MTO级甲醇合成系统能效优化研究

Energy efficiency optimization of MTO grade methanol synthesis system

甲醇生产过程普遍存在能耗、水耗过高的问题,对该系统进行节能研究具有重要的意义。文章通过夹点分析技术,对MTO级甲醇合成系统换热网络进行分析优化,按照避免热流量通过夹点换热、不应有跨越夹点的传热等原则,以及一次换热处理完一股物流的设计经验,对MTO级甲醇合成系统进行能耗方面的优化。以120万t/a煤制甲醇为例,把合成器出口气体分成2股,一股用来加热原料气,一股用来给预精馏塔底提供热量。优化后反应器出口物流经一次换热后温度比原来降低了近30℃,充分利用了甲醇合成反应器出口物流的热能,同时节省0.56MPa低压蒸汽140 t/h,节约循环水量2 770 t/h,节省整个系统单元的蒸汽和循环水量达98.75%,为甲醇合成单元提高能效、降低系统能耗提供一定的参考。

The production of methanol is a process of high energy and water consumption,therefore,the relevant energy conservation research has the vital significance. In this paper,the heat exchanger network（HEN） of MTO grade methanol synthesis system were analyzed and optimized by pinch technology. According to pinch point design philosophy： avoiding heat flux passing pinch point and the heat transfer should not be across the pinch point,and one heat exchange finish one flow design experience,the energy consumption of MTO grade methanol synthesis system was optimized. Take 1 million 200 thousand tons of coal to methanol for example,split outlet gas of the reactor into two flows,one to heat the feed gas and one provide heat for the pre-fractionating column. After optimizing,the temperature of outlet gas by the first heat exchange is 30 ℃ lower than now. It is made full use of the heat energy of outlet gas in the optimized process,also saved 0. 56 MPa low-pressure steam 140 t/h,saved circulating water 2 770 t/h. All of this is up to 98. 75% of the total consumption of steam and circulating water.This method can provide a reference for the methanol synthesis unit to improve energy efficiency and reduce the energy consumption of the system.