What is a rotary dryer?
Rotary dryer is a very widely drying equipment used to reduce the moisture content of the feed materials by direct or indirect heating ,Its body is a tilted or horizontal and rotating cylinder, Rotary drum dryer occupies a very important position in the chemical, agricultural, coal, building materials, and light industrial industries.
How does a rotary dryer work?
Rotary dryers work by tumbling and drying material in a rotating drum.The wet material enters the dryer from the front end, and when it passes inside the rotating cylinder, it is dried by effective contact with the hot air passing through the cylinder or the heated wall. The dried product is collected from the lower rear end of the cylinder.
Rotary dryer construction and components
The rotary dryer is composed of a series of parts such as drum, large gear, pinion, transmission mechanism, support roller,roller ring and so on. Drum dryers under 75 HP can use large sprockets and chain drives, and small drums can use the frictional drive from the support drag wheel and the roller ring.
- Raw material feed port 2. Rotary drum 3. Roller ring 4. Connection flanges 5. Large gear 6. Flue gas outlet 7. Motor 8. Gear reducer 9. Couplings 10.Gear 11.Support roller 12. Bearings and bearing housings 13. lifting plate 14. Inspection door
Indirect-heated rotary dryer
The heat is heated by conduction through the metal wall to the material to be dried. Its characteristic is that only a small amount of air is needed to take away the moisture, and the exhaust gas takes away less heat, so the thermal efficiency is high. In addition, the high temperature of the tail gas is conducive to solution recovery and less dust.
Indirect heating type dryer is the whole dryer outer cylinder built in the furnace. The flue gas from the combustion chamber sweeps through the outer wall of the rotor into the barrel and is then removed from the atmosphere by the induced draft fan. When the flue gas passes through the outer and inner walls of the drum, it indirectly heats the material in the middle.
Who use the rotary dryer
Rotary dryers are available for both large and small projects. They are available in a variety of sizes to accommodate a wide range of products and moisture contents. Small rotary dryers are typically available in a few cubic meters to tens of cubic meters, medium-sized ones in hundreds of cubic meters, and large rotary dryers in 600-1400 cubic meters. The volume of the dryer depends on the diameter and length, ranging from 2 feet to 18 feet in diameter. Different volumes of drums correspond to different product yields. When choosing a new or used rotary dryer, volume is a parameter that must be considered.The price of a rotary dryer depends on the volume size of the dryer and the materials used in the dryer.
Rotary dryer design
When you choose to use a drum dryer, you must first perform design calculations for the dryer. Rotary drum dryers can be designed in stainless steel or carbon steel materials. If the product is corrosive, stainless steel can be used instead of carbon steel. If the product is food grade, food grade stainless steel such as SUS304 can be used. carbon steel drums are designed to withstand inlet temperatures of 530°c – 600°c. With special materials, such as 316L, drum dryers can obtain higher inlet temperatures.
The internal component of the dryer (lifting plate) affects the performance of the dryer to some extent. The function of the lifting plate is to send the material to the inner unit of the drum as quickly as possible. The purpose of the internal device is to ensure the violent stirring of the material and the uniform distribution of the material during the rotation of the drum, as well as the sufficient contact between the gas and the wet material.
Advantages of rotary dryer
1.Rotay dryer has strong overload resistance, large processing capacity, low fuel consumption and low drying cost;
2. Rotary Drum dryer can change the operating parameters according to different material properties, so that the material can form a stable full break fabric screen in the dryer cylinder, and the quality heat exchange is more adequate;
3. Rotary Drum dryer adopts new feeding and discharging device, which eliminates the phenomenon of vertical dryer feeding blockage, discontinuity, unevenness and material return, and reduces the load of dust removal system;
Disadvantages of rotary dryer
If the dryer is larger and the airflow speed is faster, there will be dust entrainment, so dust removal equipment and dust recovery equipment are needed.
Application of rotary dryer
Rotary dryer is widely used in alfalfa grass drying, alcohol dregs drying, straw drying, wood chips drying, marigold drying, shavings drying, ginkgo biloba drying, Chinese herbal medicine drying, beer dregs drying, white wine dregs drying, potato starch dregs drying, cassava dregs drying, barley malt drying, melon seeds drying, sugarcane bagasse drying, hawthorn drying, rapeseed cake drying, vegetable drying, etc., with thermal efficiency up to 80%-90%.
1. Chemical, mining, metallurgical industries, such as ore, slag, coal, metal powder, clay, diatomaceous earth, kaolin.
2. Agriculture, feed, fertilizer industry, such as straw, alfalfa, pasture, leaves, fish flour, chicken manure, corn paste, starch residue, wine lees, medicine residue, fruit residue, soy sauce residue, sugarcane residue, grass charcoal, organic compound fertilizer, sludge, aquatic waste, food factory waste, slaughterhouse waste, organic fertilizer, inorganic fertilizer, phosphorus fertilizer and ammonium sulfate.
3. Drying of powder and granular materials with special requirements. Such as various crystals, light calcium carbonate, active white clay, magnetic powder, graphite, inorganic slurry, clay, lime slurry, ore slurry, phosphate slag, aluminum plant red mud.
Sawdust rotary dryer: three cylinder
(wood chips dryer)
Sawdust rotary dryer is widely used to dry humidity granularity materials in the biomass industries. Sawdust and wood chips should be dried to 5-10% water content to meet the demands for pelletizer. It is diferent from sawdust flash dryer,it specially designed for drying sawdust and wood chips with moisture content of below 55-60%.
Wood chips dryer: single cylinder
Rotary drum dryer machine by Palet Machinery is specially designed for drying the sawdust,wood shavings,wood chips,wood blocks, rice hull, chicken manure,grass,bean dredgs,cassava residue,cassava residue,sluges,etc.It is the important part of the pellet palnt, and the quality of material have an impact on pelletizing with pellet mill.