Research on the Pollutant Migration Law Based on Large-Scale Three-Dimensional Similar Simulation Experiments of Underground Coal Gasification

[Image: see text] The potential pollution risk of underground coal gasification (UCG) has become a key factor restricting the development of UCG industrialization. Therefore, studying the migration and diffusion behavior of harmful pollutants is of great significance for preventing UCG pollution. In this paper, a large-scale three-dimensional similar simulation experimental device for UCG is used to simulate the gasification of Tianjin fat coal under actual working conditions. The rock layer around the simulated coal seam was sampled after the gasification was completed, the contaminants in the samples were examined by XRD, and the changes in the relative content of the contaminants at different sampling points were studied by FTIR. The results showed that benzene, phenols, aldehydes, aromatic hydrocarbons, and aromatic heterocyclic compounds remained after the gasification of No. 7 sampling point in Qianjiang, Tianjin, and that the main pollutants were aromatic hydrocarbons. The migration and enrichment of phenol and aldehyde pollutants were about the same on the east and west sides of the gasification center, while benzene pollutants were more easily migrated and enriched than aromatic heterocyclic compounds. The migration distance of phenolic pollutants on the south side of the gasification area is smaller than that of other pollutants and their maximum vertical distance from the gasification reaction area to the south is about 0.7 m. The results can provide a scientific basis for pollutant risk identification and prevention and control in the later UCG field test.