基于多种状态方程模型的冷凝法油气回收对比

Simulation of oil-vapor condensing recovery process based on several state equation models

冷凝法回收油气过程的模拟计算采用何种状态方程尚无定论,建立油气混合物相平衡模型和组分热物理参数模型,进行油气回收过程模拟的对比。相平衡模型主要由状态方程、物质的量平衡方程、热力学平衡条件方程和模型迭代步骤组成,状态方程包括SRK方程、PR方程、TJS方程和理想气体方程。模拟结果表明:状态方程选用SRK、PR和TJS方程,经实验数据验证,满足精度要求;将油气视为理想气体时,计算结果与实际气体状态方程的模拟结果相差较大,冷凝温度越高,偏差越大,油气混合物在冷凝过程中不能视为理想气体;SRK、PR、TJS和Aspen Plus的模拟结果比较一致,相平衡计算应优先选用SRK或TJS方程。

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.