Stages of Producing Metals
Most metals do not occur in pure state. They are usually combined with other unwanted metals and earthly impurities, to form what is called mineral ore. When the ore is mined, the required metal is extracted from it. Some of the impurities removed from the ores are manganese, phosphorous, silicon, sulphur, etc. This is done in a blast furnace through a process called smelting.
In Nigeria, Iron is found in large quantities in areas like Itakpe and Ajaokuta, in Kogi State.
The stages involved in the processing of metals are discussed below;
Stage 1 – Extraction Stage:
The first step in metal production always involves some form of mining. Mining refers to the process of removing the metal, in its free or combined state, from the Earth’s surface.
The rock containing the metal is dug from the soil with drilling and excavating equipment. The rock and the metal mixed together is called the metal ore (the impure metal)
The ore contains impurities that must be removed in a blast furnace in a process called smelting.
Stage 2 – Smelting Stage:
The metal ore, obtained during extraction, is heated in a blast furnace until the metal melts into liquid form. This process is called smelting.It is then separated from other impurities that have mixed with it.
Coke and limestone are mixed with iron ores, and passed into the blast furnace from the top, through something called a hopper. Hot Air is pumped into the furnace, at the same time, to help burn the coke. This produces heat and carbon monoxide which reacts with the iron ore to produce pig iron.
Limestone is added to produce quick lime which removes silicon.
The iron obtained from this process is called pig iron and it is usually in the molten state.
The impurities formed produce slag which is removed.
Stage 3 – Casting Stage:
The hot molten (liquid) metal is poured into containers of different lengths and sizes called moulds. It is left there to cool and solidify, to take up the shape of the mould. This is called casting. This is where round bars, square bars, wire, and other forms of metal are produced.