Flotation of Coal Fines as Hydrophobic Flocs for Ash Rejection

Abstract

The flotation of coal fines in the form of hydrophobic flocs, which is termed floc‐flotation, for rejecting fine mineral matters from coal slimes has been studied in this work. This process consists of dispersion, selective hydrophobic flocculation of fine organic matters, and flotation of the fines as flocs. This study was performed on two coal slimes from China, namely Taixi anthracite and Tongshan coking coal. The experimental results have shown that floc‐flotation not only strongly increased the combustible recovery, but also greatly lowered the ash remaining in cleaned coals, compared with conventional flotation in the same reagent additions. This effect closely correlated with the size of flocculated organic matter. The larger were the flocs, the stronger the effect was. Also, it was found that flocculated coal fines had a much higher flotation rate than dispersed fines. In addition, the main parameters of the floc‐flotation process, namely nonpolar oil addition and slurry conditioning in the hydrophobic flocculation step were experimentally studied.

Keywords:

• Coal fines
• Hydrophobic flocculation
• Froth flotation
• Fine particle processing

Acknowledgment

The partial financial support to this work from the Consejo Nacional de Ciencia y Tecnología (CONACyT) of Mexico under the grant #485100‐5‐38214‐U is gratefully acknowledged.