Kinetic models, chemical process engineering

E. James Davis, Microchemical Engineering The Physics and Chemistry of the Microparticle Selim M. Senkan, Detailed Chemical Kinetic Modeling Chemical Reaction Engineering of the Future Lorenz T. Biegler, Optimization Strategies for Complex Process Models... 

The outlooks for the development of new fundamental concepts or for a general chemical engineering approach to catalytic processes will be summarized. RC takes place in numerous reactions. Many aspects are influenced by consideration of the RC concept activity and selectivity, catalyst formulation and "architecture", ageing processes, kinetic modelling, and process operation. 

Dente and Ranzi (in Albright et al., eds.. Pyrolysis Theory and Industrial Practice, Academic Press, 1983, pp. 133-175) Mathematical modehng of hydrocarbon pyrolysis reactions Shah and Sharma (in Carberry and Varma, eds.. Chemical Reaction and Reaction Engineering Handbook, Dekker, 1987, pp. 713-721) Hydroxylamine phosphate manufacture in a slurry reactor Some aspects of a kinetic model of methanol synthesis are described in the first example, which is followed by a second example that describes coping with the multiphcity of reactants and reactions of some petroleum conversion processes. Then two somewhat simph-fied industrial examples are worked out in detail mild thermal cracking and production of styrene. Even these calculations are impractical without a computer. The basic data and mathematics and some of the results are presented. 

Verneuil et al. (Verneuil, V.S., P. Yan, and F. Madron, Banish Bad Plant Data, Chemical Engineering Progress, October 1992, 45-51) emphasize the importance of proper model development. Systematic errors result not only from the measurements but also from the model used to analyze the measurements. Advanced methods of measurement processing will not substitute for accurate measurements. If highly nonlinear models (e.g., Cropley s kinetic model or typical distillation models) are used to analyze unit measurements and estimate parameters, the Hkelihood for arriving at erroneous models increases. Consequently, resultant models should be treated as approximations. 

A kinetic model based on the Flory principle is referred to as the ideal model. Up to now this model by virtue of its simplicity, has been widely used to treat experimental data and to carry out engineering calculations when designing advanced polymer materials. However, strong experimental evidence for the violation of the Flory principle is currently available from the study of a number of processes of the synthesis and chemical modification of polymers. Possible reasons for such a violation may be connected with either chemical or physical factors. The first has been scrutinized both theoretically and experimentally, but this is not the case for the second among which are thermodynamic and diffusion factors. In this review we by no means pretend to cover all theoretical works in which these factors have been taken into account at the stage of formulating physicochemical models of the process... 

Dr. Walas has several decades of varied experience in industry and academia and is an active industrial consultant for the process design of chemical reactors and chemical and petroleum plants. He has written four related books on reaction kinetics, phase equilibria, process equipment selection and design, and mathematical modeling of chemical engineering processes, as well as the sections Reaction Kinetics and Chemical Reactors in the seventh edition of Chemical Engineers Handbook. He is a Fellow of the AlChE and a registered professional engineer. 

Kusic, H Koprivanac, N Loncaric Bozic, A Papic, S Petemel, I Vujevic, D. Reactive dye degradation by a photochemical AOP - development of a kinetic model for UV/H2O2 process. Chemical and Biochemical Engineering Quarterly, 2006 in press. 

Lee, L.S., Chen, T.W., Haunh, T.N., and Pan, W.Y. (1989) Four lump kinetic model for fluid catalytic cracking process. Canadian Journal of Chemical Engineering, 67, 615. 

Glaze W H, Kang J-W (1989 a) Advanced Oxidation Processes. Description of a kinetic Model for the Oxidation of hazardous Materials in Aqueous Media with Ozone and Hydrogen Peroxide in a semibatch Reactor, Industrial Engineering Chemical Research 28 1573-1580. 

In order to make design or operation decisions a process engineer uses a process model. A process model is a set of mathematical equations that allows one to predict the behavior of a chemical process system. Mathematical models can be fundamental, empirical, or (more often) a combination of the two. Fundamental models are based on known physical-chemical relationships, such as the conservation of mass and energy, as well as thermodynamic (phase equilibria, etc.) and transport phenomena and reaction kinetics. An empirical model is often a simple regression of dependent variables as a function of independent variables. In this section, we focus on the development of process models, while Section III focuses on their numerical solution. 

The underlying assumption for developing a kinetic model is that it will provide a tool to assist engineers in determining important parameters of chemical degradation and the fate of the chemicals in the process [43], In addition, it serves as a guide to minimize the number of experiments required to obtain the necessary empirical information. 

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