Rotary Dryer

A rotary dryer is a large-scale industrial drying device using continuous, indirect or direct heating. The main body of a rotary dryer is a cylindrical drum that rotates at an angle (usually at a 3°-5° angle to the horizontal).

The rotation of the drum causes the wet material to move from the feed end to the discharge end under the action of gravity, while simultaneously coming into contact with the hot air flow (or heat transfer wall), achieving heat exchange and moisture evaporation.

Rotary dryers offer a wide range of applications, are easy to operate, and have high operational efficiency. They are widely used in the cement industry to dry raw materials and fuels such as clay, slag, gravel, and coal. During drying, hot air or flue gas transfers heat to the material, evaporating moisture. Ventilation also continuously renews the drying medium within the dryer to remove moisture.

What is a rotary dryer?

A rotary dryer is a large-scale industrial drying device with a low-speed rotating cylindrical drum as its core, using continuous, indirect or direct heating. By continuously turning and conveying wet materials, the dryer creates a co-current or counter-current heat and mass exchange with a heat medium (hot air, flue gas, steam, etc.), thereby reducing the material’s moisture content to the target value.

Rotary dryer definition: It combines conveying, turning, heat transfer, and mass transfer, making it one of the most commonly used large-scale industrial drying equipment for granular, bulk, and filter cake-like materials.

rotary dryer machine

Processing capacity: 1–200 t·h⁻¹ .
Inlet temperature: 300–950°C (direct heating), 120–250°C (steam bundle).
Outlet moisture content: 0.5–5% (adjustable).
Thermal efficiency: 55–75% (direct heating), ≥80% (steam bundle).
Particle size adaptability: 0.075–50 mm;

Rotary dryer specification

Model	Shell cubage (m³)	Capacity (t/h)	Installation obliquity(%)	Highest inlet air temperature	Main motor (kw)	Weight (t)
Ø1.2×8	9	1.9-2.4	3-5	700-800	7.5	9
Ø1.2×10	11.3	2.4-3	3-5	700-800	7.5	11
Ø1.5×12	21.2	4.5-5.7	3-5	700-800	15	18.5
Ø1.5×14	24.7	5.3-6.6	3-5	700-800	15	19.7
Ø1.5×15	26.5	5.7-7.1	3-5	700-800	15	20.5
Ø1.8×12	30.5	6.5-8.1	3-5	700-800	18.5	21.5
Ø1.8×14	35.6	7.6-9.5	3-5	700-800	18.5	23
Ø22×12	45.6	9.7-12.2	3-5	700-800	22	33.5
Ø2.2×14	53.2	11.4-14.2	3-5	700-800	22	36
Ø2.2×16	60.8	13-16.2	3-5	700-800	22	38
Ø2.4×14	63.3	13.5-16.9	3-5	700-800	37	45
Ø2.4×18	81.4	17.4-21.7	3-5	700-800	37	49
Ø2.4×20	90.4	19.3-24.1	3-5	700-800	45	54
Ø2.4×22	99.5	21.2-26.5	3-5	700-800	45	58
Ø2.6×24	127.4	27.2-34	3-5	700-800	55	73
Ø3×20	141.3	30.1-37.7	3-5	700-800	75	85
Ø3×25	176.6	37.7-47.1	3-5	700-800	75	95
Ø3.2×25	201	42.9-53.6	3-5	700-800	90	110
Ø3.6×28	285	60.8-76	3-5	700-800	160	135

How does a rotary dryer work?

During operation, the material and the hot air flow flow into the small end of the inner cone. The material is lifted by the lifting plate, undergoing a thorough heat exchange with the hot air flow, and then moves toward the large end.

How to feed powder in a rotary dryer? After entering the outer drum, the material is lifted by the scoop-shaped lifting plates and evenly distributed over the upper portion of the inner conical drum’s outer wall. As the drum slowly rotates, the material experiences a long retention time in the annular space before flowing along the drum wall and guide plates on the inner drum’s outer wall to the outlet, where it is discharged through a flap valve. The exhaust gas is collected by a cyclone dust collector on the discharge hood and then discharged.

Rotary Dryer Operating Principle (Four-Step Cycle)

Feed	Wet material enters the upper (or lower, depending on flow direction) end of the drum through a feeder.
Turning	The drum rotates slowly at 1–8 rpm, and internal lifters repeatedly lift and drop the material, forming a uniform curtain and increasing the heat exchange area.
Heat Transfer	Heat medium is introduced from a burner, waste heat boiler, or steam heat exchanger, and comes into direct contact with the material (convection) or indirectly through the drum wall (indirect transfer), vaporizing the moisture.
Discharge	The dried material is discharged from the lower end; dust-laden gases are discharged through a two-stage cyclone and bag filter system; condensate/exhaust gas is recovered or purified.

What are the features of a rotary dryer?

Components	Functional Description
Drum	Steel drum (optionally equipped with a lift plate), lengths ranging from 3-30 meters, diameters from 1-4 meters, high-temperature resistant (typically ≤ 800°C)
Lift plate	Lifts material to increase heat contact area (e.g., L-shaped, lift-type, fan-shaped)
Drive System	Gear motor + roller assembly, adjustable speed (2-10 RPM)
Heat Source	Can be heated by gas, oil, steam, or electricity, with hot air temperatures ranging from 80°C to 700°C
Sealing System	Prevents heat leakage and dust escape (labyrinth type, air seal type)

Rotary dryer performance advantages

High Processing Capacity: A single unit can process over 500 tons of material daily (e.g., ore sand and biomass pellets).

Adaptability: Can dry highly viscous, high-moisture, granular, or lumpy materials (moisture content reduced from 40% to <1%).

Energy-Efficient Design: Thermal Efficiency 60%-75% (over 85% for models with waste heat recovery systems).

Continuous Operation: 24/7 operation with automated control (connected to temperature and humidity sensors).

Low Maintenance: Simple structure and wear-resistant treatment of key components (e.g., welded wear-resistant coating on the lift plate).

What are rotary dryers used for?

Rotary dryer applications and materials

Industry	Typical Drying Materials	Drying Targets
Mining and Building Materials	Quartz sand, manufactured sand, tailings, clay, bentonite	Moisture content ≤ 0.5%, meeting construction/foundry sand standards
Chemical Industry	Fertilizers (ammonium phosphate, compound fertilizers), PVC resins, salt crystallization	Anti-caking treatment to improve fluidity
Metallurgy	Nickel ore/bauxite powder, metal concentrates, metallurgical waste	Pretreatment and smelting to reduce smelting energy consumption
Environmental Protection and Solid Waste	Sewage sludge (municipal/industrial), biomass pellets, pharmaceutical residues	Reduction treatment (moisture content 80% → 10%) to facilitate incineration/composting
Agriculture	Feed pellets, distiller’s grains, cassava residue, straw	Extend storage life and improve feed nutrient utilization
Food	Soy protein, yeast, fruit and vegetable residues (indirect heating type)	Low-temperature drying (<120°C) to preserve active ingredients

SMAT Rotary Dryer Solutions

Precision Drying · Intelligent Energy Saving · Global Commitment

Customized Drying System Design

0.5% Moisture Control: AI-Based Thermal Simulation of Target Materials (Sand/Minerals/Sludge)

Three-in-One Solution:

Optimized Drum Size + Heat Source Selection (Gas/Steam/Electric) + Emission Control

High-Performance Manufacturing

Patented Lifter and Sealing System, ≥85% Thermal Efficiency

Double Lifespan

12mm Thickened Drum + Ceramic-Coated Lifter (Wear-Resistant)

Quality Assurance

Real-Time Weld Monitoring / 72-Hour Pre-Delivery Trial Run