二氧化碳加氢合成甲醇工艺系统分析

System Analysis of Methanol Synthesis by Carbon Dioxide Hydrogenation

[目的]二氧化碳捕集、利用和封存是实现全球温室气体净零排放的重要举措。二氧化碳加氢催化合成甲醇是碳的有效利用方式之一,将二氧化碳转化为重要燃料、化工产品甲醇,还可与电解水制氢结合,将产物甲醇作为氢气的储存载体。[方法]通过Aspen Plus模拟软件构建二氧化碳加氢催化制甲醇工艺模型,对于30万t/a的甲醇生产规模,考虑氢源来自电解水制氢,详细分析了温度、压力、二氧化碳/氢气进料比对甲醇产量的影响。[结果]模拟计算结果表明:合成温度为250℃,二氧化碳/氢气进料比为7.33时,甲醇产量最高;考虑直接与电解水过程结合,合成压力选取5 MPa是合理的;氢气的含水量对甲醇的产量有一定影响,原料氢气每增加100 kg/h的含水量,甲醇产量仅降低0.1%。[结论]通过模拟确定了二氧化碳加氢合成甲醇系统关键工艺参数的选取依据,证明了电解水得到的氢气不经过干燥、压缩处理,直接与甲醇合成工艺结合的可行性,新能源制氢耦合二氧化碳加氢合成甲醇工艺是具有应用前景的甲醇合成技术。

[Introduction]Carbon dioxide capture,utilization and storage is an important measure to achieve the goal of net zero greenhouse gas emission.The synthesis of methanol by carbon dioxide hydrogenation is one of the effective ways to use carbon,which can not only convert CO_(2) into methanol,an valuable fuel and chemical product,but also combine with producing hydrogen by electrolytic water,making methanol become the storage carrier of hydrogen.[Method]The methanol producing process by carbon dioxide hydrogenation was modelled by simulation software Aspen Plus.For the methanol production scale of 300,000 t/a,the hydrogen producing by water electrolysis was considered as the hydrogen source,and the influence of temperature,pressure and CO_(2)/H2 feed ratio on methanol yield was analyzed in detail.[Result]The simulation results show the methanol yield is the highest when the synthesis temperature is around 250°C and the CO_(2)/H2 feed ratio is 7.33.Considering the direct combination with water electrolysis process,the synthesis pressure at around 5 MPa is reasonable.The water content of hydrogen has a certain effect on the methanol yield.The methanol yield only reduces 0.1 percent with the water content increase 100 kg/h in the raw H2.[Conclusion]The simulation determined the selection basis of key process parameters of methanol synthesis system by carbon dioxide hydrogenation.In addition,the feasibility of directly combining H2 obtained from water electrolysis with methanol synthesis process without drying and compression treatment is proved.In conclusion,hydrogen production from renewable sources combined with methanol synthesis by carbon dioxide hydrogenation is a technology with application prospect.