Details

An overall and component mole balance are performed:

,

,

where is the number of moles, the superscripts , and refer to the feed, liquid and vapor streams and the subscript refers to a component (methanol or water).

Overall and component energy balances with the reference state and :

,

,

,

where is enthalpy (kJ).

The enthalpies of each stream are calculated using heat capacities (kJ/(mol K)) and heat of vaporization (kJ/mol):

,

,

.

The flash drum has a single equilibrium stage, so the exiting liquid and vapor streams are at the same temperature, .

Saturation pressure of the components in vapor-liquid equilibrium is calculated using the Antoine equation:

,

where , and are Antoine constants for each component, and is in bar.

Raoult's law is used for the exit streams to find the vapor-liquid equilibrium compositions:

,

where and are the liquid and vapor mole fractions.

The sum of the mole fractions times their saturation pressures is the total pressure .

The screencast video at [1] explains how to use this Demonstration.

Reference

[1] Adiabatic Flash Drum with Binary Liquid Feed [Video]. (Dec 8, 2016) www.colorado.edu/learncheme/separations/AdiabaticFlash.html.