Xylene Column Revamp
Start-up time: 1998
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.
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.
(1) Capacity increased by 20%;
(2) Tray efficiency in whole column increased to be more than 95%;
(3) Reflux ratio decreased by 10%.