Calcination Examples

This article provides a thorough understanding of what calcination is and Calcination examples. Calcination is usually carried out to remove the volatile and moisture impurities present in a metal substance, usually by heating it at high temperatures with no supply of air or oxygen. Essentially, the process helps prevent crevice corrosion due to the deposition of sand or dust or other corrosive substances that may lead to the accumulation of water on the metal surfaces. 

A few calcification examples and their in-depth explanation give a better understanding of the process. Calcination mostly is also carried out in oxidising carbonate compounds. In various furnaces such as shaft furnaces, multiple hearth furnaces, and others, calcination is used to exclude air from the furnace by substituting inert gases.

What is Calcination?

Calcination means heating a solid material or substance at high temperatures in a controlled environment with no supply of air or oxygen, usually to remove impurities or volatile substances or oxidise a portion of the mass, thereby incurring thermal decomposition. It can also be called a thermal process that converts ores and other solid materials. 

Also known as the purification process, the term ‘Calcination’ is derived from the Latin word ‘Calcinare’ which essentially means ‘to burn lime’. The most prominent use of calcination is to separate lime from limestone. The limestone is exposed to elevated temperatures, which are enough to expel carbon dioxide, causing the separation of lime in friable conditions. A more detailed explanation, along with Calcination examples, is given below. 

Calcination Reactions 

Before the article explains the calcination examples’ meaning, it is essential to study the reactions. A calcination reaction occurs at or beyond the thermal temperature of decomposition for any metal ores or temperature of transition. The given temperature occurs when the average Gibbs free energy available for any calcination reaction tends to zero.

Calcination of Limestone:

The decomposition takes place at about 900 to 1050 °C in this process. The reaction formula of the same is:

CaCO3(s) → CaO(s) + CO2(g) 

Currently, this reaction takes place at a larger scale to manufacture portland cement through cement kilns. 

Examples of Calcination:

The most common calcination examples include :

1. In limestone manufacturing, the carbon ores are decomposed with the help of calcination, which wards off the carbon dioxide. 
2. You can decompose the dehydrated minerals through the process of calcination. In the process of gypsum or bauxite calcination, one can become the water of crystallisation in the form of water vapours. 
3. The process of decomposition of any volatile element present in a raw petroleum product or coke is also one of the Calcination examples. 
4.  The ammonia ions are removed through calcination during the process of zeolite synthesis. 
5. The process of defluorination of the present uranyl fluoride to manufacture oxides of uranium and hydrofluoric acid (gaseous state)

Essentially, a typical calcination process involves the conversion of calcium carbonate to calcium oxide. Though the concept is the same, certain aspects differentiate Calcination and Roasting. The next topic will give a brief on the differences. 

Gypsum Calcination

Gypsum calcination is one of the most important Calcination Examples that can be explained. Formed as a by-product of flue gas desulphurization in a few coal-fired electric power plants, Gypsum (CaSO4.2H2O), a Calcium Mineral, is mined across various parts of the world. Gypsum Calcination similarly involves a continuous process of dehydrating gypsum into plaster which involves heating the gypsum to evaporate the crystalline water. 

Calcined Gypsum has various industrial uses like Dental Stone, Plaster of Paris, surgical splints, casting moulds, and modelling, utilising the property of coagulation and used in major industries such as Building Construction, Pharmaceuticals, Medical Devices, Food additives, and much more. 

Conclusion

Calcination is the process through which you can remove impurities from solid metal ores. During this process, the meta is elevated to a propelled temperature, without melting but with a restricted supply of the available ambient oxygen. In simple words, calcination means introducing solid materials to elevated heat temperatures, usually below the melting point in a controlled environment with no supply of oxygen or air to remove moisture volatilities or impurities, thereby incurring thermal decomposition.