Panel Discussion

Dow Chemical was experiencing separation efficiency problems in one of its product towers. Tower internals consisted of four beds of structured sheet metal packing. Process calculations showed the tower was operating with 40% less equilibrium stages than design. Liquid maldistribution was expected and gamma scans were completed. In addition to using the standard four path grid scan layout, two additional scan lines crossing through the center of the tower were done to increase the chances of detecting maldistribution.

Effort was made to quantify the liquid maldistribution based on the gamma scan results to serve as input into a maldistribution sensitivity study. The conclusion from this analysis was the estimated maldistribution was great enough to have a significant effect on the tower efficiency. Not able to discern the root cause of the liquid maldistribution at the time (e.g. distributor design, fouled distributors, installation problem, problem in the packing, etc.), new high quality liquid distributors were designed and installed.

After installation of new liquid distributors, the tower started up and the separation efficiency improved to 98% of the design stages. This presentation includes discussion and results focused on the gamma scans and what can be done with gamma scan data to help with troubleshooting liquid maldistribution.