Monitoring and analysis of daily gas concentrations at a mining face is a vital task on safety production and security management in the coal-mining industry. This study addresses modeling and prediction of daily gas ...Monitoring and analysis of daily gas concentrations at a mining face is a vital task on safety production and security management in the coal-mining industry. This study addresses modeling and prediction of daily gas concentration variations based on the elliptic orbit model. The model describes the hourly variation in daily gas concentration by mapping its time-series into the polar coordinates to create its elliptic orbit trace for further analysis. Experiments show workability of the proposed method that daily gas concentration variation at a mining face of one coal mine in China is well described by the elliptic orbit model. Result analysis and performance comparison of the proposed elliptic orbit model with the classical AR model on the same prediction tasks indicate potentiality of the proposed elliptic orbit model,which presents a vivid approach for modeling and forecasting daily gas concentration variations in an intuitive and concise way.展开更多
During mining of lower protective coal seam, a surface borehole can efficiently extract not only the pressure-relieved gas from the protected layer, but also the gas from the mining layer gob. If the distance between ...During mining of lower protective coal seam, a surface borehole can efficiently extract not only the pressure-relieved gas from the protected layer, but also the gas from the mining layer gob. If the distance between the borehole and gob is too large, the quantity of gas drained from the protected layer decreases substantially. To solve this problem, a mathematical model for extracting pressure-relieved gas from a protected coal seam using a surface borehole was established, based on the radial gas flow theory and law of conservation of energy. The key factors influencing the quantity of gas and the drainage flow network using a surface borehole were presented. The results show that the quantity of pressure-relieved gas drained from the protected layer can be significantly increased by increasing the flow resistance of the borehole bottom. Application of this method in the Wulan Coal Mine of the Shenhua Group significantly increased the flow of pure gas and the gas concentration （by factors of 1.8 and 2.0, respectively）, thus demonstrating the remarkable effects of this method.展开更多
In order to prevent coal and methane outbursts, mining protective layers is an effective means, yet no precedents of mining multiple protective layers is discoveried in seams which includes several seams are prone to ...In order to prevent coal and methane outbursts, mining protective layers is an effective means, yet no precedents of mining multiple protective layers is discoveried in seams which includes several seams are prone to outburst like Xinzhuangzi Mine. This paper perfected the related theories through analyzing mining multiple upper protective layers. By means of examining several parameters, it synthetically analyzed and ascer- tains the protected effectiveness and scope and reasonable parameters, finally obtained the specific indexes and effectiveness of mining multiple protective layers in coal seams cluster.展开更多
The effects of the molding pressure of a KO2 oxygen plate and the initial concentration of CO2 on the oxygen generation rate, the oxygen generation efficiency, and the carbon dioxide absorption rate were studied using...The effects of the molding pressure of a KO2 oxygen plate and the initial concentration of CO2 on the oxygen generation rate, the oxygen generation efficiency, and the carbon dioxide absorption rate were studied using a YES-300 hydraulic press to alter the pressure when forming the oxygen plate used in a coal mine refuge chamber. In addition, changes in the initial concentration of CO2 used in the closed- box model were made by adjusting the CO2 supply system, and a CD-7 multi-function parameter instrument was employed to monitor and record the changes of O2 and CO2 concentration in the closed-box model. Results indicate that the oxygen generation rate of KO2 oxygen plates, the oxygen generation efficiency, and the carbon dioxide absorption rate decrease when there is an increase in the pressure used to mold the oxygen plates, but those values increase when the initial CO2 concentration increases. When the initial concentration of CO2 in the dosed-box model is 3.5% and the forming pressure is 10 kN, the average oxygen generation rate of 15 g KO2 oxygen plate is 11.88 ×10^-3 L/min, the oxygen generation efficiency is 80.3%, and the average CO2 absorption rate is 11.0 × 10^-3 L/min. Compared with the condition where the initial CO2 concentration is 1.5%, the results show that average oxygen genera- tion rate of oxygen plates increases by 88,9%, the oxygen generation efficiency increases by 88.9%, and the CO2 absorption rate increases by 100%.展开更多
In order to enhance coalbed methane recovery, taking a self-developed largecalesimulation system for the platform, a modeling experiment of driving CH_4 by CO_2 gasinjection was studied.The results of experiment indic...In order to enhance coalbed methane recovery, taking a self-developed largecalesimulation system for the platform, a modeling experiment of driving CH_4 by CO_2 gasinjection was studied.The results of experiment indicates that there is a significant lag effectof adsorption and desorption on gas, the gas pressure is changed more rapidly in theprocess of carbon dioxide adsorption of coal than methane adsorption of coal; After theinjection of carbon dioxide, compare with methane single desorption.In an early stage,speed and amount of methane single desorption are greater than the speed and amountof displacement desorption, the speed and amount of displacement desorption becamegreater.In the process of replacement, CH_4 concentration constantly declined, while CO_2concentration constantly rose.In the process of CO_2 gas injection, the temperature of coalhave been significantly increased, it is more beneficial to make CH_4 gas molecules becomefree from the adsorbed state when temperature is increased.Under the pressurestep-down at the same rate, using the method of CO_2 driving CH_4, compared with themethod of conventional pressure step-down, the desorption rate of CH_4 in coal can beraised about 2.13 times, at the same time, a lot of greenhouse gas CO_2 will also be buriedin the ground, there is a very significant environmental benefit.展开更多
Low-concentration methane(LCM) has been one of the biggest difficulties in using coal mine methane.And previous studies found that premixed combustion in porous media is an effective method of low calorific gas utiliz...Low-concentration methane(LCM) has been one of the biggest difficulties in using coal mine methane.And previous studies found that premixed combustion in porous media is an effective method of low calorific gas utilization. This paper studied the combustion of LCM in a divergent porous medium burner(DPMB) by using computational fluid dynamics(CFD), and investigated the effect of gas initial temperature on combustion characteristic, the distribution of temperature and pollutant at different equivalence ratios in detail. Besides, the comparison of divergent and cylindrical burners was also performed in this paper. The results show that: the peak temperature in DPMB increases as the increasing of equivalence ratio, which is also suitable for the outlet NO discharge; the linear correlation is also discovered between peak temperature and equivalence ratios; NO emission at the initial temperature of 525 K is 5.64 times,larger than NO emission at the initial temperature of 300 K. Thus, it is preferable to balance the effect of thermal efficiency and environment simultaneously when determining the optimal initial temperature range. The working parameter limits of divergent burner are wider than that of cylindrical one which contributes to reducing the influence of LCM concentration and volume fluctuation on combustion.展开更多
基金supported by the Scientific Research Fund of Hunan Provincial Science and Technology Department (No. 2013GK3090)the National Natural Science Foundation of China (Nos. 51374107 and 51577057)the Research Fund of Hunan Provincial Natural Science Foundation (No. 13JJ8014)
文摘Monitoring and analysis of daily gas concentrations at a mining face is a vital task on safety production and security management in the coal-mining industry. This study addresses modeling and prediction of daily gas concentration variations based on the elliptic orbit model. The model describes the hourly variation in daily gas concentration by mapping its time-series into the polar coordinates to create its elliptic orbit trace for further analysis. Experiments show workability of the proposed method that daily gas concentration variation at a mining face of one coal mine in China is well described by the elliptic orbit model. Result analysis and performance comparison of the proposed elliptic orbit model with the classical AR model on the same prediction tasks indicate potentiality of the proposed elliptic orbit model,which presents a vivid approach for modeling and forecasting daily gas concentration variations in an intuitive and concise way.
文摘During mining of lower protective coal seam, a surface borehole can efficiently extract not only the pressure-relieved gas from the protected layer, but also the gas from the mining layer gob. If the distance between the borehole and gob is too large, the quantity of gas drained from the protected layer decreases substantially. To solve this problem, a mathematical model for extracting pressure-relieved gas from a protected coal seam using a surface borehole was established, based on the radial gas flow theory and law of conservation of energy. The key factors influencing the quantity of gas and the drainage flow network using a surface borehole were presented. The results show that the quantity of pressure-relieved gas drained from the protected layer can be significantly increased by increasing the flow resistance of the borehole bottom. Application of this method in the Wulan Coal Mine of the Shenhua Group significantly increased the flow of pure gas and the gas concentration （by factors of 1.8 and 2.0, respectively）, thus demonstrating the remarkable effects of this method.
文摘In order to prevent coal and methane outbursts, mining protective layers is an effective means, yet no precedents of mining multiple protective layers is discoveried in seams which includes several seams are prone to outburst like Xinzhuangzi Mine. This paper perfected the related theories through analyzing mining multiple upper protective layers. By means of examining several parameters, it synthetically analyzed and ascer- tains the protected effectiveness and scope and reasonable parameters, finally obtained the specific indexes and effectiveness of mining multiple protective layers in coal seams cluster.
基金financially supported by the Research Fund for the Doctoral Program of Higher Education of China (No. 20130006120020)the China Postdoctoral Science Foundation (No. 2013M540866)+1 种基金the China Postdoctoral Science Foundation (No. 2014T70039)the Fundamental Research Funds for the Central Universities (No. FRF-TP-14-083A2)
文摘The effects of the molding pressure of a KO2 oxygen plate and the initial concentration of CO2 on the oxygen generation rate, the oxygen generation efficiency, and the carbon dioxide absorption rate were studied using a YES-300 hydraulic press to alter the pressure when forming the oxygen plate used in a coal mine refuge chamber. In addition, changes in the initial concentration of CO2 used in the closed- box model were made by adjusting the CO2 supply system, and a CD-7 multi-function parameter instrument was employed to monitor and record the changes of O2 and CO2 concentration in the closed-box model. Results indicate that the oxygen generation rate of KO2 oxygen plates, the oxygen generation efficiency, and the carbon dioxide absorption rate decrease when there is an increase in the pressure used to mold the oxygen plates, but those values increase when the initial CO2 concentration increases. When the initial concentration of CO2 in the dosed-box model is 3.5% and the forming pressure is 10 kN, the average oxygen generation rate of 15 g KO2 oxygen plate is 11.88 ×10^-3 L/min, the oxygen generation efficiency is 80.3%, and the average CO2 absorption rate is 11.0 × 10^-3 L/min. Compared with the condition where the initial CO2 concentration is 1.5%, the results show that average oxygen genera- tion rate of oxygen plates increases by 88,9%, the oxygen generation efficiency increases by 88.9%, and the CO2 absorption rate increases by 100%.
文摘In order to enhance coalbed methane recovery, taking a self-developed largecalesimulation system for the platform, a modeling experiment of driving CH_4 by CO_2 gasinjection was studied.The results of experiment indicates that there is a significant lag effectof adsorption and desorption on gas, the gas pressure is changed more rapidly in theprocess of carbon dioxide adsorption of coal than methane adsorption of coal; After theinjection of carbon dioxide, compare with methane single desorption.In an early stage,speed and amount of methane single desorption are greater than the speed and amountof displacement desorption, the speed and amount of displacement desorption becamegreater.In the process of replacement, CH_4 concentration constantly declined, while CO_2concentration constantly rose.In the process of CO_2 gas injection, the temperature of coalhave been significantly increased, it is more beneficial to make CH_4 gas molecules becomefree from the adsorbed state when temperature is increased.Under the pressurestep-down at the same rate, using the method of CO_2 driving CH_4, compared with themethod of conventional pressure step-down, the desorption rate of CH_4 in coal can beraised about 2.13 times, at the same time, a lot of greenhouse gas CO_2 will also be buriedin the ground, there is a very significant environmental benefit.
基金the supports by the National Basic Research Program of China (No. 2011CB201205)the National Natural Science Foundation of China (No. 51204169)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (No. 20110095120017)the Fund of China Postdoctoral Science Foundation of China (No. 20110491482)
文摘Low-concentration methane(LCM) has been one of the biggest difficulties in using coal mine methane.And previous studies found that premixed combustion in porous media is an effective method of low calorific gas utilization. This paper studied the combustion of LCM in a divergent porous medium burner(DPMB) by using computational fluid dynamics(CFD), and investigated the effect of gas initial temperature on combustion characteristic, the distribution of temperature and pollutant at different equivalence ratios in detail. Besides, the comparison of divergent and cylindrical burners was also performed in this paper. The results show that: the peak temperature in DPMB increases as the increasing of equivalence ratio, which is also suitable for the outlet NO discharge; the linear correlation is also discovered between peak temperature and equivalence ratios; NO emission at the initial temperature of 525 K is 5.64 times,larger than NO emission at the initial temperature of 300 K. Thus, it is preferable to balance the effect of thermal efficiency and environment simultaneously when determining the optimal initial temperature range. The working parameter limits of divergent burner are wider than that of cylindrical one which contributes to reducing the influence of LCM concentration and volume fluctuation on combustion.
