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 SINTER CHARGE FOR HIGHER PRODUCTIVITY AND A METHOD FOR ITS MANUFACTURE.
2 APPLICANT (S)
Name : JSW STEEL LIMITED.
Nationality : An Indian Company.
Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marq, 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 a process for utilizing blue dust in sinter making. More particularly, the present invention is directed to developing a method for production of desired improved quality of sinter charge by partial utilization of blue dust fines which is a form of very fine-grained powdery ore consisting of loose hematite and magnetite crystals, major part being of less than 0.15mm in size. Advantageously, the present method is capable of utilizing by partial replacement of iron ore fines with blue dust up to 40% in sinter mix with improved properties. The resulting sinter obtained by the process shows total Fe percentage in sinter increased by 2.80%, Alumina percentage decreased by 0.45%, Sinter productivity increased by 0.57 t/m2/day, an increase in Sinter strength by 2.1% and Sinter RDI (less than 3.15mm) decreased by 1.2%.
BACKGROUND ART
It is well known that more than 70% of the iron ore is generated in the form of fines during mining operation. These fines can not be charge directly into Blast Furnace (BF). To make suitable BF feed, it is necessary to agglomerate these fines. It is also known in the art that sintering is an important means of effecting such agglomeration in iron and steel industries. In the sintering process, the fine ore is heated to a temperature of incipient fusion, where small solid particles in contact with one another adhere and agglomerate into larger particles.
The common raw materials used conventionally for sintering process include iron ore fines (less than 10 mm size), fluxes like dolomite and limestone (less than 3mm), coke breeze (less than 3 mm), sinter return fines (less than 5 mm), lime, and steel plant wastes like basic oxygen furnace slag and mill scale.
Increased demand of iron ore for iron and steel industry has resulted into depletion of high grade iron ore reserves. In addition to medium and low grade iron ore fines, there are good deposits of 418 million tons of blue dust in India which mostly remains unused due to its fineness.

Blue dust is the name given to naturally occurring, extremely friable, high grade hematite iron ore powder. Major part of the blue dust is in the form of fines. The Fe content in the blue dust is about 64% or even more. Blue dust cannot be charged in the blast furnace (BF) directly since they block the passage of ascending reducing gas. At present, a fraction of these fines is being used for sinter making and major portion of less than 1 mm fines is dumped and this causes environment problems.
The blue dust is a form of very fine-grained powdery ore consisting of loose hematite and magnetite crystals. Major part of the blue dust is less than 0.15mm in size. The production and quality of the sinter depends on sinter bed permeability, which in turn depends on the raw material size. In order to maintain permeability of the sinter bed, the fine ore fraction (less than 0.15mm) charged in sintering should not be greater than 15%.There has been thus an unresolved limitation in utilizing iron fines or blue dust of very fine sizes in conventional process from permeability consideration of sinter bed and the resultant limitation on quality characteristics of the sinter produced.
There has been therefore a persistent need in the art to developing a method for sinter making which would be capable of utilizing substantially the fine grained blue dust rich in iron content in sinter mix without affecting the desired performance in terms of permeability and productivity of the sinter bed. The process of the present invention would also favour production of desired quality of sinter by partial utilization of blue dust fines thus eliminating dumping of unused fines and related environmental hazard and also saving scarce natural resource.
OBJECT OF THE INVENTION
The basic object of the present invention is thus directed to a process for production of improved quality sinter charge by utilization of blue dust in higher proportion in sinter mix for sinter making.

A further object of the present invention is directed to a process for sinter making by utilization of blue dust of less than 0.15mm size in substantial quantity by partial replacement of conventional charge in sinter mix.
A still further object of the present invention is directed to a process for sinter making by utilization of blue dust which would not affect the required permeability of sinter bed due to presence of fines.
A still further object of the present invention is directed to a process for sinter making by utilization of blue dust which would ensure desired improved quality of sinter produced with increased Fe content, increased strength and reduced RDI.
A still further object of the present invention is directed to a process for sinter making by utilization of blue dust which permits the use of low grade iron ore fines along with blue dust in sinter making.
A still further object of the present invention is directed to a process for sinter making by utilization of blue dust which is capable of reducing environmental hazard due to dumping of fines and ensure resource conservation.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a sinter charge for higher productivity comprising:
iron ore fines in combination with blue dust in an amount of upto 80% by wt.
A further aspect of the present invention is directed to a sinter charge comprising (a) iron ore fine based granules obtained of iron ore fines, fluxes, coke breeze, sinter return fines and lime and (b) blue dust based pellets.
A still further aspect of the present invention is directed to said sinter charge wherein said granules comprise fluxes, iron ore fines, sinter return fines and 0.20 to 1% lime

and coke breeze (1.2 to 5.8%) and said pellets comprise green pellets 100% less than 0.15 mm blue dust and 0.20 to 1% lime.
Importantly, in said sinter charge, said green pellets are coated with 0.9 to 5.8% coke breeze.
Advantageously, in said sinter charge according to the present invention, the mean particle size of the sinter charge is in the range of 3.2 to 5.6 mm,
A still further aspect of the present invention is directed to a sinter charge that comprises the following properties:
Fe : in the range of 53.8 to 58.42 Al203 : in the range of 2.29 to 3.21
According to yet another aspect of the present invention directed to a method for the production of sinter charge described herein before comprising
preparing the sinter charge in a mixer involving granulation of iron ore fines and peptization of blue dust fines to thereby obtain sinter charge of desired particle size for sinter making ensuring desired sinter bed permeability.
A still further aspect of the present invention is directed to said method comprising the steps of
(i) providing iron ore fines, fluxes, sinter return fines and lime in the range of 0.20 to 1% and coke breeze in the range of 1.2 to 5.8% for preparing granules in granulation drum and maintaining moisture in the range of 7.5 to 8.0% preferably 8%;
(ii) providing 100% less than 0.15 mm size blue dust with lime in the range of 0.20 to 1% for preparing pellets in balling disc and maintaining moisture in the range of 7.5 to 8.0% preferably 8%.
(iii) coating the green pellets so prepared with 0.9 to 5.8% coke breeze; and

(iv) finally mixing the blue dust pellets and iron ore fines granules in a drum mixer to get uniform feed of the sinter charge with mean particle size in the range of 3.2 to 5.6 mm, for sinter making.
A still further aspect of the present invention is directed to a method for the
production of improved quality sinter wherein size of blue dust and iron ore fines
comprising
Size, mm : +10 +8 +6 +3 +1 +0.15 -0.15
Blue dust( %) : 0.0 0.0 0.2 0.8 3.0 7.0 89.0
Iron ore fmes( %): 4.8 6.8 8.2 16.0 12.1 23.2 29.0
Yet another aspect of the present invention is directed to a method for the production of improved quality sinter wherein composition of blue dust and iron ore fines comprise
Fe(t) AI203 SiOz CaO MgO C LOI
Blue dust(wt%) 66.2 0.91 1.08 0.08 0.01 - 1.82
Iron ore fines(wt%) 62.8 2.80 4.59 0.13 0.02 - 3.00
A still further aspect of the present invention is directed to a method for the production of improved quality sinter wherein up to 40% of the total iron bearing material is substituted by blue dust addition to favour improved sinter properties comprising
Fe(total):56.6%, Al203: 2.76 %, Productivity: 41.8 t/m2/day, Mean size: 17.19mm, T.I (+6.3mm): 72.8 %, RDI (-3.15mm): 22.7 % .
A still further aspect of the present invention is directed to a method for the production of improved quality sinter comprising using low grade iron ore fines along with blue dust in sinter making favouring resource conservation.
The objects and advantages of the present invention is described ingreater details with reference to the following accompanying non limiting drawings and examples.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : is the schematic illustration of the conventional sinter plant used for sinter making process.
Figure 2: is the flow process chart showing the steps involved in sinter mix preparation in laboratory pot sinter making facility by utilizing fine grained blue dust substituting conventional charge.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
The present invention is directed to developing a method for production of desired improved quality of sinter charge by partial utilization of blue dust fines which is a form of very fine-grained powdery ore consisting of loose hematite and magnetite crystals, major part being of less than 0.15mm in size, without affecting the permeability of the sinter bed.
Reference is first invited to the accompanying Figure 1 which illustrates schematically the assembly of conventional sintering plant showing its different components. In the sintering process, the fine ore is heated to a temperature of incipient fusion, where small solid particles in contact with one another adhere and agglomerate into larger particles. It can be seen from Figure 1 that each pallet car (3) moves under a charging hopper(l) from which the sinter mix is loaded. The common raw materials for sintering process are iron ore fines (less than 10 mm size), fluxes like dolomite and limestone (less than 3mm), coke breeze (less than 3 mm), sinter return fines (less than 5 mm), lime, and steel plant wastes like basic oxygen furnace slag and mill scale. Then mix charge then passes under a burner/ ignition hood(2), which ignites the surface of the bed at 1150 to 1200°C. The pallet(4) moves over a suction system, which draws a continuous stream of air(5) through the top of the bed. Suction pressure of less than 170 mbar is maintained by operating the exhaust fan till the completion of sintering which is known from the

temperature of the wind box (burn through point). The pallet car moves from feed end to discharge end and during this period various physico-chemical phenomena take place and different phases are formed based on chemical composition of the material and temperature. After completion of the process at the discharge end (8), the sinter-breaker breaks the sinter cake and broken sinter lumps are fed to the cooler. Inside the cooler, different mineral phases crystallize and gets bonded together to form strong sinter, which is desirable for a BF feed.
Major part of the blue dust is in the form of fines, a form of very fine-grained powdery ore consisting of loose hematite and magnetite crystals. The Fe content in the blue dust is about 64% or even more. However the iron rich Blue dust cannot be charged in the blast furnace (BF) directly since they block the passage of ascending reducing gas. Moreover, major part of the blue dust being of less than 0.15mm in size, it tends to affect the permeability of sinter bed in conventional sintering process. In order to maintain permeability of the sinter bed, the fine ore fraction (less than 0.15mm) charged in sintering should not be greater than 15%. The conventional sintering process allowed only a fraction of these fines to be used for sinter making and niajor portion of less than 1 mm fines is dumped which causes environment problems.
The objects and advantages of the present invention are illustrated with the help of following exemplary experimental illustration.
EXAMPLE I:
According to an embodiment of the present invention. Sintering experiments have been carried out in laboratory pot sinter making facility, by partial replacement of iron ore fines with blue dust from 0 to 80% in sinter mix.
Following Table 1 shows the typical chemical analysis of blue dust and iron ore fines used for sinter making.

Table 1

Material Wt, %

Fem Al203 SiOz CaO MgO c LOI
Blue dust 66.2 0.91 1.08 0.08 0.01 1.82
Iron ore fines 62.8 2.80 4.59 0.13 0.02 3.00
Following Table 2 shows the typical size analysis of blue dust and iron ore fines used for sinter making.
Table 2

Raw material + 10 +8 + 6 + 3 + 1 + 0.15 -0.15

Size, mm
Blue dust 0.0 0.0 0.2 0.8 3.0 7.0 89.0
Iron ore fines 4.8 6.8 8.2 16.0 12.1 23.2 29.0
The present invention provides a process for sinter making by utilizing the blue dust of less than 0.15mm size in higher proportions substituting the conventional charge while also avoiding the problem relating to sinter bed permeability.
Accompanying Figure 2 illustrates the flow process chart showing the different steps involved in sinter mix preparation according to the present invention.
In this study, sinter mix consists of mixture of iron ore fines granules and blue dust pellets. Granules are prepared in granulation drum using fluxes, iron ore fines, sinter return fines and 0.20 to 1% lime and coke breeze (1.2 to 5.8%). Pellets are prepared in balling disc using 100% less than 0.15 mm blue dust and 0.20 to 1% lime. The prepared green pellets are then coated with 0.9 to 5.8% coke breeze. In both granulation and peptization process, 8% moisture has been maintained. The mean particle size of the sinter charge is in the range of 3.2 to 5.6 mm. Finally, blue dust pellets and iron ore fines granules are mixed in a mixer to get uniform feed for sinter making.
Sinter mix preparation for sinter making consisting of mixture of iron ore fines granules and blue dust pellets according to the present invention, carrying out

sintering experiments by partial replacement of iron ore fines with blue dust from 0 to 80% in sinter mix, thus comprised the steps of
(i) preparing granules in granulation drum using iron ore fines, fluxes, sinter
return fines and lime in the range of 0.20 to 1% and coke breeze in the
range of 1.2 to 5.8% and maintaining moisture in the range of 7.5 to
8.0% preferably 8%; (ii) preparing pellets in balling disc using 100% less than 0.15 mm size blue
dust with lime in the range of 0.20 to 1% and maintaining moisture in the
range of 7.5 to 8.0% preferably 8%. (iii) coating the green pellets so prepared with 0.9 to 5.8% coke breeze; and (iv) finally mixing the blue dust pellets and iron ore fines granules in a mixer to
get uniform feed with mean particle size of the sinter charge in the range
of 3.2 to 5.6 mm, for sinter making.
It is observed through experimentation as detailed above that Sinter with 40% blue dust achieved higher productivity and higher strength with lower RDI. The properties of sinter achieved following the present process are as shown in following Table 3. The addition of blue dust in sinter mix decreased the limestone addition and improved the overall sinter Fe content. It also reduced the sinter alumina. On the basis of experimental results, up to 40% of the total iron bearing material has been substituted by blue dust addition. The above laboratory trial is adapted to be scaled up for actual plat scale operation with identical benefits.
Table 3

Properties Blue dust, °/o

0 20 40 60 80
Fe (Total) 53.8 54.90 56.60 57.53 58.42
Al203, % 3.21 2.99 2.76 2.53 2.29
Productivity, t/m2/day 41.23 41.90 41.80 37.90 35.80
Mean size, mm 15.40 17.34 17.19 17.13 16.17
T.I (+6.3mm), % 72.0 73.0 72.8 63.3 57.7
RDI (-3.15mm), % 23.9 23.0 22.7 30.2 34.4

The following distinct advantages are thus derived according to the process of sinter production by way of the present invention:
-Total Fe percentage in sinter increased by 2.80%.
-Alumina percentage in sinter decreased by 0.45%.
-Sinter productivity increased by 0.57 t/m2/day.
-Sinter strength increased by 2.1%.
-Sinter RDI (less than 3.15mm) decreased by 1.2%.
-Effective utilization of blue dust (minus 0.15 mm) generated from mining process.
-Permits the use of low grade iron ore fines along with blue dust in sinter making
which is extremely important from resource conservation and utilization point of
view.

We Claim:
1. A sinter charge for higher productivity comprising:
iron ore fines in combination with blue dust in an amount of up to 80% by wt.
2. A sinter charge as claimed in claim 1 comprising (a) iron ore fine based granules obtained of iron ore fines, fluxes, coke breeze, sinter return fines and lime and (b) blue dust based pellets.
3. A sinter charge as claimed in claim 2 wherein said granules comprise fluxes, iron ore fines, sinter return fines and 0.20 to 1% lime and coke breeze (1.2 to 5.8%) and said pellets comprise green pellets 100% less than 0.15 mm blue dust and 0.20 to 1% lime.
4. A sinter charge as claimed in claim 3 wherein said green pellets are coated with 0.9 to 5.8% coke breeze.
5. A sinter charge as claimed in anyone of claims 1 to 4 wherein the mean particle size of the sinter charge is in the range of 3.2 to 5.6 mm.
6. A sinter charge as claimed in anyone of claims 1 to 5 comprising the following properties:
Fe : in the range of 53.8 to 58.42 A1203 : in the range of 2.29 to 3.21
7. A method for the production of sinter charge as claimed in anyone of claims 1 to 6
comprising
preparing the sinter charge in a mixer involving granulation of iron ore fines and pelletization of blue dust fines to thereby obtain sinter charge of desired particle size for sinter making ensuring desired sinter bed permeability.

8. A method as claimed in claim 7 comprising the steps of
(i) providing iron ore fines, fluxes, sinter return fines and lime in the range of
0.20 to 1% and coke breeze in the range of 1.2 to 5.8% for preparing
granules in granulation drum and maintaining moisture in the range of 7.5
to 8.0% preferably 8%; (iii) providing 100% less than 0.15 mm size blue dust with lime in the range
of 0.20 to 1% for preparing pellets in balling disc and maintaining
moisture in the range of 7.5 to 8.0% preferably 8%. (iii) coating the green pellets so prepared with 0.9 to 5.8% coke breeze; and (iii) finally mixing the blue dust pellets and iron ore fines granules in a drum
mixer to get uniform feed of the sinter charge with mean particle size in
the range of 3.2 to 5.6 mm, for sinter making.
9. A method for the production of improved quality sinter as claimed in any one of
claims 7 or 8 wherein size of blue dust and iron ore fines comprising
Size, mm : +10 +8 +6 +3 +1 +0.15 -0.15
Bluedust(%) : 0.0 0.0 0.2 0.8 3.0 7.0 89.0
Iron ore fmes( %): 4.8 6.8 8.2 16.0 12.1 23.2 29.0
10. A method for the production of improved quality sinter as claimed in any one of
claims 7 to 9 wherein composition of blue dust and iron ore fines comprising
Fe(t) A1203 Si02 CaO MgO C LOI
Blue dust(wt%) 66.2 0.91 1.08 0.08 0.01 - 1.82
Iron ore fines(wt%) 62.8 2.80 4.59 0.13 0.02 - 3.00
11. A method for the production of improved quality sinter as claimed in any one of
claims 7 to 10 wherein up to 40% of the total iron bearing material is substituted by
blue dust addition to favour improved sinter properties comprising
Fe(total):56.6%, Al203: 2.76 %, Productivity: 41.8 t/m2/day, Mean size: 17.19mm, T.I (+6.3mm): 72.8 %, RDI (-3.15mm): 22.7 % .

12. A method for the production of improved quality sinter as claimed in any one of
claims 7 to 11 comprising using low grade iron ore fines along with blue dust in
sinter making favouring resource conservation.
13. A sinter charge for higher productivity and a method for its manufacture
substantially as herein described with reference to accompanying figures.