Extraction of iron from haematite and its impact

The extraction of iron and its impact

Extracting iron : Iron is extracted from haematite (iron ore) in blast furnace.

Figure 1: Blast Furnace 

WHAT IS A BLAST FURNACE?

 A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.

In a blast furnace, fuel, ore, and flux (limestone) are continuously supplied through the top of the furnace, while air (sometimes with oxygen enrichment) is blown into the lower section of the furnace, so that the chemical reactions take place throughout the furnace as the material moves downward. The end products are usually molten metal and slag phases tapped from the bottom, and flue gases exiting from the top of the furnace. The downward flow of the ore and flux in contact with an up flow of hot, carbon monoxide-rich combustion gases is acountercurrent exchange process.

In contrast, air furnaces (such as reverberatory furnaces) are naturally aspirated, usually by the convection of hot gases in a chimney flue. According to this broad definition, bloomeries for iron, blowing houses for tin, and smelt mills for lead would be classified as blast furnaces. However, the term has usually been limited to those used for smelting iron ore to produce pig iron, an intermediate material used in the production of commercial iron and steel.

Raw materials used in the extraction of iron:

- Haematite,Fe₂O_{3 (a compound that contains iron)}

Figure 2: Haematite

- Coke,C ( Burns in air to produce heat, and reacts to form carbon monoxide (needed to reduce iron oxide)

Figure 3: Carbon

Figure 4: Limestone

-Limestone, CaCO_{3 (Helps to remove acidic impurities fro the iron by reacting with them to form molten slag)}

 -Air,O2 ( Allows the coke to burn, and so produces heat and carbon monoxide)

HOW IS IRON EXTRACTED FROM THE ORE?

1) Production of carbon dioxide:

Coke burns with oxygen and carbon dioxide is produced

C + O2 → CO2

2) Production of carbon monoxide

Carbon dioxide further reacts with hot coke. Carbon dioxide is reduced by more coke in the furnace to form carbon monoxide.

CO2 + C → 2CO

3) Reduction of iron(III) oxide

  In this reaction, the iron oxide is reduced to iron, and the carbon is oxidised to carbon dioxide.

In the blast furnace, it is so hot that carbon monoxide can be used to reduce the iron oxide in place of carbon:

Fe₂O₃ + 3CO    →    2Fe + 3CO₂

_{4) Removal of impurities}

_{Calcium oxide reacts with silicon (IV) oxide in the iron ore. Calcium silicate (slag) is formed}

_{CaO +SiO2} → CaSiO3

At the base of the furnace, slag floats on top of molten iron as slag is less dense.

Video: extraction of iron blast furnace

IMPACT

 1) Noise pollution 

Noise from process operation or transport of raw materials and products (lorries/trucks/wagons).

2) Dust

Dust from mining–quarrying or processing can be reduced by air filter and precipitation systems and even hosing water on dusty areas or spoil heaps or carried away to somewhere else via tall chimneys 

3) Lost of land 

Scarring of the landscape from mining, quarrying, waste tips etc. as well as loss of wildlife habitat

4) Pollution

Pollution can be reduced by cleaning the 'waste' or 'used' air, water and waste gases etc. of toxic or acidic materials

SOLUTION TO IMPACT

We can reduced the impact by recycling metals. Recycling metal has numerous benefits for the environment. Recycling metal conserves energy that would otherwise be expended in drilling ore, refining the metal and other processes of the metal manufacturing process. A limited amount of metal ore is in the planet. Recycling reduces the amount of virgin ore needed to be mined by providing manufacturers with a source of already-mined metal. Recycling metal creates 36 times more jobs than sending the same amount of metal waste to the incinerator, and six times more than sending the metal to a landfill, according to the National Institutes of Health.

.Acknowledgement:  http://www.livestrong.com/article/132349-benefits-recycling-metal/

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http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/rocks/metalsrev2.shtml
http://www.chemguide.co.uk/inorganic/extraction/iron.html
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