Production of Iron Grade8 Industrial Techniques
Materials to make iron • Iron ore is only one of the four raw materials needed to produce iron. The other three are fuel (usually coke), a fluxing material (usually limestone), and air. About 2 tons of iron ore, 1 ton of coke, 1/2 ton of limestone, and 4 tons of air are needed to produce 1 ton of pig (crude) iron.
The blast furnace • The blast furnace which produces this pig iron is a large steel shell. It is nearly 100 feet high, which is lined with a kind of brick that can stand a great amount of heat.
Charging of the furnace • It is charged (loaded) through the top with layers of coke, are, and limestone as shown in the diagram above . Each blast furnace has three or more stoves to heat air for the hot blast. Air is forced through the highly heated flues (chimneys) of these stoves and brought to the blast furnace at high, temperatures.
Impurties separated • This heated air enters the furnace near the base and along with the burning coke produces a very intense fire near the base of the furnace. This heat melts the iron ore, and the limestone acts as a flux to take out the impurities from the melted iron ore.
The tapping process • Limestone has the property of combining with the earthy impurities of the iron ore to form slag. Since the slag is lighter than the molten iron, it floats on top. This slag is drawn off through the cinder notch, leaving the clean iron to be drawn off through the iron notch at the bottom. This is called tapping.
production • During these operations the iron has picked up carbon. A blast furnace operates continuously. The raw materials are fed in at the top as rapidly as necessary to provide enough hot metal for tapping, usually every 4 to 6 hours. From 100 to 125 tons of liquid iron are taken from the furnace at each tapping
products • The liquid iron flows through troughs into huge ladles mounted on railroad cars. The product of the blast furnace is usually called hot metal. After it is poured into shapes and hardened, it is called pig iron. Steel is made from either hot metal or pig iron. There are three methods of making steel: • the Bessemer process • the open-hearth process • the electric-furnace process