Improving mixing efficiency in a closed circuit water flow rig for radiotracer studies

Abstract

Investigations were conducted on a laboratory scale water flow rig to determine the flow characteristics for improving mixing efficiency in the tanks for radiotracer studies. Approximately 20 mCi eluates of ⁶⁸Ga from ⁶⁸Ge/ ⁶⁸Ga generator were injected into the fluid at 1.0 and 1.2 minutes pulses in a second and third generation system. At measured mean residence time (τ_m) per tank of 1.68 - 2.04 minutes in the second generation, mixing efficiency was in the range 27.91 - 33.88%. Mixing efficiency of 81.57 - 90.98 % showed improvement for the modified rig with τ_m per tank between 7.80 and 8.70 minutes. The cumulative residence time distribution data for the last tanks in the two generations were fitted by perfect mixers in series model using program tools in Microsoft Excel. The volumetric flow rates of 4.55 and 8.0 L/min for the two rigs conformed to the values measured by radiotracer pulse velocity method, indicating that the flow meters functioned correctly. The modified rig with scaled-up mixing techniques could serve as platform for training in evaluating mixing vessels and flow meters in industrial process plants.