Document Type : Research Article
Department of Chemical Engineering, Islamic Azad University, Tehran, Iran
Department of Chemical Engineering, University of Bradford, Bradford, BD7 1DP, United Kingdom.
Gas hydrates form at various facilities related to the natural gas and process equipment in oil and gas fields, refineries, petrochemical and facilities in the chemical industry, in the presence of both natural gas and water, at high pressure and low temperature. In the present study, the equilibrium conditions of gas hydrate mixture formation including methane and ethane and also pure ethane are investigated. The conditions for binary hydrate formation without the presence of inhibitors have been used and the empirical research available in the field has been used to evaluate the accuracy of the present modeling. Hydoff software was used for modeling and the hydrate formation pressure was calculated. In order to evaluate the accuracy of the modeling, the values related to the calculation error were calculated from the existing experimental research and the results showed that there are 11%, 14% and 0.08% errors with Deaton & Frost, McLeod & Campbell, Holder & Grigoriou research, respectively. Therefore, it can be concluded that the best case for modeling according to the experimental results is Holder & Grigoriou, and therefore a mathematical model is presented to estimate the formation conditions of the binary mixture of methane and ethane, which can be used with very high accuracy. Pure ethane was also tested with potassium chloride, sodium chloride and 5% methanol inhibitors and also without inhibitors and the results showed that the effect of adding methanol is greater than sodium chloride and potassium chloride, respectively, and ethane hydrate is formed at higher pressures.