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Tower Scan

Dislodged Tray, Flooded Packing Found Without a Shutdown

One of the separation steps in the manufacture of a speciality chemical involves removal of impurities in a nitrogen stripper. To accomplish this, the feed is introduced onto the distributor tray of a packed bed column. This tray is designed to hold 6 inches of liquid and to evenly distribute it onto the packed bed. Uniform distribution is important to ensure good vapour/liquid contact to maximize the removal of impurities from the feed. Product specifications were not being met so Tracerco engineers were called to site to diagnose the problem.

Tray tower damage

Tracerco used the TRU-SCAN®/Tru-Grid™ Scan technique to determine if the distributor was in place and holding liquid, the location of the top and bottom of the packed bed, and if the mean density was uniform through the bed. In this case the scan did not show any radiation absorption for the distributor tray at the location given on the column drawings. This suggested that the tray was either dry or damaged and therefore not holding liquid. Increased absorption was noted above the expected location for the top of the packed bed. It therefore looked as though the distributor tray had become dislodged and fallen onto the packing. Scans of the packing didn’t show constant density, further suggesting maldistribution due to distributor tray problems. A 3-foot section of the bottom of the packing was very dense suggesting that the liquid level was very high, engulfing part of the packing and further reducing effectiveness. Tracerco’s techniques were able to pinpoint the cause of the stripper separation problems and help the plant to effect speedy repairs and a rapid return to full production of high quality product.

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