Pore Fractal Dimensions of Bituminous Coal Reservoirs in North China and Their Impact on Gas Adsorption Capacity

Natural Resources Research - Coal pores not only serve as the storage space for coalbed methane but also provide channels for gas migration. The accurate characterization of coal pore structures is...     

耕地生产力与粮食安全耦合关系与趋势分析——以河南省为例

粮食是社会经济发展的重要保障。运用耕地、粮食安全测度模型对2005~2014年河南省粮食安全状况进行评估。结果表明：① 2005~2014年,农民种粮积极性上升10%,耕地压力指数下降71%,农民经济收益上升 13%,耕地重心向西南移动。 ② 不同指标对耕地生产力的贡献率具有差异性。2005~2009年粮种比对耕地生产力的贡献率最大,2010~2014年贡献率发生转移,粮食播种面积单位产量对耕地生产力的贡献率最大;10 a间,粮种比的贡献（69.77%）相对粮食单产的贡献（39.28%）更能促进河南省耕地生产力的提高。 ③ 耕地压力受到自然、社会等多方面因素影响。各指标间相关关系较强,种粮积极性与农民耕地保护能力的二者呈现负相关关系。     

阿拉尔河悬浮物对铀的吸附影响研究

为了解阿拉尔河悬浮物对铀的吸附特性,通过静态吸附实验,研究了吸附时间、pH值、温度和铀初始浓度等因素对模拟含铀水中U(VI)去除率的影响,并从热力学和动力学方面对吸附过程进行了分析。结果表明,在T=25℃,溶液初始pH=7,接触时间为16 h时,悬浮物对铀的平衡吸附率最佳,为95.48%。随着铀初始浓度的增加,吸附量增加,但吸附率随之下降,升高温度有利于铀的吸附。铀在悬浮物上的吸附过程符合Langmuir等温吸附方程,说明悬浮物对铀为单分子层吸附,且化学吸附占主导地位。吸附动力学过程可用准二级吸附动力学模型描述,表明吸附主要受动力学控制,由两个以上步骤共同控制。FTIR和EDS分析结果表明,吸附过程中铀主要与悬浮物表面活性基团螯合并以表面络合吸附为主。吸附前后的能谱对比分析表明,吸附过程中存在离子交换行为。因此,悬浮物对铀的吸附机理是以表面络合吸附和离子交换为主、物理吸附为辅的混合吸附过程。     

Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals

Characterization of coal micro-structure and the associated rock mechanical properties are of key importance for coal seam exploration, coal bed methane development, enhanced coal bed methane production and CO₂ storage in deep coal seams. Considerable knowledge exists about coal chemical properties, but less is known about the nanoscale to the micro-scale structure of coals and how they change with coal strength across coal ranks. Thus, in this study, 3D X-ray micro-computed tomography (with a voxel size of 3.43 µm) and nano-indentation tests were conducted on coal samples of different ranks from peat to anthracite. The micro-structure of peats showed a well-developed pore system with meso- and micro-pores. The meso-pores essentially disappear with increasing rank, whereas the micro-pores persist and then increase past the bituminous rank. The micro-fracture system develops past the peat stage and by sub-bituminous ranks and changes into larger and mature fracture systems at higher ranks. The nano-indentation modulus showed the increasing trend from low- to high-rank coal with a perfect linear relationship with vitrinite reflectance and is highly correlated with carbon content as expected.

     

Experimental Study on the Effect of Moisture Content on Bituminous Coal Porosity Based on 3D Reconstruction of Computerized Tomography

Bituminous coal in the Xutuan Coal Mine of the Huaibei Mining Bureau (China) is the research object of this study. The influence of moisture content on the porosity of the bituminous coal was investigated from a microscopic perspective by using a high-solution 3D X-ray micro-analyzer. The threshold segmentation method was used to segment the scanning slices of the coal samples. The threshold values of the various media were in the following order (from large to small): minerals, water, matrices, and fractures. The scanning volume and actual volume proportions of the different media in the coal samples with different moisture contents were calculated. The accuracy of the computerized tomography (CT) scanning method in measuring the coal moisture content was verified by comparison with the results obtained using the weighing method. 3D reconstructed coal samples, with different moisture contents, were analyzed, as well as separately reconstructed fractures and water in the coal samples with different moisture contents. The heterogeneity and anisotropy of the coal mass were explained quantitatively by the CT scanning intensity. A commonly used fracture classification method indicated that the primary fracture in the coal sample was a type A fracture. The results of the analysis of water in the coal fracture indicated that the porosity of bituminous coal decreased with the increase in moisture content in conditions of atmospheric pressure and a short immersion period. However, a certain level of porosity remained evident, and the degree of fracture development of the coal samples remained unchanged. This is attributed to the minor volumetric change in the minerals in the coal samples, as the water does not completely occupy the fractures in the coal samples, and the dissolution of the minerals by water is therefore not significant. The reasons for the moisture content affecting gas adsorption, seepage, and strength of a coal body were analyzed from a microscopic perspective. In addition, the types of fractures and water in the coal samples were classified by employing statistics and analyses of volume, surface area, specific surface area, and aspect ratio of the fractures and the water in the coal samples with different moisture contents.

     

Numerical Simulation Analysis of the Permeability Enhancement and Pressure Relief of Auger Mining

Auger mining (AM) is an effective and safe way to excavate an extremely thin protective layer. This method can relieve pressure and enhance the permeability of an ultra-contiguous coal layer with high gas capacity. However, there have been few studies on AM. Based on the conditions of a coal mine in Shanxi Province, China, theoretical analyses, laboratory tests and numerical simulations were used to analyze the evolution law of the overburden permeability in an AM face. A stress–damage–permeability coupling model was proposed, and a numerical simulation algorithm for fluid–solid coupling with FLAC software was established. Through this method, the evolution law of stress and permeability and its influencing factors of the overburden of the AM face were found. The intermediate coal pillar (ICP) width and the AM height and length are the main factors influencing the permeability evolution of the AM face. The first factor determines the damage state of the ICP in the goaf, and the last two factors influence the zone size with permeability enhancement of the protected layer. Therefore, reasonable AM parameter design is the key to both safe mining operations in the AM face and pressure relief and permeability enhancement.

     

活性碳纤维吸附水中酚及脱附条件实验研究

化工、医药等行业排出的含酚废水对环境造成的污染十分严重,其废水的处理日益受到重视。活性炭纤维(Activated Carbon Fibers,ACF)作为一种新型吸附材料,其具有的大比表面积、丰富微孔结构等特点,使其吸附过程效率高。并且其吸附操作设备具有简单、方便、能耗低等优点,从而使该吸附法成为近年来一种快速发展的废水处理方法。本研究通过静态条件下的吸脱附性能研究,研究了ACF吸附水中酚的规律,确定了最佳的吸附时间为4 h,水溶液pH为弱酸性及低温有利于吸附的结果,得到了准确的平衡吸附量;找到了合适的ACF脱附再生剂NaOH,并测试出其多次再生的利用率。     

A Novel Method to Obtain Permeability in a Dual-Pore System Using Geophysical Logs: A Case Study of an Upper Triassic Formation,Southwest Ordos Basin,China

Fractured tight sandstone reservoirs are dual-pore systems including matrix pores and natural fractures, which both contribute to the system permeability. However, most previous studies either calculated the matrix permeability or obtained the fracture permeability to represent the system permeability in the logging evaluation of fractured tight sandstones because existing logging methods cannot distinguish the two types. In this study, a novel method is proposed to estimate the system permeability in fractured tight sandstones using geophysical logs. First, the fracture characteristics in the Upper Triassic Chang 8 member of the Yanchang Formation, southwest Ordos Basin, China, were analyzed. Based on the hydraulic flow unit approach, the formation classification criteria and the corresponding permeability–porosity models were established; then, the pure matrix permeability in the dual-pore system was calculated using geophysical logs. Based on the fracture characteristics, the relative pure fracture permeability was obtained using the Sibbit and Faivre method. By applying the Parsons’ model in boreholes, the system permeability was then calculated by coupling the relationship between the two permeabilities. Finally, two field applications in the study area demonstrate the feasibility of the proposed method, and the logging responses, application effects and applicable conditions of this method are discussed in detail. These applications indicate that the proposed method is suitable for tight reservoirs with fracture widths less than 200 μm, and considered to be dual-pore systems.

     

农业化肥减量及生物肥料替代可行性研究——来自新疆棉区调查数据的实证

推进化肥减施增效是实现中国农业绿色高质量发展的关键途径。本文以新疆棉花为例,基于2000—2020年棉花化肥施用量及技术、资本、劳动力投入时序数据,构建生产函数考察了新疆棉花单位面积化肥施用强度变化及其对棉花单产提升的贡献作用,并利用2015—2020年不同植棉区化肥和生物肥料施肥区的微观定位调查数据,采用熵权法构建肥料应用效益评价指标体系,对两种肥料的综合效益做出总体评判,并对经济效益（棉花产量、黄萎病害发生率）和生态效益（土壤有机质、微生物数量）及两种肥料施用成本进行具体比较,探讨了生物肥替代化肥的可行性及其实现机制。研究表明：① 2000—2020年间新疆棉花单位面积化肥施用强度呈不断上升态势,高于同期国内大部分植棉省份,自2016年起趋于减缓和平稳,施肥量浮动在585 kgN/hm²左右。② 2000—2010年随着单位面积化肥施用强度的增加,对棉花单产增加呈正向促进作用;而2010—2020年,单位面积化肥施用强度增加对棉花单产提高的贡献率为-21.29%,表明持续增加化肥用量对棉花单产提高已呈现负效应。③ 生物肥料施肥区生态效益优势更突出,但经济效益低于化肥区,两种肥料的综合效益随使用年限增加差距趋于缩小;较化肥组,研究期内不同植棉区生物肥组棉花单产降低3%~8%,黄萎病害发病率降幅27.75%~58.20%,土壤有机质含量提高了14.59%~28.54%,土壤微生物数量显著增加;生物肥单位施用成本高于化肥14%~19%。根据生物肥生态属性及作用机理,结合农户经济理性及传统的化肥依赖,建议在生物肥推广初期,实行一定的政策激励或生态补偿,同时积极引导和培育农户亲环境意识,农业化肥逐步减量及生物肥替代具有理论与实践可行性。     

黄河流域城市化与生态系统服务价值协调性及障碍因素研究

关注生态系统服务价值(Ecosystem service value,ESV)与城市化耦合协调互动关系,对黄河流域高质量发展大有裨益。文章运用熵权法、耦合协调模型、空间自相关模型,障碍度模型分析了城市化与ESV的耦合协调关系及主导障碍因素。结果表明:(1)1995—2018年,黄河流域ESV发生了很大的改善,整体增加了33.05×10⁹元,且以调节服务为主导,草地、林地、耕地服务价值对总ESV贡献率较高。单位面积生态系统服务价值(PE)呈现南高北低、中游高上下游低的空间格局。(2)PE与城市化耦合协调度(Coupling coordination degree,CCD)逐渐改善,轻度耦合协调增加了27.12%,严重失调类型减少了45.46%,耦合亚型从城市化滞后型转变为ESV滞后型;从空间上看,CCD呈现南高北低、中游优于上游和下游的空间格局,协调度具有显著的空间正相关性,存在明显的高-高和低-低集聚特征,高-高集聚区主要分布在ESV高且城市化水平相对较高的中游和下游地区,低-低集聚区主要分布在ESV较低的上游地区。(3)1995—2018年主导障碍因素未发生明显...     

Influence of Local Frequent Dynamic Disturbance on Micro-structure Evolution of Coal-Rock and Localization Effect

This study aimed to investigate the influence of local frequent dynamic disturbance on micro-structure evolution in different zones of coal-rock. To do so, we carried out a systematic experimental research on the micro-structure evolution of briquette and raw coal samples under local impact load by using self-developed pendulum hammer dynamic impact loading test device of coal-rock and ultrasonic testing equipment, and analyzed the localization effect of local impact load. The results show that M_n (micro-structure cumulative change factor) of briquette coal samples presents an inclined M-shaped four-stage evolution mode along and perpendicular to impact direction with cyclic impact times under conventional full impact load, whereas it shows more obvious anisotropy and localization under local impact load. M_n for both conventional full impact and local impact shows a nonlinear increasing trend with the increase in impulse, but their increasing gradients are different. The critical zone is the most affected, the impact zone comes next, and the non-impact zone is the least affected with the increase in impulse under local impact load. M_n in the impact zone and critical zone decreases exponentially with the increase in the impact loading area, while it increases exponentially in the non-impact zone. The micro-structures evolution in briquette and raw coal samples is similar, but the anisotropy and localization effect of micro-structure evolution for raw coal samples are more significant and more sensitive to the impact loading area. The micro-structure evolution of coal-rock under local impact load shows obvious localization effect. M_n in the critical zone is usually the largest, M_n in the impact zone is slightly less than that in the critical zone, and M_n in the non-impact zone is the least. The larger the impact loading area, the wider the influence enhancement area, and the smaller the non-influence area, yet the smaller the impact zone and critical zone are affected by local impact load.

     

Assessment of Rockburst Risk in Deep Mining: An Improved Comprehensive Index Method

With the increasing depth of underground engineering, the risk of coal–rock dynamic disasters such as rockburst is becoming more and more serious and complex, which seriously threatens the safety of coal resource, mine production and the surface ecological environment. However, the existing risk indices and methods used for evaluating rockburst risk cannot be fully applied to deep goal seam group (DCG) mining. For the safe exploitation of coal resources, in this paper, based on statistical analyses of 300 cases of rockburst, six new indices are proposed for evaluating rockburst risk in the DCG, namely dip angle, moisture content, stability of coal seam, advancing speed of working face, disturbance factors and support patterns. In addition, the influence of multiple factors coupling and superposition on rockburst risk was considered. Thus, the Comprehensive Index Method of rockburst risk of Deep Coal seam Group (DCG–CIM) based on analytic hierarchy process was established. Finally, rockburst risk in the evaluation area was quantitatively assessed into four grades, including “No rockburst risk”, “Weak rockburst risk”, “Medium rockburst risk” and “Strong rockburst risk”. Taking the 2233 working face of Hengda Coalmine as an example, the evaluation results show that the ranges of 0–184 m, 224–284 m, 324–384 m, 424–484 m, 524–584 m and 594–624 m from terminal line of haulage roadway on 2233 working face were the medium rockburst risk zones, which are in accordance with the on-site impact damage results and are more accurate than the traditional method. The DCG–CIM can consider more inducing factors and obtain more accurate and reliable evaluation results and is more suitable for deep coal seam group mining.

     

基于GIS栅格数据的空间模糊综合评判方法与实践

针对模糊综合评判多集中于对区域整体的综合评判的局限,提出了基于GIS的空间模糊综合评判方法。介绍了该方法的关键内容——隶属层的形成过程以及基于栅格数据的综合运算方法,并将该方法应用于门头沟煤矿区生态环境综合评价。     

Spatial coupling analysis of regional economic development and environmental pollution in China

Given the great number of studies focusing on the temporal interaction between economic and environmental subsystems, it is useful to perform a quantitative spatial assessment of these subsystems. In this paper, comprehensive assessment indicators for regional economic development and environmental pollution subsystems are constructed. Then, the degree of coupling and coordination of the regional economy-environment system is calculated for 350 prefectural units in China. It is found that the economic development and environmental pollution in most prefectural units is still at a low level of coupling and coordination. According to the coupling and coordination values, the Chinese territory can be divided into four types of area: economy-environment harmonious area, economy-environment gearing area, economy-environment rivaling area and low coupling degree of economy-environment area. Based on a structural analysis of the industrial sector in the four types of areas, there is a spatial relationship between the regional industrial sector structure and the coupling-coordination level. In the economy-environment harmonious area, the sectors of manufacturing of high-technology and high value-added products, such as communications, computer and electronic equipment, transport equipment and electrical machinery, account for a large proportion of the value of local industrial output. The industrial value of the economy-environment gearing area is concentrated on the manufacturing of machinery and equipment, and contains a few polluting sectors such as ferrous and non-ferrous metallurgy, chemical manufacturing and electricity generation. The economy-environment rivaling area is the type of area where polluting sectors concentrate, such as iron and steel, petrifaction, coal mining, building materials and electricity generation. In the low coupling degree of economy-environment area, its industry is concentrated on the production and processing of primary products.     

Gas Flow Characteristics and Optimization of Gas Drainage Borehole Layout in Protective Coal Seam Mining: A Case Study from the Shaqu Coal Mine,Shanxi Province,China

With increasing demands for coal resources, coal has been gradually mined in deep coal seams. Due to high gas content, pressure and in situ stress, deep coal seams show great risks of coal and gas outburst. Protective coal seam mining, as a safe and effective method for gas control, has been widely used in major coal-producing countries in the world. However, at present, the relevant problems, such as gas seepage characteristics and optimization of gas drainage borehole layout in protective coal seam mining have been rarely studied. Firstly, by combining with formulas for measuring and testing permeability of coal and rock mass in different stress regimes and failure modes in the laboratory, this study investigated stress–seepage coupling laws by using built-in language Fish of numerical simulation software FLAC^3D. In addition, this research analyzed distribution characteristics of permeability in a protected coal seam in the process of protective coal seam mining. Secondly, the protected coal seam was divided into a zone with initial permeability, a zone with decreasing permeability, and permeability increasing zones 1 and 2 according to the changes of permeability. In these zones, permeability rises the most in the permeability increasing zone 2. Moreover, by taking Shaqu Coal Mine, Shanxi Province, China as an example, layout of gas drainage boreholes in the protected coal seam was optimized based on the above permeability-based zoning. Finally, numerical simulation and field application showed that gas drainage volume and concentration rise significantly after optimizing borehole layout. Therefore, when gas is drained through boreholes crossing coal seams during the protective coal seam mining in other coal mines, optimization of borehole layout in Shaqu Coal Mine has certain reference values.

     

新型复合生物质锂吸附剂的制备及吸附性能研究

以KMnO₄、苯胺、LiOH和生物质碳气凝胶(BCA)为原料,通过水热沉积法得到了锰酸锂(LMO)负载的生物质碳气凝胶(BCA@LMO),并用HCl酸洗后得到了BCA@HMO复合锂吸附剂。利用IR、XRD、XPS、SEM、EDS、Mapping、BET等手段对其结构进行了表征。考察了pH值、离子强度、初始浓度、温度和吸附时间对锂吸附的影响。结果表明,复合吸附剂为介孔结构,其孔道内和表面具有丰富的锰酸锂颗粒,Li⁺的最大平衡吸附量在pH=12时为4.07 mmol·g-1,吸附过程符合Langmuir等温线和准二阶动力学模型,升高温度和碱性环境利于Li⁺的吸附。吸附机理为H⁺与Li⁺的离子交换。复合吸附剂较好地改善了锰系锂吸附剂固液分离困难的问题,该吸附剂在实际南翼山盐田和东台吉乃尔盐田卤水(2.92 mmol·g-1)中具有良好的吸附性能。因此,该吸附剂在卤水锂的分离中具有良好的应用价值和潜力。     

原位AlN/AZ91镁基复合材料轧制及热处理工艺研究

对前期制备出的原位AlN/AZ91镁基复合材料进行轧制及热处理工艺研究,利用X-ray衍射仪(XRD)、扫描电镜(SEM)、光学显微镜(OM)、能谱仪(EDS)等对不同轧制及热处理工艺条件下镁基复合材料轧制板材的微观组织进行表征,并对复合材料进行室温拉伸力学性能测试和分析.结果表明:通过优化轧制及热处理工艺,显著改善了...     

沟谷型沙漠泥流堆积体起动过程中的孔压变化特性

以黄河上游宁蒙段典型风水复合侵蚀流域为研究区域,重点针对堆积体堵塞沟道极端条件下的沟谷型沙漠泥流,从堆积体起动成灾的环节入手,开展直槽概化模型试验,并采用基于有效应力原理的流固耦合模型,概化模拟上游暴雨洪水入渗条件下堆积体内孔隙水压力变化特性及其起动过程,从微观角度揭示其成灾机理。结果表明：堆积体起动过程中孔隙水压力与时间呈指数为0.5的幂函数关系;流固耦合作用下堆积体内经历了应力场→体积应变→孔隙率→孔隙水压力→渗流场→塑性应变→屈服破坏的复杂非线性变化过程。