Abstract
The residence time distribution of pulp was determined in a flotation bank composed of 7 flotation cells located in the northern part of Chile. The study focused on determining what fraction of the flotation cell volume was used effectively for value separation. Soluble tracer concentration measurement was carried out using Lithium Chloride (LiCl) and Magnesium Chloride Hexahydrate (MgCl2 * 6H2O) as tracers. The measurement was conducted along the flotation bank corresponding to the rougher flotation circuit (industrial plant). The results allowed the effective volumes of pulp in the flotation cells to be estimated. The tracers exhibited drastic concentration changes. It is believed that this observation is indicative of the large amount of pulp that overflowed from the lip of the cells. In other words, a significant amount of tracer exited as part of the concentrate stream. This behavior was attributed to abrupt variation of level control and air injection problems in industrial cells. In general, the variability of the residence time results, and tracer concentration distributions are indicative of operational variability, bank instability, and operating inefficiencies of the operation strategy. The latter was corroborated in the field as flotation cells showed clearly that the fluid (pulp) behavior was far removed from ideal operation (i.e., accumulation, short-circuiting, dead zones, etc).
This paper provides a robust background that supports the importance of quantifying the residence time distribution at the industrial level using different tracers, in order to identify mitigation strategies in operating and controlling flotation cells.