Claims:We Claim:

1. Iron ore blend for sintering including specular iron ore suitable for improved sinter performance comprising:
iron ore blend including specular iron ore up to 30% blended with goethite iron ore.

2.Iron ore blend as claimed in claim 1 comprising iron ore blend including
specular iron ore with a size fractions below 10 mm up to 30% by weight, with goethite iron ore of less than or equal to 30% of size less than 10 mm and remaining other hematite iron ore less than 3 mm size, wherein 30-50% of the iron ores should be below 100# size fractions, along with fluxes including lime stone, dolomite, and coal/coke, return fines, calcined lime.

3.Iron ore blend as claimed in anyone of claims 1 or 2 which would favour improvement of sintering selectively by improvement in anyone or more of the following with respect to blend including specular iron ore of upto 30 % free of any goethite iron ore:
Increase in Shatter Index (%) by 1 to 2 %;
Increase in Tumbler Index (%) by 1 to 3 %;
Increase in Product Yield, +5mm (%) by 1 to 3 %;
Decrease in Sintering Time (min) by 1 to 6 %;
Increase in Productivity (t/h/m2), +5mm, (%) by 1 to 10 %;
Increase in Wind Box temp. (ºC) by 0 to 50 %.

4. A process for carrying out efficient sintering of iron ore blend including specular iron ore avoiding the deteriorating nature of specular iron ore having characteristics hard texture, undesirable particle size and shape, poor assimilation performance and low reactivity at high temperature comprising:
providing iron ore blend including specular iron ore up to 30% alongwith with goethite iron ore;
carrying out the sintering of said iron ore blend including said specular iron ore up to 30% alongwith with goethite iron ore with selective improvement of sintering even in the presence of specular iron ore of anyone or more of
Increase in Shatter Index (%) by 1 to 2 %;
Increase in Tumbler Index (%) by 1 to 3 %;
Increase in Product Yield, +5mm (%) by 1 to 3 %;
Decrease in Sintering Time (min) by 1 to 6 %;
Increase in Productivity (t/h/m2), +5mm, (%) by 1 to 10 %;
Increase in Wind Box temp. (ºC) by 0 to 50 %.

5. A process as claimed in claim 4 wherein said step of providing of iron ore blend comprises
preparing dry sinter mix by blending specular iron ore with a size fractions below 10 mm up to 30% by weight, with goethite iron ore of less than or equal to 30% of size less than 10 mm .

6. A process as claimed in anyone of claims 4 or 5 comprising

preparing dry sinter mix by blending specular iron ore with a size fractions below 10 mm up to 30% by weight, with goethite iron ore of less than or equal to 30% of size less than 10 mm and remaining other hematite iron ore less than 3 mm size, wherein 30-50% of the iron ores should be below 100# size fractions, along with fluxes including lime stone, dolomite, and coal/coke, return fines, calcined lime, in a balling drum; followed by

agglomerating the sinter mix in presence of moisture using a drum mixer;

subjecting said agglomerated mix so obtained to sintering at required sintering parameters/condition, whereby the negative influence of presence of specular nature of iron ore is neutralized favouring improved sinter quality and sinter plant performance.

7. A process as claimed in anyone of claims 4 to 6 wherein said step of dry mixing in balling drum is carried out @ 20 rpm for 300 seconds; and
said step of agglomerating is carried out in drum mixer by wet mixing @ 20 rpm for 480 seconds.

8. A process as claimed in anyone of claims 4 to 7 carried out with
said step of sintering carried out with ignition condition comprising
Suction air flow volume before ignition:2.0 m3/min;
Ignition holding time:60 sec;
Suction pressure after ignition:-1200 mm H2O.

9. A process as claimed in anyone of claim 4 to 8 wherein said sintering is carried out with Bed Height: 700 mm (constant) having Hearth Layer: 60 mm and comprises formation of complex slag to form calcium ferrite which turns out to silico-ferrite of calcium and aluminium through diffusion of silica and alumina at high temperature in the range of 1100°C to 1300°C.

10. A process as claimed in anyone of claims 4 to 9 wherein raw materials involved comprises:

Blend FeT FeO Fe2O3 SiO2 Al2O3 CaO MgO LOI
Specular Iron Ore (I/O)-1 58.27 -- 83.24 7.95 3.68 0.05 0.04 3.72
I/O-2 62.76 -- 89.66 3.68 2.91 0.06 0.07 2.78
I/O-3 57.85 -- 82.64 7.95 4.45 0.05 0.04 3.90
I/O-4 (Goethite I/O) 58.41 -- 83.44 6.03 2.97 0.05 0.04 6.73
Sinter return fines (SRF) 52.88 8.68 -- 6.54 2.98 10.00 2.52 --
Limestone -- -- 0.93 0.92 0.20 49.84 4.26 42.80
Dolomite -- -- 1.61 0.20 0.12 31.43 19.78 46.19
Calcined Lime -- -- 0.26 1.10 0.37 93.59 1.86 2.52
Ash VM S FC
Coke breeze 20.07 3.45 0.59 76.48

11. A process as claimed in anyone of claims 4to 10 wherein proportion of constituents in said agglomerated sinter mix comprising

Specular iron ore: 5 to 30 preferably 30 wt%;
Goethite iron ore: 0 to 40 preferably 30 wt%;
Other hematite iron ores: 30 to 75 preferably 75 wt%;
Return fines : 20 to 40 preferably 34 wt%;
Lime stone: 5 to 10 preferably 7.2 wt%;
Dolomite: 5 to 10 preferably 6.1 wt%;
Calcined lime: 1.5 to 2.5 preferably 2.2 wt%;
Coal/Coke: 3.5 to 4.5 preferably 4.2 wt%;
Moisture : 7 to 9 preferably 7.5 wt%.

12. A process as claimed in anyone of claims 4to 11 whereinsize analysis of iron ore, flux, return fines and solid fuels comprising
(i)
SEIVES +10 + 8 +6.3 +5 +3.15 +1 +0.5 +100 -100
mm #
Specular I/O-1 11.05 5.95 6.58 2.49 9.09 17.95 5.92 10.16 30.80
I/O-2 --- --- --- --- 2.55 27.53 11.84 16.04 42.04
I/O-3 --- --- --- --- 3.64 15.53 12.78 17.53 50.52
I/O-4 (Goethite I/O) 7.15 7.82 8.76 3.29 15.42 22.94 6.64 10.16 17.82

(ii)
SEIVES +5 +3.15 +1 -1 -3.15
mm
Limestone 0.35 6.74 56.94 35.97 92.91
Dolomite 0.42 8.45 54.43 36.70 91.14
SEIVES +8 +5 - 5 Cum. +5
mm
Return Fines 0.89 24.16 74.95 25.05
SEIVES +5 +3.15 +1 +0.5 -0.5 Cum -3.15
mm
Solid Fuel (Coke Breeze) 1.31 6.04 48.32 21.67 22.67 92.65

Dated this the 24th day of June, 2019
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199
, Description:FIELD OF THE INVENTION
The present invention relates to a method of sintering of iron ore blend comprising specular iron ore by blending with hematite and hydroxide iron ore mineral mainly goethite iron ore to overcome the deteriorating nature of specular iron ore having characteristics hard texture, undesirable particle size and shape, poor assimilation performance and low reactivity at high temperature. Such features are detrimental to sinter plant performance, sinter quality and plant productivity. More particularly, the present invention is directed to provide a process to deal with sinter grade specular iron ore (Size < 10 mm) and to achieve better plant productivity and sinter quality by blending with hydroxide iron ore mineral mainly goethite iron ore to attain sustainable production with increased sinter strength. In this invention specular iron ore up to 30% is blended with goethite iron ore (less than or equal to 30% of size less than 10 mm) and remaining other hematite iron ore (less than 3mm size wherein 30-50% of the iron ore should be below 100# size fractions) so that the negative influence of specular nature of iron ore can be neutralized.

BACKGROUND OF THE INVENTION
According to the analysis of world iron ore reserves, specular hematite iron ore is widely distributed in the world and abundant in some countries such as Canada and Brazil. However, due to its inherent characteristics like hard texture, undesirable particle size and shape, dense and smooth particle surface, they show poor assimilation performance with other sinter mix ingredients. Such type of iron ore shows smooth surface, poor hydrophilicity, long and flat particle shape, resulting granulation difficulties affect bed permeability during sintering process. It is hard to be used in large amount for the production of sinter and pellet as they possess difficulty in melting and granules formation, so it has not yet been widely applied in production. Many steel mills like Baosteel, Wisco, Hansteel and Valin Group found that, adding large amount of specularite in sinter mixture would deteriorate mixture’s granulating and green sinter bed’s permeability, worsen productivity and tumble index of sinter and increase solid fuel consumption. As a result, the blend ratios of specularite in sintering plant are normally 3%–10%.

To overcome the above said shortcomings of the specular iron ore, prior art suggested following ways to increase the amount of specular iron ore in sinter mix.

1. Jiang et. al. published a paper entitled “Composite agglomeration process (CAP) for preparing blast furnace burden” in Ironmaking and steelmaking journal (Ironmaking and Steelmaking, 2010, 37(1), pp 1-8) wherein they explained a new process to increase the specular iron ore through sinter making. They mainly focused on modification of surface properties through strengthening granulating process by ameliorating agglomeration process like CAP (composite agglomeration process) or adding binder, and selective ore proportioning for sintering. The proportion of specular ores can be increased to as high as 40-50% with an achievement of satisfactory results using Composite Agglomeration Process (CAP), an innovative agglomeration process invented by Central South University. The process has the following merits: making reasonable utilization of different iron ore resources; improving the quality and output of sinters; manufacturing sinters with low basicity; significantly reducing energy consumption, etc. In this invention negative influence of specular nature of iron ore can be neutralized by blending iron ore of goethite nature.

This process requires additional capital expenditure and space requirement.

2. Jian et. al., described a new process in his paper entitled “Improving Sintering Performance of Specularite Concentrates by Pre-briquetting Process” published in ISIJ International, 2016, 56(5), pp. 777–785; wherein the specular iron ore usage is increased up to 24–36% through pre-briquetting process of specularite into a lump particles which has resulted in improved green bed permeability, sintering speed and sinter productivity.
This process requires additional capital expenditure and space requirement.

3. CN104451129A (Blended ore structure capable of increasing usage rate of specular hematite)
This invention discloses to increase specularite fractions in sintering through blending with other raw material and ingredients. They claimed that specularite hematite with particle size less than or equal to 10 mm can be increased to 10-40% in sinter mix along with 10-20% of other hematite with the particle sizes being 3.15-10mm, 30%-40% of limonite with the particle sizes being less than or equal to 10mm, and the balance being other iron ore with the particle sizes being smaller than or equal to 10mm. In general, the required iron ore size fractions in sinter making is less than or equal to 10 mm. In the present invention, the inventors did not disclose the required size fractions of other iron ore and limonite iron ore for increased specularite fractions with sustainable sinter quality.
This shortcoming is addressed in the present invention by accommodating finer fractions of other ores. The finer fractions of other hematite particles such as below 150 microns in the weight proportion range of 30-50% improves the granulometry of specularite and enhance the reaction kinetics of iron ore during sintering, improves the bonding and sinter strength. The hydrated minerals goethite is being used in the present invention which generates high volume of liquid phase forming thicker combustion zone results in better bonding with specularite and thus improved sinter quality and sintering performances.
4. CN104451133A (Sintered ore containing specular hematite and preparation method of sintered ore)

The invention discloses sintered ore containing specular hematite wherein the raw materials in percentage by weight are as follows: 2-60 percent of specular hematite of which the granularity is less than or equal to 1mm, 20-40 percent of return mine of which the granularity is less than or equal to 5mm, 3-5 percent of fuel of which the granularity is less than or equal to 4mm, 8-15 percent of flux of which the granularity is less than or equal to 4mm, and an additional adhesive which accounts for 0.5-6 percent of the total weight of the raw materials.

In this prior art the specularite usage has been increased up to 60% of size fractions below 1mm. In this process the major challenge is to grind the hard specularite to below 1 mm which is very difficult due to its inherent characteristics and harder in nature. Moreover, the binder cost adds up to the manufacturing cost of sinter making.

In the present invention, inventors are able to utilize up to 30% of specular iron ore without any change in existing process, no additional binder requirement and thus no additional capital and consumable requirements.

OBJECTS OF THE INVENTION:
The basic object of the present invention is directed to a process for sintering of iron ore involving a ore blend composition favouring effective utilization of specular iron ores with improved sinter quality and plant productivity and neutralizing the negative influence of specular nature of iron ore.

A further object of the present invention is directed to a process of sintering iron ore blend including specular iron ore involving use of goethite iron ore alongwith other hematite ore to assimilate and form melt with the specular iron ore and prevent detrimental impact.

A still further object of the present invention is directed to a process of sintering of specular iron ore involving a blend prepared by mixing with goethite iron ore in order to overcome the hard texture and poor high temperature reactivity of specular iron ore.

A still further object of the present invention is directed to a process of sintering of specular iron ore wherein formation of complex slag to form calcium ferrite which turns out to silico-ferrite of calcium and aluminium through diffusion of silica and alumina at high temperature in the range of 1100°C to 1300°C enable achieving desired improved properties of sinter product.
A still further object of the present invention is directed to a process of sintering of specular iron orecontaining ore blend wherein presence of goethite iron ore helps to improve granulometry and thus bed permeability, melt formation which provides more strength to the sinter as compared to diffusion bonding.

A still further object of the present invention is directed to a process of sintering of specular iron ore containing ore blend including goethite and other hematite ore having selective size fraction distribution wherein 30-50% of ores should be below 150 microns size favouring better agglomeration/granulation.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to iron ore blend for sintering including specular iron ore suitable for improved sinter performance comprising:
iron ore blend including specular iron ore up to 30% blended with goethite iron ore.

A further aspect of the present invention is directed to said iron ore blend comprising iron ore blend including
specular iron ore with a size fractions below 10 mm up to 30% by weight, with goethite iron ore of less than or equal to 30% of size less than 10 mm and remaining other hematite iron ore less than 3 mm size, wherein 30-50% of the iron ores should be below 100# size fractions, along with fluxes including lime stone, dolomite, and coal/coke, return fines, calcined lime.

A still further aspect of the present invention is directed to iron ore blend which would favour improvement of sintering selectively by improvement in anyone or more of the following with respect to blend including specular iron ore of upto 30 % free of any goethite iron ore:
Increase in Shatter Index (%) by 1 to 2 %;
Increase in Tumbler Index (%) by 1 to 3 %;
Increase in Product Yield, +5mm (%) by 1 to 3 %;
Decrease in Sintering Time (min) by 1 to 6 %;
Increase in Productivity (t/h/m2), +5mm, (%) by 1 to 10 %;
Increase in Wind Box temp. (ºC) by 0 to 50 %.

A still further aspect of the present invention is directed to a process for carrying out efficient sintering of iron ore blend including specular iron ore avoiding the deteriorating nature of specular iron ore having characteristics hard texture, undesirable particle size and shape, poor assimilation performance and low reactivity at high temperature comprising:
providing iron ore blend including specular iron ore up to 30% alongwith with goethite iron ore;
carrying out the sintering of said iron ore blend including said specular iron ore up to 30% alongwith with goethite iron ore with selective improvement of sintering even in the presence of specular iron ore of anyone or more of
Increase in Shatter Index (%) by 1 to 2 %;
Increase in Tumbler Index (%) by 1 to 3 %;
Increase in Product Yield, +5mm (%) by 1 to 3 %;
Decrease in Sintering Time (min) by 1 to 6 %;
Increase in Productivity (t/h/m2), +5mm, (%) by 1 to 10 %;
Increase in Wind Box temp. (ºC) by 0 to 50 %.

A still further aspect of the present invention is directed to said process wherein said step of providing of iron ore blend comprises
preparing dry sinter mix by blending specular iron ore with a size fractions below 10 mm up to 30% by weight, with goethite iron ore of less than or equal to 30% of size less than 10 mm .

Another aspect of the present invention is directed tosaid process comprising

preparing dry sinter mix by blending specular iron ore with a size fractions below 10 mm up to 30% by weight, with goethite iron ore of less than or equal to 30% of size less than 10 mm and remaining other hematite iron ore less than 3 mm size, wherein 30-50% of the iron ores should be below 100# size fractions, along with fluxes including lime stone, dolomite, and coal/coke, return fines, calcined lime, in a balling drum; followed by

agglomerating the sinter mix in presence of moisture using a drum mixer;

subjecting said agglomerated mix so obtained to sintering at required sintering parameters/condition, whereby the negative influence of presence of specular nature of iron ore is neutralized favouring improved sinter quality and sinter plant performance.

Yet another aspect of the present invention is directed to said process wherein said step of dry mixing in balling drum is carried out @ 20 rpm for 300 seconds; and said step of agglomerating is carried out in drum mixer by wet mixing @ 20 rpm for 480 seconds.

A further aspect of the present invention is directed to a process carried out with
said step of sintering carried out with ignition condition comprising
Suction air flow volume before ignition:2.0 m3/min;
Ignition holding time:60 sec;
Suction pressure after ignition:-1200 mm H2O.

A still further aspect of the present invention is directed to a process wherein said sintering is carried out with Bed Height: 700 mm (constant) having Hearth Layer: 60 mm and comprises formation of complex slag to form calcium ferrite which turns out to silico-ferrite of calcium and aluminium through diffusion of silica and alumina at high temperature in the range of 1100°C to 1300°C.

A still further aspect of the present invention is directed to a process wherein raw materials involved comprises:
Blend FeT FeO Fe2O3 SiO2 Al2O3 CaO MgO LOI
Specular Iron Ore (I/O)-1 58.27 -- 83.24 7.95 3.68 0.05 0.04 3.72
I/O-2 62.76 -- 89.66 3.68 2.91 0.06 0.07 2.78
I/O-3 57.85 -- 82.64 7.95 4.45 0.05 0.04 3.90
I/O-4 (Goethite I/O) 58.41 -- 83.44 6.03 2.97 0.05 0.04 6.73
Sinter return fines (SRF) 52.88 8.68 -- 6.54 2.98 10.00 2.52 --
Limestone -- -- 0.93 0.92 0.20 49.84 4.26 42.80
Dolomite -- -- 1.61 0.20 0.12 31.43 19.78 46.19
Calcined Lime -- -- 0.26 1.10 0.37 93.59 1.86 2.52
Ash VM S FC
Coke breeze 20.07 3.45 0.59 76.48

Another aspect of the present invention is directed to a process wherein proportion of constituents in said agglomerated sinter mix comprising
Specular iron ore: 5 to 30 preferably 30 wt%;
Goethite iron ore: 0 to 40 preferably 30 wt%;
Other hematite iron ores: 30 to 75 preferably 75 wt%;
Return fines : 20 to 40 preferably 34 wt%;
Lime stone: 5 to 10 preferably 7.2 wt%;
Dolomite: 5 to 10 preferably 6.1 wt%;
Calcined lime: 1.5 to 2.5 preferably 2.2 wt%;
Coal/Coke: 3.5 to 4.5 preferably 4.2 wt%;
Moisture : 7 to 9 preferably 7.5 wt%.

Yet another aspect of the present invention is directed to a process wherein size analysis of iron ore, flux, return fines and solid fuels comprising
(i)
SEIVES +10 + 8 +6.3 +5 +3.15 +1 +0.5 +100 -100
mm #
Specular I/O-1 11.05 5.95 6.58 2.49 9.09 17.95 5.92 10.16 30.80
I/O-2 --- --- --- --- 2.55 27.53 11.84 16.04 42.04
I/O-3 --- --- --- --- 3.64 15.53 12.78 17.53 50.52
I/O-4 (Goethite I/O) 7.15 7.82 8.76 3.29 15.42 22.94 6.64 10.16 17.82

(ii)
SEIVES +5 +3.15 +1 -1 -3.15
mm
Limestone 0.35 6.74 56.94 35.97 92.91
Dolomite 0.42 8.45 54.43 36.70 91.14
SEIVES +8 +5 - 5 Cum. +5
mm
Return Fines 0.89 24.16 74.95 25.05
SEIVES +5 +3.15 +1 +0.5 -0.5 Cum -3.15
mm
Solid Fuel (Coke Breeze) 1.31 6.04 48.32 21.67 22.67 92.65

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 and example.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: shows the Mineralogy of specular iron ore.
Figure 2: shows the Electron microscopy of specular iron ore with energy dispersive spectra showing elements present in it using electron probe micro analysis coupled with energy dispersive spectroscopy (EPMA-EDS).
Figure 3: is the Pictorial representation of the sinter quality and productivity of sintering process comprising of usage of increased fractions of specular iron ore.
Figure 4: is the Pictorial representation of the sinter quality and productivity of sintering process comprising of usage of specular iron ore according to present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention is directed to a process for sintering of iron ore blend comprising specular iron ore for effective utilization of specular iron ores in sinter making for improved sinter quality and plant productivity. The step involves blending specular iron ore with goethite iron ore wherein the specular iron ores are charged along with the goethite iron ore and remaining ingredients into the drum mixer for dry and wet mixing for required time to achieve completely homogeneous mix and granules for sintering.

In the present invention, the hard texture of specular iron ore is blended with goethite iron ore for sinter preparation. This presence of goethite iron ore helps to improve granulometry and thus bed permeability, melt formation which provides more strength to the sinter as compared to diffusion bonding.

The invented process is directed to increased usage of specular iron ore through blending to achieve desired sinter mix without deterioration of the sinter quality and sinter plant performance, wherein specular iron ore with a size fractions below 10 mm is blended with the goethite iron ore having less than 10mm size fractions and other hematite iron ore having size fractions below 3 mm of which 30-50% should be below 150 microns size, wherein addition of said goethite iron ore with other hematite iron ore for agglomerating/granulating the sinter mix with desired size fractions, thus favouring sustained superior plant performance and sinter quality.

It is clearly apparent from Figure 1 that, the iron ore -1 contains needle shaped structure also known as specular structure and mirror structure iron ore.

It is clearly apparent from Figure 2 that, the specular iron ore contains very fine needle type structure as well the platy kind of structure. It is also clear from the figure that the grains are smooth. Elemental analysis of the iron ore reveals the presence of total iron in it.

It is clearly apparent from Figure 2 that, with the increased fractions of specular iron ore in the blend as shown in Table 2 without having goethite iron ore in blend, the sinter quality and productivity deteriorates with increased fractions of specular iron ore

It is clearly apparent from Figure 3 that at 30% specular iron ore in the blend with 30% goethite iron ore in blend as shown in Table 3, the sinter quality and productivity improved.

Experimental Conditions
? Approximately 90 kg of sinter mix blended using balling drum. Blending condition: mixing @ 20 rpm for 300 seconds.
? One kg of each blended sinter mix sample was dried and analyzed for particle size distribution.
? Agglomerated the sinter mix in presence of moisture using a drum mixer; Agglomerating condition: mixing @ 20 rpm for 480 seconds.
? Sintered the material in pot grate with ignition conditions as under:
Ignition conditions:

Suction air flow volume before ignition 2.0 m3/min
Ignition holding time 60 sec
Suction pressure after ignition -1200 mm H2O

• Raw materials were screened to obtain the desired size as given below.
Material Size
Base Mix As received
Calcined lime - 0.212 mm
Coke breeze - 3.15 mm

• Bed Height: 700 mm (constant), Hearth Layer: 60 mm

Blend FeT FeO Fe2O3 SiO2 Al2O3 CaO MgO LOI
Specular Iron Ore (I/O)-1 58.27 -- 83.24 7.95 3.68 0.05 0.04 3.72
I/O-2 62.76 -- 89.66 3.68 2.91 0.06 0.07 2.78
I/O-3 57.85 -- 82.64 7.95 4.45 0.05 0.04 3.90
I/O-4 (Goethite I/O) 58.41 -- 83.44 6.03 2.97 0.05 0.04 6.73
Sinter return fines (SRF) 52.88 8.68 -- 6.54 2.98 10.00 2.52 --
Limestone -- -- 0.93 0.92 0.20 49.84 4.26 42.80
Dolomite -- -- 1.61 0.20 0.12 31.43 19.78 46.19
Calcined Lime -- -- 0.26 1.10 0.37 93.59 1.86 2.52
Ash VM S FC
Coke breeze 20.07 3.45 0.59 76.48
Table-1: Chemical Analysis of Raw Materials (wt.%):
Table-2: Sinter Mix proportions used for the experimental trials (wt. %):
Specular iron ore,% 0 10 20 25 30
Experiment No. 1 2 3 4 5
Total Iron ore (I/O) 47.11 47.10 47.10 47.10 47.10
Specular (I/O)-1 0.00 4.71 9.42 11.78 14.13
I/O-2 32.96 32.97 32.97 32.97 32.50
I/O-3 14.13 9.42 4.71 2.36 0.47
Return fines (R/F) 34.00 34.00 34.00 34.00 34.00
Limestone 6.40 6.40 6.40 6.40 6.40
Dolomite 6.11 6.10 6.10 6.10 6.10
Calcined lime 2.20 2.20 2.20 2.20 2.20
Coal/Coke 4.20 4.20 4.20 4.20 4.20
TOTAL 100 100 100 100 100
Exp 1: Sintering of raw mix having 0% specular iron ore in the blend.
Exp 2: Sintering of raw mix having 10% specular iron ore in the blend.
Exp 3: Sintering of raw mix having 20% specular iron ore in the blend.
Exp 4: Sintering of raw mix having 25% specular iron ore in the blend.
Exp 5: Sintering of raw mix having 30% specular iron ore in the blend.

Table-3: Sinter Mix proportions used for the experimental trials under presentinventions (wt. %):

%TIOM in I/O blend
(~ 30% Goethite I/O in blend) 0 20 30
Experiment No. 1 6 7
Total I/O 47.11 46.79 46.30
Specular (I/O)-1 0.00 9.36 13.89
I/O-2 32.96 23.40 18.52
I/O-3 14.13 0.00 0.00
I/O-4 (Goethite I/O) 0.00 14.03 13.89
Return fines (R/F) 34.00 34.00 34.00
Limestone 6.40 6.70 7.20
Dolomite 6.11 6.10 6.10
Calcined lime 2.20 2.20 2.20
Coal/Coke 4.20 4.20 4.20
TOTAL 100 100 100

Exp 1: Sintering of raw mix having 0% specular iron ore in the blend with 0% goethite iron ore
Exp 6: Sintering of raw mix having 20% specular iron ore in the blend with 30% goethite iron ore
Exp 7: Sintering of raw mix having 30% specular iron ore in the blend with 30% goethite iron ore
Table-4: Sintering performance and sinter qualities with increased fractions of specularite
Specular I/O wt. fractions in IOF blend, % 0 10 20 25 30
Experiments 1 2 3 4 5
Shatter Index (%) 71.31 69.57 69.63 69.48 69.12
Tumbler Index (%) 69.27 65.60 64.67 65.73 65.80
Product Yield, +5mm (%) 82.17 82.81 81.47 81.45 80.25
Sintering Time (min) 20.3 19.3 20.3 21.1 21.4
Sinter Productivity (t/h/m2), +5mm, (%) 2.12 2.34 2.15 2.07 2.02
Wind Box temp. (ºC) 335 331 329 297 289
Table-5: Sintering performance and sinter qualities with increased fractions of specularite with almost 30% of goethite iron ore in blend
% Specularite in IOF blend 0 20 30
(with ~ 30 wt.% goethite I/O in I/O blend)
Experiments 1 6 7
Shatter Index (%) 71.31 70.49 70.33
Tumbler Index (%) 69.27 67.37 67.30
Product Yield, +5mm (%) 82.17 82.27 81.90
Sintering Time (min) 20.3 18 20.3
Productivity (t/h/m2), +5mm, (%) 2.12 2.49 2.17
Wind Box temp. (ºC) 335 368 427

Table 6: Typical Size analysis of iron ore, flux, return fines and solid fuels
SEIVES +10 + 8 +6.3 +5 +3.15 +1 +0.5 +100 -100
mm #
Specular I/O-1 11.05 5.95 6.58 2.49 9.09 17.95 5.92 10.16 30.80
I/O-2 --- --- --- --- 2.55 27.53 11.84 16.04 42.04
I/O-3 --- --- --- --- 3.64 15.53 12.78 17.53 50.52
I/O-4 (Goethite I/O) 7.15 7.82 8.76 3.29 15.42 22.94 6.64 10.16 17.82

SEIVES +5 +3.15 +1 -1 -3.15
mm
Limestone 0.35 6.74 56.94 35.97 92.91
Dolomite 0.42 8.45 54.43 36.70 91.14
SEIVES +8 +5 - 5 Cum. +5
mm
Return Fines 0.89 24.16 74.95 25.05
SEIVES +5 +3.15 +1 +0.5 -0.5 Cum -3.15
mm
Solid Fuel (Coke Breeze) 1.31 6.04 48.32 21.67 22.67 92.65

It is thus possible by way of the present invention to provide a process for sintering iron ore wherein the sinter mix contains up to 30wt% of specular iron ore. In this process, 30% of the specular iron ore of total iron ore blend can be utilized by adding 30% of goethite iron ore of total iron ore blend and remaining 40% another iron ore of any grade, each having defined size distribution.The sinter mix also includes fluxes including lime stone dolomite, coal/coke, return fines, calcined lime, mixture of limestone/dolomite/return fines, coal and coke, in selected proportion.
The process include a first step of preparing the sinter mix wherein all sinter raw mix including specular and goethite iron ore are added in the drum mixer, firstly, for dry mixing and then wet mixing and then charged for sintering. The agglomerated sinter mix is then sintered with selected operating parameters by subjecting the charge above to heating thereby producing a semi-molten mass, this in turn solidifies into porous pieces of sinter having the required size and strength, suitable for feeding into blast furnace.
The sintering processas above is carried out for improving the melt formation and assimilation process. The process involves formation of complex slag to form calcium ferrite which turns out to silico-ferrite of calcium and aluminium through diffusion of silica and alumina at high temperature in the range of 1100°C to 1300°C, thus achieving sustained superior properties of sinter product.