Heuristic Design of Reaction/Separation Processes with Two Recycles

Abstract

A recent paper presented a heuristic approach to quickly estimate the optimum tradeoff between reactor size and recycle flow rate during the preliminary conceptual process design of a reaction/separation process. The basic idea is to find the minimum recycle flow rate by designing the process to meet some specified conversion/yield/selectivity criterion, using a very large reactor. A heuristic of setting the actual recycle flow rate equal to 1.2 times the minimum then is used to obtain an approximate optimum design. The process studied had relative volatilities such that only one recycle stream was needed. The purpose of this paper is to extend this work to the case where two recycle streams are required. There is a reactor and three distillation columns with two recycle streams. The desired product C is produced via the reaction A + B → C. An undesired product D is also produced. Two alternative reactions (A + C → D or A + B → D) mean that there is a large recycle of either B or A to achieve high selecti...