NOVEL METHOD FOR BENEFICIATION OF IRON ORES
FIELD OF INVENTION
This invention relates to a novel method for production of iron ore concentrates by selectively reducing
the gangue minerals. The present invention particularly relates to hinder settling classification
techniques on the basis of their physical properties in the iron ore bodies.
BACKGROUND OF INVENTION
Commonly iron ores are used directly after crushing and sizing in iron making however exponential e
increase in demand for steel and rapidly depleting high grade iron ore deposits has forced to device
new methods for beneficiating low grade ores, mine tailings (slimes) and other deposits with high iron
content. The most common methods so far used in iron ore industry for treating these ores are
crushing and sizing followed by gravity concentration (jigs, tables, etc) and magnetic separations.
However, these methods are not suitable for all types of ores and report loss of Fe value in the tailings
(lower recovery). Also the flow sheet are complex with series of unit operations which makes it less
attractive with economics. Some of the low grade iron ores also has complex textural association of
gangue minerals due to complex geological conditions. More over hydrothermal altrations and weather
of the deposits some times resulting in coating oxy-hydroxide minerals. This coatings are difficult to
removed by conventional beneficition techniques including magnetic operations. Therefore a novel
method has been developed to beneficiate varity of iron ore deposit, products various stages of mines
and beneficiation plant and other deposits containing sizable iron.
OBJECTS OF THE INVENTION
An object of this present invention to propose a novel method for production of iron ore concentrates by
selectively reducing the gangue minerals;

Another object of this invention is to propose a suitable beneficiation process for treating various types
of iron ore deposit, slimes, tailings and other deposits containing high iron values;
Further object of this invention is to propose the techniques of hindered settling classification on the
basis of physical properties of iron ore minerals and gangue minerals;
Still further object of this invention is to propose hindered settling classification for oxidized ore.
BRIEF DESCRIPTION OF THE PRESENTINVENTION:
According to this invention there is provided a novel method for production of iron ore concentrates by
selectively reducing the gangue minerals;
In accordance with this invention there is also provided a method for production of iron ore
concentrates from oxidized ore.
DETAILED DESCRIPTION OF THE INVENTION
In iron ore deposits hematite, magnetite and goethite are principle iron bearing minerals. Based on the
concentration of these minerals deposits are commonly classified into two type such as hematite and
magnetite. Common gangue minerals are silicates and carbonates. Textural relationships between of
these gangue minerals and ore minerals is dictated by geological conditions during the formation of
the deposits and subsequent hydrothermal altrations and weathering. Therefore it is vital to understand
the detailed textural relationships and their effect on liberation analysis of these ore bodies. For this
invention state of the art equipments were used to carryout detailed textural and liberation analysis.
Also it is necessary to identity the type of gangue minerals (quartz, alumino silicates, calcite, dolomite,
oxyhydroxy minerals) and their physical properties. This data was used to select the comminution
(crushing and grinding) perameters and subsequent unit operation. Iron ore minerals are commonly
heavier than gangue minerals and also their crushing properties are different compared to associated
gangue minerals due to difference in hardness and cleavage. Therefore, in comminution the gangue
minerals reduce to finer size whereas most of iron ore minerals form coarse size.

In this inventive process, the iron ore minerals and gangue minerals are separated by using difference
in their physical properties, size and density. When the solids particles are dropped in the fluid medium
they settle according to the different in size, shape and density (buoyancy force). In the hinder settling
classification, the separation of these settling solid particles in fluid medium is controlled by adjusting a
flow and density of fluid medium (pseudo liquid formed by solid suspended in the medium). In this
process, the heavier and coarser particles settles down below fluidized zone and termed as an
underflow fraction which is collected from the bottom of the classifer. On the hand, the lighter and finer
particles flows along with the fluid medium from side the side of the classifier and this fraction is called
overflow fraction.
In this invention, the size distribution of feed particles was controlled in the range of 0 -1 mm size and
velocity of fluid medium (teeter water) was adjusted in innovative way to separate heavy and large iron
ore minerals from lighter and fine gangue minerals. The teeter water flow rate depends on the design
parameters of the unit (hinder settling classification). In present invention, the iron ore minerals with >
75 microns size and 4 - 5.5 gm/cc density were collected as a underflow fraction and in overflow
fraction the gangue minerals with 75 - 200 microns size and 2 - 4 gm/cc density were reported.
An exemplary embodiment of the present invention provides a novel method for simultaneously
desliming the ore minerals with beneficiation. In view of the association of gangue minerals and their
fine size range (generated during the comminution), the desliming operation is generally carried out
after size reduction to remove the slimes, the separation of which is difficult in subsequent beneficiation
unit operations. The flow of fluid medium and attritioning effect caused by particle movement was used
in innovative way to remove the coatings on the ore minerals and also to deslime. Hence, the hindered
settling classifier is best option as compared to the conventional de-sliming operations like cyclones
because also acts as concentrating unit operation by separating gangue phases on the basis of particle
size and density difference.
One of the major advantages of this innovative process is simultaneously concentrating magnetite and
hematite ore minerals. When ore body contains magnetite and hematite minerals, in conventional
beneficiation process (after desliming), first magnetite is separated from the feed using low intensity
magnetic separator (LIMS) and then the non-magnetic fraction of this process is further treated in high
intensity magnetic separator (HIMS) to recover the hematite ore minerals. This two step process is

required as magnetite is ferromagnetic and hematite is paramagnetic minerals. In both magnetic
separation techniques, more than two cycles (steps) are essential to achieved the desired quality of
concentrates. Hence, in conventional process the loss of Fe values (Fe recovery) is much lower due to
three stages of operations namely deslime, LIMS and HIMS. On the other hand, the innovative process
can simultaneously perfumes desliming and recovery of both hematite and magnetite in one step, and
thereby generate a desired quality concentrates with higher Fe recovery values.
In the present invention, for achieve further improvement in Fe values (grade of the concentrate) the
additional beneficiation of underflow of hinder settling classifier is carried out by using conventional
techniques. The magnetic and gravity separation techniques were used in present invention to recover
Fe values from overflow fraction of hinder settling classifier.