Batch reactor comparison with CSTR

A comparison of this equation with Equation 1) demonstrates that functional relationships between dependent and independent variables can be quite different for CSTR s and batch reactors, even with the same reaction system and the same kinetic mechanisms. 

A performance comparison between a BR and a CSTR may be made in terms of the size of vessel required in each case to achieve the same rate of production for the same fractional conversion, with the BR operating isothermally at the same temperature as that in the CSTR. Since both batch reactors and CSTRs are most commonly used for constant-density systems, we restrict attention to this case, and to a reaction represented by... 

This means that as long as a CSTR is used as the first stage reactor and all the recipe ingrediants are fed into the first stage reactor, one cannot have more than 57% of the number of particles produced in a batch reactor with the same recipe as in continuous operation. The validity of these expression is clear from the comparison between the experimental and theoretical values shown in Figure 5. From Figure 5, it is found that the optimum mean residence time of the first stage reactor is about 10 minutes under these reaction conditions. Equation(30) predicts 10.0 minutes, while experimental value is 10.4 minutes where the number of polymer particles is about 60% of that produced in a batch reactor. 

Experimental. Figure 2 compares molecular weight data reported by Garden (J 0) for batch reactors and by Poehlein for CSTR reactors ( ), with the data obtained in this study for a tubular reactor. The solid lines are predicted by Garden s theory (10). The molecular weights obtained in this experimenTal study were predicted within a factor of 3 by Garden s theory. No direct comparison can be made with the data of other workers, yet this molecular weight data is consistent (at least within experimental error) with data obtained in other types of reactors. 

Depending upon the particular polymer system, a CSTR or a series of CSTRs may offer several advantages over batch and tubular flow reactors both with respect to polymer production rate and polymer quality. With a perfectly mixed CSTR it is often possible to achieve a molecular weight distribution considerably narrower than can be obtained with a batch (or tubular) reactor with the same holdup time. This is true with any polymerization where molecular weights are controlled by termination. By running CSTRs in series or in parallel it is possible to produce tailor-made polymers with a broader MWD simply by operating each CSTR at a different temperature and/or with different residence times. Another feature of CSTRs is that the CCD can be very narrow in comparison with batch (or tubular) reactors, where the CCD is broadened due to the drift in monomer composition. 

Our treatment of Chemical Reaction Engineering begins in Chapters 1 and 2 and continues in Chapters 11-24. After an introduction (Chapter 11) surveying the field, the next five Chapters (12-16) are devoted to performance and design characteristics of four ideal reactor models (batch, CSTR, plug-flow, and laminar-flow), and to the characteristics of various types of ideal flow involved in continuous-flow reactors. Chapter 17 deals with comparisons and combinations of ideal reactors. Chapter 18 deals with ideal reactors for complex (multireaction) systems. Chapters 19 and 20 treat nonideal flow and reactor considerations taking this into account. Chapters 21-24 provide an introduction to reactors for multiphase systems, including fixed-bed catalytic reactors, fluidized-bed reactors, and reactors for gas-solid and gas-liquid reactions. 

Almost innumerable instances of such reactions are practiced. Single-batch stirred tanks, CSTR batteries, and tubular flow reactors are all used. Many examples are given in Table 17.1. As already pointed out, the size of equipment for a given purpose depends on its type. A comparison has been made of the production of ethyl acetate from a mixture initially with 23% acid and 46% ethanol these sizes were found for 35% conversion of the acid (Westerterp, 1984, pp. 41-58) ... 

The hrst part serves as an introduction to the subject title and contains chapters dealing with history, process variables, basic operations, chemical kinetic principles, and stoichometry and conversion variables. The second part of the book addresses traditional reactor analysis chapter topics include batch, CSTRs, and tubular flow reactors, plus a comparison of these classes of reactors. Part IH keys on reactor applications that include thermal elfects, interpretation of kinetic data, non-ideal reactors, and reactor design. The book concludes with other reactor topics chapter titles include catalysis, catalytic reactions, fluidized and fixed bed reactors, biochemical reactors, open-ended questions, and ABET-related topics. An Appendix is also included. 

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