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In a blast furnace, lime and impurities in the ore create a substance called __________.
This nail is made of iron. Where does iron come from? To obtain iron, iron ore is excavated in mines. Iron ore is a solid substance in nature, a mineral that contains the element iron. The iron ore is in the bedrock.
The part of the bedrock that is not iron ore is called gangue. To obtain the iron, one must first separate the ore from the gangue. The ore is crushed and rinsed to remove most of the gangue in a processing plant. Then you get a kind of wet sand called slurry which has a high iron content - over 60 percent - in a form called 'iron ore fines'. But we want an even higher iron content.
To get that, we must form the iron ore fines into small balls, pellets. And then heat these pellets up to 1300 degrees celsius in a furnace. This allows the iron ore fines in the pellets to begin melting together, which is called sintering. The pellets are then transported to another furnace, a blast furnace. In the blast furnace, the pellets are heated to a higher temperature, together with a purified form of coal called coke, and limestone.
Hot air is blown into the lower part of the blast furnace, which raises the temperature to about 1800 degrees celsius. The coke then combines with oxygen to form carbon monoxide which flows upwards within the blast furnace. The hot carbon monoxide heats the ore and the coke. The oxygen in the ore reacts with the carbon monoxide to form carbon dioxide. This strong heat also causes the lime and impurities in the ore, such as quartz, to form a substance called slag.
The slag floats to the top of the melted iron and is then removed. When the oxygen and slag in the iron ore have been removed, what’s left is called pig iron. Pig iron contains about 4 percent carbon that comes from the coke used in the blast furnace. Iron with such a high carbon content makes it hard, but brittle. It breaks easily and is difficult to shape.
Therefore, it is transported to another furnace. In this furnace, oxygen is blown against the molten pig iron. Then the remaining carbon reacts with the oxygen and becomes carbon monoxide and carbon dioxide which are released into the air. Then the carbon content in the iron decreases to about 0,1 percent. This process is called decarburization.
Now the iron is no longer brittle, and can be shaped. This iron can be formed into beams, wire and sheets. And it is the basic material to make for instance, a nail.