A novel coating technology for fast sealing of air leakage in underground coal mines

Air leakage in underground coal mines presents a serious hazard for coal production and the safety of miners. Coating technology is commonly used as an efficient means for preventing air leakage. To address existing problems with high dust concentrations in large operations involving complex processes and the high cost of traditional coating technology, a novel coating technology that ensures intrinsic safety by utilizing water pressure and wind pressure was developed. This new coating technology was designed to suction and spray, and the technical parameters of its spray performance was also studied. The experimental tests and evaluation indicated the optimum working range is 0.3–0.7 MPa of wind pressure,1.2–10.2 L/min of water quantity, and 1.0–3.5 m of spraying distance. Moreover, this novel coating technology was tested in the Dashuitou Coal Mine in Gansu Province of China. Compared with conventional counterparts, the proposed new technology is safe, efficient, and convenient to operate. During spraying,dust concentrations were kept at less than 10 mg/m3, and the average rebound ratio resilient rate of solid materials was below 13%. After spraying, the average leakage every 100 m was 4 m3/min, and the oxygen volume fraction in the adjacent goaf was approximately 4%, demonstrating excellent air leakage prevention.     

三相泡沫对综放面采空区漏风的影响规律

为研究综放面上隅角埋管注三相泡沫时采空区漏风风流的变化规律,采用FLUENT软件进行模拟分析.模拟结果表明,当综放面倾角分别为0°,10°,30°时,三相泡沫在采空区沿工作面倾斜方向的扩散范围分别达到20～30,50～100,100～150m,大大地减少了采空区的漏风风量;同时,采空区氧化带带宽分别缩减为10～20,10～15,5～10m,模拟结果表明三相泡沫能有效地防治采空区的煤炭自燃.以新集二矿1606工作面为例,注三相泡沫后,采空区氧化带带宽由60m缩减为15m以内,漏风风量由原来的约200m3/min减少到约25m3/min,以此为依据制定的防灭火方案取得了很好的效果,表明了模拟结果跟现场实际基本吻合.     

Risk assessment of gas control and spontaneous combustion of coal under gas drainage of an upper tunnel

The adjustment of the gas drainage rate has an immediate impact on air leakage in gob, thus resulting in the change of self-heating of coal. While regulating the gas drainage parameters, the risk of spontaneous combustion of coal should be considered. The risk assessment of gas control and spontaneous combustion of coal under gas drainage in a tunnel was investigated at different gas drainage rates. The distributions of the air volume along the working face, the gas management effects and the width of the oxidation zone were subjected to risk analysis. As the simulation results showed, with increasing gas drainage rate,although the safety of gas dilution by ventilation was assured, the intensifying air leakage caused the oxidation zone to move into the deeper gob and led to an increase in the width of the oxidation zone.A risk assessment method was proposed to determine a suitable gas drainage rate for the upper tunnel.The correctness of the risk assessment and the validity of the numerical modelling were confirmed by the field measurements.     

Bulking factor of the strata overlying the gob and a three-dimensional numerical simulation of the air leakage flow field

The present study examines the results of the researches related to the gob bulking factor carried out at home and abroad. A mathematical function of a three-dimensional gob bulking factor is described based on a three-dimensional gob model. The method of taking value for interstice and permeability ratios is also proposed. The law of air leakage of fully mechanized top coal is researched in this study. The results show that the speed of air flow near the upper and lower crossheadings is higher than that in the central section of the gob at the same distance from the working face. When the amount of air at the working face exceeds a critical amount, the width of the spontaneous combustion zone in the upper and lower crossheadings is also larger than that in the central section. In this situation, the key is preventing the coal left in the upper and lower crossheadings from self-igniting. Reducing the amount of air at the working face can decrease the width of the spontaneous combustion zone, especially the width near the upper and lower crossheadings. This also moves the spontaneous combustion zone in the direction of the working face. It can prevent the coal in the gob from self-igniting by making the coal left in the crossheadings to be inert and by effectively controlling the amount of air at the working face.     

煤粉空气流在管内着火规律的研究

本文介绍一管内煤粉气流着火的试验方法与理论模型，从而得出煤粉气流着火的一些特性与规律，由于管内煤粉气流着火更接近工程实际，因此该实验方法比其它一些研究着火规律的方法有更多的优点，同时介绍了几种典型工业用煤在控制煤粉浓度、气流速度以及管壁温度时，管内煤粉气流的着火特性的试验结果，并与理论模型的计算结果进行了比较．比较表明，理论模型计算结果与实验结果相符．     

综采面邻空煤柱漏风微循环现象研究

针对综采面"采场-邻空煤柱-采空区"间的漏风微循环现象,利用MATLAB中的PDE工具进行二维非线性渗流的数值模拟,同时分析研究漏风微循环现象形成的原因,以及漏风微循环对煤炭自燃的影响。研究表明,"采场-邻空煤柱-采空区"间的漏风微循环可以导致采空区内相对压力和气体成分的周期性变化,即"采空区喘息"现象。     

Method for prevention and control of spontaneous combustion of coal seam and its application in mining field

Spontaneous combustion of coal seam has been and continues to be a big problem in coal mines. It could pose great threat to the safety of the whole mine and all miners, especially when it occurs in or nearby coal mines. Besides, environment of area surrounded mines during combustion can be threatened where large amount of toxic gases including CO_2, CO, SO_2 and H_2S can be leased by fire in mine. Hence, it is important and significant for scholars to study the controlling and preventing of the coal seam fire. In this paper, the complicated reasons for the occurrence and development of spontaneous combustion in coal seam are analysed and different models under various air leakage situations are built as well. Based on the model and approximately calculation, the difficulty of fire extinguishment in coal seam is pointed out as the difficulty and poor effect to remove the large amount of heat released. Detailed measurements about backfilling and case analyses are also provided on the basis of the recent ten years' practice of controlling spontaneous combustion in coal seams in China. A technical fire prevention and control method has been concluded as five steps including detection, prevention, sealing, injection and pressure adjustment. However, various backfill materials require different application and environmental factors, so in this paper, analyses and discussion about the effect and engineering application of prevention of spontaneous combustion are provided according to different backfilling technologies and methods. Once the aforementioned fire prevention can be widely applied and regulated in mines, green mining will be achievable concerning mine fire prevention and control.     

超超临界汽轮机汽封漏汽流动特性的数值模拟研究

利用ANSYS软件对梳齿型、侧齿型和蜂窝型汽封的内部气体流动特性进行数值模拟分析,其结果表明:在相同的特征尺寸和边界条件下,梳齿型汽封出口压力最高,蜂窝型汽封出口压力最低。在梳齿型汽封中,气流在汽封齿与凸台之间形成的蒸汽室内将产生漩涡;侧齿汽封由于增加了侧齿,产生的漩涡强度将增大;蜂窝汽封在每个小蜂窝中将产生漩涡,漩涡强度最小,节流效果最明显。蜂窝式汽封的漏汽量最小,梳齿型汽封漏汽量最大。当出口压力相同、入口压力不同时,随着入口压力的增加,3种汽封的漏汽量也随之增加;当出、入口压力相同时,随着汽封段长度的增加,3种汽封的漏汽量均减小。     

相关分析法管道漏点定位系统的试验研究

针对管道漏点定位问题,研制出了一套基于快速傅立叶变换的相关分析法管道泄漏点定位系统.采用水声传感器捕获泄漏点水声信号;并对信号进行放大、带通滤波处理;应用LabVIEW语言进行计算机编程以实现水声信号的数据采集;引入了离散快速傅立叶算法,求解水声信号的互相关函数;进行了多种泄漏点定位检测试验;对试验结果进行了比较分析;结果表明了该系统应用于实际的可行性.     

简放工作面供风量与采空区遗煤自燃危险性研究

针对地方煤矿易自燃厚煤层简易放顶煤开采推进速度低的现实条件,本文在分析不同氧浓度条件下煤的耗氧速度、采空区煤氧化自燃三带及其与采空区漏风量关系基础上,研究了工作面供风量与漏风量及其采空区氧化带宽度的关系,研究结果为厚煤层简放开采工作面的合理供风量及防治煤炭自燃措施应用提供了技术依据.     

煤粉燃烧燃料氮析出研究进展

介绍了煤中氮元素的存在形态及NOX的形成机理，挥发分氮及焦氮在燃烧过程中的形成规律及分配比例。综述了国内外对煤热解、燃烧过程中燃料氮的热转化以及混煤氮的动态析出特性的研究方向、方法、结论以及有待解决的问题。讨论了煤质特性与运行参数对燃料氮在热解及燃烧产物中赋存形态的影响，指出了氮析出研究的发展趋势及研究方法，为实现煤的洁净利用、氮析出的试验研究提供借鉴作用。     

注氮惰化窒息燃烧煤炭氧浓度的实验研究

利用煤炭自燃实验系统,对龙固煤矿7煤煤样的自燃过程进行了模拟实验.实验研究了注氮情况下的煤氧化煤温、自燃状态与氧含量的变化关系,确定了龙固煤矿7煤煤样窒息的最低氧浓度,研究结果对使用注氮防治煤炭自燃技术的应用具有重要的现实指导意义.     

Numerical simulation of excess-enthalpy combustion flame propagation of coal mine methane in ceramic foam

Based on the assumption of a local non-equilibrium of heat transfer between a solid matrix and gas,a mathematic model of coal mine methane combustion in a porous medium was established,as well the solid-gas boundary conditions.We simulated numerically the flame propagation characteristics.The results show that the flame velocity in ceramic foam is higher than that of free laminar flows;the maximum flame velocity depends on the combined effects of a radiation extinction coefficient and convection heat transfer in ceramic foam and rises with an increase in the chemical equivalent ratio.The radiation extinction coefficient cannot be used alone to determine the heat regeneration effects in the design of ceramic foam burners.     

不同褐煤在O_2/CO_2条件下燃烧特性的实验研究

利用热重分析仪,系统地研究了霍林河褐煤、印尼1#褐煤和印尼2#褐煤在空气和O2/CO2条件下的燃烧特性,比较了不同褐煤样品在燃烧过程中失重与温度和时间的关系.实验结果表明,褐煤在O2/CO2条件下的燃烧特性与空气条件下的燃烧特性存在明显的区别,富氧燃烧条件下CO2分压力的大小影响褐煤的反应活性.     

A study of fire propagation in coal seam with numerical simulation of heat transfer and chemical reaction rate in mining field

Spontaneous combustion of coal is a problem that affects the mining operation and generates environmental, economic, social and geotechnical impacts. This phenomenon has been divided into two processes: ignition and propagation. Fire propagation develops in coal seams because of a set of factors such as direction and wind speed, fracturing and temperature. In this work, heat transfer and chemical kinetics are studied from conservation equations of energy and species, respectively, using the software COMSOL Multiphysics to simulate the propagation of fires in coal seams. Two possible scenarios were analyzed that usually occur in the walls of the coal seams, such as fire focus and fire complete screens. It was found that the propagation kinetics of the fire changes depending on the temperature, the fracturing of rock mass and the area of fire influence. For temperature values lower than 300 °C, there is consumption around 250 cm³/h, values around 700 °C, the consumption is 1500 cm³/h, and for fires of 1200 °C have values of 3000 cm³/h. Depending on the speed of propagation can vary from 4 to 17 cm/day, considering on the level and fracturing of the final wall of the open pit.     

煤粉分级燃烧对炉内燃烧过程影响的试验研究

为了考察炉内燃烧过程的变化特性，研究了2.11 MW四角喷燃煤粉炉的煤粉分级燃烧效果.试验采用的锅炉燃料分级百分比为20%，二级燃烧区过量空气系数取0.95.一级燃烧区和燃尽区过量空气系数取1.10.结果表明, 与未进行分级燃烧的基础工况相比，煤粉分级燃烧试验炉二级燃烧区和炉膛出口温度增高，锅炉NOx排放体积比降低45%. CO、CO2和SO2在应用分级燃烧后的炉内变化复杂，但其排放体积比未发生较大改变，甚至略有下降. 分级燃烧使锅炉固体不完全燃烧损失(SICL)有一定程度增加, 该煤粉分级燃烧是一种清洁燃烧技术.     

高炉喷吹煤粉的理论研究

给出了置换比与煤粉燃烧率之间的定量关系式,以高炉所允许的最低煤粉燃烧率ηｍｉｎ为依据,明确地提出了最佳喷吹位置（氧煤燃烧器的位置）在具体的生产条件下高炉所允许的最高煤比和最佳煤比的概念,对各种型式的氧煤燃烧器进行了比较,认为双枪螺旋式氧煤燃烧器和同轴双螺旋式氧煤枪优于其它类型的氧煤枪。     

煤矿井下无火花截割机的研制

煤矿井下地质复杂 ,条件恶劣 ,常有事故和故障发生 .当紧急排除故障时 ,需要对被堵地段进行疏通和清理 ,为此 ,研制了一种无火花截割机进行快速疏通 ,该机的主机部分为经过优化设计的曲柄摇块机构 .经井下试验表明 :该机设计合理、简单实用 ,是煤矿井下尽快排除故障或打开一条救生通道时可选用的一种先进设备     

堤坝渗漏广义示踪法室内试验研究

以堤坝填筑材料中常见细砂、中砂、粗砂为试验材料,以食盐溶液为示踪剂,通过测试各材料中示踪剂电导率随时间的变化规律,计算其渗透水平流速。经试验传统点稀释公式计算得出的渗透水平流速在各砂层中对比流量法测试得到的流速偏大,在同一砂样不同水力梯度下两流速比值基本为一恒定值,而在不同砂层中比值不尽相同。对原点稀释计算公式进行了修正,并给出了修正系数实验值。     

Analysis of underground fires in Polish hard coal mines

In the period of the first twenty years after World War II the number of fires in Polish hard coal mines reached annually the value of several thousands of cases. About 80% of fires constituted spontaneous fires. Investigations into the development of new methods of fire hazard prediction and implementation of new methods and means of fire prevention as well as the introduction of prohibition concerning the use of products manufactured of combustible organic materials in underground mine workings re-duced considerably the hazard of underground fire rise. The worked out at the Central Mining Institute (GIG) new method of un-derground fire prediction allows the correct selection of fire prevention means. The introduction into common use of fire-resistant conveyor belts, the main factor giving rise to spontaneous fires, and methods of assessment of their fire resistance eliminated prac-tically the fire hazard. These activities contributed in an efficient way to the reduction of the number of underground fires to a sa-tisfactory level.