煤的解吸规律研究现状及发展趋势

瓦斯是煤层中的主要气体,研究分析煤层解吸瓦斯的规律,能够有效地避免煤层开采时煤与瓦斯突出的危险。在以往的研究中,不难发现煤解吸瓦斯与煤的孔隙结构、破坏类型以及水分、灰分和挥发分有关,还与振动、压力、温度等因素有关。本文主要分析温度、振动以及孔隙结构对瓦斯解吸的影响程度,并且提出目前存在的不足,指出了煤炭解吸瓦斯的发展趋势和应用前景,并将其应用于需要解决的实际工程问题。

利用煤钻屑瓦斯解吸指标法测定煤层瓦斯含量

煤层瓦斯含量是计算矿井瓦斯储量和预测瓦斯涌出量的基础,也是预测煤与瓦斯突出的重要参数之一。在实验基础上,提出了煤钻屑瓦斯解吸指标法测定煤层瓦斯含量法,并经过实际验证该方法合理可靠。

煤钻屑瓦斯解吸指标Δh_2自动测定系统设计

针对当前实验室内测定不同瓦斯吸附压力条件下的煤钻屑瓦斯解吸指标值Δh_2的过程存在步骤繁琐、自动化程度低、人为干扰因素较多的问题,设计了一种基于单片机控制的高精度煤钻屑瓦斯解吸指标Δh_2自动测定系统。该系统以Atmega16单片机为核心,以USART_HMI触摸屏为系统指令输入及显示输出装置。单片机通过识别触摸屏发送的指令对各种传感器、继电器、电磁阀进行操作,完成煤样的自动脱气、吸附、卸压、测定等过程,最终测得煤钻屑在不同瓦斯吸附压力条件下的解吸指标Δh_2值。测试结果表明,与现有煤钻屑瓦斯解吸仪相比,该自动测定系统相对误差控制在5%以内,具有良好的实用性和较好的数据准确性。

一种电子式煤钻屑瓦斯解吸指标测定仪的设计

本研究针对现有机械式煤钻屑瓦斯解吸指标测定仪存在的操作复杂、井下人工读数误差大和测定数据无法保存并上传的问题的分析,研制了一种电子式测定仪,增加了电磁阀,优化了手动阀的设计,提高了测定精度和自动化程度,操作简单,在煤矿现场应用效果良好,相比老仪器取得了较大的提高。

谈煤层突出危险性预报指标K_1的敏感性

讨论了影响K1值预报结果准确性的3个方面,即K1值的敏感性,K1测定值的真实性,K1临界值与预报结果;现场测定环节影响K1测定值的真实性;建立了K1值测定的误差分析和仪器漏气判别依据;K1临界值取定也影响预报结果的质量,但不影响其敏感性。

突出煤相似材料综述及展望

突出煤相似材料是进行煤与瓦斯突出模拟实验的基础,相似材料的研究有助于更准确地还原煤与瓦斯突出现象。对国内外相似材料的研究成果进行了综述,对相似材料制作过程中各个因素对相似材料力学、吸附解吸和渗透率3方面性能的影响进行了梳理,同时指出了相似材料的发展方向:全面衡量材料在力学、吸附解吸和渗透率方面的性能;对原料和制作工艺标准化;细化相似材料的定量评价方法。

采空区瓦斯涌出强度对其流动规律的影响研究

为准确掌握煤矿井下采空区瓦斯分布及流动规律,自主研制了常压块煤瓦斯解吸测定装置,开展了不同尺寸块煤瓦斯长时间解吸试验,分析了块煤尺寸对瓦斯解吸量、解吸速率的影响,建立了不同涌出源的采空区瓦斯涌出强度模型,并利用COMSOL Multiphysics数值模拟软件模拟分析了U形回风条件下不同涌出强度对采空区瓦斯流动的影响。结果表明,1)不同尺寸块煤(3 cm、5 cm、8 cm、13 cm)的累计瓦斯解吸量随时间延长均呈现增大趋势,在前期变化较为明显,随着时间的推移,瓦斯解吸量逐渐趋于稳定,且累计瓦斯解吸量随块煤尺寸增大呈现增长趋势;不同尺寸块煤解吸速率与时间存在负指数函数关系,且块煤尺寸越小,其初始瓦斯解吸速率与解吸速率衰减系数的平均值(试验前40d)也越大。2)在U形回风条件下,不同涌出强度模型将导致采空区瓦斯体积分数随时间呈现不同的变化趋势,采用瓦斯涌出衰减模型时,瓦斯体积分数随时间推移呈先增大后减小的变化趋势;采用均匀恒定模型时,瓦斯体积分数随时间推移先增大后趋于平缓。因此,为准确预测采空区瓦斯分布特征,制定合理高效的抽采方案,应充分考虑瓦斯涌出强度的影响。

突出预测指标Δh_2测定超前钻孔有效影响半径

介绍了目前常用的测定超前钻孔有效影响半径的方法,并对其分析比较。现场结合容光煤矿C5煤层的实际情况,选择钻屑瓦斯解吸指标Δh2,采用常用方法和新方法分别测定了在C5煤层中Φ89mm超前钻孔的有效影响半径。测定结果表明新方法用来测定超前钻孔的有效影响半径同样准确有效。

Experimental study on effects of CBM temperature-rising desorption

To study the effects of CBM （coal bed methane） temperature-rising desorption, isothermal adsorption/desorption experiments on three ranks （anthracite, coking coal and lignite） of coal at different temperatures were designed based on the traditional CBM decompression desorption. The experimental results indicate that temperature-rising desorption is more effec- tive in high-rank coal, and ever-increasing temperature of high-rank coal reservoir can reduce the negative effects of coal ma- trix shrinkage in the process of production and improve the permeability of the coal reservoir as well. It is also revealed that the technique of temperature-rising desorption applied in higher-rank coal reservoir can enhance CBM recovery ratio. This study provided theoretical support for the application of temperature-rising desorption technique in practical discharging and mining projects, which can effectively tackle the gas production bottleneck problem.

Gas desorption characteristics of the high-rank intact coal and fractured coal

The objective of this work is to study the gas desorption characteristics of the high-rank intact coal and fractured coal.The gas adsorption,mercury porosimetry and gas desorption experiments were carried out in this study.Then,the theories of thermodynamics,diffusion mechanism and desorption kinetics were used to estimate the gas desorption characteristics.The results of gas adsorption experiments show that the initial isosteric adsorption heat of the intact coal is greater than that of the fractured coal,indicating that the gas molecules desorb more easily from fractured coal than intact coal.Using the mercury porosimetry,we find that the diffusion channels of fractured coal are more developed than those of intact coal.The difficult diffusion form dominates in the intact coal during the gas diffusing,while the easy diffusion form dominates in the fractured coal.The results of gas desorption experiments show that the initial gas desorption volume and velocity of the fractured coal are both greater than those of the intact coal.Using the Fick diffusion law,the study calculates the gas diffusion coefficients of the intact coal and fractured coal.The diffusion coefficients of the fractured coal are 2 times and 10 times greater than those of the intact coal at the time of 0-120 and 0-10 min,respectively.

综采面顺层钻孔瓦斯抽放消突技术研究

成庄矿为了消除煤层的突出危险性,安全有效地开采井下3号煤层4311综采面,采用顺层钻孔预抽该综采面回采区域煤层瓦斯。成庄矿4311综采面作为试验区进行了消突措施、消突效果技术研究,在该综采面预抽煤层瓦斯过程中以及抽放结束后,进行煤层残余瓦斯含量测定,并对该综采面煤层区域进行预抽煤层瓦斯抽采效果达标和消突效果达标评判。上述措施确保了该矿综采面4311的高产高效安全生产,取得了良好的经济效益。

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.

Geologically controlling factors on coal bed methane （CBM） productivity in Liulin

It is of great significance to forecast high yield of CBM wells and analyze dynamic production by having an overall study on the characteristics of the produced CBM and determining the main factors influencing the productivity of CBM. With the test report and the related geological parameters of a single well, methods of combining the productivity data and typical production curves were used to analyze different geological factors and how to influence the capacity of a single layer. Then, the paper proposed a new understanding about capacity characteristics of the study area and geological control factors： First, the Shanxi formation production capacity characteristics was divided into two-stages, showing signs of gas and gas break- through for 100 days. Second, two parameters, which include potential of gas production and gas production capacity, were bet- ter than the single parameter, such as gas content, coal thickness, and penetration to analyze affecting factors of single well pro- duction. Finally, comprehensive analysis concluded that the ratio of critical desorption pressure to reservoir pressure has greater influence on the production of vertical CBM wells. Besides, the potential of gas production capacity has greater impact at stage of showing gas signs; the coal reservoir pressure and gas production capacity have greater impact at stage of gas breakthrough for 100 days. Thus, to seek the coal bed methane with high ratio of critical desorption pressure to reservoir pressure and high yield of gas will be important guarantee to the success of the coal bed methane exploration and development.

High rank coalbed methane desorption characteristic and its application in production in Qinshui basin

Based on spontaneous desorption characteristic, the correlation of desorption time and gas content was analyzed and the application of it in production was researched. The desorption of high rank coalbed methane in Qinshui basin was periodic, and isotope fractionation effect also exists in the process. △δ^13C1 can be used to distinguish the stabilization of coalbed methane wells, associated with desorption rate, the individual well recoverable reserves can be calculated. Economically recoverable time can be predicted according to the logarithmic relationship between desorption gas content per ton and desorption time. The error between predicted result and numerical simulation result is only 1.5%.

Denitrification of Coal Tar Diesel Fraction by Phosphate Imidazolium Based Polymeric Ionic Liquids

A series of highly cross-linked polymeric ionic liquids P[Ci(Vim)_2][Cl]_2(i = 2,3,4,5,6) were synthesized by quaternization reaction and polymerization,and used to remove nitrogen compounds from oils.The polymeric ionic liquids P[Ci(Vim)_2][H_2PO_4]_2(i = 2,3,4,5,6) were then obtained via ion exchange.The structures of P[C_4(Vim)_2][Cl]_2 and P[C_4(Vim)_2][H_2PO_4]_2 were characterized by Fourier transform infrared(FT-IR) spectroscopy,energy dispersive spectrometry(EDS),N2 adsorption-desorption isotherm measurements,scanning electron microscopy(SEM),thermogravimetric analysis and differential scanning calorimetry(TG/DSC).The removal of nitrogen compounds was characterized by pyridineFTIR spectrometry.The results indicated that P[C_4(Vim)_2][H_2PO_4]_2 with an average pore size of 19.23 nm and a specific surface area of 11.78 m^2/g was efficient for the removal of nitrogen compounds,and exhibited good thermal stability.The adsorption rate in the simulated oil reached 93.8% when using a polymeric ionic liquid P[C_4(Vim)_2][H_2PO_4]_2 to oil ratio of 0.04 and a temperature of 313 K.The nitrogen removal rate from the coal-tar diesel fraction achieved by P[C_4(Vim)_2][H_2PO_4]_2 was 90.3%.

Characteristics and applications of gas desorption with excavation disturbances in coal mining

According to the deficiency of experiment system for gas adsorption and desorption in coal mass, a large scale experiment system is developed independently by researchers. This experiment system is composed of primary and auxiliary boxes, power transmission system, mining system, loading system, gas charging system, data monitoring and intelligent acquisition system. The maximum experiment coal consumption is 1200 kg, the mining system is developed to conduct experiment for gas desorption under excavating disturbance, and the plane-charging cribriform ventilation device is developed to realize uniform ventilation for experiment coal sample, which is accord with the actual gas source situation of coal bed. The desorption characteristics of gas in coal are experimentally studied under the conditions of nature and mining using the experiment system. The results show that, compare with nature condition, the permeability of coal and the velocity of gas desorption could significantly increase under the influence of coal pressure relief and destruction caused by mining, and the degree of gas desorption could somewhat increase too. Finally, pressure relief gas extraction of current seam and adjacent seams after mining in a certain coal mine of Yangquan mining area are introduced, and the gas desorption experiment results is verified by analyzing the effect of gas extraction.

Infrared measurement of temperature field in coal gas desorption

In order to reveal the temperature change in coal gas desorption process,the temperature variation in coal gas desorption process under different particle sizes is analyzed with infrared thermal imager.The infrared video signals obtained by the experiment are processed with SAT.Then the infrared radiation signals are processed by EMD with Hilbert–Huang and the infrared radiation noise is effectively removed.The research results show that the desorption process,with the change of the temperature,is an endothermic process.The coal absorbs heat when the gas is desorbed and the temperature drops.The coal body temperature drop range is obviously related to coal particle size.The smaller the particle size is,the bigger the temperature drop becomes.The temperature variation curves in the process of coal gas desorption under different particle sizes are fitted,and they comply with the exponential function.The research results lay the theoretical and experimental foundation for non-contact prediction on working face of coal and gas outburst with infrared thermal image technology.

Kinetic characteristics of coal gas desorption based on the pulsating injection

In order to understand the kinetic characteristics of coal gas desorption based on the pulsating injection （PI）, the research experimentally studied the kinetic process of methane desorption in terms of the PI and hydrostatic injection （HI）. The results show that the kinetic curves of methane desorption based on PI and HI are consistent with each other, and the diffusion model can best describe the characteristics of meth- ane desorption. Initial velocity, diffusion capacity and ultimate desorption amount of methane desorption after P! are greater than those after HI, and the ultimate desorption amount increases by 16.7-39.7%. Methane decay rate over the time is less than that of the HI. The PI influences the diffusion model param- eters, and it makes the mass transfer Biot number B＇_i decrease and the mass transfer Fourier series F＇_0 increase. As a result, PI makes the methane diffusion resistance in the coal smaller, methane diffusion rate greater, mass transfer velocity faster and the disturbance range of methane concentration wider than HI. Therefore, the effect of methane desorption based on PI is better than that of HI.

Evolvement behavior of microstructure and H_2O adsorption of lignite pyrolysis

The effect of pyrolysis on the microstructure and moisture adsorption of lignite was investigated with low field nuclear magnetic resonance spectroscopy. Changes in oxygen-containing groups were analyzed by Fourier transform infrared spectroscopy （FTIR）, and H20 adsorption mechanism on the surface of lignite pyrolysis was inferred. Two major changes in the pore structure of lignite char were observed as temperature increased in 105-200 ℃ and 500-700 ℃. Pyrolysis temperature is a significant factor in removing carboxyl and phenolic hydroxyl from lignite. Variation of ether bond content can be divided into three stages; the content initially increased, then decreased, and finally increased. The equilibrium adsorption ratio, content of oxygen-containing groups, and variation of pore volume below 700° were closely correlated with each other. The amount of adsorbed water on char pyrolyzed at 700 ℃ increased. Moreover, the adsorption capacity of the lignite decreased, and the adsorption state changed.

Numerical description of coalbed methane desorption stages based on isothermal adsorption experiment

Quantitative description of desorption stages of coalbed methane is an important basis to objectively understand the production of coalbed methane well,to diagnose the production state,and to optimize the management of draining and collection of coalbed methane.A series of isothermal adsorption experiments were carried out with 12 anthracite samples from 6 coalbed methane wells located in the south of the Qinshui Basin,based on the results of isothermal adsorption experiments,and an analytical model was developed based on the Langmuir sorption theory.With the model,a numerical method that adopts equivalent desorption rate and its curve was established,which can be used to characterize the staged desorption of coalbed methane.According to the experimental and numerical characterizations,three key pressure points determined by the equivalent desorption rate curvature that defines pressure-declining desorption stage,have been proposed and confirmed,namely,start-up pressure,transition pressure and sensitive pressure.By using these three key pressure points,the process of coalbed methane desorption associated with isothermal adsorption experiments can be divided into four stages,i.e.,zero desorption stage,slow desorption stage,transition desorption stage,and sensitive desorption stage.According to analogy analysis,there are differences and similarities between the processes of coalbed methane desorption identified by isothermal adsorption experiments and observed in gas production.Moreover,it has been found that larger Langmuir volume and ratio of Langmuir constants are beneficial to earlier advent of steady production stage,whereas it is also possible that the declining production stage may occur ahead of schedule.