Measurement And Calculation On Methane Solubility At Normal And High Pressures

With the improvement of environment consciousness and development of vehicles, relatively clean and economically natural gas vehicles become the emphasis of research. The very urgent problem of natural gas vehicle is how to store natural gas economically and efficiently. Dissolving natural gas in some solvents maybe one effective way for putting natural gas vehicle in wide use. Some fundamental research was done to select the ideal solvents for natural gas in the paper.A set of apparatus of determining gas solubilities in liquids at normal temperature and pressure was designed and established. The reliability of it was confirmed with literature data. The solubilities of methane in ethanol-n-hexane and ethanol-n-heptane under normal pressures were determined, the data were calculated by PR and PRSV EOS. At the same time the Henry's coefficients of methane in the binary solvents were calculated.In the paper, one set of experiment equipment for measuring gas solubility under high pressures was set up. It was proved reliable and accurate. In order to develop the use of ethanol-gasoline and methanol-gasoline blend fuels, ethanol and methanol, the two kinds of polar compounds mixing with n-hexane, n-heptane, benzene, toluene and some other hydrocarbon compounds separately were selected as solvents. The solubilities of methane in the different kinds of mixed solvents at high pressures were measured systematically. It was shown that it is feasible to dissolve NG in solvents. And by this method the energy storage density can be increased and the storage pressure can be decreased. It can provide basis and abundant fundamental data for the study of natural gas vehicle fuels, the develop of solution theory and the calculation of GLE. Five different equations of state coupled with mixing rules were adopted to calculate the ternary GLE data under high pressures by correlation, interpolation and extrapolation. And the modified method based on activity coefficient and associated theory were used to calculate the experimental data. At the same time, the applicability of every method to the GLE calculation for polar systems was discussed.In addition, the solubilities of methane under high pressures in gasoline and cyclehexane-n-heptane were determinated and the experimental data were calculated by the method based on equation of state. It was indicated that the ternary GLE data can be well estimated by the method using binary GLE data. The UNIFAC group contribution method was used to correlate and estimate the solubility of methane in polar solvents. New groups were defined, and the interaction-energy parameters of these groups with methane were regressed with the experimental data in the paper and other related data in literatures. It shown that the UNIFAC model coupled with the interaction-energy parameters can be used to estimate the solubility of methane in the related solvent accurately. PR EOS and A-K model were both used to calculate the molar volumes of liquid phase under high pressures for experimental systems. Besides, the A-K model was modified by two methods in order to estimate data of the systems containing alcohols more accurately. So the method was established successfully by which the quantity of fuel can be calculated using the molar volumes of liquid phase under high pressures.In a word, the methane solubilities in different mixed solvents under normal and high pressures were determinated. It provided the necessary data for practical application. Some calculation methods were put forword, it can be used to design the natural gas vehicle fuels containing solvents. At the same time, the theory of phase equilibria and the calculation methods were advanced.