A COMPARATIVE STUDY OF BATCH AND SEMI-BATCH REACTOR PERFORMANCE FOR A PARALLEL-CONSECUTIVE REACTION UNDER ISOTHERMAL AND NONISOTHERMAL CONDITIONS

Abstract

The performances of semi-batch and batch reactors are compared using a variety of conditions. Differential equations for mass and thermal balances are presented for the general semi-batch process and integrated solutions for particular cases are obtained for the final temperature rise in the adiabatic case. Reduced variables and dimensionless parametric groups were employed to produce differential equations of more general applicability than hitherto. For adiabatic reactions, numerical solutions of the appropriate differential equations should be self-consistent with integrated, thermodynamic results. To illustrate the further considerations required in the application of the general schema, an exothermic parallel-consecutive reaction occuring in the liquid phase was considered: A+B→C, A+C→D and comparison is made to the related batch process with equivalent stoichiometric amounts. The reaction scheme was studied under isothermal and nonisothermal conditions; in the latter case, both adiabatically and with heat transfer. This example is of practical significance and poses an interesting problem in selectivity involving a non-trival energy balance. Numerical computation predicts that the performance of a semi-batch reactor matches a batch reactor when a solution of A is added to a solution of B using either an isothermal or an adiabatic operation; but with heat transfer facility, a purer intermediate product C may be obtained from a semi-batch reactor. When a solution of B is added to one of A, or when an initially empty tank is being filled with reaction mixture, the reaction path deviates from the batch reactor case and further reaction of C is favoured. Usually, semi-batch operation time exceeds that for batch processing and is a self-limiting criterion of performance. These disparate elements of performance are combined in a figure-of-merit to facilitate comparison of the overall productive outcome