Claims:1. A sinter mix comprising:
Iron ore 59.71 + 2 wt%, Coke breeze 6.5 + 2 wt%, Burnt Lime 1 + .05 wt%, a de-phosphorised LD slag 3.0-14.1 wt%, limestone 4.9-7.6 wt%, dolomite 4.4-6.0 wt% and return fines 15 + 2 wt%.

2. The sinter mix as claimed in claim 1, wherein the de-phosphorised LD slag comprises Fe(T): 49.94-53.85 wt%, FeO: 10.32-15.09 wt%, CaO: 11.16-16.02 wt%, SiO2: 5.27-8.24 wt%, MgO: 2.43-2.70 wt%, Al2O3: 3.10-3.7 wt% and P: 0.07¬-0.28 wt%.

3. The sinter mix as claimed in claim 1, wherein chemistry of the sinter is Fe(T): 47.16-53.85 wt%, FeO: 11.61-15.09 wt%, CaO: 11.16-16.02 wt%, SiO2: 5.60-8.24 wt%, MgO: 2.27-3.18 wt%, Al2O3: 2.83-4.21 wt%, P: 0.06-0.37 wt%.

4. The sinter mix as claimed in claim 1, wherein Tumbler Index of the sinter obtained from the sinter mix is 53.95-64.38.

5. The sinter mix as claimed in claim 1, wherein RDI of the sinter obtained from the sinter mix is 12.50-16.30.

6. The sinter mix as claimed in claim 1, wherein the de-phosphorised LD slag replaces Limestone and pyroxenite.

7. The sinter mix as claimed in claim 1, wherein the size of the return fines is less than 5mm.

8. The sinter mix as claimed in claim 1, wherein the size of the De-phos LD Slag in the sinter mix is 2-3% for size +3.15 mm, 95-97% for size -3.15+2 mm and rest for size -2+1 mm and -1 mm. , Description:TECHNICAL FIELD
The present disclosure generally relates to a field of metallurgy. Particularly, but not exclusively, the present disclosure relates to steelmaking process. Further embodiments of the present disclosure disclose sinters.

BACKGROUND OF THE DISCLOSURE
Steel is an alloy of iron and carbon and is by far the most widely used material for building the world’s infrastructure and industries. Steels are used in fabricating almost everything, from sewing needles to oil tankers. In addition, the tools required to build and manufacture are made of steel as well. Conventionally, for producing steel, raw iron ores which is taken from the earth is fed into the blast furnace plant in the form of pellets or sinters and is subjected to treatment to obtain hot metal iron in liquid state. The hot metal is then subjected to further treatment to obtain steel i.e. the hot metal undergoes primary steelmaking process and secondary steelmaking process to obtain steel.

A large percentage of iron ore fines generated in the steel industry are predominantly recycled via the agglomeration making route. Sintering is a generic term that is used to describe a high temperature process in which a raw materials mixture is converted into a particular form of agglomerate known as sinter. Iron ore sinters are suitable porous materials obtained by agglomeration processes of iron ore fine particles. These agglomerates are widely employed in blast furnaces to produce pig iron. Sufficient cold handling strength of sinter is required to minimise fines generation and different processes are used for this purpose. Sinter is produced at relatively low temperatures (~1050ºC) without complete melting of the iron ore particles. Thus, the microstructure of sinter consists largely of unreacted ore particles, bonded by fairly large amount of complex ferrite phase, as well as, partially reduced hematite or magnetite phases. The type and amount of flux and fuel can thus affect the sinter quality.

From steel industries, significant quantities of steel making slag is generated as waste material or by product every day. Slag dumping in the slag yard is not acceptable at many steel plants, as it generates dust, causes loss of thermal energy present in liquid slag and requires considerable land space.

One such alternative to slag dumping can be sinter making. They usually contain considerable quantities of valuable metals and materials. These materials can be used in sinter making as a replacement of other prime raw materials.

The sintering process begins with the preparation of a sinter mixture consisting of iron ore fines, fluxes, solid fuel (called bonding agents in Japan) such as coke breeze, and return fines from the sinter plant and blast furnace as well as recycled ferruginous materials from downstream iron and steelmaking processes.

OBJECTS OF THE DISCLOSURE
An object of the invention is to consume LD slag appropriately in sinter making.

Another object of the invention is to replace prime raw material with the LD slag, a waste as per steel industry.

DETAILED DESCRIPTION OF THE DISCLOSURE
The present invention provides a sinter mix comprising:
Iron ore 59.71 + 2, Coke breeze 6.5 + 2, Burnt Lime 1 + .05, a de-phosphorised LD slag 3.0-14.1, limestone 4.9-7.6, dolomite 4.4-6.0 and return fines 15 + 2 (all in wt%).

The provision of composition as described above ensures effective utilization of the de-phosphorised LD slag at wt% of 3.0-14.1. Further, limestone wt% of 4.9-7.6 is less from what consumed conventionally at (~13 wt.%) and Pyroxenite has not been used at all whereas conventionally it is used at 3-4 wt.%. Usage of de-phosphorised LD slag is quite economical as compared to reduced usage of limestone and Pyroxenite. Further, sinter obtained from the sinter mix have Tumbler Index of 53.95-64.38 and RDI is 12.50-16.30 which is industrially acceptable.

In a preferred embodiment, the de-phosphorised LD slag comprises Fe(T): 49.94-53.85, FeO: 10.32-15.09, CaO: 11.16-16.02, SiO2: 5.27-8.24, MgO: 2.43-2.70, Al2O3: 3.10-3.7 and P: 0.07¬-0.28 (all in wt%).

In another embodiment chemistry of the sinter is Fe(T): 47.16-53.85, FeO: 11.61-15.09, CaO: 11.16-16.02, SiO2: 5.60-8.24, MgO: 2.27-3.18, Al2O3: 2.83-4.21, P: 0.06-0.37 (all in wt%).

In yet another embodiment, Tumbler Index and RDI of the sinter obtained from the sinter mix is 53.95-64.38 and 12.50-16.30 respectively.

In yet another embodiment, the de-phosphorised LD slag replaces Limestone and pyroxenite.

In yet another embodiment, the size of the return fines is less than 5mm.

In yet another embodiment, the size of the De-phos LD Slag in the sinter mix is 2-3% for size +3.15 mm, 95-97% for size -3.15+2 mm and rest for size -2+1 mm and -1 mm.

Description of Preferred Embodiment
In accordance with an embodiment of the invention, a sinter mix comprises Iron ore 59.71 + 2, Coke breeze 6.5 + 2, Burnt Lime 1 + .05, de-phosphorised LD slag 3.0-14.1, limestone 4.9-7.6, dolomite 4.4-6.0 and return fines 15 + 2 all in wt%.

The size distribution of the constituents is shown below in the Table 1:

Table 1
Size in mm Limestone wt% Dolomite wt% Burnt Lime wt% Coke breeze wt% Return fines wt% De-phos LD Slag wt%
+3.15 49.4 19.9 00 25.1 54.6 2-3
-3.15+2 3.0 2.2 00 2.2 4.9 95-97
-2+1 18.1 17.2 00 19.4 31.3 Rest
- 1 29.4 60.7 100 53.3 9.1

The size distribution of the iron ore is shown below in the Table 2:

Table 2
Size distribution of Iron ore
Size in mm wt.%
+10 2.3
-10+8 6.1
-8+6 14.7
-6+3.15 43.3
-3.15+1 15.4
-1+0.25 11.1
-0.25+0.15 2.3
- 0.15 4.8

LD Slag have high Phosphorous content which can be used in sinter making in very limited quantity. The phosphorus tends to deteriorate the final quality of steel product. Phosphorus decreases ductility and impact to toughness, especially in higher carbon steels. There are various methods available in an art to reduce the Phosphorus content from the de-phosphorised LD slag. But it is equally important to evaluate the appropriate sinter chemistry while using de-phosphorised slag.

In accordance with an embodiment of the invention, the de-phosphorised slag comprises is Fe(T): 49.94-53.85, FeO: 10.32-15.09, CaO: 11.16-16.02, SiO2: 5.27-8.24, MgO: 2.43-2.70, Al2O3: 3.10-3.7 and P: 0.07-0.28 (all in wt%).

In accordance with an embodiment of the invention, the chemistry of the sinter is Fe(T): 47.16-53.85, FeO: 11.61-15.09, CaO: 11.16-16.02, SiO2: 5.60-8.24, MgO: 2.27-3.18, Al2O3: 2.83-4.21, P: 0.06-0.37 (all in wt%).

The composition of the sinter mix is so chosen can be well explained from the fact that silica content in the chemistry of the sinter obtained shall not go above 6. At the same time phosphorus in the final chemistry shall not go above 0.8 wt.%. Also, the RDI value and Tumbler Index shall be in industrially permissible range. The industrially accepted value of RDI is < 6 and Tumbler Index is >52.

Role of components in sintering:
Iron ore: it mainly comprises haematitic ore. Also acts as main source of iron with Silica and alumina as gangue.

Coke breeze: it has carbon around 80% and rest volatile material and impurity. It is used to generate temperature for reactions as well as maintain reducing environment for the reactions.

Limestone: Source of CaO. Used to bring down the melting point of iron ore by forming low temperature melting phase. It also helps in formation of bonding matrix which improves the cold strength of sinter required for transportation to blast furnace

Burnt Lime: It act as a source of MgO which is used to stabilize the required phases (magnetite formation) required for sinter high temperature strength. Generally used as alternative of pyroxenite. Especially in case when SiO2 is supplied from some other source.

De-phosphorised LD slag: in accordance with an embodiment, it is used as a source slag has calcium silicates and can be used as flux for sinter making.

Dolomite: Acts as a source of MgO, use to stabilize the required phases (magnetite formation) required for sinter high temperature strength. Generally used as alternative of pyroxenite. Especially in case when SiO2 is supplied from some other source
Return fines: These are sinter below 5 mm returned from blast furnace due to fine size. Have similar chemistry as of sinter and are recycled.

The Tumbler Index of the sinter obtained the sinter mix is 53.95-64.38.

The RDI of the sinter obtained the sinter mix is 12.50-16.30.

The de-phosphorised LD slag replaces Limestone (CaCO3) and pyroxenite (MgO.SiO2). Conventionally, the amount of limestone is ~13 wt.% and Pyroxenite 3-4 wt.% depending on the basicity requirement. As per the embodiments of the invention the consumption of Pyroxenite has been reduced to nil. Also, the consumption of limestone has been drastically reduced to 4.9 to 7.6 wt%.

The sinter mix is further mixed in a mixing drum at sinter plant and lime fines and moisture as per the requirement is added for granulation.

The sinter mix is charged into a sinter machine for assimilation of cake and filled upto a height of 600 cm. The top of the sinter mix is ignited using a movable ignition/burner hood fuelled by coke oven gas while suction is applied across the bed. Ignition temperature is maintained at 1500 °C while suction during ignition is maintained at 600 mmWC. The speed of the belt is such that ignition is continued for 2 minutes and after the ignition process the suction is increased to 1500 mmWC.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

Any possible combination of two or more of the embodiments described herein is comprised within the scope of the present disclosure.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

The above-mentioned process for producing agglomerates of sinter and its benefit can be validated by the following examples. The following illustrations in form of examples are described to bring more clarity of the invention and should not be considered as limitation or drawback of the invention.

EXAMPLES
Raw materials were weighed in the proportions in the experiments as per various Tables 3-8 to get the desired sinter mix chemistry and processed for sinter making.

Table 3
Materials Weight, % Tumbler Index RDI
Iron ore 61.5 56.3 14.9
Coke breeze 6.5
Burnt Lime 1.0
De-phosphorised LD slag 3.0
Limestone 7.6
Dolomite 5.5
Return fines 15
Pyroxenite 00.0

Table 4
Materials Weight, % Tumbler Index RDI
Iron ore 60.7 55.8 16.3
Coke breeze 6.5
Burnt Lime 1.0
De-phosphorised LD slag 4.1
Limestone 6.7
Dolomite 6.0
Return fines 15.0
Pyroxenite 00.0

Table 5
Materials Weight, % Tumbler Index RDI
Iron ore 60.0 60.95 16.3
Coke breeze 6.5
Burnt Lime 1.0
De-phosphorised LD slag 4.7
Limestone 6.8
Dolomite 6.0
Return fines 15.0
Pyroxenite 00.0

Table 6
Materials Weight, % Tumbler Index RDI
Iron ore 59.2 64.38 12.9
Coke breeze 6.5
Burnt Lime 1
De-phosphorised LD slag 6.6
Limestone 5.9
Dolomite 5.8
Return fines 15.0
Pyroxenite 00.0

Table 7
Materials Weight, % Tumbler Index RDI
Iron ore 57.5 58.22 13.3
Coke breeze 6.5
Burnt Lime 1
De-phosphorised LD slag 9.8
Limestone 5.3
Dolomite 4.9
Return fines 15.0
Pyroxenite 00.0

Table 8
Materials Weight, % Tumbler Index RDI
Iron ore 57.2 56.8 14.8
Coke breeze 6.5
Burnt Lime 1
De-phosphorised LD slag 10.2
Limestone 5.4
Dolomite 4.7
Return fines 15.0
Pyroxenite 00.0

The raw materials as per experiments 1-8 were charged into the granulation drum which was then inclined at 45° and set into rotation at a constant speed of 25 rpm. The materials were allowed to ‘dry mix’ for 15 minutes, following which half the total amount of water was added and mixed intensely for 2 minutes. Rest of the water was then added and mixed. The granules were allowed to grow without mixing during the last minute of granulation. The total amount of moisture used was 6% of base mix and the wet mixing time was 5 minutes.

Sinter mix from the granulation drum was then transferred to the sinter machine as mentioned above in the description. Ignition temperature was 1500 °C while suction during ignition was maintained at 600 mmWC. The sinter machine speed was maintained such that the Ignition was continued for 2 minutes after which the suction was increased. The increased suction was maintained throughout the experiment. The experiment was considered to be complete when the windbox thermocouple recorded the maximum temperature (BTP-Burn through point, Completion of sintering process).

Drop test was conducted on sinter samples thus generated.

It is quite evident from the above-mentioned sinter mix composition from Tables 2-8, that though the composition of the Limestone has been reduced considerably and Pyroxenite didn’t get consumed, their corresponding Tumbler index and RDI have been in permissible industrial range. The industrial permissible range for Tumbler Index is >52 and RDI is < 6.