Once the process design stage ends, the equipment design begins. This stage of design converts process requirements into actual hardware.
Selection Guide for Tray Column
The factors discussed below influence the choice between trays & packings. As these are guidelines for selection of trays or packings for a particular service, it is recommended to analyze each design case on its own merit for selection.
|
Sr. No. |
System Favoring Tray Column |
System Favoring Packed Column |
|
01 |
Solid handling |
Vacuum system |
|
02 |
High liquid rate feed composition and
temperature |
Low pressure drop application, Revamps- The pressure drop reduction |
|
03 |
Large diameter columns | Small diameter columns< 900 mm |
|
04 |
Performance prediction is easy | Corrosive system Or Foaming system |
Types of Tray
The particular tray selection and its design can materially affect the performance of a given distillation, absorption, or stripping system. Each tray should be designed so as to give as efficient a contact between the vapors and liquid as possible, within reasonable economic limits.
A] SCM Valve Tray
Valve trays are perforated sheet metal decks on which round, liftable valves are mounted. The vapors flows through valves which are installed parallel to the outlet weir.
Vapour flows lifts the caps, thus self creating a flow area for the passage of vapour. The lifting cap directs the vapour to flow horizontally into the liquid, thus providing better mixing than is possible in sieve trays.Valve trays combine high capacity and excellent efficiency with a wide operating range.
Fixed Valve Trays Floating Valve Trays Advantages:
- Excellent liquid/ vapors contacting.
- Higher capacity.
- Higher flexibility than sieve trays.
- Can handle higher loadings.
- Low-pressure drop than bubble cap.
B] SCM Sieve Tray
Sieve trays are flat perforated plate in which vapour rises through small holes in tray floor, & bubbles through liquid in fairly uniform manner. They have comparable capacity as valve trays.
Vapour passes straight upward through the liquid on the plate. The arrangement, number and size of the holes are design parameters.
Advantages:
- Simple construction Low entrainment,
- low cost Low maintenance cost
- Low fouling tendency
Disadvantages:
- Less-flexible to varying loads than
C) SCM Bubble Cap Tray
Riser or chimney fitted over each hole, and a cap that covers the riser. The cap is mounted so that there is a space between riser and cap to allow the passage of vapour. Vapour rises through the chimney and is directed downward by the cap, finally discharging through slots in the cap, and finally bubbling through the liquid on the tray.
