Mixing efficacy and residence time distribution measurement in heavy water upgradation plant using radiotracer

To evaluate the efficiency of catalyst packing and to characterize the liquid phase flow dynamics in a heavy water distillation column, a series of residence time distribution (RTD) measurements were carried out using radiotracer. For a RTD measurement, about 1 mCi (37 MBq) of 82Br as ammonium bromide was injected as an impulse and its movement was monitored by thirty NaI(Tl) detectors at the inlet and outlet of the five catalyst cages present in the distillation column. The tracer measurements were carried out at varying liquid phase flow rate from 80 to 180 LPH. From the radiotracer data, it was concluded that radial distribution of the liquid phase at the top and bottom of the five cages was uniform. However, a slight non uniformity was observed in the middle cages. The residence time of the heavy water in the five cages varying the liquid flowrate was found to be varying from 4.2 min to 36.7 Min. To characterize the liquid mixing in each section of the distillation column, axial dispersion model was used using convolution method. The model parameter peclet number (Pe) was used to characterize the mixing. The Pevalues for the five sections were found to be varying from 7 to 35. The Pevalue suggests that flow of the liquid phase in the column was close to the plug flow in bottom three sections as desired.