煤炭在我国的能源消费结构中占据重要地位，传统机械开采模式所带来的安全、环境和成本问题严重制约了煤炭的绿色高效开发利用。煤炭热解作为一种煤炭清洁开发的颠覆性技术，能够在增加煤炭开发利用率的同时最大限度降低开采过程对环境的影响，因此，煤炭热解逐渐成为保障我国能源安全的必要选择。

本文综合利用理论研究、室内试验、物理模型、数值模拟和综合分析等方法开展了研究工作，分析了富油煤热解过程中煤体的热物理性质、孔隙结构、热解动力学和热声发射特征及响应规律，揭示了富油煤的热损伤机制，利用物理模型和离散元数值分析法研究了热解过程中覆岩温度场、应力场和裂隙发育演化规律，取得成果如下：

（1）基于激光闪射法热物性测试技术，分析了富油煤热物理性质参数的演化特征，揭示了富油煤热物性对温度的响应机制。煤样在30～300°C的实时加热过程中，热扩散率的减小速率不断降低，比热容和热导率与实时温度均呈正相关。实时温度在210~240°C之间时，煤样中束缚水快速消散，比热容和热导率表现出明显的阶段性特征，特征阈值前后随实时温度的变化规律基本一致。热解后煤样的热扩散率随热解温度而降低，比热容随之增加，热导率整体降低。修正后的热物性归一化特征符合多项式模型。

（2）根据氢谱核磁共振T₂谱和T₁-T₂谱结果，研究了孔隙结构特征和含氢物质分布等参数的热响应规律，揭示了不同含氢物质对热解温度的响应机制。一维NMR试验T₂谱结果表明，随着热解温度增加，饱和试样孔隙尺度增加，孔隙间连通性增强，中孔体积比不断减小，大孔体积比呈先减小后增大趋势。当温度为350℃时，大孔体积比最小，而裂隙体积比达到最大值。二维NMR试验T₁-T₂谱结果表明，饱和后试样T₁-T₂信号峰数量随热解温度升高而减少，表明孔隙连通性和孔隙分选性增强。有机孔束缚水、无机孔束缚水和自由水沿T₁/T₂=1依次向右上方分布，T₁/T₂值范围分别为1~42、1~8和1~5。含氢基质T₁/T₂值分布范围明显大于有机孔油或轻烃类。在350℃时饱和热解煤中含氢基质、有机孔油或轻烃类物质和自由水等物质含量达到最大。

（3）基于声发射技术，分析了富油煤热解过程中热声发射特征的演化规律，揭示了富油煤热解过程热损伤机制，构建了富油煤热解多级裂纹发育模型。结果表明，室温~350℃主要发生干燥脱吸和弱键断裂；350~600℃热解反应活泼，焦油和气体产物的生成量分别在450℃和550℃时达到峰值，气态热解产物排出和矿物颗粒不均匀热膨胀导致的热损伤是产生声发射信号的主要原因，形成的裂纹信号在350~400℃最密集；600~1200℃主要以半焦的缩聚反应为主。随着升温速率增大，煤样热解过程中的热滞后效应更加显著。结合b值变化可以判断裂纹尺度随热解温度的变化规律。热解过程中富油煤的裂纹发育可分为四个阶段：200℃以下主裂纹发育形成主裂纹网，200~350℃主裂纹横向扩展，次级裂纹发育，350~450℃次级裂纹加速发育，450~600℃裂纹网加密，出现龟裂状裂隙。

（4）利用搭建的煤炭地下开采物理模拟试验系统开展了煤炭地下热解物理模型试验，建立了颗粒流离散元数值模型，模拟研究了热-力耦合作用下温度场和应力场对裂隙发育演化的影响机制。随着试验进程推进，各地层水平温度场趋向成为高温中心温度场；竖直温度场由中间温度低，两侧温度高，逐渐发展为中部温度高于两侧的对称分布特征。同一地层中下部裂隙发育程度明显较高。泥岩层中部可见水平和竖直贯通裂隙，破碎岩块较大，两侧岩体破碎程度明显高于中间部分，可见较平整离层面。温度、覆岩质量和地层埋深均对裂隙发育具有显著促进影响。煤及覆岩裂隙的发育由应力集中引起，当宏观裂隙产生后相应位置的应力得到明显释放。

Coal plays an important role in energy consumption structure of our country. The safety, environment and cost problems brought by traditional mechanical mining modes seriously restrict the green efficient development and utilization of coal. Coal pyrolysis, as a disruptive technology for clean coal development, can increase the utilization rate of coal development while minimizing the environmental impact of the mining process. Therefore, coal pyrolysis is gradually becoming a necessary choice to ensure energy security in China.

In this paper, theoretical research, laboratory test, physical model, numerical simulation and comprehensive analysis are comprehensively used to carry out research work. The thermophysical properties, pore structure, pyrolysis kinetics, thermoacoustic emission characteristics and response laws of middling coal body in the process of oil-rich coal pyrolysis are analyzed. The thermal damage mechanism of coal petrography is revealed. The temperature field of overburden rock during pyrolysis is studied by physical model and discrete element numerical analysis method The stress field and the evolution law of crack development have achieved the following results:

(1) Based on the thermal property testing technique of laser flash method, the evolution characteristics of thermal physical property parameters of oil-rich coal were analyzed, and the response mechanism of thermal physical property to temperature was explained. During the real-time heating of coal samples from 30 to 300 °C, the reduction rate of thermal diffusivity decreased continuously, and the specific heat capacity and thermal conductivity were positively correlated with temperature. When the temperature is between 210 °C and 240 °C, the structural water in the coal sample quickly dissipates, and the specific heat capacity and thermal conductivity showed obvious stage characteristics, the change laws before and after the characteristic threshold with the real-time temperature were basically the same. The modified normalized characteristics of the thermal properties are consistent with the polynomial model.

(2) Based on the results of NMR T₂ spectra and T₁-T₂ spectra of hydrogen spectra, the thermal response patterns of parameters such as pore structure characteristics and distribution of hydrogen-containing materials were investigated, and the response mechanisms of different hydrogen-containing materials to pyrolysis temperatures were revealed. The results of T₂ spectra of one-dimensional NMR tests showed that with the increase of pyrolysis temperature, the pore scale of saturated specimens increased, the inter-pore connectivity was enhanced, the mesopore volume ratio kept decreasing, and the macropore volume ratio showed a trend of first decreasing and then increasing. When the temperature was 350 ℃, the macropore volume ratio was the smallest, while the fracture volume ratio reached the maximum. The results of the T₁-T₂ spectra of the two-dimensional NMR tests showed that the number of T₁-T₂ signal peaks of the saturated specimens decreased with increasing pyrolysis temperature, indicating enhanced pore connectivity and pore sorting. The organic pore-bound water, inorganic pore-bound water and free water were distributed along T₁/T₂=1 in order to the upper right, with T₁/T₂ values ranging from 1 to 42, 1 to 8 and 1 to 5, respectively. The distribution range of T₁/T₂ values of hydrogen-containing matrix is significantly larger than that of organic pore oil or light hydrocarbons. The content of hydrogen-containing matrix, organic pore oil or light hydrocarbon substances and free water in saturated pyrolysis coal reached the maximum at 350 °C.

(3) Based on the acoustic emission technique, the evolution law of thermoacoustic emission characteristics in the pyrolysis process of oil-rich coal was analyzed, the thermal damage mechanism in the pyrolysis process of oil-rich coal was explained, and a multi-stage crack development model of oil-rich coal pyrolysis was constructed. The results showed that dry desorption and weak bond breaking occurred mainly at room temperature ~350 °C; The pyrolysis reaction was active from 350 to 600 °C, and the production of tar and gaseous products reached the peak at 450 °C and 550°C, respectively. Thermal damage caused by the discharge of gaseous pyrolysis products and uneven thermal expansion of mineral particles were the main reasons for the generation of acoustic emission signals, and the crack signals formed were most intensive at 350 ~ 400 °C; The polycondensation of semi-coke was mainly dominated from 600 to 1200 °C. With the increase of the heating rate, the thermal hysteresis effect in the pyrolysis process of coal samples was more significant. The variation pattern of crack scale with pyrolysis temperature can be judged by combining the change of b value. The crack development of oil-rich coal during pyrolysis can be divided into four stages: below 200 °C the main cracks developed to form the main crack network, 200 ~ 350 °C the main cracks expanded laterally and the secondary cracks developed, 350 ~ 450 °C the secondary cracks accelerated, 450 ~ 600 °C the crack network encrypted and the crack-like texture appeared.

(4) The physical model test of coal underground pyrolysis was carried out by the designed physical simulation test system of coal underground mining, and the discrete element numerical model of particle flow was established to simulate the influence mechanism of thermal-mechanical coupling effect of thermal and mechanical fields on the fracture development and evolution. As the experiment progressed, the horizontal temperature field of each stratum tended to become the high-temperature central temperature field. The vertical temperature field gradually developed into a symmetrical distribution with the temperature in the middle being lower and the temperature on both sides being higher. The degree of fracture development was obviously higher in the middle and lower part of the same stratum. Horizontal and vertical through fissures can be seen in the middle of the mudstone layer, and the broken rock pieces are larger, and the rock fragmentation on both sides was obviously higher than that in the middle part, and the smooth departure level can be seen. Temperature, overburden quality and rock burial depth all had significant promoting effects on fracture development. The development of coal and overburden fractures was caused by stress concentration, and the stresses at the corresponding locations were significantly released when macroscopic fractures were created.