A lime kiln is a device used to produce quicklime by the calcination of limestone (calcium carbonate). Here's a general overview of how it works:
Loading the Kiln: Limestone is loaded into the kiln from the top. kilns can be operated continuously or in batches.
Heating: The limestone is heated to a high temperature (typically around 900-1000°C) using a fuel source, which can be coal, oil, gas, wood, or even waste materials. The heat causes the chemical decomposition of limestone, known as calcination.
Calcination Reaction: The primary chemical reaction in a lime kiln involves the endothermic reaction where calcium carbonate (CaCO₃) is converted into calcium oxide (CaO, lime) and carbon dioxide (CO₂):
\[ \text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g) \]
The carbon dioxide is released as a gas and vented out of the kiln.
Collection of Lime: As the limestone breaks down into quicklime, it forms in a lower part of the kiln. Depending on the design of the kiln, this can be collected continuously or after a batch process.
Cooling: The produced quicklime is then cooled before handling. This can involve air coolers or water sprays.
Removal and Storage: The quicklime is removed from the kiln, usually at the bottom, and stored for use in various industrial processes, such as in the production of steel, in environmental applications like flue gas desulfurization, or in the manufacturing of construction materials.
Depending on the construction, kilns can be either:
This process ensures an efficient transformation of limestone to quicklime, optimizing for fuel consumption, temperature control, and the quality of the lime produced.
