煤火烧变岩区热量富集机理与热迁移特性

Subsurface fire is known as a worldwide disaster without geographical boundaries. The heat generated by the combustion of coal is mainly absorbed by the surrounding rock, which refers to the burnt rock with high temperature and large heat capacity. In the previous work, the thermal energy from the fire area is always treated as a source of disaster, resulting in a lot of heat loss. Therefore, it is of great practical significance to carry out thermal extraction and development, considering the extraction of thermal energy, fire prevention and cooling. Heat extraction cooling technology is based on seeking a desert area from thermal enrichment area of coal fire. The igneous rock is the main carrier of heat accumulation in coal fire area, and its thermal seepage is influenced by both matrix and fracture. Based on the thermo-physical parameters and prediction model of the burnt rock, this program explores the heat storage and desorption mechanism of the burnt coal and rock, and provides the basis for the thermal enrichment and heat transfer in the coal fire zones. The evolution of fractured field and the law of gas seepage in high temperature and large heat capacity rock are explained. The thermal effect of the flow-solid-thermal-chemical multi-field coupling in burnt rock zone from coalfield fires is revealed. The dynamic evolution mechanism of the "generation - enrichment - migration" of the heat in the burnt rock zone is understood. The criteria for delineation of "desert area" of coal fire resources is put forward. It is of great scientific significance to evaluate the potential of coal fire resources, the assessment of thermal quality and the development and utilization of geothermal energy through the research of the program.

地下煤火被称为没有地理界限的世界性灾难。煤火燃烧产生的热量主要被围岩吸收而形成高温、大热容量的烧变岩。以往火灾治理研究均是将火区热能视为一种灾害源，造成了大量热资源损失。因此，将煤火热能提取与灭火降温协同考虑，进行热能提取开发具有重要的现实意义。热量提取降温技术的基础是对煤火热资源“甜点区”的圈定。烧变岩作为煤火区热量集聚的主要载体，热力渗流来自于基质与裂隙两方面的影响。本项目基于烧变岩的热物性参数及预测模型，探索烧变煤岩的蓄热/释热机制，为煤火区热富集特性及热量传递提供基础；阐明高温大热容烧变岩区裂隙场演化与气体渗流规律，揭示煤火烧变岩区流-固-热-化多场耦合的热效应，掌握煤火烧变岩区热量的“产生-富集-迁移”全过程动态演化机制。提出煤火热资源“甜点区”的圈定准则，预期研究成果将对于煤火热资源开采潜力评价，热品质的评估及热能开发利用、灭火降温工程实施具有重要的科学意义。

地下煤火被称为没有地理界限的世界性灾难。煤火灾害治理的根本就是消除能量，降低烧变煤岩体温度。由于地下煤火从形成到燃烧耗时长，蕴藏着巨大的热能。但传统煤火治理方法，均是将火区的热能作为一种灾害源，治理时仅考虑如何移除火区热能而并未考虑热量的提取和利用，导致治理过程中火区蕴含的热能全部废弃。因此，将煤火热能提取与灭火降温协同考虑，进行热能提取开发具有重要的现实意义和科学价值。. 本项目通过理论分析、Frattini试验研究等多种手段对烧变岩的理化特性、火山灰活性及影响因素进行了深入的探究，揭示了烧变岩形成过程中的孔隙结构演化、矿物转化规律、致色机理，首次证实了烧变岩具备火山灰活性，且实验得出其活性与烧变岩种类、粒径相关。研究了高温热处理后岩体的孔隙形态分布规律，得出了高温热损伤具有开孔效应。通过实验和理论分析了烧变岩的热损伤机制及能量演化规律，得出了高温岩样力学突变的阈值温度。阐明了煤在不同供氧浓度下的低温氧化至在燃烧过程中4阶段的氧化动力学、温度、气体产物等特征参数的变化规律，提出CO/CO2浓度比值用以判定煤自燃风险、煤火演化状态以及煤火废弃热能品级的方法。采用地温梯度法、大地热流法等分析煤火燃烧体热异常水平、垂直分布规律，结合薄板差值，栅栏化修正热流数据，实现了煤火区废热资源量的计算；建立了基于传热传质及煤自燃的热动力学理论的煤田火区渗流及传热传质的多物理场耦合模型，基于新疆三道坝火区的工程模型，建立了煤火区“甜点区”热流密度模型。在传统煤火治理的基础上，提出了分布式煤火废热提取与热资源利用的方法，构建了超长重力热管技术高效提取煤火区热能系统，煤火区单孔最高发电功率达到了2.1kW，提取火区热能 181.6kW，标志着煤田火灾高品质废弃热能够得到有效回收利用，研究成果在新疆大泉湖、三道坝火区实现了规模化应用，社会、经济、环境、生态效益显著。