【作者】 曹凯；

【导师】 王德明；

【作者基本信息】 中国矿业大学 ， 安全技术及工程， 2013， 博士

【摘要】 煤炭是我国的主要能源，煤炭开采面临煤自然发火的严重威胁。由于广泛采用综采放顶煤开采工艺和瓦斯抽采技术，造成了采空区遗煤多、漏风大，综放采空区成为自然发火的主要区域。综放采空区空间大、遗煤分布广、漏风复杂等特点导致自燃危险区域分布异常且缺乏深入研究，使得综放采空区遗煤自燃的防治工作存在很大的盲目性，时常导致自燃事故的发生。本文以分析采空区煤氧化自热环境为切入点，深入研究采空区贫氧条件下遗煤自燃氧化特性，通过建立符合现场实际的综放采空区及上覆岩三维空隙场数学模型和煤自然发火三维数学模型，揭示采空区遗煤自然发火规律，提出针对性较强的防治措施，提高防治综放采空区遗煤自燃的技术水平。综放采空区为半封闭空间，煤自燃氧化多在贫氧条件下进行。为了获得更加符合现场实际的煤自燃特性参数规律，奠定系统研究综放工作面采空区自然发火规律的实验基础，论文开展了贫氧条件下煤自燃特性研究。为了保证实验可靠和准确性，首次采用计算机智能动态稳定配气装置，实现对不同氧浓度N2-O2混合气体的高精度、动态稳定配制。在此基础上，利用差示扫描量热技术（C80微量热仪）和煤氧化过程特征参数多元测试装置实现准确定量分析不同氧浓度条件下耗氧、放热以及气体产物生成规律。研究表明，贫氧状态对煤耗氧和放热的影响较小，而对气体产物的影响稍大；煤自燃在300℃前存在缓慢放热和加速放热两个阶段，对不同氧浓度条件下煤样缓慢放热阶段和加速放热阶段的表观活化能进行了计算，表观活化能随氧浓度的降低而近似呈线性缓慢升高的趋势；变质程度低的煤对环境的贫氧程度敏感性强，氧浓度的变化对其自燃过程的耗氧、放热、气体产物以及交叉点温度特性的影响程度都普遍高于变质程度高的煤。总体来说，贫氧条件对综放采空区煤自燃特性的影响较大，以上实验研究为准确分析采空区自然发火规律奠定了基础。采空区与覆岩的空隙是遗煤自燃的漏风供氧、烟气和热量逸散的通道，是煤氧复合和蓄热升温的重要影响因素，决定着遗煤自燃环境的气体浓度场、流场和温度场分布。因此，研究采空区及覆岩的空隙率分布规律对掌握采空区遗煤自燃过程的热、质传递规律尤为重要。在现场观测和理论分析的基础上，本文在关键层挠曲方程基础上提出了覆岩倾向、走向比例耦合平面连续挠曲模型，基于该模型得出覆岩离层带裂隙场的“双驼峰”比例耦合空间曲面模型，同时根据基本顶下沉曲面及采空区倾向空隙率变化系数，并考虑重力对破碎岩体空隙率的影响，推导出冒落带空隙率连续变化曲面方程，从而形成了采空区及上覆岩的三维空隙场数学模型，并对该模型进行了验算，得出的结论与现场实测数据基本吻合，这为揭示综放采空区遗煤自然发火规律，定量模拟综放采空区自燃火源特性确定了重要参量。在以上理论分析、实验研究的基础上，开展了综放采空区自燃危险区域现场观测和数值模拟研究，得出了综放采空区自然发火规律，即：综放采空区存在“空间自燃三带”分布特征，随着距离底板高度的不断增加，高浓度氧气分布区域的范围不断减小。因此得出：紧邻工作面的采空区，上部浮煤自燃的可能性要大于底板处的浮煤；随着进入采空区深度的增加，底板处浮煤自燃的可能性逐渐升高，上部浮煤加快进入窒息带，自燃的可能性降低。针对综放采空区自燃危险区空间立体分布的特点，提出了大流量、高扩散的高效阻化泡沫技术。研制了适合井下狭小作业空间的新型大流量、风驱高效泡沫发生装置，构建了满足大流量稳定灌注的阻化泡沫防灭火系统，实现了对大空间采空区遗煤的“宏观立体覆盖和微观高效阻化”，并从宏观和微观角度分别分析了阻化泡沫的阻化效果及阻化机理。有效防治了综放采空区遗煤自然发火，解决了综放大空间采空区自燃隐蔽火源防治难题。更多还原

【Abstract】 Coal is the major sources of energy in our country, but the spontaneouscombustion of coal seriously threaten the mining safety. The fully mechanized cavingtechnology and gas discharge which are widely used in recent years caused moreresidual coal and air leaking in goaf. The fully mechanized caving face goaf is themain area of coal spontaneous combustion which is characterized by high goaf space,widely distributed residual coal and stereoscopic distribution of spontaneouscombustion risk area. The inadequate research related to the regularity of spontaneouscombustion in the stereoscopic goaf results in a lot of blindness in controlling it, evenleads to extraordinarily serious spontaneous combustion accidents. Regarding thespontaneous combustion environment in goaf as the starting point, this dissertationanalyzed the space characteristics of spontaneous combustion environment in the goaf,studied the spontaneous combustion oxidation characteristics of residual coal underlean oxygen conditions, revealed the regularity of spontaneous combustion of residualcoal in goaf that more consistent with the actual conditions, at the same time,proposed targeted prevention measures to improve the overall technical level of thecaving face.As a hemi-closure space, the oxidation process of coal spontaneous combustionin fully mechanized caving face goaf occurred in the oxygen-poor conditions. In orderto get characteristic parameters and oxidation law that was more in line with theactual situation of coal spontaneous combustion and so as to lay the experimentalfoundation for the systematic study the law of spontaneous combustion of coal, thepaper carried out the experimental study of the characteristic parameters of thespontaneous combustion of coal in oxygen-poor conditions. In order to ensure thereliability and accuracy of the experiment, the study for the first time used thecomputer intelligence dynamic volumetric device, to achieve high accuracy anddynamic stability preparation of the different oxygen concentration in the gas mixtureof N2-O2. On this basis, using Differential Scanning Calorimetry (C80microcalorimeter) and multivariate testing device used to test characteristics parameters ofoxidation process of coal, the paper accurately and quantitatively analyzed the oxygenconsumption, the law of heat release and the generating law of gas product underdifferent oxygen concentration conditions. Research derived that the effect degree of the oxygen-poor conditions on oxygen consumption and heat release is less thangaseous products of the coal sample, and the process of spontaneous combustionexists the slow and accelerated exothermic stages before300℃, moreover, theapparent activation energy of coal samples linearly and slowly increases with thereduction of the oxygen concentration. When analyzed from the metamorphic gradeof coal samples, it was discovered that the effect degree of the oxygen-poorconditions on oxygen consumption, heat release and gaseous products of coal that islow degree of metamorphism is more than coal that is high degree of metamorphism.Overall, the effect of the oxygen-poor conditions on coal spontaneous combustioncharacteristics in fully mechanized caving face goaf.The distribution model of fracture field in goaf and overlying strata is theair-leaking and oxygen supply channel of spontaneous combustion of residual coal,fugitive channel of flue gases and heat, and it is the important factor of the process ofcombined effects of coal and oxygen and heat storage, and determines the distributionof concentration field, flow field, as well as the temperature field, so researching thedistribution law of porosity in goaf and overlying strata is particularly important tomaster the transfer law of heat and mass in the process of spontaneous combustion.On the basis of field observations and theoretical analysis, the paper established themathematical model of the three-dimensional void field of goaf and overlying strata.The paper put forward the proportional coupling model of tendency and trend bend ofoverlying strata on the basis of flexure equation of critical layer. Trough this model,the "double hump" proportional coupling space model of the fractured field wasraised. Meanwhile, based on the sinking curved surface of basic top and the changecoefficient of porosity in goaf tendency, and considering the effect of gravity on theporosity of broken rock, the paper deduced the continuously varying surface equationof porosity in caving zone. In addition, the checking results of this model wereconsistent with field data. It provides important parameters to reveal the spontaneouscombustion law of residual coal and quantitatively simulate characteristics of thesource of fire in goaf.On the basis of the above theoretical analysis and experimental studies, fieldobservation and numerical simulation of the spontaneous combustion risk area in goafwere conducted, and the spontaneous combustion regularity in fully mechanizedcaving face goaf was obtained, i.e. there was "Stereoscopic Three Zone" exist in goaf,the area of high concentration oxygen constantly reduced with the increase of the distance to the floor. Therefore, near the face, the upper residual coal in the goaf waslikely to have higher possibility of spontaneous combustion than that of the floorresidual coal; with the gradual entering into the goaf, the spontaneous combustion riskof the floor residual coal gradually increased, the rate of the upper residual coal’sentering the choking area was accelerated, and this reduced the spontaneouscombustion risk of the upper residual coal.On the basis of revealing the regularity of spontaneous combustion of coal infully mechanized caving face goaf, according to the stereoscopic distribution of thespontaneous combustion risk area, the hydroxy-type inhibitive foam technology wasproposed for the first time and has been applied in Dafosi mine successfully. Theinhibition effect of the hydroxy-type inhibitor was investigated in the laboratory fromboth macroscopic and microscopic characterization. A new efficient foam generatorwith large flow that suitable for small space underground was developed. The macrostereoscopic coverage and microscopic efficient inhibition of the goaf with largespace were realized, and the risk of spontaneous combustion in goaf was effectivelyreduced. Thereby, the conundrum of the prevention of hidden fire source in goaf withlarge space was successfully resolved.更多还原