The selection of state equation for simulation of condensing oil-gas recovery is still questionable. In this study

by establishing the phase equilibrium model and thermodynamic parameter models

simulation results of condensing oil-vapor recovery process are compared. The phase equilibrium model is composed of state equations

substance balance equation

and thermodynamic equilibrium equation

with model iteration steps. State equations include SRK

PR

TJS and ideal-gas state equation. The simulations present following results. (1) The simulation results are verified by existing test data. For TJS equation

average deviations of gas and liquid mole fractions are 4.03% and 3.54%

respectively

meeting the precision requirement. For SRK equation

at mole fractions of component higher than 5%

average deviations of CH4 and C2H6 are 2.8% and 3.5%

respectively

while at mole fractions less than 5%

average deviation of C3H8 is 18.5%

meeting the precision requirement. (2) When the oil-gas mixture is considered as ideal gas

the simulation results differ greatly from those with the real-gas state equations

such as SRK

PR or TJS equation

so for the oil-vapor mixture can not be treated as ideal gas

and SRK and TJS equations are preferred. (3) The simulation results of SRK

PR

TJS and Aspen Plus software are equivalent

while the simulation result of PR model is slightly worse. The mathematical model and simulation analysis on condensing oil-vapor recovery process provide theoretical references for future experiment.