Comprehensive evaluation of water-inrush risk from coal floors

Lower groups of coal seams are presently being mined from water-inrush from coal floors in order to have safe production in the Yanzhou coal mining area. We need to evaluate the risk in the lower groups of coal seams in mines. Based on a systematic collection of hydrogeological data and some data from mined working faces in these lower groups, we evaluated the factors affecting water-inrush from coal floors of the area by a method of dimensionless analysis. We obtained the order of the factors affecting water-inrush from coal floors and recalculated data on depths of destroyed floors by multiple linear regression analysis and obtained new empirical formulas. We also analyzed the water-inrush coefficient of mined working faces of the lower groups of coal seams and improved the evaluation standard of the water-inrush coefficient method. Finally, we made a comprehensive evaluation of water-inrush risks from coal floors by using the water-inrush coefficient method and a fuzzy clustering method. The evaluation results provide a solid foundation for preventing and controlling the damage caused by water of an Ordovician limestone aquifer in the lower group of coal seams in the mines of Yanzhou. It provides also important guidelines for lower groups of coal seams in other coal mines.

CO2-hierarchical activated carbon prepared from coal gasification residue: Adsorption equilibrium, isotherm, kinetic and thermodynamic studies for methylene blue removal

Mineral matter in a residue(RC G)from coal gasification(CG)was removed by two-stage acid leaching.Hierarchical activated carbon(HAC)was prepared by activating RC Gwith CO2.The performance of HAC on removing methylene blue(MB)from an aqueous solution was investigated.HAC was characterized by N2 adsorption–desorption isotherm,Fourier transform infrared spectroscopy,and scanning electron microscopy.The results show that HAC exhibits hierarchical pore structure with high specific surface area(862.76 m2·g-1)and total pore volume(0.684 cm3·g-1),and abundant organic functional groups.The adsorption equilibrium data of MB on HAC are best fitted to the Redlich-Peterson.The kinetic data show that the pseudo-first-order model is more suitable at low MB concentration,while the advantages of the pseudo-second-orderand the Elovich models are more obvious as the concentration increases.According to the thermodynamic parameters,the HAC-MB adsorption process is spontaneous and endothermic.

Characteristics of dissolved inorganic carbon in produced water from coalbed methane wells and its geological significance

Based on long-term dynamic tracing of dissolved inorganic carbon(DIC)and stable carbon isotope(δ13CDIC)in produced water from 20 coalbed methane(CBM)wells in western Guizhou,the spatial-temporal dynamic variations ofδ13CDIC of the GP well group produced in multi-layer commingled manner were analyzed,and the relationship between the value ofδ13CDIC and CBM productivity was examined.The produced water samples of typical wells in the GP well group were amplified and sequenced using 16S rDNA,and a geological response model ofδ13CDIC in produced water from CBM wells with multi-coal seams was put forward.The research shows that:δ13CDIC in produced water from medium-rank coal seams commonly show positive anomalies,the produced water contains more than 15 species of methanogens,and Methanobacterium is the dominant genus.The dominant methanogens sequence numbers in the produced water are positively correlated withδ13CDIC,and the positive anomaly of v is caused by reduction of methanogens,and especially hydrogenotrophic methanogens.Vertical segmentation of sedimentary facies and lithology in stratum with multi-coal seams will result in permeability and water cut segmentation,which will lead to the segmentation ofδ13CDIC and archaea community in produced water,so in the strata with better permeability and high water cut,theδ13CDIC of the produced water is abnormally enriched,and the dominant archaea is mainly Methanobacterium.In the strata with weak permeability and low water cut,theδ13CDIC of the produced water is small,and the microbial action is weak.The shallow layer close to the coal seam outcrop is likely to be affected by meteoric precipitation,so theδ13CDIC of the produced water is smaller.The geological response model ofδ13CDIC in produced water from multi-coal seams CBM wells in the medium-rank coal reveals the geological mechanism and microbial action mechanism of theδ13CDIC difference in the produced water from the multi-coal seams CBM wells.It also provides effective geochemical evidence for the superimposed fluid system controlled by sedimentary facies,and can also be used for the contribution analysis of the produced gas and water by the multi-layer CBM wells.

Main factors influencing the expulsion of oil derived from coal

THE expulsion of hydrocarbons from coal is controlled by two main factors. The first is theproperties inherited from coal itself and contains two implications. One is original potential ofhydrocarbon generation from coal, which determines the degree of oil-bearing saturability;

Expulsion and primary migration of the oil derived from coal

The characteristics of coal pores and the interaction relationship between hydrocarbons and pores in coal are analysed based on the typical example of oil from coal in Tuha Basin, pointing out that the interaction between hydrocarbon molecules and coal pore surface particles is a major controlling factor of expulsion of oil from coal. Distribution characteristics of coal pores and the ability of hydrocarbon generation are inner factors of the expulsion of the oil from coal; tectonic compressive shear stress is an external force of the expulsion of oil from coal; expulsion of the oil from coal has greater geochromatographic effect than that from mudstone, the low mature stage (or vitrinite reflectance R\-o is less than 0.9%) is advantageous to the coal-formed oil expulsion and migration; hydrocarbons in the hydrocarbon network are linked with carrier beds (such as fault), through the pore network and fissure which are connected with each other, which constitutes the main pathway of expulsion and migration.

New concept on coal structure and new consideration for the generation mechanism of oil from coal

The traditional two_phase structural model of coal based on the chemical covalence bonding has to be revised since recent discoveries of powerful mixed solvent such as CS-2/C-5H-9N, giving extra high yields in coal extraction at room temperature. It is believed that the physically associated interactions play important roles in the structure of coal. A composite model of coal is suggested. The organic matter of coal is mainly composed of some parts: the rigid 3_D macromolecules linked with chemical bonds; the polar molecules of high and moderate molecular weights, corresponding to asphaltenes and resins; the hydrocarbons with lower molecular weights. The polar molecules are associated by physical interactions (such as hydrogen bonding, charge transfer interactions, π_π interactions of aromatic sheets, etc.) each other and with macromolecules to form the network structure, in which some smaller nonpolar molecules are trapped. Based on the new concept of the composite coal model, some considerations for the generation mechanism of oil from coal have approached. Since the energy level of physical association is much lower than the chemical covalent bonding, the upper threshold of oil window for the generation of oil from coal seems not to be limited strictly after the theory of oil generation at the latter stage of the kerogen maturation. It looks reasonable to pay more attention to the geological conditions including the salt, water, minerals and environments of the sedimentation. The evolution process of physically associated interactions in the composite structure of coal and the generation of oil is thought to be intimately influenced by these factors.

Types of Organic Fades and Source Rock Assessment of the Coal-Measure Mudstone in the Turpan-Hami Basin

This paper discusses the enviromental characteristics of carbonaceous mudstone and mudstone (coal-measure mudstone in short) of the Early and Middle Jurassic in the Turpan-Hami basin, which were formed in swamps. Through the organic facies study of the coal-measure mudstone in this area, the authors clarify that the flowing-water swamp is the most advanced organic facies belt. Furthermore, according to the practical materials of coal-measure mudstone in the area and with the evaluation criteria of lacustrine mudstone in the past, the authors have established the integrated symbol systems from the abundance of organic matter and the type of organic matter, which can be used in the source rock evaluation of the coal-measure mudstone.

煤层采动底板突水物理模拟试验研究进展与展望

【目的】底板突水受特定地质构造、水-岩-应力及采掘扰动等因素叠加作用影响,具有复杂性、隐蔽性、突发性等特点。【方法】物理模拟试验能较好地还原底板岩层与承压水赋存环境、直观展现采动底板裂隙扩展及突水路径演化全过程、实时获取灾变各阶段多源数据信息,因而在底板突水研究方面具有独特优势。【结果和结论】对底板突水经典理论、标准规范、模拟试验及工程实践等方面的研究成果进行了回顾,重点梳理了试验加载装置及水压模拟方式、相似材料研制及其特性指标、监测技术及其观测系统设计3个方面的研究进展,其中在模拟水-岩-应力耦合环境下的三维模型底板突水全过程信息捕捉方面有较大突破。面对数智化研究大背景,分析当前底板突水物理模拟试验领域存在的不足,并据此指出未来应重点关注大型三维底板突水综合试验平台研制、基于标准化的多特性相似材料配比数据库建立、多相多场多维耦合监测预警系统构建、人工智能等数智化技术融合应用研究等发展方向。提出的思考有助于从装置、材料、技术等方面提升未来物理模拟试验水平,从而更好支撑煤矿底板水害数智化防治基础研究工作高质量发展。

ML-QSPR方法预测煤基液体的燃料性能

煤基液体混合物如煤焦油、煤直接液化油的分子结构描述和性质预测是开发煤基液体产品高值化工艺和技术的重要基础。由于煤基液体主要由C、H、O、N、S元素构成数量庞杂、芳环结构各异的混合物,因此,使用Python中的RDKit工具包,利用简化分子线性输入规范(Simplified Molecular Input Line Entry System,SMILES)语言构建煤基液体中物质分子描述符,描述符包含样品元素信息、环数与环结构信息、原子数及分子量信息等共计115个分子描述符。对比人工信息提取方法,将所构建的分子描述符能够体现煤基液体分子结构碎片、分子量及原子个数信息等作为机器学习的特征输入变量,用于建立预测煤基液体的燃料性能的分子机器学习-定量结构性质关系方法 (ML-QSPR),实现对燃料低位热值(LHV)、液体密度(ρ)、闪点(FP)、十六烷值(CN)4个关键燃料性能参数的快速预测。模型验证分析表明LHV、ρ、FP模型的R^(2)分别为0.996、0.988、0.987;CN预测中加入混合物数据进行预测,R^(2)=0.959。与已公开报道的预测LHV、ρ、FP、CN性质方法对比,笔者提出ML-QSPR方法在预测4个关键燃料性能参数准确度方面有提升,在获取结果速度方面有显著优势。利用ML-QSPR模型预测得到的煤基液体制特种燃料性能参数数据库中的信息,分析增加不同族组分物质的碳原子数量时4个燃料性能参数的演变趋势,发现LHV、ρ、FP、CN四个燃料性能参数均受碳数(n)影响显著。由于LHV主要由n决定,不同族组分物质的LHV差距小;而不同族组分物质的ρ、FP和CN性质差距明显。此外,本研究训练好的模型可用于预测新的分子,为新型燃料分子设计提供参考;ML-QSPR方法作为迁移学习模型可在今后用于煤基液体其他场景相关理化性质的分析。

煤制甲醇虚拟仿真实验操作评分系统优化

为解决化工及相关专业实习难、实验“两性一度”不足的问题,郑州大学于2010年开始建设了国内首套煤制甲醇虚拟仿真实验系统,并开设了相关课程。为提高煤制甲醇虚拟仿真实验教学质量,针对其操作评分系统中普通步骤操作分占比过高,质量步骤操作不细的问题,通过优化,大大提高了实验的挑战度和操作质量的区分度,调动了学生的积极性。通过该实验培养了学生的工程素养和运用专业知识分析问题的能力,为新工科建设提供了有利支撑。

井下动水截流施工骨料堆积生长机制研究

灌注骨料形成阻水屏障实现截流降速是井下治水工程的关键所在。为定量描述骨料堆积生长的时空演化机理,提出了将骨料沉降堆积过程切分为具有一定厚度的片状颗粒层堆叠过程的分析计算方法,以及动水环境中骨料灌注后从沉降到堆积全过程关键参量(颗粒水平移距xd,动水休止角ψ,未接顶区流速U,骨料留存临界流速U_(cr))的理论计算公式,在此基础上构建了骨料堆积体生长预测模型。通过CFD-DEM双向耦合算法研究了骨料灌注期间流场分布演化特征和骨料堆积形态差异,并验证了预测模型合理性。研究表明:空间上,依据初始流速U_(s)是否超过骨料起动流速U_(c)或骨料留存临界流速U_(cr),可将截流初期骨料沉积主域的所在位置划分为3个区域,若沉积主域位于③区,则将其视为无效灌注;时间上,骨料堆积体生长过程可归结为3个阶段:高度快速增长阶段、高度长度同步生长阶段、仅水平向伸长阶段;初始流速决定了第1阶段的有无,而灌注条件(骨料粒径、灌注速度)主导着第1阶段所持续的时间;基于泥沙运动力学中推移质输沙率、起动流速等概念,得出了堵孔现象发生及骨料能否留存的临界判据;数值模拟试验结果表明,预测模型能够较好地刻画骨料灌注后的堆积生长规律,骨料堆积稳定后,理论计算值与模拟试验值相对误差小于10%。

煤岩体突水通道骨料灌注运移堆积机制试验

为揭示突水通道中骨料运移堆积的演化规律,开展了动水条件下骨料灌注试验,得到了骨料的初始沉积位置、堆积体形成方向以及堆积体极限堆积高度与水流速、骨料灌注速度等影响因素的内在关联。结果表明:在1.0 m/s高流速动水环境中,骨料堆积体形成方向为先逆水流方向生长至投料孔底后转为顺水流方向生长;在0.3 m/s低流速条件下,采用口径36 mm漏斗投料同口径18 mm相比,骨料灌注总量相同时,其堆积体的极限高度提升了41%。基于数值力学模型——计算流体动力学-离散元方法(computational fluid dynamics and distinct element method,CFD-DEM),研究了骨料灌注期间突水通道内流场的时空分布特征以及骨料堆积体的过水阻力作用对突水通道内静水压力的影响机制。

特厚煤层底板断层破坏与顶板垮断联动效应的CFDEM模拟研究

特厚煤层采场空间大、覆岩扰动范围广,顶板垮断产生的强扰动加卸荷载易导致底板断层破坏加剧。通过数值模拟研究特厚煤层底板断层突水与顶板垮断联动效应机理规律是开展水害防治的基础,关键在于掌握加卸载下岩体渐进破坏与裂隙流耦合特征。构建加卸载下拉、剪损伤演化方程,结合有效偏/球应力为基本变量的屈服准则与塑性势函数,得到完整岩块的塑性损伤本构;建立拉/剪、混合型加卸载过程中塑性位移与强度劣化关系,以平方拉剪应力与B-K准则为初始、完全断裂准则,形成非贯通裂隙断裂本构;提出岩块分离、压缩、剪切判据,结合实验数据建立离散块体间挤压、剪切摩擦本构与剪胀方程。基于质量/动量守恒、状态方程,并结合流体体积与浸没边界方法,形成裂隙岩体气−水二相流模拟理论。由此形成CFDEM数值计算程序,并将加卸载下塑性损伤、断裂、挤压/摩擦、流体属性分别赋予实体单元(岩块)、黏聚力单元(非贯通裂隙)、接触对(贯通裂隙)、欧拉单元(水和气)。根据宁武煤田北部矿区工程地质条件,建立特厚煤层底板断层突水与顶板垮断联动效应数值计算模型。结果表明:①CFDEM耦合程序及相应的理论模型可数值实现特厚煤层覆岩及底板断层从(准)连续体到离散体转化,以及地下水在裂隙中运移;②模拟条件下特厚煤层含断层底板的采动裂隙包络线呈w形,最深处超过55 m位于断层及其上盘,最浅处23 m位于断层下盘,而无构造底板处的破坏深度为24~36 m,已导通奥灰含水层;③特厚煤层底板普遍出现二次破坏现象。表现为无构造底板在超前工作面处破坏深度为24.0~29.3 m,但在采空区内普遍增加至31.5~36.0 m;断层及其上盘在超前工作面处裂隙总开度为0.34~0.86 m,但在采空区内迅速增加至3.6 m,形成突水优势通道。④底板断层突水与顶板垮断联动效应的根源在于覆岩高位关键岩层垮断失稳、砌体梁下沉与二次断裂,并导致底板二次破坏,突水风险加剧。

煤直接、间接液化柴油及其混合燃料液滴的蒸发特性

为研究煤直接和间接液化柴油(DDCL、DICL)及其混合燃料液滴在不同环境温度下(500、600和700℃)的蒸发特性,利用基于悬挂法的液滴蒸发试验装置,采用交叉石英丝悬挂液滴,通过燃料设计方法,将DDCL和DICL按29∶21的质量比混合后可获得与柴油理化特性非常相近的燃料.研究显示,DDCL、DICL及其混合燃料液滴蒸发规律与柴油相似,均呈现两阶段蒸发.在600℃以下与经典d^(2)定律(d为液滴直径)存在较大偏差,随环境温度的升高,与d^(2)定律的偏差逐渐缩小.在以上3种环境温度下,混合燃料液滴均表现出的蒸发性能优于柴油,分别比柴油的平均蒸发速率高27.2%、46.3%和19.6%.研究结果为煤液化柴油在柴油机上的应用提供支撑数据.

底板突水危险性评价研究进展

回顾了煤层底板突水危险性评价的发展历程,提出其危险性评价的体系:指标(指标体系的建立)—方法(评价方法的选取)—工具(处理工具的革新),并对3个环节进行总结。指出指标体系的发展不再是因素集的扩充,而是因素与因素之间非线性关系的处理以及对以开采条件及地质条件为两大基本要素集的化繁为简;将现有方法依据处理数据的逻辑分为3类:以数据的基础信息为基准,将原始数据对评价对象所产生的大小、高低、优劣性影响进行考量、排序及综合形成评价结果的第一类方法;对数据列进行人工评判、加工分析、拓展和延伸,挖掘数据的潜在信息,并形成最终评价结果的第2类方法;整理具有相同指标的数据集,通过数据信息处理技术发现数据间的共有信息,从而获得最终评价结果的第3类方法。指出未来评价方法的发展方向一方面是对突水系数法的传承,修正其在厚、巨厚、极薄隔水层的不良表现,另一方面是对机器学习新型方法的创新,对其本身及组合模型进行开发与应用。提出了处理工具所需实现的三大目标:矿井立体化模型的建立、评价结果的动态化演示、“定位、定量、定概率”三定指标的实现。分别探讨了三者面临的问题并阐述具体解决手段。在上述基础上,总体阐明了煤层底板突水危险性评价体系各环节的研究展望。

矸石电厂粉煤灰薄喷材料制备及性能研究

为实现矸石电厂粉煤灰的综合利用,在分析了陕西黄陵矸石电厂粉煤灰理化性能基础上,研究粉煤灰掺量、胶沙比、粉煤灰质量分数对薄喷材料流动性能及抗压强度的影响规律。通过正交实验确定了矸石电厂粉煤灰薄喷材料基础配比,并采用扫描电镜(SEM)对薄喷材料1、28 d龄期的微观结构进行表征。通过外加剂对材料流动性能进行调控,揭示了调控机理。研究结果表明,当粉煤灰∶水泥(质量比)为6∶1,胶沙比(质量比)为1.0∶1.2,粉煤灰质量分数为77%,聚羧酸减水剂掺量为0.5%(质量分数),SD-WJ40液体无碱速凝剂掺量为11%(质量分数)时,薄喷材料性能满足混凝土基层喷浆处理技术规程要求。

EACD技术处理煤矿酸性废水硫酸根的研究

采用·OH清除剂优化接地极雾化电晕放电(EACD)技术处理煤矿酸性废水,利用响应面法研究了放电电压、放电时间和硫酸根与苯酚的浓度比对硫酸根降解率的影响。结果表明,各因素显著性顺序为:硫酸根与苯酚的浓度比>放电电压>放电时间,放电电压、硫酸根与苯酚的浓度比的交互作用对硫酸根去除率影响显著。优化条件为:放电电压12 kV、放电时间66 min、硫酸根与苯酚的浓度比0.9时,对应的硫酸根去除率为76.55%,与预测值仅有0.55%的误差。实验结果与模型数值高度吻合,证实了该回归模型的准确性。

基于微震监测技术的煤矿底板突水预警研究

煤矿底板突水是矿山生产中的主要灾害之一,其破坏性极大,因此,研究有效的突水预警技术具有重要意义。以董家河煤矿22517工作面为例,构建了微震监测系统,并对底板进行突水预警。监测数据显示,该煤矿的底板微震事件总共有191个,其中能量超过1000 J的微震事件仅为18个,占全部微震事件的9.63%,同时,该系统检测到的底板破坏深度约为11.01 m,与底板钻孔声波仪测试计算的数据仅相差0.22 m。这些数据可以说明研究所提出的微震监测技术能够有效预测煤矿底板的突水事故,起到了良好的预警作用,为煤矿开采作业的水害风险防范提供了可靠的技术支持。

煤制氢、天然气制氢及绿电制氢经济性分析

氢气是人类利用的最轻元素。作为能源载体,氢气被称为未来的清洁能源。目前,通过化石能源煤炭、天然气制取的氢气为灰氢,灰氢叠合CCUS技术后可得到蓝氢,绿氢由绿电(光电、风电)转化的电能直接电解水得来,最具代表的是绿电电解水制氢。文中主要分析煤制氢、天然气制氢及绿电制氢主流制氢技术的资源消耗量与经济性,随着碳税开征,绿氢成本会远低于蓝氢、灰氢,未来绿氢在氢能市场上最具商业竞争力,会获得越来越多的重视。