Flash Drum Calculator
Calculate vapor-liquid equilibrium in a flash drum using the Rachford-Rice equation for a binary system.
Inputs
kmol/hr
mole fraction
°C
kPa
Results
Vapor Fraction (ψ)
0.67
Vapor Flow Rate
66.67 kmol/hr
Vapor Composition (y₁)0.63 mole fraction
Liquid Composition (x₁)0.25 mole fraction
Liquid Flow Rate33.33 kmol/hr
How to Use This Calculator
- Enter the Feed Rate in kmol/hr and the Feed Composition (z₁) as the light-component mole fraction.
- Set the Flash Temperature in °C and Flash Pressure in kPa — these define the operating point of the drum.
- Enter the K-Value (equilibrium ratio K = y/x) for Component 1 (lighter) and Component 2 (heavier) at the operating temperature and pressure — obtain from process simulators or thermodynamic data.
- A K-Value above 1.0 means the component preferentially partitions to the vapor; below 1.0 it stays in the liquid.
- Read the Vapor Fraction (ψ) — 0 means all liquid, 1 means all vapor, values in between indicate two-phase equilibrium.
- Use Vapor and Liquid Compositions and Flow Rates to size the drum, downstream piping, and separators.
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