Recovery of clean coal from polymer flocculated raw coal slurry

Abstract

The recovery of fine clean coal from waste streams using column flotation is recognized as an efficient and economical technique. However, due to the low percent solids (≈3% by weight) found in these fine waste slurries, the flotation columns have low capacities and are, thus, underutilized. In this study, a 3% (by weight) solids suspension of Upper Freeport coal was flocculated with polymers and concentrated to 10% (by weight) solids. The flocculated slurry was then floated using 250 git No. 2 fuel oil and 250 git MIBC, which provided a clean coal with 12% ash at an 80% yield. The results showed that flocculated coal could be floated effectively. Zeta potential and contact-angle data showed that the presence of polymer on the surface of the coal did not affect its hydrophobicity, and in some cases it improved the hydrophobicity as indicated by larger contact angles.