甲醇合成及精馏单元的能效优化

甲醇生产工艺普遍存在能耗、水耗过高的问题,对该工艺进行过程集成节能研究,具有重要的意义。以60万t/a煤制甲醇装置为背景,将处于上下游关系的甲醇合成及精馏单元作为一个系统考虑。利用夹点技术对该系统的用能现状和换热网络进行了分析,找出了违背夹点设计原则的不合理换热匹配。在此基础上,通过充分回收系统高温热源尤其是甲醇合成塔出塔合成气的能量,提出了2种现行换热网络的优化方案。方案1:节约低压蒸汽34.8%,节约脱盐水和循环冷却水21.1%,其中节约1.2 MPa低压蒸汽2 277.7 kW,节约0.3 MPa低压蒸汽20 544.4 kW;方案2:节约低压蒸汽30.8%,节约脱盐水和循环冷却水18.7%,其中节约1.2 MPa低压蒸汽6 027.0 kW,节约0.3 MPa低压蒸汽14 157.5 kW。当1.2 MPa与0.3 MPa低压蒸汽价格差距较大时,选择方案2较合理。

Energy efficiency optimization of methanol synthesis and distillation units

The production of methanol is a process of high energy and water consumption,therefore,the relevant process integration research has the vital significance.The upstream and downstream units of methanol synthesis and distillation were considered as one system based on a 6×105 t/a coal to methanol device.In this process,the energy usage and heat exchanger network(HEN) were analyzed by pinch technology,and those illogical heat exchanger matches against the pinch design principles were found.On that basis,two optimization schemes for current HEN were designed to sufficiently recover the heat source of high temperature in the system,especially the heat of syngas coming out of the methanol synthesis reactor.Scheme 1: saving 34.8% low pressure steam and 21.1% desalinated water and circulating cooling water,among which saving 1.2 MPa low pressure steam 2 277.7 kW and 0.3 MPa low pressure steam 20 544.4 kW.Scheme 2: saving 30.8% low pressure steam and 18.7% desalinated water and circulating cooling water,among which saving 1.2 MPa low pressure steam 6 027.0 kW and 0.3 MPa low pressure steam 14 157.5 kW.In the circumstances of large price gap between 1.2 MPa and 0.3 MPa low pressure steams,the scheme 2 is more reasonable.