Mixed or Activity-Coefficient Approach

Mixed or activity coefficient Molecular Weight (MW) Ideal Gas Heat Capacity (CPjq) Vapor Pressure (Pvap) Heat of Vaporization (AHvap) Liquid Heat Capacity (CP,jq) Liquid Density (pj Solubility Parameter (d) Yes, however, best with heavy components that the EOS approach cannot deal with 

Equation of state Molecular Weight (MW) Critical Temperature (TJ Critical Pressure (PJ Acentric Factor (a ) Ideal gas Heat Capacity (CPjc) Liquid Density (pj Interaction Parameter (kjj) Yes, with adequate corrections of liquid density 

The simple approach is the most basic and least rigorous thermodynamic approach. In the simple approach or the Raoult s law, we assume that both the vapor and liquid phases are ideal. In this case, the general statement of equilibrium (Equation (1.48)) may be written as Equation (1.49), where pj is the vapor-phase mole composition of component i, P is the pressure, is the liquid-phase mole composition and (T) is the vapor pressure of component i as a function of temperature only. These properties are routinely available for pure components and we have extensively discussed how to obtain the required properties from pseudocomponents. 

A variation of this equation is to re-arrange the equation to obtain the equilibrium distribution ratio, yjx as shown in Equation (1.50). This distribution ratio is also known as the K-value for component i. Numerous correlations for K-values exist for a variety of pure components and pseudocomponents. The Braun-KlO (BK-10) correlation is a popular correlation of this type [6]. 

Once we obtain a JC-value at a given temperature and pressure, we can perform mass and energy balances include isothermal, isobaric and isenthalpic flashes. We can also use the ideal gas heat capacity of the vapor phase, heat of vaporization and heat of capacity of the liquid to represent the enthalpies of relevant vapor and liquid streams. 

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The mixed or activity-coefficient approach uses the concept of activity coefficients to separate out the effects of non-ideality because of component interactions and the effect of pressure. For the activity-coefficient approach, we can rewrite the general equilibrium statement as ... 

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