酸性气体脱除单元再吸收系统优化探讨

以某公司1.8 Mt/a甲醇合成装置的酸性气体脱除单元为例,介绍了典型贫液/半贫液酸性气体脱除单元再吸收工艺流程及其存在的技术缺陷,主要体现在半贫液溶解的CO_2的摩尔分数高达12%,对酸性气的吸收能力弱,导致系统运行能耗高。针对酸性气体脱除单元再吸收系统存在的技术缺陷,开发出了准贫液循环吸收、多股氮气气提和单泵双循环等新技术,使准贫液中溶解的CO_2的摩尔分数降低至6.5%。通过对比优化前后主要工艺参数,结果表明:优化后的再吸收流程在准贫液循环量、循环冷却水消耗、送热再生的富甲醇量、冰机及动力消耗等方面均取得了很好的优化效果,酸性气体脱除单元综合能耗下降6%,每年可节约操作费用1 000万元。优化后的再吸收流程工艺适用于大型酸性气体脱除单元的工程设计或扩能改造。

Study on optimization of reabsorption system in sour gas removal unit

Through a case study of the acid removal unit of a 1.8 MM TPY methanol plant,the reabsorption process of typical lean/semi lean liquid sour gas removal unit is introduced.The main technical defects in reabsorption process are analyzed,such as the content of carbon dioxide in semi lean liquid is up to 12 mol％,the absorption capacity of acid gas is low,and the energy consumption is high.In order to solve these defect problems,quasi lean liquid circulation absorption,multi nitrogen gas stripping,and single pump double circulation technologies are developed,which can reduce the carbon dioxide dissolved in the lean liquid to 6.5％.The comparison of the main process parameters before and after optimization shows that,after the optimization,good results have been achieved in lean liquid circulation rate,cooling water consumption,amount of rich methanol for hot regeneration and power consumption,etc.The energy consumption of sour gas removal unit is decreased by 6％,and annual saving of operation cost is 10 million Yuan (RMB).The optimized reabsorption process is good for the engineering of large sour gas removal unit or expansion revamping.