Phase Separation of Reactor Effluent

With the reasonable assumption that the phases in a heterogeneous mixture are in phase (physical) equilibrium for a given reactor effluent composition at the temperature and pressure to which the effluent is brought, process simulators can readily estimate the amounts and compositions of the phases in equilibrium by an isothermal (two-phase)-flash calculation, provided that solids are not present. When the possibility of two liquid phases exists, it is necessary to employ a three-phase flash model, rather than the usual two-phase flash model. The three-phase model considers the possibility that a vapor phase may also be present, together with two liquid phases. 

Consider the following examples of phase-equilibria calculations for industrial reactor effluents  

Vapor-liquid case. The reactor effluent for a toluene hydrodealkylation process, of the type discussed in Section 4.3, is a gas at 1,150°F and 520 psia. When brought to 100°F at say 500 psia by a series of heat exchangers, the result is a vapor phase in equilibrium with a single liquid phase. A two-phase flash calculation using the SRK equation of state gives the following results  

Reactor Effluent Phase Equilibrium for a Toluene Hydrodealkylation Process 

Component Effluent (Ibmol/hr) Vapor (Ibmol/hr) Liquid (Ibmol/hr) 

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