Entire elevating temperature processes for green hydrogen coupled coal-to-methanol process: simulation and techno-economic evaluation

The development of the traditional coal-to-methanol process has been constrained due to its high carbon emissions and low energy efficiency. In this paper, the authors proposed an entire elevating temperature process in green hydrogen production for coal to methanol process (ETGH-CTM), where the elevated temperature alkaline water electrolysis and the elevated temperature pressure swing adsorption technology were integrated to replace the water gas shift unit and the Rectisol process. The traditional coal-to-methanol (T-CTM) and green hydrogen coupled with coal-to-methanol (GH-CTM) processes were also built and validated. Each process is compared and analyzed for two gasification methods. The carbon utilization efficiency, energy utilization efficiency and economic analysis are compared to explore the advantages of the elevated temperature process. The results show that compared to T-CTM, the energy utilization efficiency increases from 49.38 %∼51.73 % to 57.47 %∼57.64 % and 58.08 %∼ 58.58 % under GH-CTM and ETGH-CTM, respectively. The carbon utilization efficiency for pulverized coal gasification rises from 44.66 %∼45.73 % to 83.00 %∼89.92 % and 94.21 %∼ 96.10 % under GH-CTM and ETGH-CTM. For economic performance, using Internal Rate of Return as the evaluation metric. Cross-comparison of coal gasification routes reveals that pulverized coal and coal-water slurry configurations yield equivalent IRR values for GH-CTM (4.07 %) and ETGH-CTM (17.48 %) processes at threshold electricity prices of 0.342 CNY/kWh and 0.336 CNY/kWh respectively. Progressive reduction in green electricity pricing beyond these thresholds confers increasingly favorable economics to the ETGH-CTM pathway.