Rotary dryer: Difference between revisions
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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.[[File:Single Shell Rotary Drum Dryer.jpg|thumb|Single Shell Rotary Drum Dryer]] The dryer is made up of a large, rotating cylindrical tube, usually supported by [[concrete]] columns or [[steel beam]]s. 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. |
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A '''rotary dryer''' is a type of [[industrial dryer]] used to reduce or minimize the [[moisture]] content of the material it is handling by bringing it into contact with a heated gas.<ref>{{cite web |title=Rotary Dryers |url=https://feeco.com/rotary-dryers/ |website=feeco.com |publisher=Feeco International Inc. |access-date=17 February 2021}}</ref> The dryer is made up of a rotating cylinder ("drum" or "shell"), a drive mechanism, and a support structure (commonly [[concrete]] posts or a steel frame). The cylinder is inclined slightly with the discharge end is lower than the material feed end so that material moves through the dryer under the influence of [[gravity]]. Material to be dried enters the dryer and, as the dryer rotates, the material is lifted up by a series of fins (known as [[Flights (rotary dryer)|flights]]) lining the inner wall of the dryer. When the material gets high enough, it falls back down to the bottom of the dryer, passing through the hot gas stream as it falls. |
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==Applications== |
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'''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. |
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Rotary Dryers have many applications but are most commonly seen in the [[Mining|mineral industry]] for drying sand, stone, soil, and [[ore]].<ref>{{cite web |title=Rotary Dryers |url=https://www.thyssenkrupp-industrial-solutions.com/en/products-and-services/mineral-processing/pyroprocessing-systems/dryers/rotary-dryer |website=www.thyssenkrupp-industrial-solutions.com |publisher=Thyssenkrupp Industrial Solutions |access-date=17 February 2021}}</ref> They are also used in the [[Food processing|food industry]] for granular material such as grains, cereals, [[Legume|pulses]], and coffee beans. |
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==Design== |
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== Working Principle == |
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A wide variety of rotary dryer designs are available for different applications. Gas flow, heat source, and drum design all affect the [[efficiency]] and suitability of a dryer for different materials. |
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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.<ref>{{Cite web |
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| url = http://www.han-da.com/rotary-dryer |
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| title = Rotary Dryer - Rotary kiln manufacturer |
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| last = Handa |
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| website = www.han-da.com |
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| access-date = 2016-02-29 |
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}}</ref> |
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== |
===Gas flow=== |
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The stream of hot gas 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 direction of gas flow combined with the [[Grade (slope)|inclination]] of the drum determine how quickly material moves through the dryer. |
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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. |
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===Heat source=== |
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The gas stream is most commonly heated with a burner using [[Fossil fuel|gas, coal or oil]]. If the hot gas stream is made up of a mixture of air and combustion gases from a burner, the dryer is known as "directly heated". Alternatively, the gas stream may consist of air or another (sometimes inert) gas that is preheated. Where burner combustion gases do not enter the dryer, the dryer is known as "indirectly-heated".<ref>{{cite web |title=Rotary Dryers |url=http://www.mitchelldryers.co.uk/products/rotary-dryers/ |website=mitchelldryers.co.uk |publisher=Mitchell Dryers |access-date=17 February 2021}}</ref> Often, indirectly heated dryers are used when product contamination is a concern. In some cases, a combination of direct-indirect heated rotary dryers are also used to improve the overall efficiency. |
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==Drum |
===Drum design=== |
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[[File:Double Shell Rotary Drum Dryer.jpg|thumb|Double Shell Rotary Drum Dryer]][[File:Triple Shell Rotary Drum Dryer.jpg|thumb|Triple Shell Rotary Drum Dryer]]A rotary dryer can consist of a single shell or |
[[File:Double Shell Rotary Drum Dryer.jpg|thumb|Double Shell Rotary Drum Dryer]][[File:Triple Shell Rotary Drum Dryer.jpg|thumb|Triple Shell Rotary Drum Dryer]]A rotary dryer can consist of a single shell or several [[Concentric objects|concentric]] shells, though any more than three shells is not usually necessary. Multiple drums can reduce the amount of space that the equipment requires to achieve the same [[throughput]]. Multi-drum dryers are often heated directly by oil or gas burners. The addition of a combustion chamber at the feed end helps ensure efficient fuel usage, and homogenous drying air temperatures. |
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==Combined |
===Combined processes=== |
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Some rotary dryers have the ability to combine other processes with drying. Other processes that can be combined with drying include cooling, cleaning, [[Industrial shredder|shredding]] and separating. |
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Other processes that can be combined with drying are: |
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*Cooling |
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*Cleaning |
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*Shredding |
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*Separating |
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== See also == |
== See also == |
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* [[Fluidized bed]] |
* [[Fluidized bed]] |
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* [[Flights (rotary dryer)]] |
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* [[Sectional cooler]] |
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* [[Kiln]] |
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==References== |
==References== |
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{{reflist}} |
{{reflist}} |
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<ref name="working principle">[http://www.rotary-kiln.org/Featured-Product/Rotary-Dryer.html Applied range of rotary dryer.], Applied range of rotary dryer..</ref> |
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<ref name="working principle">[http://www.rotarykilnhk.com/25-Rotary_dryer#con_two_2 Working principle of rotary dryer], Working principle.</ref> |
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[[Category:Dryers]] |
[[Category:Dryers]] |
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Latest revision as of 12:31, 24 August 2024
A rotary dryer is a type of industrial dryer used to reduce or minimize the moisture content of the material it is handling by bringing it into contact with a heated gas.[1] The dryer is made up of a rotating cylinder ("drum" or "shell"), a drive mechanism, and a support structure (commonly concrete posts or a steel frame). The cylinder is inclined slightly with the discharge end is lower than the material feed end so that material moves through the dryer under the influence of gravity. Material to be dried enters the dryer and, as the dryer rotates, the material is lifted up by a series of fins (known as flights) lining the inner wall of the dryer. When the material gets high enough, it falls back down to the bottom of the dryer, passing through the hot gas stream as it falls.
Applications
[edit]Rotary Dryers have many applications but are most commonly seen in the mineral industry for drying sand, stone, soil, and ore.[2] They are also used in the food industry for granular material such as grains, cereals, pulses, and coffee beans.
Design
[edit]A wide variety of rotary dryer designs are available for different applications. Gas flow, heat source, and drum design all affect the efficiency and suitability of a dryer for different materials.
Gas flow
[edit]The stream of hot gas 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 direction of gas flow combined with the inclination of the drum determine how quickly material moves through the dryer.
Heat source
[edit]The gas stream is most commonly heated with a burner using gas, coal or oil. If the hot gas stream is made up of a mixture of air and combustion gases from a burner, the dryer is known as "directly heated". Alternatively, the gas stream may consist of air or another (sometimes inert) gas that is preheated. Where burner combustion gases do not enter the dryer, the dryer is known as "indirectly-heated".[3] Often, indirectly heated dryers are used when product contamination is a concern. In some cases, a combination of direct-indirect heated rotary dryers are also used to improve the overall efficiency.
Drum design
[edit]
A rotary dryer can consist of a single shell or several concentric shells, though any more than three shells is not usually necessary. Multiple drums can reduce the amount of space that the equipment requires to achieve the same throughput. Multi-drum dryers are often heated directly by oil or gas burners. The addition of a combustion chamber at the feed end helps ensure efficient fuel usage, and homogenous drying air temperatures.
Combined processes
[edit]Some rotary dryers have the ability to combine other processes with drying. Other processes that can be combined with drying include cooling, cleaning, shredding and separating.
See also
[edit]References
[edit]- ^ "Rotary Dryers". feeco.com. Feeco International Inc. Retrieved 17 February 2021.
- ^ "Rotary Dryers". www.thyssenkrupp-industrial-solutions.com. Thyssenkrupp Industrial Solutions. Retrieved 17 February 2021.
- ^ "Rotary Dryers". mitchelldryers.co.uk. Mitchell Dryers. Retrieved 17 February 2021.