煤炭地下气化（UCG）技术作为一种环境友好的采煤方法，可被用来开发深部煤层与矿井遗留的煤炭资源。当地下气化时，随着气化时间的推移，煤炭在煤层内部“燃烧”逐渐形成气化炉，炉内温度最高可达1 200 ℃。从UCG过程中的放热反应出发，综述了热量来源、温度场的变化及其传热特征等，总结了研究温度场的重要手段。分析认为，UCG是一个复杂的温热动态变化过程，在此过程中氧化还原反应、吸热和放热的可逆反应同时进行，导致了气化炉的温度场及其传热机制的复杂性。研究气化过程传热机制的方法主要有物理模拟、试验监测、理论计算和数值模拟4种，各自具有不同的适应性。其中，物理模拟的可操控性强，但是难以解决地层接触关系导致的接触热阻误差；试验监测能真实反映温度场等的变化情况，但是实际操作的经济性差；理论计算通过对气化过程的拆分，从理论角度定性定量了UCG的温度场特征，但理论计算难以考虑到温度渗流等对温度的影响；数值模拟借助计算机进行温度场的多场耦合，综合考虑了渗流、变形、温度等对传热的影响，但多场的物理耦合计算难度较大，且煤层及岩石的热物理性质随温度变化会产生较大的差异，导致数值建模的计算难度增加，制约了数值模拟方法的应用。综上所述，现有的UCG温度场的研究手段难以真实反映出气化炉的传热特征，各种研究方法只能研究特定情况下的温度变化，难以与实际情况结合。因此，基于现场试验数据，结合大型物理模拟试验与数值模拟手段，开展多物理场之间的耦合机理研究是后续煤炭地下气化的主要研究方向。另外，岩石热物理性质在高温下的变化规律及其对温度场的影响作用，也将是值得重视的研究方向之一。

Underground coal gasification (UCG) technology, as an environmentally-friendly coal mining method, can be used to develop deep coal seams and coal resources left over from mines. At the time of underground gasification, as the gasification time passes, coal “burns” inside the coal seam to gradually form a gasification furnace, and the maximum temperature in the furnace can reach 1 200 ℃. Starting from the exothermic reaction in the UCG process, this paper summarized the heat source, the change of temperature field and its heat transfer characteristics, and summarized the important methods for studying the temperature field. It is believed that UCG is a complex process of dynamic changes in temperature and heat, during which the reversible reactions of oxidation-reduction reaction, endothermic and exothermic proceed simultaneously, resulting the complexity of the temperature field of the gasifier and its heat transfer mecha nism. There are four main methods for studying the heat transfer mechanism of the gasification process: physical simulation, experimental monitoring, theoretical calculation and numerical simulation, each with different adaptability. Among them, the physical simulation has strong maneuverability, but it is difficult to solve the contact thermal resistance error caused by the contact relationship between the formations; the experimental monitoring can truly reflect the changes in the temperature field, but the actual operation is not economical; the theoretical calculation passes the separation of the gasification process, qualitatively quantified the temperature field characteristics of UCG from a theoretical point of view, but theoretical calculations are difficult to consider the influence of temperature seepage on temperature; numerical simulation uses computers to conduct multi-field coupling of temperature fields, and comprehensively consider seepage, deformation, and temperature. However, the calculation of the physical coupling of multiple fields is too difficult, and the thermophysical properties of coal seams and rocks will vary greatly with temperature changes, which increases the computational difficulty of numerical modeling and restricts numerical simulation methods.In summary, the existing UCG temperature field research methods cannot truly reflect the heat transfer characteristics of the gasifier, and various research methods can only study temperature changes under specific conditions and are difficult to relate to actual conditions. Therefore, combining field test data andlarge-scale physical simulation experiments with numerical simulation methods to further develop the coupling mechanism research between multiple physical fields will be the main research direction of subsequent underground coal gasification. In addition, the changing law of rock thermophysical properties at high temperature and its influence on the temperature field will also be one of the research directions worthy of attention.

0 引言

1 UCG过程中热量来源及温度场分布

   1.1 热量来源

   1.2 温度场分布

2 围岩的温度变化

   2.1 物理模拟

   2.2 试验监测

   2.3 理论计算

   2.4 数值模拟

3 高温下岩石热力学特征

4 存在问题与发展趋势