Steady state multiplicity in gas-liquid CSTRs

(1992) Steady state multiplicity in gas-liquid CSTRs. Masters thesis, King Fahd University of Petroleum and Minerals.


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A comprehensive model has been developed for the study of steady state multiplicity features of non-isothermal, non-adiabatic, gas-liquid continuous stirred tank reactors (CSTRs). The theretical development takes into consideration the reaction kinetics, the interphase mass transfer, the mode of physical contact, and for the first time both reactor and impeller geometry. Possible variations in the hydrodynamic and transport parameters due to variable operating conditions also for the first time have been taken into account y incorporating empirical correlations in the model for these parameters. A comprehensive review of empirical correlations for various hydrodynamic, transport and associated parameters used in the model has also been presented. The influence of chemical reaction on gas absorption has been taken into consideration by using a new approximate reaction factor expression derived based on general second-order kinetics and spherical bubble geometry. A parametric study on the so-called local model shows that when the size of the gas bubble is comparable to the thickness of concentration boundary layer around it, the spherical effect depending on the system conditions may significantly increase or decrease the reaction factor values. A detailed parametric study was carried out to show the individual effects of reactivity, nature of feed fas, gas and liquid feed temperatures and their flow rates, and degree of agitation. The results obtained by the rigorous model are compared with those predicted by simplified models reported in the literature. The analysis shows that although the proposed model predicts similar multiplicity patterns and maximum number of steady states, the conditions under which they occur are significantly different. The hydrodynamic and transport parameters which have been assumed constant by the previous investigators have been shows to vary significantly with the operating conditions indicating that the predictions of multiplicity behavior based on previous simplified models are conservative.

Item Type: Thesis (Masters)
Subjects: Chemical Engineering
Department: College of Chemicals and Materials > Chemical Engineering
Committee Advisor: Shaikh, Abdullah A.
Committee Members: Hastaoglu, Mehmet A. and Al-Naafa, M. A.
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 13:54
Last Modified: 01 Nov 2019 13:56