Iron Extraction by Blast Furnace in Metallurgy

Iron, when extracted from iron ore such as haematite containing iron(III) oxide, Fe2O3, in a blast furnace is called iron extraction blast furnace metallurgy. In this reduction reaction, oxygen is removed from the iron(III) oxide to leave behind iron. Generally, the extraction of metals and their isolation are based on three major procedures. The steps are:

1. Concentration of Ore

2. Extraction of metal from concentrated ore and

3. Purification of the metal

In the following article extraction of iron from its ore in the blast furnace is described in light of these three quintessential steps. Extracted iron is used in several ways like building a bridge, house etc. The process is very important in the domain of Metallurgy. 

What is the Procedure of Extraction of Iron From its Ore?

Extraction of iron is a lengthy process which commences from Concentration through calcination roasting. Water and other volatile impurities like sulfur and carbonates are removed by the process of Concentration. The concentrated ore is blended with limestone (CaCO3) and Coke and fed into a blast furnace from the top. Extraction of iron happens in the blast furnace. It is a very lengthy and submissive procedure. The above process helps in separating the useful ingredients from the waste materials like slag.

What is Calcination?

Calcination is the procedure of converting an ore into an oxide by heating it strongly. The heating of ore is materialized below its melting point either in absence of air or in a controlled supply. The carbonates and hydroxides are converted into their respective oxides by this process. 

Calcination also separates the moisture and volatile impurities. Calcination may also be termed as a thermal process which is used to convert ores and other solid materials by providing thermal decomposition. The word calcination came from a Latin word ‘calcinare’ which means ‘to burn lime’. Therefore, decomposition of limestone (calcium carbonate) to lime (calcium oxide) and carbon dioxide takes place by the method of calcination. The products from calcination are termed as calcines.

\[ CaCO_{3} = CaO + CO_{2} \]

What is Roasting?

Roasting is a method of Metallurgy. It converts an ore into its oxide by heating it above the melting point in the presence of excess air. While roasting is a process that is used for converting sulfide ores, calcination is generally used in the oxidation of carbonates. Moisture and non-metallic impurities in the volatile gasses are extracted during the process of roasting. Oxidation, reduction, sulfation, chlorination and pyrohydrolysis are included in the solid-gas thermal reaction which is an important part of roasting. 

The major drawback of the process is that roasting involves sulfides which are the main source of air pollution. Apart from that, the process of releasing a large amount of metallic as well as toxic and acidic compounds results in harm to the environment. When Zinc sulfide is converted into zinc oxide, that will be an example of roasting.

\[ 2ZnS + 3O_{2} = 2ZnO + CO_{2} \]

What are the Differences between Calcination and Roasting?

The major differences between the Calcination and Roasting are given in the following table:

What Happens in the Blast Furnace?

The concentrated ore is reduced to its liquid metal state in a chemical method in Blast Furnace. A Blast Furnace is a giant, steel stack parallel with refractory brick where the concentrated ore, coke and limestone are dumped from the top and a blast of steamy air is blown into the bottom.

All the three components are crushed into small round pieces and blended and put on a hopper which regulates the input. Hot steamy air is blown from underneath and coke is burned to capitulate temperatures up to 2200K. The maximum portion of heat for this process is produced by burning coke.

Coke reacts with the oxygen in the hot air to generate Carbon Monoxide (CO) at such high temperatures. After that, the CO and heat move in the upward direction to meet the raw material coming down from the top. The temperature in the upper portion of the Blast Furnace is eventually lower than the 2200K at the lower portion. Ferrous Oxide (FeO) is generated by reducing Haematite (Fe2O3) and Magnetite (Fe3O4).The following reactions occur in the blast Furnace at 500-800K in the upper portion with lower temperatures:

\[ 3Fe_{2}O_{3} + CO = 2Fe_{3}O_{4} + CO_{2} \]

\[ Fe_{3}O_{4} + 4CO = 3Fe + 4CO_{2} \]

\[ Fe_{2}O_{3} + CO = 2FeO + CO_{2} \]

In the lower portion of the Blast Furnace (at 900-1500K)

\[ C + CO_{2} = 2 CO \]

\[ 3FeO + CO_{2} \] = \[Fe + CO_{2} \]

The limestone is also decomposed to CaO that separates the silicate impurity of the ore in the form of Slag. It can be easily removed from the molten iron. Approximately 3-4% of Carbon and little quantities of many other impurities like sulfur, Silicon etc are contained in the iron manufactured in the Blast Furnace. The same is termed as Pig Iron. The strength is acutely hampered by the impurities. Carbon plays a pivotal role in influencing the brittleness and hardness balance in iron. The above component is melted again with scraps of iron and coke to further reduce the carbon content in Pig iron. It is also subject to the blast of hot air. The above kind of iron is termed as cast iron and contains slightly lower carbon content (2-3%). Cast iron is harder than pig iron.

What is Wrought Iron/Malleable Iron?

The purest form of iron commercially available is the Wrought Iron. It is made by heating cast iron in a furnace lined with Haematite (Fe2O3). Carbon is reacted with Haematite to produce pure iron and carbon monoxide gas which escapes.

\[ Fe_{2}O_{3} +3C \] = \[2Fe + 3 CO \]

After that limestone is added as flux and slag is created. Various impurities like S, Si pass into the slag and later on slag can be easily removed to produce pure iron.The above procedure describes the Extraction of Iron in the Blast Furnace. It is one of the most important phenomenons in the context of Metallurgy. The extracted iron can be utilized in several sectors. 

Iron extraction by blast furnace metallurgy is an extremely important concept which shows what happens after the iron has been extracted from iron ore in a blast furnace. This whole process is a reduction reaction where oxygen is removed from the iron (III) oxide to leave behind iron. This process of metallurgy is taught in-depth in chapter 6 of Class 12 chemistry called general principles and processes of isolation of elements. 

In order to get a good score in chemistry in the board examination students are advised to learn in-depth about this concept as it is extremely important and there are high chances of it coming in the board examination. Students wanting to pursue a career in the medical field, need to appear for the NEET examination in which they will have to study metallurgy. Therefore, it is advisable to get a clear understanding of this concept.

The objective is to make the learning process feel like a breeze, vedantu’s team has curated study material and has definitions and examples which can help you learn in an easier way, concentrating on the main topic and not cluttering your brain with unnecessary information. A PDF can be downloaded for free and the study material can be  studied in an offline environment. The following article mainly deals with the Extraction of iron from its ore in the blast furnace. Iron extraction is an extremely important process as it deals with building a bridge, house et cetera. Iron extraction is one of the main parts of metallurgy.

Iron Extraction Procedure

Iron extraction is considered as an extremely lengthy process that starts from concentration and ends through calcination roasting. The process of concentration deals with the removal of water and other volatile impurities like sulfur and carbonate. This is concentrated or is then blended with limestone and coke and fed into the blast furnace from the top. The extraction of iron occurs in the blast furnace. This process helps in separating the useful ingredients from the waste materials like slag.

There are certain steps that are followed for the process of extraction and isolation of metals from ores-

• Purification of metal

• Concentration of an ore

• Metal isolation from its concentrated ore.

Important Concepts Explained in the Chapter

6.1 Occurrence of Metals

6.2 concentration of ores

6.2.1 Hydraulic Washing

6.2.2 Magnetic Separation

6.2.3 Froth Floatation Method

6.2.4 Leaching

6.4 Thermodynamic Principles of Metallurgy

6.4.1 Applications

A) extraction of iron from its oxides

(c) Extraction of zinc from zinc oxide

6.5 Electrochemical Electrochemical Principles of Metallurgy

6.6 Oxidation Reduction

6.7 Refining

a) distillation

b) liquation

c) electrolytic refining

d) zone refining

e) vapor phase refining

f) chromatographic methods

6.8 Uses of Aluminum, Copper, Zinc, and Iron.