Rotary Drum Dryer

The wet material enters the drum from the feeding device and exchanges heat with the drying medium in the drum (mainly in the way of conduction and convection). The drum is normally equipped with lifting plates to make the material fall after being picked up. During the drying process, due to the action of gravity, the material will move from the higher end to the lower end of the drum, and finally reach the lower part of the other end and output from there.

According to the flow direction of materials and hot air, the drum dryer can be divided into two drying methods: co-curnter flow and counterflow.

Co-current flow rotary drum dryers are the most widely used and are particularly suitable for drying materials containing a high moisture content. Due to the large temperature difference between the raw material and the hot air, the heat transfer speed is fast at the beginning, the heat transferred to the material is large, and the rapid drying is rapid, so the evaporation of water is also large. As the material and the flue gas continue to move, the moisture in the material decreases, the temperature rises, the water content in the flue gas increases, the temperature decreases, the temperature difference between the two gradually decreases, the heat transfer per unit time is gradually reduced, and the residual moisture contained in the material reaches the discharge end. This dryer is suitable for drying materials with high initial moisture and technical requirements for drying temperature.

Examples: filter cakes, minerals, fertilisers, beet pulp, de-greased bone, floatation concentrates, coal/coke, clays, phosphates, animal feeds, germ, stillage, sludges.

Counterflow rotary drum dryer is characterized by the opposite direction of the flow of the material in the cylinder to the flue gas. At the feeding end (the high end of the dum), the wet material with a lot of moisture and low temperature meets the flue gas with a lot of moisture and a low temperature that is about to be discharged into the dryer. At the discharge end (the low end of the drum), the dried material that has been dried and the temperature has risen is in contact with the hot flue gas of the dryer that has just entered the dryer. Therefore, the temperature difference between the material and the flue gas at each point in the whole cylinder is relatively uniform, and the heat transfer efficiency is relatively high. In the drying process, the drying speed is more uniform, and the heat and mass transfer are more balanced, avoiding the situation of hard drying surface. Compared with the co-current flow type, the drying time is longer, and the residual moisture of the material is small. It is suitable for drying materials with too much moisture at the input and less residual moisture.

Examples: silica gel, sugar, chemical salts and crystalline products (low temperature range) ammonium nitrate, ores and minerals, pigments, removal of floatation reagents.

• It is suitable for a wide range of applications, and it can be used to dry granular substances, also very much suitable of highly viscous, pasty, slurries type of materials.
• Rotary drum dryers are suitable drying of heat sensitive materials for its shorter drying time.
• Highly adjustable, the components of the drum dryer such as pressure, rotation speed, applicator width and other can be adjusted individually.
• Drum dryers offers higher thermal efficiency as compared to other drying systems as the drying takes place due to transfer of heat from within drum to outside drum.
• Flexible with wide range of size and heat transfer to handle wide range of material.
• Rotary dryer operates in continuous drying mode and with large production capacity.
• Simple structure and easy operation.
• The operation flexibility is large, and the output of the product is allowed to fluctuate greatly, which does not affect the quality of the product.
• Easy to maintain and clean.