Question 1

What is flash calculation?

Accepted Answer

Flash calculation determines how a multicomponent mixture splits into vapor and liquid phases at given temperature and pressure using VLE relationships and mass balance.

Question 2

What is the Rachford-Rice equation?

Accepted Answer

Rachford-Rice is an iterative equation: Σ zi(Ki-1)/(1+(Ki-1)V) = 0, where zi is feed composition, Ki is K-value, and V is vapor fraction. It solves for vapor-liquid split.

Question 3

What is bubble point vs dew point?

Accepted Answer

Bubble point: temperature/pressure where first vapor bubble forms (V=0). Dew point: where first liquid drop condenses (V=1). Flash operates between these limits.

Question 4

What are K-values?

Accepted Answer

K-value (equilibrium ratio) Ki = yi/xi relates vapor and liquid compositions. For ideal mixtures, Ki = Psat,i/P. K>1 means component prefers vapor phase.

Process Tools

Flash Calculation

Flash Calculation

Preset Mixtures

Operating Conditions

Feed Composition

Flash Curve

Results