Overview of Rotary Drum Drying Machine Equipment
The rotary drum dryer is a cylindrical body with a slightly inclined main body and adjustable speed within a certain range. Wet materials are fed into the cylinder by the feeder, and under the flipping of the uniformly distributed plate reader in the cylinder, the materials are evenly distributed and dispersed in the dryer, and fully contact with the hot air (parallel or reverse) passing through the cylinder, accelerating the heat and mass transfer of drying and achieving the purpose of drying. This device can use various forms of copying boards to adapt to different materials, with a simple structure, reliable operation, easy maintenance, and high production capacity.
Rotary drum dryer is a type of dryer that processes large amounts of materials. Due to its reliable operation, high operational flexibility, strong adaptability, and large processing capacity, it is widely used in metallurgy, building materials, light industry, and other sectors. In the chemical industry, rotary dryers are mostly used for drying materials such as ammonium sulfate, alkali sulfide, Anfu powder, ammonium nitrate, urea, oxalic acid, calcium carbonate, calcium magnesium phosphate fertilizer, ordinary superphosphate, heavy superphosphate, and sodium tripolyphosphate (some materials can also be dried using other types of dryers). Rotary drum dryers are generally suitable for granular materials, and can also be used to dry viscous paste materials or materials with high moisture content by partially adding dry materials. The moisture content of materials is generally 3-25%, and can reach up to 50%. The moisture content of products can reach 0.5%.

Process flow diagram of rotary drum dryer

Working principle of rotary drum dryer
Wet materials are mixed and stirred by a spiral feeder before being added to a rotating drum. Under the action of a plate, the materials are lifted up, and the heated hot air enters the kiln and quickly exchanges heat and mass with the materials. After the hot air comes into contact with the wet materials, the temperature drops rapidly, and the materials absorb heat and quickly evaporate moisture. The fine powder in the humid air is recovered by a cyclone dust collector and discharged outdoors by a dehumidification fan. The material enters the dryer from the feeding end and is discharged from the other end, working continuously. The entire process includes material preheating, water evaporation, and material heating.
This system operates under slight negative pressure, so the environment is very clean. The variable frequency speed regulation of the transmission motor can adjust the speed of the drum, effectively controlling the output and final moisture content of the product.

Rotary drum dryer is suitable for materials
The chemical, mining, metallurgical and other industries dry large particles and materials with high specific gravity, such as mining, blast furnace slag, coal, metal powder, phosphate fertilizer, and ammonium sulfate.
Drying of powders and granular materials with special requirements, such as HP foaming agent, distiller's residue, light calcium carbonate, activated clay, magnetic powder, graphite, and drug residue.
Materials that require low-temperature drying and require continuous drying in large quantities.

Performance characteristics of rotary drum dryer
The rotary dryer has a high degree of mechanization and a large production capacity.
The fluid has low resistance and low functional consumption when passing through the cylinder.
Has strong adaptability to material characteristics.
Stable operation, low operating costs, and good uniformity of product drying.

Flow direction selection and thermal carrier fluid selection for rotary dryer
1. Parallel flow: The direction of material movement is the same as the direction of heat transfer fluid flow. It is suitable for the following materials:
(1) When the moisture content of the material is high, it is allowed to dry quickly without cracking or coking.
(2) After drying, the material cannot withstand high temperatures, which means that the product will undergo decomposition, oxidation, and other changes when exposed to high temperatures.
(3) The moisture absorption of the dried material is very low, otherwise the dried material will absorb moisture back from the heat transfer fluid, reducing product quality.
2. Reverse flow: The direction of material movement is opposite to the direction of heat transfer fluid flow. It is suitable for the following materials:
(1) When the moisture content of the material is high, rapid drying is not allowed to prevent cracking of the material;
(2) The dried material can withstand high temperatures and will not undergo decomposition, oxidation, or other phenomena;
(3) The dried material has high moisture absorption;
(4) Require high drying speed while also requiring low moisture content in the product.
3. Selection of heat transfer fluid:
If the dried solid material is not afraid of high temperature and is not a post product, it is allowed for the intermediate process to be slightly contaminated. Flue gas can be used as the heat transfer fluid to achieve higher volume evaporation rate and thermal efficiency. The rotary dryer for materials such as ore, gravel, coal, and superphosphate uses flue gas, which can be coal, oil, or natural gas as fuel. If the dried material is not allowed to be contaminated, air should be used as the heat transfer fluid. Hot air is obtained by passing through a steam heat exchanger or indirectly heating a hot blast stove.

Technical specifications for rotary drum dryer

model	Direct heating downstream type	Direct heating downstream type	Direct heating counter current type	Direct heating counter current type	Composite heating	Composite heating
Material type	ore	HP foaming agent	blast furnace slag	ammonium sulfate	phosphate fertilizer	coal
Processing capacity (kg/h)	1000	466	15000	20000	12000	5000
Water content (%)	30	13	6	1.5	5	6.5
Final moisture content (%)	15	0.3	1	0.1	0.1	0.1
Average particle size (mm)	6.5	0.05	4.7	0.5-1.7	0.5	5
Material stacking density (kg/m3)	770	800	1890	1100	1500	750
Hot air volume (kg/h)	3900	5400	10750	9800	6500	16000
Inlet gas temperature（oC)	600	165	500	180	650	570
Material outlet temperature（oC)		42	100	70	80	75
Heating method	gas	Steam electric heating	heavy oil	JRF	heavy oil	heavy oil
loading coefficient		6.3	7	7.5	7.8	18
Rotational speed (rpm)	4	4	3.5	3	4	2
tilt	0.04	0.005	0.03	0.05	0.05	0.043
Number of copied boards	12	24	12	22	Outer side of inner cylinder 8 Inner cylinder outer 16	6 12
Drier diameter (m)	2.0	1.5	2	2.3	Outer tube 2 Inner cylinder 0.84	Outer tube 2.4 Inner cylinder 0.95
Drying machine length (m)	20	12	17	15	10	16
Drive power (kw)	22	7.5	15	11	11	15

On site installation photos of rotary drum dryer