Introduction to Iron Making
Iron is a chemical element with symbol Fe (from Latin: ferrum) and atomic number 26. It is a metal in the first transition series. It is by mass the most common element on Earth, forming much of Earth’s outer and inner core. It is the fourth most common element in the Earth’s crust after (Oxygen, Silicon and Aluminium).
The Iron making is necessarily a reduction process, as far as the chemical theory is concerned, where reduction of the iron ores takes place to produce metallic iron.
Iron ores: Generally in Oxides: Hematite (Fe2O3), Magnetite (Fe3O4)
By Reduction conversion of Fe2O3 to Fe3O4 to FeO to Fe takes place.
So Iron Making is necessarily a REDUCTION process. Out of a many reducing agents, like C, CO, H2, we select Carbon monoxide (CO).
In case of Iron making, both the Direct and Indirect Reduction takes place. Where direct reduction needs Carbon, which is endothermic in nature, on the other hand, we have the Indirect Reduction, which is the exothermic reaction and utilizes CO in the reaction.
For direct reduction of 1 kg. Fe, only 0.23 kg. C is consumed but results in absorption of 656 kcal of heat but 0.81 kg. C is required for indirect reduction of 1 kg. Fe from Fe203 and about 1790 kcal of heat is evolved in the process.
Step by step reduction of iron ore
Steel is World‟s most useful and inexpensive alloy. It is an alloy of Iron & Carbon with/without other alloying elements. Iron making is the 1st step of an integrated steel plant.
PLAIN CARBON STEEL: here the carbon content is quite below 2.11% (in actual practice, it takes 1.6% value).
CAST IRON: Eutectic ferrous alloys (>2.11% C and eutectic reaction takes place in this alloy during cooling unlike steel)
Consumption Per Capita
• World- 150 Kg
• Developed World- 350 Kg
• INDIA – 50 Kg
• CHINA – 250 Kg
• The estimated India per capita consumption is expected to reach approximately 165 kg in 2019-20.
• Iron can be extracted by the blast furnace because Oxygen of Iron Oxides can be displaced by carbon.
• This is more efficient method than electrolysis because it is more cost effective.
• The B.F. works on a counter current principle.
• Ascending hot gases meet Descending solid charge.
• The charge includes Iron bearing materials (ore, sinter, pellets), coke & flux (Lime stone, Dolomite).
• The ascending gases cause reduction of Iron oxide in the Iron bearing materials while progressively heating it.
• The result is Production of
– Liquid slag
– Liquid Metal
– B.F. Gas of considerable calorific value
• “Stukofen ” furnace was considered to be the progenitor of the modern blast furnace.