This is the most cost effective equipment for processing easily separated coals, especially run-of-mine coal for industrial use.
Raw material and water are fed into the top of the barrel.
The water combines with the fine coal and shale particles to form a viscous natural medium (1.0 to 1.3sg). The barrel is angled at 8 degrees, and the inside is scrolled. The combination of the viscosity of the medium and the dynamic effect of the barrel revolving (at 5 – 20 rpm) causes the coal to float near the top of the flowing stream.
The shale, which is heavier, sinks to the bottom and is carried by the scrolls back out of the top end of the barrel. The effective range for separation is between 1.5 and 1.8sg.
At the lower end of the barrel there is a sizing screen which lets water and particles smaller than 12mm drain through. This mixture is pumped to the cyclones.
The larger coal particles pass over a dewatering screen and on to the stock pile.