Effect of Temperature Functions a (T) on Prediction of CH4 and N2 Gas Hydrate Formation Conditions

In this research, by using Van der Waals–Plauteeuw model for solid hydrate phase and equations of state with mixing rules (j −j model) for calculation of fugacity of components in gas and liquid phases, three phase equilibrium conditions (VL H) W have been predicted in two hydrate mixtures contain binary systems (CH4-H2O) and (N2-H2O). The pressure of hydrate formation has been calculated with four EOSs, VPT, PR, SRK and SW by using Danesh mixing rule. Also three temperature functions a (T) in PR equation of state have been studied that contain Soave, Tribble – Bishnoi (TB) and Nasrifar-Moshfeghiyan (NM). Mixing rule interaction parameters in each mixture have been optimized by ( ) W VL data and then optimized parameters have been used for three phase equilibrium calculations (VL H) W . Results show, for (T>302 K and P>775 bar) PR equation of state and for (T<290 K and P<159 bar) SRK equation of state have more accuracy in methane hydrate. In nitrogen hydrate mixture, SRK equation of state with 3% has minimum of error. Also TB temperature function with 7% error for (CH4-H2O) system and NM function with 8% error for (N2-H2O) system in PR equation of sate have lower error than others functions.