CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I ternary gas m...CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I ternary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis,compared with SF6 gas mixtures.The results confirm that the critical electric field strength of CF3I/c-C4F8/70%CO2 is greater than that of 30%SF6/70%CO2 when the CF3I content is greater than 17%.Moreover,a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field,and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures.The synergistic effects for CF3I/c-C4F8/70%N2 were most obvious when the c-C4F8 content was approximately 20%,and for CF3I/c-C4F8/70%CO2 when the c-C4F8 content was approximately 10%.On the basis of this research,CF3I/c-C4F8/70%N2 shows better insulation performance when the c-C4F8 content is in the15%–20%range.For CF3I/c-C4F8/70%CO2,when the c-C4F8 content is in the 10%–15%range,the gas mixtures have excellent performance.Hence,these gas systems might be used as alternative gas mixtures to SF6 in high-voltage equipment.展开更多
Based on industrial production with an annual capacity of million tons of methanol,ammonia/urea,etc.,a platform technology is developed for direct,green,efficient,and high-value mega-size utilization of the CO2-rich n...Based on industrial production with an annual capacity of million tons of methanol,ammonia/urea,etc.,a platform technology is developed for direct,green,efficient,and high-value mega-size utilization of the CO2-rich nature gas,which is the technology of CO2-rich natural gas dry reforming and hydrogen reaction.The following technologies are discussed,such as CO2-rich natural gas dry reforming integrated with the Fischer-Tropsch synthesis to olefins(FTO)technology for producing high value-added linear alpha olefins(LAO);CO2-rich natural gas dry reforming integrated with low carbon olefin linear hydroformylation technology to produce higher carbon alcohols;direct methanol production from CO2 and hydrogen;and the new cutting edge technology of photo-catalytic process.In addition,simple techno-economic evaluations of two technologies mentioned above are discussed.The CO2-rich natural gas dry reforming integrated with FTO technology can achieve about 30%of internal rate return(IRR),while the low carbon olefin linear hydroformylation technology could have a static payback period of 2.57 years when the capacity of 2-propylhexanol(2-PH)reaches 100 kt/a.Based on the mega-size green and high-efficient CO2-rich natural gas direct utilization technology,a hybrid energy and chemical production system framework with good prospects is preliminarily designed.A modern industry zone with an annual capacity of more than 10 Mt of CO2 converted to high value-added products is underway.展开更多
As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide(CO2)enhanced gas recovery(CO2-EGR) is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.B...As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide(CO2)enhanced gas recovery(CO2-EGR) is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state(EOS) module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional(3D)1/4 model(2.2 km×1 km×1 km) which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase(2 MPa) and uplift(7 mm) occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.展开更多
CO2 gas is a nonhydrocarbon gas, with a high economic value and a broad prospect for application. In the Huanghua Depression, there exist many genetic types of CO2 gases, i.e. organic CO2, thermal metamorphic CO2 and ...CO2 gas is a nonhydrocarbon gas, with a high economic value and a broad prospect for application. In the Huanghua Depression, there exist many genetic types of CO2 gases, i.e. organic CO2, thermal metamorphic CO2 and crust-mantle mixed CO2. The distribution of different types of CO2 gases is controlled by different factors. Organic CO2 that occurs mainly around the oil-generating center is associated with hydrocarbon gases as a secondary product and commonly far away from large faults. Thermal metamorphic CO2 occurs mainly in areas where carbonate strata are developed and igneous activity is strong, and tends to accumulate near large faults. CO2 of such an origin is higher in concentration than organic CO2, but lower than crust-mantle mixed CO2. Crust-mantle mixed CO2 occurs mainly along large faults. Its distribution is limited, but its purity is the highest.展开更多
Tube-type CO_2 gas sensors based on NASICON (Na Super Ion Conductor) material were fabricated.The material was synthesized by conventional sol-gel method,and the resulted powders were characterized by XRD.The tube-typ...Tube-type CO_2 gas sensors based on NASICON (Na Super Ion Conductor) material were fabricated.The material was synthesized by conventional sol-gel method,and the resulted powders were characterized by XRD.The tube-type CO_2 sensor was prepared with the sensing electrode Li_2CO_3-BaCO_3 binary carbonates in molar ratio 1:1.5.The concentration of CO_2 range from 300μg/g to 3000μg/g,the sensitivity of the sensor was 62.3 mV/decade.The response and recovery time (90%)corresponding to the switching change between 300μg/g and 1000μg/g CO_2 were 20 s and 2 min,respectively.If the sensing electrode was modified with binary oxides,the steady time of the sensor could be greatly reduced from 30 min to 5 min and the stability and humid-resistance of the sensor were improved.展开更多
Mixed matrix hollow fiber membranes(MMHFMs)filled with metal-organic frameworks(MOFs)have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and ...Mixed matrix hollow fiber membranes(MMHFMs)filled with metal-organic frameworks(MOFs)have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53(S-MIL-53)and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.展开更多
We calculated the uniform dielectric breakdown field strength of residual 30% CF3I/CO2 gas mixtures during the arc extinction process over the temperature range 300-3500 K at 0.1 MPa. The limiting reduced field streng...We calculated the uniform dielectric breakdown field strength of residual 30% CF3I/CO2 gas mixtures during the arc extinction process over the temperature range 300-3500 K at 0.1 MPa. The limiting reduced field strengths are decided by a balance of electron generation and loss based on chemical reactions estimated by the electron energy distribution function (EEDF), which employs the Boltzmann equation method with two-term expanding approximation in the steady-state Townsend (SST) condition. During the insulation recovery phase, the hot CF3I/CO2 gas mixtures have maximum dielectric strength at a temperature of about 1500 K. At room temperature 300 K, the electric strength after arc extinction (90.3 Td, 1 Td=10-21 V.m2) is only 38% of the original value before arc (234.9 Td). The adverse insulation recovery ability of CF3I/CO2 gas mixtures in arc extinction hinders its application in electric circuit breakers and other switchgears as an arc quenching and insulating medium.展开更多
Abstract: Types of polymerized molecular network structure and degree of bond breakdown for glass phases of magmatic inclusions and glassy matrix in volcanic rocks from the Shengli oilfield have been defined by the la...Abstract: Types of polymerized molecular network structure and degree of bond breakdown for glass phases of magmatic inclusions and glassy matrix in volcanic rocks from the Shengli oilfield have been defined by the laser Raman spectroscopic investigation. There are significant differences in types of polymerized molecular network structure and degree of bond breakdown of the magmatic glass phases between the non-CO2 and CO2 gas pools: magmatic glass phases of fluid inclusions and matrix in volcanic rocks from the CO2 gas pool contain more sheet network molecules and have a greater degree of bond beakdown than those from the non-CO2 gas pool; and when gas bubbles occur in evolving magma, magma saturated with volatile components has more sheet network molecules. The results suggest the magmadegassing mechanism of the formation of CO2 gas pools in the Shengli oilfield.展开更多
CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technol...CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of "thief zones". Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system (modified polyacry- lamide-methenamine-resorcinol gel system) to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were con- ducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indi- cate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guideli- nes for the deployment of theCO2-sensitive gel system for field applications.展开更多
Corrections of density effects resulting from air-parcel expansion/compression are important in interpreting eddy covariance fluxes of water vapor and CO2 when open-path systems are used. To account for these effects,...Corrections of density effects resulting from air-parcel expansion/compression are important in interpreting eddy covariance fluxes of water vapor and CO2 when open-path systems are used. To account for these effects, mean vertical velocity and perturbation of the density of dry air are two critical parameters in treating those physical processes responsible for density variations. Based on various underlying assumptions, different studies have obtained different formulas for the mean vertical velocity and perturbation of the density of dry air, leading to a number of approaches to correct density effects. In this study, we re-examine physical processes related to different assumptions that are made to formulate the density effects. Specifically, we re-examine the assumptions of a zero dry air flux and a zero moist air flux in the surface layer, used for treating density variations, and their implications for correcting density effects. It is found that physical processes in relation to the assumption of a zero dry air flux account for the influence of dry air expansion/compression on density variations. Meanwhile, physical processes in relation to the assumption of a zero moist air flux account for the influence of moist air expansion/compression on density variations. In this study, we also re-examine mixing ratio issues. Our results indicate that the assumption of a zero dry air flux favors the use of the mixing ratio relative to dry air, while the assumption of a zero moist air flux favors the use of the mixing ratio relative to the total moist air. Additionally, we compare different formula for the mean vertical velocity, generated by air-parcel expansion/compression, and for density effect corrections using eddy covariance data measured over three boreal ecosystems.展开更多
To increase the photoelectronic conversion efficiency of the single discharge tube and to meet the requirements of the laser cutting system, optimization of the discharge tube structure and gas flow field is necessary...To increase the photoelectronic conversion efficiency of the single discharge tube and to meet the requirements of the laser cutting system, optimization of the discharge tube structure and gas flow field is necessary. We present a computational fluid dynamic model to predict the gas flow characteristics of high-power fast-axial flow CO2 laser. A set of differential equations is used to describe the operation of the laser. Gas flow characteristics, are calculated. The effects of gas velocity and turbulence intensity on discharge stability are studied. Computational results are compared with experimental values, and a good agreement is observed. The method presented and the results obtained can make the design process more efficient.展开更多
The stable and crystalline phase of pure nano- structured CeO2 was directly synthesized by flame-assisted spray pyrolysis and solid state diffusion route. Different characterization techniques, including X-ray diffrac...The stable and crystalline phase of pure nano- structured CeO2 was directly synthesized by flame-assisted spray pyrolysis and solid state diffusion route. Different characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier trans- form infrared spectroscopy (FTIR), ultraviolet-visible (UV- Vis), and thermo gravimetric analysis (TGA) were employed to examine the structural, morphological, optical, and thermal properties of the final product. Similarly, the comparative carbon dioxide (CO2)-sensing response of as-synthesized CeO2 nanoparticles by both routes was also reported. The CeO2 nanoparticles synthesized by solid state diffusion method exhibit good sensitivity (3.38 %) at room temperature, low operating temperature (398 K), fast response time (32 s), and recovery time (36 s) along with good stability.展开更多
A novel porous aromatic framework, PAF-8, derived from tetraphenylsilane as basic building unit, was successfully synthesized via Friedel-Crafts alkylation reaction. This PAF material had high thermal stability as wel...A novel porous aromatic framework, PAF-8, derived from tetraphenylsilane as basic building unit, was successfully synthesized via Friedel-Crafts alkylation reaction. This PAF material had high thermal stability as well as high surface area (785 m^2 g^-1) calculated from the Brunauer-Emmett-Teller (BET) model. Meanwhile, PAF-8 possessed high performances in gas sorption and especially for CO2 separation.展开更多
CO2is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO2. Membrane gas separation is a fast growing CO2 capture technique, particularly gas ...CO2is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO2. Membrane gas separation is a fast growing CO2 capture technique, particularly gas separation by composite membranes. The separation of CO2 by a membrane is not just a process to physically sieve out of CO2 through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO2. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO2 in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO2 through membranes. Pure cellulose acetate(CA) and cellulose acetatetitania nanoparticle(CA-TiO2) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO2 membrane adsorbed more quantity of CO2 gas as compared to pure CA membrane. The high CO2 adsorption capacity may enhance the diffusion and solubility of CO2 in the CA-TiO2 composite membrane, which results in a better CO2 separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models.According to correlation factor R2, the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion.展开更多
基金supported by National Natural Science Foundation of China(No.51337006)。
文摘CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I ternary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis,compared with SF6 gas mixtures.The results confirm that the critical electric field strength of CF3I/c-C4F8/70%CO2 is greater than that of 30%SF6/70%CO2 when the CF3I content is greater than 17%.Moreover,a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field,and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures.The synergistic effects for CF3I/c-C4F8/70%N2 were most obvious when the c-C4F8 content was approximately 20%,and for CF3I/c-C4F8/70%CO2 when the c-C4F8 content was approximately 10%.On the basis of this research,CF3I/c-C4F8/70%N2 shows better insulation performance when the c-C4F8 content is in the15%–20%range.For CF3I/c-C4F8/70%CO2,when the c-C4F8 content is in the 10%–15%range,the gas mixtures have excellent performance.Hence,these gas systems might be used as alternative gas mixtures to SF6 in high-voltage equipment.
文摘Based on industrial production with an annual capacity of million tons of methanol,ammonia/urea,etc.,a platform technology is developed for direct,green,efficient,and high-value mega-size utilization of the CO2-rich nature gas,which is the technology of CO2-rich natural gas dry reforming and hydrogen reaction.The following technologies are discussed,such as CO2-rich natural gas dry reforming integrated with the Fischer-Tropsch synthesis to olefins(FTO)technology for producing high value-added linear alpha olefins(LAO);CO2-rich natural gas dry reforming integrated with low carbon olefin linear hydroformylation technology to produce higher carbon alcohols;direct methanol production from CO2 and hydrogen;and the new cutting edge technology of photo-catalytic process.In addition,simple techno-economic evaluations of two technologies mentioned above are discussed.The CO2-rich natural gas dry reforming integrated with FTO technology can achieve about 30%of internal rate return(IRR),while the low carbon olefin linear hydroformylation technology could have a static payback period of 2.57 years when the capacity of 2-propylhexanol(2-PH)reaches 100 kt/a.Based on the mega-size green and high-efficient CO2-rich natural gas direct utilization technology,a hybrid energy and chemical production system framework with good prospects is preliminarily designed.A modern industry zone with an annual capacity of more than 10 Mt of CO2 converted to high value-added products is underway.
基金funded by the National Natural Science Foundation of China(Grant No.NSFC51374147)the German Society for Petroleum and Coal Science and Technology(Grant No.DGMK680-4)
文摘As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide(CO2)enhanced gas recovery(CO2-EGR) is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state(EOS) module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional(3D)1/4 model(2.2 km×1 km×1 km) which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase(2 MPa) and uplift(7 mm) occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.
文摘CO2 gas is a nonhydrocarbon gas, with a high economic value and a broad prospect for application. In the Huanghua Depression, there exist many genetic types of CO2 gases, i.e. organic CO2, thermal metamorphic CO2 and crust-mantle mixed CO2. The distribution of different types of CO2 gases is controlled by different factors. Organic CO2 that occurs mainly around the oil-generating center is associated with hydrocarbon gases as a secondary product and commonly far away from large faults. Thermal metamorphic CO2 occurs mainly in areas where carbonate strata are developed and igneous activity is strong, and tends to accumulate near large faults. CO2 of such an origin is higher in concentration than organic CO2, but lower than crust-mantle mixed CO2. Crust-mantle mixed CO2 occurs mainly along large faults. Its distribution is limited, but its purity is the highest.
基金The authors acknowledge Natural Science Foundation of China (No.60174033);ministry of education and Innovation Foundation of Jilin University
文摘Tube-type CO_2 gas sensors based on NASICON (Na Super Ion Conductor) material were fabricated.The material was synthesized by conventional sol-gel method,and the resulted powders were characterized by XRD.The tube-type CO_2 sensor was prepared with the sensing electrode Li_2CO_3-BaCO_3 binary carbonates in molar ratio 1:1.5.The concentration of CO_2 range from 300μg/g to 3000μg/g,the sensitivity of the sensor was 62.3 mV/decade.The response and recovery time (90%)corresponding to the switching change between 300μg/g and 1000μg/g CO_2 were 20 s and 2 min,respectively.If the sensing electrode was modified with binary oxides,the steady time of the sensor could be greatly reduced from 30 min to 5 min and the stability and humid-resistance of the sensor were improved.
基金the financial support from the National Natural Science Foundation of China(No.21436009)
文摘Mixed matrix hollow fiber membranes(MMHFMs)filled with metal-organic frameworks(MOFs)have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53(S-MIL-53)and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.
基金supported by National Natural Science Foundation of China(No.10875093)
文摘We calculated the uniform dielectric breakdown field strength of residual 30% CF3I/CO2 gas mixtures during the arc extinction process over the temperature range 300-3500 K at 0.1 MPa. The limiting reduced field strengths are decided by a balance of electron generation and loss based on chemical reactions estimated by the electron energy distribution function (EEDF), which employs the Boltzmann equation method with two-term expanding approximation in the steady-state Townsend (SST) condition. During the insulation recovery phase, the hot CF3I/CO2 gas mixtures have maximum dielectric strength at a temperature of about 1500 K. At room temperature 300 K, the electric strength after arc extinction (90.3 Td, 1 Td=10-21 V.m2) is only 38% of the original value before arc (234.9 Td). The adverse insulation recovery ability of CF3I/CO2 gas mixtures in arc extinction hinders its application in electric circuit breakers and other switchgears as an arc quenching and insulating medium.
基金This research was supported by the National Natural Science Foundation of China grant 49573186.
文摘Abstract: Types of polymerized molecular network structure and degree of bond breakdown for glass phases of magmatic inclusions and glassy matrix in volcanic rocks from the Shengli oilfield have been defined by the laser Raman spectroscopic investigation. There are significant differences in types of polymerized molecular network structure and degree of bond breakdown of the magmatic glass phases between the non-CO2 and CO2 gas pools: magmatic glass phases of fluid inclusions and matrix in volcanic rocks from the CO2 gas pool contain more sheet network molecules and have a greater degree of bond beakdown than those from the non-CO2 gas pool; and when gas bubbles occur in evolving magma, magma saturated with volatile components has more sheet network molecules. The results suggest the magmadegassing mechanism of the formation of CO2 gas pools in the Shengli oilfield.
基金financial support from the National Basic Research Program of China(2015CB251201)the Fundamental Research Funds for the Central Universities(15CX06024A)the Program for Changjiang Scholars and Innovative Research Team in University(IRT1294 and IRT1086)
文摘CO2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of "thief zones". Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system (modified polyacry- lamide-methenamine-resorcinol gel system) to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were con- ducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indi- cate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guideli- nes for the deployment of theCO2-sensitive gel system for field applications.
文摘Corrections of density effects resulting from air-parcel expansion/compression are important in interpreting eddy covariance fluxes of water vapor and CO2 when open-path systems are used. To account for these effects, mean vertical velocity and perturbation of the density of dry air are two critical parameters in treating those physical processes responsible for density variations. Based on various underlying assumptions, different studies have obtained different formulas for the mean vertical velocity and perturbation of the density of dry air, leading to a number of approaches to correct density effects. In this study, we re-examine physical processes related to different assumptions that are made to formulate the density effects. Specifically, we re-examine the assumptions of a zero dry air flux and a zero moist air flux in the surface layer, used for treating density variations, and their implications for correcting density effects. It is found that physical processes in relation to the assumption of a zero dry air flux account for the influence of dry air expansion/compression on density variations. Meanwhile, physical processes in relation to the assumption of a zero moist air flux account for the influence of moist air expansion/compression on density variations. In this study, we also re-examine mixing ratio issues. Our results indicate that the assumption of a zero dry air flux favors the use of the mixing ratio relative to dry air, while the assumption of a zero moist air flux favors the use of the mixing ratio relative to the total moist air. Additionally, we compare different formula for the mean vertical velocity, generated by air-parcel expansion/compression, and for density effect corrections using eddy covariance data measured over three boreal ecosystems.
基金supported by the National Key Technology Research and Development Program under Grant No.2007BAF11B01
文摘To increase the photoelectronic conversion efficiency of the single discharge tube and to meet the requirements of the laser cutting system, optimization of the discharge tube structure and gas flow field is necessary. We present a computational fluid dynamic model to predict the gas flow characteristics of high-power fast-axial flow CO2 laser. A set of differential equations is used to describe the operation of the laser. Gas flow characteristics, are calculated. The effects of gas velocity and turbulence intensity on discharge stability are studied. Computational results are compared with experimental values, and a good agreement is observed. The method presented and the results obtained can make the design process more efficient.
文摘The stable and crystalline phase of pure nano- structured CeO2 was directly synthesized by flame-assisted spray pyrolysis and solid state diffusion route. Different characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier trans- form infrared spectroscopy (FTIR), ultraviolet-visible (UV- Vis), and thermo gravimetric analysis (TGA) were employed to examine the structural, morphological, optical, and thermal properties of the final product. Similarly, the comparative carbon dioxide (CO2)-sensing response of as-synthesized CeO2 nanoparticles by both routes was also reported. The CeO2 nanoparticles synthesized by solid state diffusion method exhibit good sensitivity (3.38 %) at room temperature, low operating temperature (398 K), fast response time (32 s), and recovery time (36 s) along with good stability.
基金the financial support of National Basic Research Program of China(973 Program,Nos.2012CB821700 and 2014CB931804)Major International(Regional) Joint Research Project of NSFC(No.21120102034)NSFC Project(Nos. 21531003 and 21503038)
文摘A novel porous aromatic framework, PAF-8, derived from tetraphenylsilane as basic building unit, was successfully synthesized via Friedel-Crafts alkylation reaction. This PAF material had high thermal stability as well as high surface area (785 m^2 g^-1) calculated from the Brunauer-Emmett-Teller (BET) model. Meanwhile, PAF-8 possessed high performances in gas sorption and especially for CO2 separation.
基金supported by Higher Education Commission (HEC) Pakistan
文摘CO2is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO2. Membrane gas separation is a fast growing CO2 capture technique, particularly gas separation by composite membranes. The separation of CO2 by a membrane is not just a process to physically sieve out of CO2 through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO2. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO2 in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO2 through membranes. Pure cellulose acetate(CA) and cellulose acetatetitania nanoparticle(CA-TiO2) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO2 membrane adsorbed more quantity of CO2 gas as compared to pure CA membrane. The high CO2 adsorption capacity may enhance the diffusion and solubility of CO2 in the CA-TiO2 composite membrane, which results in a better CO2 separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models.According to correlation factor R2, the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion.