A hybrid design combining double-effect thermal integration and heat pump to the methanol distillation process for improving energy efficiency

Despite the low energy efficiency of distillation, it remains the popular separation technology for methanol purification. Enlightened by progress in heat pump (HP) concepts, which have been proposed to upcycle waste heat and reduce energy consumption, this work introduces a hybrid methanol distillation process, which elaborately integrates the HP with double-effect thermal integration by designing an intermediate heater to shunt the heat load of the reboiler. Simultaneously, a corresponding optimization function and schematic solution procedure based on pinch technology are proposed to minimize the operational expenditure. The calculation results demonstrate the validity of the optimization method. Compared with the popular 4-column double-effect methanol distillation scheme, the hybrid scheme can considerably reduce utility depletion as well as operating costs, with an acceptable payback period for the compressor. As a result, the hybrid design that gets the advantage of both double-effect and HP is worth extending to the methanol community as well as to other industrial plants.