The key economic parameters for magnetite ore being economic are the
crystallinity of the
magnetite,
the grade of the
iron within the banded iron formation host rock, and the contaminant elements which exist within the
magnetite
concentrate. The size and strip ratio of most magnetite resources is irrelevant as a banded iron
formation can be
hundreds of meters thick, extend hundreds of kilometres along strike, and can easily come to more
than
three billion or
more tonnes of contained ore.
The typical grade of iron at which a magnetite-bearing banded iron formation becomes economic is
roughly
25% iron, which
can generally yield a 33% to 40% recovery of magnetite by weight, to produce a concentrate grading
in
excess of 64% iron
by weight. The typical magnetite iron-ore concentrate has less than 0.1% phosphorus, 3–7% silica and
less than 3%
aluminium.
Currently magnetite iron ore is mined in Middle East,Australia& Canada Magnetite bearing banded iron
formation is
currently mined extensively in Brazil, which exports significant quantities to Asia, and there is a
nascent and large
magnetite iron-ore industry in Australia.
We can supply Iron ore from lower grade of 40% Fe to 65% Fe.
Magnetite is magnetic, and hence easily separated from the gangue minerals and capable of producing
a
high-grade
concentrate with very low levels of impurities.
The grain size of the magnetite and its degree of commingling with the silica groundmass determine
the
grind size to
which the rock must be comminuted to enable efficient magnetic separation to provide a high purity
magnetite
concentrate. This determines the energy inputs required to run a milling operation.
Mining of banded iron formations involves coarse crushing and screening, followed by rough crushing
and
fine grinding to
comminute the ore to the point where the crystallized magnetite and quartz are fine enough that the
quartz is left
behind when the resultant powder is passed under a magnetic separator.
Generally most magnetite banded iron formation deposits must be ground to between 32 and 45
micrometers
in order to
produce a low-silica magnetite concentrate. Magnetite concentrate grades are generally in excess of
70%
iron by weight
and usually are low phosphorus, low aluminium, low titanium and low silica and demand a premium
price.
Due to the high density of hematite relative to associated silicate gangue, hematite beneficiation
usually involves a
combination of beneficiation techniques.
One method relies on passing the finely crushed ore over a slurry containing magnetite or other
agent such as
ferrosilicon which increases its density. When the density of the slurry is properly calibrated, the
hematite will sink
and the silicate mineral fragments will float and can be removed.
We can supply good quantities of Iron ore from India,Middle East and CIS countries.
Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron
ore (in the form of
lumps, pellets, or fines) to iron by a reducing gas or elemental carbon produced from natural gas or
coal. Many ores are
suitable for direct reduction.
Reduced iron derives its name from the chemical change that iron ore undergoes when it is heated in
a furnace at a high
temperature of 800 to 1200 °C in the presence of a reducing gas called syngas which is a mixture of
hydrogen and carbon
monoxide.
Direct reduction refers to processes which reduce iron oxides to metallic iron at temperatures below
the melting point
of iron. The product of such solid state processes is called direct reduced iron.
Direct reduction processes can be divided roughly into two categories: gas-based, and coal-based. In
both cases, the
objective of the process is to drive off the oxygen contained in various forms of iron ore (sized
ore, concentrates,
pellets, mill scale, furnace dust, etc.), in order to convert the ore to metallic iron, without
melting it (below 1200
°C).
The direct reduction process is comparatively energy efficient. Steel made using DRI requires
significantly less fuel,
in that a traditional blast furnace is not needed. DRI is most commonly made into steel using
electric arc furnaces to
take advantage of the heat produced by the DRI product.
Benefits :
In modern times, direct reduction processes have been developed to specifically overcome the
difficulties of
conventional blast furnaces. DRI is successfully manufactured in various parts of the world. The
initial investment and
operating costs of direct reduction plants are low compared to integrated steel plants and are more
suitable for
developing countries where supplies of coking coal are limited.
Factors that help make DRI economical:
Direct-reduced iron has about the same iron content as pig iron, typically 90–94% total iron
(depending on the quality
of the raw ore) so it is an excellent feedstock for the electric furnaces used by mini mills,
allowing them to use lower
grades of scrap for the rest of the charge or to produce higher grades of steel.
Hot-briquetted iron (HBI) is a compacted form of DRI designed for ease of shipping, handling and
storage.
Hot direct reduced iron (HDRI) is iron not cooled before discharge from the reduction furnace, that
is immediately
transported to a waiting electric arc furnace and charged, thereby saving energy. The direct
reduction process uses
pelletized iron ore or natural "lump" ore. One exception is the fluidized bed process which requires
sized iron ore
particles.
The direct reduction process can use natural gas contaminated with inert gases, avoiding the need to
remove these gases
for other use. However, any inert gas contamination of the reducing gas lowers the effect (quality)
of that gas stream
and the thermal efficiency of the process.
Supplies of powdered ore and raw natural gas are both available in areas such as Northern Australia,
avoiding transport
costs for the gas. In most cases the DRI plant is located near natural gas source as it is more cost
effective to ship
the ore rather than the gas.
This method produces 97% pure iron.
India is the world’s largest producer of direct-reduced iron, a vital constituent of the steel
industry.[4] Many other
countries use variants of the process, so providing iron for local engineering industries.