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Dr. Siddhartha Mukherjee
Group Leader – Process
Lurgi India Company Pvt. Ltd.
High Performance Trays in
Distillation Operation
13
A conventional tray has three functional zones:
1. Active area for mixing vapour and liquid
2. Vapour space above the active area
3. Downcomer between trays
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A proper tray design involves balancing these
three zones to achieve the desired objectives. The
skill involved is in striking the best balance
between the active and downcomer areas.
For a greenfields plant, a well designed High performance trays function by improving
conventional tray generally provides the best performance in one or more of the three
solution for vapour-liquid contacting. However, functional zones.
with the passage of time, increasing demand for
throughput, has compelled operators to operate
the column to a limit where conventional trays
become a bottleneck.
Limits of a Conventional Tray
High Capacity Choices
C r o s s - F l o w Tr a y s w i t h Tr u n c a t e d
Downcomers
The introduction of high performance trays have
been one of the highlights of distillation processes Increasing the active bubbling area: A normal tray
in the 1990s. They offer practical solutions for has an area under the entering downcomer and
revamping processes to achieve higher capacities. over the exiting downcomer where liquid and
High performance trays can increase throughput vapour cannot come into contact. Typically, the
by 10 – 25% over a good conventional tray design. downcomer top area accounts for 15 – 25% of the
column cross-section area, leaving as little as 50%
for active bubbling area. This reduces the tray's
Active Area
Conventional Trays
Smaller Active Area
Active Area
High Performance Trays
Larger Active Area
Figure 1 : Conventional Trays vs. High Performance Trays