基于双级精馏塔的LNG冷能空气分离工艺优化

摘要

针对典型的LNG冷能空气分离工艺存在单位质量产品能耗较高、工艺流程可优化空间大等现状,介绍了一种LNG冷能用于空气分离流程的新模型.在对比传统空气分离工艺的缺点、详细分析典型的LNG冷能空气分离工艺流程优化可行性的基础上,提出了采用双级精馏塔空气分离的优化工艺流程:一级精馏塔预冷分离富氧液空,二级精馏塔分离液氮.使用Aspen Plus进行流程模拟,物性方程选用Pen-Robinson,并根据模拟数据计算分析产品能耗.计算结果表明:此优化工艺与传统空气分离工艺单位质量能耗1.05 ～ 1.25 kWh相比,降低了50％以上.另外,利用黑箱模型研究了此流程中换热器的(火用)效率问题,计算得到η=12.6％,并分析了(火用)效率较低的原因,给出了该优化工艺应用建议.%A new model of LNG cold energy for air separation process is presented for the typical LNG cold energy air separation process,which has the advantages of high energy consumption per unit product and large optimization of process flow.In contrast to the traditional air separation process shortcomings,and according to analysing the optimization feasibility of typical LNG cold air separation process in details,the authors put forward the optimization of air separation with two-stage distillation tower:a distillation column pre cooling separation of oxygen enriched liquid air,liquid nitrogen two distillation separation.Aspen Plus was used for process simulation,Pen-Robinson was used as physical properties equation,and product energy consumption was analysed according to simulation data.The calculation results show that,compared with conventional air separation process unit mass energy consumption 1.05 ～ 1.25 kWh,the optimization process is reduced by more than half.In addition,the energy efficiency of the heat exchanger in the process was studied by using the black box model,it was obtained that η=12.6％,the reason of low efficiency of energy was also analyzed.Finally,the suggestions of the optimization process in practical production were given.