Pyrite–Coal Depressants Interactions During Coal Reverse Flotation

This work investigates coal desulfurization by using reverse flotation. In this method, pyrite (the only source of sulfur in the studied coal) was separated from the meta-bituminous coal by using three different coal depressants (starch, dextrin and humic acid). A novel variable elimination approach was used to determine the contribution of the depressant type and the depressant concentration on the desulfurization performance. The results showed that the pyrite recoveries are influenced by the depressant type while the highest pyrite recovery was achieved in the presence of humic acid. Therefore, humic acid should be used in flotation rougher and scavenger cells in which the aim is to achieve high pyrite recovery. By contrast, the pyrite grades are affected significantly by the depressant concentration. Considering that the aim in flotation cleaner cells is to achieve high pyrite grade, any of the studied coal depressants can be successfully used but at high concentrations. This work demonstrated that the selection of flotation depressants depends on the type of flotation cells used in coal desulfurization.