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The -28 mesh coal material which passed <br /> through the sieve bends or the .4 mm centrifugal dryer baskets <br /> is pumped to a flotation circuit that recovers the remaining <br /> i clean coal (third circuit) . This is a flotation circuit which <br /> utilizes the chemical action of a collector, a frother/promoter , <br /> and air . The equipment consists of 5 banks of cells equipped <br /> with air agitators . Air is bubbled into the bottom of the cell . <br /> The -28 mesh material is suspended in water in the cells . Diesel <br /> oil and NALFLOTE 8-839 are added to render the coal particles <br /> hydrophobic so that when they collide with a tiny air bubble, <br /> they attach to the bubble and are carried to the surface where <br /> they form a stable froth. The refuse particles remain in suspension <br /> and are discharged from the flotation cells and pumped to a large <br /> thickening tank where flocculants are added . The thickened <br /> material (underflow) is pumped to a vacuum disc filter where the <br /> solids are removed and conveyed to the refuse pile. <br /> The froth on top of the flotation cells <br /> containing the clean coal is skimmed off and dewatered in vacuum <br /> disc filters . The coal filter cake is sent to the thermal dryer <br /> for further drying. <br /> Mid-Continent operates two fluidizing- bed <br /> type thermal dryers . In these dryers heated air is forced through <br /> a bed of wet coal on a constriction plate. Surface moisture on <br /> the coal is evaporated by the air current . After the clean coal <br /> is dried it is conveyed to temporary storage bins before being <br /> loaded onto trucks and hauled to the train loadout facility. <br /> Coal is the primary fuel for the thermal dryers . Methane gas <br />