Flashing feeds in vacuum distillation columns:
What is the feed nozzle velocity?
By Ken Graf
The normal practice for calculating the inlet velocity of a two-phase feed to a distillation column is to calculate the flash of the feed at column pressure, and then to apply a two-phase-flow correlation(1,2) to check the flow regime of the mixture in the feed piping. The mixture could be in the bubble-flow regime, the dispersed regime, the annular regime, etc. The two-phase-flow regime indicates whether the mixture is all moving at one uniform high velocity, or whether the liquid is moving more slowly than the higher velocity vapor.
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