Effects of operating parameters on residence time distribution in a REFLUX flotation cell

Residence time distribution (RTD) is a critical parameter in design and optimization of flotation processes and
machines. RTD measurements provide valuable indication into the distribution of residence times experienced by
particulates (e.g., particles, oil droplets) within the system, enabling the identification of flow regimes and po
tential issues such as short-circuiting, dead zones or inadequate mixing. While previous studies in the literature
have generally focused on RTD measurements in mechanical flotation cells, there are limited experimental
studies available for pneumatic flotation cells. In this study, RTD measurements were performed to characterize
the type of flow regime in the REFLUXTM Flotation Cell (RFC), and to investigate the impacts of operational
parameters, including bias, feed flux, and gas flux, using a laboratory-scale RFC-100. An impulse-response
methodology was employed with a KCl solution used as a tracer in a two-phase (liquid–gas) system. Large
and Small Tanks in Series (LSTS), N-mixer in Series, and Perfect Mixer models were applied to a database created
by experimental results. The results revealed that the fluid behavior in RFC-100 approached a plug-flow pattern
rather than perfect mixing in the two-phase (liquid–gas) system. Furthermore, an increase in bias resulted in a
decrease in mean residence time (MRT), and the tracer concentration inside the cell could be adjusted by varying
the gas flux under the same feed flux.