Material tumbling

Trommel efficiency is affected both by geometrical and operational factors, such as length, diameter, angle of slope, rotational speed, and feed rate. Rotational speed is the most crucial operational parameter, as it must be maintained at an optimum value. Optimum rotational speed occurs when the waste material tumbles in the drum forming a cascade, which means that waste material is partially carried up the interior wall of the rotating drum, reaches about the maximum height, and then falls back on the bottom. The optimum rotational... 

The same principle of agglomeration can be applied at multiple transfer points from belts to belts, on shaking or vibrating conveyor decks, or on steeply inclined belt conveyors where material tumbles downward against the upward motion of the belt [B.48, B.97] (Section 8.1, Figs. 8.14, 8.15, and 8.16). 

StUl another ore preparation is the nodulizing process where the ore is heated in a rotary kiln to incipient fusion. The tumbling action in the kiln causes the phosphate ore to cohere and form spheroidal agglomerates. Combustion of carbon monoxide from the furnaces is used along with supplemental fuel to supply heat to 1300—1500°C. A boring bar is used near the kiln discharge to aid in breaking up the fused ore. The material is then cooled, cmshed, and screened to the appropriate size for furnace feed. 

Usually not suited for materials smaller than 30 mesh. Material does not tumble, except in Roto-louvre dryer. Latter operates at higher temperatures Suited to smaller objects that can be loaded on each other. Can be used to convey materials through heated zones. Roto-louvre not suited. Not apphcahle Special designs are required. Suited to veneers. Roto-louvre not applicable... 

Percentages of material greater than 50% of the maximum size are about 50% from rolls, 15% from tumbling mills, and 5% from closed circuit ball mills. 

---