Integration of Underground Coal Gasification and Carbon Capture, Utilization, and Storage: A Clean Energy Pathway to Carbon Neutrality

The "carbon neutrality" and "carbon peaking" objectives are propelling China's urgent energy structure transition toward renewable energy sources. As the dominant primary energy, coal must strike a balance between clean utilization and energy security. Notably, over half of China's medium−deep coal resources are unsuitable for conventional mine mining, making underground coal gasification (UCG) a pivotal technology for their development. This study addressed the critical challenges in UCG industrialization, namely the high storage and transportation costs of H₂ and the unclosed−loop treatment of CO₂ emissions. A novel coupling technical scheme was proposed, integrating three−stage underground coal gasification (UCG−Ⅲ) with near−well CO₂ hydrogenation to produce methanol. UCG−Ⅲ is a new generation of clean coal conversion technology, whose core lies in using CO₂ as both a product and a gasification agent, and achieving efficient utilization of coal and internal circulation of CO₂ through a three−stage process design. The gasification reaction pathway was optimized by this innovative approach to generate hydrogen−rich syngas, which is directly utilized for wellhead CO₂ catalytic conversion. Through this, simultaneous on−site hydrogen energy consumption and high−value utilization of carbon resources were achieved. Experimental and economic analyses demonstrated that storage and transportation costs were significantly reduced by 47% compared to traditional methods, and CO₂ emissions were lowered by up to 80% through underground CO₂ recycling. The dual value of coal as both an "energy service provider" and a "carbon−based material supplier" was validated in this study, paving the way for environmentally friendly and economically feasible clean coal utilization. Current challenges include enhancing the controllability of the three−stage gasification process and developing low−cost skid−mounted methanol conversion equipment. Future research will focus on optimizing process control via multi−physics field model coupling, developing efficient catalysts, and improving system integration to facilitate large−scale industrial application. This work provides a critical technological pathway for China's fossil energy transition toward carbon neutrality.