Coal Preparation » Fine Coal
The use of frothers in the froth flotation process is essential in achieving acceptable process performance through the formation of sufficient numbers of stable bubbles to maximise particle-bubble contact and bubble surface area to carry hydrophobic particles to product.
Frother has traditionally been added to the flotation feed slurry. During bubble formation, frother molecules need to diffuse from the bulk solution to the interface being formed, a relatively slow process. Previous work has shown that when the frother is added to the gas phase as an aerosol, process performance may be improved and/or frother demand may be reduced, as the frother acts directly at the interface being formed and the need for frother molecules to diffusion from the bulk solution to the interface is avoided.
The aim of this project was to develop the best implementation methodology of safe aerosol frother addition and confirm the effectiveness of this process in improving flotation process performance and/or reduced frother demand on a large-scale flotation system.
Methods for successfully adding atomised frother directly into the process air stream as aerosol before entering the downcomer of plant-scale Jameson cells were developed. For frothers with low flashpoints such as MIBC, atomisation was done as a frother-water mixture to mitigate the fire/explosion hazard of atomized frother by dilution and cooling.
The metallurgical performance achieved in terms of product yield and ash values for the base case when frother was added to the flotation feed slurry were compared with those for aerosol frother added to the process air. Different frother concentrations ranging from 7ppm to 16ppm were examined. In all cases, the product yield for the aerosol frother addition was higher than the base case results with the yield improvement ranging from 2.5 to 10 percentage points. The average increase in product yield attained when the frother was added as an aerosol to the process air rather than to the feed slurry was 6.5 percentage points. The average increase in product ash of 0.25 percentage points was determined to be statistically not significant, meaning that it was within experimental variability.