Location: Korea

Start-up time: 1998

Background:

Original xylene column, 7500mm ID column with (150) 4-pass valve tray, contained two columns arranged in series in Korea. Running results had indicated separation efficiency was low that tray efficiency was 80% in rectifying section and only 56% in stripping section. There was another train for xylene column (4900mm ID) that tray efficiency could be 80% in both sections. Customer decided to revamp 7500mm ID column in 1998. The purposes were as following:

(1) Capacity increase by 20%.

(2) Tray efficiency increase to be more than 85%;

(3) Operating flexibility increase to meet requirements for two production scenarios, which one was maximum production for PX and MX and the other was maximum production for OX.

Solution:

The following issues were listed after analyzing the original design for xylene column:

(1) Beams below trays were so high that capacity of trays was limited and tray efficiency was strong impacted;

(2) Many blind spots would be existed in bubble area, for no valves were arranged at the joints between beams and decks;

(3) Original design for vapor inlet was unreasonable. It would affect vapor and liquid distributions on adjacent trays.

Thus, related solutions were as following:

(1) Original valve trays (146 trays) would be replaced by ADV® trays;

(2) 4 trays were special design trays for transition;

(3) Special design trays made beams and aerated liquid flow in same direction;

(4) Inlet distributors were added.

Result:

(1) Capacity increased by 20%;

(2) Tray efficiency in whole column increased to be more than 95%;

(3) Reflux ratio decreased by 10%.