Disjunctive optimization design models for complex liquid-liquid multistage extractors

A new method for the optimal design of multicomponent liquid-liquid extract ion processes using multistage countercurrent extractor systems is proposed . The method determines the optimum number of equilibrium stages and flow r ates needed to obtain a specified product separation and recovery, and acco unts for the possibility of side feed streams and product extractions. A su perstructure is proposed that has embedded all potential configurations and interconnections. Based on this superstructure representation, the problem is formulated as an optimization problem using generalized disjunctive pro gramming (GDP) to minimize the total cost of the process', subject to desig n specifications. The robustness and computational efficiency of the model is illustrated with different cases involving single and complex countercur rent cascades in a quaternary liquid-liquid system.