乙烯深冷分离中变温冷却过程制冷系统的设计与优化

根据乙烯装置中的用冷需求,将乙烯装置的深冷分离过程分为变温冷却过程和定温冷凝过程,变温冷却过程指的是裂解气的预冷过程,定温冷凝过程指的是乙烯装置中各塔塔顶冷凝器中的换热;分析了乙烯-丙烯复叠制冷系统的换热集成曲线,可知在裂解气的预冷阶段,冷热物流换热温差大。提出一种组合制冷系统,它集成了纯工质复叠制冷和混合冷剂制冷,其中的多元混合冷剂制冷系统为乙烯深冷分离的变温换热过程提供冷量。并用Aspen Plus软件对混合冷剂系统进行建模,使用遗传算法优化,优化结果表明在替代原制冷系统6895.5 kW冷量负荷的情况下,功耗降低521.6 kW,节能14.7%。

Design and optimization of refrigeration separation system for variable-temperature cooling process in ethylene cryogenic separation process

According to the cooling demand of the ethylene plant,cracking gas cooling-separation process is divided into a variable-temperature cooling process and a constant-temperature cooling process,corresponding to the precooling process of cracking gas and the overhead condenser of towers in the ethylene plant,respectively.In this study,the heat exchange composite curve of the original refrigeration system(ethylene-propylene cascade refrigeration systems)was obtained,indicating that the heat exchange temperature difference between cold and hot streams is massive in precooling process of cracking gas.The heat exchange losses can be reduced by a suitable mixed refrigerant system.Furthermore,a combining multiple mixed refrigerant and cascade refrigeration system was proposed.The combinatorial refrigeration system model was set up with Aspen Plus.And genetic algorithm was adopted as the optimization method,with system variables such as refrigerant components,outlet pressure of compressor,and pressure in outlet of the throttle.Eventually,the compression power in the optimal solution was 3025.5 kW,which was 14.7% lower than that in the pure refrigerant systems.