Gas-expanded liquids.

If the potential for a boom in the global hydrogen economy is realized, there will be an increase in the need for accurate hydrogen thermodynamic property standards. Based on current and anticipated needs, new fundamental equations of state for parahydrogen, normal hydrogen, and orthohydrogen were developed to replace the existing property models. To accurately predict thermophysical properties near the critical region and in liquid states, the quantum law of corresponding states was applied to improve the normal hydrogen and orthohydrogen formulations in the absence of available experimental data. All three equations of state have the same maximum pressure of 2000MPa and upper temperature limit of 1000K. Uncertainty estimates in this paper can be considered to be estimates of a combined expanded uncertainty with a coverage factor of 2 for primary data sets. The uncertainty in density is 0.04% in the region between 250 and 450K and at pressures up to 300MPa. The uncertainties of vapor pressures and saturated liquid densities vary from 0.1% to 0.2%. Heat capacities are generally estimated to be accurate to within 1%, while speed-of-sound values are accurate to within 0.5% below 100MPa.

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Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen

An equation of state for the CH4-CO2-H2O system: II. Mixtures from 50 to 1000°C and 0 to 1000 bar

http://www.diva-portal.org/smash/get/diva2:459567/FULLTEXT03

PVTxy properties of CO2 mixtures relevant for CO2 capture, transport and storage: Review of available experimental data and theoretical models

In 2004, we started to develop a group contribution method aimed at estimating the temperature dependent binary interaction parameters (kij(T)) for the widely used Peng–Robinson equation of state (EOS). Because our model relies on the Peng–Robinson EOS as published by Peng and Robinson in 1978 and because the addition of a group contribution method to estimate the kij makes it predictive, this model was called PPR78 (predictive 1978, Peng Robinson EOS). In our previous papers eleven groups were defined: CH3, CH2, CH, C, CH4 (methane), C2H6 (ethane), CHaro, Caro, Cfused aromatic rings, CH2,cyclic and CHcyclic Ccyclic. It was thus possible to estimate the kij for any mixture containing alkanes, aromatics and naphthenes at any temperature. In this study, the PPR78 model is extended to systems containing carbon dioxide. To do so, the group CO2 was added. The results obtained in this study are in many cases accurate.

Predicting the phase equilibria of CO2+hydrocarbon systems with the PPR78 model (PR EOS and kij calculated through a group contribution method)

The P-V-T-X relations around the phase boundaries have been measured for the carbon dioxide-nitrogen and the carbon dioxide-methane systems. A visual glass capillary was used as the equilibrium cell. The principle of the experimental procedure is based on the dew and bubble point method. The pressure range covered was from 20 to 150 atm and the experimental temperatures were 15°C, 0°C and -20°C. From the data obtained, compressibility factor charts were constructed for the entire experimental range. The fugacities and partial molar volumes were also calculated. Finally it was found that there is a straight-line relationship between pressure and average density of coexisting liquid and vapor for the binary systems studied here. This relationship is similar to Cailletet-Mathias rule between temperature and average density for a pure substance.

The experimental determination of the p-v-t-x relations for the carbon dioxide-nitrogen and the carbon dioxide-methane systems

Vapor-liquid equilibria containing carbon dioxide: CO2-CO, CO2-Ar, CO2-CH4 and CO2-H2-CO were measured by static method at -50°C to 20°C and up to 200 atm. By using these data and the data available in literature, the extent of usefulness of the Benedict-Webb-Rubin equation (hereafter abbreviated as BWR equation) and the treatment of Leland et al. were studied. The BWR equation correctly predicted the vapor-liquid equilibria of inorganic mixtures except in the critical region, while the treatment of Leland et al. was insufficient.

Vapor-liquid equilibria for binary and ternary systems containing carbon dioxide

The vapor-liquid equilibrium relations of the hydrogen-methane, the hydrogen-ethylene, The hydrogen-ethane, the hydrogen-methane-ethylene and the hydrogen-ethylene-ethane systems were determined by a static method at several temperatures from -25°C to -170°C and at pressures up to 100 atm. From the data obtained, features of the phase equilibria of hydrogen-light hydrocarbon mixtures are discussed. The Benedict-Webb-Rubin equation was successfully applied to predict the vapor-liquid equilibria of the present systems above the normal boiling point of the heaviest hydrocarbon.

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Vapor-liquid equilibria of binary and ternary systems containing hydrogen and light hydrocarbons

The P-V-T-X relation for the carbon dioxide-argon system was measured at 15°C and up to 150 atm by using a glass capillary cell. From the data obtained, fugacities, partial molar volumes and compressibility factor charts were constructed. It was found again for the present system that there is a straight-line relationship between pressure and average density of coexisting liquid and vapor.

Yasuhiko Arai

Papers

The experimental determination of the p-v-t-x relations for the carbon dioxide-nitrogen and the carbon dioxide-methane systems

Vapor-liquid equilibria for binary and ternary systems containing carbon dioxide

Vapor-liquid equilibria of binary and ternary systems containing hydrogen and light hydrocarbons

The p-v-t-x relation for the carbon dioxide-argon system

The compressibility factors of hydrogen methane, hydrogen-ethane and hydrogen-propane gaseous mixtures