Simulation of oil-vapor condensing recovery process based on several state equation models
LI Yinglin, TAN Laizai, ZHANG Xiaosong
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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.