Utilizing Gamma Scans to Monitor Fouling Accumulation in Packed Towers

In some processes, a common problem is the accumulation of fouling material in the packed beds of separation towers. Fouling can cause conditions such as liquid and/or vapor maldistribution and excessive liquid holdup in packed columns, resulting in a loss of efficiency, an increase in operating pressure drop and premature flooding. Fouling may result from foreign material entering a column or from polymerization or decomposition occurring inside the column. The fouling may start under normal conditions or begin to build due to abnormal operating conditions.

During a turnaround, a visual inspection can be performed on the upper and lower layers of packing, but unless the packing is removed, it is impossible to see fouling material within the bed. In some cases, towers with fouled beds are restarted without cleaning or replacing the packing, because no fouling was visually seen on the upper or lower layers of packing during the inspection. This can ultimately lead to costly unplanned outages.

Gamma scanning is a non-intrusive and cost-effective way to monitor a packed tower for the accumulation of fouling material. Many operators implement a routine maintenance program where the column is periodically scanned to monitor the progress of the condition over time. This type of monitoring program typically begins with a baseline scan of the column.

This paper will provide case studies that illustrate the effectiveness of utilizing gamma scans to monitor fouling accumulation in packed towers.