Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In...Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.展开更多
Turbulent fluidized bed possesses a distinct advantage over bubbling fluidized bed in high solids contact efficiency and thus exerts great potential in applications to many industrial processes.Simulation for fluidiza...Turbulent fluidized bed possesses a distinct advantage over bubbling fluidized bed in high solids contact efficiency and thus exerts great potential in applications to many industrial processes.Simulation for fluidization of fluid catalytic cracking(FCC)particles and the catalytic reaction of ozone decomposition in turbulent fluidized bed is conducted using the EulerianeEulerian approach,where the recently developed two-equation turbulent(TET)model is introduced to describe the turbulent mass diffusion.The energy minimization multi-scale(EMMS)drag model and the kinetic theory of granular flow(KTGF)are adopted to describe gaseparticles interaction and particleeparticle interaction respectively.The TET model features the rigorous closure for the turbulent mass transfer equations and thus enables more reliable simulation.With this model,distributions of ozone concentration and gaseparticles two-phase velocity as well as volume fraction are obtained and compared against experimental data.The average absolute relative deviation for the simulated ozone concentration is 9.67%which confirms the validity of the proposed model.Moreover,it is found that the transition velocity from bubbling fluidization to turbulent fluidization for FCC particles is about 0.5 m$se1 which is consistent with experimental observation.展开更多
In this paper,a model of activated carbon was established by molecular simulation and the separation performance of N2 and CH4 on activated carbon was studied.In order to evaluate the adsorption selectivity and diffus...In this paper,a model of activated carbon was established by molecular simulation and the separation performance of N2 and CH4 on activated carbon was studied.In order to evaluate the adsorption selectivity and diffusion selectivity of N2 and CH4,Grand Canonical Monte Carlo and molecular dynamic methods were used to obtain equilibrium adsorption isotherms and mean square displacements of N2 and CH4 on activated carbon with different pore sizes.Research results showed that the difference in adsorption isosteric heat of N2 and CH4 at the pore size of 0.46 nm is the largest,which is 5.759 and 7.03 kcal·mol^-1(1 cal=4.184 J),respectively.Activated carbon with pore size of 0.46 nm has the best N2 and CH4 adsorption selectivity,while its diffusion selectivity is not obvious.展开更多
In order to better guide the design of industrial process for purification and recovery of VOCs,temperature swing adsorption(TSA)and temperature vacuum swing adsorption(TVSA)process for VOCs purification and recovery ...In order to better guide the design of industrial process for purification and recovery of VOCs,temperature swing adsorption(TSA)and temperature vacuum swing adsorption(TVSA)process for VOCs purification and recovery were studied systematically with activated carbon adsorbent.The adsorption and desorption behaviors of benzene on activated carbon in above two processes were investigated systematically.Effects of operating parameters on process performances were further analyzed,including as regeneration temperature,purging feed ratio and hot–cold purging ratio.The results showed that the increase of hot–cold purging ratio(HP/CP)could obtain the same regeneration effect as the increase of desorption temperature.Increasing the feed purge ratio without increasing the hot–cold purging ratio is not conducive to bed regeneration,because a large number of cold purge gases cannot utilize the residual heat of temperature wave,thus reducing the desorption effect of the cooling step on the bed.In addition,the vacuum step can enhance the regeneration ability of hot nitrogen to the bed at the same regeneration temperature,making the bed regeneration of TVSA process more thorough.Temperature in the middle and lower part of the bed in TVSA process was higher and the regeneration was more thorough.In conclusion,TVSA has more obvious advantages than TSA in terms of energy consumption,hot or cold purge volume and bed regeneration.展开更多
A two-stage vacuum pressure swing adsorption(VPSA)process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue ...A two-stage vacuum pressure swing adsorption(VPSA)process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue gas(85%N_(2)/15%CO_(2)).In the first enriching stage,carbon molecular sieve(CMS),which shows kinetic selectivity for CO_(2)/N_(2),is adopted as the adsorbent to remove most N_(2)in feed gas,thereby upgrading CO_(2)and significantly reducing the amount for further refinement.The second stage loads zeolite 13X as adsorbent to purify the CO_(2)-rich flow from the first stage for meeting the requirements of National Energy Technology Laboratory.Series of experiments have been conducted for adsorption isotherms measuring and lab-scale experimental validation as well as analysis.The effect of feed composition on the separation performance of the PSA system was studied experimentally and theoretically here.The optimal results achieved 95.1%purity and 92.9%recovery with a high CO_(2)productivity(1.89 mol CO_(2)·h^(-1)·kg^(-1))and an appropriate energy consumption of 1.07 MJ·(kg CO_(2))^(-1).Further analysis has been carried out by simulation for explicating the temperature,pressure,and concentration distribution at cyclic steady state.展开更多
Particle-fluid system is one of the most popular systems in chemical processes.Owing to complex interface structure and high-velocity turbulence,the momentum and mass transfer exhibit nonlinear characteristics,which p...Particle-fluid system is one of the most popular systems in chemical processes.Owing to complex interface structure and high-velocity turbulence,the momentum and mass transfer exhibit nonlinear characteristics,which pose a great challenge for further study and application.To solve this problem,computational mass transfer(CMT)emerged and has been proved to be effective in deeply exploring the mass transfer behavior of particle-fluid systems.First,this paper reviews recent gas-solid numerical studies of turbulence issues from empirical to theoretical,then discusses interphase mass transfer rate models and the interfacial interaction force.Second,the present study particularly reviews researches on mass transfer process of fixed and fluidized regime by CMT,providing reliable analysis of turbulent anisotropy diffusivity as well as multiscale structure and presenting theoretical instruction for the industrial optimization of mass transfer processes in chemical engineering.展开更多
Solid-state polymer electrolytes(SPEs) capable of withstanding high voltage are considered to be key for next-generation energy storage devices with inherent safety as well as high energy density.This study involves t...Solid-state polymer electrolytes(SPEs) capable of withstanding high voltage are considered to be key for next-generation energy storage devices with inherent safety as well as high energy density.This study involves the rational design of solid-state-C≡N functionalized P(VEC_1-CEA_(0.3))/LiTFSI@CE SPEs and its synthesis by in-situ free radical polymerization of vinyl ethylene carbonate(VEC) and 2-cyanoethyl acrylate(CEA).In situ polymerization yields electrode/electrolyte interfaces with low interfacial resistance,forming a stable SEI layer enriched with LiF,Li_(3)N,and RCOOLi,ensuring stable Li plating/stripping for over 1400 h.The-C≡N moiety renders the αH on the adjacent αC positively charged,thereby endowing it with the capability to anchor TFSI^(-).Simultaneously,the incorporation of-C≡N moiety diminishes the electron-donating ability of the C=O,C-O-C,and-C≡N functional groups,facilitating not only the ion conductivity enhancement but also a more rapid Li^(+)migration proved by DFT theoretical calculations and Raman spectroscopy.At room temperature,t_(Li+) of 0.60 for P(VEC_1-CEA_(0.3))/LiTFSI@CE SPEs is achieved when the ionic conductivity σ_(Li+)is 2.63×10^(-4) S cm^(-1) and the electrochemical window is expanded to5.0 V.Both coin cells with high-areal-loading cathodes and the 6.5-mAh pouch cell,exhibit stable charge/discharge cycling.At 25℃,the 4.45-V Li|P(VEC_1-CEA_(0.3))/LiTFSI@CE|LiCoO_(2) battery performs stable cycling over 200 cycles at 0.2 C,with a capacity retention of 82.1%.展开更多
The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection...The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection positions by simulating five simplified and representative erosion categories,including A-type horizontal-vertical elbow with an upstream flow,B-type horizontal-vertical elbow with a downstream flow,C-type vertical-horizontal elbow with an upstream flow,D-type vertical-horizontal elbow with a downstream flow and E-type horizontal-horizontal elbow.Compared with the C/D-type elbow,where particles were injected uniformly,the A-type elbow and E-type elbow were found to increase erosion rate,while the B-type elbow decreases erosion rate.An interesting discovery is that the elbow erosion rate is relatively low for small particles when particles are injected from the middle and bottom positions of the inlet section of the elbow.Based on the observation,a novel preceding rotating sheet structure was developed to regulate the particle injection position.It shows an excellent anti-erosion performance by reducing the maximum erosion rate of particles with diameters of 50,100,and 200μm by 23%,35%,and 43%,respectively.展开更多
The enrichment of low concentration coalbed methane using adsorption process with activated carbon adsorbent was studied in this work.Adsorption isotherms of methane,nitrogen and carbon dioxide on activated carbon wer...The enrichment of low concentration coalbed methane using adsorption process with activated carbon adsorbent was studied in this work.Adsorption isotherms of methane,nitrogen and carbon dioxide on activated carbon were measured by volumetric method,meanwhile a series of breakthrough tests with single component,binary components and three components feed mixture has been performed for exploring dynamic adsorption behaviors.Moreover,a rigorous mathematical model of adsorption bed containing mass,energy,and momentum conservation equation as well as dualsite Langmuir model with the Linear driving force model for gassolid phase mass transfer has been proposed for numerical modeling and simulation of fixed bed breakthrough process and vacuum pressure swing adsorption process.Furthermore,the lumped mass transfer coefficient of methane,nitrogen and carbon dioxide on activated carbon adsorbent has been determined to be 0.3 s^(-1),1.0 s^(-1) and 0.06 s^(-1) by fitting the breakthrough curves using numerical calculation.Additionally,a six bed VPSA process with twelve step cycle sequence has been proposed and investigated for low concentration coalbed methane enrichment.Results demonstrated that the methane molar fraction in feed mixture ranged from 10%to 50%could be enriched to 32.15%to 88.75%methane in heavy product gas with a methane recovery higher than 83%under the adsorption pressure of 3 bar(1 bar=105 Pa)and desorption pressure of 0.1 bar.Energy consumption of this VPSA process was varied from 0.165 k·W·h·m^(-3) CH_(4)to 0.649 k·W·h·m^(-3) CH_(4).Finally,a dualstage VPSA process has been successfully developed to upgrade a low concentration coalbed methane containing 20%methane to a target product gas with methane purity higher than 90%,meanwhile the total methane recovery was up to 98.71%with a total energy consumption of 0.504 k·W·h·m^(-3)CH_(4).展开更多
An integrated vacuum pressure swing adsorption(VPSA) and Rectisol process is proposed for CO_(2) capture from underground coal gasification(UCG) syngas. A ten-bed VPSA process with silica gel adsorbent is firstly desi...An integrated vacuum pressure swing adsorption(VPSA) and Rectisol process is proposed for CO_(2) capture from underground coal gasification(UCG) syngas. A ten-bed VPSA process with silica gel adsorbent is firstly designed to pre-separate and capture 74.57% CO_(2) with a CO_(2) purity of 98.35% from UCG syngas(CH_(4)/CO/CO_(2)/H_(2)/N_(2)= 30.77%/6.15%/44.10%/18.46%/0.52%, mole fraction, from Shaar Lake Mine Field,Xinjiang Province, China) with a feed pressure of 3.5 MPa. Subsequently, the Rectisol process is constructed to furtherly remove and capture the residual CO_(2)remained in light product gas from the VPSA process using cryogenic methanol(233.15 K, 100%(mass)) as absorbent. A final purified gas with CO_(2) concentration lower than 3% and a regenerated CO_(2) product with CO_(2) purity higher than 95% were achieved by using the Rectisol process. Comparisons indicate that the energy consumption is deceased from 2.143 MJ·kg^(-1) of the single Rectisol process to 1.008 MJ·kg^(-1) of the integrated VPSA & Rectisol process, which demonstrated that the deployed VPSA was an energy conservation process for CO_(2) capture from UCG syngas. Additionally, the high-value gas(e.g., CH_(4)) loss can be decreased and the effects of key operating parameters on the process performances were detailed.展开更多
The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production,which necessitate accurate prediction of gas-solid transfer behavior.In this work,a developed Computational Flui...The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production,which necessitate accurate prediction of gas-solid transfer behavior.In this work,a developed Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)model combined with the adsorption model is proposed.The developed CFD-DEM model is validated by comparing simulated results with experimental data and empirical correlation.Subsequently,the effect of particle packing structure and particle shapes on the dynamic adsorption process are analyzed in detail.The results reveal the mechanism of particle packing structure affecting axial velocity distribution,showing that uneven distribution of resistance on the outer flow channel side leads to uneven axial velocity distribution in the bed.Compared to cylindrical adsorbents,the use of spherical adsorbents results in a more uniform axial velocity distribution,consequently reducing bed pressure drop.The study holds significant potential for optimizing gas distribution and improving separation efficiency in future industrial applications.展开更多
L-valve is often used as a non-mechanical valve for the circulation of solids in gas-solids fluidized bed(GSFB)due to its advantages in simple construction and easy control.The information on solids circu-lation rate ...L-valve is often used as a non-mechanical valve for the circulation of solids in gas-solids fluidized bed(GSFB)due to its advantages in simple construction and easy control.The information on solids circu-lation rate as well as the hydrodynamics performance of the CFB with L-valve is of great importance for its better control and design.This paper proposes a Eulerian-Eulerian approach based numerical model integrating the computational fluid dynamics(CFD)with turbulent model,the kinetic theory of granular flow(KTGF)and the drag model,thus the solids circulation rate and the local phase velocity as well as solids volume fraction can be predicted simultaneously.With this model,the hydrodynamics perfor-mance of the full loop GSCFB with a L-valve is analyzed in detail.It is found that the drag model affects the simulation significantly and the(energy minimization multiscale)EMMS method shows good per-formance in the full-loop simulation of GSCFB.展开更多
基金supported by the renewable energy and hydrogen projects in National Key Research and Development Plan of China(2019YFB1505000).
文摘Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.
基金financial support from the National Natural Science Foundation of China(22078230)the National Key Research and Development Program of China(2023YFB4103600)the State Key Laboratory of Heavy Oil Processing(SKLHOP202202008).
文摘Turbulent fluidized bed possesses a distinct advantage over bubbling fluidized bed in high solids contact efficiency and thus exerts great potential in applications to many industrial processes.Simulation for fluidization of fluid catalytic cracking(FCC)particles and the catalytic reaction of ozone decomposition in turbulent fluidized bed is conducted using the EulerianeEulerian approach,where the recently developed two-equation turbulent(TET)model is introduced to describe the turbulent mass diffusion.The energy minimization multi-scale(EMMS)drag model and the kinetic theory of granular flow(KTGF)are adopted to describe gaseparticles interaction and particleeparticle interaction respectively.The TET model features the rigorous closure for the turbulent mass transfer equations and thus enables more reliable simulation.With this model,distributions of ozone concentration and gaseparticles two-phase velocity as well as volume fraction are obtained and compared against experimental data.The average absolute relative deviation for the simulated ozone concentration is 9.67%which confirms the validity of the proposed model.Moreover,it is found that the transition velocity from bubbling fluidization to turbulent fluidization for FCC particles is about 0.5 m$se1 which is consistent with experimental observation.
基金part of the project supported by the Shanxi Coal-bed Methane Joint Research Fund(No.2015012004)。
文摘In this paper,a model of activated carbon was established by molecular simulation and the separation performance of N2 and CH4 on activated carbon was studied.In order to evaluate the adsorption selectivity and diffusion selectivity of N2 and CH4,Grand Canonical Monte Carlo and molecular dynamic methods were used to obtain equilibrium adsorption isotherms and mean square displacements of N2 and CH4 on activated carbon with different pore sizes.Research results showed that the difference in adsorption isosteric heat of N2 and CH4 at the pore size of 0.46 nm is the largest,which is 5.759 and 7.03 kcal·mol^-1(1 cal=4.184 J),respectively.Activated carbon with pore size of 0.46 nm has the best N2 and CH4 adsorption selectivity,while its diffusion selectivity is not obvious.
基金Projects in National Key Research and Development Plan of China(2019YFB1505002).
文摘In order to better guide the design of industrial process for purification and recovery of VOCs,temperature swing adsorption(TSA)and temperature vacuum swing adsorption(TVSA)process for VOCs purification and recovery were studied systematically with activated carbon adsorbent.The adsorption and desorption behaviors of benzene on activated carbon in above two processes were investigated systematically.Effects of operating parameters on process performances were further analyzed,including as regeneration temperature,purging feed ratio and hot–cold purging ratio.The results showed that the increase of hot–cold purging ratio(HP/CP)could obtain the same regeneration effect as the increase of desorption temperature.Increasing the feed purge ratio without increasing the hot–cold purging ratio is not conducive to bed regeneration,because a large number of cold purge gases cannot utilize the residual heat of temperature wave,thus reducing the desorption effect of the cooling step on the bed.In addition,the vacuum step can enhance the regeneration ability of hot nitrogen to the bed at the same regeneration temperature,making the bed regeneration of TVSA process more thorough.Temperature in the middle and lower part of the bed in TVSA process was higher and the regeneration was more thorough.In conclusion,TVSA has more obvious advantages than TSA in terms of energy consumption,hot or cold purge volume and bed regeneration.
基金financially supported by the Renewable Energy and Hydrogen Projects National Key Research&Development Program of China(2019YFB1505000)。
文摘A two-stage vacuum pressure swing adsorption(VPSA)process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue gas(85%N_(2)/15%CO_(2)).In the first enriching stage,carbon molecular sieve(CMS),which shows kinetic selectivity for CO_(2)/N_(2),is adopted as the adsorbent to remove most N_(2)in feed gas,thereby upgrading CO_(2)and significantly reducing the amount for further refinement.The second stage loads zeolite 13X as adsorbent to purify the CO_(2)-rich flow from the first stage for meeting the requirements of National Energy Technology Laboratory.Series of experiments have been conducted for adsorption isotherms measuring and lab-scale experimental validation as well as analysis.The effect of feed composition on the separation performance of the PSA system was studied experimentally and theoretically here.The optimal results achieved 95.1%purity and 92.9%recovery with a high CO_(2)productivity(1.89 mol CO_(2)·h^(-1)·kg^(-1))and an appropriate energy consumption of 1.07 MJ·(kg CO_(2))^(-1).Further analysis has been carried out by simulation for explicating the temperature,pressure,and concentration distribution at cyclic steady state.
基金the NSFC Project(grant No.22078230)the State Key Laboratory of Heavy Oil Processing(grant No.SKLHOP202202008)the National Key Researchh and Development Program ofC hina(granNt o.2018YFE0111100).
文摘Particle-fluid system is one of the most popular systems in chemical processes.Owing to complex interface structure and high-velocity turbulence,the momentum and mass transfer exhibit nonlinear characteristics,which pose a great challenge for further study and application.To solve this problem,computational mass transfer(CMT)emerged and has been proved to be effective in deeply exploring the mass transfer behavior of particle-fluid systems.First,this paper reviews recent gas-solid numerical studies of turbulence issues from empirical to theoretical,then discusses interphase mass transfer rate models and the interfacial interaction force.Second,the present study particularly reviews researches on mass transfer process of fixed and fluidized regime by CMT,providing reliable analysis of turbulent anisotropy diffusivity as well as multiscale structure and presenting theoretical instruction for the industrial optimization of mass transfer processes in chemical engineering.
基金National Natural Science Foundation of China (22078228)。
文摘Solid-state polymer electrolytes(SPEs) capable of withstanding high voltage are considered to be key for next-generation energy storage devices with inherent safety as well as high energy density.This study involves the rational design of solid-state-C≡N functionalized P(VEC_1-CEA_(0.3))/LiTFSI@CE SPEs and its synthesis by in-situ free radical polymerization of vinyl ethylene carbonate(VEC) and 2-cyanoethyl acrylate(CEA).In situ polymerization yields electrode/electrolyte interfaces with low interfacial resistance,forming a stable SEI layer enriched with LiF,Li_(3)N,and RCOOLi,ensuring stable Li plating/stripping for over 1400 h.The-C≡N moiety renders the αH on the adjacent αC positively charged,thereby endowing it with the capability to anchor TFSI^(-).Simultaneously,the incorporation of-C≡N moiety diminishes the electron-donating ability of the C=O,C-O-C,and-C≡N functional groups,facilitating not only the ion conductivity enhancement but also a more rapid Li^(+)migration proved by DFT theoretical calculations and Raman spectroscopy.At room temperature,t_(Li+) of 0.60 for P(VEC_1-CEA_(0.3))/LiTFSI@CE SPEs is achieved when the ionic conductivity σ_(Li+)is 2.63×10^(-4) S cm^(-1) and the electrochemical window is expanded to5.0 V.Both coin cells with high-areal-loading cathodes and the 6.5-mAh pouch cell,exhibit stable charge/discharge cycling.At 25℃,the 4.45-V Li|P(VEC_1-CEA_(0.3))/LiTFSI@CE|LiCoO_(2) battery performs stable cycling over 200 cycles at 0.2 C,with a capacity retention of 82.1%.
基金the National Natural Science Foundation of China(grant No.22278332)Shaanxi Province's Key Research and Development Plan(grant No.2023-YBGY-317,2023-YBGY-175)+1 种基金Natural Science Basic Research Program of Shaanxi(grant No.2020JQ-597)Natural Science Foundation of Shaanxi Provincial Department of Education(grant No.23JK0723).
文摘The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection positions by simulating five simplified and representative erosion categories,including A-type horizontal-vertical elbow with an upstream flow,B-type horizontal-vertical elbow with a downstream flow,C-type vertical-horizontal elbow with an upstream flow,D-type vertical-horizontal elbow with a downstream flow and E-type horizontal-horizontal elbow.Compared with the C/D-type elbow,where particles were injected uniformly,the A-type elbow and E-type elbow were found to increase erosion rate,while the B-type elbow decreases erosion rate.An interesting discovery is that the elbow erosion rate is relatively low for small particles when particles are injected from the middle and bottom positions of the inlet section of the elbow.Based on the observation,a novel preceding rotating sheet structure was developed to regulate the particle injection position.It shows an excellent anti-erosion performance by reducing the maximum erosion rate of particles with diameters of 50,100,and 200μm by 23%,35%,and 43%,respectively.
文摘The enrichment of low concentration coalbed methane using adsorption process with activated carbon adsorbent was studied in this work.Adsorption isotherms of methane,nitrogen and carbon dioxide on activated carbon were measured by volumetric method,meanwhile a series of breakthrough tests with single component,binary components and three components feed mixture has been performed for exploring dynamic adsorption behaviors.Moreover,a rigorous mathematical model of adsorption bed containing mass,energy,and momentum conservation equation as well as dualsite Langmuir model with the Linear driving force model for gassolid phase mass transfer has been proposed for numerical modeling and simulation of fixed bed breakthrough process and vacuum pressure swing adsorption process.Furthermore,the lumped mass transfer coefficient of methane,nitrogen and carbon dioxide on activated carbon adsorbent has been determined to be 0.3 s^(-1),1.0 s^(-1) and 0.06 s^(-1) by fitting the breakthrough curves using numerical calculation.Additionally,a six bed VPSA process with twelve step cycle sequence has been proposed and investigated for low concentration coalbed methane enrichment.Results demonstrated that the methane molar fraction in feed mixture ranged from 10%to 50%could be enriched to 32.15%to 88.75%methane in heavy product gas with a methane recovery higher than 83%under the adsorption pressure of 3 bar(1 bar=105 Pa)and desorption pressure of 0.1 bar.Energy consumption of this VPSA process was varied from 0.165 k·W·h·m^(-3) CH_(4)to 0.649 k·W·h·m^(-3) CH_(4).Finally,a dualstage VPSA process has been successfully developed to upgrade a low concentration coalbed methane containing 20%methane to a target product gas with methane purity higher than 90%,meanwhile the total methane recovery was up to 98.71%with a total energy consumption of 0.504 k·W·h·m^(-3)CH_(4).
基金financially supported by the Renewable Energy and Hydrogen Projects in National Key Research & Development Program of China (2019YFB1505000)。
文摘An integrated vacuum pressure swing adsorption(VPSA) and Rectisol process is proposed for CO_(2) capture from underground coal gasification(UCG) syngas. A ten-bed VPSA process with silica gel adsorbent is firstly designed to pre-separate and capture 74.57% CO_(2) with a CO_(2) purity of 98.35% from UCG syngas(CH_(4)/CO/CO_(2)/H_(2)/N_(2)= 30.77%/6.15%/44.10%/18.46%/0.52%, mole fraction, from Shaar Lake Mine Field,Xinjiang Province, China) with a feed pressure of 3.5 MPa. Subsequently, the Rectisol process is constructed to furtherly remove and capture the residual CO_(2)remained in light product gas from the VPSA process using cryogenic methanol(233.15 K, 100%(mass)) as absorbent. A final purified gas with CO_(2) concentration lower than 3% and a regenerated CO_(2) product with CO_(2) purity higher than 95% were achieved by using the Rectisol process. Comparisons indicate that the energy consumption is deceased from 2.143 MJ·kg^(-1) of the single Rectisol process to 1.008 MJ·kg^(-1) of the integrated VPSA & Rectisol process, which demonstrated that the deployed VPSA was an energy conservation process for CO_(2) capture from UCG syngas. Additionally, the high-value gas(e.g., CH_(4)) loss can be decreased and the effects of key operating parameters on the process performances were detailed.
基金financially supported by the National Key R&D Program of China(grant No.2019YFB1505000).
文摘The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production,which necessitate accurate prediction of gas-solid transfer behavior.In this work,a developed Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)model combined with the adsorption model is proposed.The developed CFD-DEM model is validated by comparing simulated results with experimental data and empirical correlation.Subsequently,the effect of particle packing structure and particle shapes on the dynamic adsorption process are analyzed in detail.The results reveal the mechanism of particle packing structure affecting axial velocity distribution,showing that uneven distribution of resistance on the outer flow channel side leads to uneven axial velocity distribution in the bed.Compared to cylindrical adsorbents,the use of spherical adsorbents results in a more uniform axial velocity distribution,consequently reducing bed pressure drop.The study holds significant potential for optimizing gas distribution and improving separation efficiency in future industrial applications.
基金support by the National Key Research and Development Program of China(grant No.2018YFE0111100)the National Nature Science Foundation of China(grant No.22078230)the Open Foundation of State Key Laboratory of Chemical Engineering(grant No.SKL-ChE-21B07).
文摘L-valve is often used as a non-mechanical valve for the circulation of solids in gas-solids fluidized bed(GSFB)due to its advantages in simple construction and easy control.The information on solids circu-lation rate as well as the hydrodynamics performance of the CFB with L-valve is of great importance for its better control and design.This paper proposes a Eulerian-Eulerian approach based numerical model integrating the computational fluid dynamics(CFD)with turbulent model,the kinetic theory of granular flow(KTGF)and the drag model,thus the solids circulation rate and the local phase velocity as well as solids volume fraction can be predicted simultaneously.With this model,the hydrodynamics perfor-mance of the full loop GSCFB with a L-valve is analyzed in detail.It is found that the drag model affects the simulation significantly and the(energy minimization multiscale)EMMS method shows good per-formance in the full-loop simulation of GSCFB.
