Szepe

As Levenspiel points out, the optimum size ratio is generally dependent on the form of the reaction rate expression and on the conversion task specified. For first-order kinetics (either irreversible or reversible with first-order kinetics in both directions) equal-sized reactors should be used. For orders above unity the smaller reactor should precede the larger for orders between zero and unity the larger reactor should precede the smaller. Szepe and Levenspiel (14) have presented charts showing the optimum size ratio for a cascade of two reactors as a function of the conversion level for various reaction orders. Their results indicate that the minimum in the total volume requirement is an extremely shallow one. For example, for a simple... 

The optimum size ratio for two mixed flow reactors in series is found in general to be dependent on the kinetics of the reaction and on the conversion level. For the special case of first-order reactions equal-size reactors are best for reaction orders n > 1 the smaller reactor should come first for n < 1 the larger should come first (see Problem 6.3). However, Szepe and Levenspiel (1964) show that the advantage of the minimum size system over the equal-size system is quite small, only a few percent at most. Hence, overall economic consideration would nearly always recommend using equal-size units. 

Although the above /tth-order expressions are quite simple they are general enough to embrace many of the decay equations used to date [see Szepe and Levenspiel (1968)]. 

Szepe, S., Ph.D. Thesis, Illinois Institute of Technology, 1966 also see Szepe, S., and O. Levenspiel, Chem. Eng. ScL, 23, 881 (1968) Catalyst Deactivation, p. 265, Fourth European Symposium on Chemical Reaction Engineering, Brussels, September 1968, Pergamon, London, 1971. 

Szepes, A., Makai, Z., Bliimer, C., Mader, K., Kasa, P. Jr., Szabo-Revesz, P. (2008). Characterization and drug delivery behaviour of starch-based hydrogels prepared via isostatic ultrahigh pressure. Carbohydr. Poly., 72(4), 571-578. 

In analyzing reactions over deactivating catalysts, we can follow separable or non-separa-ble kinetics. According to separable kinetics, Szepe and Levenspiel used two different terms one for the reaction kinetics (independent of time) and another for activity (time dependent). Consequently,... 

Szepe, S, Levenspiel, O., Proceedings of the Fourth European Symposium on Chemical Reaction Engineering, Pergamon Press, Brussels (1971)... 

Szepe, S. Levenspiel, 0. Proc. 45h Euro. Syrap. Chem. Reac. Eng., 1968 265- Pergaraon Press, Oxford. 

Normally, commercial HDS reactors are operated under adiabatic conditions. The heat removal is achieved by the addition of quench fluids. Mhaskar and Shah27 carried out a similar analysis for reactors which are operated non-isothermally under the conditions of either constant wall temperature or constant wall heat flux. For simplicity, they assumed that the catalyst desulfurization activity function

rate equation proposed by Szepe,55 namely,... 

Approximate reaction networks have become customary for modeling reactions in which the species are too numerous for a full accounting or chemical analysis. Lumped components or continuous distributions commonly take the place of single components in process models for refinery streams (Wei and Kuo 1969 Weekman 1969 Krambeck 1984 Astarita 1989 Chou and Ho 1989 Froment and Bischoff 1990). Polymerization processes are described in terms of moments of the distributions of molecular weight or other properties (Zeman and Amundson 1965 Ray 1972, 1983 Ray and Laurence 1977). Lumped components, or even hypothetical ones, are also prevalent in models of catalyst deactivation (Szepe and Levenspiel 1968 Butt 1984 Pacheco and Petersen 1984 Schipper et al. 1984 Froment and Bischoff 1990). 

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