FIELD OF THE INVENTION
The present invention relates to beneficiation process of Banded Hematite Jasper which is a
low grade iron ore by froth flotation process with best reagent scheme to recover iron
values from pre concentrated iron ore. More particularly, the invention relates to a
beneficiation process of high siliceous low grade iron ore exhibiting complex liberation
characteristics and liberates at a particle size less than 50 microns.
BACKGROUND OF THE INVENTION
In a globally-competitive environment, steelmaking process requires high quality iron ore in
the form of lumps, sinter fines or pellet feed. The high grade hematite ore (>58% Fe (T))
available in some part of the world do not require sophisticated beneficiation. However, a
fast depletion of reserve of high grade hematite ore forecasts substantial dependence on
low grade iron ore (< 58% Fe(T)) for future steel production. Hence, it has become
imperative to revaluate and exploit the low-grade iron ore resources such as Banded
Hematite Quartz (BHQ), Banded Hematite Jasper (Henceforth, BHJ), and Banded Iron
Formation (BIF) etc., to increase mine life and achieve zero waste mining. The low grade
iron ores are normally rejected at mine site due to the presence of high levels of gangue
such as alumina and silica in the raw material, contradicting to the blast furnace chemistry.
The issues relating to low grade iron ores include composition of Iron ore with low Fe
content and high AI:Si ratio, low strength, high temperature break down, lower reducibility,
low temperature

softening and melting behavior of iron ores, etc. Generally, Iron ores with high Fe content
are desirable for better productivity in blast furnace. Alumina and Silica content should be
within permissible limit for better fluidity of slag. Therefore, the low grade iron ore is
needed to be beneficiated to reduce the level of impurities and improve the strength of
sinter and pellet quality. The beneficiation process for low-grade iron ores require higher
energy and can also cause pollution.
Froth flotation process to separate or concentrate minerals from iron ore using a wide
variety of silica collectors reagents is generally known in the art. For example, U. S. Pat.
Nos. 3,260,365, 3,363,758, 3,265,211 and 3,744,629 disclosed the use of various amines
and amine acetates as collectors in reverse froth flotation processes. U. S. Pat. No. 3960715
described the cationic froth flotation of oxidized taconite type ores using amines. The use of
primary branched aliphatic ether monoamines and alkyloxyalkaneamines as silica collectors
of martite-quartz-goethite type iron ore is described in U. S. Pat. Nos. 4319987 and
5540337. In contrast thereto, the present invention contemplated the concentration of iron
bearing minerals from banded hematite jasper which contains silica as gangue bearing
mineral where mineral-gangue association is complex with liberation at particle size less
than 50 urn. The equal distribution of silica across all size fractions shows the complexity of
liberation and difficulty in beneficiation. Accordingly, grinding of iron ore below 50pm is a
costly process and high reagent dosing is required at finer sizes. The choice of selecting
collector for treating this type of ore is more important to recover maximum values from the
ore.

Therefore, low-grade iron ore needs beneficiation prior to iron making in blast furnace. The
research on up-gradation of low grade iron ore for effective use during iron making is of
vital importance. To beneficiate low grade iron ore, application of a novel beneficiation
process strategy is needed.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention is to propose a beneficiation process of high
siliceous low grade iron ore exhibiting complex liberation characteristics with liberation
particle size less than 50 microns.
Another object of the invention is to propose a benefication process of high siliceous low
grade iron ore via pre-concentration and froth flotation.
A further object of the invention is to propose a benefication process of high siliceous low
grade iron ore which implements a reagent scheme for reverse cationic flotation in
processing the pre concentrated high siliceous low grade iron ore slimes.

SUMMARY OF THE INVENTION
According to the invention, high siliceous low-grade iron ore is crushed for feed preparation
prior to the beneficiation process. The feed material is treated in a pre-concentration unit to
upgrade the feed material based on density difference between iron bearing mineral and
gangue bearing minerals. This separation is done at a particular size fraction to avoid the
effect of size in pre-concentration unit. In pre-concentration unit, the operating parameters
are so adjusted for better separation. The concentrate obtained from pre-concentration unit
is subjected to fine grinding to address the liberation of iron bearing mineral with gangue
bearing mineral. The fine material is processed through froth flotation process for recovery
of the iron values. In froth flotation process, reverse flotation technique is employed to float
the gangue mineral from the high siliceous low-grade iron ore. Selective reagents are used
to enhance the floating characteristics of gangue mineral from the high siliceous low-grade
ore. The feed material is conditioned by the addition of chemicals before the collection of
froth at the top of the cell. Due to the modifications of surface characteristics of minerals,
the gangue mineral is floated leaving behind the iron values at the bottom of the froth
flotation cell. During flotation, the froth is collected at the top of the cell and it is considered
as tailings. The iron values at the bottom are considered as concentrates. Both samples are
analyzed for chemical analysis. The design of experiments is predefined for optimum
recovery of iron values from high siliceous low-grade ore. This design approach gives the
optimum condition of process parameters for desired yield. The combination of pre-
concentration and froth flotation process gives high grade Fe concentrate. The obtained
product is suitable for blend fine ore (BFO) which is pelletized to feed in blast furnace.

Froth flotation process is explored to recover iron values from high siliceous low-grade iron
ore with optimum dosing condition of reagents to control the surface chemistry of the
slurry.
The process developed for recovering Fe (T) values from high siliceous low grade iron ore is
ideal to blend feed ore for pellet making where the future of steel industry rests. The
invention of beneficiation process to upgrade high siliceous iron ore for the production of
quality raw material plays a key role in future steel industry.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING AND TABLES
Fig.l- shows a flow chart of beneficiation process for high siliceous low grade iron
ore according to the invention.
Fig. 2(a)- shows visible massive Quartz and sporadic quartz in the feed material
Fig. 2(b)- shows the vein of quartz cut-across all bands
Fig. 2( c)- shows presence of sporadic hematite in quartz bands
Fig. 2(d)- shows alternate thick band of Quartz and thin bands of hematite
Fig. 2(e)- shows an imaging view of BHJ showing thin veins of quartz
Fig. 3- Exhibits result of a size-wise chemical analysis of the floation feed.
Fig.4- graphically represents mass percent vis-a-vis particle size of different mineral
phases in flotation feed.
Fig 5- exhibits association of mineral phases with hematite through mineral
mapping

Table 1- size-wise chemical analysis of BHJ
Table 2- Mineral mass % of BHJ feed
Table 3- Exhibit result of Jig Unit indicating wt%, Fe & SiO2 assay of concentrate,
middling and tailing at optimum condition
Table 4- Six factor-three level Box-Behenken design of experimentation undertaken.
DETAILED DESCRIPTION OF THE INVENTION
It is known that low-grade iron ore is being rejected at the mine site due to
presence of high silica content. The low-grade iron ore comprises iron bearing
minerals and gangue bearing mineral such as silica. It is regarded as a hard ore
due to the presence of silica. The complex relationship of the iron bearing mineral
and gangue bearing mineral makes the beneficiation process more challenging to
recover the iron values.
According to the invention, a Froth flotation is employed to find a feasible
beneficiation route for the best recovery and quality of the Iron ore. In general, a
low-grade iron ore beneficiation takes place at finer size fractions due to its
liberation characteristics. Iron ore fines which are generated during beneficiation of
low grade ores are identified to be potential source to produce pellet grade
concentrate. Pellets are ideal and suitable material as a feed to blast furnace plants.
The present inventors carried-out detailed studies on low-grade iron ore to yield
quality concentrates for pellet feed. The concentration of valuable minerals involves
exploitation of the differences in physical and surface properties of the mineral and
gangue.

Low-grade iron ore lump size collected from the existing iron ore mines, particularly
in India, is Banded Hematite Jasper (BHJ). It is thoroughly mixed and crushed in
the jaw crusher to a finer size during the feed preparation. The representative
sample is drawn by coning and quartering method for chemical analysis. The size-
wise chemical analysis of BHJ is given in Tablel. BHJ, which is low grade iron ore,
consists of 40% Fe (T) with high amount of silica as a gangue bearing mineral. It is
understood that the gangue is uniformly distributed over all the size fractions of
BHJ. A sample is analyzed for characterization study using advanced
characterization techniques like SEM, QEMSCAN. The major minerals present in BHJ
are Hematite and Quartz (Table 2) as alternate bands with traces of goethite,
limonite, kaolinite, etc. The iron ore minerals present in BHJ is appeared to be 1.3
times more than gangue minerals. Textural characterization study revealed the
complex relationship of hematite and quartz due to its mineral association and
intergrowth patterns developed among ore minerals and gangue minerals. The
presence of micro grains of quartz in hematite bands shows the difficulty in
beneficiation of low-grade iron ore. The occurrence of free iron mineral is observed
at finer sizes <50μm (Figure 2). The feed material is pre-concentrated in a Denver
duplex jig unit. Denver duplex jig is used to upgrade the BHJ ore by removing the
massive bodies of quartz during stratification. The optimum conditions of process
parameters used to concentrate the BHJ iron values in a jig unit are

Test parameters:

After optimizing the jig parameters, a bulk jig test is conducted to produce sufficient
concentrate for conducting further tests with the jig products. The results of Jig tests are
presented in Table.3. The pre-concentration process of BHJ using jig unit reduces the
grinding energy (higher the silica-higher the energy) and load for cost effective process.
The concentrate obtained from jig unit is subjected to ball mill for size reduction to the
finer size. The size-wise chemical analysis of flotation feed is given in Figure 3. Mass% of
different minerals in flotation feed is shown in Figure 4. Figure 5 shows the mineral
mapping and association of minerals in flotation feed. Froth flotation is employed to
concentrate the jig product to the desired grade of pelletization using Denver D12
flotation cell. In reverse froth flotation, silica (gangue) is collected along with the froth
and iron oxides at the bottom of the cell. The conditioning of ore slurry is done at
particular percent solids for 5 minutes after regulating the slurry pH to the desired level.
Slurry pH is maintained using alkali solution. Since, flotation relies upon the surface
properties, the knowledge of the condition of the mineral surfaces is essential during
flotation process. Both silica and iron oxides acquire

surface charge in aqueous state due to the acquisition of hydroxide or hydronium ions at
the fractured bond sites. The sign and magnitude of the surface charge is dependent on
the pH of the slurry. At the desired pH, silica carries net negative surface charge and iron
oxides carries net positive charge. Difference in surface properties of minerals during froth
flotation is the key for the selection of collector. Anionic collectors are the logical choice
for net positive charge floating mineral and Cationic collectors for net negative charge
floating mineral. Different reagents are added for selective adsorption to provide
hydrophobic surfaces on mineral particles. Hence, cationic collectors such as amines are
employed to make the quartz mineral surface hydrophobic in reverse flotation. The
property of ether amines in aqueous environment during flotation is hydrolysis or
dissociation.

Ether amines exhibit the form of dissociated species in acid medium and molecular species
in alkali medium. The equilibrium for the concentration of ether amines exists at pH 10.5.
The dissociated species of collector is water soluble and easily adsorbs at the quartz
surface due to the electrostatic attraction between mineral surface bearing net negative
charge and cationic collector. With the increase of adsorption density, the hydrocarbon
chains come closer to establish Van der Waal's bonds to create high stability
configurations known as hemi-micelles. At equilibrium concentration, molecular species of
amine eliminate the repulsive forces of hemi-micelle by rendering the configuration to
more stable configuration. The molecular species also acts as frother to impart elastic
nature to the inter lamellar film of the froth which enhances the selectivity of the
separation. Dispersant and depressant are added to

iron oxides. The conditioning time of 5 minutes each for dispersant and depressant are
maintained. The role of depressant is selective adsorption on iron oxides to avoid cationic
collector adsorption on iron oxides during reverse cationic froth flotation. Amines are used
as collector in reverse cationic froth flotation with conditioning time of 15 minutes. Frother
is added to the slurry with conditioning time of 3 minutes. During the flotation, froth is
collected for 5 minutes at a particular air flow rate and stirrer speed. The froth is
considered as tailing and remains at the bottom are considered as concentrate for reverse
cationic froth flotation. The optimum reagent scheme is developed based on the best
results obtained during experiments with six-factor three levels Box - Behnken design.
Factors with corresponding levels used in the experiments are presented in Table 4.
Flotation studies indicate that concentrate of high grade Fe can be achieved with high
recovery from a feed consisting of 55% Fe. The obtained product is used for blend fine
ore (BFO) to feed in blast furnace.
According to the invention the process consists of different unit operations namely, (i)
Feed preparation (ii) Pre-concentration (iii) Froth flotation. The flow sheet of the
benefication process is shown in figurel. Textural characterization study revealed the
complex relationship of hematite and quartz due to its mineral association and intergrowth
patterns developed among ore minerals and gangue minerals (Figure 2). The presence of
Micro grains of Quartz in Hematite bands shows the difficulty in beneficiation of BH1

THE MAIN ADVANTAGES OF THE INVENTION
i. Utilization of the low grade iron ores for steel production and increase the
mine life,
ii. Environmental and Ecological benefits through effective land utilization and
reduced deforestation,
iii. Reduction in land contamination.
iv. Pre-concentration of low grade ore before fine grinding reduces carbon foot
print.
v. Selection of reagents in froth flotation process improved the grade of
flotation
concentrate,
vi. Optimum dosing of reagents during froth flotation process improves the
recovery of iron values,
vii. Value addition from low grade iron ores with viable beneficiation process

WE CLAIM
1. A process of froth flotation to recover Fe values from high siliceous low-grade
iron ore through beneficiation, comprising:
- crushing of banded hematite jasper to -10mm size for pre-
concentration in Jig unit and grinding the obtained jig concentrate to -
0.1mm size for flotation feed;
-mixing the flotation feed with water at particular percent solids to get
flotation slurry in the flotation cell;
-conditioning the flotation slurry in the flotation cell using pH modifier,
dispersant, depressant, collector and frother at particular percent solids,
pH of slurry, stirrer speed and air flow rate to float the silica gangue
material from the high siliceous banded hematite jasper; and
- optimum dosing of reagents for beneficiation of banded hematite
jasper to get high grade Fe concentrate with high recovery in a reverse
cationic froth flotation which can be blended with pellet fines to use in
blast furnace.

2. The process as claimed in claim 1, wherein the particular percent solids in the
slurry is 20-30% solids in the flotation slurry.
3. The process as claimed in claim 1, wherein the pH modifier is NaOH solution
and pH of slurry is 8.5-10.5.
4. The process as claimed in claim 1, wherein the stirrer speed is maintained at
800 - 1000 revolutions per minute.
5. The process as claimed in claim 1, wherein the air flowrate during flotation is 3
litre per minute.
6. The process as claimed in claim 1, wherein the dispersant used is
Sodium Hexametaphosphate and optimum dosing of dispersant is 2-3 kg/ton of
flotation feed.
7. The process as claimed in claim 1, wherein the depressant used is potato starch
and optimum dosing of depressant is 2-3 kg/ton of flotation feed.

8. The process as claimed in claim 1, wherein the collector used is Ether
monoamines (Sokem 503C) and optimum dosing of collector is 1-1.5 kg/ton of
flotation feed.
9. The process as claimed in claim 1, wherein the frother used is Methyl Isobutyl
Carbinol, MIBC and optimum dosing of frother is 0.1 kg/ton of flotation feed.

10.The process as claimed in claim 1, wherein said high grade Fe concentrate is in
the range of 61-62%.
11. The process as claimed in claim 1, wherein said high recovery of Fe is 62% in
reverse cationic flotation.

ABSTRACT
The invention relates to the beneficiation process of high siliceous low grade iron
ore. A process of froth flotation to recover Fe values from high siliceous low-
grade iron ore through beneficiation, comprising crushing of banded hematite
jasper ore to -10mm size for pre-concentration in Jig unit and grinding the jig
concentrate to -0.1mm size for flotation. A reverse cationic flotation is employed
at particular percent solids with a particular reagent scheme to float the silica
gangue material from the high siliceous banded hematite jasper; and optimum
dosing of reagents for beneficiation of banded hematite jasper to get high grade
Fe concentrate with high recovery in a reverse cationic froth flotation which can
be blended with pellet fines to use in blast furnace.