Distribution and enrichment of pollutants from underground gasification of bituminous coal in Huating Mining Area

In order to study the enrichment and distribution of pollutants from the underground gasification of bituminous coal in Huating Mining Area, and to evaluate the environmental factors of the underground gasification of bituminous coal, with an underground gasification simulation experimental platform system, this paper studies the enrichment of heavy metal pollutants in tar and gasification residues during gasification process by means of different oxygen-rich-water gasification experiments and pyrolysis experiments of coal samples in different sizes. The results show that the pyrolytic tar of bituminous coal tends to increase as its size increases, and the yield increases first and then decreases. When bituminous coal is pyrolysed in N₂ and CO₂, the main components of pyrolysis tar are phenols, naphthalenes and hydrocarbon pollutants. The concentrations of Ni, Cr, Zn, Cu and As after underground gasification are the highest in the oxidation zone, followed by the reduction zone and the dry distillation zone. And the enrichment of Hg is the highest in the oxidation zone, followed by the dry distillation zone and the reduction zone, while Pb is the most concentrated in the reduction zone, followed by the oxidation zone and the dry distillation zone. The residual degree of heavy metal elements from high to low is Zn, As, Hg, Cr, Ni, Cu and Pb. In Huating mining area, heavy metal elements Zn, As and Hg should be detected after gasification. In the later stage of production, combined with the characteristics of coal seams and groundwater, pollution prevention and control should be carried out in terms of project site selection and gasification process. Given the current severe situation of eco-environmental protection, the research results have certain guiding significance for the disposal and emission reduction of pollutants from underground coal gasification mining.