PNNL

Abstract

This paper describes measurement techniques developed and applied to characterize solids mobilization and mixing of Newtonian slurries that are subjected to transient, periodic, developing flows. Metrics to characterize mobilization and mixing are the just suspended velocity (UJS) and the cloud height (HC). Two ultrasonic instruments to characterize pulse jet mixing of slurries were developed and deployed to measure related metrics: the thickness of the settled bed (used to determine mobilization) and the concentration within the cloud as a function of elevation [C(Z)]. A second method, continuous sample extraction, characterization, and reinsertion was successfully used to measure average density and characterize the concentration within the cloud. Testing focused on mixing vessels using intermitent jet mixers oriented vertically downward. Descriptions of the instruments and instrument performance are presented. These techniques were an effective approach to characterize mixing phenomena, determine mixing energy required to fully mobilize vessel contents, and to determine mixing times for process evaluation.