Rotary dryer
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The rotary dryer is a type 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.
The dryer is made up of a large, rotating cylindrical tube, usually supported by concrete columns or steel beams. The dryer slopes slightly so that the discharge end is lower than the material feed end in order to convey the material through the dryer under gravity. Material to be dried enters the dryer, and as the dryer rotates, the material is lifted up by a series of internal fins lining the inner wall of the dryer. When the material gets high enough to roll back off the fins, it falls back down to the bottom of the 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 co-current flow), or toward the feed end from the discharge end (known as counter-current flow). The gas stream can be made up of a mixture of air and combustion gases from a burner, in which case the 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 dryer known as an indirect-heated type. Often, indirect heated dryers are used when product contamination is a concern. In some cases, a combination of direct-indirect heated rotary dryers are also available to improve the overall efficiency.
Brief Introduction Rotary dryer is suitable to dry metallic and nonmetallic mineral, clay in cement industrial and coal slime in coal mine,etc. Rotary dryer can be widely used to dry various materials, and it is simple to be operated.
Working Principle
The rotary dryer is a rotating cylinder which inclines slightly with the horizontal line. The raw material access into the chamber from the higher end, heating medium enters into from the low end, to counter current contact the raw material. Sometimes the heating medium and the raw material together cocurrent flow into the cylinder. As the drum rotates, the raw material, under the action of gravity, goes to the lower end. In the process of moving in the drum，the wet material to be hot by the heating medium directly or indirectly, by which the raw material dry. At the discharging end, the dry material takes out by the conveyor belt or screw conveyer. Inner drum there is equipped with lifting plate, the function of which is lifting the material and spreading down, make the contact surface of the material and hot airflow become big to enhance the dry efficiency and accelerate the material go forward. Generally the heating medium could be hot air flue gases, etc. After the heating medium pass through the drum dryer, there usually need to collect the dust in the air by the cyclone dust collector. If there need to be further reduce the dust in the tail gas,which should go through the bag filter or the wet dust collector, then to be discharged.[1]
Applications
Rotary Dryers have many applications but are most commonly seen in the mineral industry for drying sands, limestone, stones and soil, ores, fertilizers, wood chips, coal, iron sulphate, filter cakes, sewage sludge, etc.
Drum or Shell Variations
A rotary dryer can consist of a single shell or many, though any more than three drums is not usually necessary. Multiple drums can reduce the amount of space that the equipment consumes. Multi-shell dryers consist of several concentric tubes. Multiple shells allow the dryer to be utilized in a more compact space. The drums are often heated directly by oil or gas burners. The addition of a combustion chamber on the entry end helps ensure efficient fuel usage, and that homogenous drying air temperatures. As the material moves through the rotating drum is heated and moisture released. Some dryers also offer the option to cool, clean, shred, and/or separate the dried material.
Combined Processes
Along with drying rotary dryers have the ability to increase their economy by combining other process needs with drying. Other processes that can be combined with drying are:
- Cooling
- Cleaning
- Shredding
- Separating
See also
References
- ^ Handa. "Rotary Dryer - Rotary kiln manufacturer". www.han-da.com. Retrieved 2016-02-29.
- ^ a b Applied range of rotary dryer., Applied range of rotary dryer.. Cite error: The named reference "working principle" was defined multiple times with different content (see the help page).