考虑塔压变量优化的精馏塔间热集成

Heat Integration of Different Distillation Columns Considering Pressure Variable Optimization

塔压是改变塔内温度分布的关键参数。传统设计一般先固定塔压,然后再搜寻可能的热集成,未考虑精馏与换热过程的同步优化。以塔压为关键耦合变量优化塔间的热集成,首先给出筛选热集成物流的启发式规则,然后借助流程模拟数据建立塔压与待选物流温度的约束关系,最后以年度总费用为目标函数建立了考虑塔压参数作为变量的热集成优化模型,并利用GAMS软件求解。以某炼化企业40 kt·a^(-1)干气制乙苯的精馏系统为研究背景,将塔压与物流温度关系线性化。案例研究表明:苯塔和乙苯塔的压力分别为1.5和0.82 MPa时,对应最优的热集成方案,其年度总费用为9310000 CNY·a^(-1),热集成的经济效益约为39890000 CNY·a^(-1)。本研究揭示了塔压作为耦合变量对热集成的影响及作用机制,即塔压越高并非热集成效果越好,应考虑热集成系统中不同换热过程的相互影响和制约。

Pressure is a key parameter in controlling temperature distribution inside columns.Traditional column design usually fixes pressure first,and then possible heat integration opportunities are searched without considering simultaneous optimization of distillation and heat exchange.In this paper,column pressure was regarded as a key coupling variable in heat integration.Heuristic rules for screening streams of heat integration were first presented,and then the constraints between pressure and stream temperature were built using simulation data.Finally,annual cost as the objective function was expressed in the heat integration optimization model considering pressure as a variable,and GAMS was used to solve the problem.A distillation system which can produce40kt?a?1of ethylbenzene from dry gas was taken as a case study from petrochemical industry,and the relationship between pressure and temperature was linearly fitted.The case study shows that the optimal pressures of the benzene and ethylbenzene columns are1.5MPa and0.82MPa,respectively.The total annual cost in the optimal heat integration scheme is9.31million CNY?a?1,and its economic benefits is about39.89million CNY?a?1.This study shows the effect and mechanism of pressure as a coupling variable on heat integration.Higher pressure does not result in better heat integration,and mutual effects/restraints should be considered in different heat exchanger processes of heat integrated systems.