【作者】 曾强；

【导师】 王德明；

【作者基本信息】 中国矿业大学 ， 安全技术及工程， 2012， 博士

【摘要】 煤火是伴生煤炭资源开发的一种灾害，在世界主要产煤国普遍存在。煤火不仅燃烧损失大量煤炭资源，还对区域环境产生严重影响。煤火燃烧系统热动力特性是煤火研究领域的核心内容，其研究旨在揭示煤火热动力演化过程，为煤火高效治理、科学定量评价煤火环境影响提供基础。本论文以新疆地区煤火为研究对象，较系统地从煤火赋存物理边界、火区持续燃烧供氧动力、火区煤燃烧放热特性与传热特性等方面开展了其燃烧系统热动力特性研究。应用岩层控制理论分析了火区空间的状态特性，提出了确定火区控制体物理空间边界的方法，初步构建了火区控制体模型。火区控制体地表范围以走向、倾向最外层裂隙为界，地下区域范围以走向、倾向岩层移动角、煤层赋存底板等高线推断。在火区控制体模型研究基础上，结合火区内孔隙介质透气率、裂隙介质透气率，提出了火区等效透气率计算模型。火区控制体内存在燃烧垮落空区、裂隙区域。燃烧垮落空区透气率符合孔隙介质透气率计算模型，裂隙区域透气率符合裂隙透气率计算模型，火区等效透气率是孔隙、裂隙透气率的有效组合。根据火区等效透气率理论计算模型，初步构建了火区等效透气率实验方法，可用于火区控制体围岩不同介质组合透气率的模拟测试。结合火区控制体模型，研究了火区控制体孔隙介质围岩导热率的计算方法。通过对火区烟气流动特性的研究，揭示了火区煤持续燃烧供氧动力-火风压的形成机制，提出了煤田火区火风压的计算方法与参数确定方法。火区控制体内烟气属自然对流条件迫使下的气体流动，其与火区环境大气间的温度差产生的重力差是引起烟气流动的主要动力。地面覆盖前后火区控制体内烟气流动状态不同，覆盖前空气流经火区控制体内状态变化基本符合等压过程，覆盖后烟气在火区控制体内状态变化基本符合等容过程。在此基础上提出采用火区状态系数C表征火区覆盖前后空气/烟气流动状态的变化，并设计了火区状态系数C的实验装置和试验方法。应用燃烧学理论对火区煤燃烧状态进行了分析，提出了火区控制体煤燃烧放热计算模型，即火区控制体热源强度模型。火区过量空气系数是反映煤燃烧状态的参数之一，实际火区多属于富燃料燃烧。由于煤火的复杂性，采用煤燃烧反应动力学研究方法描述火区控制体内煤燃烧状态具有一定局限性。对于整体火区燃烧系统热动力特性规律研究而言，可采用单位质量煤燃烧需氧量、放热量和火区烟气流量计算火区控制体煤燃烧放热量。应用传热学理论研究了火区与外部环境的热量传递方式，提出了煤火火源温度计算模型。煤火热量传递包括火区控制体内围岩导热、火区地表与环境大气的对流传热、火区地表的辐射传热以及火区烟气的传质传热。其中火区内以导热方式传向地面的热量以对流和辐射方式散失。火区地表与空气的对流传热符合外掠平板自然对流模型，对流传热系数根据空气流动雷诺数确定的流动状态计算。建立了火区控制体单位时间散热量和累积散热量计算模型。以典型火区1-水西沟火区和典型火区2-托洛盖05火区为例，进行了火区煤燃烧系统热动力特性部分参数的计算。结果表明地表辐射散热量普遍高于对流散热和传质散热。由建模及实例分析，在煤火治理中需要强调的治理原则：一是首先应考虑置换火区热量，尤其需要置换火区高温区域热量以快速降低火区内外温度差，及时减少火区供氧动力；二是对非高温区域裂隙及时进行覆盖封堵，增加空气渗入火区的阻力，及时降低火区供氧量。通过本论文研究，首次较系统地构建了煤火燃烧系统热动力特性基本模型，为揭示新疆地区煤火燃烧系统热动力演化的本质提供了定量分析手段。更多还原

【Abstract】 Coal fire is one of disasters associated with coal mining activities over the world.Coal fire not only consumes the coal resource for nothing, but also brings someserious problems to local environment, such as the pollution to air, the damage to soils,and the contamination to underground water and consequently the health problem tohuman beings. The thermal dynamic characteristic of coal combustion system for coalfire is the core of research in the coal fire field because of its important roles ofrevealing the mechanism of coal fire propagation and improving the coal fireextinction efficiency as well as scientifically evaluating the coal fire’s impact onenvironment. This dissertation focused on the modeling of the thermal dynamiccharacteristics of coal fires’ combustion system in Xinjiang region, including researchof the physical boundary of coal fire control volume, the dynamic of oxygen supply tocoal fire, the characteristics of heat generation from coal combustion under coal fireconditions, and the characteristics of heat transfer with coal fire and so forth. Theresults and conclusions have been obtained in this dissertation as follows.Coal fire burns in subsurface area. With the application of rocks control theory, amethod was proposed to determine the physical boundary of coal fire control volume,and a preliminary model of coal fire control volume has been established. Bothorientated and inclined boundaries of underground part of coal fire control volumecan be determined by using overlying rocks movement angle and contour map of coalseam deposit. The surface boundary of coal fire control volume can be determined bythe farthest faults/cracks along directions of the orientation and the inclination of coalfire. Based on the research of control volume of coal fire, and together with the use offluid theory within porous medium, the model of equivalent permeability (EP) of coalfire control volume was put forward firstly. Then, an experimental facility for EP wasdesigned, which it’s useful to study the EP with different mediums and differentcombinations of these mediums. As an important property of coal fire control volume,the overlying rocks’ thermal conductivity also was studied in this dissertation. Amethod was proposed to calculate it with an assumption of homogenous medium in alldirections for each rock layer.With analyzing the model of air/smoke flow of coal fire, a method of calculatingthe fire-heating air pressure (FAP) was proposed. It is known the air/smoke movesforced by the natural convection. The dynamic of its movement is the gravity difference between the fresh air and the hot smoke which is due to their temperaturedifference. It shows that the air/smoke state after covering is different from the onebefore covering. Before covering, the variety of air/smoke state within the fire zoneabides with constant volume process. After covering, it abides with constant pressureprocess. This dissertation also put forward a coal fire state coefficient C to indicate thechange of air/smoke state with the going on of extinction, and designed anexperimental facility for studying it.With the application of combustion theory, the state of coal combustion withinfire zone was analyzed at first. Then, a model of calculating the heat-generation fromcoal fire zone, i.e. the heat source model of coal fire, was proposed. Excess aircoefficient is one kind of parameter to indicate the coal combustion state within firezone. In fact, almost all coal fire is under conditions of rich combustible materialcombustion. For coal fire’s complication, it’s hard to describe coal combustion stateby using the kinetic theory of coal combustion. In order to study the thermal dynamiccharacteristics of any given whole coal fire, a heat source model, which is based onthe oxygen requirement and heat-generation for per kilogram coal combustion and theair/smoke flow amount, was established.Based on the theory of heat transfer, the style of heat transportation with coal firewas analyzed, and the model of calculating the fire source temperature was proposed.Heat transfer of coal fire includes the heat conductivity within fire zone, the heatdissipation by radiation from the surface of fire zone, and the heat dissipation byconvection as well as the heat taken away by mass transport. Plate natural convectionmodel can be used to describe the heat transfer by convection with coal fire. Theconvective coefficient can be determined by use the Reynolds number and otherparameters. Other two models also were proposed to calculate the heat dissipation andaccumulated heat dissipation.At the end of this dissertation, examples, i.e. the Shui-xi-gou coal fire and theNo.5fire zone of Tuo-luo-gai coal fire, were given to make calculation with parts ofabove proposed models. Results show that heat dissipation by radiation is greater thanother kinds of heat-transfer styles. From modeling of thermal dynamic characteristicsof coal combustion for coal fire and given example analysis, the principle of coal fireextinction will be emphasized again, i.e. heat-removing is an effective measurementto reduce the oxygen supply because it can reduce the coal fire zone’s temperaturequickly, another effective measurement is to cover faults/cracks located in lower temperature area of coal fire to increase the resistance for air leaking into the firezone.From the research, the basic models of describing coal fire thermal dynamiccharacteristics were established firstly. It will provide a quantitative method to revealthe essence of evolution of thermal dynamic characteristics of coal combustion forcoal fires in Xinjiang region.更多还原