In Propane-Propylene (PP) Splitter, the phase equilibrium relationship is the key factor to achieve effective separation of propane and propylene.

From the perspective of physical chemistry, propane and propylene exist in a dynamic equilibrium between different phases. In Propane-Propylene (PP) Splitter, it mainly involves gas-liquid two-phase equilibrium. There is a difference in the boiling points of propane and propylene, and the boiling point of propylene is relatively low. When the mixed material enters the fractionator, under certain temperature and pressure conditions, the system tends to reach phase equilibrium.

In gas-liquid equilibrium, propane and propylene molecules in the liquid phase will continuously evaporate into the gas phase, and molecules in the gas phase will also continuously condense into the liquid phase. For propylene, due to its lower boiling point, it is easier to evaporate into the gas phase than propane at the same temperature. This process of volatilization and condensation continues until the chemical potential of propane and propylene in the gas and liquid phases is equal, at which time phase equilibrium is achieved.

Temperature has a significant effect on the phase equilibrium relationship. Increasing the temperature will cause more propane and propylene molecules to transform from the liquid phase to the gas phase, but the proportion of propylene molecules to transform is relatively higher, which is conducive to enriching propylene in the gas phase and achieving preliminary separation. The effect of pressure cannot be ignored either. Reducing the pressure can reduce the boiling point and also help promote the transfer of molecules from the liquid phase to the gas phase.

The design and operation of the Propane-Propylene (PP) Splitter requires precise control of these conditions to maintain the ideal phase equilibrium relationship. For example, the reasonable design of the height and number of plates of the distillation tower can help create sufficient gas-liquid contact opportunities, so that the phase equilibrium can develop in the direction of improving the propane-propylene separation efficiency, thereby obtaining high-purity propane and propylene products to meet the different purity requirements of these two substances in industrial production.