热泵辅助甲醇精馏工艺优化及分析

Optimization and analysis of heat pump-assisted methanol distillation processes

以30万t/a煤制甲醇工厂数据为基础,将热泵精馏技术引入甲醇四塔双效精馏工艺,开发了2种热泵强化甲醇精馏流程:外挂覆叠式热泵强化流程和二级压缩热泵强化流程。首先运用Aspen Plus软件对流程进行了工艺模拟,然后以最小年度总费用(TAC)为目标函数,运用网格自适应搜索算法对流程进行了优化,最后分别以年度总费用、碳排放和[火用]效率为经济、环境和能效指标对基础流程和2个热泵强化流程进行了分析和比较。结果显示:2个热泵强化流程的TAC相对于基础流程可分别降低7.49%和23.01%,碳排放减少29.53%和38.37%,而[火用]效率从7.01%提升为7.44%和8.92%,因此,2个热泵强化流程都可以实现明显的节能减排,而外挂覆叠式热泵强化流程更适合旧厂改造,二级压缩热泵强化流程更适合新厂建设。

Two heat pump(HP)assisted methanol distillation processes,external cascade HP enhanced scheme(ECHP)and two-stage compression HP enhanced scheme(TSCHP),were developed by introducing the HP technology into the basic four-column double-effect process based on the industrial data of a 300000 t/a coal to methanol plant.The processes were firstly simulated with Aspen Plus software,and then optimized by employing the total annual cost(TAC)as the objective function and using the mesh adaptive direct search algorithm.Finally,the three parameters of TAC,CO_(2)emission and exergy efficiency were respectively used as economic,environmental,and energy efficiency indicators to quantify and compare the two HP-assisted processes with the basic one.The results indicate that,compared to the basic process,the TAC and CO_(2)emissions of ECHP and TSCHP can be reduced by 7.49%and 23.01%,29.53%and 38.37%,respectively,while the exergy efficiency is boosted from 7.01%to 7.44%and 8.92%.Therefore,both of the two HP-assisted processes can significantly save energy and reduce CO_(2)emissions,ECHP is more suited for upgrading the existing facilities,while TSCHP is better suited for constructing new plants.