Evaluation of the 20 L dust explosibility testing chamber and comparison to a modified 38 L vessel for underground coal

The phenomenon of combustible dust explosions is present within many industries. Tests for explosibility of dust clouds per ASTM E1226 use a 20 L explosive chamber that places the combustible dust directly below the dispersion nozzle which generates a thorough mixture for testing purposes. However, in the underground coal mining industry, there are a number of geologic, mining, and regulatory factors that change the deposition scheme of combustible coal dust. This causes the atmosphere of a coal mine to have a variable rock dust-coal dust mixture at the time of ignition. To investigate the impact of this variable atmosphere, a series of lean explosibility tests were conducted on a sample of Pittsburgh Pulverized coal dust. These explosibility tests were conducted in a 38 L chamber with a 5 kJ Sobbe igniter. The 38 L chamber generates a variable air-dust mixture prior to ignition. The test results indicate that the 38 L chamber experiences reduced explosive pressures, and lower explosibility index values when compared to the 20 L chamber.

Semi-Industrial Test of Underground Coal Gasification In Well No.2 in Xinhe, Xuzhou

The necessity of underground coal gasification is explained. The condition,technology character,and process of the semi-industrial test of underground coal gasification in well No. 2 at Xinhe, Xuzhou,are introduced. The test results indicate that the technique of long tunnel,large sectiou,two stage underground coal gasification can obtain a large output of coal gas with a high heat value, making the working process stable. So the feasibility of the new techuology is verified. It can be concluded that there will have a good application prospect of the technique in China.

基于W-OH的矿区重构冻土阻水层功能评价模拟研究

为缓解高寒矿区扰动土体难以形成冻土带来的不利影响,选取5种W-OH浓度(0%、1.5%、2.5%、3.5%、4.5%)喷施于扰动土体底部,重构矿区冻土阻水层,进行抗压试验、入渗试验和模拟降雨试验,分别从物理性能、入渗产流产沙、经济性3个层面进行重构阻水层评价分析,采用层次分析法和专家打分法选出8个影响重构阻水层的主要因子,构建重构阻水层功能评价体系,根据综合评分选出该地区最佳的重构阻水层方案。结果表明:(1)W-OH增强了煤矸石固结体的强度,特别是4.5%W-OH浓度时效果最明显。(2)W-OH浓度上升导致重构阻水层入渗率降低,稳渗历时延长,累计入渗量减少。(3)在降雨条件下,W-OH浓度升高降低了煤矸石固结体的稳定入渗率,增加了平均产流率和平均产沙率,并且平均产流率和平均产沙率都同W-OH浓度、坡度存在正相关关系。(4)4.5%W-OH浓度方案功能综合评分最高,但在实际施工中,4.5%W-OH浓度方案易堵塞喷头,故推荐使用评分次之的3.5%W-OH浓度方案重构矿区冻土阻水层。研究结果可为W-OH在高寒矿区重构冻土阻水层应用提供理论依据。

Coriolus versicolor对褐煤溶解过程的条件优化

为了提升劣质褐煤的资源利用率,本文以云南昭通的露天褐煤为研究对象,利用微生物Coriolus versicolor进行溶煤的实验研究。通过正交实验,考察了培养基种类、微量元素的添加量、加煤时间等因素对溶煤效果的影响,使用紫外-可见光分光光度计(UV-Vis)和红外光谱分析仪(FTIR)对溶煤产物进行了分析。结果表明,培养基种类对溶煤效果的影响最大,微量元素添加量的影响最小。当使用DOX培养基、微量元素的添加量为7mL、在第0天添加煤时,溶煤条件最优。溶煤产物主要为带支链的芳香族化合物,FTIR谱图中检测到大量的氢键(3000cm^(-1)~3700cm^(-1))、芳环(1700cm^(-1))、甲基/亚甲基(1440cm^(-1)、2890cm^(-1)附近)和酯/醚键(1030cm^(-1)、1200cm^(-1)附近)等。

Space-time evolution rules of acoustic emission location of unloaded coal sample at different loading rates

By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious ''step'',which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.

Coupling mechanism between mining-induced deformation and permeability of coal

The coupling mechanism between mining-induced mechanical behavior and gas permeability of coal is effectively obtained in laboratory.This study means significant understanding of the prevention of coal-gas outburst.The testing samples of coal were drilled from the 14120 mining face at the depth of690 m.Based on the redistribution of stress during the excavation,the coupling test between mechanical state and seepage has been designed using the triaxial servo-controlled seepage equipment for thermofluid-solid coupling of coal containing methane.It is the result that there are two main factors influencing the mining-induced mechanical behavior of coal,such as the change ofσ_1-σ_3 andΔσ_1-Δσ_3.The failure mode mainly depends on the value ofσ_1-σ_3,and the peak strength value mainly depends on the value ofΔσ_1-Δσ_3.The difference of mechanical response between geostress and mining-induced stress has been obtained,which can be a theoretical support for safe mining such as reasonable gas drainage,prevention of coal-gas outburst and gas over-limit.

燃煤电厂取水设施物理模型试验研究

某燃煤电厂调试阶段出现了循环冷却水量不足而导致机组停机现象,排查供水系统源头,发现取水泵运行时发生喘振,造成供水量不足,进一步引发机组停机。为保障燃煤电厂机组安全稳定运行,其取水水源需要稳定可靠,取水设施各部位尺寸应合理设计。以巴基斯坦某660 MW燃煤电站海水取水工程为例,对海水取水泵房及配套设施进行物理模型试验研究,并对设计方案进行了验证,试验结果表明,推荐设计方案布置可满足HIS(hydraulic institute standards)建议值,能保证取水设备安全稳定运行。

Creep properties and a creep equation of delay outburst coal and its adjacent mudstone

The study of the creep properties of coal and its adjacent mudstone is very important for understanding the mechanism of delay outburst coal. The samples of delay outburst coal and its adjacent mudstone collected from Yongshanqiao mine were used to carry out triaxial creep tests. The influence of confining pressure and axial compression on the creep test was analyzed. An accelerated creep model was constructed in parallel with a nonlinear viscous component and plastic component. It is connected with the traditional Burges creep model in series. A creep model which can describe the nonlinear viscoelastic-plastic creep model of rock was established and the corresponding creep equation was derived.According to the results of the creep test, the related parameters of the equation were fitted. The results show that, under the same confining pressure, instantaneous creep strain, creep strain of deceleration phase and constant rate creep of the coal and its adjacent mudstone are increased with an increase in the deviatoric stress. But at the same axial pressure, all of the above decrease with an increase of confining pressure. The duration time of the deceleration creep phase increases with the increase in the deviatoric stress. The theoretical values of the creep equation are in good agreement with the experimental results. It indicates that the creep properties of the delayed outburst coal and its adjacent mudstone can be well described by the creep model established in this paper.

Liberation characteristics of coal middlings comminuted by jaw crusher and ball mill

The associated minerals make coal middlings possess a relatively high ash content.Subsequent liberation through size reduction can cause recovery increase.However,effect of comminution facilities on mineral liberation of middlings was ignored.This paper studied the liberation characteristics of middlings crushed with different kinds of fragmentation forces.Middlings of 3 mm+0.5 mm sampled from a dense medium cyclone were comminuted by a jaw crusher and a ball mill to 0.5 mm with similar size distribution respectively.The generating mechanism of fnes was also analyzed.Full densimetric analyses indicate that mineral liberation of the product crushed by the jaw crusher is better than that by the ball mill at each fraction.For sizes of 0.125 mm+0.074 mm and 0.074 mm,yields of the product with ash content 11%comminuted by jaw crusher are nearly 20%higher than that by the ball mill.Sectional micrographs observed by the scanning electron microscopy(SEM)also show the same law for these two fractions and some intergrowth particles still exist in the fraction of 0.5 mm+0.25 mm.

构造煤层顶板爆破跨界面致裂增透机制研究及应用

深部煤炭开采地质条件恶化,原生煤在多期构造运动作用下形成松软低渗高瓦斯构造煤层,煤层钻孔施工困难,爆破增透产生的裂隙不发育且易于重新压实。针对目前构造煤层顶板爆破致裂增透关键技术没有得到根本突破问题,构建试验模型进行煤层顶板爆破相似模拟试验和数值分析,监测跨界面应力波传播和宏观三维裂隙演化形态,再现了爆破应力波传播和煤岩体内部损伤破坏过程。研究表明:(1)构造煤层爆破损伤范围主要集中在爆破孔和煤层上下煤岩交界面附近煤体;构造煤顶板爆破产生跨界面致裂卸压裂纹,爆破损伤沿爆破孔向四周岩体扩展,最后蔓延到煤层底板,爆破孔位置和上部煤岩交界面以及煤层内部的损伤较为严重。(2)爆破应力波从构造煤层顶板传播到煤岩交界面时发生波的透射和反射,透射的压缩应力波破坏煤体;反射的拉伸应力波反作用于煤岩交界面区域岩体。(3)爆破累积损伤产生的跨界面交叉裂纹卸压,使顶板岩层裂隙和构造煤层裂隙贯通,有利于构造煤层的瓦斯垂向运移流动和卸压瓦斯抽采。现场应用表明,煤层顶板爆破瓦斯抽采纯量及其浓度快速上升,瓦斯抽采纯量从爆破前的0.07 m^(3)/min提高到1.73 m^(3)/min,体积分数从10.46%上升到68.50%,并且长时间维持在较高水平。研究成果可为深部构造煤层瓦斯高效抽采提供理论基础和技术支持。

Experimental Study on Shear Mechanical Properties and Section Morphology of Coal Samples

The mechanical properties of rocks under cyclic and dynamic loading are important research topics for solving the structural stability of large engineering rocks. As underground mining in coal mines goes deeper, ground stresses are increasing and instability damage of coal rocks by shear loading is frequent. Therefore, in order to investigate the shear mechanical properties and section morphological characteristics of intact coal samples in the direct shear test, the RDS-200 rock direct shear instrument was used to carry out direct shear tests on intact coal samples under different normal stresses, and the shear section was scanned for three-dimensional morphology. The results show that: 1) from the strength characteristics, the peak shear strength of the coal samples increased linearly with increasing normal stress, and the residual shear strength increased logarithmically. 2) In terms of deformation characteristics, the peak shear displacement of the coal sample increases linearly with increasing normal stress, the pre-peak shear stiffness increases logarithmically, and the residual normal displacement decreases linearly. 3) From the morphological characteristics of the shear surface, with the increase of normal stress, the section transitions from high-order undulating to flattening type. The maximum height of the fracture surface profile and kurtosis coefficient of the shear section decreased linearly, and the profile area ratio and root mean square of slope decreased as a power function, i.e. the higher the normal stress, the smaller the undulation of the section, the sharpness of the roughness shape and the roughness coefficient JRC, and the flatter and smoother the section. The findings of this study can help to provide some reference for the evaluation of shear instability occurring in coal bodies under different normal stresses.

Correlativity between coal permeability and strain in quasi-plane strain state

To simulate the variety of big coal sample permeability during the rupture process under quasi-plane strain state, a series of experiments have been performed by a set of self-made coal-gas coupling test system. The test results indicate that the development trend between the permeability rate-strain curve and the stress-strain curve of big coal sample is almost consistent. The permeability rate-strain curve is general hysteretic to stress-strain curve, indicating the close relativity between the evolvement of damage and the development of permeability rate. However, there is time interval between them and the perme- ability rate peaks value when the sample reaches the softened stage after the peak stress. Based on the characteristics of per- meability rate-strain curve, three stages were plotted out： the stage before minimum permeability rate （/co）, the stage between minimum and maximum of permeability rate and the stage after the maximum permeability rate （kmax）. According to the three stages of permeability rate, the segmental curve equations of permeability rate-strain were fitted： the first stage can be fitted with negative exponential function; the second stage can be fitted with Boltzmann equation; and the last stage can be fitted with multinomial equation.

Nephelometric Performance Evaluation of Oxidized Starch in the Treatment of Coal Washery Effluent

This study investigated the coag-flocculation performance of oxidized starch coagulant (OSC) and its blends with alum and FeCl3 in removing turbidity from coal washery effluent at room temperature. A conventional laboratory bench-scale jar test apparatus was employed for the experiments. Coag-flocculation parameters such as reaction order α, rate constant K, coagulation time τ, etc. were determined. The optimum pH was observed at 4.0, while the blend of 30.0 mg/L FeCl3 and 250.0 mg/L OSC achieved the optimum turbidity removal. Turbidity removal efficiency was recorded between 96.0% and 99.9% for various dosages and pH studied. The coagulation rate constants, K recorded range from 9.393 × 10-5 L/mg.min to 8.294 × 10-1 min-1, while coagulation periods τ, range from 3.8 s to 235.7 s for various dosages and pH studied. The use of OSC blended with FeCl3 showed high level of efficiency, for the treatment of coal washery effluent.

基于Weibull分布的煤矸石对混凝土断裂损伤特性的影响

为探索煤矸石质量取代率、粉煤灰质量取代率、水灰比对I型裂缝煤矸石混凝土荷载-裂缝张开位移、荷载-跨中挠度曲线、断裂韧性、断裂能的影响规律,对I型裂缝煤矸石混凝土进行三点弯曲试验,将所得结果结合损伤力学及Weibull分布函数建立煤矸石混凝土的断裂损伤本构模型。结果表明:煤矸石质量取代率对预制I型裂缝的煤矸石混凝土断裂性能影响最大,粉煤灰质量取代率对其断裂韧度影响较大,水灰比对其断裂能影响较大;提升煤矸石混凝土断裂时断裂韧度及断裂能的最佳组合的煤矸石质量取代率为25%、粉煤灰质量取代率为10%、水灰比为0.5;经对比可知,所得损伤本构模型对应的应力-应变曲线与试验曲线高度吻合。研究成果为煤矸石混凝土的制备及工程实际应用研究提供了参考。

Leaching behavior of V,Pb,Cd,Cr,and As from stone coal waste rock with different particle sizes

This paper investigates the leaching behavior of heavy metals(V,Pb,Cd,Cr,and As) from stone coal waste rocks with various particle sizes using dynamic leaching experiments.The results show that the dissolved concentrations of V and As initially increased and then slightly decreased as time progressed and that the dissolved concentrations of Pb,Cd,and Cr were high in the early stage before decreasing.The particle size of the stone coal waste rocks strongly influenced the heavy metal concentration in the leaching solutions.The effects of the particle size of the stone coal waste rocks on the dissolved concentrations of V,Pb,and As decreased in the order fine fraction > medium fraction > coarse fraction,and the effects of particle size on the dissolved concentrations of Cr and Cd decreased in the order medium fraction > coarse fraction > fine fraction and coarse fraction > medium fraction > fine fraction,respectively.The quantities of heavy metals dissolved from the stone coal waste rock with fine particle sizes were observed to decrease in the order V(17104.36 μg/kg) > As(609.41 μg/kg) > Pb(469.24 μg/kg) > Cr(56.35 μg/kg) > Cd(27.52 μg/kg),and the dissolution rates decreased in the order As(2.96%) > Pb(0.93%) > V(0.35%) > Cd(0.25%) > Cr(0.01%).The specific surface area,pore size of the stone coal waste rocks,and chemical forms of heavy metals also influenced the release of heavy metals from the stone coal waste rocks.Kinetic analysis showed that the dissolution of heavy metals fundamentally agreed with the rate equation controlled by the shrinking core model.The results of this study are expected to serve as a reference for the evaluation of heavy metals contamination from stone coal waste rocks.

煤系高岭石热活化及其对水泥净浆长期强度的影响研究

【目的】煤矸石的高值化利用是目前研究的热点,煤矸石中高岭石的活化及作用对煤矸石的高值化利用意义重大。【方法】首先采用正交试验方法进行了煤系高岭石的热活化参数优化设计研究,再以最优条件形成的煤系偏高岭土替代部分水泥,对净浆的抗压强度、物相组成及微观结构进行了分析。【结果】试验结果表明,煤系高岭石最佳热活化条件为煅烧温度800℃,保温时间2 h,粉磨细度2.82μm.煅烧温度对煤系偏高岭土活性影响最大,粉磨细度次之,保温时间最小;采用煤系偏高岭土替代20%(质量分数)水泥,可加快水泥的水化反应速率,有效提升净浆在各养护龄期的抗压强度,其中早期强度提升最显著;微观机理分析发现,煤系偏高岭土发生火山灰反应消耗了大量氢氧化钙,形成了结构更致密的低钙硅比水化硅酸钙。

煤的温压吸附试验方法与等温吸附试验方法比较研究

为了研究煤的温压吸附试验方法在煤层气吸附方面的可行性,本文对煤的温压吸附试验方法与煤的高压等温吸附试验方法进行了比较研究。分别取12个、10个、8个、和6个温压吸附试验点作为四组不同温度和相应不同压力作为温压吸附试验点,记为V_(实测)。使用温度-压力-吸附方程(Temperature-Pressure-AbsobingEquation(TPAE)),将方程转化为二元一次方程后进行线性回归计算其余三个参数,将所得的四个参数记为V_(计算)。通过计算_(实测)与V_(计算)之间的平均相对误差和标准偏差以衡量温压吸附试验方法的可行性。

煤岩蠕变试验及其灾变模型

为全面揭示煤岩长历时蠕变破坏机制,开展了长历时煤岩单轴压缩分级蠕变声发射试验,分析了不同应力水平下煤岩蠕变变形和声发射规律,在此基础上,把临界幂律灾变函数引入理想黏弹塑性体,并与Burgers体串联,建立煤岩灾变蠕变模型。结果表明:煤岩单轴蠕变经历减速、稳定和加速蠕变3个阶段,声发射参数的变化规律能很好地反映煤岩蠕变3个阶段的变形特征;减速蠕变阶段内声发射事件较活跃,稳定蠕变阶段内低应力水平下声发射活动比中应力水平多,当从稳定蠕变阶段到加速蠕变阶段时,煤岩突然宏观脆性破坏,应变发生突变,声发射突然增大,呈现灾变破坏特征;高应力水平下的减速和稳定蠕变阶段煤岩内部裂隙充分且均匀发育,最终导致煤岩发生粉碎性的灾变破坏,这一破坏特征不同于单轴压缩破坏的剪切破坏;煤岩灾变蠕变模型能全面体现煤岩减速、稳定和加速蠕变阶段,已有几种非线性蠕变模型预测高应力水平蠕变试验结果相关系数最大为0.74,而灾变蠕变模型预测的相关系数大于0.97。岩石蠕变试验数据拟合结果表明灾变模型能够很好地描述各类岩石蠕变过程,临界幂律指数β对灾变破坏起控制作用,随着β的不断增大,岩石蠕变也从渐进式破坏转变为灾变破坏,从而验证了此煤岩灾变蠕变模型的正确性和适用性。

松软煤层大采高工作面煤壁片帮机理及深浅孔交替超前预注浆加固技术研究

目的为探究松软煤层大采高工作面煤壁片帮机理,并对片帮严重的松软煤层大采高工作面煤壁进行有效控制,方法利用材料力学理论得到煤壁片帮的频发位置,引入煤壁剪切破坏准则,得出松软煤体煤壁片帮的主控因素。并以李村煤矿1305工作面为例,通过FLAC3D建立数值模型,以煤壁最大位移、煤体破坏深度、支承压力大小和支承压力峰值位置4个因素作为参考比较对象,通过引入正交试验法,研究了煤层埋深、内摩擦角、黏聚力、抗拉强度以及支护强度对煤壁片帮的影响程度。结果结果表明:煤体自身的物理力学性质(内摩擦角和黏聚力)是影响煤壁片帮的主要因素,其次煤体的赋存条件(埋深)也是一个较为关键的影响因素。结论工业性试验基于正交试验结果提出了大采高综采工作面深浅孔交替超前预注浆加固技术,有效控制了李村煤矿1305工作面煤壁片帮严重情况,为其他类似地质条件大采高综采工作面煤壁片帮控制提供了借鉴。

Utilization of Coal Ash as a Barrier Material for Radioactive Waste Disposal

About 10% of total electricity (386 MkW) was generated by nuclear power plants in the world (2014) and about 58,400 tons of uranium has been mined in uranium mines annually. A plenty of radioactive waste material is produced from uranium mines and nuclear power plants. The wastes must be disposed or stored safely for a long term. Because if they leak and/or move from disposal or storage sites due to air/groundwater flow, then a serious environmental pollution can occur. Hence, multi-layer system has been proposed and employed in order to seal off these radioactive waste materials from biosphere. Basically, bentonite is now used for establishing one of absorbing and sealing layers in this system. However, the amount of high quality bentonite is very limited and in some cases it is hard to be obtained. On the other hand, a great deal of refuse from coal burning plants is produced every year and the amount of it is expected to be higher each year especially in developing countries. More than half of coal ash is utilized and the remaining is disposed at the disposal sites. However, the life of the disposal site is limited and it is difficult to find a new disposal site. It is requested that the percentage of the utilization of the coal ash be increased in every field. From the above two points of view, a fly ash-based barrier system is considered in this research and this paper discusses the applicability of fly ash as a content of barrier material. Based on the results of a series of laboratory tests, it can be concluded that fly ash has a potential for use in the buffer material as the bentonite is substituted.