing Da can cause conversion loss, which can be mitigated by increasing the reflux (or reboil) ratio at the expense of selectivity. Consequently, there is an optimum value of reflux or reboil ratio that gives a maximum yield for systems operated at low or moderate Da. For the isomerization in a BRD, the heat released by reaction can improve selectivity at the expense of conversion. For ethylene glycol synthesis at a low reboil ratio, BRD has a negative impact on both conversion and selectivity by causing separation of the reactants. We also show that decreasing the reboil ratio near the end of the BRD can increase the removal rate of EG and thereby improve selectivity. This operating strategy is different from a common operating strategy in distillation of increasing reboil ratio near the end of a batch or cut. We also find that an operation with a constant volumetric liquid flow rate provides lower selectivity than a constant molar liquid flow rate. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101417m [article] Operating parameters and selectivity in batch reactive distillation [texte imprimé] / Wei Qi, Auteur ; Michael F. Malone, Auteur . - 2011 . - pp. 11547–11556. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 22 (Novembre 2010) . - pp. 11547–11556 Mots-clés : Reactive  distillation Résumé : This Article provides new predictions for selectivity in batch reactive distillation, identifying the reflux or reboil ratio and a Damköhler number (Da) as the key operating parameters. The dimensionless Da incorporates the influence of liquid holdup, vapor rate, and rate of reaction. Example results for a system of serial isomerization reactions and for the synthesis of ethylene glycol are provided. The results show that selectivity improvements in BRD are limited for high values of Da or for high values of the reflux or reboil ratio and that selectivity is enhanced as Da or reflux or reboil ratio is decreased. However, decreasing Da can cause conversion loss, which can be mitigated by increasing the reflux (or reboil) ratio at the expense of selectivity. Consequently, there is an optimum value of reflux or reboil ratio that gives a maximum yield for systems operated at low or moderate Da. For the isomerization in a BRD, the heat released by reaction can improve selectivity at the expense of conversion. For ethylene glycol synthesis at a low reboil ratio, BRD has a negative impact on both conversion and selectivity by causing separation of the reactants. We also show that decreasing the reboil ratio near the end of the BRD can increase the removal rate of EG and thereby improve selectivity. This operating strategy is different from a common operating strategy in distillation of increasing reboil ratio near the end of a batch or cut. We also find that an operation with a constant volumetric liquid flow rate provides lower selectivity than a constant molar liquid flow rate. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101417m

Predicting the effect of the homogenization pressure on emulsion drop-size distributions / Neha B. Raikar in Industrial & engineering chemistry research, Vol. 50 N° 10 (Mai 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 10 (Mai 2011) . - pp. 6089–6100 Titre : Predicting the effect of the homogenization pressure on emulsion drop-size distributions Type de document : texte imprimé Auteurs : Neha B. Raikar, Auteur ; Surita R. Bhatia, Auteur ; Michael F. Malone, Auteur Année de publication : 2011 Article en page(s) : pp. 6089–6100 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Homogenization  pressure  Emulsion Résumé : We have previously developed a population balance equation (PBE) model for emulsion drop breakage in a high-pressure homogenizer that incorporated multiple-drop formation within two mechanisms of turbulent drop breakage. The model was found to satisfactorily predict the effects of formulation variables on the drop-size distribution, but the model was not extensible to a range of homogenization pressures. The objective of this paper is to determine the additional model elements necessary to obtain acceptable predictions over a wide range of pressures. The most significant improvements were obtained by increasing the number of daughter drops formed upon breakage from 20 to 150 drops and by introducing a maximum stable diameter, below which drops could not break. Smaller improvements were obtained by introducing terms that describe the loss of energy available for drop breakage due to thermal heating of the sample and homogenizer and by extending the model to account for the effects of surfactant adsorption and deficiency on the interfacial tension. The simultaneous implementation of all five enhancements was shown to produce a 62% improvement over the previous model, as measured by a least-squares objective based on the difference between the measured and predicted drop-size distributions over five homogenization passes and five pressures in the range 250−1250 bar. The resulting model was also validated over a range of oil and surfactant concentrations and shown to provide satisfactory predictions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101818h [article] Predicting the effect of the homogenization pressure on emulsion drop-size distributions [texte imprimé] / Neha B. Raikar, Auteur ; Surita R. Bhatia, Auteur ; Michael F. Malone, Auteur . - 2011 . - pp. 6089–6100. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 10 (Mai 2011) . - pp. 6089–6100 Mots-clés : Homogenization  pressure  Emulsion Résumé : We have previously developed a population balance equation (PBE) model for emulsion drop breakage in a high-pressure homogenizer that incorporated multiple-drop formation within two mechanisms of turbulent drop breakage. The model was found to satisfactorily predict the effects of formulation variables on the drop-size distribution, but the model was not extensible to a range of homogenization pressures. The objective of this paper is to determine the additional model elements necessary to obtain acceptable predictions over a wide range of pressures. The most significant improvements were obtained by increasing the number of daughter drops formed upon breakage from 20 to 150 drops and by introducing a maximum stable diameter, below which drops could not break. Smaller improvements were obtained by introducing terms that describe the loss of energy available for drop breakage due to thermal heating of the sample and homogenizer and by extending the model to account for the effects of surfactant adsorption and deficiency on the interfacial tension. The simultaneous implementation of all five enhancements was shown to produce a 62% improvement over the previous model, as measured by a least-squares objective based on the difference between the measured and predicted drop-size distributions over five homogenization passes and five pressures in the range 250−1250 bar. The resulting model was also validated over a range of oil and surfactant concentrations and shown to provide satisfactory predictions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101818h