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

Abstract

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.

Effects of Pressurized Pyrolysis on the Chemical and Porous Structure Evolution of Coal Core during Deep Underground Coal Gasification

“…Besides, the moisture content, volatile content, and ash content of raw coal samples also affect the development of the coal coke pore structure. Among them, the evaporation of water in the raw coal during pyrolysis plays a leading role . In addition, the degreasing of macromolecular structures during coal pyrolysis plays an important role in the growth of micropores …”

“…Among them, the evaporation of water in the raw coal during pyrolysis plays a leading role. 21 In addition, the degreasing of macromolecular structures during coal pyrolysis plays an important role in the growth of micropores. 42 3.4.2.…”

“…Therefore, the UCG technology is extremely promising for deep coal mining. As an important supplementary technique for coal mining and utilization, UCG technology has, in recent years, been developed and advanced widely. , Pyrolysis gas is an important component of the UCG gas product. In addition, the semicoke produced by pyrolysis is the raw material for gasification and combustion.…”