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Balance Analysis of Profit and Loss on Exploiting Coal-Bed Gas in China
Models about four aspects according to the balance principle and practice in China were established, which involve the minimum production scale, alert production scale, safe running scale, and the goal production scale for specified profit level. It provides an effective quantitative analyzing method for the investors of coal-bed gas exploitation project....
2020-06-12 16:17:18浏览：1428
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△P index with different gas compositions for instantaneous outburst prediction in coal mines
In this study we measured the △P(initial speed of gas emission)index with different gas concentrations of carbon dioxide(pure CO2,90% CO2+10% CH4,67% CO2+33% CH4,50% CO2+50% CH4,30% CO2+10% CH4 and pure CH4)of coal samples from the No.2 coal seam in the Yaojie Coal Mine,Gansu province,China.The effect of carbon dioxide concentration,gas composition,coal strength and particle size of coal samples on the △P index was investigated.The experimental results show that with gas of various compositions,the △P value of three samples were clearly different.The △P index of coal samples A,B and C(0.2～0.25 mm)were 4,6 and 7 with pure CH4 and 22,30 and 21 when pure CH4 was used.Carbon dioxide concentration affects the△P index markedly.The △P index increases with an increase in carbon dioxide concentration,especially for coal B.Hence,the△P index and K(another outburst index)values tested only with pure CH4 for prediction of the danger of outburst is not accurate.It is important to determine the initial speed of gas emission given the gas composition of the coal seam to be tested for exact outburst prediction....
2020-06-12 16:17:12浏览：1436
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Evaluation of coal bed methane content using BET adsorption isotherm equation
Coal bed methane is unconventional raw natural gas stored in coal seam with considerable reserves in China.In recent years,as the coal bed methane production,the safety and the use of resources have been paid more attentions.Evaluating coal bed methane content is an urgent problem.A BET adsorption isotherm equation is used to process the experimental data.The various parameters of BET equation under different temperatures are obtained; a theoretical gas content correction factor is proposed,and an evaluation method of actual coal bed methane is established....
2020-06-12 16:17:05浏览：1430
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Step change approaches in coal technology and fugitive emissions research
Multi-factor productivity (MFP) in underground coal mining has been on the decline for the last decade. The mining industry requires a viable and sustainable approach to overcome the current downtrend. This is only possible by concurrently focussing on productivity improvement and operating costs reduction, delivered through both incremental and step change technology development. Four technologies are pre-sented in this paper:fibre optic borehole sensing has been demonstrated to reveal detailed information about gas flow influx, water level and borehole blockage events occurring along the length of a surface-to-inseam lateral. Fibre optic gas sensing has also been investigated, and this technology promises a remote, intrinsically safe, distributed solution. Recent developments in continuous water jet drilling tech-nology have demonstrated a step change increase in drilling rates and flexibility for coal seam degassing, applicable in both surface-to-inseam and underground in-seam applications. The application of water jet technology to the cable bolt drilling problem offers potential to address a serious health and safety and productivity issue in the roadway development process....
2020-06-12 16:17:02浏览：1445
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Effect of roadway turnings on gas explosion propagation characteristics in coal mines
In order to reveal the effect of turnings on explosion propagation,experiments were performed in three different pipes (single bend,U-shaped pipe and Z-shaped pipe).Flame and pressure transducers were used to track the velocity at the explosion front.When the pipes were filled with methane,the explosion strength was significantly enhanced due to the turbulence induced by increasing the number of turnings,while the flame speed (Sf) and peak overpressure (△Pmax) increased dramatically.In addition,the strength of the explosion increased in violence as a function of the number of turnings.However,when the bend was without methane,the turnings weakened the strength of the explosion compared with the ordinary pipe,shown by the decrease in the values of △Pmax and Sf.In addition,the propagation characteristics in a U-shaped pipe were similar to those in a Z-shaped pipe and the values of △Pmax and Sf were also close.The results show that the explosion propagation characteristics largely depend on gas distribution in the pipes and the number of turnings.The different directions of the turnings had no effect....
2020-06-12 16:16:55浏览：1430
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Acoustic emission generated during the gas sorption-desorption process in coal
An experimental system for monitoring the acoustic signals generated in coal during gas sorption and/or desorption was designed and the acoustic signals were observed under different gas pressures.The experimental results show that signals generated by the coal during gas adsorption are attenuated over time.Also,the signals are not continuous but are impulsive.The intensity of the signals generated during gas desorption is far smaller than that observed during adsorption.The signal seen during desorption remains essentially stable.Cycles of sorption and desorption cause acoustic emission signals that exhibit a memory effect,which depends upon the maximum gas pressure the sample was exposed to in earlier cycles.Lower pressures in subsequent cycles,compared to the maximum adsorption pressure in previous cycles,cause both the energy and impulse frequency to be lower than previously.On the contrary,a gas adsorption pressure that exceeds the maximum pressure seen by the sample during earlier cycles causes both the energy and impulse frequency to be high....
2020-06-12 16:16:54浏览：1424
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Research into comprehensive gas extraction technology of single coal seams with low permeability in
For a low permeability single coal seam prone to gas outbursts,pre-drainage of gas is difficult and inefficient,seriously restricting the safety and efficiency of production.Radical measures of increasing gas extraction efficiency are pressure relief and infrared antireflection.We have analyzed the effect of mining conditions and the regularity of mine pressure distribution in front of the working face of a major coal mine of the Jiaozuo Industrial (Group) Co.as our test area,studied the width of the depressurization zone in slice mining and analyzed gas efficiency and fast drainage in the advanced stress relaxation zone.On that basis,we further investigated and practiced the exploitation technology of shallow drilling,fan drilling and grid shape drilling at the working face.Practice and our results show that the stress relaxation zone is the ideal region for quick and efficient extraction of gas.By means of an integrated extraction technology,the amount of gas emitted into the zone was greatly reduced,while the risk of dangerous outbursts of coal and gas was lowered markedly.This exploration provides a new way to control for gas in working faces of coal mines with low permeability and risk of gas outbursts of single coal seams in the Jiaozuo mining area....
2020-06-12 16:16:42浏览：1433
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Catastrophic mechanism of coal and gas outbursts and their prevention and control
Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point (P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load.When the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented....
2020-06-12 16:16:37浏览：1394
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Monitoring in Building Road Tunnel Across Coal Measures
In some cases coal measures,goaf,big caves,and huge faults,as well as high initial stress cannot be avoided in road tunnel excavation.These geological features may make it more difficul practical tunnel construction. So it is necessary to take strong precautious measures against gas outburst,water bursting and roof fall in a tunnel across coal measures with risk of gas outburst.The techniques,such as advance drilling exploration,multiple-cycle shallow depth hole controlled blasting,reinforced supporting,which include concrete grouting and twice supporting,and monitoring measures are often applied in the construction of tunnels and satisfied results are achieved. Results in this paper can help others to get experiences in road tunnel construction with similar geological features....
2020-06-12 16:16:37浏览：1405
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Critical Value of CO of Forecasting Coal Spontaneous Combustion
CO has been used widely in the production process of colliery as an index gas to predict spontaneous combustion of coal. But in some collieries there are CO gas in the upper corner of the face all the times, sometime CO gas even exceeds the regulated critical index. This phenomenon is much more obvious in the fully-mechanized longwall face and fully-mechanized longwall and top-coal caving face. Although many measures of fire-proof and fire-extinguishing have been adopted, the flowing amount of CO gas can be only decreasd, but can not be eliminated completely. Using the different kinds of coal, the experiment of coal oxidation was made at the low temperature. The experiment indicates that some kinds of coal can produce CO under the condition of normal temperature oxidation, sometime the CO consistency is very high, and the intension of CO can be decreased with oxidation time prolonging. Selecting rational critical value of CO is the kev to predicting spontaneous combustion of coal correctly and reliably. The problem of selecting retional critical value of CO was studied. Finally, the amount of CO gas released by different kinds of coal was obtained under normal temperature condition....
2020-06-12 16:16:33浏览：1433
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Stress emission of helium and argon in coal seams
In the Yutianbao Mine, the Nantong Coal Field, Chongqing, a lot of gas samples were measured and analyzed. It has been found in these samples that helium is sensitive to stress concentration, while argon is sensitive to stress release. Compared with the flowing out of gas itself, the combination of helium and argon can be more suitably used as an indicator to predict gas outburst. In a mining area of this mine, both δ He > 30 and δAr < δ0.97="" can="" be="" used="" critically="" to="" define="" the="" dangerous="" area.="" also,="" the="" contour="" maps="" of="" δ="" he,="" δ="" ar="" and="" ch4="" can="" provide="" a="" guidance="" for="" engineering="" monitoring.="">...
2020-06-12 16:16:11浏览：1431
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Determination of the volatile fraction of coal tar
The coal tar was qualitative and quantitative analyzed by gas chromatography (GC) method. 74 components were identified exactly by gas chromatography-mass spectrometry (GC-MS). 31 components (37%) were quantitatively analyzed by gas chromatography-flame ionization detector (GC-FID). The linearity, accuracy, precision, limit of detection (LOD) and limit of quantitative (LOQ) determination were inspected. The scope of quantitative analysis by GC was discussed. The experimental results of thermogravimetric analysis (TGA) proved that GC quantitative analysis of the coal tar was reliable....
2020-07-02 21:23:04浏览：1444
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Distribution of Heavy Hydrocarbon in Coal Seams and Its Use in Predicting Outburst of Coal
In order to verify whether any special gas component exists in outburst samples or not, coal samples from both outburst coal seams and non-outburst coal seams were collected. Some gases were extracted from the samples and analyzed qualitatively and quantitatively on chromatogram-mass spectrograph. The qualitative analysis show that there is no special gases in coal seams. And the quantitative analysis indicates that the heavy hydrocarbon content in coal samples from outburst coal seams is apparently higher than that from non-outburst district ones, which reflects the damage of geological tectonic movement to coal body in history. Therefore, the heavy hydrocarbon content of coal sample can be used as an index to predict coal outburst....
2020-07-02 21:23:04浏览：1420
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甲醇气体标准样品的研制
介绍了甲醇气体标准样品的制备和定值方法，考察采用重量法制备氮气中甲醇标准气体样品的重现性、标准气体的均匀性和稳定性。试验表明，甲醇气体标准样品在气瓶内均匀性良好，在12个月研制期间没有不稳定趋势。摩尔分数为149．2×10-6甲醇气体标准样品，扩展不确定度为3％，能够满足环境污染源废气中甲醇气体监测的要求。...
2020-06-12 15:51:20浏览：1410
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内标法与外标法测定餐具洗涤剂中甲醇含量的分析比较
对GB 9985-2000中内标法测定餐具洗涤剂中甲醇含量的方法进行了改进,并比较了内标法和外标法在测定洗涤剂中甲醇含量的差异.通过向洗涤剂样品中加入异丁醇内标液,用75％乙醇定容到一定体积,经0.45 μm针式微孔滤膜过滤,DB-FFAP色谱柱分离,火焰离子化检测器(FID)检测,内标法和外标法分别计算洗涤剂中甲醇的含量.实验得到方法的检出限为0.5 mg/L,内标法和外标法的相对标准偏差(RSD)分别为0.4％ ～0.9％和0.6％ ～1.2％,平均回收率分别为100％～102％和95％～99％.结果表明,采用内标法和外标法的定量方式获得的结果均能满足检测要求,但内标法的精密度和回收率优于外标法....
2020-06-12 15:51:05浏览：1431
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