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 w...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.展开更多
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 like...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.展开更多
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 ...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.展开更多
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 technic...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.展开更多
Based on the statistical data of 26 outburst prone coal seams in China, this paper presents the relationship among the threshold gas pressure in coal and gas outburst and the volatile content and hardness of coal by m...Based on the statistical data of 26 outburst prone coal seams in China, this paper presents the relationship among the threshold gas pressure in coal and gas outburst and the volatile content and hardness of coal by mathematical statistics. The threshold value of gas pressure for outburst pmin in MPa may be calculated by formula Pmin =5(0. 1+0. 07Kf), where / is the hardness and V the volatile content (%) of a soft bed. In China, the value of Pmin of some outburst prone coal seams ranges from 0. 57 to 0. 1 MPa.展开更多
基金Supported by Natural Science Program of Shaanxi Province Education Department (05JK261)
文摘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.
基金support from the Major Project of Engineering Science and Technology in Heilongjiang Province in 2020(Grant No.2020ZX04A01)support from the Scientific Research Projects of Undergraduate Universities in Heilongjiang Province(Grant No.2020-KYYWF-0534).
文摘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.
基金support from the National Key R&D Program of China(Grant No.2022YFC3004704)the National Natural Science Foundation of China(Grant No.52374241)the National Natural Science Foundation of China Youth Foundation(Grant No.52104230).
文摘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.
文摘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.
文摘Based on the statistical data of 26 outburst prone coal seams in China, this paper presents the relationship among the threshold gas pressure in coal and gas outburst and the volatile content and hardness of coal by mathematical statistics. The threshold value of gas pressure for outburst pmin in MPa may be calculated by formula Pmin =5(0. 1+0. 07Kf), where / is the hardness and V the volatile content (%) of a soft bed. In China, the value of Pmin of some outburst prone coal seams ranges from 0. 57 to 0. 1 MPa.
