The effect of off-cut recycle on the optimum design and operation of binary batch distillation with fixed product demand

摘要

Off-cut production and recycling played an important role in efficient separation of binary and multicomponent mixtures using batch distillation.However,the research in this area is handful and all the investigations until to date were concerned with only operation optimisation in terms of minimisation of batch time or maximisation of productivity (amount of main products per unit time).No consideration was given to market demand of the products;therefore these operation policies would result in under and over production of the products leading to potential revenue losses.In this work,for the first time we considered both design (number of stages,vapour load) and operation (reflux ratio,batch time) optimisation for fixed market demand of the products while maximising a profit function reflecting product revenues,operating cost,storage cost and annualised capital cost.The effect of off-cut production and recycling on the design,operation and profitability are evaluated using an easy and a difficult binary separation problem and off-cut recycling is found to be more beneficial for difficult separation.Design and operation policies are also found to be different for different amount of off-cut.Finally,the storage cost can be a deciding factor for the production and recycling of off-cut.