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.

Combustion mechanism and control approaches of underground coal fires:a review

With the large-scale mining of coal resources,the huge economic losses and environmental problems caused by underground coal fires have become increasingly prominent,and the research on the status quo and response strategies of underground coal fires is of great significance to accelerate the green prevention and control of coal fires,energy conservation and emission reduction.In this paper,we summarized and sorted out the research status of underground coal fires,focused on the theoretical and technical issues such as underground coal fire combustion mechanism,multiphysics coupling effect of coal fire combustion,fire prevention and extinguishing technology for underground coal fires,and beneficial utilization technology,and described the latest research progress of the prevention and control for underground coal fire hazards.Finally,the key research problems in the field of underground coal fire hazards prevention and control were proposed in the direction of the basic theory,technology research,comprehensive management and utilization,with a view to providing ideas and solutions for the management of underground coal fires.

Research on the mechanism of rockburst induced by mined coal-rock linkage of sharply inclined coal seams

In recent years,the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased.Local deformation of mining coal-rock results in frequent rockbursts.This has become a critical issue that affects the safe mining of deep,steeply inclined coal seams.In this work,we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data.We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof,explaining the mechanical response behavior of key disaster-prone zones within the deep working face,affected by the dynamics of deep mining.By exploring the spatial correlation inherent in extensive microseismic data,we delineate the“time-space”response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face.The results disclose that(1)the distinctive coal-rock occurrence structure characterized by a“sandwiched rock pillar-B6 roof”constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine,with both elements presenting different degrees of deformation localization with increasing mining depth.(2)As mining depth increases,the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration.The localized deformation of deep,steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions,increasing the energy distribution disparity and stress asymmetry of the“sandwiched rock pillar-B3+6 coal seam-B6 roof”configuration.This makes worse the propensity for frequent dynamic disasters in the working face.(3)The developed high-energy distortion zone“inner-outer”control technology effectively reduces high stress concentration and energy distortion in the surrounding rock.After implementation,the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430%and 300%,respectively,thus guaranteeing the safe and efficient development of steeply inclined coal seams.

Study on partition of spontaneous combustion danger zone and prediction of self-ignition in coalmine based on numeric simulation

By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as well as duration of spontaneous combustion from large-scale spontaneous combustion experiment, 'three zones' of spontaneous combustion were partitioned and mining conditions to avoid spontaneous combustion were obtained. The above method was employed to partition 'three zones' in gob of fully mechanized top-coal caving long wall face and got fairly good result. Calculation of the above method is much smaller than simulating the whole process of coal spontaneous combustion, but the prediction precision can satisfy the demand of predicting and extinguishing spontaneous combustion in mining.

Study and application of plasticity plaster-slurry for preventing coal spontaneous combustion

Introduced the modulation scheme, function and mechanism of plasticity plaster slurry preventing coal spontaneous combustion. The applications show that the plasticity plaster slurry has good hygroscopicity and adsorptivity. To spray it on the coal wall of tunnel can shut off leakage wind fast and effectively. To press it into the coal body can absorb the heat and descend the temperature, surround the coal pieces, eliminate the possibility of the fiery district resuming combustion.

Disasters of gas-coal spontaneous combustion in goaf of steeply inclined extra-thick coal seams

In light of the escalating global energy imperatives,mining of challenging-to-access resources,such as steeply inclined extra-thick coal seams(SIEC),has emerged as one of the future trends within the domain of energy advancement.However,there is a risk of gas and coal spontaneous combustion coupling disasters(GCC)within the goaf of SIEC due to the complex goaf structure engendered by the unique mining methodologies of SIEC.To ensure that SIEC is mined safely and efficiently,this study conducts research on the GCC within the goaf of SIEC using field observation,theoretical analysis,and numerical modeling.The results demonstrate that the dip angle,the structural dimensions in terms of width-to-length ratio,and compressive strength of the overlying rock are the key factors contributing to the goaf instability of SIEC.The gangue was asymmetrically filled,primarily accumulating within the central and lower portions of the goaf,and the filling height increased proportionally with the advancing caving height,the expansion coefficient,and the thickness of the surrounding rock formation.The GCC occurs in the goaf of SIEC,with an air-return side range of 41 m and an air-intake side range of 14 m,at the intersection area of the“<”-shaped oxygen concentration distribution(coal spontaneous combustion)and the“>”-shaped gas concentration distribution(gas explosion).The optimal nitrogen flow rate is 1000 m3/h with an injection port situated 25 m away from the working face for the highest nitrogen diffusion efficacy and lowest risk of gas explosion,coal spontaneous combustion,and GCC.It has significant engineering applications for ensuring the safe mining of SIEC threatened by the GCC.

Analysis and Design Innovation on Underground Gasifier for Medium-Deep Coal Seam

Over the past 80 years,dozens of underground coal gasification(UCG)mine field tests have been carried out around the world.However,in the early days,only a small number of shallow UCG projects in the former Soviet Union achieved commercialised production.In this century,a few pilot projects in Australia also achieved short-term small-scale commercialised production using modern UCG technology.However,the commercialisation of UCG,especially medium-deep UCG projects with good development prospects but difficult underground engineering conditions,has not progressed smoothly around the world.Considering investment economy,a single gasifier must realise a high daily output and accumulated output,as well as hold a long gasification tunnel to control a large number of coal resources.However,a long gasification tunnel can easily be affected by blockages and failure,for which the remedial solutions are difficult and expensive,which greatly restricts the investment economy.The design of the underground gasifier determines the success or failure of UCG projects,and it also requires the related petroleum engineering technology.Combining the advantages of the linear horizontal well(L-CRIP)and parallel horizontal well(P-CRIP),this paper proposes a new design scheme for an“inclined ladder”underground gasifier.That is to say,the combination of the main shaft of paired P-CRIP and multiple branch horizontal well gasification tunnels is adopted to realise the control of a large number of coal resources in a single gasifier.The completion of the main shaft by well cementation is beneficial for maintaining the integrity of the main shaft and the stability of the main structure.The branch horizontal well is used as the gasification tunnel,but the length and number of retracting injection points are limited,effectively reducing the probability of blockage or failure.The branch horizontal well spacing can be adjusted flexibly to avoid minor faults and large cracks,which is conducive to increasing the resource utilisation rate.In addition,for multi-layer thin coal seams or ultra-thick coal seams,a multi-layer gasifier sharing vertical well sections can be deployed,thereby saving investment on the vertical well sections.Through preliminary analysis,this gasifier design scheme can be realised in engineering,making it suitable for largescale deployment where it can increase the resource utilisation rate and ensure stable and controllable operations.The new gasifier has outstanding advantages in investment economy,and good prospects for application in the commercial UCG projects of medium-deep coal seams.

Experiment Research of Application of FMCCT in Complex-Condition Coal Seams

The fully-mechanized caving coal technique (FMCCT) is a great technique progress of mining method in thick coal seams in China, and it has succeeded in some suitable condition mines. This paper introduces some technical measures and achieved outcomes in gas and fire precaution and support selection for the use of the fully-mechanized caving coal technique in the complex-condition coal seams based on the practice of Weijiadi Coal Mine, in which the technique is used in the gently inclined extremelythick soft coal seam with the dangers of coal and gas outburst and spontaneous combustion.

Comparative Experimental Analysis on Coal Spontaneous Combustion

The goal of this study was to investigate coal quality features and their relationship to coal spontaneous combustion characteristics in multi-seam coal mines to better predict when coal spontaneous combustion is likely to occur.To that end,coal samples of various particle sizes were obtained from five coal seams(Nos.6,8,9,12 and 20)in the Shuangyashan City Xin’an Coal Mine.The samples were then respectively heated using a temperature programming system to observe and compare similarities and differences in the sponta-neous combustion process of different particle sizes in response to rising temperature.The experimental results show,that in all five coal seams,the concentration of CO,C_(2)H_(4),and C_(2)H_(6) increased with a certain degree of regularity as a function of rising temperature.However,of these three gasses,only CO and C_(2)H_(4) can be used as indicators to predict coal mine spontaneous combustion.The critical temperature for samples from all five coal seams ranged from 50–85℃,while the dry cracking temperature of coal seams 8 and 12(80–100℃)were lower than those of 6,9,and 20(100–120℃).Furthermore,the production rate of CO,C_(2)H_(4),and C_(2)H_(6) is related to both coal particle size and temperature.The smaller the particle size,the faster the production rate;and the higher the temperature,the more gas that gets produced.All five coal seems are mainly com-posed of long flame coal.However,they differ in that the No.12 coal seam contains weak cohesive coal;the No.8 coal seam contains lean and gas coal;and the Nos.6,9,and 20 coal seams contain a certain amount of anthracite.During the programmed coal heating,the CO,C_(2)H_(4),and C_(2)H_(6) release trend for the coal seams was No.12>No.8>Nos.6,9,and 20.These results demonstrate that the presence of weak cohesive coal and anthracite highly influence the concentration of CO,C_(2)H_(4),and C_(2)H_(6) released during coal spontaneous combustion.

煤矸石自燃的关键影响因素及治理方法研究现状

煤矸石作为煤炭的伴生产物,长期堆存过程中自燃现象频发,直接或间接产生生态污染、水体污染、地质灾害等诸多问题,造成巨大经济损失和人员伤亡。煤矸石从堆积初期到燃烧状态受诸多因素影响,包括自身性质、自燃条件和外部环境等,是一个复杂的物理化学反应过程。为提高煤矿矿区矸石自燃的防治能力,分析了煤矸石自燃理论的研究现状,系统总结了现阶段国内外学者对煤矸石自燃机理和治理方法的研究进展。围绕可燃物、氧气、温度3个影响煤矸石自燃的必要因素,提出了引发自燃的主要关键影响因素和作用过程机理。较全面介绍已有煤矸石山自燃防治的主要方法,对比分析了各种常规煤矸石自燃灭火手段以及治理技术的优缺点,指出了常规简单技术治理效果的局限性。针对煤矸石作为砂、石等替代材料,回填露天矿坑、采煤塌陷区等区域进行土地整治和生态修复,提出在防治过程中要明确自燃治理的控制对象,提升防灭火材料的特定性能,通过智能化设备提高辨识准确性进行精细化监控,并运用多种监测预警技术协同自燃防治材料多手段多方法运用综合治理,并提出了煤矸石自燃防治技术的未来发展和矿用防灭火材料的研究方向,为后续开展煤矸石自燃机理研究及自燃防治工程应用提供参考和理论支持。

急倾斜特厚煤层冲击地压防治探索与总结

急倾斜特厚煤层开采顶板破断运动复杂,应力和能量演化规律特殊,在深部“三高一扰动”影响下,冲击地压防治不容乐观。基于某矿2016年冲击地压事故后急倾斜特厚煤层水平分段开采冲击地压防治经验,从急倾斜特厚煤层水平分段开采冲击地压发生机理、瓦斯突出与冲击地压综合防治和冲击地压管理详细介绍了该矿7年来急倾斜特厚煤层冲击地压防治经验。冲击地压发生机理方面,建立了顶板岩层倾斜悬臂梁模型,揭示了顶、底板覆岩结构破断失稳演化过程,划分了夹持煤体受力状态分区,提出了急倾斜特厚煤层冲击“夹持理论”。瓦斯突出与冲击地压综合防治方面,基于冲击地压灾害控制解危技术的强度弱化减冲理论,结合原有防突措施体系,提出了既能防冲且对防突有利的解危措施,形成了某矿瓦斯/CO_(2)突出-冲击地压“双防”技术体系,建立了适用于某矿急倾斜特厚煤层水平分段开采的冲击地压防治体系,以钻屑量和瓦斯吸解值验证了瓦斯突出防治的强度保障,同时以加强实施卸压措施工作面的微震事件分布及各能级总频次和能量对比,论证说明了卸压方案防治效果的有效性。冲击地压管理方面,形成了预测评价、监测预警、治理预防、效果检验、安全防护和教育培训“六位一体”综合防治架构,基于《煤矿安全规程》和《防治煤矿冲击地压细则》等各项规定,制定了Q/YJMD-—FC 0104-2022《窑街煤电集团有限公司煤矿冲击地压防治第四部分:冲击地压防治技术规范》。

急倾斜深埋巨厚煤层掘巷冲击地压前兆特征及其灾害防治

随着冲击地压矿井逐渐向深开采,其巷道掘进伴随的冲击显现愈发强烈。针对巷道掘进过程中的冲击地压有效防治问题,以新疆乌东煤矿急倾斜煤层矿井为例,运用微震监测对巷道掘进的冲击地压时空前兆特征加以分析。结合巷道掘进的应力与能量变化数值模拟分析,揭示巷道掘进的冲击地压发生机理,提出急倾斜巨厚煤层巷道冲击地压防治策略,并完成现场工程实践验证。研究结果表明:急倾斜巨厚煤层巷道掘进的冲击地压发生前第2~5天出现微震总能量极低值,或存在至少4 d的能量潜伏期;冲击地压发生前5 d普遍存在3 d以上的最大能量占比高频波动期。冲击地压发生前存在明显缺震现象,发生位置集中分布在距离掘进工作面较近的微震能量极小值区间范围内,或位于微震能量极值区间附近的微震频次极小值区间范围内,且冲击地压事件位于冲击变形能指数较高区域。急倾斜巨厚煤层水平分段综放开采的坚硬覆岩结构不易破断,使得巷道掘进存在上水平采空区两侧“双翼型”应力集中,掘进工作面前方与巷道底部受顶底板岩层相互挤压的应力集中分布且能量积聚显著,随着巷道掘进深度增加其应力集中与能量积聚进一步增强,容易诱发冲击地压等动力灾害。综合分析形成急倾斜巨厚煤层巷道掘进的工作面爆破卸压、巷道钻孔卸压与补强支护、复杂区域架蓬的冲击地压防治策略。结合冲击地压时空前兆异常为及时加强卸压力度提供时机。通过工作面与巷道卸压使得掘进期间未发生单日累计1×105 J以上微震能量,在对支护优化调整与复杂区域重点防护后,巷道掘进日均微震能量降至2.2 kJ,其1 kJ以上微震事件占比下降且巷道断面整体平整。研究结果为急倾斜巨厚煤层巷道安全掘进提供了科学依据。

地下煤火分维—分级探测预警技术研究

为实现煤自燃隐蔽火源的高效监测预警和防治,本文对地下煤火分维—分级探测预警技术展开研究。首先,揭示煤自燃受热升温及燃烧过程的煤自燃的电磁—声波—温—气变化特征,形成电磁—声波—氡气—红外多维探测方法,实现井上井下联合多维探测应用;其次,根据大尺寸煤自燃指标气体产生规律,建立基于正压输运的煤自燃监测预警体系,实现地下煤自燃发火的分级精准预警;最后,依据复杂区域综放面煤层自燃发火特点、影响因素及变化规律,提出复杂开采煤自燃灾害综合防治技术体系。研究成果可为井下煤自燃灾害预警防治提供依据与参考。

煤制油气化灰渣防灭火凝胶的制备及性能

针对煤制油气化灰渣堆积造成环境污染和固废资源浪费等问题,本研究提出以气化灰渣为基料、羟丙基甲基纤维素(HPMC)为胶凝剂,制备气化灰渣凝胶煤矿防灭火材料,使用扫描电镜和傅里叶红外光谱仪分析其微观形貌与表面官能团特征。考察了材料的胶凝时间、热稳定性及保水性,确定了气化渣凝胶最优配方为水灰比1∶1.25、HPMC添加量1.5%(质量分数)。该凝胶较好抑制了煤自燃过程中羟基、甲基、亚甲基、取代芳烃、醚碳氧键等官能团反应,与未经凝胶处理的煤样相比,经凝胶处理的煤样在80℃时芳香烃峰面积减小11.85%,脂肪烃峰面积减小43.07%,120℃时芳香烃峰面积减小27.36%,脂肪烃峰面积减小44.23%。凝胶处理的煤样在氧化升温过程中,100℃时CO浓度降低65.07%,200℃时CO浓度降低53.09%,C 2H 4浓度降低23.68%。微观和宏观结果表明,气化灰渣凝胶较好地抑制了煤自燃进程,阻化性能优于CaCl 2,可有效防治煤自燃灾害,解决灰渣堆积问题,实现固废资源化利用。

大采深高承压水条件下煤层底板突水问题及解决对策

在当前煤矿普遍面临大采深、底板高承压水、高地应力等采掘条件下,正确评价煤层底板承压水突水危险是做好防治水工作的基础。以河南省受底板灰岩承压水突水威胁的大水矿井为例,就底板破坏深度计算、突水系数计算及临界值、脆弱性指数法、不同水文地质单元的“双层水位”效应等问题进行了剖析。分析表明:在大采深和高地应力开采条件下,底板破坏深度较现有用经验公式计算得到的值偏大,一些矿井突水系数虽小于全国临界值,但回采过程中却发生了突水,脆弱性指数法有待于规范化。此外,井田范围内水文地质条件存在着时空变化,甚至会出现“双层水位”等现象。鉴于此,提出了建立大采深和高地应力开采条件下的底板破坏深度计算模型、确定矿区或矿井范围的临界突水系数值、规范脆弱性指数评价方法、查明水文地质条件的时空变化和不同单元的水动力参数、制定同各单元水文地质条件相适应的防治水措施等各项对策。

易自燃厚煤层综采工作面CO溯源数值分析

甘肃某矿厚煤层2804综放工作面,回采期间的上隅角CO浓度长期保持150×10^(-6)左右,严重威胁井下人员安全。实验揭示了不同温度和O_(2)浓度下CO生成规律,建立了采空区CO生成运移的热-固-流-化多场耦合模型,定量分析了地温、工作面风量及回采速度对采空区CO生成-运移规律的影响。结果表明,当温度超过40℃时,煤的氧化反应速率开始增加,且随O_(2)浓度增大,煤的氧化反应越剧烈,生成的CO越多;回采过程中工作面上隅角CO浓度呈现递增趋势,生成速率先增大后减小,且随着地温、风量增大而增大;综合分析认为2804工作面上隅角CO主要来源于采空区内部浮煤氧化。

残煤复采区巷道掘进凝胶堵漏防灭火技术研究

采空区中遗留煤炭自燃现象直接影响着煤矿的安全高效开采,而采用堵漏材料封闭漏风通道是解决采空区煤自燃问题的有效方法。以运河煤矿F1301复采工作面为工程背景,针对在采空区中掘进巷道时遗留松散煤体的自燃隐患问题,制定了松散煤体凝胶堵漏防灭火技术实施方案,采用COMSOL数值模拟方法研究了不同注胶时间与压力下的凝胶扩散规律,并进行了工程应用。结果表明:注胶时间和压力与凝胶扩散范围成正比,综合考虑注胶效果与成本,选取10 MPa、140~160 min为最佳的注胶压力与时间,注胶钻孔间距设置为5 m;实施凝胶堵漏防灭火方案后,巷道两侧观测钻孔监测数据显示,标志气体CO体积分数稳定于24×10^(-6)以下,凝胶堵漏防灭火效果良好,有效消除了采空区遗留煤炭自然发火隐患。

大倾角工作面采空区均压-注氮联合防火数值模拟研究

以峻德煤矿93172大倾角外部漏风工作面为例,研究大倾角外部漏风采空区均压参数合理性以及对注氮防火的影响。采用Fluent数值模拟方法对采空区进行流场分析,充分考虑位压的影响,合理设置工作面和采空区进回风口及漏风口压力边界参数;建立了“L”形大倾角采空区冒落分布模型,进行采空区“恰当均压”,“欠均压”,“过均压”数值模拟,探究不同均压工况的采空区自燃三带分布,同时探讨了采空区均压注氮的合理参数选择。结果表明:“恰当均压”的采空区自然氧化带宽度最短;注氮防火应在“恰当均压”条件下进行,否则将会极大降低采空区惰化效果,徒增注氮量。研究结果对现场科学制定均压-注氮联合防火措施提供理论指导,同时压力边界参数设置方法为大倾角工作面采空区均压-注氮联合防火相关数值模拟研究提供科学参考。

浅埋近距离煤层群开采过程中上覆采空区自燃危险区预测研究

为揭示浅埋深近距离煤层群开采过程中地表裂隙发育对上覆采空区遗煤自燃的影响规律及影响范围,以苏家沟煤矿为研究背景,建立采空区流场流动及低温氧化的数学模型和三维几何模型。采用FLUENT模拟软件模拟了下煤层工作面推进过程中上覆采空区的氧气分布情况,得到了浅埋近距离煤层上覆采空区基于裂隙动态发育的氧气场和风流场的分布规律。依据采空区自燃危险区域判定理论,对上部煤层采空区内的自然发火危险区域进行预测。结果表明:连通地表与采空区的裂隙数量随工作面的推进而增加,上覆采空区氧化升温区域主要集中在滞后工作面0~20 m范围内,采空区深部的氧化带分布在新、老裂隙附近,在进风侧靠近地表且在回风侧靠近裂隙底端;当工作面推进120 m,即产生3条贯通型裂缝时,采空区自燃危险性最大,结合风流场云图确定上煤层底板自燃危险区距工作面水平距离为97.5 m,是煤矿开采过程中的重点防护区域。

改性固废基多孔颗粒吸附CO_(2)及其解吸抑制煤自燃特性研究

煤矿采空区遗煤自燃灾害频发,严重危害矿井安全生产。为了防治采空区遗煤自燃,本文研究了一种胺改性固废多孔材料,并研究了胺改性固废多孔材料的CO_(2)吸附性能及抑制煤自燃特性。研究结果表明,有机胺改性剂能够成功负载在固废多孔颗粒上,并且在不同有机胺(乙醇胺(MEA)、二乙烯三胺(DETA)、四乙烯五胺(TEPA)、聚乙烯亚胺(PEI))改性多孔颗粒中,四乙烯五胺(TEPA)改性多孔颗粒CO_(2)吸附性能最好。CO_(2)吸附实验结果表明,随着改性剂负载量的增大,CO_(2)吸附量先升高后降低,25℃、1bar条件下,有机胺负载量为20wt%时,吸附量最大达到119.24mg/g;改性剂负载量相同时,CO_(2)吸附量随着温度的升高先增加后降低,70℃时吸附量最高,为128.97 mg/g。程序升温测试结果显示,相较于添加未吸附CO_(2)的改性颗粒,添加吸附CO_(2)的改性颗粒后,煤样的交叉点温度升高了29.2℃,有效降低了煤自燃危险性,温度升高过程中改性颗粒吸附的CO_(2)能够解吸,降低煤颗粒周围的氧浓度,从而抑制采空区遗煤自燃。本文研究对促进工业固废的高效利用、推动采空区煤自燃灾害高效防控技术的发展具有重要意义。