Rotary Kilns

DIRECT-FIRED ROTARY KILNS

FEECO is a leading manufacturer of highly engineered, custom rotary kilns for processing solids. Our high-temperature kilns have earned a reputation for their durability, efficiency, and longevity. We offer both direct- and indirect-fired units.

Rotary kilns work by processing material in a rotating drum at high temperatures for a specified retention time to cause a physical change or chemical reaction in the material being processed. The kiln is set at a slight slope to assist in moving material through the drum.

Direct-fired kilns utilize direct contact between the material and process gas to efficiently process the material. Combustion can occur in a combustion chamber to avoid direct flame radiation, or the flame can be directed down the length of the kiln.

Direct-fired kilns can be of the co-current or counter-current configuration, referring to the direction the combustion gases flow in relation to the material.

FEATURES

• Size: Up to 15′ diameter x 100’+ long (Up to 4.6m dia. x 30.5m+ long)
• Capacity: 1 TPH – 50 TPH (1 MTPH – 45 MTPH); maximum capacity is dependent on process variables unique to each application
• Parallel or counter-current flow
• Optimized Refractory Lining Solutions (multiple layers, castable, brick)
• Engineered shell to eliminate distortion and misalignment due to high operating temperatures
• Various Drive Assemblies Available

In addition to the rotary kiln itself, FEECO can supply a complete system with services, including:

DIRECT-FIRED ROTARY KILN COMPONENTS AND PARTS

The image below shows the standard components of a direct-fired rotary kiln. Click image to view larger.

Mechanical Construction of a Rotary Kiln (3D Rotary Kiln by FEECO International)

INDIRECT-FIRED ROTARY KILNS

Indirect-fired kilns are used for various processing applications, such as when processing must occur in an inert environment, when working with finely divided solids, or when the processing environment must be tightly controlled.

An indirect-fired kiln is enclosed in a furnace, which is then externally heated. This avoids contact between the combustion gases and the material being processed.

FEATURES

• Size: Up to 15′ diameter x 75’+ heated length (up to 4.6m dia. x 23m+ heated length) maximum capacity is dependent on process variables unique to each application
• Capacity: 200 lb/hr – 20 TPH (91kg/hr – 18 MTPH)
• Heat resistant alloy shell
• Engineered shell to eliminate distortion and misalignment due to high operating temperatures
• Separate zones for temperature control
• Integrated cooling zone can be added
• Various Drive Assemblies Available

INDIRECT-FIRED ROTARY KILN COMPONENTS AND PARTS

The image below shows the standard components of an indirect-fired rotary kiln. Click image to view larger.

Mechanical Construction of an Indirect Rotary Kiln (3D Indirect Rotary Kiln by FEECO International)

APPLICATIONS & MATERIALS

Rotary kilns are versatile thermal processing machines capable of processing a wide variety of materials. Common applications are for both direct-fired kilns and indirect-fired kilns are listed below.

CALCINATION

Calcination refers to the process of heating a material to a temperature that will cause chemical dissociation (chemical separation). This process is used frequently in the creation of inorganic materials, for example, the dissociation of calcium carbonate to create calcium oxide and carbon dioxide.

THERMAL DESORPTION

Thermal desorption is also a separation process. This process uses heat to drive off a volatile component, such as a pesticide, from an inorganic mineral, such as sand. The component is vaporized at the increased temperature, causing a separation without combustion. In some cases, an indirect rotary kiln would be best for this application, because the volatile chemicals may be combustible. The indirect kiln will supply the heat for desorption, without the material coming into direct contact with the flame.

ORGANIC COMBUSTION

Organic combustion refers to the treatment of organic wastes with the intent of reducing mass and volume. Organic waste is treated in the kiln, leaving behind an ash with considerably less mass and volume. This allows for more efficient and effective deposit of waste materials into landfills.

HEAT SETTING

Heat setting involves bonding a heat resistant core mineral with another, less heat resistant coating material. Unlike an unheated coating process, here, a rotary kiln heats the coating material to just below liquefaction point, allowing it to coat the heat resistant core more evenly and more securely. This process is commonly seen in the manufacture of roofing granules, where a mineral such as granite is coated with a colored pigment, producing a product that is both durable and aesthetically pleasing.

REDUCTION ROASTING

Reduction roasting is the removal of oxygen from a component of an ore usually by using carbon monoxide (CO). The CO is typically supplied by mixing a carbonaceous material such as coal or coke with the ore or by feeding it separately. Examples are the reduction roasting of a hematite containing material to produce magnetite that can be magnetically separated. In the Waelz process, zinc oxide in steel mill wastes is reduced to metallic zinc and volatilized for recovery in the off-gas system.

Some of the most common materials for which rotary kilns are employed include: