Distillation columns are among the tallest and most expensive vessels in a chemical plant. Their design integrates process simulation output (number of theoretical stages, reflux ratio, reboiler and condenser duties) with mechanical design (tray or packing type, column diameter, wind load, skirt support). Ohm Engineers fabricates distillation columns and fractionators at our Vadodara works as a secondary product line alongside heat exchangers — the vessel shell, nozzles, and supports are built to the drawing and code you attach.
Tray Columns vs Packed Columns
| Criterion | Tray Column | Packed Column |
|---|---|---|
| Typical diameter range | 0.6 m to 6+ m | 0.3 m to 3 m (structured packing) |
| Turndown flexibility | Moderate — weeping at low rates | Good with structured packing |
| Fouling tolerance | Better — trays can handle solids | Poor — packing channels block |
| Pressure drop | Higher per stage (~50–100 mm liquid) | Lower per stage (~20–40 mm) |
| Cost at large diameter | Lower above ~1.2 m diameter | Packing cost rises sharply with diameter |
| Maintenance | Manway access to inspect trays | Packing removal required for inspection |
Data Required for Column Fabrication Enquiry
- Inside diameter and tangent-to-tangent height (or number of stages × tray spacing + allowances)
- Design pressure and temperature — both top and bottom sections if different (e.g., vacuum at top, pressure at bottom)
- Tray type and number (sieve, valve, bubble cap) or packing type and height per bed
- Feed, product, and reflux nozzle locations and sizes
- Material of construction for shell, trays/packing, and internals
- Wind and seismic design code (IS 875, ASCE 7, UBC) for outdoor columns
- Insulation requirements and clip details
- Platform and ladder requirements (if applicable)
Common Specification Errors
- Not specifying tray spacing — default 450–600 mm is assumed; wrong spacing changes column height.
- Omitting bottom sump volume — affects reboiler liquid seal and startup time.
- Not defining vacuum design for top section when column operates under vacuum — shell thickness and stiffening rings change significantly.
- Specifying column diameter without confirming with hydraulic rating (jet flood, downcomer backup) from process engineer.
What to send Ohm Engineers
Attach the GA or licensor drawing with nozzle schedule, design pressure and temperature at top and bottom, tray count and type (or packing height per bed), MOC, and the applicable code (ASME Section VIII, IS). Reboiler and condenser are usually separate heat-exchanger orders — link them in the RFQ if you want one vendor to quote the full train. Use the technical RFQ form and upload P&ID excerpts if the GA is not yet issued.
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