FIELD OF THE INVENTION
The present invention relates to a slime beneficiation process and system for treating
slime obtained from the existing ore processing in Crushing, Screening and Washing
(CSW) plant for recovery of valuable minerals from the rejects and also to improve
the overall quality of sinter fines product being produced. More particularly, the
present invention is directed to a slime beneficiation process wherein slime from
washing plant is pumped to a cluster of Hydro-cyclones for de-sliming purpose and
some part of Hydro-cyclone concentrate is treated through SSSC thereafter and rest
is treated through Medium Intensity Magnetic Separator (MIMS). Importantly, in
MIMS, only very high quality larger hematite iron ore minerals are captured and an
innovative Self Vibrating Launder is employed to recover the valuable iron particles
from the MIMS's reject. Advantageously, the process of the present invention is
capable to recover iron ore particles with 63% Fe grade with less than 5% silica from
slime with 49%Fe at a rate of around 40t/hr making the process suitable for wide
industrial application with significant cost advantage.
BACKGROUND OF THE INVENTION
It is experienced from the existing operation in Dalli mines of Bhilai Steel Plant that
the average quality of ore fines produced contain 62% Fe, 5% SiO2 and 3% Al2O3 as
against the norm of 62.6% Fe (min.), 4.8% SiO2 (max.) and AI2O3 / SiO2 as 0.81.
High silica iron ore has caused increase in Si02 load in Blast Furnace (BF) and
thereby increases coke rate and reduces its productivity. As the iron ore fines are
sintered before being fed to blast furnace, the sinter quality gets degraded with high
alumina in ore fines. With increase in silica in fines, the sinter thus produced has
worst reducibility, though the strength and Reduction Degradation Index (RDI) value
becomes better. Al2O3 in ore fines has much deteriorating effect in sintering process
itself. The yield gets affected as well as the RDI and strength becomes worsen.
Applicants' Dalli iron ore mines have an installed capacity to process 5.55 Mt
Hematite iron ore/ annum. In Dalli mines, slime is generated through processing of
iron ore fines in classifiers i.e. classifier overflow. This mine generates reject 0.8 Mt
per annum slime having 49% Fe value into the tailing dam in processing 5.5 Mt per
annum iron ore. The tailing pond of Dalli mines is almost full with ~15 Mt slime and
unless a system of slime beneficiation is introduced, the mines operation may stand

still within 2-3 years. The existing Fluidized Bed Classifier (FBC) system can treat
50% of the slime, being generated from the washing plant while the rest 50% is
dumped as waste.
One of the most immediate technological challenges facing the industry is to deal
with the problem of processing alumina rich iron ore fines and slimes. For the
sustainable growth of iron ore industry which is beset with serious problems of
shortage of land and water, it is absolutely imperative that the state-of-the-art
mineral processing technology is utilized to take the industry closer to a position of
zero waste production. The current practice of iron ore washing in India results in
three products, namely coarse ore lumps, directly charged to blast furnace, the
classifier fines, (2-3% alumina) which with or without beneficiation are fed to
sintering plants and the slimes (6-10% alumina) which are currently discarded as
waste.
The generation of iron ore slimes in India is estimated to be 10-25% by weight of the
total iron ore processed - the iron ore values are lost to the tune of 15-20 million
tonnes every year. In addition, these slimes stored in massive water ponds pose
enormous environmental hazard. SAIL alone has more than 35 million tonnes of
slimes accumulated over the years. Considering the fact that iron ore production will
more than double and rise to at least 300 million tonnes soon, finding suitable means
of safe disposal/utilization of slimes is indeed urgent.
Considering the present magnitude of the iron ore slimes generation annually, the
quantities of slimes accumulated over the years, the fact that these slimes are
available in already very fine form and assaying reasonably high %Fe, it is obvious
that if properly beneficiated, these slimes can be considered a national resource
rather than a waste of nuisance value.
There has been thus a need in the art to developing a system and method for
processing of slime generated from washing plant to recover iron fines and reduced
silica/alumina so as to avoid wastage of iron rich slime and ensure improved quality
of the iron fines obtained at the end of the process for use in sintering for utilization
in blast furnace.

OBJECTS OF THE INVENTION
The basic object of the present invention is directed to providing a system and
process for the beneficiation of slime generated through processing of iron ore in
classifiers as classifier overflow and a system thereof so as to recover iron fines from
slime and reduce silica and alumina in concentrate product.
A further object of the present invention is directed to a system and process for the
beneficiation of slime generated through processing of iron ore as classifier overflow
to avoid environmental problems and reduce requirement of scarce land resource for
dumping of slime as wastes.
A still further object of the present invention is directed to a system and process for
the beneficiation of slime generated through processing of iron ore as classifier
overflow wherein slime from the existing ore processing plant is further processed for
recovery of valuable minerals from the rejects and also to improve the overall quality
of sinter fines product being produced in mines.
A still further object of the present invention is directed to a process for the
beneficiation of slime generated through processing of iron ore fines in classifier
overflow wherein the process parameters have been optimized for slime beneficiation
system to maximize yield of concentrate (40 T/hr) at silica level less than 5%.
A still further object of the present invention is directed to a process for the
beneficiation of slime generated through processing of iron ore fines in classifier
overflow wherein the valuable iron particles from the MIMS's reject is recovered
involving a Self Vibrating Launder as technical advancement over already known
slime beneficiation process.
A still further object of the present invention is directed to a process for the
beneficiation of slime generated through processing of iron ore in classifier overflow
wherein 63% Fe mineral particles are being recovered from slime with 49%Fe.
A still further object of the present invention is directed to a process for the
beneficiation of slime generated through processing of iron ore in classifier overflow

wherein product obtained at output of Self Vibrating Launder contains higher
proportion (30%) of 400 mesh size fraction.
A still further object of the present invention is directed to a process for the
beneficiation of slime generated through processing of iron ore in classifier overflow
wherein finished fines product quality reveals that the quality of the fines product
meets the norm of Fe% and also of SiO2% and Al2O3%.
A still further object of the present invention is directed to a process for the
beneficiation of slime generated through processing of iron ore in classifier overflow
wherein overall 40 t/hr concentrate product is being recovered through the system
with assay as ~61.7% Fe, 6.7% SiO2 and 2.6% Al2O3.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a system for the
beneficiation of slime produced through iron ore processing, comprising
a cluster of Hydro-cyclones for de-sliming of the slime pumped therein from washing
plant obtained as classifier overflow;
a Slow Speed Spiral Classifier (SSSC) for treating a part of Hydro-cyclone
concentrate;
a Medium Intensity Magnetic Separator (MIMS) for treating rest of the said Hydro-
cyclone concentrate and capture desired high quality iron ore particles as
concentrate; and
a Self Vibrating Launder to recover the valuable but finer iron ore particles from the
MIMS's reject.
A further aspect of the present invention is directed to said system wherein said self
vibrating launder is adapted to vibrate automatically with the slurry feed weight.

A still further aspect of the present invention is directed to said system wherein iron
strips are fixed inside said self vibrating launder at an angle with the flow such that
the heavier iron particles get trapped and only gangue mineral particles (being
lighter) overflow the iron strips.
Advantageously also in said system a collection line has been provided by the side of
self vibrating launder for the heavier iron rich particles.
According to a further aspect of the present invention directed to said system which
is adapted to carry out a slime beneficiation at a rate of 500m3/hr and recover
around 40 t/hr (i.e. 0.35 Mt/annum) iron ore.
A further aspect of the present invention is directed to a process for the beneficiation
of slime produced through iron ore processing using the system as described above,
comprising the steps of
(i) subjecting at least part of the slime of washing plant obtained as classifier
overflow to a cluster of Hydro-cyclones for de-sliming of the slime;
(ii) treating in a Slow Speed Spiral Classifier (SSSC) a part of Hydro-cyclone
concentrate;
(iii) treating the rest of the said Hydro-cyclone concentrate in a Medium Intensity
Magnetic Separator (MIMS) and capture desired high quality iron ore particles as
concentrate; and
(iv) involving a Self Vibrating Launder to recover the valuable iron particles from the
MIMS's reject.
Yet another aspect of the present invention is directed to said process comprising the
steps of
(i) providing slime having 49% Fe from overflow of classifier in crushing, screening
and washing plant into a cluster of hydro-cyclones with 15 mm apex and 25 mm
vortex and with % solid in the feed to cyclone optimised at 18 % and feed pressure
at 15 psi;

(ii) treating the part of said Hydro-cyclone concentrate through SSSC and rest
through Medium Intensity Magnetic Separator (MIMS) so as to capture very high
quality iron ore particles in MIMS concentrate.
(iii) treating the MIMS reject in a Self Vibrating Launder to recover the valuable iron
particles wherein the feed is made to pass over the iron strips fixed at an angle with
the flow such that the heavier iron particles get trapped and only gangue mineral
particles (being lighter) overflow the iron strips to thereby allowing collection of the
heavier iron rich particles through a collection line provided at the side of said self
vibrating launder.
According to a further aspect of the present invention directed to said process
wherein iron ore particles with 63% Fe are being recovered from slime with 49%Fe.
A still further aspect of the present invention is directed to a process wherein during
treatment of slime through cyclone followed by SSSC, the yield is as high as 36%
with quality of the concentrate obtained is ~61% Fe, 7.3% SiO2 and 2.84% Al2O3
and when the cyclone underflow product is routed through MIMS and self vibrating
launder, the quality of concentrate is enhanced to ~67.5% Fe, 1.8% SiO2 and
0.45% Al2O3, with yield of only 4% so that the overall 40 t/hr concentrate product is
being recovered by the process with assay as ~61.7% Fe, 6.7% SiO2 and 2.6%
AI2O3.
Yet another aspect of the present invention is directed to said process wherein SSSC
product contains 8% (<400 mesh) and MIMS magnetic concentrate product contains
9% of this fraction, and the overall <400 mesh fraction in the final product
concentrate goes up to 12%.
A further aspect of the present invention is directed to said process wherein the
product obtained from self vibrating launder contains higher fraction of 400 mesh
sizes (30%).
The various other objects and advantages of the present invention are described in
greater details with reference to the following accompanying non limiting illustrative
drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1: is the schematic illustration of the system for beneficiation of slime
obtained from classifier overflow involving a self-vibrating launder according to the
present invention.
Figure 2: is the photographic image of the inside view of the self vibrating lauder
showing the selective disposition of the iron strips fixed at an angle with the flow
direction adapted to trap iron fines only and allowing gangue minerals to overflow.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWING
The present invention is directed to providing a process for the beneficiation of slime
generated as classifier overflow and a system thereof to recover iron ore fines from
slime and reduce level of silica and alumina in product concentrate. Importantly, the
process is capable of producing 63% Fe grade recovered from slime with 49%Fe,
wherein the process parameters have been optimized for slime beneficiation system
to maximize yield of concentrate (40 T/hr) at silica level less than 5% and alumina
level less than 3%.
Reference is first invited to the accompanying Figure 1 that illustrate schematically
the system for beneficiation of slime obtained from classifier overflow wherein Line 1
shows the existing system for slime beneficiation involving Fluidized Bed
Classifier(FBC) and Line 2 show the system according to the present invention for
slime beneficiation involving a self-vibrating launder.
The existing iron ore processing plant consists of two stage crushing (Gyratory/Jaw
and Cone Crusher) followed by wet screening and classification. The product lump
(+10mm) is separated in the wet screening process whereas entire -10mm fractions
in slurry form enter into four numbers of twin spiral classifiers for beneficiation
purpose. Two out of four classifiers have 250 t/hr capacities each whereas the other
two have 350 t/hr throughput capacities. Classifier sand/product is raked up by the
screws and conveyed to stockyard through a series of conveyor whereas 50 % of the

classifier overflow/slime is being treated in a Fluidized Bed Classifier (FBC) system as
shown in Line 1 of Figure 1, comprising a cylindrical vessel, where the slime
(classifier overflow) enters tangentially, like hydro-cyclone, and splits into two parts,
the overflow and the underflow. From bottom of the vessel, a stream of water is
being injected to make the particle in fluidized state. A teeter bed thus formed which
allows only heavier particles to pierce through the bottom and rejects all the slimy
and light particles through its overflow. The underflow particles are further processed
in a set of 14" hydro-cyclones to get rid of gangue mineral particles. The hydro-
cyclone underflow is being treated in a Slow Speed Spiral Classifier (SSSC) to obtain
the final product.
The existing Fluidized Bed Classifier (FBC) system can treat only 50% of the about
0.8 Mt per annum slime having 49% Fe generated from the washing plant and rest
of the slime is dumped in the tailing pond.
As already the FBC system treats 50% slime being generated, the present invention
is target to treating the remaining 50% slime, which otherwise are directed to tailing
pond. In the present work, process parameters have been optimized for slime
beneficiation system to maximize yield of concentrate (40 T/hr) at silica level less
than 5%.
In the attempt to further treating the slime obtained from classifier overflow, the
existing processing plant of Dalli mines was studied in detail and performance data
were collected. The representative slime samples were collected for in-depth
investigation and analysis was done using DTA/DTG, XRD, mineralogical microscope
and XRF equipment. After characterization of the slime sample, bench scale
beneficiation tests were carried using hydro-cyclone. As 2-stage beneficiation has
been envisaged, the conventional hydro-cyclone with 15 mm apex and 25 mm vortex
was used. The % solid in the feed to cyclone was optimised at 18% and feed
pressure at 15 psi, based on the experience for mainly de-sliming purpose.
To reject the gangue mineral particles from the hydro-cyclone underflow product, a
series of experiments were carried out using Wet High Intensity Magnetic Separator
(WHIMS) equipment with varying magnetic intensities. The samples drawn were
magnetic concentrate and its non magnetic tails. These samples were dried, weighed

and subjected to chemical analysis to confirm the optimum magnetic intensities, to
be maintained for Dalli iron ore slimes. The major observations obtained during
WHIMS test are as follows:
-Very fine iron ore concentrate particles could not be captured even with magnetic
strength of 12KGauss.
-Quality of magnetic fraction after the WHIMS test gets deteriorated with increase in
magnetic strength from 6KGauss to 14KGauss.
-At 6KGauss strength, only very rich (Fe: >66%) quality particles get attracted
but the yield becomes very poor (~10%). Most of the finer iron ore concentrate
particles are swayed in non-magnetic fraction of the WHIMS test.
Based on the above experiments, it has been established that to eliminate gangue
mineral particles from the hydro-cyclone underflow product, WHIMS is not a very
effective solution and accordingly an alternative route involving SSSC and MIMS
followed by self vibrating launder was adopted. It is clearly apparent from the Line 2
of Figure 1 that illustrates the system according to the present invention for
carrying out the beneficiation process of slime obtained from classifier overflow for
beneficiation directed to efficient iron recovery. In the new system, slime from
washing plant is pumped to a cluster of Hydro-cyclones for de-sliming purpose.
Thereafter, some part of Hydro-cyclone concentrate is treated through SSSC and
rest is treated through Medium Intensity Magnetic Separator (MIMS). In MIMS, only
very high quality iron ore particles are captured. An innovative Self Vibrating
Launder has also been fabricated and installed to recover the valuable iron particles
from the MIMS's reject, details of which has been shown in accompanying Figure 2.
The launder is designed in such a way that it vibrates automatically with the slurry
feed weight. The iron strips are fixed with an angle with the flow such that the
heavier iron particles get trapped and only gangue mineral particles (being lighter)
overflow the iron strips. A collection line has been designed by the side of self
vibrating launder for the heavier iron rich particles. After implementation, samples
were drawn at various points and analyzed. Based on the analyses, further
improvement of quality of the enriched product is achieved.

Results achieved:
The following are the analyses of the trials treatment after implementing the slime
beneficiation system at Dalli mines:
- During treatment of slime through cyclone followed by SSSC, the yield is quite high
as 36% but the quality of the concentrate obtained is ~61% Fe, 7.3% SiO2 and
2.84% Al2O3. And when the cyclone underflow product is routed through MINIS and
special launder, the quality of concentrate jumps to ~67.5% Fe, 1.8% SiO2 and
0.45% Al2O3, but the yield is only 4%. Overall 40 t/hr concentrate product is being
recovered through the system with assay as ~61.7% Fe, 6.7% Si02 and 2.6% Al2O3.
- While SSSC product contains 8% (<400 mesh) and MIMS magnetic concentrate
product also contains 9% of this fraction, the overall <400 mesh fraction in the final
product concentrate goes up to 12%.
-Special launder product contains higher fraction of 400 mesh sizes (30%),
confirming satisfactory performance of the innovative self vibrating launder.
-With this addition of concentrate @ 40 t/hr also, the overall sinter fines
granulometry did not show any adverse result.
-Silica content in sinter fines have improved to 4.9% from the base figure of 5.12%,
whereas Fe% has improved marginally. This improvement is still significant as the
quality of run of mines ore has worsened during the last two years.
-The average monthly performance of Crushing Screening and Washing (CSW) plant
with respect to finished fines product quality reveals that the quality of the fines
product meets the norm of Fe% and AI2O3%.
It is thus possible by way of the present invention to providing a system and method
for beneficiation of slimes obtained from overflow of classifier which is capable of
recovering iron or particles with 63% Fe from slime with 49% Fe. The system and
process according to the present invention is adapted to carry out slime beneficiation
at a rate of 500 m3/hr and recover iron ore fines at around 40t/hr with reduced silica
and alumina content, making it suitable for sintering having prospects of wide
industrial application.

We Claim:
1. A system for the beneficiation of slime produced through iron ore processing,
comprising
a cluster of Hydro-cyclones for de-sliming of the slime pumped therein from washing
plant obtained as classifier overflow;
a Slow Speed Spiral Classifier (SSSC) for treating a part of Hydro-cyclone
concentrate;
a Medium Intensity Magnetic Separator (MIMS) for treating rest of the said Hydro-
cyclone concentrate and capture desired high quality iron ore particles as
concentrate; and
a Self Vibrating Launder to recover the valuable but finer iron ore particles from the
MIMS's reject.
2. A system as claimed in claim 1 wherein said self vibrating launder is adapted to
vibrate automatically with the slurry feed weight.
3. A system as claimed in claims 1 or 2 wherein iron strips are fixed inside said self
vibrating launder at an angle with the flow such that the heavier iron particles get
trapped and only gangue mineral particles (being lighter) overflow the iron strips.
4. A system as claimed in claims 1 to 3 wherein a collection line has been provided
by the side of self vibrating launder for the heavier iron rich particles.
5. A system as claimed in claims 1 to 4 which is adapted to carry out a slime
beneficiation at a rate of 500m3/hr and recover around 40 t/hr (i.e. 0.35 Mt/annum)
iron ore.
6. A process for the beneficiation of slime produced through iron ore processing
using the system as claimed in claims 1 to 5, comprising the steps of

(i) subjecting at least part of the slime of washing plant obtained as classifier
overflow to a cluster of Hydro-cyclones for de-sliming of the slime;
(ii) treating in a Slow Speed Spiral Classifier (SSSC) a part of Hydro-cyclone
concentrate;
(iii) treating the rest of the said Hydro-cyclone concentrate in a Medium Intensity
Magnetic Separator (MIMS) and capture desired high quality iron ore particles as
concentrate; and
(iv) involving a Self Vibrating Launder to recover the valuable iron particles from the
MIMS's reject.
7. A process as claimed in claim 6 comprising the steps of
(i) providing slime having 49% Fe from overflow of classifier in crushing, screening
and washing plant into a cluster of hydro-cyclones with 15 mm apex and 25 mm
vortex and with % solid in the feed to cyclone optimised at 18 % and feed pressure
at 15 psi;
(ii) treating the part of said Hydro-cyclone concentrate through SSSC and rest
through Medium Intensity Magnetic Separator (MIMS) so as to capture very high
quality iron ore particles in MIMS concentrate.
(iii) treating the MIMS reject in a Self Vibrating Launder to recover the valuable iron
particles wherein the feed is made to pass over the iron strips fixed at an angle with
the flow such that the heavier iron particles get trapped and only gangue mineral
particles (being lighter) overflow the iron strips to thereby allowing collection of the
heavier iron rich particles through a collection line provided at the side of said self
vibrating launder.
8. A process as claimed in anyone of claims 6 or 7, wherein iron ore particles with
63% Fe are being recovered from siime with 49%Fe.
9. A process as claimed in anyone of claims 6 to 8, wherein during treatment of
slime through cyclone followed by SSSC, the yield is as high as 36% with quality of

the concentrate obtained is ~61% Fe, 7.3% SiO2 and 2.84% Al2O3 and when the
cyclone underflow product is routed through MIMS, the quality of concentrate is
enhanced to ~67.5% Fe, 1.8% SiO2 and 0.45% Al2O3, with yield of only 4% so that
the overall 40 t/hr concentrate product is being recovered by the process with assay
as -61.7% Fe, 6.7% SiO2 and 2.6% Al2O3.
10. A process as claimed in anyone of claims 6 to 9, wherein SSSC product contains
8% (<400 mesh) and MIMS magnetic concentrate product contains 9% of this
fraction, and the overall <400 mesh fraction in the final product concentrate goes up
to 12%.
11. A process as claimed in anyone of claims 6 to 10 wherein the product obtained
from self vibrating launder contains higher fraction of 400 mesh sizes (30%).

ABSTRACT

A slime beneficiation process and system for treating slime obtained from the
existing ore processing in Crushing Screening and Washing (CSW) plant for recovery
of valuable minerals from the rejects is disclosed. In the slime beneficiation process
according to the present invention slime from washing plant is pumped to a cluster
of Hydro-cyclones for de-sliming purpose and some part of Hydro-cyclone
concentrate is treated through SSSC thereafter and rest is treated through Medium
Intensity Magnetic Separator (MIMS). Importantly, in MIMS, only very high quality
hematite iron mineral particles are captured and a Self Vibrating Launder is
employed to recover the valuable but finer iron ore particles from the MIMS's reject.
The process is capable to recover iron ore particles with 63% Fe grade with less than
5% silica from slime with 49%Fe at a rate of around 40 t/hr making the process
suitable for wide industrial application with significant cost advantage.