Distillation Downcomer Backup & Choke Flood Calculator
Calculate total clear liquid backup in downcomers (hdc), froth density aeration, head loss under the apron, and downcomer choke flood percentage.
Downcomer Dimensions & Flow
Downcomer Liquid Level & Safety
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Frequently Asked Questions
What is the difference between Downcomer Backup Flooding and Choke Flooding?
Backup flooding occurs when clear liquid head + tray pressure drop forces froth up the downcomer onto the upper tray deck. Choke flooding occurs when excessive liquid velocity causes vapor bubbles to become entrained in the downcomer liquid, choking the flow.
What is the maximum recommended downcomer backup limit?
Total froth height in the downcomer should not exceed 50% to 60% of tray spacing for high-pressure foaming systems (such as depropanizers) and 70% to 75% for non-foaming atmospheric systems.
How does downcomer apron clearance prevent vapor back-flow?
The bottom apron of the downcomer dips below the liquid level of the tray below (downcomer seal), creating a liquid trap that prevents ascending vapor from bypassing the tray perforations.