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

The performances of semi-batch and batch reactors are compared using a variety of conditions. Differential equations for mass and thermal ba lances 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 param etric groups were employed to produce differential equations of more g eneral applicability than hitherto. For adiabatic reactions, numerical solutions of the appropriate differential equations should be self-co nsistent with integrated, thermodynamic results. To illustrate the fur ther considerations required in the application of the general schema, an exothermic parallel-consecutive reaction occurring in the liquid p hase was considered: A + B --> C (1) A + C --> D (2) and comparison is made to the related batch process with equivalent stoichiometric amou nts. The reaction scheme was studied under isothermal and nonisotherma l conditions; in the latter case, both adiabatically and with heat tra nsfer. This example is of practical significance and poses an interest ing problem in selectivity involving a non-trival energy balance. Nume rical computation predicts that the performance of a semi-batch reacto r 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 he at transfer facility, a purer intermediate product C may be obtained f rom a semi-batch reactor. When a solution of B is added to one of A, o r when an initially empty tank is being filled with reaction mixture, the reaction path deviates from the batch reactor case and further rea ction of C is favoured. Usually, semi-batch operation time exceeds tha t 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.