Patent ID: 7087174

Claim:
A method of enhancing the recovery of useful coal from screenbowl centrifuge separation operations comprising a) discharging a slurry of coal into the screenbowl centrifuge; b) adding to a low shear zone of the screeynbowl centrifuge, from about 0.03 lbs active polymer/ton dry solids in centrifuge to about 0.70 lbs active polymer/ton dry solids in centrifuge, of a cationic terpolymer, wherein said catiomc terpolymer is prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.1 to about 10 mole percent of one or more hydroxyalkyl (meth)acrylates and from one to about 98.1 mole percent of one or more noniome monomers to allow solids to be flocculated without being torn apart by shear forces; c) centrifuging the slurry to separate the flocculated solids from an effluent; and d) recovering useful coal from the slurry.