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 :
SINTER WITH IMPROVED STRENGTH AND A PROCESS FOR ITS PRODUCTION FAVOURING REDUCED SINTER RETURN FINES.
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 high strength sinter and a method for its production for reduction in generation of blast furnace sinter return fines by optimizing the sinter process parameters. More particularly, the present invention is directed to a process for sinter production by introducing selective composition of sinter raw mix and optimizing the sintering process parameters with respect to raw material properties and sinter chemistry to increase the sinter strength and thereby decreasing the BF sinter return fines in sinter plant.
BACKGROUND OF THE INVENTION
It is well known in the art of iron and steel production that iron ore sinter is produced from fine grained iron ore to feed the blast furnace (BF). During the sinter production process, sinter fines are generated which is not acceptable for blast furnace due to its finer size. The size of sinter has a significant effect on blast furnace performance. Fine material lowers the blast furnace stack permeability and increases dust losses. For smooth furnace operation, the desired sinter size range is -60+5 mm. In order to fulfill size requirement for blast furnace, sinter is being screened at sinter plant before dispatching to blast furnace. The oversize sinter sent from the sinter plant screen house to blast furnace is further screened at blast furnace to remove the fines generated during its transport. The undersize (-5 mm) generated during screening process is known as sinter return fines.
The good quality sinter is necessary to reduce the generation of blast furnace sinter fines by resisting the breakdown during its transportation from sinter plant to blast furnace. These fines are returned to the sinter plant and are recycled. This recycling process results in the loss of sinter production. The sinter return fines mainly decreases the sinter yield and more sinter return fines from the blast furnace is undesirable. Its recirculation may decrease the throughput of the fresh material into the sintering strand. On the other hand, its addition to the sinter mix may improve the yield of sinter because of better fusion and bonding.
The amount of return fines generation depends on the strength of the desired size of sinter. Analysis of plant data has revealed that the average harmonic mean diameter of sinter increases from 15 mm to 20 mm when -5 mm size fraction is screened out from the sinter at the blast furnace point. Such an elimination of fines improves the furnace productivity. The sinter strength, yield of sinter and strand productivity is also influenced considerably by the sintering process parameters.

There has been therefore a need in the existing art to study the influence of sinter plant operating parameters like raw mix chemistry, sinter chemistry, basic laboratory studies to produce sinter of desired size with improved strength. The objective of the present investigation is to optimize the process parameter with respect to raw material properties and sinter chemistry to increase the sinter strength and thereby decreasing the sinter return fines in sinter plant.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to high strength sinter and a process for production of such good quality sinter with improved strength to reduce generation of the sinter return fines at blast furnace end.
A further object of the present invention is directed to a process for production of sinter with improved strength to reduce sinter return fines by selective use of sinter raw mix and implementing the optimized sinter process parameters in sinter plant.
A still further object of the pre sent invention is directed to a process for production of sinter with improved strength to reduce the generation of blast furnace sinter return fines by resisting the breakdown during its transportation from sinter plant to blast furnace.
Yet another object of the present invention is directed to a process for production of sinter with improved strength to reduce sinter return fines wherein the properties of the iron ore sinter are selectively controlled by the composition and distribution of the mineral phases present.
A further object of the present invention is directed to a process for production of sinter with improved strength to reduce sinter return fines wherein sinter basicity is selectively maintained to control the quantity of silico-ferrite of calcium and aluminium (SFCA) at desired level as the SFCA phase is the strongest phase in iron ore sinter and gives strength to the sinter.
A still further object of the present invention is directed to a process for production of sinter with improved strength to reduce sinter return fines wherein disintegration behavior of sinter during handling by maintain optimum quantity of MgO in sinter.

A still further object of the present invention is directed to a process for production of sinter with improved strength to reduce sinter return fines wherein coke breeze size is selectively maintained to balance the internal heat from coke breeze and external heat supplied as gas which improves the combustibility of the coke breeze and improves sinter strength with uniform distribution of microstructural phases.
A still further object of the present invention is directed to a process for production of sinter with improved strength to reduce sinter return fines to achieve overall increase in sinter strength from 74 to 79% decreased the blast furnace sinter return fines from 29.3 to 21.5%.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a new composition for sinter
comprising:
<3.10% Al2O3 in iron ore fines, >85 of -3.15 mm flux size (limestone + dolomite) in sinter
mix, >85 of -3.15 mm coke breeze size in sinter mix, 1.90 to 2.00 sinter basicity
(CaO/Si02), 1.40 to 1.60% MgO in sinter, 68 to 70% coke breeze in sinter raw mix, and
8.60 to 9.80% FeO in sinter.
A further aspect of the present invention is directed to sinter obtained involving flanged composition comprising <3.10% Al203 in iron ore fines, >85 of -3.15 mm flux size (limestone + dolomite) in sinter mix, >85 of -3.15mm coke breeze size in sinter mix, 1.90 to 2.00 sinter basicity (CaO/Si02), 1.40 to 1.60% MgO in sinter, 68 to 70% coke breeze in sinter raw mix, and 8.60 to 9.80% FeO in sinter.
A still further aspect of the present invention is directed to said sinter having sinter strength in the range of 79 to 81%
A still further aspect of the present invention is directed to a process for the production of sinter with improved strength and favouring reducing the sinter return fines comprising the steps of
(i) providing sinter raw mix comprising iron ore fines, limestone, dolomite, coke breeze,
lime, and sinter return fines such as to maintain
<3.10 wt% Al203 in iron ore fines,
>85% of -3.15 mm flux size (limestone + dolomite) in sinter mix,

>85% of -3.15 mm coke breeze size in sinter mix,
1.90 to 2.00 sinter basicity (CaO/Si02),
1.40 to 1.60 wt% MgO in sinter,
68 to 70 wt% coke breeze in sinter raw mix, and
8.60 to 9.80 wt% FeO in sinter,
and feeding to the mixing and granulation drum along with water to get small granules or agglomerates;
(ii) feeding the mix granules/agglomerates onto the moving grate (sinter strand) and
igniting at the top of the layer; (iii)drawing the hot gases into the bed of agglomerates as sinter strand move from one
end of the strand to another end for sintering reaction to proceed through sinter
bed whereby different phases are formed; (iv)breaking the sinter cake after completion of the process at the discharge end in the
sinter breaker; (v) feeding the broken sinter lumps to the cooler wherein the different mineral phases
crystallize and bond the structure together to form strong sinter.
Yet another aspect of the present invention is directed to a process for the production of sinter comprising the steps of
(i) providing sinter raw mix comprising iron ore fines, limestone, dolomite, coke
breeze, lime, and sinter return fines such as to maintain
<3.10 wt% Al203 in iron ore fines,
>85% of -3.15 mm flux size (limestone + dolomite) in sinter mix,
>85°/o of -3.15mm coke breeze size in sinter mix,
1.90 to 2.00 sinter basicity (CaO/SiO2),
1.40 to 1.60wt% MgO in sinter,
68 to 70wt% coke breeze in sinter raw mix, and
8.60 to 9.80wt% FeO in sinter,
and feeding to the mixing and granulation drum along with water to get small granules or agglomerates;
(ii) feeding the mix granules/agglomerates onto the moving grate (sinter strand) and the incorporated fuel is ignited at the top of the layer by Corex gas;

(iii) drawing the hot gases into the bed of agglomerates as sinter strand move from one end of the strand to another end for sintering reaction to proceed through sinter bed whereby different phases are formed based on chemical composition of the material and temperature;
(iv) breaking the sinter cake after completion of the process at the discharge end in the sinter breaker;
(v) feeding the broken sinter lumps to the cooler wherein the different mineral phases crystallize and bond the structure together to form strong sinter;
(vi) screening the lump sinter at sinter plant end and over size sinter (-50+5) is sent to the blast furnace and under size sinter is reused.
A further aspect of the present invention is directed to a process for the production of sinter comprising controlling the composition and distribution of the mineral phase present to control the properties of the iron ore sinter.
A still further aspect of the present invention is directed to a process for the production of sinter wherein sinter basicity is maintained in the range of 1.9 to 2.0 to achieve favourable quantity of silico-ferrite of calcium and aluminium (SFCA) phase and also desired Fe content of the sinter.
A still further aspect of the present invention is directed to a process for the production of sinter wherein MgO in sinter is maintained in the range of 1.20 to 1.40% to get the desired sinter strength by avoiding deterioration of strength due to the formation of vitreous glassy matrix and dicalcium silicates which are the phases harmful for sinter strength because these structures exhibit a high degree of stress.
A still further aspect of the present invention is directed to a process for the production of sinter wherein alumina is maintained less than 3.10% in sinter causing more number of SFCA-1 phase having calcium ferrite in sinter identified as a solid solution of CaO.2Fe203 (CF2) with small amount of Al203 and SiO2, leading to higher strength.
A still further aspect of the present invention is directed to a process for the production of sinter wherein coke breeze size -3.15% is maintained in the range of 85 to 90%, and preferably at least 85% to improve sinter strength with uniform distribution of microstructural phases and reduced porosity.

Yet another aspect of the present invention is directed to a process for the production of sinter wherein flux size -3.15 mm 85 to 90% , preferably at least 85% is maintained which increases the reaction rate in the sintering process due to better and uniform distribution of flux particles and better bed permeability causing easy assimilation of fluxes with hematite resulting in uniform distribution of calcium ferrites and silicate bonds during sintering process providing good strength to sinter.
A further aspect of the present invention is directed to a process for the production of sinter wherein to achieve the optimum FeO content of 8.60 to 9.80 wt% FeO in sinter of desired strength, the coke breeze addition should be in the range of 68 to 70 kg/t of sinter.
The objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: is the schematic diagram showing the different stages in a conventional sinter plant to execute the sintering process.
Figure 2: is the graphical presentation showing the various sinter process parameters before and after implementation of the process according to the present invention.
Figure 3: is the graphical presentation showing the comparative of Sinter strength and sinter return fines before and after implementation of the process according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention relates to a process for production of sinter with improved strength to reduce sinter return fines by selective use of sinter raw mix and implementing the optimized sinter process parameters in sinter plant. The good quality sinter is necessary to reduce the generation of blast furnace sinter fines by resisting the breakdown during its transportation from sinter plant to blast furnace.

In order to achieve the above objective, advancement in the area of technology to permeate new composition and process coordinates for production of sinters has been explored. The present advancement/invention contemplates the production of sinters which reduces the amount of sinter return fines substantially. In order to accomplish the aforementioned objective a new flanged composition range (by weight) for sinter is proposed. The composition and the constituent are as follows:
<3.10% Al2O3 in iron ore fines,
>85 of -3.15 mm flux size (limestone + dolomite) in sinter mix,
>85 of -3.15 mm coke breeze size in sinter mix,
1.90 to 2.00 sinter basicity (CaO/Si02),
1.40 to 1.60 % MgO in sinter,
68 to 70% coke breeze in sinter raw mix, and
8.60 to 9.80% FeO in sinter.
The sinter mix having the above characteristics is processed in a conventional sinter plant. Accompanying Figure 1 is the schematic diagram showing the different stages in a conventional sinter plant to execute the sintering process. The stages in the sinter making process as marked in the Figure 1 are as follows:
1. Moving grate (Sinter Strand)
2. Raw material mix
3. Mixing and granulation drum
4. Agglomerates/granules
5. Ignition wood
6. Air
7. Suction air
8. Sinter cake
9. Crusher

10. Cooler
11. Screen at sinter plant

12. Sinter Bin
13. Screen at BF end
In the sintering process, the raw materials (iron ore fines, limestone, dolomite, coke breeze, lime, and sinter return fines) mix from different bins are fed to the mixing and granulation drum along with the water to get small granules or agglomerates. After feeding the mix granules/agglomerates onto the moving grate (sinter strand) the incorporated fuel is ignited at the top of the layer by Corex gas. Corex gas is the gas produced in the Corex iron making process from melter-gasifier and has high net calorific value of approximately 7500 - 8000 kJ/m3. The hot gases are drawn into the bed of agglomerates as sinter strand move from one end of the strand to another end. Within that time various physico-chemical phenomenon take place (formation of calcium ferrites with the reaction of CaO of limestone and Fe of iron ore, formation of slag phase with reaction of CaO and MgO of limestone & dolomite with Si02 of raw material, and formation of magnesio ferrites with the reaction of MgO of dolomite with the Fe of iron ore fines) and different phases are formed based on chemical composition of the material and temperature. Here after completion of the process at the discharge end the sinter breaker breaks the sinter cake and broken sinter lumps fed to the cooler. Within this cooler, the different mineral phases crystallize and bond the structure together to form strong sinter. The lump sinter is screened at sinter plant end and over size sinter (-50+5) is sent to the blast furnace and under size sinter is reused. At blast furnace screening house once again screening of the sinter takes place to remove the -5 mm sinter to improve the blast furnace performance. The generated -5 mm size sinter at blast furnace end is known as blast furnace sinter return fines.
Thus the sintering process according to-the present invention involves the steps of
(i) Providing sinter raw mix comprising iron ore fines, limestone, dolomite, coke breeze, lime, and sinter return fines wherein
a. <3.10% Al203 in iron ore fines,
b. >85% of -3.15 mm flux size (limestone + dolomite) in sinter mix,
c. >85% of -3.15mm coke breeze size in sinter mix,
d. 1.90 to 2.00 sinter basicity (CaO/Si02),
e. 1.40 to 1.60% MgO in sinter,
f. 68 to 70% coke breeze in sinter raw mix, and
g. 8.60 to 9.80% FeO in sinter,

h. fed to the mixing and granulation drum along with the water to get small granules or agglomerates
(ii) feeding the mix granules/agglomerates onto the moving grate (sinter strand) and
the incorporated fuel is ignited at the top of the layer by Corex gas. (iii)drawing the hot gases into the bed of agglomerates.as sinter strand move from one
end of the strand to another end for sintering reaction to proceed through sinter bed
whereby different phases are formed based on chemical composition of the material
and temperature. (iv)breaking the sinter cake after completion of the process at the discharge end in the
sinter breaker; (v) feeding the broken sinter lumps to the cooler wherein the different mineral phases
crystallize and bond the structure together to form strong sinter; (vi)screening the lump sinter at sinter plant end and over size sinter (-50+5) is sent to
the blast furnace and under size sinter is reused.
As already stated the sintering process according to the present invention involves a sinter raw mix charge comprising (by weight) <3.10% Al203 in iron ore fines, 85 to 90% of -3.15 mm flux size (limestone + dolomite) in sinter mix, >85 to 90% of coke breeze -3.15 mm size in sinter mix, 1.90 to 2.00 sinter basicity (CaO/Si02), 1.40 to 1.60% MgO in sinter, 68 to 70% coke breeze in sinter raw mix, and 8.60 to 9.80% FeO in sinter.
The properties of the iron ore sinter are controlled by the composition and distribution of the mineral phases present. The sinter having basicity below 1.9% shows the lesser strength due to the presence of lower quantity of silico-ferrite of calcium and aluminium (SFCA). The SFCA phase is the strongest phase in iron ore sinter and gives strength to the sinter. In sinter, SFCA is the major mineral constituent of the sinter structure and it imparts strength to the sintered mass. With increase in sinter basicity, sinter strength increased up to basicity 1.90 to 2.0 even up to 2.80. With increase in sinter basicity the total Fe content of the sinter reduces. Concern to total Fe content of the sinter, basicity of the sinter should not be too high. High basicity sinter reduces the blast furnace output by generating more slag. By keeping this in mind the sinter basicity 1.90 to 2.0 is considered as best sinter basicity to reduce the sinter return fines.
The strength of the sinter gives an indication of its disintegration behavior during handling, and has been found to be influenced by MgO. The optimum quantity of MgO in sinter is 1.20 to 1.40%. Beyond sinter MgO content of 1.40%, sinter strength deteriorated due to the

formation of vitreous glassy matrix and dicalcium silicates as these phases are harmful for sinter strength and these structures exhibit a high degree of stress. Below 1.20% MgO, the formation of magnetite phase and magnetite spinel decreases. This affects the other sinter properties like sinter reducibility. The minimum MgO content was maintained to achieve the sinter strength with other desired properties for sinter making.
The behaviour of alumina during iron ore sintering and its influence on the quality of the product sinter has long been a subject of concern for Indian iron makers. The alumina has deleterious effect both on the performance of sinter plant as well as blast furnace. Alumina in sinter mix requires higher heat for its assimilation and delays the sintering process due to its refractory nature. In sinter, calcium ferrite is the major mineral constituent of the sinter structure and it imparts strength to the sintered mass. The most existing calcium ferrite in sinter has been identified as a solid solution of Ca0.2Fe203 (CF2) with small amount of Al203 and Si02, known as SFCA-1 and with large amount of AI2O3 and Si02, known as SFCA. The SFCA-1 phase is stronger than SFCA. The sinter with alumina less than 3.10% consists of more number of SFCA-1 phase and sinter with greater than 3.10% alumina consist of more number of SFCA phase. Sinter with lower alumina gives better strength to the sinter. If sinter consist of higher alumina >3,10% deteriorates the sinter strength and increases the sinter return fines.
For uniform firing a definite firing cycle has to be maintained in order to balance the internal heat from coke breeze and external heat supplied as gas. The internal heat of the sinter mainly depends on size of the coke breeze particles. The sinter with optimum coke breeze size -3.15mm should be 85 to 90%. The size of the coke breeze particles strongly influences sinter porosity as well as microstructural phases. Bigger the size of the coke breeze particles develops the bigger size pores and deteriorates the sinter strength and increases the sinter porosity. It is well known that the combustion of the coke particles is directly proportional to its particle size. Finer the coke breeze burns faster and improves the combustibility of the coke breeze and improves sinter strength with uniform distribution of microstructural phases. If the coke breeze particle size beyond 90% is no harm for sinter quality. But minimum 85% is enough to get the good quality of sinter.
Fluxes are decomposed to form CaO and MgO which further react with hematite to form different ferrites. Optimum flux size -3.15 mm 85 to 90% increases the reaction rate in the sintering process and this could be due to better and uniform distribution of flux particles

and better bed permeability caused easy assimilation of fluxes with hematite. These reactions causes uniform distribution of calcium ferrites and silicate bonds during sintering process gives good strength to sinter. With coarser size flux i.e., -3.15 mm less than 85% in sinter mix, these reactions are mostly insignificant in assimilation because the time required for decomposition and diffusion are limited in sintering. If the flux particle size beyond 90% is no harm for sinter quality. But minimum 85% is enough to get the good quality of sinter.
Coke breeze supplies necessary heat to the sintering process. Evolution of sinter quality and structure is primarily governed by the thermal state of the process. If the ignition conditions are kept constant, amount of coke breeze added can be considered governing the thermal state of the sintering process. FeO is an indicator of the thermal state of the sintering. Sinter FeO content increases with increasing coke breeze addition. The variation in sinter FeO has been effected by varying the amount of coke breeze in the sinter mix. FeO content in the sinter is employed as quality control tool at sinter plants. FeO content in the sinter is the measure of magnetite content. At optimum FeO content of the sinter is 8.60 to 9.80%. The SFCA is the main bonding phase in the sinter. The FeO content in the sinter is less than 8.60% the sinter strength deteriorates due to the porous structure with dendritic SFCA and un-reacted ore particles and poor bonding of the hematite, magnetite and ferrites phases with slag phase. The sinter with FeO 9.80% showed lower strength due to the presence of large quantity of columnar SFCA phase with magnetic phase. To achieve the optimum FeO content in the sinter the coke breeze addition should be in the range of 68 to 70 kg/t of sinter.
Accompanying Figure 2 shows the sinter process parameters before and after implementation. Accompanying Figure 3 shows the improvement in sinter strength and reduction in sinter return fines before and after implementation of sintering process parameters
It is thus possible by way of the present invention to providing a process for production of sinter with improved strength to reduce sinter return fines wherein the good quality sinter necessary to reduce the generation of blast furnace sinter fines by resisting the breakdown during its transportation from sinter plant to blast furnace has been achieved. The process involved selective composition and properties of sinter raw mix introduction leading to overall increase in sinter strength from 74 to 79% with blast furnace sinter return fines reduced from 29.3 to 21.5%.

We Claim:
1. A flanged composition for sinter comprising:
<3.10% Al203 in iron ore fines, >85 of -3.15 mm flux size (limestone + dolomite) in sinter mix, >85 of -3.15 mm coke breeze size in sinter mix, 1.90 to 2.00 sinter basicity (CaO/SiO2), 1.40 to 1.60% MgO in sinter, 68 to 70% coke breeze in sinter raw mix, and 8.60 to 9.80% FeO% in sinter.
2. Sinter obtained involving flanged composition comprising <3.10% Al203 in iron ore fines, >85
of -3.15 mm flux size (limestone + dolomite) in sinter mix, >85 of -3.15mm coke breeze size in sinter mix,
1.90 to 2.00 sinter basicity (CaO/Si02), 1.40 to 1.60% MgO in sinter, 68 to 70% coke breeze in sinter raw
mix, and 8.60 to 9.80% FeO in sinter.
3. Sinter as claimed in claim 2 having sinter strength in the range of 79 to 81%
4. A process for the production of sinter with improved strength and favouring reducing the
sinter return fines comprising the steps of
(i) providing sinter raw mix comprising iron ore fines, limestone, dolomite, coke breeze, lime, and sinter return fines such as to maintain <3.10 wt% Al2O3 in iron ore fines,
>85% of -3.15 mm flux size (limestone + dolomite) in sinter mix,
>85% of -3.15mm coke breeze size in sinter mix,
1.90 to 2.00 sinter basicity (CaO/Si02),
1.40 to 1.60 wt% MgO in sinter,
68 to 70 wt% coke breeze in sinter raw mix, and
8.60 to 9.80 wt% FeO in sinter,
and feeding to the mixing and granulation drum along with water to get small granules or agglomerates;
(ii) feeding the mix granules/agglomerates onto the moving grate (sinter strand) and
igniting at the top of the layer; (iii)drawing the hot gases into the bed of agglomerates as sinter strand move from one
end of the strand to another end for sintering reaction to proceed through sinter
bed whereby different phases are formed;

(iv)breaking the sinter cake after completion of the process at the discharge end in the
sinter breaker; (v) feeding the broken sinter lumps to the cooler wherein the different mineral phases
crystallize and bond the structure together to form strong sinter.
5. A process for the production of sinter as claimed in claim 4 comprising the steps of
(i) providing sinter raw mix comprising iron ore fines, limestone, dolomite, coke breeze, lime, and sinter return fines such as to maintain
a. <3.10 wt% Al2O3 in iron ore fines,
b. >85% of -3.15 mm flux size (limestone + dolomite) in sinter mix,
c. >85% of -3.15 mm coke breeze size in sinter mix,
1.90 to 2.00 sinter basicity (CaO/Si02),
d. 1.40 to 1.60 wt% MgO in sinter,
e. 68 to 70 wt% coke breeze in sinter raw mix, and
f. 8.60 to 9.80 wt% FeO in sinter,
g. and feeding to the mixing and granulation drum along with water to get small
granules or agglomerates;
(ii) feeding the mix granules/agglomerates onto the moving grate (sinter strand) and
the incorporated fuel is ignited at the top of the layer by Corex gas; J (iii)drawing the hot gases into the bed of agglomerates as sinter strand move from one
end of the strand to another end for sintering reaction to proceed through sinter bed
whereby different phases are formed based on chemical composition of the material
and temperature; (iv)breaking the sinter cake after completion of the process at the discharge end in the
sinter breaker; (v) feeding the broken sinter lumps to the cooler wherein the different mineral phases
crystallize and bond the structure together to form strong sinter; (vi) screening the lump sinter at sinter plant end and over size sinter (-50+5) is sent to
the blast furnace and under size sinter is reused.
6. A process for the production of sinter as claimed in anyone of claims 5 or 6 comprising
controlling the composition and distribution of the mineral phase present to control the
properties of the iron ore sinter.

7. A process for the production of sinter as claimed in anyone of claims 5 to 6, wherein sinter basicity is maintained in the range of 1.9 to 2.0 to achieve favorable quantity of silico-ferrite of calcium and aluminium (SFCA) phase and also desired Fe content of the sinter.
8. A process for the production of sinter as claimed in anyone of claims 5 to 7, wherein MgO in sinter is maintained in the range of 1.20 to 1.40% to get the desired sinter strength by avoiding deterioration of strength due to the formation of vitreous glassy matrix and dicalcium silicates which are the phases harmful for sinter strength because these structures exhibit a high degree of stress.
9. A process for the production of sinter as claimed in anyone of claims 5 to 8, wherein alumina is maintained less than 3.10% in sinter causing more number of SFCA-1 phase having calcium ferrite in sinter identified as a solid solution of Ca0.2Fe2O3 (CF2) with small amount of Al203 and Si02i leading to higher strength.

10. A process for the production of sinter as claimed in anyone of claims 5 to 9, wherein coke breeze size -3.15% is maintained in the range of 85 to 90%, and preferably at least 85% to improve sinter strength with uniform distribution of microstructural phases and reduced porosity.
11. A process for the production of sinter as claimed in anyone of claims 5 to 10 wherein flux size -3.15 mm 85 to 90%, preferably at least 85% is maintained which increases the reaction rate in the sintering process due to better and uniform distribution of flux particles and better bed permeability causing easy assimilation of fluxes with hematite resulting in uniform distribution of calcium ferrites and silicate bonds during sintering process providing good strength to sinter.
12. A process for the production of sinter as claimed in anyone of claims 5 to 11, wherein to achieve the optimum FeO content of 8.60 to 9.80 wt% FeO in sinter of desired strength, the coke breeze addition should be in the range of 68 to 70 kg/t of sinter.