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国际煤炭科学技术学报（英文）
国际煤炭科学技术学报（英文）

季刊

2095-8293

国际煤炭科学技术学报（英文）/Journal International Journal of Coal Science & TechnologyCSCDCSTPCD北大核心
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    Research advances in enhanced coal seam gas extraction by controllable shock wave fracturing

    Chaojun FanHao SunSheng LiLei Yang...
    1-31页
    查看更多>>摘要：With the continuous increase of mining in depth,the gas extraction faces the challenges of low permeability,great ground stress,high temperature and large gas pressure in coal seam.The controllable shock wave(CSW),as a new method for enhancing permeability of coal seam to improve gas extraction,features in the advantages of high efficiency,eco-friendly,and low cost.In order to better utilize the CSW into gas extraction in coal mine,the mechanism and feasibility of CSW enhanced extraction need to be studied.In this paper,the basic principles,the experimental tests,the mathematical models,and the on-site tests of CSW fracturing coal seams are reviewed,thereby its future research directions are provided.Based on the different media between electrodes,the CSW can be divided into three categories:hydraulic effect,wire explosion and excitation of energetic materials by detonating wire.During the process of propagation and attenuation of the high-energy shock wave in coal,the shock wave and bubble pulsation work together to produce an enhanced permeability effect on the coal seam.The stronger the strength of the CSW is,the more cracks created in the coal is,and the greater the length,width and area of the cracks being.The repeated shock on the coal seam is conducive to the formation of complex network fracture system as well as the reduction of coal seam strength,but excessive shock frequency will also damage the coal structure,resulting in the limited effect of the enhanced gas extraction.Under the influence of ground stress,the crack propagation in coal seam will be restrained.The difference of horizontal principal stress has a significant impact on the shape,propaga-tion direction and connectivity of the CSW induced cracks.The permeability enhancement effect of CSW is affected by the breakage degree of coal seam.The shock wave is absorbed by the broken coal,which may hinder the propagation of CSW,resulting in a poor effect of permeability enhancement.When arranging two adjacent boreholes for CSW permeability enhancement test,the spacing of boreholes should not be too close,which may lead to negative pressure mutual pulling in the early stage of drainage.At present,the accurate method for effectively predicting the CSW permeability enhanced range should be further investigated.
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    Understanding poromechanical response of a biogenic coalbed methane reservoir

    Rohit PandeySatya Harpalani
    32-50页
    查看更多>>摘要：Biogenic coalbed methane(BCBM)reservoirs aim to produce methane from in situ coal deposits following microbial con-version of coal.Success of BCBM reservoirs requires economic methane production within an acceptable timeframe.The work reported here quantifies the findings of previously published qualitative work,where it was found that bioconversion induces strains in the pore,matrix and bulk scales.Using imaging and dynamic strain monitoring techniques,the bioconver-sion induced strain is quantified here.To understand the effect of these strains from a reservoir geomechanics perspective,a corresponding poromechanical model is developed.Furthermore,findings of imaging experiments are validated using core-flooding flow experiments.Finally,expected field-scale behavior of the permeability response of a BCBM operation is modeled and analyzed.The results of the study indicated that,for Illinois coals,bioconversion induced strains result in a decrease in fracture porosity,resulting in a detrimental permeability drop in excess of 60％during bioconversion,which festers itself exponentially throughout its producing life.Results indicate that reservoirs with high initial permeability that will support higher Darcian flowrates,would be better suited for coal bioconversion,thereby providing a site-selection criteria for BCBM operations.
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    A critical review on direct catalytic hydrogasification of coal into CH4:catalysis process configurations,evaluations,and prospects

    Shuai YanJun FengShenfu YuanZihong Xia...
    51-85页
    查看更多>>摘要：Coal catalytic hydrogasification(CCHG)is a straightforward approach for producing CH4,which shows advantages over the mature coal-to-CH4 technologies from the perspectives of CH4 yield,thermal efficiency,and CO2 emission.The core of CCHG is to make carbon in coal convert into CH4 efficiently with a catalyst.In the past decades,intensive research has been devoted to catalytic hydrogasification of model carbon(pitch coke,activated carbon,coal char).However,the chemical process of CCHG is still not well understood because the coal structure is more complicated,and CCHG is a combination of coal catalytic hydropyrolysis and coal char catalytic hydrogasification.This review seeks to shed light on the catalytic process of raw coal during CCHG.The configuration of suitable catalysts,operating conditions,and feedstocks for tailoring CH4 formation were identified,and the underlying mechanisms were elucidated.Based on these results,the CCHG process was evaluated,emphasizing pollutant emissions,energy efficiency,and reactor design.Furthermore,the opportunities and strategic approaches for CCHG under the restraint of carbon neutrality were highlighted by considering the penetration of"green"H2,biomass,and CO2 into CCHG.Preliminary investigations from our laboratories demonstrated that the integrated CCHG and biomass/CO2 hydrogenation process could perform as an emerging pathway for boosting CH4 production by consuming fewer fossil fuels,fulfilling the context of green manufacturing.This work not only provides systematic knowl-edge of CCHG but also helps to guide the efficient hydrogenation of other carbonaceous resources such as biomass,CO2,and coal-derived wastes.
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    Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain

    F.AnimahC.KelesW.R.ReedE.Sarver...
    86-101页
    查看更多>>摘要：Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.
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    Effect of long reaction distance on gas composition from organic-rich shale pyrolysis under high-temperature steam environment

    Lei WangRui ZhangGuoying WangJing Zhao...
    102-119页
    查看更多>>摘要：When high-temperature steam is used as a medium to pyrolyze organic-rich shale,water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis,thus affecting the generation law and release char-acteristics of gas products.In this study,based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection,the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and com-pared with other pyrolysis processes.The advantages of organic-rich shale pyrolysis via steam injection are then evaluated.The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest,which is more than 60％.The hydrogen content increases as the reaction distance is extended;however,the rate of increase changes gradually.Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91％to 69.68％and from 63.13％to 78.61％when the steam temperature is 500 ℃ and 555 ℃,respectively.However,the higher the heat injection temperature,the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment(hydrogen concentration＞60％).When the steam pyrolysis temperature is increased from 500 ℃ to 555 ℃,the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm.Compared with the direct retorting process,the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces,respectively.The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment.
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    Chemical looping reforming of the micromolecular component from biomass pyrolysis via Fe2O3@SBA-16

    Yunchang LiBo ZhangXiantan YangBolun Yang...
    120-134页
    查看更多>>摘要：To solve the problems of low gasification efficiency and high tar content caused by solid-solid contact between biomass and oxygen carrier in traditional biomass chemical looping gasification process.The decoupling strategy was adopted to decouple the biomass gasification process,and the composite oxygen carrier was prepared by embedding Fe2O3 in molecular sieve SBA-16 for the chemical looping reforming process of pyrolysis micromolecular model compound methane,which was expected to realize the directional reforming of pyrolysis volatiles to prepare hydrogen-rich syngas.Thermodynamic analysis of the reaction system was carried out based on the Gibbs free energy minimization method,and the reforming performance was evaluated by a fixed bed reactor,and the kinetic parameters were solved based on the gas-solid reaction model.Thermodynamic analysis verified the feasibility of the reaction and provided theoretical guidance for experimental design.The experimental results showed that the reaction performance of Fe2O3@SBA-16 was compared with that of pure Fe2O3 and Fe2O3@SBA-15,and the syngas yield was increased by 55.3％and 20.7％respectively,and it had good cycle stability.Kinetic analysis showed that the kinetic model changed from three-dimensional diffusion to first-order reaction with the increase of temperature.The activation energy was 192.79 kJ/mol by fitting.This paper provides basic data for the directional preparation of hydrogen-rich syngas from biomass and the design of oxygen carriers for pyrolysis of all-component chemical looping reforming.
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    Mechanical properties and acoustic emission characteristics of soft rock with different water contents under dynamic disturbance

    Yujing JiangLugen ChenDong WangHengjie Luan...
    135-148页
    查看更多>>摘要：Uniaxial compression tests and cyclic loading acoustic emission tests were conducted on 20％,40％,60％,80％,dry and saturated muddy sandstone by using a creep impact loading system to investigate the mechanical properties and acoustic emission characteristics of soft rocks with different water contents under dynamic disturbance.The mechanical properties and acoustic emission characteristics of muddy sandstones at different water contents were analysed.Results of experimen-tal studies show that water is a key factor in the mechanical properties of rocks,softening them,increasing their porosity,reducing their brittleness and increasing their plasticity.Under uniaxial compression,the macroscopic damage characteristics of the muddy sandstone change from mono-bevel shear damage and'X'type conjugate bevel shear damage to a roadway bottom-drum type damage as the water content increases.Dynamic perturbation has a strengthening effect on the mechani-cal properties of samples with 60％and less water content,and a weakening effect on samples with 80％and more water content,but the weakening effect is not obvious.Macroscopic damage characteristics of dry samples remain unchanged,water samples from shear damage and tensile-shear composite damage gradually transformed into cleavage damage,until saturation transformation monoclinic shear damage.The evolution of acoustic emission energy and event number is mainly divided into four stages:loading stage(I),dynamic loading stage(Ⅱ),yield failure stage(Ⅲ),and post-peak stage(Ⅳ),the acoustic emission characteristics of the stages were different for different water contents.The characteristic value of acoustic emission key point frequency gradually decreases,and the damage degree of the specimen increases,corresponding to low water content—high main frequency—low damage and high water content—low main frequency—high damage.
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    Synergistic CO2 mineralization using coal fly ash and red mud as a composite system

    Zhenchao YaoYugao WangJun ShenYanxia Niu...
    149-158页
    查看更多>>摘要：CO2 mineralization plays a critical role in the storage and utilization of CO2.Coal fly ash(CFA)and red mud(RM)are widely utilized as CO2 mineralizers.However,the inert calcium species in CFA limit its carbonation capacity,meanwhile the substantial Ca2+releasing of RM is hindered by a covering layer of calcium carbonate.In this study,CO2 mineraliza-tion in a composite system of CFA and RM was investigated to enhance the carbonation capacity.Multiple analyzers were employed to characterize the raw materials and resulting mineralization products.The results demonstrated that a synergis-tic effect existed in the composite system of CFA and RM,resulting in improving CO2 mineralization rate and efficiency.The produced calcium carbonate was ectopically attached the surface of CFA in the composite system,thus slowing down its coverage on the surface of RM.This phenomenon facilitated further releasing Ca2+from the internal RM,thereby enhancing CO2 mineralization efficiency.Meanwhile,the inclusion of RM significantly improved the alkalinity of the composite system,which not only promoted the dissolution of Ca2+of the inert CaSO4(H2O)2 in CFA,but also acceler-ated CO2 mineralization rate.The investigation would be beneficial to CO2 mineralization using industrial solid wastes.
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    Influences of clean fracturing fluid viscosity and horizontal in-situ stress difference on hydraulic fracture propagation and morphology in coal seam

    Gang WangShuxin WangYixin LiuQiming Huang...
    159-175页
    查看更多>>摘要：The viscosity of fracturing fluid and in-situ stress difference are the two important factors that affect the hydraulic fracturing pressure and propagation morphology.In this study,raw coal was used to prepare coal samples for experiments,and clean fracturing fluid samples were prepared using CTAB surfactant.A series of hydraulic fracturing tests were conducted with an in-house developed triaxial hydraulic fracturing simulator and the fracturing process was monitored with an acoustic emission instrument to analyze the influences of fracturing fluid viscosity and horizontal in-situ stress difference on coal fracture propagation.The results show that the number of branched fractures decreased,the fracture pattern became simpler,the fractures width increased obviously,and the distribution of AE event points was concentrated with the increase of the fracturing fluid viscosity or the horizontal in-situ stress difference.The acoustic emission energy decreases with the increase of fracturing fluid viscosity and increases with the increase of horizontal in situ stress difference.The low viscosity clean fracturing fluid has strong elasticity and is easy to be compressed into the tip of fractures,resulting in complex fractures.The high viscosity clean fracturing fluids are the opposite.Our experimental results provide a reference and scientific basis for the design and optimization of field hydraulic fracturing parameters.
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    Mechanical properties and energy evolutions of burst-prone coal samples with holes and fillings

    Yukai FuYongzheng WuJunchen LiPenghe Zhou...
    176-189页
    查看更多>>摘要：During the mining process of impact-prone coal seams,drilling pressure relief can reduce the impact propensity of the coal seam,but it also reduces the integrity and strength of the coal mass at the side of the roadway.Therefore,studying the mechanical properties and energy evolution rules of coal samples containing holes and filled structures has certain practi-cal significance for achieving coordinated control of coal mine rockburst disasters and the stability of roadway surrounding rocks.To achieve this aim,seven types of burst-prone coal samples were prepared and subject to uniaxial compression experiments with the aid of a TAW-3000 electro-hydraulic servo testing machine.Besides,the stress-strain curves,acoustic emission signals,DIC strain fields and other data were collected during the experiments.Furthermore,the failure modes and energy evolutions of samples with varying drilled hole sizes and filling materials were analyzed.The results show that the indexes related to burst propensity of the drilled coal samples decline to some extent compared with those of the intact one,and the decline is positively corelated to the diameter of the drilled hole.After hole filling,the strain concentration degree around the drilled hole is lowered to a certain degree,and polyurethane filling has a more remarkable effect than cement filling.Meanwhile,hole filling can enhance the strength and deformation resistance of coal.Hole drilling can accelerate the release of accumulated elastic strain energy,turning the acoustic emission events from low-frequency and high-energy ones to high-frequency and low-energy ones,whereas hole filling can reduce the intensity of energy release.The experimental results and theoretical derivation demonstrate that hole filling promotes coal deformability and strength mainly by weaken-ing stress concentration surrounding the drilled holes.Moreover,the fillings can achieve a better filling effect if their elastic modulus and Poisson's ratio are closer to those of the coal body.
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