Analysis of Wind-Hydrogen Coupling with Coal-to-Methanol System for Green Low-Carbon Methanol Synthesis

Coal to methanol (CTM) is the most important source of methanol in China. However, the traditional CTM process needs to produce hydrogen through the water-gas shift (WGS) unit, which results in high CO 2 emissions. In this study, a new coal-to-methanol process coupled with green hydrogen (CTM HPWE ) is proposed to reduce CO 2 emissions and improve energy efficiency. Compared with CTM process, the carbon utilization efficiency of CTM HPWE process is increased by 76.75%, and the energy consumption and CO 2 emissions are reduced by 15.87% and 56.61% respectively. In a grid-powered mode, in which the hydrogen production system is powered by grid, the influence of electricity price and carbon tax on methanol cost is studied. When the renewable electricity price drops to 0.2427 yuan/kWh (the lowest bidding price for photovoltaic in China, 2020), the methanol cost of CTM HPWE process will drop to 2565.75 yuan/t, equal to that of CTM process with medium level of carbon tax (240 yuan/tCO 2 ). In a wind-powered mode, in which the hydrogen production system is powered by self-built wind farm, through sizing optimization and dynamic operation management of wind-hydrogen system, the maximum wind power accommodation and stable methanol production are both realized under fluctuating wind power input. The economy of the optimized wind-hydrogen-methanol system is evaluated. The results shows that the methanol cost of CTM HPWE process is 2245.53 RMB/t, which is comparable with CTM process under the domestic carbon tax reference value (51 RMB/tCO 2 ). Our study provides a feasible technical route for the upstream renewable energy accommodation coupled with downstream stable green hydrogen supply in the future.