This paper presents an analysis of contaminants generated from large-scale, laboratory-based, underground coal gasification (UCG) experiments using a high-rank coal from the South Wales Coalfield. The experiments were performed at atmospheric and elevated pressures (30 bar) by varying the oxidants’ composition. The experiments were designed to predict the amount of produced water and contaminants generated at each stage of the operating conditions. The mass balance of water supplied and produced in the experiments was accounted for. Chemical analyses of produced water, char and ash contents were performed to quantify the inorganic and organic chemical parameters. Most of the contaminant concentrations in the produced water from the 30-bar pressure experiment were lower than the concentrations generated from the atmospheric pressure experiment. The measured concentrations of the inorganic chemical species and the inorganic parameters of the coal seam water from the South Wales Coalfield were used in theoretical calculations to predict the dominant equilibrium species concentrations in a hypothetical scenario of effluent contaminated groundwater. The biodegradation of organic contaminants such as phenol, benzene and sorbed fractions of inorganic contaminants from the produced water on iron oxide in the ash residue was predicted using existing biotransformation kinetics and surface complexation models, respectively. The biodegradation of phenol and benzene would be a slow process even at optimum conditions and the iron oxide left in the cavity can act as a sorbent for a few inorganic species. The evidence from the present study suggests future work towards (i) developing an appropriate water treatment process during gas cleaning, (ii) operational procedure (pressure and proportions of oxidant) and (iii) developing UCG-specific experimental prediction of contaminant transportation and transformation kinetics.

本文介绍了对使用南威尔士煤田的高级煤进行的大规模，基于实验室的地下煤气化（UCG）实验产生的污染物的分析。通过改变氧化剂的组成，在大气压和高压（30巴）下进行实验。设计这些实验是为了预测在操作条件的每个阶段产生的水和污染物的数量。考虑了在实验中供应和产生的水的质量平衡。对采出水，炭和灰分进行化学分析，以量化无机和有机化学参数。30 bar压力实验产生的水中大部分污染物浓度低于大气压实验产生的浓度。在理论计算中，使用了来自南威尔士煤田的测得的无机化学物质的浓度和煤层水的无机参数，在理论计算中预测了假设的污水污染地下水情景中的主要平衡物质浓度。分别利用现有的生物转化动力学和表面络合模型预测了灰渣中氧化铁上的有机污染物（如苯酚，苯）和无机污染物从采出水中在氧化铁上的吸附部分的生物降解。即使在最佳条件下，苯酚和苯的生物降解也将是一个缓慢的过程，并且残留在腔体中的氧化铁可以充当一些无机物的吸附剂。