Rotary kilns (also known as rotary calciners) are used to heat solids to a predetermined temperature in order to create a chemical and/or physical reaction. The two basic types of rotary kilns – direct fired and indirect fired (calciners) – can be found supporting processes in mineral, agriculture, and other material processing industries.
Common Rotary Kiln Applications
The following examples highlight common rotary kiln or rotary calciner applications and the benefits created as a result of this specialized method of thermal processing.
1. Commodity Materials
Many traditional commodity materials, such as agricultural products or raw minerals, benefit from the use of a rotary kiln as part of the manufacturing process. The following examples require rotary kilns to successfully process material into a viable consumer product.
Example 1: Cement
A cement plant uses a rotary kiln, also referred to as a cement kiln or rotary cement kiln, to heat raw material into a product commonly referred to as ‘clinker.’ While the types of cement kilns have changed and evolved over the years, modern cement processing typically uses a continuous direct fired kiln to thermally process material. While wet processing does occur, a dry process is commonly used, because it eliminates water evaporation considerations and transfers heat more efficiently. When processing cement, the goal of a rotary kiln is to produce clinker at a maximum rate, while maintaining low operating costs. The use of a rotary kiln allows for continuous production of large quantities of cement while maintaining a high-quality, uniform product.
Example 2: Gypsum
Kettle calciners or flash calciners are used to remove chemically bound water from finely ground gypsum. The kettle calciners indirectly heat gypsum, while flash calciners use direct heat to process the material. Both types of calciners, also referred to as gypsum calciners or rotary calciners, are commonly used to create stucco.
2. Custom Rotary Kiln Applications
FEECO is an industry leader and innovative solutions provider in the field of custom thermal processing. In addition to providing traditional rotary kiln solutions, FEECO is able to determine if an unconventional process is feasible and has the resources capable of providing customized, original solutions. While custom thermal processing applications occur in many different fields, common uses typically involve metal recovery, waste processing, and oxidation applications.
Example 1: Reclaiming Nickel
As an alternative to sending electronics to the trash, FEECO partnered with a large natural resource company to reclaim nickel from nickel-bearing electronic waste. By using rotary kilns to generate high processing temperatures, FEECO created an innovative recycling method that eliminated unnecessary organic material while recovering valuable minerals. The customer was able to reclaim nickel from waste materials, prevent toxic materials from entering the environment, and promote a sustainable and profitable material solution.
Example 2: Hydraulic Fracturing Proppants
A proppant is a material used in hydraulic fracturing to support (i.e. ‘prop open’) the opening of a fracture. It is typically composed of treated sand or man-made ceramic. Proppant manufacturers use the rotating motion and high temperatures within rotary kilns to sinter proppant powder and form uniform ceramic beads. Because high temperatures are necessary to properly calcine and harden ceramic proppants, the rotary kilns used to manufacture proppants are often refractory lined
Testing the Feasibility of Custom Rotary Kiln Applications
The design and operation of a rotary kiln are critical to its efficiency. If designed incorrectly or operated improperly, a rotary kiln will inadequately treat materials and drastically increase operating costs. FEECO’s testing and tolling facilities are available to help customers efficiently optimize their material and create the best thermal process design possible. Whether it’s calcining mined minerals or creating a waste-to-value solution, FEECO has the experience and testing knowledge base to answer thermal processing questions and assist customers in making informed decisions about their material.
In addition to the wide variety of thermal processing equipment available for feasibility testing, FEECO recently welcomed a continuous indirect fired kiln to their lab. The new equipment addition expands the lab’s testing capabilities to include a higher and more continuous testing capacity. Customers will benefit from this expanded testing ability because the continuous indirect fired kiln serves as a way to define the feasibility of applications for commercial transition, further verifying processing designs for large scale operations.
For more information on rotary kiln applications and thermal processing feasibility testing, contact FEECO today!
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