Carbon flow and energy flow analyses of a Lurgi coal-to-SNG process

Developing coal-to-SNG can alleviate the shortage of natural gas supply in China. In this paper, a commercial process of coal-to-SNG is modeled and simulated. Based on the simulation, the carbon flow and exergy flow of the coal-to-SNG process are analysed. The results show that the carbon element utilization efficiency is 35.7%. The unused carbon is almost discharged in the form of CO2. The acid gas removal unit and the power generation unit are the major emission units, which occupy 67.2% and 32.8% of the total carbon emission. By the exergy analysis, the results show that the major exergy destruction occurs in the power generation unit, followed by the coal gasification unit and the acid gas removal unit. Finally, several improvement methods are proposed to estimate energy saving and carbon emission reduction. The results show that the utilities consumption of the air separation unit, the coal gasification unit, the acid gas removal unit and the phenol recovery unit can be reduced by 29.8%, 85.7%, 17.9%, and 18.6%, respectively. The reduced utilities consumption would lead to decrease of the entire carbon emission by 19%.