rotary furnace

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Mining Machinery Admin 2025-07-14 10:24:44 130

Rotary furnace is a thermal equipment with a rotating cylindrical furnace body, widely used in various industrial fields such as metallurgy, chemical industry, building materials, environmental protection, etc. It is mainly used for material roasting, calcination, drying, reduction, oxidation and other heat treatment processes. The following provides a detailed introduction from the aspects of working principle, structural composition, classification, application fields, and characteristics:

1、 Working principle
The core working principle of a rotary furnace is to achieve uniform heating and processing of materials through the synergistic effect of the rotation of the furnace body and internal heating devices.

The furnace body is usually inclined at a certain angle (usually 3 °~5 °) and rotates at low speed (usually 0.5~5 r/min).
The material enters from the high end of the furnace body, and as the furnace body rotates, it slowly moves along the axis of the furnace body towards the low end under the action of gravity and friction. During the process, it fully contacts with the high-temperature gas (or electric heating element) inside the furnace, completing heating, reaction or physical state change (such as drying, melting, decomposition, etc.).
The main heating methods include fuel combustion heating (such as coal gas, natural gas, coal powder, etc., where heat is transferred to the material through flames or flue gas) and electric heating (directly heating the material through elements such as resistance wires and silicon carbon rods).
2、 Structural composition
The structure of a rotary furnace usually includes the following key parts:

Furnace body: a cylindrical body made of rolled and welded steel plates, lined with refractory materials (such as fire-resistant bricks and refractory castables) to withstand high temperatures and reduce heat loss. Some furnace bodies may also be equipped with cutting plates (lifting material blades) according to demand to enhance material flipping and heat exchange efficiency.
Supporting device: including a supporting wheel group and a blocking wheel group. The supporting wheel supports the weight of the furnace body and rotates with it, while the blocking wheel restricts the axial movement of the furnace body.
Transmission device: composed of a motor, a reducer, and gears (or supporting wheel friction transmission), it drives the furnace body to rotate at a set speed.
Heating device:
Fuel heating type: including burners, combustion chambers, flues, chimneys, etc., where fuel burns at the furnace head or inside the furnace to produce high-temperature flue gas.
Electric heating type: Electric heating elements are installed outside or inside the furnace body to heat materials through radiation or conduction.
Feeding and discharging device: The feeding port (usually a chute or spiral feeder) is located at the high end of the furnace body, and the discharging port is located at the low end. Some equipment will be equipped with sealing devices to prevent smoke leakage or air from entering.
Control system: Through temperature sensors, speed regulators, feed rate controllers, etc., precise control of temperature, speed, and material flow inside the furnace is achieved.
3、 Classification
According to different classification criteria, rotary furnaces can be divided into multiple types:

By heating method:
Flame heating rotary furnace (fuel type): using coal, oil, and gas as fuels, with low cost, suitable for large-scale industrial production (such as metallurgy and cement calcination).
Electric heating rotary furnace: uniform heating, precise temperature control, low pollution, but high energy consumption, suitable for precision heat treatment (such as laboratory small equipment, special material processing).
By purpose:
Metallurgical rotary furnace: used for roasting metal ores (such as reduction of hematite, desulfurization of non-ferrous metal sulfide ores), and reduction of metal oxides (such as production of sponge iron).
Chemical rotary furnace: used for calcination of chemical raw materials (such as soda ash calcination), catalyst preparation, waste decomposition, etc.
Building materials rotary furnace: The most typical is the cement rotary kiln, used for calcining cement clinker; In addition, there is a lime rotary furnace (which calcines limestone to produce quicklime).
Environmentally friendly rotary furnace: used for incineration treatment of hazardous waste (such as medical waste and industrial waste), achieving reduction and harmlessness by decomposing harmful substances at high temperatures.
According to the atmosphere inside the furnace:
Oxidation atmosphere rotary furnace: Air or oxygen is introduced into the furnace for the oxidation reaction of materials (such as roasting sulfide ore to generate oxides).
Reduction atmosphere rotary furnace: introducing reducing gases such as hydrogen and carbon monoxide for the reduction reaction of materials (such as the reduction of metal oxides to metal elements).
Inert atmosphere rotary furnace: Introduce inert gases such as nitrogen and argon to prevent material oxidation, suitable for the treatment of easily oxidizable materials.
4、 Application Fields
Metallurgical industry:
Ferrous metals: magnetization roasting of iron ore, oxidation pellet roasting of iron concentrate.
Nonferrous metals: zinc concentrate roasting desulfurization, nickel ore reduction roasting, bauxite roasting desilication, etc.
Building materials industry:
Cement production: The cement rotary kiln is the core equipment that calcines raw materials (limestone, clay, etc.) into mature materials.
Lime production: Calcination of limestone (CaCO3) produces quicklime (CaO).
Chemical industry:
Soda ash (Na ₂ CO ∝) calcination, phosphate calcination, catalyst support calcination, etc.
In the field of environmental protection:
Hazardous waste incineration: processing medical waste, waste plastics, waste oil, etc., and damaging harmful substances at high temperatures (800-1200 ℃).
Thermal decomposition and gasification of garbage derived fuel (RDF).
Other fields:
Agriculture: High temperature composting and sterilization of organic fertilizers.
New materials: ceramic powder calcination, rare earth material calcination, etc.
5、 Main features
advantage:
Large material handling capacity, suitable for continuous industrial production.
The materials in the furnace are mixed evenly, heated thoroughly, and the product quality is stable.
Strong adaptability, capable of handling various forms of materials such as solid particles, powders, and blocks, and able to adapt to different temperatures (from room temperature to above 1800 ℃) and atmosphere requirements.
Disadvantages:
The equipment has a large volume, occupies a wide area, and requires a high initial investment.
Low thermal efficiency (generally 30%~60%) and high energy consumption.
The furnace body and lining are prone to wear and tear, resulting in high maintenance costs, especially when dealing with high hardness or corrosive materials.
6、 Typical Equipment Examples
Cement rotary kiln: It is the "heart" of cement production, with a length to diameter ratio of usually 15-30 and a furnace temperature of up to 1450 ℃. The raw materials are dried, preheated, decomposed, calcined, and cooled in the kiln, ultimately producing cement clinker.
Metallurgical rotary furnace: such as zinc roasting rotary furnace, the temperature inside the furnace is controlled at 850~950 ℃, and zinc concentrate (ZnS) is roasted into zinc oxide (ZnO) while removing sulfur elements (generating SO ₂ for acid production).