Lime Kiln Technology
Lime kiln technology is an ancient technology used to make lime. Lime kiln technology dates back to pre-history, when it was used in primitive societies to process limestone into quicklime, or calcium oxide (CaO), which could then be used for a variety of purposes such as making plaster for construction, mortar for cement and stain for paint. Lime kilns were also used to make pottery and glass, in addition to being used for various industrial purposes.
The design and construction of a lime kiln is relatively simple but must be done in accordance with certain safety guidelines. A typical lime kiln is a cylindrical structure constructed from either masonry or steel, approximately 8-12 feet in diameter and 20-30 feet in length. A firebox is constructed in the center of the kiln and is where the fuel is burned to heat the limestone. The fuel can be either charbroil, wood, coal or oil. The limestone is usually charged into the kiln through an opening at the top of the kiln and is then heated to temperatures between 800 to 1000 degrees Celsius. The heat of the fuel is transferred to the limestone by the flame and intense heat of the firebox. As the limestone passes down the kiln it gradually combines with the fuel’s heat and converts into quicklime.
The temperature in a lime kiln must be carefully monitored and adjusted to ensure the correct chemical reaction between the limestone and the fuel. The exact temperature is dependent on the particular fuel used and the composition of the limestone. Too low a temperature can lead to incomplete conversion of limestone to quicklime, while too high a temperature can lead to an over-conversion of quicklime and an undesirable residue. To increase or decrease the temperature, the amount of fuel can be adjusted or the air supply to the firebox can be increased or decreased.
Once the correct temperature is achieved, the quicklime is removed from the bottom of the kiln, while the unloaded limestone is placed in the top of the kiln. The quicklime is then cooled and bagged for sale or can be used straight away for various purposes.
Lime kilns are still in use today, both for commercial and industrial production, as well as for very small scale operations. It is an effective and efficient method of processing limestone into a form useful for many different applications and provides a low-cost production method for quicklime.
