Use Quantitative Gamma Scans to Troubleshoot Maldistribution on Trays


Quantitative, multichordal gamma-scan analysis is invaluable for diagnosing maldistribution and channeling in distillation columns. The graphical tool introduced here is a convenient way to visually represent the data.

Distillation towers containing conventional or high-capacity trays occasionally experience liquid and/or vapor maldistribution or channeling. Maldistribution and channeling form zones of high vapor velocities, where excessive entrainment and premature flood originate; this leaves other zones vapor-deficient, with excessive weep that lowers tray efficiency. Overall, maldistribution reduces tray efficiencies, increases the reflux, reboil, and energy requirements, and creates entrainment, premature flood, and tower capacity bottlenecks. Maldistribution is difficult, often impossible, to diagnose with conventional troubleshooting techniques, such as vendor software, pressure drop measurements, and single-chord qualitative gamma scans.

Author Bios: 

Henry Z. Kister

Henry Z. Kister is a Fluor Corp. senior fellow and director of fractionation technology (phone 1-949-349-4679, email He has over 30 years experience in design, troubleshooting, revamping, field consulting, control and startup of fractionation processes and equipment. He is the author of three books, the distillation equipment chapter in Perry’s Handbook, and about 90 articles, and has taught the IChemE-sponsored “Practical Distillation Technology” course more than to 350 times. A recipient of several awards, Kister...Read more

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