Promotions for Further Improvements in Multiple Downcomer Tray Performance

In this work, promotions of multiple downcomer trays are studied and discussed. Directing baffles were added to the tray deck to reduce the liquid back-mixing, resulting in a uniform liquid distribution. A bed of structured packing was hung under the tray deck to capture and reduce the entrainment. The experimental results showed that, when the F factor increased to 2.0, the entrainment fraction of the tray with the packing was 0.003 kg of water/kg of air, obviously lower than that of the tray without the packing, 0.014 kg of water/kg of air. This indicates that the combined packing technology could reduce the entrainment significantly. Antidumping units were applied to prevent the liquid from dumping through the orifices. Experiments with the ethanol/water system showed that the tray efficiency was 10-15% higher than that of conventional multiple downcomer trays. Additionally, in the revamp of an olefin plant, DJ-3 trays, with all the promotions mentioned above on conventional multiple downcomer trays, were used in several fractionators to replace the valve trays and sieve trays on a 1-for-1 basis, resulting in 30% increase in the ethylene production rate. Moreover, it was found that the overall tray efficiency of the DJ-3 trays is as high as that of valve trays in the demethanizer and the C2 splitter, as well as 24% higher than that of sieve trays in the C3 splitter.