Calculation on the phase equilibrium and critical temperature of CH4/CO2

The phase equilibrium and critical temperature are the pivotal parameters for the application of biogas, especially the liquefied biogas. In this work, rapid estimation methods for the phase equilibrium (e.g. SRK, PR and PC-SAFT equations of state (EOS)) and critical temperature (e.g. MF, CVF, CP, GT, RK, MW and GC methods) of synthetic biogas (CH4/CO2) were summarized based on previous studies and the accuracy was then verified according to the experimental data. The results showed that PR EOS gave more accurate results when estimating the phase equilibrium of CH4/CO2. For the estimation of critical temperature of CH4/CO2, in the region with low CH4 composition (<50%), all the estimation methods except GC method gave the results close to the experimental data, while GC method produced obviously lower values. While in the region with high CH4 composition (>60%), only MF and CP methods gave the most accurate results. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.