Drum drying is a method used to dry out liquids of wet materials. The rotary drum dryer is used to reduce or minimize the liquid moisture content in the biomass material(wood, wood chips, sawdust, straw, stalk, etc.). it is handling by bringing it into direct contact with hot gas. The totary drum dryer is widely used to dry various materials in the mineral industry such as sands, ores, fertilizers, wood chips, coal, limestone, stones and soil, iron sulphate, filter cakes, sewage sludge, etc.
Material to be dried enters the rotary drum dryer, and as the rotary drum dryer rotates, the material is lifted up by a series of internal fins lining the inner wall of the rotary dryer. When the material gets high enough to roll back off the fins, it falls back down to the bottom of the rotary drum dryer, passing through the hot gas stream as it falls. This gas stream can either be moving toward the discharge end from the feed end (known as cocurrent flow), or toward the feed end from the discharge end (known as countercurrent flow). The gas stream can be made up of a mixture of air and combustion gases from a burner, in which case the rotary drum dryer is called a direct heated dryer. Alternatively, the gas stream may consist of air or another (sometimes inert) gas that is preheated. When the gas stream is preheated by some means where burner combustion gases do not enter the dryer, the rotary dryer known as an indirectheated type. Often, indirect heated dryers are used when product contamination is a concern.
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