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Phase equilibria and solubility measurements of gases in water in the hydrate formation region

Authors
Publisher
McGill University
Publication Date
Keywords
  • Engineering - Chemical

Abstract

Gas hydrates are a topic of intense investigation primarily due to the vast amount of methane trapped in the form of gas hydrate on Earth and to the possibility of reducing greenhouse gas emissions via the sequestration of carbon dioxide in the form of gas hydrate. In the present study, phase equilibrium relationships of pressure, temperature, and composition in the liquid, vapour, and hydrate phases for the pure propane-water and CO2-CH4 mixed hydrate-water systems have been investigated. In the first part of the study, the concentration of propane dissolved in water in the presence of propane gas hydrates has been measured at temperatures from 274 K to 277 K and pressures ranging from 150 kPa to 350 kPa. Solubility measurements in the absence of hydrate were found to be in agreement with literature values, which predict an increase in solubility as temperature is decreased. In the hydrate formation region, the solubility of propane decreased with decreasing temperature. Therefore, hydrate formation reverses the gas-liquid solubility trend. Results also show that pressure does not have a strong influence on solubility in the presence of gas hydrate. In the second part of the study, phase equilibrium relationships for a 50/50 CH4/CO2 mixed hydrate-water system have been investigated at temperatures between 274 K and 282 K and at pressures of 2000 kPa and 2500 kPa. In the absence of hydrate, solubility of each gas in the aqueous phase decreased with increasing temperature. In the hydrate formation region, solubility of both CH4 and CO2 in water was found to decrease with decreasing temperature. Therefore, as previously concluded with single gas systems, hydrate formation reversed the gas-liquid solubility trend for each gaseous component in the mixed hydrate system. Results also showed that pressure did not have a strong influence on the solubility of each component in the presence of mixed gas hydrate. Furthermore, by mole balance, water-free mixed hydrate compo

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