This paper presents the application of a thermal-hydraulic-chemical model to simulate (1) a laboratory small-scale borehole combustion experiment using high-ash-content coal and (2) an ex-situ large-scale UCG experiment using low-moisture-content hard coal. The focus was to study temperature development, syngas composition, pore structure alteration of coal, and cavity growth pertinent to the UCG process. Both numerical simulations reproduced the temperature development trends along the gasification channel. Compared with the measured cavity with a horizontal length of 15 cm and a maximum vertical extension of 5.4 cm that was created in the 10-h-long borehole combustion experiment, a similar simulated cavity was formed in the first simulation, which had a horizontal length of 10 cm and a maximum vertical extension of 5.1–5.7 cm. This simulation indicated that the proposed model can be used to estimate the cavity growth with the process of UCG due to solid-gas conversion. In the second simulation, the simulated composition of syngas showed good agreement with the experimental results. It also revealed that fierce gasification and combustion mainly occurred close to the inlet, and thus created an L-shaped cavity in the 20-h-long UCG process. Moreover, the UCG process was distinctly divided into three stages from the perspective of solid loss and pore structure alteration at a representative node owing to thermal expansion, compressional shrinkage, pyrolysis, and gasification and combustion. The second stage of 3–11 h was the main period for combustion and gasification of the UCG process, namely, 70% of the solid mass was converted into syngas at temperatures above 1320 K, and the porosity increased linearly with time and the permeability showed exponential growth. Furthermore, a parametric sensitivity study based on the second simulation indicated that the simulated cavity growth of UCG was sensitive to the kinetics of char combustion, while the assumed pyrolyzed production ratios in the model were not of significance to the cavity growth during UCG. It is claimed that the coupled thermo-hydraulic-chemical model adopted in this paper provides novel insights into the UCG reactor's dynamic behavior, including solid-gas conversion and cavity growth.

本文介绍了热工水化学模型的应用，以模拟（1）使用高灰分煤的实验室小规模井眼燃烧实验，以及（2）使用低水分进行的非原位大规模UCG实验含量的硬煤。重点是研究温度的发展，合成气的组成，煤的孔隙结构的变化以及与UCG过程有关的空穴的增长。两种数值模拟都再现了沿气化通道的温度发展趋势。与在10小时的钻孔燃烧实验中所测量的水平长度为15 cm，最大垂直延伸为5.4 cm的空腔相比，在第一次模拟中形成了类似的模拟空腔，其水平长度为10厘米，最大垂直延伸范围为5.1-5.7厘米。该模拟表明，该模型可用于估算由于固-气转化而产生的UCG过程中的空腔生长。在第二次模拟中，模拟的合成气组成与实验结果显示出良好的一致性。它也表明激烈的气化和燃烧主要发生在入口附近，因此在长达20小时的UCG过程中形成了一个L形腔。此外，由于热膨胀，压缩收缩，热解以及气化和燃烧，从代表性节点处的固体损失和孔结构改变的角度来看，UCG过程被分为三个阶段。3-11小时的第二阶段是UCG工艺燃烧和气化的主要阶段，即70％的固体物质在高于1320 K的温度下转化为合成气，孔隙率随时间线性增加，渗透率呈指数增长。此外，基于第二次模拟的参数敏感性研究表明，模拟的UCG空腔生长对炭燃烧动力学很敏感，而模型中假定的热解生产率对UCG期间的空腔生长没有意义。据称，本文采用的热-水-化学耦合模型为UCG反应器的动态行为提供了新颖的见解，包括固体气体转化和空洞生长。而模型中假定的热解产率对UCG期间的空腔生长没有意义。据称，本文采用的热-水-化学耦合模型为UCG反应器的动态行为提供了新颖的见解，包括固体气体转化和空洞生长。而模型中假定的热解产率对UCG期间的空腔生长没有意义。据称，本文采用的热-水-化学耦合模型为UCG反应器的动态行为提供了新颖的见解，包括固体气体转化和空洞生长。