Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Numerical Simulation of Partitioning and Storage of Impure CO<sub>2</sub> in a Saline Aquifer at the Shenhua CCS Site, China
No full textCarbon capture and storage (CCS) is a key technology to control emissions of CO2 and mitigate climate change. Coinjection of CO2 with major impurity (i.e., N-2 or O-2) into saline aquifers would be an economical strategy. To assess the feasibility of coinjection, the partitioning and storage efficiency of impure CO2 in a deep saline aquifer were numerically investigated using a two-dimensional (2-D) radial anisotropic model, the aquifer condition referred to that of the Shenhua CCS site in the Ordos Basin. The results indicated that a high concentration of impurity moderately accelerated CO2 migration, and the formation dip angle dramatically promoted the migration as well as high temperature. Meanwhile, the partitioning of CO2 with impurities became intensive with the increase of impurity concentration. N-2 could be a suitable tracer to monitor leakage in saline aquifers, since the hysteresis of the breakthrough time between CO2 and N-2 was more evident. Moreover, N-2 lowered the storage efficiency of gaseous CO2, and the lowering was more obvious with the rising formation dip angle and temperature. The impact of N-2 on the storage efficiency of gaseous CO2 was obvious compared to O-2 under the same concentration. The investigation could be crucial for assessing the feasibility of coinjection and the long-term performance of the saline aquifer storage system
Influence of the introduction of small hydrophilic groups on the kinetic hydrate inhibition effect of poly(N-vinylcaprolactam)
No full textTraditional amide-based hydrate inhibitors, vital for preventing blockages, face limitations due to increasingly stringent environmental regulations. This study focuses on modifying poly(N-vinylcaprolactam) (PVCap) to improve its inhibition and biodegradation properties, by introducing -OH, -NH2, or -COOH groups into the molecular structure. The results revealed that the -OH group significantly improved both hydrate inhibition and biodegradability, while the -COOH and - NH2 groups had moderate and counter-effects, respectively. Compared to end hydroxyl modification, multiple -OH groups in the vinylcaprolactam/vinylalcohol copolymer weaken the inhibition effect, despite enhancing biodegradability. Optimal hydrophilicity was found to enhance PVCap's KHI performance, emphasizing the delicate balance needed to optimize stability and effectiveness. PXRD, Raman spectroscopy and interfacial tension tests were used to elucidate the impact of the modified PVCaps on hydrate structure and gas-liquid interfacial properties. The results further highlighted the significance of appropriate amphiphilicity in augmenting the KHI effect of the modified PVCaps
Influence of the introduction of small hydrophilic groups on the kinetic hydrate inhibition effect of poly(N-vinylcaprolactam)
No full textTraditional amide-based hydrate inhibitors, vital for preventing blockages, face limitations due to increasingly stringent environmental regulations. This study focuses on modifying poly(N-vinylcaprolactam) (PVCap) to improve its inhibition and biodegradation properties, by introducing -OH, -NH2, or -COOH groups into the molecular structure. The results revealed that the -OH group significantly improved both hydrate inhibition and biodegradability, while the -COOH and - NH2 groups had moderate and counter-effects, respectively. Compared to end hydroxyl modification, multiple -OH groups in the vinylcaprolactam/vinylalcohol copolymer weaken the inhibition effect, despite enhancing biodegradability. Optimal hydrophilicity was found to enhance PVCap's KHI performance, emphasizing the delicate balance needed to optimize stability and effectiveness. PXRD, Raman spectroscopy and interfacial tension tests were used to elucidate the impact of the modified PVCaps on hydrate structure and gas-liquid interfacial properties. The results further highlighted the significance of appropriate amphiphilicity in augmenting the KHI effect of the modified PVCaps
Effect of Cationic Polyacrylamide on Gas-Water Seepage in Quartz Sands before and after Methane Hydrate Formation
No full textExcessive water production impacted marine natural gas hydrate production. Cationic polyacrylamide (CPAM), one kind of chemical reagent, was used for the first time to selectively reduce water production while having less impact on gas production. After quartz sands with an absolute permeability of 100-1000 mD were treated with CPAM, the water phase permeability was reduced to 1/15, while the gas phase permeability almost had no change. Furthermore, CPAM was effective in controlling water flow in quartz sands with an absolute permeability range of 100-1000 mD. The water phase permeability initially decreased and then stabilized as the concentration of CPAM increased from 500 to 20,000 ppm. Additionally, the formation of methane hydrate in pretreated quartz sands with CPAM led to a greater reduction in quartz sands' permeability than the sum of the respective reduction for CPAM treatment and methane hydrate formation. In addition, compared to quartz sands treated only with CPAM, the dissociation of 5% methane hydrate significantly increased the permeability of CPAM-treated quartz sands, but the permeability was smaller than that before CPAM treatment
Anisotropic heat characteristics and analysis of molten salt thermocline storage system
No full textMolten salt thermocline storage system is a promising heat storage technology for solar energy utilization, but the system with anisotropic heat transfer packed-bed is seldom studied. In present article, molten salt thermocline storage system with anisotropic heat transfer packed-bed is first proposed and numerically analyzed to improve discharging efficiency. In anisotropic system, molten salt temperature distribution including thermocline is similar to that of isotropic system, and temperature difference between molten salt and solid fillers is mainly determined by average solid thermal conductivity, while thermocline thickness and discharging performance are affected by axial heat diffusion and fluid-solid heat transfer. As axial solid thermal conductivity increases, effective discharging time and efficiency first increase with fluid-solid heat transfer enhancement, and then decrease with axial heat diffusion and thermocline thickness increasing. In present system, effective discharging time and efficiency reach their maximum value of 2.96 h and 89.45 %, and effective discharging efficiency can be increased 5.22 % with optimal axial solid thermal conductivity of 10 W/(mK). As radial solid thermal conductivity increases, heat diffusion in radial direction accelerates and that in axial direction slightly decelerates with thermocline thickness decreasing, and fluid-solid heat transfer is also enhanced, so effective heat discharging efficiency can be increased 6.56 %. As a conclusion, axial solid thermal conductivity should be optimized to a low value to reduce thermocline thickness, while radial solid thermal conductivity should be improved to enhance fluid-solid heat transfer
Synergy of heterogeneous Co/Ni dual atoms enabling selective C-O bond scission of lignin coupling with in-situ N-functionalization
No full textSelective cleavage of Csp2-OCH3 bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass. Here, a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal-organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols (88.5%-99.9% yields), which had ca. 4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts. The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps, and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp2-OCH3 cleavage, as elaborated by theoretical calculations. Notably, the CoNiDA@NC catalyst was highly recyclable, and exhibited excellent demethoxylation performance (77.1% yield) in real lignin monomer mixtures. Via in-situ cascade conversion processes assisted by dual-atom catalysis, various high-value N-containing chemicals, including caprolactams and cyclohexylamines, could be produced from lignin. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved
Performance Comparison of High-Temperature Heat Pumps with Different Vapor Refrigerant Injection Techniques
No full textIn order to develop a highly efficient and stable high-temperature heat pump to realize high-efficient electrification in the industrial sector, performance of high-temperature heat pumps with a flash tank vapor injection and sub-cooler vapor injection are compared under different evaporation temperatures, condensation temperatures, compressor suction superheat degrees, subcooling degrees and compressor isentropic efficiencies. The results show that the COP, injection mass flow ratio and VHC of the FTVC are higher than those of the SVIC-0, SVIC-5, SVIC-10 and SVIC-20 under the same working conditions, while the discharge temperature of the FTVC is approximately equal to that of the SVIC-0 and lower than those of the SVIC-5, SVIC-10 and SVIC-20. When the evaporation temperature, the condensation temperature and injection pressure are 55 degrees C, 125 degrees C and 921.4 kPa, respectively, the system COP of the FTVC is 4.49, which is approximately 6.7%, 7.3%, 7.8% and 8.9% higher than those of the SVIC-0, SVIC-5, SVIC-10, and SVIC-20, respectively
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