Current situation of resource utilization of coal gasification slag and research progress of carbon-ash separation technology

Promoting clean and efficient utilization of coal is a major demand for accelerating China’s green and low-carbon energy transformation and realizing the national strategy of “carbon peaking and carbon neutrality”. Coal gasification is one of the important directions to realize clean and efficient utilization of coal, and coal gasification slag is the main solid waste generated in the process of coal gasification. At present, the treatment of coal gasification slag is mainly landfill storage, which causes waste of resources and environmental pollution. Therefore, it is urgent to carry out research on resource utilization of coal gasification slag to realize green consumption of bulk solid waste. The particle size distribution, phase composition and surface morphology of coal gasification slag are systematically introduced. According to the discharge method, gasification slag can be divided into coarse slag and fine slag. The former particle size is mostly 1−4 mm, and the fine slag is mostly less than 1 mm, and the particle size is generally −45 μm. The gasification slag mainly contains flocculent amorphous carbon residue and inorganic minerals mainly composed of SiO₂, Al₂O₃, CaO, etc. The two components symbiosis in the form of mutual dispersion, adhesion or fusion. The secondary utilization of carbon components is mainly achieved through cyclic blending, soil improvement and water restoration, and preparation of porous carbon materials. The utilization methods of ash components are mainly construction materials, production of silicon fertilizer raw materials, and preparation of high value-added composite materials. The development status of coal gasification slag carbon ash separation technology including screening, gravity separation and flotation is analyzed. Serious oxidation of carbon particles surface, developed pore structure, dense melting of carbon-ash and fine particle size are the main reasons for the difficulty in separating carbon-ash from coal gasification slag. In the future, further research can be carried out on how to reduce the adverse effects of particle size, pore size and surface hydrophilic characteristics on the flotation process. In order to realize the economical and efficient separation of carbon ash from fine slag of coal gasification and promote the resource utilization of coal gasification slag.