Entropy Minimization in Design of Extractive Distillation System with Internal Heat Exchangers

摘要

A methodology for entropy production minimization in design of extractive diabatic distillation systems is proposed. The feasibility of the design is obtained by the boundary value method used by Doherty and coworkers, and the optimal design is attained using a genetic algorithm, this strategy allows determine the optimal heat load distribution, and the flows and temperatures for hot and cold utilities. For optimal design of diabatic distillation columns it was employed a multilevel strategy, the first level solves the optimal adiabatic design and the second one determines the optimal heat load distribution in the sequential heat exchangers (SHE), in both levels the feasibility of the designs is forced by a penalty in the objective function, it considers the separation feasibility and the energy balance consistency. The ethanol dehydration by extractive distillation with ethylene glycol is assessed in order to show our optimal design procedure and to compare the diabatic distillation process with the adiabatic one. Results show that this strategy allows to solve the problem, and that with SHE, the entropy production can be reduced expressively: 14% for the recovery solvent column and 16% for the extractive one, compared to the adiabatic columns.