Study on Hydrate Phase Equilibrium Diagram of Methane Containing System Based on Thermodynamic Model

Natural gas hydrate is a potential energy source in the future, which widely occurs in nature and industrial activities, and its formation and decomposition are identified by phase equilibrium. The calculation of multicomponent gas phase equilibrium is more complex than that of single component gas, which depends on the accurate model characterized by enthalpy and free energy. Based on the Kvamme-Tanaka statistical thermodynamic model, theoretical and experimental methods were used to predict and verify the phase equilibrium of pure methane hydrate and carbon dioxide hydrate in the temperature range of 273.17–289.05 K. The phase equilibrium curves of methane-containing gases such as CH4+CO2,CH4+C2H6,CH4+H2S and CH4+CO2+H2S under different mole fractions were drawn and analyzed, and the decomposition or formation enthalpy and free energy of hydrate were calculated. The results show that, the phase equilibrium curves of the methane containing systems is mainly related to the guest molecule type and the composition of gas. The evolution law of phase equilibrium pressure of different gases varies with composition and temperature, and the phase splitting of CO2 at the quadruple point affects the phase equilibrium conditions. Due to the consideration of the interaction between the motion of guest molecules and the vibration of crystal lattice, the model exhibits a good performance, which is quantified in terms of mean square error (MSE) with respect to the experimental data. The magnitudes of MSE percent are respectively 1.2, 4.8, 15.12 and 9.20 MPa2 for CH4+CO2, CH4+C2H6, CH4+H2S and CH4+CO2+H2S systems, and the values are as low as 3.57 and 1.32 MPa2 for pure methane and carbon dioxide, respectively. This study provides engineers and researchers who want to consult the diagrams at any time with some new and accurate experimental data, calculated results and phase equilibrium curves. The research results are of great significance to the development and utilization of gas hydrate and the flow safety prediction of gas gathering and transportation.

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Effect of Common Impurities on the Phase Behavior of Carbon-Dioxide-Rich Systems: Minimizing the Risk of Hydrate Formation and Two-Phase Flow

SPE Journal ◽

10.2118/123778-pa ◽

2011 ◽

Vol 16 (04) ◽

pp. 921-930 ◽

Cited By ~ 31

Author(s):

Antonin Chapoy ◽

Rod Burgass ◽

Bahman Tohidi ◽

J. Michael Austell ◽

Charles Eickhoff

Keyword(s):

Experimental Data ◽

Carbon Dioxide ◽

Phase Behavior ◽

Water Content ◽

Thermodynamic Model ◽

Two Phase Flow ◽

Hydrate Formation ◽

Experimental Methodology ◽

Phase Flow ◽

Two Phase

Summary Carbon dioxide (CO2) produced by carbon-capture processes is generally not pure and can contain impurities such as N2, H2, CO, H2 S, and water. The presence of these impurities could lead to challenging flow-assurance issues. The presence of water may result in ice or gas-hydrate formation and cause blockage. Reducing the water content is commonly required to reduce the potential for corrosion, but, for an offshore pipeline system, it is also used as a means of preventing gas-hydrate problems; however, there is little information on the dehydration requirements. Furthermore, the gaseous CO2-rich stream is generally compressed to be transported as liquid or dense-phase in order to avoid two-phase flow and increase in the density of the system. The presence of impurities will also change the system's bubblepoint pressure, hence affecting the compression requirement. The aim of this study is to evaluate the risk of hydrate formation in a CO2-rich stream and to study the phase behavior of CO2 in the presence of common impurities. An experimental methodology was developed for measuring water content in a CO2-rich phase in equilibrium with hydrates. The water content in equilibrium with hydrates at simulated pipeline conditions (e.g., 4°C and up to 190 bar) as well as after simulated choke conditions (e.g., at -2°C and approximately 50 bar) was measured for pure CO2 and a mixture of 2 mol% H2 and 98 mol% CO2. Bubblepoint measurements were also taken for this binary mixture for temperatures ranging from -20 to 25°C. A thermodynamic approach was employed to model the phase equilibria. The experimental data available in the literature on gas solubility in water in binary systems were used in tuning the binary interaction parameters (BIPs). The thermodynamic model was used to predict the phase behavior and the hydrate-dissociation conditions of various CO2-rich streams in the presence of free water and various levels of dehydration (250 and 500 ppm). The results are in good agreement with the available experimental data. The developed experimental methodology and thermodynamic model could provide the necessary data in determining the required dehydration level for CO2-rich systems, as well as minimum pipeline pressure required to avoid two-phase flow, hydrates, and water condensation.

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Platelet Phagocytosis As A Model For Platelet Adhesion

10.1055/s-0038-1653285 ◽

1981 ◽

Cited By ~ 1

Author(s):

D R Absolom ◽

W Zingg ◽

A W Neumann ◽

C J van Oss

Keyword(s):

Experimental Data ◽

Free Energy ◽

Thermodynamic Model ◽

Platelet Adhesion ◽

Helmholtz Free Energy ◽

Hydrophilic Polymers ◽

Polymer Substrates ◽

Physical Conditions ◽

Insight Into

It has been suggested that platelet phagocytosis might be a useful model to provide insight into platelet adhesion to polymer substrates commonly employed in biocompatibility studies. To test this supposition the present study of platelet engulfment of four strains of bacteria (opsonized as well as non-opsonized) under well defined in vitro physical conditions was undertaken. In physiologic conditions, platelet adhesion is maximum on the more hydrophilic polymers and minimum on the more hydrophobic surfaces; bacterial engulfment under the same conditions follows an identical pattern in that the more hydrophilic bacteria are more readily engulfed. The experimental data further suggest that, unlike phagocytosis by neutrophils platelet interaction with bacteria is non-specific in that it does not appear to be antibody receptor modulated. Opsonization of the bacteria does however play an important role in that it serves to increase the hydrophobicity of the bacteria thereby influencing the degree of bacterial engulfment. A striking correlation between the extent of bacterial engulfment and the Helmholtz Free Energy of Engulfment exists. Platelet adhesion to polymer substrates and platelet engulfment of bacteria appear to follow the same thermodynamic model.

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Experimental Data Assessment Test for Composition of Vapor Phase in Equilibrium with Gas Hydrate and Liquid Water for Carbon Dioxide + Methane or Nitrogen + Water System

Industrial & Engineering Chemistry Research ◽

10.1021/ie202465r ◽

2012 ◽

Vol 51 (9) ◽

pp. 3819-3825 ◽

Cited By ~ 13

Author(s):

Ali Eslamimanesh ◽

Saeedeh Babaee ◽

Amir H. Mohammadi ◽

Jafar Javanmardi ◽

Dominique Richon

Keyword(s):

Experimental Data ◽

Carbon Dioxide ◽

Vapor Phase ◽

Liquid Water ◽

Gas Hydrate ◽

Water System ◽

Data Assessment

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Phase Equilibrium Study on the Quaternary System H2O-Na2SO4-MgSO4-C3H8 at 0°C and Pressure

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.550-553.2690 ◽

2012 ◽

Vol 550-553 ◽

pp. 2690-2694 ◽

Cited By ~ 2

Author(s):

Panpan Chen ◽

Guoen Li ◽

Hongfei Guo ◽

Ji Lin Cao

Keyword(s):

Phase Equilibrium ◽

Gas Hydrate ◽

Mother Liquor ◽

New Technology ◽

Hydrate Formation ◽

Equilibrium Pressure ◽

Equilibrium Study ◽

Phase Equilibrium Study ◽

Gas Hydrate Formation ◽

Very High

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.

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Thermodynamic Interpretation of Carbonation Process of Portland Cement Hydration Products

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.753-755.543 ◽

2013 ◽

Vol 753-755 ◽

pp. 543-557

Author(s):

Yan Jun Liu ◽

Bo Tian Chen ◽

Yong Chao Zheng

Keyword(s):

Carbon Dioxide ◽

Free Energy ◽

Gibbs Free Energy ◽

Cement Paste ◽

Cement Hydration ◽

Hardened Cement ◽

Hydration Products ◽

Hardened Cement Paste ◽

Equilibrium Pressure ◽

Carbonation Process

Cement hydration products carbonation is not only blamed for the carbonation-induced hardened cement paste or concrete cracking, also attributed to the pore water PH-value decrease, which causes the reinforcement corrosion under the existence of water and oxygen due to removal of oxide film passivating rebar surface, in hardened cement paste and concrete. Based on chemical thermodynamics, this paper presents the susceptibility of different cement hydration products to carbonation through calculating their Standard Gibbs Free Energy respectively, Gibbs free energy under temperature variation and the minimum equilibrium pressure of carbon dioxide triggering the carbonation process. The calculated results show that, under standard state (25°C, 100kpa), the minimum equilibrium pressure of carbon dioxide triggering carbonation process is significantly variable for different types of cement hydration products. For example, mono-sulfate sulfoferrite hydrates (3CaOFe2O3CaSO412H2O) is the most susceptible to carbonation, followed by mono-sulfate aluminate hydrates (3CaOAl2O3CaSO412H2O), while multi-sulfate sulfoaluminate hydrates (3CaOAl2O33CaSO432H2O) is the least vulnerable to carbonation, followed by silicate hydrates (5CaO6SiO25.5H2O). The findings in this paper are significant in understanding thermodynamic mechanism of cement hydrates carbonation and seeking the solution to prevent cement hydrates from carbonation-induced deterioration.

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Gas hydrate phase equilibrium in the system methane–carbon dioxide–neohexane and water

Fluid Phase Equilibria ◽

10.1016/s0378-3812(99)00084-9 ◽

1999 ◽

Vol 158-160 ◽

pp. 795-800 ◽

Cited By ~ 51

Author(s):

Phillip Servio ◽

Fritz Lagers ◽

Cor Peters ◽

Peter Englezos

Keyword(s):

Carbon Dioxide ◽

Phase Equilibrium ◽

Gas Hydrate ◽

Hydrate Phase ◽

Methane Carbon

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Experimental and Theoretical Studies on the Fluid Properties Required for Simulation of Thermal Processes

Society of Petroleum Engineers Journal ◽

10.2118/8393-pa ◽

1981 ◽

Vol 21 (05) ◽

pp. 535-550 ◽

Cited By ~ 8

Author(s):

S.T. Lee ◽

R.H. Jacoby ◽

W.H. Chen ◽

W.E. Culham

Keyword(s):

Experimental Data ◽

Carbon Dioxide ◽

Phase Equilibrium ◽

Equation Of State ◽

Phase Equilibria ◽

Crude Oil ◽

Thermal Recovery ◽

Phase Equilibrium Data ◽

Equilibrium Data ◽

Robinson Equation

Abstract Experimental phase equilibrium data are presented for three reservoir oils at conditions approximating those encountered in in-situ thermal recovery processes. The fluid systems involved consist of three major groups of components: flue gas, water, and crude oil. Data were measured at temperatures from 204.4 to 371.1°C (400 to 700°F) and pressures from 6996.0 to 20785.6 kPa (1,000 to 3,000 psia). Experimental phase equilibrium data were used to develop a correlation of binary interaction coefficients of crude-oil fractions required for the Peng-Robinson equation of state. Phase equilibrium data predicted using the Peng-Robinson equation of state, using our interaction coefficients, are compared with experimental data. Generally, the Peng-Robinson equation of state predictions were in close agreement with the experimental data. Effect of feed gas/oil ratio and water/oil ratio on the equilibrium coefficients was examined through the Peng-Robinson equation of state. A study on the feasibility of representing the crude oil by only two fractions was made also. This study includes a procedure for lumping the crude-oil fractions and examples showing the importance of mixing rules in determining the pseudo critical properties of lumped fractions. Introduction The steady growth of commercial thermal recovery processes1 has created a need for basic data on phase equilibria that involve water and hydrocarbons ranging from methane to high boiling-point fractions. The in-situ thermal recovery processes often are operated at pressures above 6800 kPa (1,000 psia) and temperatures above 200°C (400°F). Experimental data and theoretical correlations on phase equilibria approximating these systems are virtually nonexistent. Early work by White and Brown2 dealt with high boiling-point hydrocarbon phase equilibria. However, the highest pressure studied was 6894.8 kPa (1,000 psia) and the lightest component was pentane. Poettmann and Mayland,3 on the basis of an empirical correlation,4 constructed charts of equilibrium coefficients, or K values, as functions of pressure and temperature for various boiling-point fractions. But the maximum pressure studied was 6894.8 kPa (1,000 psia). Later, Hoffmann et al.5 studied phase behavior of a gas-condensate system with the highest pressure reaching 20 684.3 kPa (3,000 psia) but the highest temperature investigated was only 94.2°C (201°F). In 1963, Grayson and Streed6 reported experimental vapor/liquid equilibrium data for high-temperature and high-pressure hydrocarbon systems. They also extended the Chao-Seader correlation to cover the higher temperature ranges. However, the. major light component in Grayson and Streed's system was hydrogen. Recently, because of the increasing activity in carbon dioxide flooding processes, the phase equilibria of systems involving carbon dioxide and crude oil has received attention. Simon et al.7 studied phase behavior and other properties of carbon-dioxide/reservoir-oil systems. Shelton and Yarborough8 examined phase behavior in porous media during carbon dioxide or rich-gas flooding. No extensive data on equilibrium coefficients were reported in those papers, and the temperature ranges (out of physical reality) were below 93.5°C (200°F). None of these papers surveyed included water as a component.

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