Claims:WE CLAIM:

1. A process for producing high purity Fe2O3 for value-added applications including blast furnace feed from a poor-grade iron ore slime, comprising the steps of:
- pumping the slime in slurry form to undergo hydro cyclone for size separation to produce coarser concentrate in its underflow;
- pumping the underflow as second concentrate slurry to undergo stub cyclone with gravity separation in the form of second tailing.

2. The process as claim in claim 1, wherein the process is configured for recovery of iron ore particles with 63% Fe are being recovered from slime with 57% Fe with
20 t/hr production of iron ore of good quality.

3. The process as claim in claim 1, wherein under hydro cyclone includes a cluster of 24 numbers of cyclones and the finer particles of size of less than 20 µm get discarded to the overflow.

4. A system for producing high purity Fe2O3 for value-added applications including blast furnace feed from a poor-grade iron ore slime, comprising:
a plurality of slurry pumps configured for pumping slurry;

a hydro-cyclone configured for discarding less than 20 micron particles from the feed as iron ore slime;
a stub cyclone configured for gravity separation unit apart from size separation for effective and final beneficiation; and
a plurality of pinch valves operably connected with pumps for smooth flow of slurry.

5. A system as claim in claim 4, wherein the system is configured for recovery of iron ore particles with 63% Fe are being recovered from slime with 57% Fe with 20 t/hr production of iron ore of good quality.

6. A system as claim in claim 4, wherein under hydro cyclone includes a cluster of

24 numbers of cyclones and the finer particles of size less than 20 µm get discarded to the overflow.

Dated: this 17th day of February, 2016.

(N. K. Gupta) Patent Agent, Of NICHE,
For SAIL.

To,
The Controller of Patents, The Patent Office, Kolkata.
, Description:A PROCESS AND SYSTEM FOR THE BENEFICIATION OF SLIME PRODUCED THROUGH IRON ORE PROCESSING

FIELD OF INVENTION

The present invention relates to the process and system for beneficiation of slime produced through Iron Ore Processing. 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 and size separation purposes and the underflow of these cyclones is treated through cluster of stub hydro- cyclones for gravity separation.

PRIOR ART

Bolani Ores Mine under Raw Materials Division of Steel Authority of India Limited presently processes 5.5 million ton per annum (mtpa) of iron ore beyond its installed capacity of 4.2 mtpa. The processing plant has two circuits i.e. dry circuit for processing of Direct Ore (DO) and wet circuit for processing of lower grade or beneficiable Ore (BO). The DO circuit has two lines. It consists of two feed bins of
300 ton each, belt feeder with variable speed and a double deck vibrating screen of

40 mm and 10 mm size. The products of size between 10 mm and 40 mm are lump and of size less than 10 mm are fines. The beneficiable Ore (BO) circuit also has two processing lines consisting of two feed bins of 300 ton each, belt feeder with variable speed which feeds to double deck screen through launders having top deck and bottom deck openings of 40 mm and 8 mm respectively. Plenty of water is used in the launder to make flow-ability of ore. The lump is conveyed to lump loading plant whereas the fines is fed to screw classifier having cut size of 150 µm for further beneficiation. The classifier sands (product) of size between 0.15 mm and 8 mm are de-watered by a de-watering screen having opening of 0.15 mm. These fines are the sinter feed and are taken to fines loading plant. The classifier overflow of size less than 0.15 mm and the residue of de-watering screen of same size are called slime. Slime is treated as waste material of washing plant and is sent to the thickener. The thickener overflow flows to a process water reservoir for recycling to the ore beneficiation/processing plant. The thickener underflow, having about 20% solid, flow by gravity to the tailing pond.

Iron ore are beneficiated all over the world for which several techniques are being used namely spiral, floatex density separators, jigs, multi-gravity separator, low and high intensity magnetic separator, flotation, selective dispersion and flocculation and many more with advanced technologies. Iron ore production entails generation of fines (10-25%) containing high alumina (6-8%), which is unsuitable for direct use in the blast furnace. Assuming an annual production of 150 million tons of iron ore, the iron values to the tune of 15- 25 million tonnes is lost every year. The main drawback for use of iron ore ultra fines is that high level of clay is associated with it. As a consequence, this ultra fines being rejected and getting wasted causing environmental hazards. The particle size of these ultra fines is not suitable to beneficiate it by known beneficiation processes such as (i) gravity or (ii) magnetic separation.

The slime generated from washing plant is sent to the thickener and tailings pond and thus losing 57-60 % Fe. The generation of slime is increasing with higher wet operation which is necessary for stringent quality requirement of sized ore at steel plants. Moreover, the slime having 57-60 % Fe cannot be discarded as per the IBM’s guidelines. The metal value in the reject process should not have more than
45% Fe content.

OBJECT OF THE INVENTION

It is therefore an object of the invention to propose a process for producing high purity Fe2O3 for value added application and blast furnace feed from a poor grade iron ore slime , which eliminates the prior art disadvantages. Another object of the invention is to propose a process for producing high purity Fe2O3 for value added application and blast furnace feed from a poor grade iron ore slime, which provides a first grade of product containing only very low amount of alumina and silica adaptable for high-valued product or blast furnace feed.

A further object of the invention is to propose a process for producing high purity Fe2O3 for value added application and blast furnace feed from a poor grade iron ore slime, which provides a second grade of product containing high alumina and silica suitable for making building or refractory material.

SUMMARY OF THE INVENTION

According to the invention, the present invention is focused on treatment of underflow of the conventional cyclone assaying above mentioned composition through stub cyclone, the yield is 37% but the quality of the concentrate obtained is
~63% Fe, 2.6% SiO2 and 2.98% Al2O3. Therefore such as herein described a process for producing high purity Fe2O3 for value-added applications including blast furnace feed from a poor-grade iron ore slime. It comprises the steps of pumping slime to conventional hydro-cyclone to get the first concentrate through the underflow, which is then again pumped to Stub hydro-cyclone to produce high grade concentrate.

Further there is provided a system for producing high purity Fe2O3 for value-added applications including blast furnace feed from a poor-grade iron ore slime, comprising : a plurality of slurry pumps configured for pumping slurry; a hydro- cyclone configured for discarding less than 20 micron particles from the feed and iron ore slime; a stub cyclone configured for gravity separation unit apart from size separation for effective and final beneficiation; and a plurality of pinch valves operably connected with pumps for smooth flow of slurry.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig. 1 illustrates a schematic representation of the online slime beneficiation system at Bolani mines in accordance with the present invention;

Fig. 2 shows a pictorial view of the online slime beneficiation system at Bolani mines in accordance with the present invention.

DETAILED DESCRIPTION

As there was no facility for beneficiation of slime, an innovative system has been conceptualized and implemented in an open space adjacent to the existing ore processing plant. Based on the above findings, total system was designed with equipment specification and was implemented at Bolani mines. The schematic representation of the entire system is shown in Fig. 1.

The broad objective of the present work is for the introduction of a new online slime beneficiation system by incorporating two types of hydro-cyclones in series for recovery of valuable minerals from the process rejects and also to improve the overall quality of sinter fines product being produced in this mine. This innovative work also focused in treating slime, which otherwise are directed to tailing pond. The tailing pond of mines is almost full with ~ 5 Mt slime and unless a system of slime beneficiation is introduced, the mines operation may stand still within 2-3 years. In the present work, process parameters have been optimized for slime beneficiation system to maximize yield of concentrate (20 t/hr) at alumina level less than 3%. The disclosed system is employed for recovering the valuable iron mineral particles from the process reject. Advantageously, the process of the present invention is capable to recover iron mineral particles with 63% Fe grade with less than 3% alumina from slime with 56% Fe and 6% alumina at a rate of around 20 t/hr making the process suitable for wide industrial application with significant cost advantage.

In the iron ore mines, the slime is generated through processing of iron ore fines in screw classifiers i.e. classifier overflow. As shown in Fig 1, the system consists of Slurry Pump no.1, connected with first phase Hydro-cyclone and a Slurry Pump no.2 connected with Stub Hydro-cyclone. During operation the Slurry pump no. 1 is connected to the Hydro-cyclone which is further connected to Slurry Pump no .2 to Stub Hydro-cyclone such that the waste slime from Hydro-cyclone is further treated with stub Hydro-cyclone.

Functions of the Components:

Slurry Pump No. 1: This pump is having capacity of 500 m3/hr and can handle up to

20% solid. It takes the slurry from the process reject and pumps to conventional hydro-cyclone at a pressure of 30 psi.
Conventional Hydro-Cyclone: There is a cluster of 24 numbers of cyclones. This is a size separation unit. The finer particles of size of 15-20 µm get discarded to the overflow i.e. iron ore slime gets partially beneficiated here. This cyclone creates the avenue for better beneficiation in the subsequent stage.
Slurry Pump No. 2: This pump is having capacity of 300 m3/hr. It takes the feed

from the conventional hydro-cyclone underflow (coarser particles) and pumps to the

Stub cyclone for effective and final beneficiation. The cyclone pressure can be varied from 15-30 psi.
Stub cyclone: This is a gravity separation unit apart from size separation. As the finer particles have already been removed in the first stage of beneficiation by conventional hydro-cyclone, the effectiveness of gravity separation in this cyclone gets enhanced.

Working Principle of the Invention:

Slurry Pump no.1 takes the slurry from the process reject launder and pumps the slurry to the conventional hydro-cyclone.
This hydro-cyclone discards less than 20 micron particles from the feed and iron ore slime gets partially beneficiated.
Slurry Pump no.2 pumps partially beneficiated relatively coarser particles to stub cyclone which is a gravity separator.
The partially beneficiated slime gets finally beneficiated by the stub cyclone whose underflow is beneficiated product for use in steel plant.
The individual equipments i.e. Slurry pump with motor, Hydro-cyclones, Pinch valves were procured and installed to make a perfect and smoothly operative online system. After implementation, samples were drawn at various points and analyzed. The pictorial view of the innovative online slime beneficiation system is shown in Fig. 2.

The present innovation aims to recover fines concentrate of >63 % Fe content from part of on-line slime of 57-60 % Fe and reject mineral with 45 % Fe by setting up a slime beneficiation plant of 100 tph solid throughput, dovetailing the existing classifier operation.

Experimental Observations

The processing plant of Bolani mines was studied in detail and performance data were collected. The representative slime samples were collected for in-depth investigation at RDCIS laboratory. The samples were analyzed using DTA/DTG, XRD, mineralogical microscope and XRF equipment. After characterization of the slime sample, bench scale beneficiation tests were carried out using both conventional hydro-cyclone and stub hydro-cyclone. Representative sample of slime coming out from washing plant of Bolani ore mines was collected from the

launder before entering into thickener. Physical and chemical characterizations were carried out in RDCIS laboratory. Handsome quantity of slime sample keeping
15% solid in the feed was prepared and passed at 10 psi and 15 psi pressure through conventional hydro cyclone with 15 mm apex and 25 mm vortex for de- sliming and size separation. Chemical and granulometry tests of under flow and over flow particles were conducted separately. Again the under flow material passed at 15 psi was prepared as feed for stub hydro cyclone, maintaining 15% solid and passed through it at 15 psi pressure for gravity separation. Chemical and granulometry tests of under flow and over flow particles were conducted.

EVALUATION

Plant operation data after innovation

= 20t/hr for 8 hrs/day x 2 shifts

= 320 tons/day

Considering 300 working days of operation in a year

= 96000 ton per annum

Considering cost of production of ore fines @ Rs 373.00 per ton,

Annual benefit due to extra production of fines = 9600 x 373 = Rs 35.808 lakh per annum
[Slime beneficiation system is being operated in only one shift at product rate of

20 t/hr]

INVENTIVE STEP:

a) Development of a smooth and trouble free system with an online slime beneficiation rate of 500 m3/hr.
b) Design, fabrication and installation of an online slime beneficiation system by incorporating two types & stages of hydro-cyclone only. Actually Bolani slime contains higher amount of micro-fines (size < 20 µm) having mainly alumina particles. So a circuit has been developed to discard these micro-fines at first by a de-sliming cyclone, which helps an avenue for better beneficiation (gravity separation) in the stub-cyclone followed.
c) By the implementation of this technology the alumina in recovered fines gets reduced to 2.98% from 5.8 %.
d) By this innovative technology iron ore particles with 63% Fe are being recovered from slime with 57% Fe.

e) By the application of this technology, quality of fines resulted in improvement from approximately 4.95% to 2.6% SiO2.
f) This system is able to recover around 20 t/hr (i.e. 0.096 Mt/annum) iron ore of

good quality.

g) This slime beneficiation system has an impact in increasing mineral conservation and reducing a greater degree of environmental pollution.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.