The rotary dryer is a form of industrial dryer employed to reduce or minimize the liquid moisture content of the material it is handling by bringing it into direct contact with a heated gas. A rotary dryer is said to be of the direct type if by virtue of its design, heat is added to or taken off the solids by direct exchange between the gas and solids. The direct heat dryer would be the simplest and also the most economical class.
They are utilized whenever a direct exposure to the gas or air is not really detrimental for the fed. When high temperature is required for rotary evaporator in a direct-heated rotary dryer, a combustion chamber can be used and once low temperature is necessary on the contrary, for thermolabile materials, steam coil can be used. Rotary dryer may also be said to be indirect when the heating medium is separated from exposure to the solid with a metal wall or tube.
Single Shell Rotary Drum Dryer – The dryer is made up of a sizable, rotating cylindrical tube, usually backed up by concrete columns or steel beams. The dryer is inclined to slopes slightly in order that the discharge end is less than the material feed end so that you can convey the material with the dryer under gravity. Material to get dried enters the dryer, and as the dryer rotates, the content is lifted up by a number of internal fins lining the inner wall from the dryer. When the material gets high enough to roll back away the fins, it falls back to the foot of the dryer, passing from the hot gas stream because it falls.
This gas stream either can be moving toward the discharge end from the feed end (known as co-current flow), or toward the feed end from your discharge end (called counter-current flow). The gas stream can be made up of a blend of air and combustion gases from the burner, whereby the dryer is named a direct heated dryer. Alternatively, the gas stream may include air or another (sometimes inert) gas that is certainly preheated. If the gas stream is preheated by some means where burner combustion gases usually do not go into the dryer, the dryer known as an indirect-heated type. Often, indirect heated dryers are employed when product contamination is an issue. In some instances, a mixture of direct-indirect heated rotary dryers are also available to boost the overall efficiency.
A rotary dryer is suitable to dry metallic and nonmetallic mineral, clay in cement industrial and coal slime in coal mine, etc. Rotary dryers may be widely used to dry various materials, and are easy to operate.
Rotary Dryers have many applications but are most frequently observed in the mineral industry for drying sands, limestone, stones and soil, ores, fertilizers, wood chips, coal, iron sulphate, filter cakes, sewage sludge, etc. May also be applied to food industry mainly for liquids along with granular material like food grains, cereals, pulses,coffee beans, fermented tea leaves, etc.
Drum or shell variations: Double Shell Rotary Drum Dryer. Triple Shell Rotary Drum Dryer – A rotary dryer can consist of one particular shell or many, though any more than three drums is not usually necessary. Multiple drums is effective in reducing the quantity of space that the equipment consumes. Multi-shell dryers include several concentric tubes. Multiple shells enable the dryer to get utilized in a more compact space. The drums are often heated directly by oil or gas burners. Incorporating a combustion chamber on the entry end helps ensure efficient fuel usage, which homogenous drying air temperatures. Since the material moves through the rotating drum is heated and moisture released. Some dryers also provide the option to cool, clean, shred, and separate the dried material.
For evaporating moisture from concentrates or some other products from plant operations, Rotary Dryers are designed and constructed for top efficiency and economy in fuel consumption. Whenever possible to use heat direct to the material to be dried, Rotary Dryers of the Direct Heating Design are employed. Should it be unachievable to use heat direct towards the material to be dried, Rotary Dryers from the Indirect Heating Design could be furnished so that the heated gases will not come in direct connection with the content.
Rotary Dryer is an easy, inexpensive unit for reducing the moisture content of flotation concentrates, as well as chemical and industrial products. Frequently the saving of shipping weight so effected will pay tjihbx the dryer in a month or two. Difficulties from freezing while in transit can also be eliminated. Many industrial projects are now using Dryers for control and production purposes on many materials.
Three main types of rotary evaporator can be supplied. The direct heat unit is used when it is permissible for that drying gases to come in direct connection with the material being dried. Partition plates boost the heating surface. Drying could be by heat or exhaust gases off their operations. If this type of drying gas features a deleterious effect on the product, then an indirect form of dryer may be supplied. A further derivation is the Tedrow Steam Dryer.
The movement of the material is due to combined effect of inclination of the shell towards the horizontal and the internal tumbling action or mechanical turn over thus the name tumbling dryer. The character in the feed determines the directions of gas flow with the cylinder in fact it is in accordance with the solid. This drying equipment may also perform batch or continuous processing of the wet feed.