| As an important C1 resource,utilization of carbon dioxide into carbon-based chemicals plays an important role in reducing greenhouse gas emissions and alleviating energy shortages.As one of carbon-based chemicals,methanol is not only an efficient energy carrier,but also a bulk chemical and alternative fuel.The utilization of carbon dioxide resources to synthesize methanol fits the concept of“methanol economy”,and is also an effective greenhouse gas emission reduction program.In this paper,two typical carbon dioxide synthesis methanol processes,including direct method and indirect process,are selected as case studies;the key units of the process and the basic analysis model of the overall process are established;the thermal integration design of the two processes and the technical-economic analysis are presented.The results show that the effective utilization rate of carbon element in direct process and indirect process is 96.50%and 99.10%,respectively.Process heat duty per unit product of the indirect method is about 54.38%lower than that of the direct process.The FCI of the direct process and the indirect process are 806.02CNY/t MeOH/y and 1518.38 CNY/t MeOH/y,and the product costs of the two processes are 5201.30 CNY/t MeOH and 5309.23 CNY/t MeOH,respectively.Through further investigation of the relationship between electricity price and methanol cost,when the electricity price will be as low as 0.1 CNY/kwh,the product cost of direct process and indirect process will be 1552.20 CNY/t MeOH and 1618.18 CNY/t MeOH,respectively.In order to solve the problem of ineffective utilization of low-grade waste heat in the five-tower multi-effect methanol rectification process the problem,this paper proposes a heat pump coupled multi-effect methanol novel process,which combines the advantages of heat pump assisted distillation and multi-effect distillation.Based on the whole process simulation data,the rationality of the heat pump setting is analyzed through pinch technology,and the energy consumption,the coefficient of performance（COP）and total annual cost（TAC）is used to evaluate the process performance.The results show that the heat pump setting is reasonable in the novel methanol distillation process.The condenser duty and the total reboiler duty are respectively 24.7 MW and 22.25 MW,and the COP is 22.5.The condenser duty,heat duty and TAC are respectively reduced by 33.76%,32.64%and 26.97%compared with the five-column multi-effect distillation process.The energy saving effect is significant for the novel methanol distillation process combining heat pump and multi-effect process.Aiming at the large amount of carbon dioxide produced by the CCS process in the coal-to-methanol process,this research proposes the green hydrogen integrated coal-to-methanol process.Based on the modeling parameters of the key units and the simulation results of the whole process,the green hydrogen integrated coal-to-methanol process is evaluated and analyzed.The results show that the integrated process produce a total of 517.01 t/h of methanol product with a purity of99.9 wt.%,which is higher than that of coal.The methanol output of the methanol production process is 124.67%higher.The energy efficiency of the integrated process is 51.90%,while the energy efficiency of the coal-to-methanol process is 46.96%.The carbon dioxide emissions of the integrated process are 85.64%lower than the carbon dioxide emissions of the coal-to-methanol process.The cost of integrated process products is 23.95%lower than that of coal-to-methanol process products,and the payback period of integrated process investment（2.8 years）is lower than that of coal-to-methanol（7.2 years）.This work aims to provide a feasible low-carbon and clean method to use coal resources. |
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