An evaluation of a two-stage spiral processing fine anthracite refuse

Testing was conducted to evaluate the performance of a two-stage Multotec SX7 spiral concentrator treating fine anthracite refuse. Two sets of samples were collected from an anthracite cleaning plant located in eastern Pennsylvania. One sample consisted of the thickener feed slurry (nominal-1.2mm) and the other consisted of the thickener underflow slurry. A third sample was prepared by desliming the thickener feed using a 102-mm diameter Krebs cyclone to produce a nominal-1.2+0.025mm product. The effects of slurry flow rate and solids concentration on spiral performance were investigated. For the+0.025mm material, the feed ash value could be reduced from 71% to 21%, while producing a refuse with an ash value of 91%. Regardless of whether the feed slurry was deslimed or undeslimed, the+0.025mm material would separate. The separation occurred even with the thickener underflow, which had been treated with flocculant. The-0.025mm material split in approximately the same proportion as the water.