2 Gas-Liquid Equilibrium Ideal Behavior Applications to low pressuresSimplificationsthe gas phase behaves as an Ideal Gasthe liquid phase exhibits Ideal Solution Behavior
3 Ideal BehaviorThe equilibrium criteria between 2 phases a and b is,
4 Equilibrium Conditions The last criteria implies “tendency of a component to be in phase a or b is balanced” – “net mass transfer across phases is zero”
5 Ideal Behavior ModelGas phase behaves as an ideal gas (IG), and liquid phase behaves as an ideal solution (IS).These assumptions imply thatIG: molecular interactions are zero, molecules have no volume.IS: forces of attraction/repulsion between molecules are the same regardless of molecular species. Volumes are additive (Amagat’s Law).
11 Depletion Path Isothermal Reservoir Depletion Process for a Reservoir Oil with 2 Componentsz= fixedA1T= TCPaMBPBCPressurePDTxzy1aTemperature111z1=overall mole fraction of , y1=vapor mole fraction of , x1=liquid mole fraction of 
15 Bubble Point Evaluation Under Raoult’s law, the bubble point has a linear dependence with the vapor pressures of the pure components.Once the bubble point pressure is found, the equilibrium vapor compositions are found from Raoult’s law.
16 Dew Point CalculationAt the dew point the overall fluid composition coincides with the gas composition. That is.
17 Dew Point Calculation (Ideal Behavior Model) Find DP pressure and equilibrium liquid compositions