Mechanical means for increasing the grade of a flotation cell concentrate

Claim 1

In a flotation cell for treating coal slurry which contains unwanted refuse particles: a tank in which the coal slurry is contained; air supply means arranged to deliver air to the bottom of the tank to infuse fine air bubbles into the slurry; a power driven agitating means carried by the tank and operatively arranged to disperse the fine air bubbles through the slurry; and, a mechanical power driven froth agitator carried by the tank, said froth agitator comprising a rake having a plurality of spaced-apart depending teeth which are disposed radially with respect to the axis of rotation of the rake and at an angle with respect to a horizontal line that passes through the axis about which the rake rotates, said teeth slanting inwardly towards the axis of rake rotation, said rake being disposed in position to impart a rolling mechanical motion to the froth layer so that the froth is rolled back into the low solid pulp below the froth layer so as to dislodge unwanted refuse particles mechanically trapped between air bubbles.