The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing ...The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing sediment deviates from that of pure bulk hydrate,reflecting the porous media effect in phase equilibrium.A generalized phase equilibrium equation was established for hydrate-bearing sediments,which indicates that both capillary and osmotic pressures cause the phase equilibrium curve to shift leftward on the temperature-pressure plane.In contrast to bulk hydrate,hydrate-bearing sediment always contains a certain amount of unhydrated water,which keeps phase equilibrium with the hydrate within the hydrate stability field.With changes in temperature and pressure,a portion of pore hydrate and unhydrated water may transform into each other,affecting the shear strength of hydrate-bearing sediment.A shear strength model is proposed to consider not only hydrate saturation but also the change in temperature and pressure of hydrate-bearing sediment.The model is validated by experimental data with various hydrate saturation,temperature and pressure conditions.The deformation induced by partial dissociation was studied through depressurization tests under constant effective stress.The reduction in gas pressure within the hydrate stability field indeed caused sediment deformation.The dissociation-induced deformation can be reasonably estimated as the difference in volume between hydrate-bearing and hydrate-free sediments from the compression curves.展开更多
1 Introduction A salt lake is a naturally occurring complex body of water and salt interaction.More than 700 salt lakes are widely distributed in the area of the Qinghai-Tibet Plateau.Most of the salt lakes are famous...1 Introduction A salt lake is a naturally occurring complex body of water and salt interaction.More than 700 salt lakes are widely distributed in the area of the Qinghai-Tibet Plateau.Most of the salt lakes are famous for their abundance of lithium,potassium,magnesium,and boron resources.It is展开更多
The present paper contains the effects of the ammonium ion, counter ion, solvent and anion being transferred on the solid-liquid phase transfer equilibrium constant of quaternary ammonium salts. The most striking diff...The present paper contains the effects of the ammonium ion, counter ion, solvent and anion being transferred on the solid-liquid phase transfer equilibrium constant of quaternary ammonium salts. The most striking difference between solid-liquid and liquid-liquid phase transfer equilibriums is that the length of alkyl chain shows a large effect on the latter but little on the former This means that the chain length affects only the hydrophobicity, rather than the lipophilicity.Keywords Quaternary ammonium salt, Phase transfer catalysis, Equilibrium constant, Hydrophobicity, Lipophilicity展开更多
KF or K2CO3 was added into the 1-butanol-water system and two phases were formed： water-rich phase （water phase） and 1-butanol-rich phase （1-butanol phase）. The liquid liquid equilibrium （LLE） data for 1-butano...KF or K2CO3 was added into the 1-butanol-water system and two phases were formed： water-rich phase （water phase） and 1-butanol-rich phase （1-butanol phase）. The liquid liquid equilibrium （LLE） data for 1-butanol-water-KF and 1-butanol-water-K2CO3 systems were measured at 25℃ and showed that 1-butanol phase contained negligible salt and water phase contained negligible 1-butanol when the concentrations of KF and K2CO3 in the water phase were equal to or higher than 27.11% and 31.68% , respectively. Thus water could be separated efficiently from 1-butanol-water by adding KF or K2CO3 into the system. A theoretical calculation of LLE data was calculated by using the Pitzer theory to get water activity in the water phase, and by the models, such as the Wilson, NRTL or the UNIQUAC for the 1-butanol phase. For 1-hutanol-water-KF system, the experimental data were found in good agreement with the calculated results by using Pitzer theory and Wilson equa tion, while for 1-butanol-water-K2CO3 system, the experimental data were found in good agreement with the calculated results by using Pitzer theory and UNIQUAC eauation.展开更多
Extraction of methane hydrate from subseafloor reservoir may potentially trigger seabed slides and induce subsidence.To address the problems,it is crucial to properly characterize the phase equilibrium condition of po...Extraction of methane hydrate from subseafloor reservoir may potentially trigger seabed slides and induce subsidence.To address the problems,it is crucial to properly characterize the phase equilibrium condition of pore hydrate and the shear strength of the soil.As one of the key constitutive components,the phase equilibrium condition enforces a constraint over pore gas pressure,temperature and unhydrated water content.Such a constraint,however,has been traditionally ignored in analyzing the mechanical behavior of hydrate-bearing soil.In this paper,a series of stepwise hydrate dissociation tests was performed,and the phase equilibrium condition of pore hydrate was determined,providing an effective way to evaluate the unhydrated water content during hydrate dissociation.Meanwhile,a series of direct shear tests was also conducted to explore the shear strength characteristics of the soil.It is shown that the shear strength of the hydrate-bearing soil can be significantly influenced by pore gas pressure,unhydrated water content,hydrate saturation and several other factors.In particular,the measured shear strength depends upon the initial water content of the sample,pointing to a potential problem that the shear strength could be wrongly determined if not properly interpreted.A shear strength criterion,which enforces the equilibrium condition of pore hydrate,is developed for hydrate-bearing soil,establishing a link between the equilibrium condition and the shear strength.The proposed equation describes well the shear strength characteristics of hydrate-bearing soils,remarkably unifying the effects of pore pressure,temperature,water content and hydrate saturation.展开更多
According to the compositions of the underground gasfield brines in the west of Sichuan Basin,the phase equilibria in the ternary systems KBr-K2B4O7-H2O and KCl-K2B4O7-H2O at 373 K were studied using the isothermal di...According to the compositions of the underground gasfield brines in the west of Sichuan Basin,the phase equilibria in the ternary systems KBr-K2B4O7-H2O and KCl-K2B4O7-H2O at 373 K were studied using the isothermal dissolution equilibrium method.The solubilities of salts and the densities of saturated solutions in these ternary systems were determined.Using the experimental data,phase diagrams and density-composition diagrams were constructed.The two phase diagrams were simple co-saturation type,each having an invariant point,two univariant curves and two crystallization regions.The equilibrium solid phases in the ternary system KBr-K2B4O7-H2O are potassium bromide （KBr） and potassium tetraborate tetrahydrate （K2B4O7·4H2O）,and those in the ternary system KCl-K2B4O7-H2O are potassium chloride （KCl） and potassium tetraborate tetrahydrate （K2B4O7·4H2O）.Comparisons of the phase diagrams of the two systems at different temperatures show that there is no change in the crystallization phases,but there are changes in the size of the crystallization regions.As temperature increases,the solubility of K2B4O7·4H2O increases rapidly,so the crystallization field of K2B4O7·4H2O becomes smaller.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42171135 and 12262009)the“CUG Scholar”Scientific Research Funds at China University of Geosciences(Wuhan)(Project No.2022098).
文摘The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing sediment deviates from that of pure bulk hydrate,reflecting the porous media effect in phase equilibrium.A generalized phase equilibrium equation was established for hydrate-bearing sediments,which indicates that both capillary and osmotic pressures cause the phase equilibrium curve to shift leftward on the temperature-pressure plane.In contrast to bulk hydrate,hydrate-bearing sediment always contains a certain amount of unhydrated water,which keeps phase equilibrium with the hydrate within the hydrate stability field.With changes in temperature and pressure,a portion of pore hydrate and unhydrated water may transform into each other,affecting the shear strength of hydrate-bearing sediment.A shear strength model is proposed to consider not only hydrate saturation but also the change in temperature and pressure of hydrate-bearing sediment.The model is validated by experimental data with various hydrate saturation,temperature and pressure conditions.The deformation induced by partial dissociation was studied through depressurization tests under constant effective stress.The reduction in gas pressure within the hydrate stability field indeed caused sediment deformation.The dissociation-induced deformation can be reasonably estimated as the difference in volume between hydrate-bearing and hydrate-free sediments from the compression curves.
基金Financial supports from the NSFCs (21106103, 21276194 and 21306136)the Specialized Research Funds for the Doctoral Program of Chinese Higher Education (20101208110003 and 20111208120003)+1 种基金the Natural Science Foundation of Tianjin (12JCQNJC03400)the Senior Professor Program for TUST (20100405)
文摘1 Introduction A salt lake is a naturally occurring complex body of water and salt interaction.More than 700 salt lakes are widely distributed in the area of the Qinghai-Tibet Plateau.Most of the salt lakes are famous for their abundance of lithium,potassium,magnesium,and boron resources.It is
文摘The present paper contains the effects of the ammonium ion, counter ion, solvent and anion being transferred on the solid-liquid phase transfer equilibrium constant of quaternary ammonium salts. The most striking difference between solid-liquid and liquid-liquid phase transfer equilibriums is that the length of alkyl chain shows a large effect on the latter but little on the former This means that the chain length affects only the hydrophobicity, rather than the lipophilicity.Keywords Quaternary ammonium salt, Phase transfer catalysis, Equilibrium constant, Hydrophobicity, Lipophilicity
文摘KF or K2CO3 was added into the 1-butanol-water system and two phases were formed： water-rich phase （water phase） and 1-butanol-rich phase （1-butanol phase）. The liquid liquid equilibrium （LLE） data for 1-butanol-water-KF and 1-butanol-water-K2CO3 systems were measured at 25℃ and showed that 1-butanol phase contained negligible salt and water phase contained negligible 1-butanol when the concentrations of KF and K2CO3 in the water phase were equal to or higher than 27.11% and 31.68% , respectively. Thus water could be separated efficiently from 1-butanol-water by adding KF or K2CO3 into the system. A theoretical calculation of LLE data was calculated by using the Pitzer theory to get water activity in the water phase, and by the models, such as the Wilson, NRTL or the UNIQUAC for the 1-butanol phase. For 1-hutanol-water-KF system, the experimental data were found in good agreement with the calculated results by using Pitzer theory and Wilson equa tion, while for 1-butanol-water-K2CO3 system, the experimental data were found in good agreement with the calculated results by using Pitzer theory and UNIQUAC eauation.
基金This research was funded by the National Science Foundation of China(NSFC)(Grant Nos.51939011 and 42171135)Youth Innovation Promotion Association,Chinese Academy of Sciences(CAS)(Grant No.2020326),which are gratefully acknowledged.
文摘Extraction of methane hydrate from subseafloor reservoir may potentially trigger seabed slides and induce subsidence.To address the problems,it is crucial to properly characterize the phase equilibrium condition of pore hydrate and the shear strength of the soil.As one of the key constitutive components,the phase equilibrium condition enforces a constraint over pore gas pressure,temperature and unhydrated water content.Such a constraint,however,has been traditionally ignored in analyzing the mechanical behavior of hydrate-bearing soil.In this paper,a series of stepwise hydrate dissociation tests was performed,and the phase equilibrium condition of pore hydrate was determined,providing an effective way to evaluate the unhydrated water content during hydrate dissociation.Meanwhile,a series of direct shear tests was also conducted to explore the shear strength characteristics of the soil.It is shown that the shear strength of the hydrate-bearing soil can be significantly influenced by pore gas pressure,unhydrated water content,hydrate saturation and several other factors.In particular,the measured shear strength depends upon the initial water content of the sample,pointing to a potential problem that the shear strength could be wrongly determined if not properly interpreted.A shear strength criterion,which enforces the equilibrium condition of pore hydrate,is developed for hydrate-bearing soil,establishing a link between the equilibrium condition and the shear strength.The proposed equation describes well the shear strength characteristics of hydrate-bearing soils,remarkably unifying the effects of pore pressure,temperature,water content and hydrate saturation.
文摘针对甲基丙烯酸(MAA)与水(H_(2)O)形成共沸混合物、MAA水溶液分离难的问题,开展了MAA水溶液提纯过程萃取剂筛选、MAA H_(2)O萃取剂三元液液相平衡数据测定与关联等研究。通过对甲苯、正己烷、环己烷、邻苯二甲酸二丁酯(DBP)4种萃取剂的萃取效率进行考察,确定DBP为综合性能最优的萃取剂。测定了常压条件下20、30、40℃时H_(2)O MAA DBP三元体系的液液相平衡数据,实验结果通过了Hand方程和Othmer Tobias方程对相平衡数据的一致性验证,线性相关性系数R^(2)值超0.99。使用UNIQUAC模型来拟合实验数据得到三组分二元交互作用参数,模型预测值与实验值的均方根偏差小于0.07,表明实验数据及拟合参数均有较高的准确性,为DBP应用于工业MAA水溶液提纯过程开发提供基础。
基金supported by the Open Fund (PLC201204) of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology)the National Natural Science Foundation of China (Grant No. 41373062,40973047, 41172118)+1 种基金the Specialized Research Fund (20125122110015) for the Doctoral Program of Higher Education of Chinathe youth science and technology innovation team of Sichuan Province, China(2013TD0005)
文摘According to the compositions of the underground gasfield brines in the west of Sichuan Basin,the phase equilibria in the ternary systems KBr-K2B4O7-H2O and KCl-K2B4O7-H2O at 373 K were studied using the isothermal dissolution equilibrium method.The solubilities of salts and the densities of saturated solutions in these ternary systems were determined.Using the experimental data,phase diagrams and density-composition diagrams were constructed.The two phase diagrams were simple co-saturation type,each having an invariant point,two univariant curves and two crystallization regions.The equilibrium solid phases in the ternary system KBr-K2B4O7-H2O are potassium bromide （KBr） and potassium tetraborate tetrahydrate （K2B4O7·4H2O）,and those in the ternary system KCl-K2B4O7-H2O are potassium chloride （KCl） and potassium tetraborate tetrahydrate （K2B4O7·4H2O）.Comparisons of the phase diagrams of the two systems at different temperatures show that there is no change in the crystallization phases,but there are changes in the size of the crystallization regions.As temperature increases,the solubility of K2B4O7·4H2O increases rapidly,so the crystallization field of K2B4O7·4H2O becomes smaller.
