The effects of the secondary gradient crystallizing pressure, temperature and time on the purity and crystallization ratio of andrographolide were investigated via single factor experiments. The shape of crystal was...The effects of the secondary gradient crystallizing pressure, temperature and time on the purity and crystallization ratio of andrographolide were investigated via single factor experiments. The shape of crystal was observed with scanning electron microscopy (SEM). The purity of andrographolide was determined by high pressure liquid chromatography (HPLC). It was found that the optimized parameters were pressure 14 MPa, temperature 55℃, time 60 min, and CO2 flow rate 15 L min-1, under these conditions the particle of andrographolide was much smaller, the crystal of andrographolide was distributed in floccule on crystal board,with the purity of andrographolide 92.5%, the crystallization ratio 48.9%.展开更多
The thermal decomposition of 2, 2'-azobis (isobutyronitrile) (AIBN) in supercritical CO2 with cosolvent methanol or cyclohexane has been studied by using UV/Vis spectroscopic method at 335.15 K and at 12.0 MPa and...The thermal decomposition of 2, 2'-azobis (isobutyronitrile) (AIBN) in supercritical CO2 with cosolvent methanol or cyclohexane has been studied by using UV/Vis spectroscopic method at 335.15 K and at 12.0 MPa and 14.0 MPa. Both of the cosolvents can accelerate the decomposition rate, and the effect of methanol is more significant than that of the cyclohexane.展开更多
The effect of cosolvent on the palladium catalyst which catalyze alkoxycarbonylation of allyl bromide in supercritical CO2 has been investigated. It was found that a small amount of cosolvent such as ethanol, CH2Cl2 a...The effect of cosolvent on the palladium catalyst which catalyze alkoxycarbonylation of allyl bromide in supercritical CO2 has been investigated. It was found that a small amount of cosolvent such as ethanol, CH2Cl2 and cyclohexane can affect both reaction yields and selectivities largely. Ethanol was the most favorable cosolvent for increasing the total yield of unsaturated esters and the selectivity of 3-butenoic acid ester. Using cosolvent ethanol and cocatalyst FeCl2 simultaneously can lead to better reaction results.展开更多
The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to ...The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to preparing semi-interpenetrating polymer network (semi-IPN) of SR and poly(methyl methylacrylate) (PMMA). The SR/PMMA semi-IPNs were characterized by scanning electron microscopy (SEM) and dynamic mechanical analyzer (DMA).展开更多
The effect of cosolvent cyclohexane, chloroform, and acetonitrile on the keto-enol tautomeric equilibrium of ethyl acetoacetate in supercritical CO2 was studied by UV-Vis spectroscopy over the pressure range from 76 t...The effect of cosolvent cyclohexane, chloroform, and acetonitrile on the keto-enol tautomeric equilibrium of ethyl acetoacetate in supercritical CO2 was studied by UV-Vis spectroscopy over the pressure range from 76 to 110 bar at 308.15 K. It was found that the equilibrium constant decreases with increasing polarity of the cosolvents.展开更多
Extraction of heavy metal ions from solid matrix by means of an incorporation of chelating agents with supercritical carbon dioxide(scCO2) was investigated experimentally. Four commercially available chelating agent...Extraction of heavy metal ions from solid matrix by means of an incorporation of chelating agents with supercritical carbon dioxide(scCO2) was investigated experimentally. Four commercially available chelating agents, diethylammonium diethyldithiocarbamate(Et2NH2DDC), trifluoroacetylacetone(TFA), hexafluoroacetylacetone(HFA) and thenoyltrifluoroacetone(TTA) were tested. The extraction experiments were conducted at 50 °C and 1.39×107― 2.80×107 Pa. According to the experimental results, for the extraction of Cu2+, all the chelating agents investigated here are effective. For other metal ions, such as Pb2+, Ni2+ and Cd2+, Et2NH2DDC exhibited a better extraction result, while other chelating agents were less effective. This investigation is expected to provide a tentative evaluation on the scCO2-based metal extraction from solid media.展开更多
Oxidation of n-butanol and 2-pentanol using molecular oxygen in supercritical (SC) CO2 with and without co-solvent is investigated. The results showed that the reaction selectivity is high when the reaction is carried...Oxidation of n-butanol and 2-pentanol using molecular oxygen in supercritical (SC) CO2 with and without co-solvent is investigated. The results showed that the reaction selectivity is high when the reaction is carried out in SC CO2. It has been observed that co-solvent affects conversion and selectivity of the reaction considerably.展开更多
Introduction The use of supercritical fluids such as supercritical CO<sub>2</sub>(scCO<sub>2</sub>) has provided a ’clean’ and effective alternative to traditional methods of protein delive...Introduction The use of supercritical fluids such as supercritical CO<sub>2</sub>(scCO<sub>2</sub>) has provided a ’clean’ and effective alternative to traditional methods of protein delivery systems.Here。展开更多
Solid phase transition of the a form crystals to the 3 form crystals in syndiotactic polystyrene (sPS) samples has occurred in supercritical CO2. This transformation is different from those detected under other condit...Solid phase transition of the a form crystals to the 3 form crystals in syndiotactic polystyrene (sPS) samples has occurred in supercritical CO2. This transformation is different from those detected under other conditions. The effects of some factors (e.g. time, temperature, and pressure) on the solid phase transformation of sPS in supercritical CO2 were analyzed in detail. Experimental results show that longer time, higher temperature or higher pressure favors the transformation of the a form crystals to the beta form crystals.展开更多
The experiment was conducted to investigate the heat transfer performance of supercritical CO_2 in a casing heat exchanger by comparing their heat transfer,entropy production unit number,non-dimensional entropy produc...The experiment was conducted to investigate the heat transfer performance of supercritical CO_2 in a casing heat exchanger by comparing their heat transfer,entropy production unit number,non-dimensional entropy production rate and field synergy factor.The results show that both heat transfer and entropy production unit number in four tubes decrease with water temperature increasing.Heat transfer and entropy production unit number in multiple tubes( i. e.,triple straight tube and double helix tube) is higher than their single counterparts; the non-dimensional entropy production rate increases with water temperature. Non-dimensional entropy production rate of triple straight tube and double helix tube is far below the single tube. Field synergy factor of double helix tube is much higher than that of the triple straight tube under the same condition. Further experiment was carried out in double helix tube,under various CO_2 pressure and inlet water temperature,the results are analyzed and reported in this paper.展开更多
The deposition of a Cu seed layer film is investigated by supercritical fluid deposition (SCFD) using H2 as a reducing agent for Bis(2,2,6,6-tetramethyl-3,5- heptanedionato) copper in supercritical CO2 (scCO2). ...The deposition of a Cu seed layer film is investigated by supercritical fluid deposition (SCFD) using H2 as a reducing agent for Bis(2,2,6,6-tetramethyl-3,5- heptanedionato) copper in supercritical CO2 (scCO2). The effects of deposition temperature, precursor, and H2 concentration are investigated to optimize Cu deposition. Continuous metallic Cu films are deposited on Ru substrates at 190 ℃ when a 0.002 mol/L Cu precursor is introduced with 0.75 mol/L H2. A Cu precursor concentration higher than 0.002 mol/L is found to have negative effects on the surface qualities of Cu films. For a H2 concentration above 0.56 mol/L, the root-mean-square (RMS) roughness of a Cu film decreases as the H2 concentration increases. Finally, a 20-nm thick Cu film with a smooth surface, which is required as a seed layer in advanced interconnects, is successfully deposited at a high H2 concentration (0.75 tool/L).展开更多
The solvatochromic behavior of acetone in supercritical CO? was investigated from 75 bar to 239 bar and at 318.15K. A clustering model is proposed to investigate the formation of solute-solvent and solute-solute clust...The solvatochromic behavior of acetone in supercritical CO? was investigated from 75 bar to 239 bar and at 318.15K. A clustering model is proposed to investigate the formation of solute-solvent and solute-solute clusters, based on the solvatochromic study and some reasonable assumptions. At lower pressures, there were more than one solute molecules in one cluster. At higher pressures, however, each cluster only contained one solute and the clustering of solute-solvent was dominant.展开更多
To construct the heterojunctions of TiO2 with other compounds is of great importance for overcoming its inherent shortages and improving the visible-light photocatalytic performance.Here we propose the construction of...To construct the heterojunctions of TiO2 with other compounds is of great importance for overcoming its inherent shortages and improving the visible-light photocatalytic performance.Here we propose the construction of TiO2/covalent organic framework(COF)heterojunction with tight connection by a supercritical CO2(SC CO2)method,which helps bridging the transformation paths for photo-induced charge between T i02 and COF.The produced T i02/COF heterojunction performs a H2 evolution of 3,962 nmol·g^-1·h^-1 under visible-light irradiation,which is-25 times higher than that of pure TiO2 and 4.5 folds higher than that of TiO2/COF synthesized by the conventional solvothermal method.This study opens up new possibilities for constructing heterojunctions for solar energy utilization.展开更多
Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/d...Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experiment...展开更多
Supercritical CO2 fracturing is considered to be a new method for efficient exploitation of unconventional reservoirs,such as shale gas,coal bed methane,and tight sand stone gas.Supercritical CO2 has many special prop...Supercritical CO2 fracturing is considered to be a new method for efficient exploitation of unconventional reservoirs,such as shale gas,coal bed methane,and tight sand stone gas.Supercritical CO2 has many special properties including low viscosity,high diffusion coefficient,and lack of surface tension,which brings about great advantages for fracturing.However,these properties also cause several problems,such as difficulty in proppant transportation,high friction loss,and high pump displacement.In this paper,the above problems were analyzed by combining field test with laboratory study and specific solutions to these problems are given.The high frictionloss in the pipeline could be reduced by developing a new drag reducing agent and selecting large-size casing.Besides,for the problem of poor capacity in proppant carrying and sand plug,the methods of adding tackifier into supercritical CO2,increasing pump displacement and selecting ultralow density proppants are proposed.Moreover,for the problem of fast leak-off and high requirement for pump displacement,the displacement can be increased or the pad fluid can be injected into the reservoir.After solving the above three problems,the field test of supercritical CO2 fracturing can be conducted.The research results can promote the industrialization process of supercritical CO2 fracturing.展开更多
The utilization of sensible waste heat such as flue gas and industrial surplus heat is essential for energy saving. Supercritical CO2 power generation cycle is a promising way to be used in this field. In this paper, ...The utilization of sensible waste heat such as flue gas and industrial surplus heat is essential for energy saving. Supercritical CO2 power generation cycle is a promising way to be used in this field. In this paper, a new supercritical CO2 Rankine cycle coupled with an absorption refrigeration cycle is proposed, which consists of a reheating supercritical CO2 cycle, a mixed-effect Li Br-H2O absorption refrigeration cycle and solar subsystem including evacuated-tube collector and a hot water storage tank. The system has four variants according to the presence or absence of solar subsystem and net cooling energy output. The thermodynamic model of the proposed system was established and its performance was evaluated. The proposed system is able to realize cascade utilization of flue gas waste heat and efficient conversion of solar energy. It has much higher thermodynamic efficiency than the reference system(i.e., the conventional supercritical CO2 Brayton cycle). Taking combined power and cooling system driven by flue gas waste heat and solar energy as an example, its thermal efficiency and exergy efficiency are 20.37% and 54.18% respectively, compared with the 14.74% and 35.96% of the reference system. Energy Utilization Diagrams(EUD) are implemented to investigate the irreversible losses and variation of the exergy destruction in the energy conversion process. Parametric analysis in two key parameters is conducted to provide guidance for the system optimal design.展开更多
Research on applying a supercritical carbon dioxide power cycle (S-CO2) to concentrating solar power (CSP) instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is s...Research on applying a supercritical carbon dioxide power cycle (S-CO2) to concentrating solar power (CSP) instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is suitable for CSP owing to its compactness, higher efficiency, and dry-cooling capability. At the Korea Institute of Energy Research (KIER), to implement an S-CO2 system, a 10 kWe class test loop with a turbine- alternator-compressor (TAC) using gas foil bearings was developed. A basic sub-kWe class test loop with a high- speed radial type turbo-generator and a test loop with a capability of tens of kWe with an axial type turbo- generator were then developed. To solve the technical bottleneck of S-CO2 turbomachinery, a partial admission nozzle and oil-lubrication bearings were used in the turbo- generators. To experience the closed-power cycle and develop an operational strategy of S-CO2 operated at high pressure, an organic Rankine cycle (ORC) operating test using a refrigerant as the working fluid was conducted owing to its operational capability at relatively low- pressure conditions of approximately 30 to 40 bar. By operating the sub-kWe class test loop using R134a as the working fluid instead of CO2, an average turbine power of 400 W was obtained.展开更多
Supercritical(SC) CO2 anti-solvent induced polymer epitaxy(SAIPE) method was used to help prepare nanohybrid carbon nanotubes(CNTs) wrapped with polyvinyl alcohol(PVA) nanocrystals.With the variation of a seri...Supercritical(SC) CO2 anti-solvent induced polymer epitaxy(SAIPE) method was used to help prepare nanohybrid carbon nanotubes(CNTs) wrapped with polyvinyl alcohol(PVA) nanocrystals.With the variation of a series of experimental conditions or peripheral effects,such as PVA concentration,CNTs concentration,and SC CO2 pressure,the optimal experimental variables for PVA-nanocrystals growing on CNTs have been found.The adsorption of polymer on CNTs via multiple weak molecular interactions has been studied by Fourier transform infrared(FTIR) spectroscopy and Raman spectroscopy.The mechanism about the formation of PVA nanocrystals on CNTs can be suggested through the experimental phenomena.These CNTs wrapped with PVA nanocrystals can be directly used as nanofillers to fabricate PVA composite fibers reinforced with CNTs by electrospinning.展开更多
Foamable high melt strength polypropylene (HMSPP) was prepared by grafting styrene (St) onto polypropylene (PP) and simultaneously introducing poly- dimethylsiloxane (PDMS) through a one-step melt extru- sion ...Foamable high melt strength polypropylene (HMSPP) was prepared by grafting styrene (St) onto polypropylene (PP) and simultaneously introducing poly- dimethylsiloxane (PDMS) through a one-step melt extru- sion process. The effect of PDMS viscosity on the foaming behavior of HMSPP was systematically investigated using supercritical CO2 as the foaming agent. The results show that the addition of PDMS has little effect on the grafting reaction of St and HMSPP exhibits enhanced elastic response and obvious strain hardening effect. Though the CO2 solubility of HMSPP with PDMS (PDMS-HMSPP) is lower than that of HMSPP without PDMS, especially for PDMS with low viscosity, the PDMS-HMSPP foams exhibit narrow cell size distribution and high cell density. The fracture morphology of PDMS-HMSPP shows that PDMS with low viscosity disperses more easily and uniformly in HMSPP matrix, leading to form small domains during the extrusion process. These small domains act as bubble nucleation sites and thus may be responsible for the improved foaming performance of HMSPP.展开更多
基金financially supported by the National Natura1 Science Foundation of China(29976008)
文摘The effects of the secondary gradient crystallizing pressure, temperature and time on the purity and crystallization ratio of andrographolide were investigated via single factor experiments. The shape of crystal was observed with scanning electron microscopy (SEM). The purity of andrographolide was determined by high pressure liquid chromatography (HPLC). It was found that the optimized parameters were pressure 14 MPa, temperature 55℃, time 60 min, and CO2 flow rate 15 L min-1, under these conditions the particle of andrographolide was much smaller, the crystal of andrographolide was distributed in floccule on crystal board,with the purity of andrographolide 92.5%, the crystallization ratio 48.9%.
文摘The thermal decomposition of 2, 2'-azobis (isobutyronitrile) (AIBN) in supercritical CO2 with cosolvent methanol or cyclohexane has been studied by using UV/Vis spectroscopic method at 335.15 K and at 12.0 MPa and 14.0 MPa. Both of the cosolvents can accelerate the decomposition rate, and the effect of methanol is more significant than that of the cyclohexane.
文摘The effect of cosolvent on the palladium catalyst which catalyze alkoxycarbonylation of allyl bromide in supercritical CO2 has been investigated. It was found that a small amount of cosolvent such as ethanol, CH2Cl2 and cyclohexane can affect both reaction yields and selectivities largely. Ethanol was the most favorable cosolvent for increasing the total yield of unsaturated esters and the selectivity of 3-butenoic acid ester. Using cosolvent ethanol and cocatalyst FeCl2 simultaneously can lead to better reaction results.
基金This work was supported by the National Natural Science Foundation of China (50173030).
文摘The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to preparing semi-interpenetrating polymer network (semi-IPN) of SR and poly(methyl methylacrylate) (PMMA). The SR/PMMA semi-IPNs were characterized by scanning electron microscopy (SEM) and dynamic mechanical analyzer (DMA).
基金This work was financially support by National Basic Research Project(G2000048010).
文摘The effect of cosolvent cyclohexane, chloroform, and acetonitrile on the keto-enol tautomeric equilibrium of ethyl acetoacetate in supercritical CO2 was studied by UV-Vis spectroscopy over the pressure range from 76 to 110 bar at 308.15 K. It was found that the equilibrium constant decreases with increasing polarity of the cosolvents.
基金Supported by the National Natural Science Foundation of China(Nos.20776066, 20976079)
文摘Extraction of heavy metal ions from solid matrix by means of an incorporation of chelating agents with supercritical carbon dioxide(scCO2) was investigated experimentally. Four commercially available chelating agents, diethylammonium diethyldithiocarbamate(Et2NH2DDC), trifluoroacetylacetone(TFA), hexafluoroacetylacetone(HFA) and thenoyltrifluoroacetone(TTA) were tested. The extraction experiments were conducted at 50 °C and 1.39×107― 2.80×107 Pa. According to the experimental results, for the extraction of Cu2+, all the chelating agents investigated here are effective. For other metal ions, such as Pb2+, Ni2+ and Cd2+, Et2NH2DDC exhibited a better extraction result, while other chelating agents were less effective. This investigation is expected to provide a tentative evaluation on the scCO2-based metal extraction from solid media.
基金supported by National Natural Science Foundation of China(20073056).
文摘Oxidation of n-butanol and 2-pentanol using molecular oxygen in supercritical (SC) CO2 with and without co-solvent is investigated. The results showed that the reaction selectivity is high when the reaction is carried out in SC CO2. It has been observed that co-solvent affects conversion and selectivity of the reaction considerably.
文摘Introduction The use of supercritical fluids such as supercritical CO<sub>2</sub>(scCO<sub>2</sub>) has provided a ’clean’ and effective alternative to traditional methods of protein delivery systems.Here。
文摘Solid phase transition of the a form crystals to the 3 form crystals in syndiotactic polystyrene (sPS) samples has occurred in supercritical CO2. This transformation is different from those detected under other conditions. The effects of some factors (e.g. time, temperature, and pressure) on the solid phase transformation of sPS in supercritical CO2 were analyzed in detail. Experimental results show that longer time, higher temperature or higher pressure favors the transformation of the a form crystals to the beta form crystals.
基金Hujiang Foundation of China(No.D14003)Yangtze River Delta Technology Joint Research,China(No.10195811000)
文摘The experiment was conducted to investigate the heat transfer performance of supercritical CO_2 in a casing heat exchanger by comparing their heat transfer,entropy production unit number,non-dimensional entropy production rate and field synergy factor.The results show that both heat transfer and entropy production unit number in four tubes decrease with water temperature increasing.Heat transfer and entropy production unit number in multiple tubes( i. e.,triple straight tube and double helix tube) is higher than their single counterparts; the non-dimensional entropy production rate increases with water temperature. Non-dimensional entropy production rate of triple straight tube and double helix tube is far below the single tube. Field synergy factor of double helix tube is much higher than that of the triple straight tube under the same condition. Further experiment was carried out in double helix tube,under various CO_2 pressure and inlet water temperature,the results are analyzed and reported in this paper.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50901086 and 51072118)the Shanghai Shuguang Project,China (Grant No. 09SG46)+2 种基金the Science Foundation for the Excellent Youth Scholars of Shanghai Municipal Education Commission,China (Grant No. slg10032)the Qianjiang Project of Zhejiang Province,China (Grant No. 2010R10047)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘The deposition of a Cu seed layer film is investigated by supercritical fluid deposition (SCFD) using H2 as a reducing agent for Bis(2,2,6,6-tetramethyl-3,5- heptanedionato) copper in supercritical CO2 (scCO2). The effects of deposition temperature, precursor, and H2 concentration are investigated to optimize Cu deposition. Continuous metallic Cu films are deposited on Ru substrates at 190 ℃ when a 0.002 mol/L Cu precursor is introduced with 0.75 mol/L H2. A Cu precursor concentration higher than 0.002 mol/L is found to have negative effects on the surface qualities of Cu films. For a H2 concentration above 0.56 mol/L, the root-mean-square (RMS) roughness of a Cu film decreases as the H2 concentration increases. Finally, a 20-nm thick Cu film with a smooth surface, which is required as a seed layer in advanced interconnects, is successfully deposited at a high H2 concentration (0.75 tool/L).
文摘The solvatochromic behavior of acetone in supercritical CO? was investigated from 75 bar to 239 bar and at 318.15K. A clustering model is proposed to investigate the formation of solute-solvent and solute-solute clusters, based on the solvatochromic study and some reasonable assumptions. At lower pressures, there were more than one solute molecules in one cluster. At higher pressures, however, each cluster only contained one solute and the clustering of solute-solvent was dominant.
基金The authors thank the financial supports from M inistry of Science and Technology of China(No.2017YFA0403003)the National Natural Science Foundation of China(Nos.21525316 and 21673254)+1 种基金Chinese Academy of Sciences(No.QYZDYSSW-SLH013)Beijing Municipal Science&Technology Commission(No.Z191100007219009).
文摘To construct the heterojunctions of TiO2 with other compounds is of great importance for overcoming its inherent shortages and improving the visible-light photocatalytic performance.Here we propose the construction of TiO2/covalent organic framework(COF)heterojunction with tight connection by a supercritical CO2(SC CO2)method,which helps bridging the transformation paths for photo-induced charge between T i02 and COF.The produced T i02/COF heterojunction performs a H2 evolution of 3,962 nmol·g^-1·h^-1 under visible-light irradiation,which is-25 times higher than that of pure TiO2 and 4.5 folds higher than that of TiO2/COF synthesized by the conventional solvothermal method.This study opens up new possibilities for constructing heterojunctions for solar energy utilization.
基金supported by the National Natural Science Foundation of China (20506014)
文摘Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experiment...
基金the National Natural Science Foundation of China(Grant Nos.51221003,51874318)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2017ZX05039-003).
文摘Supercritical CO2 fracturing is considered to be a new method for efficient exploitation of unconventional reservoirs,such as shale gas,coal bed methane,and tight sand stone gas.Supercritical CO2 has many special properties including low viscosity,high diffusion coefficient,and lack of surface tension,which brings about great advantages for fracturing.However,these properties also cause several problems,such as difficulty in proppant transportation,high friction loss,and high pump displacement.In this paper,the above problems were analyzed by combining field test with laboratory study and specific solutions to these problems are given.The high frictionloss in the pipeline could be reduced by developing a new drag reducing agent and selecting large-size casing.Besides,for the problem of poor capacity in proppant carrying and sand plug,the methods of adding tackifier into supercritical CO2,increasing pump displacement and selecting ultralow density proppants are proposed.Moreover,for the problem of fast leak-off and high requirement for pump displacement,the displacement can be increased or the pad fluid can be injected into the reservoir.After solving the above three problems,the field test of supercritical CO2 fracturing can be conducted.The research results can promote the industrialization process of supercritical CO2 fracturing.
基金support of the China Postdoctoral Science Foundation(No.2018M641288)the Science and Technology Project of China Electric Power Planning&Engineering Institute(No.K201730-X)。
文摘The utilization of sensible waste heat such as flue gas and industrial surplus heat is essential for energy saving. Supercritical CO2 power generation cycle is a promising way to be used in this field. In this paper, a new supercritical CO2 Rankine cycle coupled with an absorption refrigeration cycle is proposed, which consists of a reheating supercritical CO2 cycle, a mixed-effect Li Br-H2O absorption refrigeration cycle and solar subsystem including evacuated-tube collector and a hot water storage tank. The system has four variants according to the presence or absence of solar subsystem and net cooling energy output. The thermodynamic model of the proposed system was established and its performance was evaluated. The proposed system is able to realize cascade utilization of flue gas waste heat and efficient conversion of solar energy. It has much higher thermodynamic efficiency than the reference system(i.e., the conventional supercritical CO2 Brayton cycle). Taking combined power and cooling system driven by flue gas waste heat and solar energy as an example, its thermal efficiency and exergy efficiency are 20.37% and 54.18% respectively, compared with the 14.74% and 35.96% of the reference system. Energy Utilization Diagrams(EUD) are implemented to investigate the irreversible losses and variation of the exergy destruction in the energy conversion process. Parametric analysis in two key parameters is conducted to provide guidance for the system optimal design.
文摘Research on applying a supercritical carbon dioxide power cycle (S-CO2) to concentrating solar power (CSP) instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is suitable for CSP owing to its compactness, higher efficiency, and dry-cooling capability. At the Korea Institute of Energy Research (KIER), to implement an S-CO2 system, a 10 kWe class test loop with a turbine- alternator-compressor (TAC) using gas foil bearings was developed. A basic sub-kWe class test loop with a high- speed radial type turbo-generator and a test loop with a capability of tens of kWe with an axial type turbo- generator were then developed. To solve the technical bottleneck of S-CO2 turbomachinery, a partial admission nozzle and oil-lubrication bearings were used in the turbo- generators. To experience the closed-power cycle and develop an operational strategy of S-CO2 operated at high pressure, an organic Rankine cycle (ORC) operating test using a refrigerant as the working fluid was conducted owing to its operational capability at relatively low- pressure conditions of approximately 30 to 40 bar. By operating the sub-kWe class test loop using R134a as the working fluid instead of CO2, an average turbine power of 400 W was obtained.
基金Supported by the the National Natural Science Foundation of China(Nos.20804040, 20974102, 50955010, 51173170, 21101141, 51003098), the Program for New Century Excellent Talents in Universities(NCET) and the Open Fund of Key Laboratory of Applied Surface and Colloid Chemistry(Shaanxi Normal University) of Ministry of Education of China(No.201201).
文摘Supercritical(SC) CO2 anti-solvent induced polymer epitaxy(SAIPE) method was used to help prepare nanohybrid carbon nanotubes(CNTs) wrapped with polyvinyl alcohol(PVA) nanocrystals.With the variation of a series of experimental conditions or peripheral effects,such as PVA concentration,CNTs concentration,and SC CO2 pressure,the optimal experimental variables for PVA-nanocrystals growing on CNTs have been found.The adsorption of polymer on CNTs via multiple weak molecular interactions has been studied by Fourier transform infrared(FTIR) spectroscopy and Raman spectroscopy.The mechanism about the formation of PVA nanocrystals on CNTs can be suggested through the experimental phenomena.These CNTs wrapped with PVA nanocrystals can be directly used as nanofillers to fabricate PVA composite fibers reinforced with CNTs by electrospinning.
基金Acknowledgements This work was financially supported by National Natural Science Foundation of China (Grant Nos. 21476085 and 21306047), Fundamental Research Funds for the Central Universities of China (22A201514016 222201314051).
文摘Foamable high melt strength polypropylene (HMSPP) was prepared by grafting styrene (St) onto polypropylene (PP) and simultaneously introducing poly- dimethylsiloxane (PDMS) through a one-step melt extru- sion process. The effect of PDMS viscosity on the foaming behavior of HMSPP was systematically investigated using supercritical CO2 as the foaming agent. The results show that the addition of PDMS has little effect on the grafting reaction of St and HMSPP exhibits enhanced elastic response and obvious strain hardening effect. Though the CO2 solubility of HMSPP with PDMS (PDMS-HMSPP) is lower than that of HMSPP without PDMS, especially for PDMS with low viscosity, the PDMS-HMSPP foams exhibit narrow cell size distribution and high cell density. The fracture morphology of PDMS-HMSPP shows that PDMS with low viscosity disperses more easily and uniformly in HMSPP matrix, leading to form small domains during the extrusion process. These small domains act as bubble nucleation sites and thus may be responsible for the improved foaming performance of HMSPP.