Research progress on characteristic analysis and resource utilization of coal gasification slag
FAN Ning，ZHANG Yiqun，FAN Panpan，FAN Xiaoting， WANG Jie，WANG Jiancheng，DONG Lianping，FAN Minqiang，BAO Weiren
In China, the energy structure is characterized by rich coal, poor oil and less gas, and the development of coal chemical industry is full of opportunities and challenges. Coal gasification technology is the front-end process of modern coal chemical industry. It is an effective way to realize clean, efficient, green and low-carbon utilization of coal, and has important national strategic significance. However, the disposal of a large amount of solid waste (coal gasification slag) produced by the large-scale application of coal gasification technology is a pain point that coal chemical bases urgently need to solve. Starting from the particle size composition, mineral composition, micro morphology, surface properties, water holding properties and other physical and chemical properties of gasification ash of representative coal chemical industry bases in China, the characteristics of ash under different furnace types, different places of origin, different gasification processes and other conditions were compared, analyzed and summarized. The difference of physical properties of ash and slag is related to gasification process, furnace type, coal type and other factors. The main components of ash are silicon and aluminum minerals. The particle size of coarse slag is generally too large. The residual carbon content of fine slag is generally about 20%, and its surface is rich in oxygen-containing functional groups. In addition, the water content of fine slag is high due to its high porosity. Based on the physical and chemical properties of gasification ash, the reported methods for improving the quality of gasification slag were systematically summarized. It is proposed that carbon-ash separation is an important prerequisite for realizing the reduction and resource utilization of gasification slag. From the perspective of efficient recovery of micro fine minerals, flotation is the most suitable carbon-ash separation method. However, due to the developed pore structure of carbon residue and the existence of oxygen-containing hydrophilic groups, the floatability is poor, and the current production cost is high. From the point of reducing production cost and increasing treatment capacity, gravity separation method is the first choice, but there is a problem of higher separation size limit. Magnetic separation is more targeted for ash with high content of ferromagnetic minerals and is not generally applicable. Based on the characteristics of the above separation methods, the development of large-scale separation equipment, new high-efficiency flotation reagents and flotation methods, and high efficiency and low consumption combined separation process of gasification slag are the research focus in the follow-up field of carbon-ash separation. In addition, the research progress of resource utilization of gasification ash was systematically summarized. Application fields such as building materials can realize the large-scale consumption of gasified slag, which is the primary utilization direction to improve the comprehensive utilization rate of solid waste. It is necessary to further study the follow-up problems such as drying and dehydration of gasified slag and precipitation of heavy metals. In the fields of ecological restoration, boiler mixed combustion, carbon material preparation, adsorption/catalyst preparation, etc., the high-value utilization of gasification slag can be realized, and the market capacity should also be fully considered. Taking the downstream market as the guide, comprehensively considering the technical status, cost accounting, market consumption and other factors, and combined with the concept of efficient separation and quality utilization, it is an effective way to realize the resource utilization of gasification slag, where the enterprise benefits and environmental protection benefits can be achieved. At the same time, it is also an important supplement to realize the high-end, diversified and low-carbon development of coal chemical industry.
solid waste;coal gasification slag;flotation;gravity separation;resource utilization