Multi-objective optimization and techno-economic analysis of CO2 utilization through direct synthesis of di-methyl ether plant

In this study, a multiobjective optimization problem (MOOP) with two objective functions (maximization of di-methyl-ether (DME) production rate and minimization of carbon dioxide release) was applied to the direct synthesis of DME from a natural gas-derived synthesis gas (syngas). Twelve degrees of freedom were considered. The MOOP results suggest that the process with a maximum DME production rate of 1686 kmol/hr releases 4788 kmol/hr CO2 while the CO2 release of the process with DME production rate of 1282 kmol/hr is 1761 kmol/hr. The higher the DME production rate, the lower net CO2 emission to the air, natural gas consumption, and energy consumption per kg of the DME produced. In addition, the process with a higher DME production rate has a higher carbon efficiency and power production from the produced steam. The annual profit criteria of the overall process were used as a posterior preference index to select the best point from the resultant multiobjective optimization Pareto front. It was shown that the plant with the topmost DME production rate has the utmost annual profit compared to other Pareto optimum points. Lastly, the effect of degrees of freedom on the maximum DME production rate is discussed.