Gamma-ray CT as a complementary technique for structural inspection of tray-type distillation columns

• GCT was investigated as complementary technique for distillation column inspections.
• MCNPX Monte Carlo code has been used for simulations.
• Experimental validation was done on a tray type distillation column in Lab-scale.
• Tray damage was successfully detected by using gamma-ray tomographic scan.
• Using gamma CT technique, the optimum direction was proposed for vertical scanning.

Gamma-ray scanning method has been already used for troubleshooting analysis of the distillation columns in industries. The obtained density profile in this method will give useful information about either structure or process of the column. However, in situations such as damaged tray, the damage severity cannot be identified using conventional gamma-ray scanning method. In this study, gamma-ray CT technique has been investigated as a complementary technique for structural inspection of a tray-type distillation column. So, a laboratory scale distillation column containing damaged tray and overlapped downcomers along with a transportable tomographic system have been simulated using MCNPX Monte Carlo code. Image contrast higher than 75% was obtained for reconstructed results of simulated data. Furthermore, the damage fraction calculated from reconstruction result showed a difference about 3% in comparison with its true value. To validate the simulations, an experiment was performed on a Lab-scale distillation column for inspection of downcomers overlap which leads to unexpected peaks in the obtained density profile. A reconstruction error of less than 7.5% was obtained for both experiment and simulation reconstruction results. Simulation and experimental image reconstruction results show that structural details of the column inside can be effectively determined using gamma-ray tomographic scan method. The overall results are indicative of the fact that gamma-ray CT technique can be efficiently used as a complementary technique for structural inspection of tray-type distillation columns.