Optimal Design And Energy-saving Investigation Of The Triple CO₂ Feeds For Methanol Production System By Combining Steam And Dry Methane Reforming

Methanol is an important energy and chemical raw material.In recent years,the demand for methanol is increasing.The study of methanol synthesis process has important industrial application significance.There are many methods for methanol production,of which natural gas reforming is the most common.The process mainly includes synthesis gas preparation,methanol synthesis and distillation refining.Using natural gas as raw material to synthesize methanol,the hydrogen to carbon ratio of the synthetic gas is close to 3,which is 2.05 higher than that of the synthetic methanol.In order to improve the utilization rate of hydrogen,there are many kinds of methanol synthesis processes with carbon dioxide addition,such as carbon supplement process after methane steam reforming(SMR),carbon supplement process in front of SMR and carbon supplement process after methane steam reforming combined with carbon dioxide methane reforming(SMR-DMR).By comparing and analyzing different methanol synthesis processes,this paper proposed a methanol synthesis process with SMR-DMR and three carbon dioxide supplements in front of methane steam reformer,carbon dioxide methane reformer and recycle gas.On the basis of process simulation,multi-objective optimization and heat exchange network optimization design were carried out.According to the simulation calculation data,comparing the carbon supplement process before the SMR reformer,after the SMR reformer,and the SMR-DMR combined carbon supplement process,it was found that the three-carbon carbon dioxide methanol synthesis process could not only significantly reduce energy consumption and carbon dioxide emissions.In addition,the exergy analysis of the above-mentioned methanol processes showed that the triple adding carbon dioxide methanol synthesis process could greatly reduce the exergy loss.Based on the results of the exergy analysis,the heat exchange network was designed by using Aspen energy analyzer(AEA)software to recycle the heat in the process of methanol synthesis by the triple feeds carbon dioxide.The results showed that the energy required by the process after heat exchange was 50.8% less than that before heat exchange.Compared with the process before heat exchange,the system loss after heat exchange was reduced by 63.5%,and the total capital investment was 17.6%lower than that of the process before heat exchange.Multi-objective optimization,exergy analysis and heat exchange network were used to optimize the energy-saving design of methanol synthesis process with triple carbon dioxide feeds of this paper,which had certain theoretical guiding significance for the production of methanol.