A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an H_(2)O-D_(2)O mixture.Results have been obtained and analyzed in the concentration range of 0%-10%and 90%-10...A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an H_(2)O-D_(2)O mixture.Results have been obtained and analyzed in the concentration range of 0%-10%and 90%-100%D_(2)O.A proposed structure of tungsten scatterers in an aluminum host is studied.In order to detect the target material,a cavity region is considered as a sound wave resonator in which the target material with different concentrations of D_(2)O is embedded.By changing the concentration of D_(2)O in the H_(2)O-D_(2)O mixture,the resonance frequency undergoes a frequency shift.Each 1%change in D_(2)O concentration in the H_(2)O-D_(2)O mixture causes a frequency change of about 120 Hz.The finite element method is used as the numerical method to calculate and analyze the natural frequencies and transmission spectra of the proposed sensor.The performance evaluation index shows a high Q factor up to 1475758 and a high sensitivity up to 13075,which are acceptable values for sensing purposes.The other figures of merit related to the detection performance also indicate high-quality performance of the designed sensor.展开更多
It is acknowledged that injecting CO_(2) into oil reservoirs and saline aquifers for storage is a practical and affordable method for CO_(2) sequestration.Most CO_(2) produced from industrial exhaust contains impurity...It is acknowledged that injecting CO_(2) into oil reservoirs and saline aquifers for storage is a practical and affordable method for CO_(2) sequestration.Most CO_(2) produced from industrial exhaust contains impurity gases such as H_(2)S that might impact CO_(2) sequestration due to competitive adsorption.This study makes a commendable effort to explore the adsorption behavior of CO_(2)/H_(2)S mixtures in calcite slit nanopores.Grand Canonical Monte Carlo(GCMC)simulation is employed to reveal the adsorption of CO_(2),H_(2)S as well as their binary mixtures in calcite nanopores.Results show that the increase in pressure and temperature can promote and inhibit the adsorption capacity of CO_(2) and H_(2)S in calcite nanopores,respectively.CO_(2)exhibits stronger adsorption on calcite surface than H_(2)S.Electrostatic energy plays the dominating role in the adsorption behavior.Electrostatic energy accounts for 97.11%of the CO_(2)-calcite interaction energy and 56.33%of the H_(2)S-calcite interaction energy at 10 MPa and 323.15 K.The presence of H_(2)S inhibits the CO_(2) adsorption in calcite nanopores due to competitive adsorption,and a higher mole fraction of H_(2)S leads to less CO_(2) adsorption.The quantity of CO_(2) adsorbed is lessened by approximately 33%when the mole fraction of H_(2)S reaches 0.25.CO_(2) molecules preferentially occupy the regions near the po re wall and H_(2)S molecules tend to reside at the center of nanopore even when the molar ratio of CO_(2) is low,indicating that CO_(2) has an adsorption priority on the calcite surface over H_(2)S.In addition,moisture can weaken the adsorption of both CO_(2) and H_(2)S,while CO_(2) is more affected.More interestingly,we find that pure CO_(2) is more suitable to be sequestrated in the shallower formations,i.e.,500-1500 m,whereas CO_(2)with H_(2)S impurity should be settled in the deeper reservoirs.展开更多
The agglomeration behavior of particles significantly impacts on the defluidization occurring in a fluidized bed during the direct reduction process.The influence of CO/H_(2)ratio on surface diffusion of iron atoms wa...The agglomeration behavior of particles significantly impacts on the defluidization occurring in a fluidized bed during the direct reduction process.The influence of CO/H_(2)ratio on surface diffusion of iron atoms was proposed,and the solid bridge force between iron oxide particles was quantificationally analyzed.Moreover,the solid bridge force was successfully added into a CFD–DEM(computational fluid dynamics–discrete element method)model combined with heat transfer and mass transport to investigate the detailed information of agglomeration in a fluidized bed,including the spatial distribution of temperature,velocity and metallization of iron oxide particles.The region of defluidization is sensitive to the reduction temperature.At the same reduction temperature,the iron oxide powder will perform higher metallization and stable fluidization properties with molar fraction of H_(2)in the range of 0.6–0.8,when iron oxide is reduced by CO/H_(2)mixture.展开更多
As the greenhouse effect concerns increases,the development of new materials for the efficient capture and separation of CO_(2)gas from gas mixtures has become a matter of urgency.In this study,we performed density fu...As the greenhouse effect concerns increases,the development of new materials for the efficient capture and separation of CO_(2)gas from gas mixtures has become a matter of urgency.In this study,we performed density functional theory(DFT)calculations to investigate the adsorption and separation behavior of CO_(2)/CH_(4)/H_(2)on the surface of two-dimensional(2D)Al_(2)C materials under positive/negative applied electric fields.In the absence of an electric field CO_(2)is weakly physisorbed on the Al_(2)C surface,but with the application of an applied electric field,the adsorption state of CO_(2)gradually changes from physical to chemisorption(adsorption energy changes from-0.29 e V to-3.61 e V),while the negative electric field has little effect on the adsorption of CO_(2).We conclude that the C=O bond in adsorbed CO_(2)can be activated under an external electric field(maximum activation of 15%under an external electric field of 0-0.005 a.u.).Only in the presence of an applied electric field of 0.0033 a.u.and temperatures above525 K/675 K can the adsorption/separation reaction of CO_(2)single adsorption and CO_(2)/CH_(4)/H_(2)mixture be spontaneous.The adsorption/desorption of CO_(2)on Al_(2)C nanosheet in an electric field of 0.003-0.0033 a.u.is all exothermic,which can be easily controlled by switching on/off the electric field without any energy barriers.The capacity of Al_(2)C to capture CO_(2)per unit electric field decreases with increasing CO_(2)concentration,but still has efficient gas separation properties for CO_(2)/CH_(4)/H_(2).Our theoretical results could provide guidance for designing high-capacity and high-selectivity CO_(2)capture materials.展开更多
Supercritical H_(2)O/CO_(2) mixtures(650 K–973 K and 25 MPa,not far away from the critical temperature and pressure of water)have recently been used as the working fluid for a novel power generation system with highe...Supercritical H_(2)O/CO_(2) mixtures(650 K–973 K and 25 MPa,not far away from the critical temperature and pressure of water)have recently been used as the working fluid for a novel power generation system with higher efficiency and zero pollutant emission compared to conventional coal-fired power plants.The knowledge of the diffusion of these mixtures is important for efficient design of the system process.However,both experimental and theoretical data are scarce for typical working conditions in the system.Here,we investigated both the self-diffusion and the mutual diffusion of the supercritical H_(2)O/CO_(2) mixtures using molecular dynamics(MD)simulations.Simulations show that the mixture diffusion coefficients for supercritical conditions are more than one order of magnitude larger than those in the sub-critical region.MD results reveal that H_(2)O molecules prefer to gather with themselves rather than with CO_(2) molecules in the near-critical region,while there is no featured molecular structure for higher temperatures in the supercritical region.Therefore,the self-diffusion of CO_(2) in H_(2)O in the infinite-dilution regime features Arrhenius temperature dependent behavior in the supercritical region excluding the near-critical-temperature segment.These molecular interaction mechanisms also provide insights into the mutual diffusion behavior of CO_(2) in H_(2)O,which is well described by the Darken equation in the supercritical region.Furthermore,engineering equations,namely the Speedy-Angell power-law equation and the Vignes equation,can reproduce MD simulated infinite-dilution self-diffusion coefficients and Maxwell-Stefan mutual diffusion coefficients,respectively,of the supercritical H_(2)O/CO_(2) mixtures.展开更多
文摘A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an H_(2)O-D_(2)O mixture.Results have been obtained and analyzed in the concentration range of 0%-10%and 90%-100%D_(2)O.A proposed structure of tungsten scatterers in an aluminum host is studied.In order to detect the target material,a cavity region is considered as a sound wave resonator in which the target material with different concentrations of D_(2)O is embedded.By changing the concentration of D_(2)O in the H_(2)O-D_(2)O mixture,the resonance frequency undergoes a frequency shift.Each 1%change in D_(2)O concentration in the H_(2)O-D_(2)O mixture causes a frequency change of about 120 Hz.The finite element method is used as the numerical method to calculate and analyze the natural frequencies and transmission spectra of the proposed sensor.The performance evaluation index shows a high Q factor up to 1475758 and a high sensitivity up to 13075,which are acceptable values for sensing purposes.The other figures of merit related to the detection performance also indicate high-quality performance of the designed sensor.
基金financial support from the National Natural Science Foundation of China (Grant No.52004320)the Science Foundation of China University of Petroleum,Beijing (No.2462021QNXZ012,No.2462022BJRC001,and No.2462021YJRC012)the funding from the State Key Laboratory of Petroleum Resources and Engineering (No.PRP/indep-1-2103)。
文摘It is acknowledged that injecting CO_(2) into oil reservoirs and saline aquifers for storage is a practical and affordable method for CO_(2) sequestration.Most CO_(2) produced from industrial exhaust contains impurity gases such as H_(2)S that might impact CO_(2) sequestration due to competitive adsorption.This study makes a commendable effort to explore the adsorption behavior of CO_(2)/H_(2)S mixtures in calcite slit nanopores.Grand Canonical Monte Carlo(GCMC)simulation is employed to reveal the adsorption of CO_(2),H_(2)S as well as their binary mixtures in calcite nanopores.Results show that the increase in pressure and temperature can promote and inhibit the adsorption capacity of CO_(2) and H_(2)S in calcite nanopores,respectively.CO_(2)exhibits stronger adsorption on calcite surface than H_(2)S.Electrostatic energy plays the dominating role in the adsorption behavior.Electrostatic energy accounts for 97.11%of the CO_(2)-calcite interaction energy and 56.33%of the H_(2)S-calcite interaction energy at 10 MPa and 323.15 K.The presence of H_(2)S inhibits the CO_(2) adsorption in calcite nanopores due to competitive adsorption,and a higher mole fraction of H_(2)S leads to less CO_(2) adsorption.The quantity of CO_(2) adsorbed is lessened by approximately 33%when the mole fraction of H_(2)S reaches 0.25.CO_(2) molecules preferentially occupy the regions near the po re wall and H_(2)S molecules tend to reside at the center of nanopore even when the molar ratio of CO_(2) is low,indicating that CO_(2) has an adsorption priority on the calcite surface over H_(2)S.In addition,moisture can weaken the adsorption of both CO_(2) and H_(2)S,while CO_(2) is more affected.More interestingly,we find that pure CO_(2) is more suitable to be sequestrated in the shallower formations,i.e.,500-1500 m,whereas CO_(2)with H_(2)S impurity should be settled in the deeper reservoirs.
基金the National Natural Science Foundation Project of China(51374263 and 51974046).
文摘The agglomeration behavior of particles significantly impacts on the defluidization occurring in a fluidized bed during the direct reduction process.The influence of CO/H_(2)ratio on surface diffusion of iron atoms was proposed,and the solid bridge force between iron oxide particles was quantificationally analyzed.Moreover,the solid bridge force was successfully added into a CFD–DEM(computational fluid dynamics–discrete element method)model combined with heat transfer and mass transport to investigate the detailed information of agglomeration in a fluidized bed,including the spatial distribution of temperature,velocity and metallization of iron oxide particles.The region of defluidization is sensitive to the reduction temperature.At the same reduction temperature,the iron oxide powder will perform higher metallization and stable fluidization properties with molar fraction of H_(2)in the range of 0.6–0.8,when iron oxide is reduced by CO/H_(2)mixture.
基金funded by the National Natural Science Foundation of China(No.21603109)the Henan Joint Fund of the National Natural Science Foundation of China(No.U1404216)the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0676)。
文摘As the greenhouse effect concerns increases,the development of new materials for the efficient capture and separation of CO_(2)gas from gas mixtures has become a matter of urgency.In this study,we performed density functional theory(DFT)calculations to investigate the adsorption and separation behavior of CO_(2)/CH_(4)/H_(2)on the surface of two-dimensional(2D)Al_(2)C materials under positive/negative applied electric fields.In the absence of an electric field CO_(2)is weakly physisorbed on the Al_(2)C surface,but with the application of an applied electric field,the adsorption state of CO_(2)gradually changes from physical to chemisorption(adsorption energy changes from-0.29 e V to-3.61 e V),while the negative electric field has little effect on the adsorption of CO_(2).We conclude that the C=O bond in adsorbed CO_(2)can be activated under an external electric field(maximum activation of 15%under an external electric field of 0-0.005 a.u.).Only in the presence of an applied electric field of 0.0033 a.u.and temperatures above525 K/675 K can the adsorption/separation reaction of CO_(2)single adsorption and CO_(2)/CH_(4)/H_(2)mixture be spontaneous.The adsorption/desorption of CO_(2)on Al_(2)C nanosheet in an electric field of 0.003-0.0033 a.u.is all exothermic,which can be easily controlled by switching on/off the electric field without any energy barriers.The capacity of Al_(2)C to capture CO_(2)per unit electric field decreases with increasing CO_(2)concentration,but still has efficient gas separation properties for CO_(2)/CH_(4)/H_(2).Our theoretical results could provide guidance for designing high-capacity and high-selectivity CO_(2)capture materials.
基金supported by the National Key R&D Program of China(No.2016YFB0600100)the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103)the Fundamental Research Funds of the Central Universities(No.30919011403)。
文摘Supercritical H_(2)O/CO_(2) mixtures(650 K–973 K and 25 MPa,not far away from the critical temperature and pressure of water)have recently been used as the working fluid for a novel power generation system with higher efficiency and zero pollutant emission compared to conventional coal-fired power plants.The knowledge of the diffusion of these mixtures is important for efficient design of the system process.However,both experimental and theoretical data are scarce for typical working conditions in the system.Here,we investigated both the self-diffusion and the mutual diffusion of the supercritical H_(2)O/CO_(2) mixtures using molecular dynamics(MD)simulations.Simulations show that the mixture diffusion coefficients for supercritical conditions are more than one order of magnitude larger than those in the sub-critical region.MD results reveal that H_(2)O molecules prefer to gather with themselves rather than with CO_(2) molecules in the near-critical region,while there is no featured molecular structure for higher temperatures in the supercritical region.Therefore,the self-diffusion of CO_(2) in H_(2)O in the infinite-dilution regime features Arrhenius temperature dependent behavior in the supercritical region excluding the near-critical-temperature segment.These molecular interaction mechanisms also provide insights into the mutual diffusion behavior of CO_(2) in H_(2)O,which is well described by the Darken equation in the supercritical region.Furthermore,engineering equations,namely the Speedy-Angell power-law equation and the Vignes equation,can reproduce MD simulated infinite-dilution self-diffusion coefficients and Maxwell-Stefan mutual diffusion coefficients,respectively,of the supercritical H_(2)O/CO_(2) mixtures.
