INDIA’S LARGEST BLAST FURNACE

Source: InternationalIronMetallicsAssociation

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Context

Tata Steel Ltd. has commissioned ‘India’s largest blast furnace’ at Kalinganagar, Odisha, as part of the Phase II expansion of its plant.

Read about steel sector in India: https://www.iasgyan.in/daily-current-affairs/steel-sector-in-india#:~:text=The%20steel%20sector%20provides%20strategic,imports%20for%20critical%20defence%20items.

Read about iron ore in India: https://www.iasgyan.in/daily-current-affairs/iron-ore

Read about sponge iron: https://www.iasgyan.in/daily-current-affairs/sponge-iron

About Blast Furnace

A blast furnace is a large structure used primarily for smelting iron from its ores, functioning through various chemical and thermal processes.

Structure

The furnace is built as a tall, cylindrical tower, lined with firebrick to withstand high temperatures. It consists of several components:

• Throat: The topmost part where raw materials (iron ore, coke, and limestone) are fed.
• Stack: The section where gases heat the descending raw materials.
• Bosh: The part where temperature is highest (~2000°C) due to combustion reactions.
• Hearth: The bottom, where molten iron (pig iron) and slag collect and are tapped out.
• Tuyeres: Nozzles that inject hot air (blast) into the furnace to maintain high temperatures necessary for combustion.

Working

The process begins by loading iron ore, coke (a carbon source), and limestone (a flux) into the furnace's throat. As the materials descend:

• Preheating: Hot gases rise from the hearth and preheat the materials in the stack.
• Combustion Zone: Near the tuyeres, coke burns in the presence of hot air, producing carbon monoxide and heat. The heat helps sustain the high temperatures required for further reactions.
• Reduction Zones: Iron ore undergoes indirect reductionin the upper regions (~400-800°C), where carbon monoxide reduces iron oxides (Fe₂O₃) to iron. Further down (~800-1600°C), direct reduction occurs, where carbon itself reacts with remaining iron oxides to produce molten iron.
• The final product, molten pig iron, collects at the hearth, while slag(impurities combined with limestone) floats on top and is removed separately.

Applications

Blast furnaces are mainly used for producing iron, which is essential for making steel. The process can also be adapted for other metals such as lead and copper​

Definitions

Pig Iron is the intermediate product of smelting iron ore in a blast furnace. It contains high carbon content (around 3-4%) and impurities like silicon, manganese, and phosphorus, making it brittle and unsuitable for most applications until further refined​.

Slag is a by-product formed when limestone (flux) combines with impurities like silica and alumina in the iron ore. It floats on molten iron due to its lower density and is removed separately for use in construction materials or other industries.

Coke is a solid carbonaceous material derived from the destructive distillation of bituminous coal, where it is heated in the absence of air. This process removes volatile compounds, leaving behind a residue primarily composed of carbon, along with smaller quantities of hydrogen, nitrogen, sulfur, and oxygen. 

Metallurgical coke is a high-carbon material produced by heating coal in the absence of air, a process known as coking. It serves as a crucial fuel and reducing agent in the production of iron and steel in blast furnaces, providing the necessary heat and carbon for the reduction of iron ore.

Sources:InternationalIronMetallicsAssociation

PRACTICE QUESTION  Q:Steel slag can be the material for which of the following? (UPSC CSE 2020) 1. Construction of base road 2. Improvement of agricultural soil 3. Production of cement Select the correct answer using the code given below: (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 Answer: d Explanation: Steel slag is a byproduct generated during the steelmaking process, specifically from the conversion of iron ore into steel. When impurities such as carbon, silica, and phosphorus are removed from molten iron, a mixture of oxides and other compounds forms and solidifies into steel slag upon cooling. It contains a mix of calcium, silicon, magnesium, and aluminum oxides, along with metallic elements. Due to its properties, steel slag can be repurposed in various applications, including as an aggregate in construction, as a soil amendment in agriculture, and as a raw material in cement production. Its recycling helps reduce waste and promotes sustainability in the steel industry.