Papers by Keyword: Phase Equilibrium

Abstract: The Mg-rich corner of the equilibrium phase diagram of the Mg-Zn-Gd system has been calculated in detail using the phase diagram calculation software PANDAT and the thermodynamic database for Mg alloys. The calculated phase diagram includes the liquidus projection, isothermal sections and vertical sections. It is found that an increase of Zn content in the Mg-Gd alloy reduces the phase field of α-Mg + GdMg5. Based on the calculated phase diagrams, two alloys, Mg-5.5Zn-2Gd-0.5Zr and Mg-1.6Gd-5.5Zn-0.5Zr (wt.%), denoted as ZGK620 and ZGK616, were developed and their solidification and precipitation processes were analyzed in detail. The optimized thermal mechanical processing and heat-treatment processes were defined by referring to the calculated phase diagrams of the Mg-Zn-Gd system.

Abstract: The equilibria phase of the ternary systems NaCl-CsCl-H₂O was studied at 50°C by the isothermal evaporation method. The equilibrium phase diagrams were plotted in line with the experimental data. It suggest that the phase diagram of NaCl-CsCl-H₂O is the simple eutectic type where one invariant point is found to have the compositions of 12.3% NaCl, 54.1% CsCl and 33.6% H₂O by mass, respectively. The study provide fundamental thermodynamic data of brine system that contains sodium and cesium, and has practical significance for the brine’s comprehensive utilization.

Abstract: Capturing carbon dioxide (CO2) by forming hydrate is an attractive technology for reducing the greenhouse effect. The most primary challenges are high energy consumption, low hydrate formation rate, and separation efficiency. In order to solve the problem of slow formation rate of gas hydrate, the effects of sodium dodecyl benzene sulfonate (SDBS), hexadecyl trimethyl ammonium bromide (CTAB) and polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer (P123) on the formation of carbon dioxide hydrate have been investigated.The results show that CTAB, SDBS and P123 can reduce phase equilibrium point of CO2 hydrate. The lower pressure of hydration reaction system ,the larger induction time of CO2 hydrate reduction.Maximum promotion effect of SDBS was observed at 700 mg / kg which was comparable with that of CTAB at 300 mg / kg and P123 at 500 mg / kg. The study has a certain significance to improve the rate of hydrate formation.

Abstract: In allusion to some methods on desalination of brackish water such as distillation, electrodialysis method and reverse osmosis, this paper introduced the mechanism, advantages and disadvantages of these methods. It is convinced that these methods have higher energy consumption. Temperature is much lower annually in alpine region of China, it provides a good condition for hydrate formation. It also provides the possibility for the desalinating process of brackish water using hydrate methods in alpine region. This paper proposed a new method of desalinating brackish water. Based on the model of van der Waals-Platteeuw, we calculated the phase equilibrium conditions of methane, ethane and propane hydrate in NaCl solution combined parameter equation which was used to calculate the Langmuir constant presented by DU Ya and GUO Tian-min and Pitzer equation used to water activity in the system of electrolyte solution. The result shows that it is possible to desalinate brackish water using environment cold quantity. It also shows that propane is more suitable for brackish water desalination among methane, ethane and propane. It is very significantly important to seek energy-saving and environment-friendly methods for the process of desalinating brackish water with energy shortage increasingly intensifying and with awareness of human being enthancing on energy conservation and emission reduction.

Abstract: Biodiesel was prepared by methyl esterification and effects of different reaction conditions on the yield of fatty acid methyl esters (FAMEs) were investigated. The result of the orthogonal experiment analysis shows that the order of influential factors is ranked as reaction temperature > methanol-to-soybean-oil (M/O) ratio > reaction time. The maximum yield of 94.8 % has been achieved by reacting supercritical methanol and soybean oil in M/O ratio 4:2 (v/v) at 573 K for 45 min. Moreover, the higher M/O ratio, the higher yield of FAMEs will be obtained. At the temperature ranging from 533 k to 573 k, the yield rises significantly; however, since soybean oil decomposes over 573 K, the yield decreases oppositely. Time longer than 45 min has less effect on the final yield. In addition, the phase equilibrium data of supercritical methanol + C12 methyl esters and supercritical methanol + C18 methyl esters were separately correlated using the Peng-Robinson (PR) equation of state (EOS) with the Adachi-Sugie (AS) mixing rule.

Abstract: In order to develop a new technology for separating the bloedite by the method of gas hydrate formation, the phase equilibrium of the H2O-Na2SO4-MgSO4-C3H8 system and its subsystems was studied at 0°C and pressure.The equilibrium pressure and the composition of solid and liquid above system were investigated.It was found that equilibrium pressure of gas hydrate formation was increasing with the increase of the Na2SO4( or MgSO4) concentration. The addition of anionic surfactant SDS helped to lower the equilibrium pressure of gas hydrate formation. The mother liquor amount entrained in the gas hydrate after liquid separation by sinking was very high when surfactants was not added. But the equilibrium pressure of gas hydrate formation and the mother liquor amount entrained in gas hydrate were decreased when surfactant was added to the system.

Abstract: It is well known that the exploitation of brine resources of salt lakes is based on the relevant phase equilibrium and phase diagrams. In this paper, the progresses on the stable and metastable equilibria, thermodynamic properties and predictive solubilities of the brine system containing lithium and borate ions at present were summarized. The problems existed and the new trends in the future were also carried out.

Abstract: In this paper, phase equilibrium of MgCl2-LiCl-Na2SiO3-H2O system at 180°C was researched. The solid phases were characterized by X-ray diffraction (XRD). Lithium silicate, hectorite, karpinskite and magnesium hydroxide were observed as solid phases. According to the analysis of XRD, the phase diagram was obtained. The phase diagram could be used as the theoretical principle for synthesis of hectorite and comprehensive utilization of concentrated natural brine.

Abstract: An experiment on effects of composite promoting agents composed of surfactants and liquid hydrocarbons on hydrate formation was conducted and hydrate formation temperature, pressure, induction time and rate with different composite promoting agent portfolios were measured. Surfactants used were sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate(SDBS) and 2-octyl sodium dodecyl sulfate(GC20S), and liquid hydrocarbon additives utilized were ring silane e (CP) and methyl cyclohexane (MCH). It appeared that all these combinations of composite promoting agents could promote hydrate formation. Type II and H hydrate formation conditions with composite promoting agents CP+GC20S and MCH+GC20S respectively were the mildest and the induction time was the shortest.

Abstract: The CO₂ EOR and Storage Project in Jilin oilfield is the first large CCS demonstration project in China for CO₂ geological storage into depleting oil reservoirs. It aims at enhancing the understanding of CO₂ EOR mechanisms, movement of CO₂ in the reservoir and relevant physical-chemical reactions involved in the storage process, meanwhile gaining practical experience of monitoring and verification of CO₂ storage technology in tight oil reservoirs. To have a better understanding of the naturally occurring and phase transformation between CO₂ and reservoir fluid and provide accurate data for designing an oil development plan, we must know the interactions between CO₂ and reservoir fluids. Hence, in the first part of this paper the CO₂ and reservoir fluid phase equilibrium is measured with laboratory experiment, then the collected data is used to calculate the theory and practical CO₂ Sequestration capacities.