Extracting the raw iron to use them in various manufacturing processes is a vert wide business in industry. It is also very important industry to supply required iron from iron ores. In this article, we will summarize the production of raw iron in blast furnaces.
Blast furnaces are contraptions that are used to reduce the raw iron from iron ores with limestones and coke. Blast furnace is a refractory walled and 7-11 metres diameter towers that are filled with layers of iron ore, coke and limestone. And hot blast air is forced from the below side of furnace to reduce the iron from its ore.
With the application of hot gas(roughly around 1650 Celsius degrees), the coke is burned. Carbon monoxide is supplied as hot gas and it is also produced from the combustion of coke. The iron charge is come from top of the furnace to below side with the application of hot gases. The hot gas includes also, carbon dioxide, oxygen, vapor, hydrogen, nitrogen. The production of iron from iron ores can be summarized with following chemical reactions inside the blast furnaces;
The hematite is the starting iron ore that is reacted with carbon monoxide. The output is the iron-ozide and corbon dioxide.
The produced carbon dioxide and the carbon that is originated from the coke are reacted and produced carbon monoxide, which is a very important to reduce iron from its ore.
The produced carbon monoxide is reacted with iron oxide, and the pur iron and carbon dioxide is produced.
Because of it heaviness, produced iron from the last chemical reaction is came to the bottom of furnace, and drips into the iron ladle.
The role of limestone is very important. It reacts with the impurities in iron that is produced, that creates slug on the liquid iron in the ladle.
The iron that is produced in blast furnaces called as pig iron which has roughly 4% of carbon and other impurities inside it. Cupola furnaces are commonly used to obtain gray cast iron from pig iron. To produce steel from pig iron, the impurities must be controlled in much more precise manner.
Image source: Fundemantals of modern manufacturing.