Methane(CH_(4))and carbon dioxide(CO_(2))are primary components of coal seam gas(CSG).Understanding their adsorption-desorption hysteresis characteristics,along with the fundamental mechanism,is crucial for CSG exploi...Methane(CH_(4))and carbon dioxide(CO_(2))are primary components of coal seam gas(CSG).Understanding their adsorption-desorption hysteresis characteristics,along with the fundamental mechanism,is crucial for CSG exploitation and related hazards mitigation.This research focused on the representative Bulli coal seam in the Sydney Basin,Australia.Through the purpose-built indirect gravimetric high-pressure isothermal adsorption-desorption hysteresis experiment,a novel Langmuir-based desorption model,incorporating hysteresis effect and residual gas,was proposed.Quantitative characterization of the adsorption-desorption hysteresis degrees of CO_(2)and CH_(4)i n coal particles of various sizes and inΦ50mm 100 mm intact coal samples were achieved using the improved hysteresis index(IHI).The experimental findings validated that the proposed desorption model accurately describes the desorption behavior of CO_(2)and CH_(4)in coal(R^(2)>0.99).Based on the adsorption-desorption properties of inkbottle-shaped micropores and pore deformation caused by gas adsorption-induced coal expansion,the occurrence mechanism of adsorption–desorption hysteresis and the fundamental reasons for the presence of residual gas were elucidated.Furthermore,the study explored the impact of CO_(2)and CH_(4)adsorption-desorption hysteresis effects on coal and gas outbursts,suggesting that coal seams rich in CO_(2)do not have a higher propensity for outbursts than those rich in CH_(4).展开更多
Gas adsorption has an important influence on gas flow in a coal body.Research on the characteristics of coal and gas adsorption is the theoretical basis for studying gas flow in coal.In this paper,the interaction betw...Gas adsorption has an important influence on gas flow in a coal body.Research on the characteristics of coal and gas adsorption is the theoretical basis for studying gas flow in coal.In this paper,the interaction between methane,carbon dioxide and surface molecules of anthracite was simulated using the quantum chemistry method.Adsorption energy and adsorption configurations of different quantities of gas molecules absorbed on the coal surface were calculated.The results show that adsorption between coal and the two kinds of gas molecules is a physical adsorption process and there is an optimal configuration.Gas molecules are more easily adsorbed in the hydroxyl-containing side chain,while it is difficult for them to be adsorbed at the position of the benzene ring.Besides,carbon dioxide molecules are more readily adsorbed on the coal surface than methane molecules.The findings have an important significance in revealing the nature of gas adsorption in coal.展开更多
In this work, the use of sepiolite for the removal of carbon dioxide from a carbon dioxide/methane mixture by a pressure swing adsorption （PSA） process has been researched. Adsorption equilibrium and kinetics have b...In this work, the use of sepiolite for the removal of carbon dioxide from a carbon dioxide/methane mixture by a pressure swing adsorption （PSA） process has been researched. Adsorption equilibrium and kinetics have been measured in a fixed-bed, and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained. A model based on the LDF approximation has been employed to simulate the fixed-bed kinetics, using the Langmuir equation to describe the adsorption equilibrium isotherm. The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied. The experimental results were compared with the ones predicted by the model adapted to a PSA system. Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle. These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.展开更多
Sorption isotherms of hydrocarbon and carbon dioxide （CO2） provide crucial information for designing processes to sequester CO2 and recover natural gas from unmineable coal beds. Methane （CH4）, ethane （C2H6）, an...Sorption isotherms of hydrocarbon and carbon dioxide （CO2） provide crucial information for designing processes to sequester CO2 and recover natural gas from unmineable coal beds. Methane （CH4）, ethane （C2H6）, and CO2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo （MC） and molecular dynamics （MD） simulations at temperatures of 308 and 370 K （35 and 97 ~C） and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption （expressed as a mass basis） divided by bulk gas density has negligible temperature effect on CH4, C2H6, and CO2 sorption on dry coal when pressure is over 6 MPa. CO2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO2 mole- cules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ＂a＂ constant （pro- portional to TcPc） in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO2 injection pressures of lower than 8 MPa may be desirable for CH4 recovery and CO2 sequestration. This study provides a quantitative under- standing of the effects of temperature on coal sorptioncapacity for CH4, C2H6, and CO2 from a microscopic perspective.展开更多
Under the context of carbon neutrality of China,it is urgent to shift our energy supply towards cleaner fuels as well as to reduce the greenhouse gas emission.Currently,coal is the main fossil fuel energy source of Ch...Under the context of carbon neutrality of China,it is urgent to shift our energy supply towards cleaner fuels as well as to reduce the greenhouse gas emission.Currently,coal is the main fossil fuel energy source of China.The country is striving hard to replace it with methane,a cleaner fossil fuel.Although China has rich geological resources of methane as coal bed methane(CBM)reserves,it is quite challenging to utilize them due to low concentration.The CBM is however mainly emitted directly to atmosphere during coal mining,causing waste of the resource and huge contribution to greenhouse effect.The recent work by Yang et al.demonstrated a potential solution to extract low concentration methane selectively from CBM through using MOF materials as sorbents.Such kind of materials and associated separation technology are promising to reduce greenhouse gas emission and promote the methane production capability,which would contribute to carbon neutrality in dual pathways.展开更多
基金provided by the China Scholarship Council(No.202006430006)and the University of Wollongongsupported by the ACARP Projects(Nos.C28006 and C35015)support from the Coal Services Health and Safety Trust(No.20661)。
文摘Methane(CH_(4))and carbon dioxide(CO_(2))are primary components of coal seam gas(CSG).Understanding their adsorption-desorption hysteresis characteristics,along with the fundamental mechanism,is crucial for CSG exploitation and related hazards mitigation.This research focused on the representative Bulli coal seam in the Sydney Basin,Australia.Through the purpose-built indirect gravimetric high-pressure isothermal adsorption-desorption hysteresis experiment,a novel Langmuir-based desorption model,incorporating hysteresis effect and residual gas,was proposed.Quantitative characterization of the adsorption-desorption hysteresis degrees of CO_(2)and CH_(4)i n coal particles of various sizes and inΦ50mm 100 mm intact coal samples were achieved using the improved hysteresis index(IHI).The experimental findings validated that the proposed desorption model accurately describes the desorption behavior of CO_(2)and CH_(4)in coal(R^(2)>0.99).Based on the adsorption-desorption properties of inkbottle-shaped micropores and pore deformation caused by gas adsorption-induced coal expansion,the occurrence mechanism of adsorption–desorption hysteresis and the fundamental reasons for the presence of residual gas were elucidated.Furthermore,the study explored the impact of CO_(2)and CH_(4)adsorption-desorption hysteresis effects on coal and gas outbursts,suggesting that coal seams rich in CO_(2)do not have a higher propensity for outbursts than those rich in CH_(4).
基金foundation by the National Key Basic Research and Development Project Program of China(No.2011CB201202-2)the Research Fund for the Doctoral Program of Higher Education(No.20120023120005)+1 种基金the Foundation of State Key Laboratory of Coal Resources and Safety Mining(No.SKLCRSM11KFB04)the Fundamental Research Funds for the Central Universities(No.2009kz03)
文摘Gas adsorption has an important influence on gas flow in a coal body.Research on the characteristics of coal and gas adsorption is the theoretical basis for studying gas flow in coal.In this paper,the interaction between methane,carbon dioxide and surface molecules of anthracite was simulated using the quantum chemistry method.Adsorption energy and adsorption configurations of different quantities of gas molecules absorbed on the coal surface were calculated.The results show that adsorption between coal and the two kinds of gas molecules is a physical adsorption process and there is an optimal configuration.Gas molecules are more easily adsorbed in the hydroxyl-containing side chain,while it is difficult for them to be adsorbed at the position of the benzene ring.Besides,carbon dioxide molecules are more readily adsorbed on the coal surface than methane molecules.The findings have an important significance in revealing the nature of gas adsorption in coal.
文摘In this work, the use of sepiolite for the removal of carbon dioxide from a carbon dioxide/methane mixture by a pressure swing adsorption （PSA） process has been researched. Adsorption equilibrium and kinetics have been measured in a fixed-bed, and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained. A model based on the LDF approximation has been employed to simulate the fixed-bed kinetics, using the Langmuir equation to describe the adsorption equilibrium isotherm. The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied. The experimental results were compared with the ones predicted by the model adapted to a PSA system. Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle. These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.
基金supported by the National Basic Research Program of China (2014CB239004)the ‘‘Element and Process Constraint Petroleum System Modeling’’ project (No. 2011A-0207) under the Petro China Science Innovation program
文摘Sorption isotherms of hydrocarbon and carbon dioxide （CO2） provide crucial information for designing processes to sequester CO2 and recover natural gas from unmineable coal beds. Methane （CH4）, ethane （C2H6）, and CO2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo （MC） and molecular dynamics （MD） simulations at temperatures of 308 and 370 K （35 and 97 ~C） and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption （expressed as a mass basis） divided by bulk gas density has negligible temperature effect on CH4, C2H6, and CO2 sorption on dry coal when pressure is over 6 MPa. CO2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO2 mole- cules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ＂a＂ constant （pro- portional to TcPc） in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO2 injection pressures of lower than 8 MPa may be desirable for CH4 recovery and CO2 sequestration. This study provides a quantitative under- standing of the effects of temperature on coal sorptioncapacity for CH4, C2H6, and CO2 from a microscopic perspective.
基金financial support from the National Natural Science Foundation of China(No.22038001,51621003,22108007)。
文摘Under the context of carbon neutrality of China,it is urgent to shift our energy supply towards cleaner fuels as well as to reduce the greenhouse gas emission.Currently,coal is the main fossil fuel energy source of China.The country is striving hard to replace it with methane,a cleaner fossil fuel.Although China has rich geological resources of methane as coal bed methane(CBM)reserves,it is quite challenging to utilize them due to low concentration.The CBM is however mainly emitted directly to atmosphere during coal mining,causing waste of the resource and huge contribution to greenhouse effect.The recent work by Yang et al.demonstrated a potential solution to extract low concentration methane selectively from CBM through using MOF materials as sorbents.Such kind of materials and associated separation technology are promising to reduce greenhouse gas emission and promote the methane production capability,which would contribute to carbon neutrality in dual pathways.
