Blast Furnace Iron Ore Reduction
Introduction
When iron was first discovered, it was made by forging together synthetic forms of iron ore with charcoal and other materials. The discovery and improvement of the blast furnace allowed iron to be produced in its elemental form, making it much more easily manipulated and worked.
Reducing Iron Ore in a Blast Furnace
The blast furnace is a large steel shell enclosed at the top by a refractory-lined dome, filled at the bottom with the metallic ore, iron oxide; and downward at an angle, a series of gas nozzles and burners which play a flaming mixture of air and fuel, such as coal/coke, into the furnace. As the iron oxide is fed into the furnace via the charge hole, located at the top, this mixes with the burning fuel, thereby creating a chemical reaction which reduces the iron oxide to its basic element - iron. The heat associated with this transformation makes this an ore reducing process.
An internal blower blows a blast of air into the furnace. This hot air, mixed with the burning air-fuel mixture, further increases the temperature within the furnace, pushing the surface temperature of the iron to over 1600 degrees Celsius. The materials are loaded into the upper part of the blast furnace, with coke, limestone, and other ores being added at the centre and the bottom. The various combinations of these elements create a reaction which further reduces the ore. In the top section the reduction of iron oxides is completed while in the bottom section, slag, a by-product of the process, is created.
The reduced iron, separated from the slag, is distributed evenly throughout the furnace, cooled and allowed to settle at the base. It is then tapped off as molten alloy and sent for further refining. The molten alloy formed then undergoes further processing to remove unwanted elements, such as carbon and phosphorus, and redistributes the desired elements, such as manganese, chromium and nickel, creating a finished alloy.
Conclusion
The blast furnace has enabled iron to be produced in its elemental form, making it much more easily manipulated. The process involves injecting air and fuel, such as coal/coke, into the furnace, creating a chemical reaction which reduces the iron oxide to its basic element - iron. A slag, a by-product of the process, is created in the bottom section of the furnace and removed. The molten alloy formed then undergoes further processing to create a finished alloy. Overall, this process has been essential in the production of iron since it was discovered.
