Calcination refers to a thermal treatment process applied to ores and other solid materials in the absence of oxygen or air. Calcination is one of the important methods used for the extraction of metals in metallurgy. This process is carried out in a controlled environment with a regulated temperature. The calcination method generally removes moisture from compounds.
In this article, we are going to discuss the Calcination process, Calcination definition, Calcination formula, Calcination example, the difference between calcination and roasting, and a few applications of calcination.
What is Calcination?
Calcination also known as calcining is a process of heating a solid compound at a very high temperature below its melting point. This process is carried out in the absence of oxygen or a limited supply of oxygen. The process involves heating a substance to high temperatures, typically between 700 ℃ to 1200 ℃, although the specific temperature can vary based on the melting point of the material and the desired outcome.
In some cases, calcination of a metal results in oxidation of the metal. In the calcination process, a substance is heated below its melting or fusion point. During this process, the moisture is removed (i.e. water from ore is removed leaving the metal oxide behind).
In many industrial processes, calcination is a necessary step that changes the chemical and physical characteristics of materials for a range of uses. In the metal carbonates, the calcination process is carried out to turn metal carbonates into carbon dioxides and metal oxides.
Calcination Definition
Calcination is the process of heating a solid compound at a very high temperature in absence of oxygen or a limited supply of oxygen at controlled atmospheric pressure.
Calcination in other words also called as purification because it is used for the extraction of metals from its ore. In other words, we can say that Calcination is the process of heating ore to a high enough temperature to turn it into an oxide. Either in the absence of air or with insufficient supply, the ore is heated below its melting point.
Calcination Formula
Calcination is the process of heating a material to high temperatures, frequently without or with restricted air or oxygen supply. This causes the material to undergo chemical and physical changes. Although a universal “calcination formula” does not exist, the overall idea can be expressed by a simpler equation. The formula for calcined gypsum can be given as:
CaSO4.0.5 H2O
Calcination Example
Examples of Calcination include:
- Calcination of Limestone (Calcium Carbonate)
- Calcination of Gypsum (Calcium Sulfate Dihydrate)
- Calcination of Aluminum Hydroxide
- Calcination of Magnesium Carbonate
- Calcination of Kaolin (Clay Mineral), etc.
Calcination process is also used in the manufacture of quick lime from limestone. The ore is disposed of moisture, organic content, and volatile contaminants including sulfur dioxide and carbon dioxide. It increases porousness. Carbon dioxide and metal oxides are produced during the breakdown of carbonate ores.
Calcination Process
Calcination Process is carried out by heating a chemical compound at a very high temperature without melting it. It is performed under very little supply of oxygen. There are several steps performed during calcination process. These steps are:
- Preparation
- Heating
- Chemical Reaction and
- Cooling
Preparation
The material is crushed and grinded into small particles from large solid ores. These small particles will enhance the efficiency of the calcination process.
Heating
After that, the material is heated to high temperatures in a regulated setting. The material and the intended result determine the precise temperature and heating time. For instance, calcium carbonate is heated to temperatures more than 800 degrees Celsius.
Chemical Reaction
After heating the material the chemical reaction is performed with a limited supply of oxygen. The chemical reaction removes water from the material and yields its oxide. Carbonates and other compounds decompose, lose moisture, and undergo oxidation or reduction when a substance is heated below its melting points at a high temperature.
Cooling
After the desired chemical changes have taken place, the material is allowed to cool down. The cooling process may be slow to avoid undesired reactions or changes.
Calcination Reactions
Calcination reactions occur due to the heating of a substance at a very high temperature in a limited supply of oxygen. These reactions result in physical and chemical changes in the material, often leading to the removal of volatile components, decomposition of compounds, or other transformations.
Some substances that show Calcination reactions are Limestone (Calcium Carbonate), Gypsum (Calcium Sulfate Dihydrate), Calcination of Aluminum Hydroxide, Calcination of Magnesium Carbonate, etc.
Few of the Calcination Reactions are explained below:
Calcination of Gypsum
The chemical formula of gypsum is CaSO4․2H2O. Gypsum is known as calcium sulfate dihydrate due to the presence of two molecules of water. When gypsum is subjected to calcination then it produces calcium sulfate hemihydrate, well known as plaster of Paris (P.O.P.). The formula of plaster of Paris is CaSO4.1/2H2O. The Calcination reaction of gypsum can be given as
CaSO4.2H2O → CaSO4.1/2H2O + 3/2H2O
Read More, Plaster of Paris
Calcination of Limestone
Calcination process is used for the extraction of many metals from its ores. Although there are many examples of the calcination process. Calcination of limestone (CaCO3) is one of the most famous examples of the calcination process. When limestone is heated at 848o C, it decomposes into calcium oxide and carbon dioxide.
CaCO3 → CaO + CO2(g)
Read More, Calcium Carbonate
Difference Between Calcination and Roasting
The key difference between Roasting and Calcination is given below:
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When a material is heated in a limited supply of oxygen then it is known as the calcination process.
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When a material is heated with an excess amount of oxygen then this process is known as roasting.
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In the calcination process, the removal of water takes place.
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In the roasting process, the removal of water does not take place.
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Carbon dioxide is emitted during the reaction.
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Sulfur Dioxide is released during this reaction.
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Read More, Calcination VS Roasting
Applications of Calcination
Calcination has a wide range of uses, a few of which are described below:
- Calcination is used in the production of quick lime from limestone.
- Calcination process is used in the preparation of different types of catalysts.
- This process is used for the removal of water or any other volatile component from different substances.
- Calcination process is used in the treatment of various hazardous wastes.
- Calcination process is used in the production of various oxides from their carbonate ore.
- Calcination reaction is used in the purification of various metals from their ores.
Read More,
Calcination: Frequently Asked Questions
What is Calcination and Roasting?
Calcination is the process of heating the ore of the metal in limited supply of oxygen while roasting is the process of heating the ore of metal in presence of excess supply of oxygen.
Name Two Metals which gets Oxidized during the Calcination Process.
Lead and Tin are the two metals which gets oxidized during calcination process.
What is Heat of Calcination?
The amount of heat energy required to perform the calcination process on a specific substance is known as heat of Calcination.
Is Calcination Exothermic or Endothermic?
Calcination requires heat to evaporate moisture or break down chemical compounds, hence it is an endothermic process.
What is Calcination Temperature?
The calcination temperature for any substance is the temperature at which calcination process for that substance takes place.
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