Iron Ore Mining

IRON ORE :

Iron ores are rocks and mineral deposits from which clanging iron can be reasonably extracted. The ores are generally prosperous in iron oxides and fluctuate in color ranging from dark grey, bright yellow, deep purple, to even rusty red. The iron by its own is usually found in the structure of magnetite (Fe3O4), hematite (Fe2O3), goethite, limonite or siderite. Hematite is also identified as "natural ore". The nomenclature dates back to the early years of drawing out, when certain hematite ores comprised 66% iron and could be fed reliably into iron edifice blast furnaces. Iron ore is the unrefined substance utilized to formulate pig iron, which is one of the most important untreated materials to compose steel. 98% of the hauled out iron ore is used to produce steel.

Uncontaminated iron ore is almost nameless on the exterior of the Earth apart from the combination of Fe-Ni alloys from meteorites and very atypical forms of unfathomable mantle xenoliths. For that reason, all sources of iron ore are utilized by human diligence take benefit of iron oxide minerals, the chief form which is used in industry is known as hematite.

However, in a number of situations, more substandard iron ore sources have been utilized by manufacturing societies when right of entry to high-grade hematite ore was not obtainable. This has incorporated operation of taconite in the United States, predominantly during World War II, and goethite or bog ore utilized in the times of the American Revolution and the Napoleonic wars. Magnetite is often utilized for the reason that it is magnetic and hence effortlessly progressive from the gangue minerals.

Iron ore mining techniques differ by the type of ore that is being hauled out. There are 4 types of iron ore deposits that is being worked on at present, Based on the mineralogy and geology of the ore deposits.

HOW IS IRON OBTAINED?

Deposits of iron ore such as haematite containing iron oxide are found in sedimentary rocks from which the oxygen is removed from the iron oxide in a blast furnace to give iron as a result since iron ores consists of the element iron combined with other elements, mostly oxygen. Haematite and magnetite are the most commonly found iron ore minerals.


The smelting process allows the iron ore to be heated with carbon. The carbon combines with the oxygen and carries it away, leaving behind iron. Blast furnaces are so hot which is why they melt the iron, and drain it off to be poured into moulds to form bars, called ingots.

MINING AND PROCESSING:

Iron ore mining can be broadly divided into two categories namely 1) manual mining which is employed in small mines and 2) mechanized mining is suitable for large iron ore mines.
Manual mining method is normally limited to float ores and small mines. Mining of reef ore is also being done manually on a small scale. The float ore area is dug up manually with picks, crow bars, and spades, and then the material is manually screened and then stacked up. The waste is thrown back into the pits. The blasted broken ore is manually screened, stacked for the purpose of loading in dumpers for dispatch.

Mechanized mining is executed by the extraction of iron ore from surface deposits. The mining areas require all the operations to be mechanized and mining is exceptionally done through systematic formation of benches by drilling and blasting.
The physical processes are followed which then remove impurities and the processed ore is stockpiled and blended to meet product quality requirements and then made available to the customers.

iron mine

 

EXTRACTING IRON FROM IRON ORE USING BLAST FURNACE:

Extracting iron from its ore requires a series of steps to be followed and is considered as the penultimate process in metallurgy. The steps need the ore to be concentrated first, followed by the extraction of the metal from the concentrated ore after which the metal is purified.

How is iron extracted from its ore? Iron is concentrated by the process of calcinations. Once it is concentrated, the water and other volatile impurities such as sulfur and carbonates are removed. This concentrated ore is then mixed with limestone (CaCO3) and Coke and fed into the blast furnace from the top. It is in the blast furnace that extraction of iron occurs. The extraction of iron from its ore is a very long and forlorn process that separates the useful components from the waste materials such as slag.
What happens in the Blast Furnace? A blast furnace is a gigantic, steel stack lined with refractory brick where the concentrated iron ore, coke, and limestone are dumped from the top, and a blast of hot air is blown into the bottom. The purpose of the Blast Furnace is to reduce the concentrated ore to its liquid metal state. The iron ore, coke and limestone are crushed into small round pieces and mixed and put on a hopper which controls the input.


The most common ores of iron are hematite Fe2O3, and magnetite, Fe3O4. These ores can extract iron by heating them with the carbon present in the coke. Heating coal in the absence of air produces coke. Coke is cheap and acts as the heat source and is also the reducing agent for the reaction. Hot air is blown into the bottom of the furnace and heated using the hot waste gases from the top at a temperature of about 2200K. It is important to not waste any heat energy since it is valuable. The coke which is essentially impure carbon burns in the blast of hot air to form carbon dioxide and provides the majority of heat, thus producing a strong exothermic reaction, which is the main source of heat in the furnace.

C + O2 ----------------> CO2

Due to high temperatures at the bottom of the furnace, carbon dioxide reacts with carbon to produce carbon monoxide.

C + CO ----------------> 2CO

This carbon monoxide is the main reducing agent in the furnace.

Fe2O3 + 3CO -----------------> 2Fe + 3CO2

In the hotter parts of the furnace, the carbon acts as a reducing agent and thus reduces iron oxide to iron. At these temperatures the product of the reaction is carbon monoxide along with iron.

Fe2O3 + 3C -----------------> 2Fe + 3CO

The hot temperature of the furnace melts the iron which runs down to the bottom where it can be tapped off. Iron ore isn't pure iron oxide as it also contains some variety of rocky material. Such substances cannot melt at the temperature of the furnace and in due course would end up congesting it. As a solution, the limestone is added to the blast furnace to convert this into slag which shall melt and run to the bottom. The heat of the furnace causes the decomposition of the limestone for producing calcium oxide.

CaCO3 ------------> CaO + CO2

Since this requires absorbing heat from the furnace, it is an endothermic reaction that takes place. Therefore it becomes essential to not add too much limestone as it can cause the furnace to cool rapidly. Calcium oxide obtained on decomposition reacts with acidic oxides such as silicon dioxide present in the rock. Being a basic oxide it reacts with silicon dioxide to produce calcium silicate.

CaO + SiO2 -------------> CaSiO3

The calcium silicate produced melts and flows down the furnace to form a layer on top of the molten iron from where it can be tapped off every now and then as slag. This slag can be used in road making and as "slag cement" - a final ground slag which can be used in cement, often mixed with Portland cement.

The molten iron from the bottom of the furnace can be used as cast iron. Cast iron is flowy in nature when it is in molten state and doesn't contract much when it solidifies and is the major reason why it is useful in making castings. Nevertheless, it is actually impure as it contains about 4% of carbon. The presence of carbon makes it very hard, but also very fragile. When hit hard, it tends to shatter rather than bend or deplete.

This cast iron is used for things like manhole covers, cast iron pipes, valves and pump bodies in the water industry, guttering and drainpipes, cylinder blocks in car engines, Aga-type cookers, and very expensive and very heavy cookware.
Larger amount of molten iron from the Blast Furnace is used to make varieties of steel. Steel isn't just one substance, but a family of alloys of iron with carbon and several other metals.

steel manufacturing inputs
 


TOP IRON PRODUCING COUNTRIES:


 

 

IRON PRODUCTION IN THE WORLD :

Studies reveal that Australia and China are known to contribute as the world's largest iron ore mine producers, producing 1.5 billion metric tons and 660 million metric tons, respectively, in the year 2014. In the recent years, Brazil has bagged the second position in major production of iron. Following are other countries like China, India and Russia among the five topmost countries known for contributing towards iron production.

 

Rank

Country

Usable iron ore production (thousand tonnes)

 World

2,280,000

1

 Australia

880,000

2

  Brazil

440,000

3

 China

340,000

4

 India

190,000

5

 Russia

100,000

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