Iron
Ore
Magnetite
(Fe3O4)
Hematite (Fe2O3)
For the production of hydrogen, the calcined ore is first reduced
at 700-1000ºC by use of water gas or producer gas. Steam is then
passed over it. The ore gets oxidised and the hydrogen is liberated
from the steam.
The
History Says
Iron
ore was discovered on the Marquette Range on September 19, 1844 by
William A. Burt, United States Deputy Surveyor, and party who were
surveying in the Upper Peninsula of Michigan. Burt was the inventor of
the solar compass and t was the remarkable variations in the direction
of the needle that caused him to ask his party to seek about for that
which disturbed it.
The
Present Scenario
Iron ore is mined in about 50 countries. The seven largest of these
producing countries account for about three-quarters of total world
production. Australia and Brazil together dominate the world's iron
ore exports, each having about one-third of total exports.
Iron
(Fe) is a metallic element and composes about 5% of the Earth's crust.
When pure it is a dark, silvery-gray metal. It is a very reactive
element and oxidizes (rusts) very easily. The reds, oranges and
yellows seen in some soils and on rocks are probably iron oxides. The
inner core of the Earth is believed to be a solid iron-nickel alloy.
Iron-nickel meteorites are believed to represent the earliest material
formed at the beginning of the universe. Studies show that there is
considerable iron in the stars and terrestrial planets: Mars, the "Red
Planet," is red due to the iron oxides in its crust.
Iron is one of the three naturally magnetic elements; the others are
cobalt and nickel. Iron is the most magnetic of the three. The mineral
magnetite (Fe3O4) is a naturally occurring
metallic mineral that is occasionally found in sufficient quantities
to be an ore of iron.
The principle ores of iron are Hematite, (70% iron) and Magnetite,
(72% iron). Taconite is a low-grade iron ore, containing up to 30%
Magnetite and Hematite.
Hematite is iron oxide (Fe2O3). The amount of
hematite needed in any deposit to make it profitable to mine must be
in the tens of millions of tons. Hematite deposits are mostly
sedimentary in origin, such as the banded iron formations (BIFs). BIFs
consist of alternating layers of chert (a variety of the mineral
quartz), hematite and magnetite. They are found throughout the world
and are the most important iron ore in the world today. Their
formation is not fully understood, though it is known that they formed
by the chemical precipitation of iron from shallow seas about 1.8-1.6
billion years ago, during the Proterozoic Eon.
Taconite is a silica-rich iron ore that is considered to be a
low-grade deposit. However, the iron-rich components of such deposits
can be processed to produce a concentrate that is about 65% iron,
which means that some of the most important iron ore deposits around
the world were derived from taconite. Taconite is mined in the United
States, Canada, and China.
Iron is essential to animal life and necessary for the health of
plants. The human body is 0.006% iron, the majority of which is in the
blood. Blood cells rich in iron carry oxygen from the lungs to all
parts of the body. Lack of iron also lowers a person's resistance to
infection.
Name
The name iron is from an Old English word isaern which itself can be
traced back to a Celtic word, isarnon. In time, the "s" was
dropped from usage.
Sources
It is estimated that worldwide there are 800 billion tons of iron ore
resources, containing more than 230 billion tons of iron. It is
estimated that the United States has 110 billion tons of iron ore
representing 27 billion tons of iron. Among the largest iron ore
producing nations are Russia, Brazil, China, Australia, India and the
USA. In the United States, great deposits are found in the Lake
Superior region. Worldwide, 50 countries produce iron ore, but 96% of
this ore is produced by only 15 of those countries.
Iron ore is the raw material used to make pig iron, which is one of
the main raw materials to make steel. Due to the lower cost of
foreign-made steel and steel products, the steel industry in the
United States has had difficult economic times in recent years as more
and more steel is imported. Canada provides about half of the U.S.
imports, Brazil about 30%, and lesser amounts from Venezuela and
Australia. 99% of steel exported from the USA was sent to Canada.
Uses
In the United States, almost all of the iron ore that is mined is
used for making steel. The same is true throughout the world. Raw iron
by itself is not as strong and hard as needed for construction and
other purposes. So, the raw iron is alloyed with a variety of elements
(such as tungsten, manganese, nickel, vanadium, chromium) to
strengthen and harden it, making useful steel for construction,
automobiles, and other forms of transportation such as trucks, trains
and train tracks.
While the other uses for iron ore and iron are only a very small
amount of the consumption, they provide excellent examples of the
ingenuity and the multitude of uses that man can create from our
natural resources.
Powdered iron: used in metallurgy products, magnets, high-frequency
cores, auto parts, catalyst. Radioactive iron (iron 59): in medicine,
tracer element in biochemical and metallurgical research. Iron blue:
in paints, printing inks, plastics, cosmetics (eye shadow), artist
colors, laundry blue, paper dyeing, fertilizer ingredient, baked
enamel finishes for autos and appliances, industrial finishes. Black
iron oxide: as pigment, in polishing compounds, metallurgy, medicine,
magnetic inks, in ferrites for electronics industry.
Substitutes and Alternative Sources
Though there is no substitute for iron, iron ores are not the only
materials from which iron and steel products are made. Very little
scrap iron is recycled, but large quantities of scrap steel are
recycled. Steel's overall recycling rate of more than 67% is far
higher than that of any other recycled material, capturing more than
1-1/4 times as much tonnage as all other materials combined.
Some steel is produced from the recycling of scrap iron, though the
total amount is considered to be insignificant now. If the economy of
steel production and consumption changes, it may become more
cost-effective to recycle iron than to produce new from raw ore.
Iron and steel face continual competition with lighter materials in
the motor vehicle industry; from aluminum, concrete, and wood in
construction uses; and from aluminum, glass, paper, and plastics for
containers.
Industrial Applications
Spathic ore is used for the production of hydrogen by steam iron
contact process. The ore to be used must have a spongy structure in
order to present the maximum surface contact. Generally ore of light
yellow colour is preferred. It should not sinter together when
subjected to the high temperature of 1000ºC.
The ore is calcined before use to make it suitable for reduction and
oxidation cycles. For the production of hydrogen, the calcined ore is
first reduced at 700-1000ºC by use of water gas or producer gas.
Steam is then passed over it. The ore gets oxidised and the hydrogen
is liberated from the steam. The oxidised ore is then subjected to the
reduction cycle by passing water gas which makes the ore suitable for
reuse.
The arrangement for the process of oxidation and reduction cycle is
made automatic in the plant to get the supply of commercial hydrogen
which is utilised for the hydrogenation of vegetable oils.
Hydrogenation effects hardening of the oils.
Micaceous iron ore is generally soft and unctuous. It is used in the
manufacture of welding rods (electrodes). It is also used as a coating
material in the preparation of welding rods. Bog iron ore is used as
purifying and desulphurising material of producer gas and municipal
gases. The ore is filled in purifying tank through which gases are
passed and purified. Magnetite is used for the preparation of heavy
media in coal-washing plants. It has got distinct advantage over sand
as magnetite particles adhering to coal can easily be separated by teh
magnetic separator.
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