Thermodynamic modeling of gas hydrate phase equilibrium of carbon dioxide and its mixture using different equations of states

Abstract

In this work, the fugacity-based approach of the Klauda and Sandler model was used to predict the equilibrium conditions of gas hydrates formation for carbon dioxide and its mixtures with nitrogen, methane, ethane, and propane. In order to calculate the Langmuir constants and empty hydrate vapor pressure, the correlations presented by Munck et al., (1988) and Dharmawardhana et al., (1980) were used, respectively. Hence, six well-known equations of state (EOS) including PR, PRSV, SRK, PT, VPT and translated and consistent versions of the Peng-Robinson (tc-PR) had been used to calculate the thermodynamic properties. The thermodynamic modeling results were compared with numerous experimental data in the literature. These results showed that although all EOSs could successfully predict the equilibrium pressure of carbon dioxide, there is a deviation, less than 3.3 %, in all of them. In the case of mixture hydrates, such as CO2/CH4 and CO2/C2H6, the equilibrium pressures from the models had a good agreement with experimental data, except for PT EOS with a relatively high average absolute deviation in CO2/CH4 mixture hydrates. The predicted equilibrium pressure from the different EOSs showed excellent results for structure I, including CO2/C3H8 mixture hydrates. In addition, it has been concluded that this modeling can’t predict the equilibrium pressure structure I of CO2/N2 mixture hydrate at high pressures.