Selection of State Equation and Innovative Process Design for Removing CO2 by Azeotropic Distillation

A thermodynamic consistency test was performed on the gas‐liquid equilibrium data of three binary mixtures, namely, CH4‐C2H6, CH4‐CO2, and C2H6‐CO2, measured by Wei and Brown at three different temperatures to verify the reliability of the data. Peng‐Robinson (PR), Redlich‐Kwong (RK), and Soave‐Redlich‐Kwong (SRK) equations of state combined with Margles mixing rules were used to fit the gas‐liquid equilibrium data of these three models. The results indicate that the PR‐Margles mixed model can make the average absolute deviation of test data and calculated data pressure and vapor fraction less than 0.19 and 0.0025, respectively, which is superior to RK‐Margles and SRK‐Margles mixed models. Finally, an azeotropic distillation method with C2H6 as entrainer for removing CO2 from natural gas was explored and optimized. To remove CO2 from natural gas by azeotropic distillation, the isothermal gas‐liquid equilibrium data of binary systems of CH4, C2H6, and CO2 obtained by previous experiments were used to verify the C2H6‐CO2 azeotrope system. A new practical and economical process of azeotropic distillation decarbonization was designed and optimized, providing a theoretical basis for CO2 capture from natural gas.