Effect of saline water on the flotation of fine and coarse coal particles in the presence of clay minerals

• Saline water increased the recovery of mineral matter in fine coal flotation more significantly.
• Froth stability was increased in both fine and coarse coal flotation using saline water.
• Saline water enhanced particle aggregation in fine coal flotation but not in coarse coal flotation.
• Particle aggregation was related to mineral entrapment, especially in fine coal flotation.
• Froth stability was related to mineral entrainment.

This research addresses two important issues confronting coal flotation plants in Australia, the use of saline water and the processing of clayey coal. Two coal samples obtained from BHP Billiton Mitsubishi Alliance (BMA) and Xstrata were tested to represent coarse coal flotation and fine coal flotation, respectively. Saline water with low, medium and high ionic strengths and individual electrolytes encountered in the flotation plants were used. It was found that saline water had a more pronounced effect on fine coal flotation than coarse coal flotation despite similar mineral compositions and clay mineral types present. Although saline water increased froth stability in both fine and coarse coal flotation, coal particle aggregation only occurred between fine coal particles resulting in an increased recovery of coal particles as well as the entrapment of fine gangue minerals.