Previous Year Question
In India, the steel production industry requires the import of
saltpetre
rock phosphate
coking coal
All of the above
Correct Answer: C
Detailed Solution
India’s integrated steel industry mainly imports high-quality coking coal. It is also known as metallurgical coal.
Why is coking coal required?
Coking coal is heated in coke ovens in the absence of air to produce coke.
Coke performs three principal functions in a blast furnace:
Its combustion produces the required high temperature.
The carbon monoxide formed from it helps reduce iron oxides to metallic iron.
Strong coke supports the burden of iron ore and flux inside the blast furnace and maintains the permeability required for the movement of gases.
In the Blast Furnace-Basic Oxygen Furnace or BF-BOF process, iron ore and coke are first used to produce hot metal, which is subsequently converted into steel in a basic oxygen furnace.
Why does India import it?
India possesses coking-coal resources, particularly in the Gondwana region, but a large proportion of domestically available coal has high ash content and comparatively weak coking properties.
High-ash coke increases fuel consumption in a blast furnace, reduces productivity and can increase the volume of slag.
Steel plants, therefore, import low-ash coking coal to bridge the gap between domestic availability and requirement and to improve the quality of the coal blend.
Why are the other options incorrect?
Saltpetre is primarily potassium nitrate. It is used in fertilisers, fireworks and explosives, among other applications; it is not a principal imported raw material for steel production.
Rock phosphate is a principal raw material for producing phosphate fertilisers and phosphoric acid; it is not a principal raw material for ordinary steelmaking.
Since options (a) and (b) are incorrect, “All of the above” is also incorrect.
All steelmaking routes do not require coking coal to the same extent. Scrap-based electric arc furnaces and some direct-reduced iron processes use different raw materials and energy sources. The principal requirement for coking coal arises specifically in integrated BF-BOF steel plants.