The environmental effect of underground coal gasification semi‐coke on confined groundwater

Abstract

From the health and environmental point of view, the control of soluble metal elements and organic compounds in underground coal gasification (UCG) by-product is of great importance for groundwater protection. Unlike the leaching of gasification ash as well as leaching in normal pressure, the leaching of trace elements and organics from UCG semicoke into confined groundwater has received little concern. In this research, UCG model test of Inner Mongolia lignite was performed, the obtained UCG semi-coke was then soaked by applying stainless steel leaching column at 0.5, 1.0, 1.5 and 2.0 MPa with nitrogen as pressurizing agent, the concentrations of trace element and total organic carbons (TOC values) in lixiviums were finally determined by applying ICP-MS and TOC analyzer to investigate the slight leaching in confined groundwater. The results indicate that Cd, Co, Cr, Ni, Pb and V are undetected in all lixivium samples, and compared with soaking under normal pressure, the concentrations of As, Ba, Mn and Sr are lower in confined water. TOC values in lixivium samples approximately approach to the background value of groundwater, indicating that no extra organic compounds could be leached and TOC values also show the similar changing trend as As, Ba, Mn and Sr behave under normal and high pressures.

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

“…Pollutants produced by UCG are similar to surface gasification beds. Inorganic pollutants mainly include hydrogen sulfide, ammonia, and harmful trace elements of heavy metals, while organic pollutants mainly include phenols, benzene, PAHs, heterocyclic compounds, etc. − In the experiment of simulating UCG, the simulated rock layer made of similar materials has a certain degree of adsorption. During gasification, the high-temperature coal gas will carry pollutants from the fissures into the surrounding rock layers and remain.…”

Characterization of the migration of organic contaminants in laboratory-scale groundwater polluted by underground coal gasification

“…Therefore, the transportation and fate of contaminants should be studied to control and limit the migration. There are so many kinds of contaminants produced in the process of UCG, it is impossible to study all of them at once in a work, and among those contaminants, the phenol is one of the most representative according many previous researches (Grabowski et al 2021, Ma et al 2021, Stuermer et al 1982, Xu et al 2016.…”