Experimental and optimization studies of diabatic membrane-based distillation columns

Abstract

Abstract Membrane-based distillation column (MDC) which utilizes hollow fibers as structured packings provides the advantages of large and fixed interfacial area and independent control of fluid flow rate without the constraints of flooding and loading. Diabatic distillation columns can approach the thermodynamic reversible operation, which is energy-efficient. MDC can be easily transformed into diabatic columns (D-MDC), i.e. with internal heat exchange, by adding a jacket as the flow channel for heating or cooling media. For the methanol-water system, the experimental results show noteworthy reduction of HTU (height of a transfer unit) under diabatic operation when compared to adiabatic operation. For the benzene-toluene system, the optimization of the internal heat exchange rates for D-MDC was conducted by a nested loop optimization algorithm, which incorporates the equipartition of entropy production (EoEP), equipartition of heat exchange rate (EoQ) or linear distribution of heat exchange rate (LQ) approximation, and an evolutionary approach. The optimal solutions of EoEP, EoQ and LQ provide significant improvements in specific exergy loss, exergy loss per NTU (number of transfer unit) and variance of driving force to adiabatic columns. The optimal solutions obtained from nested loop algorithm are superior to the solution from evolutionary approach.