Optimization Of Distillation Sequence Including Non-sharp Separation

The distillation sequence including non-sharp separation is widely used in industrial separation processes,such as petroleum refinery whose each product obtained by separating crude oil according to boiling point ranges are overlapped with adjacent one.Compared to sharp separation,non-sharp separation makes middle components distributed to both top outflow and buttom outflow,increasing freedom degree and complexity of the system.Current research is mainly focused on optimization of sharp distillation sequence,sharp distillation sequence including dividing wall column and heat integrated complex column distillation sequence under special operating condition.The distillation sequence is optimized by adjusting the separation sequence and the operation parameters of each column in the sequence,which makes the problem to a mixed integer non-linear programming.In this work,the optimization of sharp and non-sharp distillation sequence is compared.The formulation for sequence number including non-sharp separation is derived.subgroup number and sub-problem number are also obtained by recurrence program.The solution space with non-sharp separation is discussed.Inspired by dynamic programing method for sharp distillation sequence,A program framework calling Aspen Plus strict distillation module by ActiveX interface is proposed to decompose the MINLP problem into IP problem and NLP problems,optimized in main optimization program coded by Python and Aspen Plus strict distillation module respectively.Compared to solving whole MINLP problem through random searching or branch and bound,optimization efficiency is improved by this method.Two optimization cases,including an industrial one,are included to validate the proposed framework.