Calcination and Roasting

1. Define Calcination and Roasting.

Calcination is the process of converting ore into oxide by heating it at high temperature in the absence of air whereas Roasting is the process of converting ore into oxide by heating it at a temperature below its melting point in presence of air.

2. What is Metallurgy?

The entire scientific and technological process used for isolation of the metal from its ore is known as metallurgy.

3. What is the Purpose of Calcination?

Calcination is used for purification purpose of mainly carbonates ore. Moisture and volatile impurities are removed during calcination.

4. Why is Calcination done in the Absence of Air?

In the metal carbonates, the calcination process is carried out to turn metal carbonates into carbon dioxides and metal oxides. No reaction will occur in the presence of air hence calcination is carried out in the absence of air.

5. Which Process is Used to Convert Hydroxides into Oxides?

Calcination is used to convert hydroxides into oxides.

6. Give an Example of Calcination

Calcination is widely used in the decomposition of Calcium carbonate(limestone) to Calcium oxide(lime) and Carbon dioxide.

CaCO₃ → CaO + CO₂

7. What is Reduction Roasting?

Reduction roasting partially reduces an oxide ore before the actual smelting process.

8. Give an Example of Roasting.

Zinc sulphide is converted to zinc oxide with the help of roasting.

ZnS + 3O₂ → 2ZnO + 2SO₂

9. Why Roasting is Hazardous for Environment?

Roasting releases sulphides which are major contributor of air pollution as they have acidic and toxic metallic compounds.

10. What is Chloridising Roasting?

Chloridising roasting transforms certain metal compounds to chlorides through oxidation or reduction. Some metals such as uranium, titanium, beryllium are processed in their chloride form.

• 2NaCl + MS + 2O₂ → Na₂SO₄ + MCl
• 4NaCl + 2MO + S₂ + 3O₂ → 2Na₂SO₄ + 2MCl₂

11. Differentiate between Calcination and Roasting.

Calcination is the process of heating a substance without air to remove volatiles or change its structure. Roasting, on the other hand, involves heating in the presence of air to remove impurities or alter the material’s composition, typically used in metallurgy.

Calcination and Roasting are two processes of refining carbonate and sulfide metal ores respectively into pure metal forms. Minerals are naturally occurring chemical substances in the Earth’s crust that are obtained by mining. Metals that are known to us are derived from some of these minerals and such minerals are known as ores.

The science that deals with extracting metals from ores is known as metallurgy. There are many ways by which metals are extracted from its ore and one such process to extract crude metal from its concentrated ore is conversion to oxide which is further divided into Calcination and Roasting. In this article, we briefly discuss calcination and roasting and the difference between calcination and roasting.