FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
A PROCESS FOR STAGEWISE BENEFICIATION OF MEDIUM TO HIGH GRADE BANDED HEMATITE QUARTZITE (BHQ).
2 APPLICANT (S)
Name : JSW STEEL LIMITED.
Nationality : An Indian Company.
Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg, Mumbai - 400 026,
State of Maharastra, India.
3 PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to beneficiation of medium to high grade banded hematite quartzite (BHQ) and more particularly, to a process for stagewise beneficiation of medium to high grade banded hematite quartzite (BHQ) for its conversion to cost effective input raw materials for iron and steel industry. More particularly, the present invention is directed to developing an economically viable and effective beneficiation process to enrich BHQ ore to produce pellet grade fines. The advancement is thus directed to optimized beneficiation technique for BHQ iron ore with process stages directed to favour value addition in the optimized beneficiation technique .The process of banded hematite quartzite (BHQ) beneficiation would enable better concentrate grade and higher recovery.
BACKGROUND ART
It is well known in the field of processing ore for input to iron and steel producing industry that very low grade Iron ore cannot be used in metallurgical plants and needs to be upgraded to increase the iron content and reduce the gangue content. A process adopting to upgrade ore is called Beneficiation. Iron ore is upgraded to higher iron content through concentration. Iron ore is being beneficiated all round the world to meet the quality requirement of Iron and Steel industries. However, each source of Iron ore has its own peculiar mineralogical characteristics and requires the specific beneficiation and metallurgical treatment to get the best product out of it. The choice of the beneficiation treatment depends on the nature of the gangue present and its association with the ore structure. Several techniques such as washing, jigging, magnetic separation, advanced gravity separation and flotation are being used to enhance the quality of the Iron ore.
Due to the high density of hematite relative to silicates, Ore separating line conventionally involves a combination of crushing and milling as well as heavy liquid separation. This is achieved by passing the finely crushed ore over a bath of solution containing bentonite or other agent which increases the density of the solution. When the density of the solution is properly calibrated, the hematite will sink and the silicate mineral fragments will float and can be removed.

With the enhanced steel production as envisaged hematite iron ore availability wiil not last long. In order to ensure longer period of ore availability, it is pertinent to use beneficiated banded hematite quartzite (BHQ) & banded magnetite quartzite (BMQ) iron ores. Thus, with the fast depletion of the limited reserves of high grade iron ore and to meet the iron ore requirement of steel plants, the low grade iron ore like banded hematite quartzite (BHQ) and banded hematite jasper (BHJ) have been the focus of interest.
BHQ occurs as compact hard rocks or in the form of weathered soft rocks. Banded magnetite sandstone formation of sedimentary origin underwent metarnorphic transformation several times due to heat and pressure from the tectonic movements of the earth in the later stages. As a result, banded magnetite sandstones altered to banded magnetite quartzite's (BMQ's). Some BMQ's later got altered to banded martite quartzite and banded hematite quartzite due to further application of heat and pressure. Till date, not much of research work has been carried out on the possibilities of making use of BHQ as a feed material for iron making and required standardizing an economically viable process for its beneficiation for effective utilization of such ores in industry.
Thus inspite of the need in the art to develop methodologies for BHQ beneficiation, no proven beneficiation methodology for BHQ beneficiation is available at present. There has been therefore a persistent need in the related art to developing a very specific and economically viable beneficiation technique for processing of BHQ based ore. The BHQ based studies as given above revealed that BHQ is hard material by nature and consume huge power for size reduction to liberate silica particles from iron bearing particles. Most of the work carried out on BHQ iron ore by various laboratories shows that the separation process was carried out on finer size material, i.e., below 150u. Single step grinding of whole bulk material to finer size generates large quantity of ultra fines automatically increases the overall tailing loss.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to develop a process for stagewise beneficiation of medium to high grade banded hematite quartzite (BHQ) to produce to pellet grade fines with substantially high Fe concentration and significant weight

recovery in a cost effective manner, as input raw materials suitable for consumption in iron and steel industry,
A further object of the present invention in directed to developing a process for stagewise beneficiation of banded hematite quartzite (BHQ) to produce to pellet grade fines as input raw materials for iron and steel industry.
A further object of the present invention in directed to developing a process for beneficiation of banded hematite quartzite (BHQ) to produce to pellet grade fines as input raw materials for iron and steel industry wherein Fe loss in tailing could be reduced avoiding generating large quantity of ultrafines due to single step grinding of
bulk ore.
A further object of the present invention in directed to developing a process for beneficiation of banded hematite quartzite (BHQ) to produce to pellet grade fines as input raw materials for iron and steel industry wherein Fe loss in tailing could be reduced due to reduction in generation of fines.
A further object of the present invention in directed to developing a process for beneficiation of banded hematite quartzite (BHQ) to produce to pellet grade fines as input raw materials for iron and steel industry wherein power consumption in grinding process could also be saved.
A further object of the present invention in directed to developing a process for beneficiation of banded hematite quartzite (BHQ) to produce to pellet grade fines as input raw materials for iron and steel industry wherein extraction of the valuable minerals in gravity separation tails could be achieved beneficially.
A further object of the present invention in directed to developing a process for beneficiation of banded hematite quartzite (BHQ) to produce to pellet grade fines as input raw materials for iron and steel industry wherein Fe concentrate in final product as high as about 65% could be achieved from an input feed Fe concentrate of about 45% and with 29% Fe in tailing loss.

SUMMARY OF THE INVENTION
Thus according to the baste aspect of the present invention there is provided a process for beneficiation of medium to high grade banded hematite quartzite (BHQ) comprising stagewise beneficiation involving :
i) subjecting the banded hematite quartzite (BHQ) to separation process at
coarse size (-6 mm) involving selectively jig and spiral; followed by,
ii) separation at finer size involving selectively spiral, medium intensity magnetic separation (MIMS),wet high intensity magnetic separator (WHIMS).
A further aspect of the present invention is directed to a process for beneficiation of medium to high grade banded hematite quartzite (BHQ) wherein said stagewise beneficiation comprises a first stage beneficiation at coarser fraction comprising -6+ 3mm, -3+1 mm and -1 mm followed by finer size beneficiation involving finer size fractions comprising about 75 u and 45 u.
A still further aspect of the present invention is directed to a process for beneficiation of medium to high grade banded hematite quartzite (BHQ) wherein magnetic separation is carried out at 45 u size in three stages of WHIMS involving rougher, scavenger and cleaner WHIMS to thereby recover more iron bearing minerals in concentrate and to reduce the loss of iron bearing minerals in tailings.
A stili further aspect of the present invention is directed to said process for beneficiation of medium to high grade banded hematite quartzite (BHQ) comprising:
(i) crushing run-of-mine (ROM) sample (size 50 to 150 mm) stage-wise to below 6 mm size and screening the crushed material to get -6+3mm, -3+lmm and lmm size fractions ;
(ii) the said -6+3mm and -3+lmm size material was separately processed in rougher jig wherein for further extraction of iron bearing minerals from rougher jig tailing, the rougher jig tailing of -6+3mm and -3+lmm were reprocessed separately in scavenger jig to reduce the tailing loss;
(iii)the said -1 mm size material was treated in spiral concentrator and obtained there from concentrate, middling and tailing;

(iv)the overall concentrate obtained from gravity separation process was mixed together and subjected to grinding process to achieve 80% passing -75u size to get liberated iron bearing minerals for further up-gradation;
(v) the ground product of gravity separator concentrator was subjected to desliming cyclone to remove slimes ;
(vi)the de-sliming cyclone underflow was subjected to medium intensity magnetic separator (MIMS) and the magnetic concentrate of the MIMS was obtained as a final product;
(vii) the overall gravity separation tailing was mixed together and subjected to grinding process to achieve 80% passing -75p size to get liberated iron bearing minerals for further up-gradation;
(viii) the ground product of gravity separator tailing was subjected to desliming cyclone wherein the de-sliming cyclone underflow was subjected to two stage spiral concentrator for removing as much as gangue minerals, the concentrate obtained from cleaner spiral was considered for further up-gradation while the middling and tailing of rougher and cleaner spiral was discarded as tailing;
(ix)the spiral concentrate obtained from the processing of gravity separator tailing was mixed with MIMS non-magnetic product, the mixed product was further ground in a ball mill to achieve 80% passing -45u size to get liberation;
(x) the ground product was processed in stub cyclone to remove as much as liberated silica;
(xi)the stub cyclone underflow was processed through rougher, cleaner and scavenger wet high intensity magnetic separator (WHIMS) to obtain two more products while the scavenger stage WHIMS non-magnetic product was treated as tails.
A further aspect of the present invention directed to said process wherein said
processing in jig carried out involving:
Stroke length 2.04 to 3.75 preferably about 3.75 cm,
Pulsation rate/min : 150 to 225 preferably about 225,
Jigging time : preferably about 5 mins, and
Water flow rate : preferably about 5ltr/min
A further aspect of the present invention directed to said process wherein said processing in spiral carried out involving:

Water flow rate: 27.72 to 61.31 preferably about 45.72 Itr/min, % solids : 25 to 40 preferably about 25, and Splitter position : about 25% from original position
A still further aspect of the present invention directed to said process wherein said
processing in De-sliming cyclone (Hydrocyclone) carried out involving:
Vortex finder diameter: about 25 mm ,
Spigot diameter: about 10 mm,
% of solids : 15.3, and
Pressure : about 30 psi .
Yet another aspect of the present invention is directed to said process, wherein de-sfiming cyclone underflow of jig and spiral concentrator concentrate are subjected to processing in said medium intensity drum magnetic (MIMS) separator to separate magnetic concentrate from non magnetic involving required magnetic intensity preferably of 7000 Gauss.
A still further aspect of the present invention directed to said process, wherein said
processing of feed in stub cyclone is carried out involving :
Cyclone size : about 12.5mm ,
Vortex finder diameter: about 25mm, ,
Spigot diameter: about 20mm,,
Pressure : about 20psi, ,
Slurry % of solids : about 20.
Cyclone parameters were calculated based on formula to get the required d50 cut
point.
A still further aspect of the present invention directed to said process, wherein processing of feed in said Rougher WHIMS (SLON magnetic separator) is carried out
involving;
Magnetic field intensity: 1500 to 7000 preferably about 7000gauss, Pulsation rate/min : about 230, Residence time : about 3 mins ,

A stili further aspect of the present invention directed to said process, wherein
processing of feed in said Cleaner WHIMS (SLON magnetic separator) is carried out
involving:
Magnetic field intensity : about 5000 Gauss,
Pulsation rate/min : about 230,
Residence time : about 3 mins.
A still further aspect of the present invention directed to said process, wherein
processing of feed in said Scavanger WHIMS (SLON magnetic separator) is carried
out involving:
Magnetic field intensity: about 3000 Gauss,
Pulsation rate/min : about 230,
Residence time : about 3 mins.
A still further aspect of the present invention directed to said process, carried out such as to achieve overall product concentrate comprising 63 to 65 % Fe preferably about 64.8% Fe and 5.0 to 7.0 % Si02 preferably about 6.6% St02 with a recovery level of 40 to 45 % preferably about 42.2% recovery.
A further aspect of the present invention directed to said process, wherein said gravity separation at coarser size involving jig and spiral is suitable for BHQ ore having quartz band width varying from 10mm to less than 1mm.
The various other objects and advantages of the present invention are described in greater details with reference to the following accompanying non limiting drawing.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1 is the schematic illustration of the flow sheet for the BHQ beneficiation process according to the present invention showing the respective process steps and the products, middling, rejects and tailing obtained at different stages of the process.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURE
The present invention relates to a suitable beneficiation technique to process BHQ ore to produce pellet grade fines and more particular to a cost effective process of beneficiation of medium to high grade banded hematite quartzite (BHQ) for conversion to input raw materials for iron and steel industry. Importantly, the present invention is directed to a process involving separation process at coarse size with the combination of jig & spiral followed by further separation in finer size. The developed BHQ beneficiation flow sheet consists of separation process at coarse size with the combination of jig & spiral followed by finer size (Spiral, MIMS and WHIMS). The generation of ultra fines during grinding process is reduced due to stage-wise beneficiation at coarser fraction (-6+3mm, -3+lmm, and -1mm) followed by finer size (75u and 150u). Magnetic separation is carried out at -45u size using three stage WHIMS, i.e., rougher, scavenger and cleaner WHIMS to recover more iron bearing minerals in concentrate and to reduce the Joss of iron bearing minerals in tailing.
Reference is invited to the accompanying Figure 1 which shows the flow sheet for the BHQ beneficiation process developed according to the present invention illustrating the respective process steps and the products, middling, rejects and tailing obtained at different stages of the process.
The present ore beneficiation process is applicable for the BHQ iron ore which assayed 45% Fe, 35% Si02, and 0.65% Al203 such as BHQ reserve of Harishankar mines located at Karnataka, India or similar other sources. In this grade of BHQ ore, hematite and martite are the predominant iron bearing minerals with minor quantity of goethite. Quartz is the major gangue mineral. The thickness of the quartz band varies from 10 mm to less than 1 mm size. From the liberation studies conducted previously, it was found that ~82% of the iron bearing minerals and ~85.0% of quartz minerals were liberated at the grain size -45u. Depending on the feed characteristics various beneficiation techniques like jig, spiral, cyclone, and magnetic separation process were used.

It would be apparent from the accompanying Figure 1, that the BHQ beneficiation process according to the present invention comprised the following stages:
(i) The run-of-mine (ROM) sample (size 50 to 150 mm) which assayed 45% Fe, 35% Si02, and 0.65% Al203, is first stage-wise crushed to get below 6 mm size. The crushed material is screened to get -6+3mm, -3+lmtn and -lmm size fractions for further beneficiation process.
(ii) The -6+3 and -3+lmm size materials are processed in separately rougher jig. For further extraction of iron bearing minerals from rougher jig tailing, the rougher jig tailing of -6+3mm and -3+lmm are reprocessed separately in scavenger jig to reduce the tailing loss.
(iii) The -1 mm size material is treated in spiral concentrator and obtained concentrate, middling and tailing.
(iv) The overall concentrate obtained from gravity separation process was mixed together and subjected to grinding process to achieve 80% passing -75u size to get liberated iron bearing minerals for further up-gradation.
(v) The ground product of gravity separator concentrator is subjected to desliming cyclone to remove slimes. The d50 cut point of de-sliming cyclone is 11.2u. The cyclone overflow is rejected as tailing.
(vi) The de-sliming cyclone underflow is subjected to medium intensity magnetic separator (MIMS). The magnetic filed intensity of MIMS is maintained 7000 Gauss. The magnetic concentrate of the MIMS is considered as final product.
(vii) The overall gravity separation tailing was mixed together and subjected to grinding process to achieve 80% passing -75p size to get liberated iron bearing minerals for further up-gradation.
(viii) The ground product of gravity separator tailing is subjected to desliming cyclone. The de-sliming cyclone underflow is subjected to two stage spiral concentrator for removing as much as gangue minerals. The concentrate obtained from cleaner spiral is considered for further up-gradation. The middling and tailing of rougher and cleaner spiral is discarded as tailing.
(ix) The spiral concentrate obtained from the processing of gravity separator tailing is mixed with MIMS non-magnetic product. The mixed product is further ground in a ball mill to achieve 80% passing -45u size to get liberation.

(x) The ground product is processed in stub cyclone to remove as much as liberated silica. At this stage also the deslimrng cyclone overflow is rejected as tailing.
(xi) The stub cyclone underflow is processed through rougher, cleaner and scavenger wet high intensity magnetic separator (WHIMS) to achieve two more products. The scavenger stage WHIMS non-magnetic product is treated as tails.
It has been experienced through past operations that for pelletization process, iron ore fines with minimum grade 63.0% Fe is required. To achieve this grade of concentrate with substantial weight recovery, the present invention selectively employs the flow sheet comprising the following process steps in beneficiation of BHQ ore:
-double stage jig and spiral separator to extract as much as iron bearing minerals
at coarser size (-6+3 mm and -3+lmm, -1mm)
-The tails from the gravity separation process is treated in double stage spiral
separator after grinding (80% passing 75u) and de-sliming to get upgraded
product to treat in further separation process like WHIMS,
-The ground product of MIMS non magnetic and spiral separator product was
treated in stub cyclone. (In stub cyclone separation takes place based on specific
gravity difference between ore mineral and gangue mineral). In stub cyclone the
improvement in Fe grade is nearly 5.0%,
-To get better yield and grade of the product, the stub cyclone underflow is
treated in three stage WHIMS (Rougher, cleaner and scavenger).
The above stages of the developed flow sheet for BHQ ore beneficiation process according to the present invention is carried out as per the following detailed process steps:
Rougher and scavenger jig
In Jig, separation takes place based on specific gravity (SG) difference between iron bearing and gangue minerals. In jig separation of minerals of different specific gravity is accomplished in a bed which is rendered fluid by a pulsating current of

water so as to produce stratification. On the pulsation stroke the bed is normally lifted as a mass, and then as the velocity decreased it tends to dilate, the bottom particles falling first until the whole bed is loosened. On the suction stroke it then closes slowly again and this is repeated at every stroke. Here motion can be obtained by pulsation of water using fixed sieve.
The jigging studies are carried out on -6+3mm and -3+lmm size fraction. A Denver mineral jig fitted with 1mm screen and 3mm steel balls as ragging material is used for the jigging studies. The cross sectional area of jig is 10.5 xl4.8 cm. The feed rate is 2.5 to 3.0kgs in a batch. It has adjustable stroke lengths with a hutch which convincingly maintains pulsation of water flow for effective separation of light and heavies. Each test is carried out for 5 minutes at water flow rate of 51it/min. The effect of stroke length and pulsating rate is evaluated. The stroke length is varied form 2.04 to 3.75cm. Pulse rate is varied from 150 to 225rpm.
Coarse Spiral
In spirals also separation takes place based on specific gravity difference between iron bearing and gangue bearing minerals.
Spirals are made of fiberglass onto which smooth urethane surface is molded to form a trough in the shape of a spiral as the name suggests. Feed slurry is introduced at the top and is subjected to a combination of gravitational and centrifugal forces imparted by its motion down the spiral. This causes high Specific Gravity(SG) minerals to move towards the centre of the trough and water and low SG minerals towards the outside. The segregated slurry discharging from the spiral at the bottom can thus be separated by cutters into high SG (concentrate) and low SG (tailings) together with intermediate SG (middling).
The screen product of -1mm size is subjected to spiral separator to separate the valuable minerals from gangue minerals. In spiral concentrator feed rate is varied from 27.72 to 61.31 lit/min and slurry solid percentage is varied from 25 to 40%. At the product collection end splitters are adjusted and splitter, position is kept 25% away from original position.

Ball mill
50kg capacity batch wise ball mill is used for grinding purpose to liberate iron bearing minerals from gangue minerals. The 28% by total volume of the ball mill is charged with steel balls. Grinding process is carried out on -6+lmm, -3+lmm and -lmm size for both concentrate and tails separately. By checking passing size of the ground material at different interval of time achieved 80% passing -75mic size product for further processing.
Fine spiral
The ground product of -75mic size of gravity separation tails of jig and spiral was mixed properly. The mixed ground product was subjected to spiral concentrator to separate the valuable minerals from gangue minerals. In spiral concentrator feed rate was varied from 27.72 to 61.31 lit/min with 25 to 40% solids. At the product collection end splitters were adjusted and splitter position was kept 25% away from original position.
Hydrocyclone
Hydrocyclone is a continuously operating device that utilises centrifugal force to accelerate the settling rate of particles. This cyclone is used as de-sliming as well as separation purpose. The typical hydrocyclone consists of a conically shaped vessel, open at its apex or underflow, joined to a cylindrical section, which has a tangential feed inlet. The top of the cylindrical section is closed with a plate through which passes as axially mounted overflow pipe. The pipe is extended into the body of the cyclone by a short removable section known as the vortex finder.
The feed is introduced under pressure through the tangential entry which impacts a swirling motion to the pulp. This generates a vortex in the cyclone, with a low pressure zone along the vertical axis, normally connected to the atmosphere through the apex opening, but in part created by dissolved air coming out of solution in the zone of low pressure. The classification theory of hydrocyclone action is that particles within the flow pattern are subjected to two opposing forces - an outward centrifugal force and an inward drag force. The centrifugal force developed accelerates the

settling rate of the particles thereby separating particles according to size, shape, and specific gravity. Faster settling particles move to the wall of the cyclone, where the velocity is lowest, and migrate to the apex opening. Due to the action of drag force, the slower settling particles move towards the zone low pressure along the axis and are carried upward through the vortex finder to the overflow. The commonest method of representing the cyclone efficiency is by partition curve. The cut point or separation size of the cyclone is defined as the size for which 50% of the particles which report to the underflow i.e. particles of this size have an equal chance of going either with the overflow or underflow.
The ground product of gravity separation (Jig and spiral) concentrate and tails are subjected to de-sliming cyclone separately to discard maximum silica minerals as slimes to increase the separation efficiency of further up-gradation process. To achieve d50 cut point between 10 to ISmic selected the cyclone size, vortex finder, spigot, feed pressure and percentage of solids based on the Plitts formula. For de-sliming purpose 75mm hydrocyclone with 25mm vortex finder, 10mm spigot was used. Cyclone was operated with 12% of solids and 30psi pressure to achieve d50 cut point 10 micron.
MIMS
Magnetic separator exploits the difference in magnetic properties between the ore minerals and is used to separate either valuable mineral from non magnetic gangue. Medium intensity magnetic separator (MIMS) is the drum separator widely used for fine material. Permanent magnets are fixed in drum separators. In drum separator separation is by the pick up principle. Magnetic particles are lifted by the magnets and pinned to the drum and are conveyed out of the field, leaving the gangue in the tailing compartment. Water is introduced into the machine to provide a current which keeps the pulp in suspension. Field intensities of 7000 gauss at the pole surface can be obtained in this separator. The feed slurry is fed into the feed box, where by concentrate is carried forward by the drum and passes through a gap, and discharged in to the concentrator collector end. The MIMS is designed for producing extremely clean magnetic concentrate.

In MIMS 7000 gauss magnetic fifed intensity is maintained. The MIMS consist of permanent magnet with fixed magnetic field intensity 7000gauss which cannot be varied. Usually, for magnetite ore one can use low intensity drum magnetic separator but for altered (in between magnetite and hematite) ore medium intensity drum magnetic separator (MIMS). Based on the mineralogica! phase composition one can select the separation process. In the BHQ sample used in the process, the martite (altered phase of magnetite) phase is nearly 21.0%. To process martite the MIMS is more suitable.
Based on the mineralogical characterization studies the de-sliming cyclone underflow of jig and spiral concentrator is subjected to medium intensity drum magnetic separator (MIMS) to separate magnetic concentrate from non magnetic. The magnetic intensity of the magnetic separator is 7000 gauss.
Ball Mill
10kg capacity batch wise ball mill is used for grinding purpose. 28% by total volume of the ball mill is charged with steel balls. Grinding process is carried out on -75mic size combined material of MIMS non magnetic and fine spiral separator concentrate. By checking passing size of the ground material at different interval of time achieved 80% passing -45mic size product for further processing.
Stub cyclone

The stub cyclone is an obtuse angle cyclone and uses water as a medium to separate particles based on specific gravity. This cyclone contains two axial outlets, one at the top and other at the bottom portion. Axial outlet at the top called vortex finder is for lighter particles and the bottom outlet called apex is for heavier particles. Feed slurry enters with pressure at the top portion of the cylindrical body through feed inlet tangential entry which impacts a swirling motion to the pulp. As the particles reach bottom conical portion, heavier particles form a thick and dense bed. The particles having lower density can not penetrate through this bed and are removed through vortex finder at the top portion, The heavier minerals, thus free from liberated low specific gravity gangue minerals report to the apex as an enriched product. The ground sample is subjected to stub cyclone for further Fe up-gradation by removing

silica mineral. In stub cyclone separation studies are carried out using 12.5mm cyclone with 25 mm vortex finder, and 20mm spigot. Cyclone is operated with 20% of solids and 20psi pressure to achieve d50 cut point 14 micron.
Rougher, cleaner and scavenger WHIMS
The Slon vertically pulsating high gradient magnetic separator system is a unique design employing a vertical carousel, straightforward rod matrix system and pulsation mechanism.
An electromagnetic field is generated within the separating zone. A carousel, rotating on its horizontal axis, houses a matrix of parallel rods. From the feed box, slurry is introduced into the matrix as it passes through the separating zone. The magnetic particles in the slurry are attached to the surface of the rods in the matrix. When the magnetizing current supply is removed the magnetic field is negligible, the magnetic materials are flushed into the concentrate box. Conversely, while the matrix is still in the separation zone, gravity and the force of hydrodynamic pulsing of the slurry drag the non magnetic particles through the matrix pile into the tailings box.
In WHIMS, the magnetic field intensity can be varied. So in WHIMS the intensity of magnetic field is adjusted to increase grade or yield. It is necessary to mention the magnetic field intensity. In WHIMS the magnetic field intensity is inversely proportional to product grade and directly proportional to product yield. Following table 2 shows the different Fe grade and yield obtained for different intensities.
Table 2:

Gauss Yield, % Fe, °/o
3000 26.81 62.8
5000 29.25 61.5
7000 31.69 60.8
9000 58.50 58.5
The stub cyclone underflow of MIMS non magnetic is treated in Slon wet high intensity magnetic separator to get pellet grade fines. Here magnetic separation studies are carried out in three stages as rougher and cleaner stage. In rougher stage the magnetic intensity is varied from 1500 to 7000 gauss. In cleaner stage the

Magnetic field intensity : 7000 Gauss Pulsation rate/min : 230 Residence time : 3mins
Cleaner WHIMS (SLON magnetic separator)
Type: Batch scale Magnetic field intensity: 5000 Gauss Pulsation rate/min : 230 Residence time : 3 mins
Scavanger WHIMS (SLON magnetic separator)
Type : Batch scale Magnetic field intensity : 3000gauss Pulsation rate/min : 230 Residence time : 3 mins
In this work the gravity separation (Jig, spiral) tails are further processed selectively using double stage fine spiral separator after size reduction instead of dumping as waste. Further down the flow sheet MIMS non magnetic product and fine spiral separator concentrate are mixed and subjected to grinding process to 80% passing -45 mic to get liberation. The ground product is processed in three stage WHIMS by planning suitable separation sequence.
After processing through jig, spiral, finer spiral, ball mill, hydrocyclone, MIMS, ball mill, stub cyclone and WHIMS, the product (concentrate) having 64.8% Fe and 6.6% Si02 with 42.2% recovery is obtained. Results of BHQ laboratory scale beneficiatton is shown in the following Table 1 indicating the grade and weight percentage of BHQ concentrate.
Table 1:

Description Wt, % Fe, % SiO2, %
Feed 100.0 45.0 35.0
MIMS maqnetic concentrate 16.0 65.5 6.3
WHIMS maqnetic concentrate-1 23.2 64.5 6.7
WHIMS maqnetic concentrate-2 3.0 63.8 6.9
Total concentrate 42.2 64.8 6.6
Tails 57.8 29.2 54.0

It is thus possible by way of the present invention to provide for a cost effective process for BHQ ore beneficiation which can be processed through jig, spiral, finer spiral, ball mill, hydrocyclone, MIMS, ball mill, stub cyclone and WHIMS, so that the product (concentrate) having 64.8% Fe and 6.6% Si02 with 42.2% recovery is achieved. The developed beneficiation flow sheet consists of separation process at coarse size with the combination of jig & spiral followed by finer size (Spiral, MIMS and WHIMS). The generation of ultra fines during grinding process was reduced due to stage-wise beneficiation at coarser fraction (-6+3mm, -3+lmm, and -1mm) followed by finer size (75u and 150u). Magnetic separation was carried out at -45u size using three stage WHIMS, i.e., rougher, scavenger and cleaner WHIMS to recover more iron bearing minerals in concentrate and to reduce the loss of iron bearing minerals in tailing.
Thus by way of the present invention a suitably optimized beneficiation technique for BHQ iron ore at coarser size (-6 mm) using jig and spiral gravity separation has been developed wherein each process step has its own value addition in the optimized beneficiation technique. Importantly, around 85% of iron bearing minerals is liberated below 45u size. Most of the tails are processed in spiral after grinding the material to 80% passing -75u size, whereby superior concentrate grade and higher recovery could be ensured at lower processing cost by the BHQ beneficiation process according to the present invention compared to existing processes known in the filed.

We Claim:
1. A process for beneficiation of medium to high grade banded hematite
quartzite (BHQ) comprising stage wise beneficiation involving :
(i) subjecting the banded hematite quartzite (BHQ) to separation process at coarse size (-6 mm) involving selectively jig and spiral; followed by,
(ii) separation at finer size involving selectively spiral, medium intensity
magnetic separation (MIMS),wet high intensity magnetic separator (WHIMS).
2. A process for beneficiation of medium to high grade banded hematite quartzite (BHQ) as claimed in claim 1 wherein said stagewise beneficiation comprises a first stage beneficiation at coarser fraction comprising -6 + 3mm, -3+1 mm and -1 mm followed by finer size beneficiation involving finer size fractions comprising about 75 u and 45 u.
3. A process for beneficiation of medium to high grade banded hematite quartzite (BHQ) as claimed in anyone of claims 1 or 2 wherein magnetic separation is carried out at 45 p size in three stages of WHIMS involving rougher, scavenger and cleaner WHIMS to thereby recover more iron bearing minerals in concentrate and to reduce the loss of iron bearing minerals in tailings,
4. A process for beneficiation of medium to high grade banded hematite quartzite (BHQ) as claimed in anyone of claims 1 to 3 comprising:
(i) crushing run-of-mine (ROM) sample (size 50 to 150 mm) stage-wise to below 6 mm size and screening the crushed materia! to get -6+3mm, -3+lmm and lmm size fractions ;
(ii) the said -6+3 and -3+lmm size material was separately processed in rougher jig wherein for further extraction of iron bearing minerals from rougher jig tailing, the rougher jig tailing of -6+3mm and -3+lmm were reprocessed separately in scavenger jig to reduce the tailing loss;
(iii) the said -1 mm size material was treated in spiral concentrator and obtained there from concentrate, middling and tailing;

(iv) the overall concentrate obtained from gravity separation process was mixed together and subjected to grinding process to achieve 80% passing -75u size to get liberated iron bearing minerals for further up-gradation;
(v) the ground product of gravity separator concentrator was subjected to desliming cyclone to remove slimes ;
(vi) the de-sliming cyclone underflow was subjected to medium intensity magnetic separator (MIMS) and the magnetic concentrate of the MIMS was obtained as a final product;
(vii) the overall gravity separation tailing was mixed together and subjected to grinding process to achieve 80% passing -75p size to get liberated iron bearing minerals for further up-gradation;
(viii) the ground product of gravity separator tailing was subjected to desliming cyclone wherein the de-sliming cyclone underflow was subjected to two stage spiral concentrator for removing as much as gangue minerals, the concentrate obtained from cleaner spirai was considered for further up-gradation while the middling and tailing of rougher and cleaner spiral was discarded as tailing;
(ix) the spiral concentrate obtained from the processing of gravity separator tailing was mixed with MIMS non-magnetic product, the mixed product was further ground in a ball mill to achieve 80% passing -45u size to get liberation;
(x) the ground product was processed in stub cyclone to remove as much as liberated silica;
(xi) the stub cyclone underflow was processed through rougher, cleaner and scavenger wet high intensity magnetic separator (WHIMS) to obtain two more products while the scavenger stage WHIMS non-magnetic product was treated as tails.
5. A process as claimed in anyone of claims 1 to 4, wherein said processing in jig
carried out involving:
Stroke length 2.04 to 3.75 preferably about 3.75 cm,
Pulsation rate/min - 150 to 225 preferably about 225,
Jigging time - preferably about 5 mins, and
Water flow rate - preferably about 5ltr/min,

6. A process as claimed in anyone of claims 1 to 5, wherein said processing in spiral
carried out involving:
Water flow rate : 27.72 to 61.31 preferably about 45.72 Itr/min, % solids : 25 to 40 preferably about 25, and Splitter position : about 25% from original position
7. A process as claimed in anyone of claims 1 to 6, wherein said processing in De-
sliming cyclone (Hydrocyclone) carried out involving:
Vortex finder diameter: about 25 mm , Spigot diameter : about 10mm, % of solids : 15.3, and Pressure : about 30 psi .
8. A process as claimed in anyone of claims 1 to 7, wherein de-sliming cyclone underflow of jig and spiral concentrator concentrate are subjected to processing in said medium intensity drum magnetic (MIMS) separator to separate magnetic concentrate from non magnetic involving required magnetic intensity preferably of 7000 Gauss.
9. A process as claimed in anyone of claims 1 to 8 , wherein said processing of feed in stub cyclone is carried out involving :
Cyclone size : about 12.5 mm , Vortex finder diameter : about 25 mm, Spigot diameter : about 20 mm, Pressure : about 20 psi, Slurry % of solids : about 20.
10. A process as claimed in anyone of claims 1 to 9, wherein processing of feed in
said Rougher WHIMS (SLOIM magnetic separator) is carried out involving:
Magnetic field intensity : 1500 to 7000 preferably about 7000gauss, Pulsation rate/min : about 230, Residence time : about 3 mins.

11. A process as claimed in anyone of claims 1 to 10 , wherein processing of feed in
said Cleaner WHIMS (SLON magnetic separator) is carried out involving:
Magnetic field intensity : about 5000 gauss, Pulsation rate/min : about 230, Residence time : about 3 mins.
12. A process as claimed in anyone of claims 1 to 11, wherein processing of feed in
said Scavanger WHIMS (SLON magnetic separator) is carried out involving:
Magnetic field intensity: about 3000gauss,
Pulsation rate/min : about 230, Residence time ; about 3 mtns.
13. A process as claimed in anyone of claims 1 to 12, carried out such as to achieve overall product concentrate comprising 63 to 65 % Fe preferably about 64.8% Fe and 5.0 to 7.0 % Si02 preferably about 6.6% Si02 with a recovery level of 40 to 45 % preferably about 42.2% recovery.
14. A process as claimed in anyone of claims 1 to 13, wherein said gravity separation at coarser size involving jig and spiral is suitable for BHQ ore having quartz band width varying from 10mm to less than 1mm.