How does calcining work?

Calcining is a thermal treatment process that uses very high temperatures to change the physical and chemical properties of various materials.


Calcining - also known as calcination - is a thermal treatment process that uses extremely high temperatures to change the physical and chemical properties of various solid materials, including minerals, metals, and ore. Calcining is used in a variety of industrial applications within the mineral processing, recycling, and manufacturing industries. The process is frequently used to improve electrical conductivity, and to remove chemically bound water and other impurities.

Many calcining processes include additional equipment after a chemical, mineral, or ore passes through the rotary kiln. While not necessary, calciners can be accompanied by a cooling system, designed to quickly cool a material down from the high temperatures experienced during the process, making it easy to quickly package and distribute the end feed for re-use.

Some examples of calcining applications include:

  • The removal of water from alumina at temperatures ranging well above 2,000°F. Removing water from alumina makes it possible to manufacture catalysts.
  • The removal of water from kaolin, from which calcined kaolin can be used in the production of paper and other similar processes.
  • Volatiles can be removed from spent activated carbon, allowing the reactivated carbon to be recycled back to absorption columns with the gold mining industry.
Other Materials That Can be Processed
  • Raw Petroleum Coke

    Raw petroleum coke, often referred to as "green", is processed in rotary kilns at temperatures ranging well above 2,000°F. This processed petroleum coke is used in the production of aluminum.

  • Bauxite & Gypsum

    Bauxite, gypsum, and many other minerals can be decomposed using calcination in order to remove crystalline water from the material, creating water vapor that can be disposed of easily.

  • Limestone

    Calcium carbonate (limestone) can be decomposed into calcium oxide (lime) through the calcining process, allowing for its use in cement production.

What's Next?
Learn More About Mercury Removal from Fines

While calcining is often used to treat feed stock within the mining and minerals industry, calcination can also be used to remove highly volatile contaminants, such as mercury, from fines. Mercury removal is one great example of how Vulcan® technology is unique in the industry. Our equipment is able to remove mercury and other contaminants safely from materials, allowing for safe re-utilization of the original feed in an appropriate setting.

Schedule a Test in Our Pilot Testing Facility

Concerned about the feasability of your calcining process? Schedule a test in our pilot testing facility where we will provide you with exceptional customer service, extensive experience, product ingenuity, and engineered solutions to help you find the perfect process for your material. Our testing center contains two units, one direct-fired and one indirect-fired, assuring you multiple options to garner your desired results.

Contact One of Our Technical Sales Engineers

Ready to start working on the specifics for your very own calcining system? Our Vulcan® Technical Sales Engineers are available to discuss your project with you and determine the best course of action moving forward. Our team has decades of combined experience working with systems designed to thermally process solid materials for re-use.

Learn More

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