Claims:We Claim:

1. An iron ore sintering composition including iron ore fines suitable for blast furnace iron making comprising:

50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of iron ore having particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of micro pellets as steel plant wastes and 1.5-2.0% of direct reduced iron fines; and moisture content in the range of 7.5-8% by wt.

2.The iron ore sintering composition as claimed in claim 1 wherein the iron ore comprises 50-55% of iron ore having particle size of -10 mm or less, and 30-40% of particle size of 150 µm or less, 0-55% of washed ore having particle size of -3 mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98 % of beneficiation plant concentrate having particle size of 150 µm or less favouring sinter characteristics including iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 67.0-69.7%, shatter index (+10 mm) is 68.4-70.1% and reduction degradation index (+3.15 mm) is 22.0-25.5%.

3. The iron ore sintering composition as claimed in anyone of claims 1 or 2 wherein iron ore fines include 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%; washed ore include 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3 and loss on ignition is 3-4%; sinter return fines include 50-52.5% Fe, 4.8-5.70% of SiO2 and 4.2-4.5% of Al2O3; limestone include 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42%; dolomite include 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45%; coke breeze include 76-80% of carbon; micro pellet include 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56-15.5% of carbon and loss on ignition is 16.63-17.5%; iron ore fines include 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4.3%; and direct reduced iron fines include 85-87% of Fe.

4.A method of manufacturing iron ore sinter with improved strength involving iron ore sintering composition as claimed in claim 1 comprising the following steps:
providing the iron ore sintering composition comprising 50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of iron ore having particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of pellets as steel plant wastes and 1.5-2.0% of direct reduced iron fines and with moisture content in the range of 7.5-8% by wt.;

granulating the thus obtained iron ore sinter composition to obtain granules having particles size in the range of 2.44-3.10 mm, wherein the granules granulation index is 3.1-2.44 and balling index is 3-2.55;

igniting the granules;

and sintering the granules to obtain the iron ore sinter, wherein the iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 67.0-69.7%, shatter index (+10 mm) is 68.4-70.1% and reduction degradation index (+3.15 mm) is 22.0-25.5%.

5. The method as claimed in claim 4, wherein the iron ore sinter composition included 50-55% of iron ore fines having particle size of -10 mm or less and 30-40% of iron ore fines having particle size of 150 µm or less, 0-55% of washed ore having particle size of -3 mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98 % of beneficiation plant concentrate having particle size of 150 µm or less.

6. The method as claimed in anyone of claims 4 or 5 , wherein said step of igniting the granules is carried out with ignition suction in the range of 600-700 mmH2O and at an ignition temperature of 1150-1160oC.

7.The method as claimed in anyone of claims 4 to 6 wherein said step of sintering the granules is carried out with sintering suction in the range of 1200-1300 mmH2O.

8. The method as claimed in anyone of claims 4 to 7 wherein the basicity of the iron ore sinter is maintained in the range of 1.8-2.20% and the mass percentage of MgO in the iron ore sinter is maintained in the range of 2.0-2.40%.

9. The method as claimed in anyone of claims 4 to 8 wherein the mass percentage of coke breeze is maintained in the range of 58-60 kg/t and carbon rate of the coke breeze is maintained in the range of 48-49.5 kg/t.

10. The method as claimed in anyone of claims 4 to 9 carried out with sinter bed permeability in the range from 52.3-45.5 JPU.

11. The method as claimed in anyone of claims 4 to 10 wherein said sintering composition include iron ore fines comprising 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%; washed ore comprising 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3 and loss on ignition is 3-4%; sinter return fines comprising 50-52.5% Fe, 4.8-5.70% of SiO2 and 4.2-4.5% of Al2O3; limestone comprising 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42%; dolomite comprising 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45%; coke breeze comprising 76-80% of carbon; pellet comprising 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56-15.5% of carbon and loss on ignition is 16.63-17.5%; iron ore fines comprising 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4.3%; and direct reduced iron fines comprising 85-87% of Fe enabling selectively providing desired iron ore sinter suitable for use in blast furnace with essential sinter components by weight percentage iron 53.6-53.0%, FeO 10.21-9.37% and CaO 11.26-11.55%.

Dated this the 5th day of September, 2020
Anjan Sen
Of Anjan Sen & Associates
(Applicants’ Agent)
IN/PA-199

, Description: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 :
AN IRON ORE SINTERING COMPOSITION AND A METHOD OF MANUFACTURING IRON ORE SINTER WITH IMPROVED STRENGTH USING FINES.



2 APPLICANT (S)

Name : JSW STEEL LIMITED.

Nationality : An Indian Company incorporated under the Companies Act, 1956.

Address : JSW CENTRE,
BANDRA KURLA COMPLEX,
BANDRA(EAST),
MUMBAI-400051,
MAHARASHTRA,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 an iron ore sintering composition including iron ore fines suitable for blast furnace iron making and a process of manufacturing agglomerates from iron ore sintering composition including fines. More particularly, the invention relates to a method to improve the strength of the iron ore sinter using fines (i.e. includingless than 150 micron particles).

BACKGROUND OF THE INVENTION

Sinter is a prepared burden which constitutes the major proportion of feed to the blast furnace. Sinter is formed when a certain portion of iron ore is mixed in defined proportions with coke/coalfines and other additives, the mixture is subjected to high temperatures derived from the combustion of coke or coalfines, and it is agglomerated by incipient fusion of the particles of ore to form solid sinter particles having considerable porosity, sufficient strength for handling and transportation and mechanical resistance. These sinter particles are ideal for the feeding to blast furnace for iron making.

The size range of the iron ore used in the sintering process is, however, limited in its lower range (below 8 mm). In particular iron ore having more than 40% of its particles with a size below 150 microns is unacceptable for this purpose because of the risk of attaining an economically unacceptable yield in the process of sintering. For fines sintering raw mixes with a high proportion of fines (<150 µm) deteriorates the operation of the Dwight-Lloyd sinter machine. The low yield is due to the obstruction by the fine ore particles of the passage of the gases necessary for the combustion of the coke or coal. Therefore, a large number of iron ore mining companies are facing with the problem of disposing of considerable stocks of ore fines (i.e., ore with a substantial proportion of particle sizes below 150 microns) which cannot be used for sintering.

The influences of chemistry and physical propertiesof iron ore fines have been investigated by many researchers. For example, patent application KR20200035767 relates to a pulverized ore granule for sinter ore production, a method for manufacturing the same, and a pre-treatment method for a sintered compound raw material comprising the same. More specifically, coke dust and calcined lime sludge are added as additives to improve sintered ore granules for sintered ore manufacturing, and methods for manufacturing the same and pre-treatment methods for sintered raw materials including the same.

Similarly, due to huge availability of iron ore fines, it is extremely desirable to increase the utilization of iron ore fines as a sintering raw material. So there has been a continuous endeavour to include increase in utilization of fine iron ores.

However, there is a need for a process which allows for the use of iron ore fines with particle size ranges below 150 microns in the conventional sintering process.

OBJECT OF THE INVENTION

The main object of the present invention is thus to provide a method for making sinter through iron oxide fines, which obviates the drawbacks as mentioned above.

It is an object of the present invention to optimize the iron ore fines in sinter mixture to achieve the better sinter properties for blast furnace iron making unit.

It is an object of the invention to provide a use of fine iron ore in the form of a high strength sinter.

In short, the purpose of the present invention is to propose a new method that can maintain the quality as iron ore sinter for a blast furnace and increase the strength more than before even when a large amount of the fine iron ore is used.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to an iron ore sintering composition including iron ore fines suitable for blast furnace iron making comprising:

50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of steel plant wastes and 1.5-2.0% of direct reduced iron fines; and moisture content in the range of 7.5-8% by wt.

A further aspect of the present invention is directed to said iron ore sintering composition wherein the 50 – 55% of iron ore comprises of particle size of -10 mm or less and 30-40% particle size of 150 µm or less, 0-55% of washed ore having particle size of -3 mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98 % of beneficiation plant concentrate having particle size of 150 µm or less favouring sinter characteristics including iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 67.0-69.7%, shatter index (+10 mm) is 68.4-70.1% and reduction degradation index (+3.15 mm) is 22.0-25.5%.

A still further aspect of the present invention is directed to said iron ore sintering composition wherein iron ore fines include 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%; washed ore include 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3 and loss on ignition is 3-4%; sinter return fines include 50-52.5% Fe, 4.8-5.70% of SiO2 and 4.2-4.5% of Al2O3; limestone include 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42%; dolomite include 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45%; coke breeze include 76-80% of carbon; pellet include 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56-15.5% of carbon and loss on ignition is 16.63-17.5%; iron ore fines include 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4.3%; and direct reduced iron fines include 85-87% of Fe.

Another aspect of the present invention is directed to a method of manufacturing iron ore sinter with improved strength involving iron ore sintering composition as claimed in claim 1 comprising the following steps:
providing the iron ore sintering composition comprising 50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of iron ore having particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of as steel plant wastes and 1.5-2.0% of direct reduced iron fines and with moisture content in the range of 7.5-8% by wt.;

granulating the thus obtained iron ore sinter composition to obtain granules having particles size in the range of 2.44-3.10 mm, wherein the granules granulation index is 3.1-2.44 and balling index is 3-2.55;

igniting the granules;

and sintering the granules to obtain the iron ore sinter, wherein the iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 67.0-69.7%, shatter index (+10 mm) is 68.4-70.1% and reduction degradation index (+3.15 mm) is 22.0-25.5%.

A further aspect of the present invention is directed to a method of manufacturing iron ore sinter with improved strength by using iron ore fines having particles size of 150 µm or less characterized by comprising the following steps. Firstly, the raw materials are prepared according to the following mass percentage: 50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of iron ore having particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of micro pellets as steel plant wastes and 1.5-2.0% of direct reduced iron fines. Secondly, water is added into the raw materials. Thirdly, the water and raw materials are mixed to obtain a mixture. The moisture content in the mixture is in the range of 7.5-8% by mass. Fourthly, the mixture is granulated to obtain granules. The granules having particles size in the range of 2.44-3.10 mm. The granules granulation index is 3.1-2.44 and balling index is 3-2.55. Fifthly, the granules are ignited. Lastly, the granules are sintered to obtain the iron ore sinter. The iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0mm, tumbler index (+6.3 mm) is67.0-69.7%, shatter index (+10mm) is 68.4-70.1% and reduction degradation index (+3.15mm) is 22.0-25.5%.

A still further aspect of the present invention is directed to said method wherein the iron ore comprises 50-55% of iron ore fines having particle size of -10 mm or less, 30-40% of iron ore fines having particle size of 150 µm or less, 0-55% of washed ore having particle size of -3mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98% of beneficiation plant concentrate having particle size of 150 µm or less.

A still further aspect of the present invention is directed to said method wherein the ignition suction is maintained in the range of 600-700 mmH2O and ignition temperature of 1150-1160oC.

Another aspect of the present invention is directed to said method wherein the sintering suction is maintained in the range of 1200-1300 mmH2O.

A still further aspect of the present invention is directed to said method wherein the basicity of the iron ore sinter is maintained in the range of 1.8-2.20%.

A still further aspect of the present invention is directed to said method wherein the mass percentage of MgO in the iron ore sinter is in the range of 2.0-2.40%.

A still further aspect of the present invention is directed to said method wherein the mass percentage of coke breeze is in the range of 58-60kg/t and carbon rate of the coke breeze is in the range of 48-49.5kg/t.

A still further aspect of the present invention is directed to said method wherein the sinter bed permeability is maintained in the range from 52.3-45.5 JPU.

A still further aspect of the present invention is directed to said method wherein the main components of the iron ore sinter by weight percentage are 53.6-53.0% of iron, 10.21-9.37% of FeO and 11.26-11.55% of CaO.

A still further aspect of the present invention is directed to said method wherein the main components of iron ore fines are 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%; the main components of washed ore are 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3and loss on ignition is 3-4%;the main components of sinter return fines are 50-52.5% Fe, 4.8-5.70% of SiO2, 4.2-4.5% of Al2O3; the main components of limestone are 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42% the main components of dolomite are 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45% the main component of coke breeze is 76-80% of carbon; the main components of micro pellet are 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56-15.5% of carbon and loss on ignition is 16.63-17.50%; the main components of iron ore fines are 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4%; and the main component of direct reduced iron fines is 85-87% of Fe.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 illustrates the flow chart for a process of manufacturing iron ore sinter with improved strength by using iron ore fines having particles size of 150 µm or less according to present invention;

FIG. 2 illustrates the effect of iron ore fines with particles size of 150 µm or less on granulation index;

FIG. 3 illustrates the influence of moisture addition on balling index with iron ore fines with particles size of 150 µm or less;

FIG. 4 illustrates the influence of moisture addition on sinter bed permeability when sinter mixture comprises iron ore fines with particles size of 150 µm or less;

FIG. 5 illustrates phase analysis and microstructure of iron ore sinter with particle size 150µm or less in sinter mixture from 26.7-9.4%;

FIG. 6 illustrates phase analysis and microstructure of iron ore sinter with particle size 150µm or less in sinter mixture from 26.7-9.4%;

Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The accompanying figure together with the detailed description below forms part of the specification and serves to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.

The present invention is now discussed in more detail referring to the drawings that accompany the present application. In the accompanying drawings, like and/or corresponding elements are referred to by like reference numbers.

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts.

Before describing in detail embodiments that are in accordance with the invention, it should be observed that the embodiments reside primarily for a method of manufacturing iron ore sinter with improved strength by using iron ore sintering composition including fines having particles size of 150 µm or less.

The present invention relates to the production of high strength iron ore sinter for blast furnace iron making unit developed by using iron ore having particles size of 150 µm or less as raw material in sintering. The parameters like sinter bed permeability, green mix moisture, sinter basicity, sinter MgO, coke breeze addition, sintering suction pressure with iron ore having particles size of 150 µm or less in as raw material in sintering resulted in production of good quality iron ore sinter required for blast furnace iron making units. The production of high strength iron ore sinter for blast furnace iron making unit was developed by using the iron ore fines having particle size of 150µm or less in sinter mixture which consists of iron ore fines, washed ore, limestone, dolomite, coke breeze, lime, sinter return fines, DRI fines and micro pellets produced from steel plant waste. The sintering process comprises preparation of mixture, mixing and production of granules using mixing and nodulising drum by maintain the optimum moisture, transferring of granules to sintering machine and firing of granules by applying suction pressure.

The present invention relates to an iron ore sintering composition including iron ore fines suitable for blast furnace iron making comprising: 50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of iron ore having particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of pellets as steel plant wastes and 1.5-2.0% of direct reduced iron fines; and moisture content in the range of 7.5-8% by wt.

The iron ore comprises 50-55% of iron ore having particle size of -10 mm or less, and 30-40% of particle size of 150 µm or less, 0-55% of washed ore having particle size of -3 mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98 % of beneficiation plant concentrate having particle size of 150 µm or less favouring sinter characteristics including iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 67.0-69.7%, shatter index (+10 mm) is 68.4-70.1% and reduction degradation index (+3.15 mm) is 22.0-25.5%.

The iron ore fines include 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%; washed ore include 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3 and loss on ignition is 3-4%; sinter return fines include 50-52.5% Fe, 4.8-5.70% of SiO2 and 4.2-4.5% of Al2O3; limestone include 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42%; dolomite include 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45%; coke breeze include 76-80% of carbon; pellet include 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56-15.5% of carbon and loss on ignition is 16.63-17.5%; iron ore fines include 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4.3%; and direct reduced iron fines include 85-87% of Fe.

The present invention relates to a method 100 of manufacturing iron ore sinter with improved strength by using iron ore fines having particles size of 150 µm or less as illustrated in flowchart shown in accompanying FIG.1. The method 100 characterized by comprising the following steps. The sintering process begins with the preparation of mixture consists of raw materials like iron ore fines, fluxes like limestone & dolomite, coke breeze, sinter return fines, lime, DRI fines and micro pellet which are produced from steel plant wastes. In step 102, the raw materials as a iron ore sintering composition including iron ore fines are prepared according to the following mass percentage: 50-55% of total iron ore, wherein the iron ore comprises 26.7-18.9% of iron ore having particles size of 150 µm, fluxes comprise 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprises 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of micro pellets as steel plant wastes and 1.5-2.0% of direct reduced iron fines. The iron ore comprises the iron ore comprises 50-55% of iron ore fines having particle size of -10 mm or less, 30-40% of iron ore fines having particle size of 150 µm or less, 0-55% of washed ore having particle size of -3mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98 % of beneficiation plant concentrate having particle size of 150 µm or less. In raw material, the proportion of iron ore fines is relatively much higher than that of other raw materials and therefore the contribution of iron ore of particle size of 150 µm or less in sinter mix is maximum through iron ore. The main components of iron ore fines are 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%. The main components of washed ore are 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3 and loss on ignition is 3-4%. The main components of sinter return fines are 50-52.5% Fe, 4.8-5.70% of SiO2 and 4.2-4.5% of Al2O3. The main components of limestone are 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42%. The main components of dolomite are 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45%. The main component of coke breeze is 76-80% of carbon. The main components of micro pellet are 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56-15.5% of carbon and loss on ignition is 16.63-17.5%. The main components of iron ore fines are 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4.3%. The main component of direct reduced iron fines is 85-87% of Fe.

In step 104, water is added into the raw materials.

In step 106, the mixture is obtained by mixing raw materials and water. The moisture content in the mixture is in the range of 7.5-8% by mass.

In step 108, the mixture is granulated to obtain granules. The granules having particles size in the range of 2.44-3.10 mm. The raw materials are mixed and produced granules using mixing and nodulising drum using water to reach proper agglomeration of the raw material mix. The granules granulation index is 3.1-2.44 and balling index is 3-2.55.

In step 110, the granules are ignited. The ignition suction is in the range of 600-700 mmH2O and ignition temperature of 1150-1160oC. The mass percentage of coke breeze is in the range of 58-60kg/t and carbon rate of the coke breeze is in the range of 48-49.5kg/t.

Lastly, in step 112, the granules are sintered to obtain the iron ore sinter. Sintering suction is in the range of 1200-1300 mmH2O.The sinter bed permeability is in the range from 52.3-45.5 JPU. These agglomerates are transferred to sintering machine. In the Dwight-Lloyd sintering machine, the sintering grate is a continuous chain of large length and width, formed by the joining together of a series of pallet cars which make the sintering strand. Each pallet car passes below a charging hopper where it is charged firstly by granules of coarse granulometry (10-20 mm) in a layer having thickness of 30-60 mm which forms the hearth layer composed mainly of sinter return fines. The hearth layer protects steel grates from over-heating during the sintering process. The sinter top layer is ignited with mixed gas using burners placed in the surface of the charge (1150-1160oC). At the same time, the mix is subjected to down draught suction through the sinter charge. Due to the down draught suction, air is drawn through the moving bed causing the fuel to burn. The pallet car continues the process and the combustion progresses in the direction of the gas flow. In this way, whole granules from top to bottom reaches the suitable temperature with the help of suction required for the partial melting of the mix with help of added coke breeze, and the subsequent agglomeration takes place. The combustion process does not happen simultaneously in the whole thickness of the bed. On the contrary, combustion happens as a horizontal layer which moves vertically through the bed. The thickness of this layer is a small fraction of the bed. Permeability of the bed is a quality requirement for the charge mix, and hence, the granulation process of the charge mix is an important step for the sintering process (permeability of the bed is improved due to granulation). Burn through temperature (BTP) indicates the completion of the sintering process. BTP is defined as the point where the temperature of the waste gas reaches its highest value. It is the point at which the flame front reaches the base of the bottom of the sinter bed. Sinter machine velocity and gas flow are controlled to ensure that the burn through point occurs just prior to the sintered iron being discharged.

After completion of sintering process, the hot iron ore sinter in the form of cake is discharged into the crusher. Here the hot iron ore sinter is crushed to required size of 0-60mm. From here the sinter is discharged onto the sinter cooler. After cooler the iron ore sinter is transferred to the screening section where it is divided normally into three granulometric fractions. The first fraction consists of 0 to 5mm which is called return fines and is sent to the feeding hoppers. Sinter fraction with a granulometry range within 10-20mm is used as hearth layer in the sinter strand. The balance amount of 10-20mm fraction which is not used for hearth layer is mixed with the third granulometric fraction having a size range of 5-60mm is sent to the blast furnace. Return fines are unavoidably generated during the sintering process, and are recycled back into the sintering process. Return fines generally consists of around 30-40% of the iron bearing materials.

The iron ore sinter productivity value is 41.0-42.8 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 67.0-69.7%, shatter index (+10 mm) is 68.4-70.1% and reduction degradation index (+3.15 mm) is 22.0-25.5%.The basicity of the iron ore sinter which is in the range of 1.8-2.20%. The mass percentage of MgO in the sinter is in the range of 2.0-2.40%. The main components of the iron ore sinter by weight percentage are 53.6-53.0% of iron, 10.21-9.37% of FeO and 11.26-11.55% of CaO.

In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article or composition that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article or composition. An element proceeded by "comprises...a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article or composition that comprises the element.

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless specifically stated otherwise.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are additionally interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted as ideal or very formal meanings unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

In addition, unless otherwise specified,% means weight%.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and are conventional in the art to which the present invention pertains. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid obscuring the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains.
The present invention is described further hereinafter by reference to a series of examples.

Experiments that were actually performed are now described by way of following examples.

Examples

Example I: Preparation of Iron ore sinter Raw Materials
The raw materials as ion ore sintering composition including iron ore fines were prepared according to the following mass percentage: 50-55% of total iron ore, wherein the percentage of the iron ore fines with particles size of 150 µm was varied from 9.7% to 26.7%, fluxes comprised 6.0-6.4% of dolomite and 5.0-6.5% of limestone, 1.8-2.0% of lime, solid fuel comprised 5-5.4% of coke breeze, 17.0-22.0% of sinter return fines, 4.5-5.0% of pellets as steel plant wastes and 1.5-2.0% of direct reduced iron fines. The main components of iron ore fines were 59-60% Fe, 4.6-4.9% SiO2, 3.8-4.3% of Al2O3 and loss on ignition is 3.5-4.5%. The main components of washed ore were 62-62.5% Fe, 4-4.15% SiO2, 3-3.20% of Al2O3 and loss on ignition is 3-4%. The main components of sinter return fines were 50-52.5% Fe, 4.8-5.70% of SiO2 and 4.2-4.5% of Al2O3. The main components of limestone were 0.88-1.30% Fe, 0.93-1.50% of SiO2, 0.42-0.6% of Al2O3, 45-50% of CaO, 1-2% of MgO and loss on ignition is 40-42%. The main components of dolomite were 0.80-1.50% Fe, 0.88-2% of SiO2, 0.36-0.7% of Al2O3, 29-33% of CaO, 16-18.5% of MgO and loss on ignition is 42-45%. The main component of coke breeze was 76-80% of carbon. The main components of micro pellet were 38-40% Fe, 7.8-9% of SiO2, 3-4.2% of Al2O3, 14.56% of carbon and loss on ignition is 16.63-17.5%. The main components of iron ore fines were 61.5-62% Fe, 4.2-4.35% SiO2, 3.25-3.45% of Al2O3 and loss on ignition is 3.2-4.3%. The main component of direct reduced iron fines was 85-87% of Fe. The iron ore comprised 50 to 55% of iron ore fines having particle size of -10mm or less, 30-40% of iron ore fines having particle size of 150 µm or less, 0-55% of washed ore having particle size of -3mm or less, 3-9% of washed ore having particle size of 150 µm or less, 96-98% of beneficiation plant concentrate having particle size of 150 µm or less.

Example II: Preparation of the Granules by Granulation
Firstly, the raw materials were prepared according to Example 1. Secondly, water was added into the raw materials. Thirdly, the water and raw materials were mixed to obtain a mixture. The moisture content in the mixture was in the range of 7.5-8% by mass. Fourthly, the mixture was granulated to obtain granules. The granules having particles size in the range of 2.44-3.10 mm.

Example III: Granules Evaluation
The quality of the sinter mainly depends on the sinter granulometry. Sinter granulometry and depends on the particle size of the iron ore fines required for making sinter granules. The produced sinter for blast furnace iron making unit should have optimum physical and metallurgical properties. For making good quality of sinter optimum with percentage of the iron ore fines in the raw material with particles size of 150 µm or less in sinter mixture is essential.

To optimize iron ore fines with the particles size of 150 µm or less in sinter mixture the washed ore of beneficiation plant jig concentrate was used for detailed sintering studies. The size analysis of sinter base mix with washed ore addition (replacing iron ore fines) is shown in Table 1.

Table 1
Washed ore,% Size, mm
+10 -10+8 -8+6 -6+3.15 -3.15+1 -1.0.5 -0.5+0.25 -0.25+0.150 -0.150
0 2.2 3.1 6.3 21.5 21.7 8.1 6.3 4.0 26.7
5 2.0 2.9 6.1 21.8 22.8 8.2 6.5 4.2 25.5
10 1.8 2.7 6.0 22.3 24.1 8.3 6.6 4.4 23.9
15 1.6 2.5 5.8 22.7 25.5 8.4 6.8 4.6 22.2
20 1.4 2.3 5.7 23.1 26.8 8.5 6.9 4.7 20.5
25 1.2 2.1 5.6 23.5 28.1 8.6 7.1 4.9 18.9
30 1.1 1.9 5.4 23.9 29.4 8.7 7.2 5.1 17.3
35 0.7 1.5 5.3 24.4 30.5 8.8 7.4 5.3 16.1
40 0.5 1.2 5.1 24.8 31.8 9.0 7.5 5.5 14.6
45 0.4 0.6 4.8 24.4 32.1 8.6 7.3 5.4 11.9
50 0.2 0.7 4.8 26.5 34.5 9.2 7.8 5.8 11.4
55 0.0 0.5 4.6 25.5 32.7 8.4 7.0 5.6 9.4

With increase in washed ore addition in sinter base mix (replacement of iron ore fines of -10mm) the 150µm decreased and coarser size of -10+8 and -8+6mm also decreased.

To know the effect of finer size (-150µm) in base mix as adhering material the iron ore fines of -10mm size was replaced with washed ore. To optimize the finer size of 150µm in sinter base mix as adhering material size analysis of sinter base mix, granulation index of sinter base mix, and optimum moisture required for sinter granules were carried out by replacing the iron ore fines of -10mm size with washed ore.

Accompanying FIG. 2 shows the effect of iron ore fines with particles size of 150 µm or less on granulation index. The granulation index as calculated as described in Crores et.al. Relationship between sinter properties and iron ore granulation index, Ironmaking and Steelmaking, 2012, Vol. 39, No. 2, pp. 85-94).

With increase in 150µm size in sinter base mix sinter granulation index increases.
The 1kg of granules were collected from balling drum and conducted the size analysis using screens. The balling index of the green sinter was calculated using following expression.

+3mm (Initial wt %)
Balling index = ------------------------------------------
+3mm (Wt % after granulation)

Accompanying FIG. 3 shows the influence of moisture addition on balling index with iron ore fines with particles size of 150 µm or less.

Example IV: Preparation of the Iron ore sinter

The granules were ignited. The ignition suction was in the range of 600-700 mmH2O and ignition temperature of 1150-1160oC. The granules were sintered. The sintering suction was in the range of 1200-1300 mmH2O. The mass percentage of coke breeze was in the range of 58-60 kg/t and carbon rate of the coke breeze is in the range of 48-49.5 kg/t.The basicity of the iron ore sinterwas in the range of 1.8-2.20%. The mass percentage of MgO in the iron ore sinter which is in the range of 2.0-2.40%.

Example V: Sinter Bed Permeability Evaluation
The sinter bed permeability was carried out using bed permeability measuring equipment and bed permeability was calculated using Japanese permeability unit. Lwamba, E. and Garbers-Craig, A.M. 2008. Control of the grain size distribution of the raw material mixture in the production of iron sinter, Journal of the Southern African Institute of Mining and Metallurgy, vol. 108. pp. 293-300. The sinter bed permeability was carried out on different layer as different size iron ore sinters using bed permeability measuring equipment. Accompanying FIG. 4 shows the influence of moisture addition on sinter bed permeability when sinter mixture comprises iron ore fines with particles size of 150 µm or less.

Sinter mixture with iron ore fines with particles size of 150 µm or less varied in percentage from 26.7-9.4%. The sinter bed permeability is 53 to 35 JPU at 8% moisture.

Example VI: Iron ore sinter Mineralogy Evaluation
The specimens were examined using a light microscope in reflection. The volume proportions of phases in sinter were estimated by using the image analyzer.

Accompanying FIG. 5 shows the phase analysis of iron ore sinter with particle size 150µm or less in sinter mixture from 26.7-9.4%.

Accompanying FIG. 6 shows microstructure of iron ore sinter with particle size 150µm or less in sinter mixture.

Sinter mineralogy depends on the sinter bed permeability (sinter granules strength) and sinter chemistry and sintering temperature. With -150µm size 26.7-9.4% in sinter mixture the silico ferrite of calcium and aluminium (SFCA) phase in produced sinter is varying from 41 to 26.0%. Up to -150µm size in sinter mixture the calcium ferrite (CF) phase was uniformly distributed with other phases like hematite (H), magnetite (M), and silicate/slag (S) phase and pores (P) as indicated in FIG. 6. The main components of the iron ore sinter by weight percentage are 53.6-53.0% of iron, 10.21-9.37% of FeO and 11.26-11.55% of CaO.

Example VII: Iron ore sinter Properties Evaluation
The important parameters to consider with respect to quality and iron ore sinter performance are productivity value, mean size value, tumbler index, shatter index and reduction degradation index as given in Table 2

Table 2
150µm in base mix 26.7 25.5 23.9 22.2 20.5 18.9 17.3 16.1 14.9 11.9 11.4 9.4
Washed ore, % w.r.t iron ore (-10mm) 0 5 10 15 20 25 30 35 40 45 50 55
Washed ore, % w.r.t total raw material 0 4.7 9.5 14.2 19 23.8 28.4 33.3 38.3 43 48.5 55
Yield,% 78.6 78.4 78.5 78.4 78.3 78.5 78.4 78.6 78.9 78.6 78.5 77.8
Shrinkage,% 16.4 16.3 15.7 15.1 15.0 14.8 14.3 13.9 12.1 11.4 10.7 10.0
Productivity, t/m2/day
Ton of +5 mm sinter/m2/24 hr 42.8 42.4 42 41.8 41.6 41 40.7 39 38.5 38.1 37.5 35.8
Mean size, mm 19.0 18.8 18.6 18.4 18.2 18.0 17.3 17.0 16.9 16.7 16.2 16.0
Cumulative Size, +10mm,% 71.8 70.7 69.4 69.5 68.7 68.2 67.7 67.0 67.0 65.7 64.9 64.3
Cumulative Size, -5mm,% 10.3 10.5 11.3 11.6 12 12.5 12.4 13.4 14.0 14.6 15 15.2
Tumbler Index (+6.3mm),%
ISO 3271:1995 69.7 68.8 67.5 67.2 67.2 67.0 65.2 64.7 63.8 63.3 62.5 62.1
Abrasion Index (-0.5mm),% 4.9 4.6 5.3 5.5 5.7 6.0 6.4 7.3 7.8 8.2 9.8 10.0
Shatter Index,% 70.1 69.8 69.0 68.4 68.7 68.4 66.1 65.6 64.4 64.2 63.8 62.8
Reduction Degradation Index (+3.15mm),%
ISO 4696-1 22 22.7 23.5 24.5 24.9 25.5 26.8 27.3 28.5 29.5 30.2 31.5

Iron ore sinter produced by using iron ore fines having particles size of 150 µm or less size in sinter mixture from 26.7 to 18.9% achieved desired sinter properties which are required for blast furnace iron making units. The productivity value is 42.8-41.0 t/m2/day, mean size value is 18.0-19.0 mm, tumbler index (+6.3 mm) is 69.7-67.0%, shatter index (+10 mm) is 70.1-68.4% and reduction degradation index (+3.15 mm) is 22.0-25.5%.

Example VI1I: Washed Ore Optimization and Iron ore sinter Properties Evaluation

From Table 2 the sinter properties with washed ore addition beyond 30% with fines<150µm below 19% in sinter base mix, the sinter properties are not suitable for blast furnace iron making unit. Further to confirm the minimum requirement of -150µm size in the total raw material (~19.0%) to achieve the desired sinter properties with washed ore addition 30- 45%, 3-10% iron ore fines (<150µm size) of washed ore was added to the sinter base mix. The important parameters to consider with respect to quality and iron ore sinter performance are productivity value, mean size value, tumbler index, shatter index and reduction degradation index as given in Table 3.
Table 3
-150µm in base mix 19.0%
Washed ore, % w.r.t iron ore fines 30.0 35.0 40.0 45.0

Washed ore, % w.r.t sinter base mix 28.6 33.2 38.5 43.1
-150 µm iron ore fines in washed ore,% 3.4 5.3 8.4 9.0
Yield,% 78.3 78.2 78.1 78.0
Shrinkage, % 14.7 14.6 14.8 14.5
Productivity, t/m2/day 41.5 42.5 42.4 42.6
Mean size, mm 18.2 18.0 18.1 17.9
Cumulative Size, +10mm,% 17.8 18.0 18.1 17.9
Cumulative Size, -5mm,% 11.8 12.2 12.0 12.1
Tumbler Index (+6.3mm), % 67.3 67.0 67.3 67.2
A.I (-0.5mm), % 5.4 5.9 6.0 5.9
Shatter Index,% 68.7 68.6 68.5 68.3
Reduction Degradation Index (+3.15mm), % 25.3 25.5 25.4 25.5

With the addition of iron ore fines<150µm size from 3 to 10% in sinter base mix by maintaining the overall <150µm size ~19% sinter bed permeability was improved from 35, 38 to ~45JPU as shown in FIG. 4. The balling index was improved from 2.2 & 1.65 to 2.5 as shown in FIG. 3. Sinter base mix with -150µm size range 26.7 to 18.9% achieved desired sinter properties are as shown in Table 3. Decreasing the fines size of -150µm below ~19.0% in sinter base mix the sinter properties were deteriorated.

The present invention is not limited to the above embodiments, but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains have other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that can be carried out. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.