Claims:We Claim:
1. A granulator drum (103) for an iron-ore sintering system (100), the granulator drum (103) comprising:
a cylindrical vessel (125) defined with an entry side (118) and an exit side (119), and configured to receive fines of raw materials through the entry side (118), wherein the cylindrical vessel (125) is rotatable for mixing and granulating the fines of raw materials;
a spraying unit (113) stationarily disposed in the cylindrical vessel (125) and configured to spray at least one of water and a binder, during rotation of the cylindrical vessel (125) to convert the fines of raw material into micro granules of wet granulated mixture; and
a feeding unit (114) stationarily disposed at the exit side (119) of the cylindrical vessel (125), wherein the feeding unit (114) is configured to supply fines of dried material into the cylindrical vessel (125), such that the micro granules are coated with the fines of the dried material.
2. The granulator drum (103) as claimed in claim 1, wherein the spraying unit (113) is disposed at the entry side (118) of the cylindrical vessel (125).
3. The granulator drum (103) as claimed in claim 1, wherein the feeding unit (114) is disposed at 1/3rd length of the cylindrical vessel (125) towards, the exit side (119).

4. The granulator drum (103) as claimed in claim 1, wherein the feeding unit (114) comprises a plurality of nozzles arranged in series to spray the dried fine material.

5. A method of granulating fines of raw materials for iron-ore sintering, the method comprising:
feeding, fines of raw materials into a granulator drum (103);
rotating, the granulator drum (103) at predetermined speed to mix the fines of the raw material;
spraying, at least one of water and binder by a spraying unit (113) onto the fines of raw materials to form micro granules of a wet granulated mixture; and
feeding fines of dried material into the cylindrical vessel (125) through a feeding unit (114), such that micro granules of the wet granulated mixture are coated with the fines of the dried material.

6. The method as claimed in claim 5, wherein the raw materials are iron ore fines, limestone fines, dolomite or pyroxenite fines, burnt lime, anthracite coal or coke fines and sinter return fines.

7. The method as claimed in claim 5, wherein the dried fine powder are calcined lime fines, calcined dolomite fines, limestones fines, olivine fines and bentonite fines.

8. The method as claimed in claim 5, wherein the feeding unit (114) is disposed at 1/3rd length of the cylindrical vessel (125) towards the exit side (119).

9. The method as claimed in claim 5, wherein the feeding unit (114) is an air pneumatic system (100) with nozzle size (100) less than 90 micron.

10. The method as claimed in claim 5, wherein the dried fine powder is sprayed for about 30 seconds to 60 seconds for coating the micro granules of the wet granulated mixture.

11. The method as claimed in claim 5, wherein coating (110) of the dried fine powder takes place due to centrifugal movement of the micro granules of the granulated mixture.

12. The method as claimed in claim 5, wherein the dried fine powder is sprayed on to the green granules of the wet granulation mixture, without spraying water and binder.

13. The method as claimed in claim 5, wherein the dried fine powder comprises particle size (100) of 45 micron for about 50% to 70% and remaining particle size (100) being 74 micron.

14. The method as claimed in claim 5, wherein the water absorbing capacity of the dried fine powder is about 70 to 150.

15. The method as claimed in claim 5, wherein thickness of coating (110) of the dried fine powder on surface of the green granules range from 80 to 150 micron.

16. The method as claimed in claim 5, wherein dried fine powder coating (110) on surface of the green granules increases granulation index of granulated mixture, which improves permeability of the sinter bed (109).

17. The method as claimed in claim 5, wherein the dried fine powder coating (110) on surface of the green granules removes moisture across the sinter bed (109) and increases the flame front speed.

18. The method as claimed in claim 5, wherein the dried fine powder coating (110) on surface of the micro granules generates a thin slag layer on surface of the micro granules at higher temperature and increases the diffusion rate during subsequent sintering.

19. A method of sintering iron ore, the method comprising:
granulating fines of raw material by a method as claimed in claim 5, to form coated wet granulated mixture;
feeding, the coated wet granulated mixture on to pallet cars (106) movably disposed on a sintering strand (107) by a feeding hopper (105), to form a sinter bed (109) having a plurality of layers of wet granulated mixture layers,
generating, flame front in each of the plurality of layers of wet granulated mixture, by one or more ignition furnaces (108), each positioned adjacent to corresponding feeding station of the plurality of feeding stations (102); and
causing, movement of the flame front in each of the plurality of layers of wet granulated mixture to simultaneously sinter each of the plurality of layers and of wet granulated mixture.

20. The method as claimed in claim 19, wherein the binder is lime fines.

21. The method as claimed in claim 19, wherein the wet granulated mixture includes constituents of iron ore fines, limestone fines, dolomite or pyroxenite fines, burnt lime, anthracite coal or coke fines and sinter return fines.

22. The method as claimed in claim 19, comprising feeding by a hearth feeding station (104) sintered material to form hearth layer (123) at bottom of each of the pallet cars (106).

23. The method as claimed in claim 19, comprises feeding the sintered iron-ore into a crusher (117) and crushed sintered iron-ore into a sinter cooler.

24. A system (100) for sintering iron-ore, the system (100) comprising:
a plurality of feeding stations (102) arranged in series;
a granulator drum (103), configured to receive raw material from each of the plurality of feeding stations (102), wherein the granulator drum (103) is configured to rotate to form a wet granulation mixture, wherein the granulator drum (103) comprises:
a cylindrical vessel (125) defined with an entry side (118) and an exit side (119), and configured to receive fines of raw materials through the entry side (118), wherein the cylindrical vessel (125) is rotatable for mixing and granulating the fines of raw materials;
a spraying unit (113) stationarily disposed in the cylindrical vessel (125) and configured to spray at least one of water and a binder, during rotation of the cylindrical vessel (125) to convert the fines of raw material into micro granules of wet granulated mixture; and
a feeding unit (114) stationarily disposed at the exit side (119) of the cylindrical vessel (125), wherein the feeding unit (114) is configured to supply fines of dried material into the cylindrical vessel (125), such that the micro granules are coated with the fines of the dried material;
a hopper (105), configured to feed the wet granulation mixture from the granulator drum (103) on to pallet cars (106) movably disposed on a sintering strand (107), to form a sinter bed (109) having a plurality of wet granulated mixture layers;
at least one ignition furnace (108), configured to generate a flame front in the sinter bed (109); and
a plurality of wind boxes (116), configured to create suction force for causing movement of the flame front in each of the plurality of wet granulated mixture layers.

25. The system (100) as claimed in claim 24, comprising a hearth feeding station (104) to feed sintered material from a hearth layer (123) at bottom of each of the pallet cars (106).

26. The system (100) as claimed in claim 24, wherein the spraying unit (113) is disposed at the entry side (118) of the cylindrical vessel (125).
27. The system (100) as claimed in claim 24, wherein the feeding unit (114) is disposed at 1/3rd length of the cylindrical vessel (125) towards the exit side (119).

28. The system (100) as claimed in claim 24, wherein the feeding unit (114) comprises a plurality of nozzles arranged in series to spray the dried fine material.

Dated this 30th day of March 2021

Gopinath A S
IN/PA-1852
of K&S Partners
Agent for the Applicant
, Description:FORM 2
THE PATENTS ACT, 1970
[39 of 1970]
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See Section 10 and Rule 13]

TITLE: “A SYSTEM FOR SINTERING IRON ORE AND A METHOD THEREOF”

Name and Address of the Applicant:
TATA STEEL LIMITED, Jamshedpur, Jharkhand, India 831001.

Nationality: INDIAN

The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

TECHNICAL FIELD

Present disclosure generally relates to a field of metallurgy. Particularly, but not exclusively, the present disclosure relates to a system and a method of iron ore sintering. Further, embodiments of the present disclosure disclose a granulator drum for forming a coated granulated mixture.

BACKGROUND OF THE DISCLOSURE

Iron ore sintering is a process in which a mixture of different raw material constituents like iron ore fines, limestone, dolomite, pyroxenite, burnt lime, coke breeze and other metallurgical wastes etc. are agglomerated into larger and porous solid lump, which is generally termed as granulation process. Granulation is a pre-treatment process applied to raw materials, to improve sintering bed permeability, thereby improving the productivity. Granulation of the raw material mixture is done for converting fines into nodules. During the granulation step, water or binder is added to the raw material mixture, while the raw material mixture is being rotated using a granulator drum of the sintering system.

Due to granulation, the finer fraction of iron ore, fluxes, and fuel (with size < 0.2 mm) adhere to the surface of the coarser fraction (with size > 0.7 mm). This results in the formation of small nodules with a mean particle size of ~ 2.75 mm, by a mechanism of nucleation and growth, during the granulation process.

Often in conventional sintering process, there would be deterioration of permeability of the sinter bed. Permeability property of the sinter bed would facilitate atmospheric air to pass from a top portion to a bottom portion of the sinter bed, when suction is created from the bottom portion of the bed, for efficient heat carry over from the top portion to the bottom portion. Permeability of the sinter bed gets deteriorated because of transfer and accumulation of magnetic susceptible materials in the top portion of the sinter bed.

Conventionally, a micro binders are supplied into the sinter plant using a vertical type wet-type ball mill. The effectiveness of micro binder into wet ground iron ore improves cohesive strength between the particles. Following patent publications disclose the aspect of using binders in sintering process.

One of the patent publication US 7,875,097 B2 discloses a sintering process, where raw material proportion include iron-containing dust and/or sludge of 60% or more, coarse grains having a grain size of 2 mm or larger of 20% or more on the weight basis and one-third or less of the total amount of addition of coke breeze, as a fuel. The blend is kneaded and granulated using a vibration kneading granulator, thereby produce granulated grains and the blend is subjected to exterior coating granulation by using a rolling type of granulator. Further, the granulated raw material for sintering is screened, and a fraction having a grain size of 1 mm or larger is used for sintering, making it possible to sinter microparticulate dust and microparticulate sludge as main raw materials, which have conventionally been used only to a limited amount of use.

Another patent publication CN102839280A discloses a selective distribution and granulation method of fuel for enhancing iron ore sintering. The fuel is subjected to two-stage granulation to reduce burning rate of the fuel and improve the burning degree of the fuel, so as to achieve the purpose of enhancing biomass energy sintering. The two-stage granulation comprises preparing biomass fuel, iron ore and quicklime in a granulating disc into a mother nuclide with the granularity of 3-5mm, then mixing with iron ore, limestone, dolomite, quicklime, sinter returns and coke powder (or coal), and carrying out second granulation for 3 to 6 mins in a granulating drum, so as to obtain the mixture before sintering with the biomass fuel wrapped at the core part. By selective distribution technology of the biomass fuel, the biomass fuel can be applied to iron ore sintering so as to successfully substitute for 10-60% of coke powder and with no influence on yield and quality indexes of the sintered ore.

Yet another patent application publication JP2014084468A aims at providing an advance granulation method for a sintering raw material. The advance granulation method comprises: a preliminary granulation step X of adding moisture to a mix of scale powder generated in the steel manufacturing industry only with iron ore or to the mix of the aforementioned with a granulation acceleration material as a binder. Further, the method include stirring at a high speed, kneading, and granulating the mix and a normal granulation step Y of adding a carbonaceous material or the like and moisture to a granulate obtained in the preliminary granulation step X. Furthermore, the method includes performing rolling and granulation with a mixer and a sintering step Z of subjecting the granulate obtained in the normal granulation step Y to sintering treatment.

Further, another patent publication CN107419093A discloses a kind of granulation particle of interior bag carbon materials and method of manufacturing the same. The iron ore powder and raw material containing CaO with size less than 250 µm, carbon materials core of 3~15mm are mixed, granulated and coated around carbon materials core and form an outer layer. In addition, the raw materials for sintering the granulation particle of above-mentioned interior bag carbon materials is loaded on a sintering dolly of sintering machine, formed and load layer and sintering deposit (sintering deposits of interior bag carbon materials) is manufactured using the above-mentioned common combustion heat for granulating carbon materials.

Furthermore, one of the patent publications BR112016000103B1, relates to a small granular coke which forms the core of carbon material and which has a particle diameter of 3 to 15 mm, iron ore powder which forms an outer layer and which has a diameter of particles of no more than 250 µm and a raw material containing chao. The mixture of these materials are inserted in a pelletizer, mixed, granulated, coated on the perimeter of the carbon material core to form the outer layer in it, to create pseudo particles (granulated particles containing material of carbon). A sintering raw material that has granulated particles containing carbon material mixed with normal granulated particles is inserted into a pallet in a sintering machine, a loaded layer is formed, and a sintered ore (sintered ore containing carbon material) is produced in a sintering heat for the carbon material contained in the normal granulated particles. As a result, a sintered mineral containing carbon material that has an iron-containing raw material and a carbon material arranged next to each other can be obtained without using iron oxide powder containing metallic iron, such as dust from rolling mill slag and slag and without restricting the production volume.

Additionally, one of the patent publication JP2017179508A discloses a method for suppressing firing of a carbonaceous material by consuming oxygen, by an oxidization reaction in a coating film during burning a sinter raw material and a capable of avoiding limitations of production amount of the sinter ore.

Flame-front speed has a large influence on sinter quality, productivity, and sintering time (Zhou et al. 2015). The flame-front is the region where coke particles are combusting, having two borders, where coke begins to combust in the initial one and is burned out in the opposite (Loo 2000). However, the temperature at which coke particle starts to combust depends on size, oxygen partial pressure, volatile content, and component types in the coke. The temperature time profiles are measured by means of thermocouples embedded in the sintering bed. Other authors suggest that the flame-front is the area where coke did not reach the combustion temperature, defining a border between combusted zone and initial mix of raw materials (Yang et al. 2006).

With advancement, different techniques have been emerged to increase sinter plant yield in terms of top layer strength and some of these known techniques are described herein.

Support stand for improved permeability in the lower part of the sinter bed is one of a method to improve sinter productivity. The sinter cake load on a combustion-melting zone has a large effect on structure formation of sinter cake, especially in the lower part of the sinter bed. Stand-support sintering technology has been developed to improve bed permeability under the in¬fluence of gravity. With this technique, high sintering bed permeability is achieved in the lower part of the sinter bed as a result of reduced shrinkage due to gravity and suction by supporting the sinter cake load with the vertical plates, attached to the pal¬lets.
On of the patent publication Japanese Patent Publication No. 61-223136 discloses, for instance, that a sintering material layer to be formed on a pallet should be reduced in its density by means of a screen constituted with a plurality of wire materials extending along a flow of sintering material being loaded on the pallet. Further, the sintering material is segregated with fine particles held in an upper layer and with coarse particles held in intermediate and lower layers so as to make the upper layer highly permeable to air with eventual improvement of yield and productivity of a sintered ore. This prior art method, however, has the problem that, since a sintering material of 7% or so in water content is prone to get adhered to the wire materials, the resultant sintering material layer is difficult to stably retain in a segregated state.

A supporting plate clean chute segregation distributor and segregation distributing device for segregating wet granulated raw material and increasing productivity is reported by Kejian Liu et. al., Patent No. CN102032790 (A). However, such method improves the permeability but will not avoid the formation of fragile layer at the top of the sinter bed and, hence more return fines generation is still a concern.
In US 6349833 B1, a method of the magnetic loading of a sintering material is disclosed. Magnetically susceptible sinterable substances of high magnetization and fine substances of slidable dropping at low speed are segregated in great amounts in an upper portion of a sintering material layer deposited on a pallet.
Method for increasing yield of sintering ore by utilizing siderite is described by Zhang Yixian et al in patent no CN103834799A, where sized siderite ore is used as hearth layer and roasted siderite is added to sinter production for calculating overall sinter yield.
Further, according to the above patent publication, in order to ensure the productivity in the middle stage of sintering reaction, negative pressure of suction is increased. However, as shown in the explanatory view disclosed in the above patent publication, although the negative pressure is increased in the intermediate stage as compared with that of the method of the conventional method, a volume of exhaust gas is decreased in portion of the intermediate stage close to the beginning stage of sintering. Therefore, it can be considered that the total productivity cannot be greatly enhanced by the technique disclosed in the above patent publications.
Above citations demand for new design incorporation in sinter plant for production increase, by reducing the sinter fines and increasing the permeability of sinter bed.
The mentioned prior arts involves transfer of magnetic susceptible material present in sinter mix to travel in such a way that it gets accumulated in the top bed of the sinter by virtue of magnetically operated sophisticated chutes or hoppers.
Such methods demand modification in sinter plants which is not economical. Similarly owing to continuous change in the raw mix in sinter, makes it difficult for the magnetic material to get accumulated in the sinter top layer. Many times, extra segregation of such material at the top layer, results in more assimilation and hence deteriorate permeability of the bed.
The segregation also tends to affect the overall segregation of coke and magnetic material across the sinter bed. As top gets richer in magnetic material, the middle layer gets deficient in wustite rich material and hence disturb the overall material balance of the sinter bed.
The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional arts.
SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional techniques are overcome by a system (i.e., granulator drum) and a method, as disclosed and additional advantages are provided through the system as described in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, a granulator drum for an iron-ore sintering system is disclosed. The granulator drum includes a cylindrical vessel, which is defined with an entry side and an exit side and configured to receive fines of raw materials through the entry side. The cylindrical vessel is rotatable for mixing and granulating the fines of raw materials. Further, the granulator drum includes a spraying unit, which is stationarily disposed in the cylindrical vessel. The spraying unit is configured to spray at least one of water and a binder, during rotation of the cylindrical vessel to convert the fines of raw material into micro granules of wet granulated mixture. Furthermore, the granulator drum includes a feeding unit, which is stationarily disposed at the exit side of the cylindrical vessel. The feeding unit is configured to supply fines of dried material into the cylindrical vessel, such that the micro granules are coated with the fines of the dried material.
In an embodiment of the disclosure, the spraying unit is disposed at the entry side of the cylindrical vessel.

In an embodiment of the disclosure, the feeding unit is disposed at 1/3rd length of the cylindrical vessel towards, the exit side.

In an embodiment of the disclosure, the feeding unit comprises a plurality of nozzles arranged in series to spray the dried fine material.

In another non-limiting embodiment of the disclosure, a method of granulating fines of raw materials for iron-ore sintering is disclosed. The method includes feeding fines of raw materials into a granulator drum and rotating the granulator drum at predetermined speed to mix the fines of the raw material. Further, the method incudes spraying at least one of water and binder by a spraying unit onto the fines of raw materials to form micro granules of a wet granulated mixture. Furthermore, the method includes feeding fines of dried material into the cylindrical vessel through a feeding unit, such that micro granules of the wet granulated mixture are coated with the fines of the dried material.

In an embodiment of the disclosure, the raw materials are iron ore fines, limestone fines, dolomite or pyroxenite fines, burnt lime, anthracite coal or coke fines and sinter return fines.

In an embodiment of the disclosure, the dried fine powder are calcined lime fines, calcined dolomite fines, limestones fines, olivine fines and bentonite fines.

In an embodiment of the disclosure, the feeding unit is an air pneumatic system with nozzle size less than 90 micron.

In an embodiment of the disclosure, the dried fine powder is sprayed for about 30 seconds to 60 seconds for coating the micro granules of the wet granulated mixture.

In an embodiment of the present disclosure, coating of the dried fine powder takes place due to centrifugal movement of the micro granules of the granulated mixture.

In an embodiment of the disclosure, the dried fine powder is sprayed on to the green granules of the wet granulation mixture, without spraying water and binder.

In an embodiment of the disclosure, the dried fine powder comprises particle size of 45 micron for about 50% to 70% and remaining particle size being 74 micron.

In an embodiment of the disclosure, the water absorbing capacity of the dried fine powder is about 70 to 150.

In an embodiment of the disclosure, the thickness of coating of the dried fine powder on surface of the green granules range from 80 to 150 micron.

In an embodiment of the disclosure, the dried fine powder coating on surface of the green granules increases granulation index of granulated mixture, which improves permeability of the sinter bed.

In an embodiment of the disclosure, the dried fine powder coating on surface of the green granules removes moisture across the sinter bed and increases the flame front speed.

In an embodiment of the disclosure, the dried fine powder coating on surface of the micro granules generates a thin slag layer on surface of the micro granules at higher temperature and increases the diffusion rate during subsequent sintering.

In yet another non-limiting embodiment of the disclosure, a method of sintering iron ore is disclosed. The method includes granulating fines of raw material in a granulator drum to form a coated wet granulated mixture. Further, the method includes feeding, the coated wet granulated mixture on to pallet cars movably disposed on a sintering strand by a feeding hopper, to form a sinter bed having a plurality of layers of wet granulated mixture layers. Furthermore, the method includes generating flame front in each of the plurality of layers of wet granulated mixture, by one or more ignition furnaces, each positioned adjacent to corresponding feeding station of the plurality of feeding stations. Additionally, the method includes causing movement of the flame front in each of the plurality of layers of wet granulated mixture to simultaneously sinter each of the plurality of layers and of wet granulated mixture.

In an embodiment of the disclosure, the binder is lime fines.

In an embodiment of the disclosure, the method includes feeding by a hearth feeding station sintered material to form hearth layer at bottom of each of the pallet cars.

In an embodiment of the disclosure, the method includes feeding the sintered iron-ore into a crusher and crushed sintered iron-ore into a sinter cooler.

In an still another non-limiting embodiment of the present disclosure, a system for sintering iron-ore is disclosed. The system includes a plurality of feeding stations, which are arranged in series. Further, the system includes a granulator drum, which is configured to receive raw material from each of the plurality of feeding stations. The granulated drum is configured to rotate to form a granulation mixture. The granulator drum includes a cylindrical vessel, which is defined with an entry side and an exit side and configured to receive fines of raw materials through the entry side. The cylindrical vessel is rotatable for mixing and granulating the fines of raw materials. Further, the granulator drum includes a spraying unit which is stationarily disposed in the cylindrical vessel. The spraying unit is configured to spray at least one of water and a binder, during rotation of the cylindrical vessel to convert the fines of raw material into micro granules of wet granulated mixture. Furthermore, the granulator drum includes a feeding unit stationarily disposed at the exit side of the cylindrical vessel. The feeding unit is configured to supply fines of dried material into the cylindrical vessel, such that the micro granules are coated with the fines of the dried material. Further, the system includes a hopper, configured to feed the wet granulated mixture from the granulator drum on to pallet cars, which are movably disposed on a sintering strand, to form a sinter bed having a plurality of wet granulated mixture layers, and at least one ignition furnace, configured to generate a flame front in the sinter bed. Additionally, the system includes a plurality of wind boxes, configured to create suction force for causing movement of the flame front in each of the plurality of wet granulated mixture layers.

In an embodiment of the present disclosure, a hearth feeding station to feed sintered material from a hearth layer at bottom of each of the pallet cars.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Figure. 1 is a schematic representation of a system for sintering iron ore, in accordance with an embodiment of the present disclosure.

Figures. 2a and 2b are schematic representation of granules formed by present disclosure and by conventional sintering process, respectively in accordance with an embodiment of the present disclosure.

Figures. 3a and 3b illustrates schematic representation, depicting air flow pattern in a sinter bed formed by system/method of present disclosure and by conventional sintering process, respectively in accordance with an embodiment of the present disclosure.

Figure. 4 is graphical representation of drop strength and green compressive strength (GCS) of the granules formed by system/method of present disclosure and granules formed by conventional process, in accordance with an embodiment of the present disclosure.
Figure. 5 is graphical representation of granulation index of the granules formed by system/method of present disclosure and granules formed by conventional sintering process, in accordance with an embodiment of the present disclosure.

Figure. 6 is graphical representation of flame front speed in a sinter bed formed by granules of conventional sintering process and by system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 7 is graphical representation of tumbler index of the granules formed by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 8 is graphical representation of return fines and abrasion index of granules formed by conventional sintering process and by system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 9 is graphical representation of sinter bed shrinkage of the sinter bed, when formed by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 10a shows a scanning electron microscope image of granules formed by conventional sintering process.

Figures. 10b to 10f shows a scanning electron microscope images of granules formed by system/method of the present disclosure, in accordance to with an embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent system and method do not depart from the scope of the disclosure. The novel features which are believed to be characteristics of the disclosure, as to method of operation, together with further objects and advantages maybe better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof has been shown by way of example in the figures and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.

Embodiments of the present disclosure disclose a system and method of sintering iron ore that increases the productivity without compromising quality of sinter and to address the drawbacks as mentioned in the background. The system of the present disclosure includes a granulator drum, which may be configured to coat micro granules formed in the granulator drum. The coating aids in absorbing moisture from core of the micro granules and allow moisture to travel from core to the shell of the granules and, hence form a hard layer on the surface of the granules. Owing to presence of hard coating layer, the granulation index of the sinter mix may largely increase and hence, the coating may aid in improving the overall bed permeability.
In conventional sintering process, there would be deterioration of permeability of the sinter bed. Permeability of the sinter bed gets deteriorated because of transfer and accumulation of magnetic susceptible materials in the top portion of the sinter bed.

Accordingly, the system for sintering the iron ore is disclosed. The system includes a plurality of feeding stations, which may be arranged in series. Each of the plurality of feeding stations may be configured to proportionately feed raw materials into a granulator drum. The granulator drum may be configured to rotate at predetermined speed for mixing the raw materials. Simultaneously, water and lime fines may be sprayed into the granulator drum to form a wet granulated mixture. The granulator drum includes a cylindrical vessel, which is defined with an entry side and an exit side and configured to receive fines of raw materials through the entry side. The cylindrical vessel is rotatable for mixing and granulating the fines of raw materials. Further, the granulator drum includes a spraying unit stationarily disposed in the cylindrical vessel. The spraying unit configured to spray at least one of water and a binder, during rotation of the cylindrical vessel to convert the fines of raw material into micro granules of wet granulated mixture. Furthermore, the granulator drum includes a feeding unit stationarily disposed at the exit side of the cylindrical vessel. The feeding unit is configured to supply fines of dried material into the cylindrical vessel, such that the micro granules are coated with the fines of the dried material. The coating aids in absorbing moisture from core of the micro granules and allow moisture to travel from core to the shell of the granules and, hence form a hard layer on the surface of the granules. Owing to presence of hard coating layer, the granulation index of the sinter mix may be largely increased and hence, the coating may aid in improving the overall bed permeability.

Further, the system may include a hopper, which may be configured to receive the wet granulated mixture from the granulator drum. The hopper may be configured to feed the wet granulated mixture on a pallet car. Furthermore, the system may include at least one ignition furnace, which may be configured to generate a flame front in the sinter bed for sintering. Upon completion of sintering of the wet coated granulated mixture, the sinter strand may be tilted, and sinter cake falls on spike crusher and crushed sinter is transported to sinter cooler. Cooled sinter, thereafter, screened into three fractions, minus 5 mm which goes to granulation unit for recycling, plus 5 mm which goes to blast furnace stock house.

In the following detailed description, embodiments of the disclosure are explained with reference to accompanying figures that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

The following paragraphs describe the present disclosure with reference to Figures. 1 to 10f. In the figures, the same element or elements which have similar functions are indicated by the same reference signs.

Figure. 1 illustrates a schematic view of a system (100) for sintering iron ore, before the iron ore is fed into a blast furnace. The system (100) includes a plurality of feeding stations (102), which may be arranged in series. Each of the plurality of feeding stations (102) may be configured to proportionately feed raw materials into a granulator drum (103). In an embodiment, the raw materials may be iron ore fines, limestone fines and solid fuel [anthracite coal/coke fines], dolomite/pyroxenite fines and sinter return fines. The granulator drum (103) may be configured to rotate for mixing the raw materials. Simultaneously, water or binder such as lime fines may be sprayed into the granulator drum (103) to form a wet granulated mixture. Further, the system (100) includes a hearth feeding station (104) which may contain 10-20 or 10-25 mm sized sinter. A layer of this 10-20 mm or 10-25 mm sinter is spread on to a pallet car (106) to form a hearth layer (123). The height of this hearth layer (123) may vary between 40mm to 80 mm.

As apparent from Figure. 1, the granulator drum (103) may include a cylindrical vessel (125), which may be defined with an entry side (118) and an exit side (119), where the granulator drum (103) may be configured to receive fines of raw materials through the entry side (118). In an embodiment, the granulator drum (103) (thus, the cylindrical vessel (125)) may be configured to rotate at predetermined speed for mixing and granulating the fines of raw materials. As seen Figure. 1, the granulator drum (103) may include a spraying unit (113), which may be stationarily positioned in the cylindrical vessel (125). The spraying unit (113) may be configured to spray at least one of water and a binder into the cylindrical vessel (125), during rotation of the cylindrical vessel (125). In an embodiment, spraying one of water or binder may facilitate in converting the fines of the raw materials into micro granules of wet granulated mixture.
Further referring to Figure. 1, the granulator drum (103) may include a feeding unit (114), which may be stationarily disposed at the exit side (119) of the cylindrical vessel (125). In an embodiment, the feeding unit (114) may be disposed at 1/3rd length of the cylindrical vessel (125) towards the exit side (119). The feeding unit (114) may be configured to supply fines of dried material into the cylindrical vessel (125), for coating the micro granules. In an embodiment, the dried fine powder are calcined lime fines, calcined dolomite fines, limestones fines, olivine fines and bentonite fines. The dried fine powder may include particle size of about 45 micron for about 50% to 70% and remaining particle size being 74 micron. Further, the dried fine powder may posses water absorbing capacity of about 70 to 150.

In an embodiment, the feeding unit (114) may be pneumatic system, which may include a plurality of nozzles [not shown in figures], arranged in series. Each of the plurality of nozzles may include a nozzle size less than 90 micron and may be connected to a storage compartment, which may be configured to store fines of dried material. The plurality of nozzles may be configured to spray fines of dried material for a period of about 30 seconds to 60 seconds, into the cylindrical vessel (125) for coating the micro granules [as seen in Figure. 2a]. The dried fine powder may coat the micro granules as a result of centrifugal movement of the micro granules of the granulated mixture, which may occur due to rotation of the cylindrical vessel (125). In an embodiment, thickness of coating (110) of the dried fine powder on the surface of the micro granules may range from about 80 to 150 micron. The coated granules exiting from the granulator drum (103) are harder and includes higher mean particle size, which helps in improving sinter bed permeability.

In an embodiment, the fines of dried material coated on the micro granules aids in decreasing total moisture of green granules, thus improving drying efficiency unlike the uncoated granules [as shown in Figure. 2b]. That is, the coating (110) aids in absorbing moisture from core of the micro granules and allow moisture to travel from core to the shell of the granules and, hence form a hard layer on the surface of the granules. Owing to presence of hard coating layer (110), the granulation index of the sinter mix may largely increase and hence, the coating (110) may aid in improving the overall bed permeability.

Referring again to Figure. 1, the system (100) may include a hopper (105), which may be configured to receive the wet granulated mixture from the granulator drum (103). The hopper (105) may be configured to feed the wet granulated mixture on the pallet car (106). In an embodiment, the wet granulated mixture may be fed over the hearth layer (123) to form a sinter bed (109) of desired height, which may include a plurality of layers. As an example, the sinter bed (109) may be of a height (600-620mm) and top portion of the sinter bed (109) may be 1/3rd of the total bed height. In an embodiment, the system (100) may include a plurality of pallet cars (106) that may be movably disposed on a sinter strand (107). Each of the pallet car (106) may be disposed such that it may move along the sinter strand (107) in a forward direction. As apparent from Figure. 1, the system (100) may include at least one ignition furnace (108), which may be configured to generate a flame front in the sinter bed (109). In other words, the sinter bed (109) moving on the pallet car (106) may come under the at least one ignition furnace (108), where top portion of the sinter bed (109) gets ignited and flame front may be generated in the sinter bed (109).

In an embodiment, the system (100) may include a plurality of wind boxes (116) positioned below the sinter strand (107), which may be configured to create suction force. This suction force may cause the air to be extracted into the sinter bed (109), which may cause the flame front to travel through the sinter bed (109) from the top portion towards the bottom portion of the sinter bed (109). In an embodiment, the plurality of wind boxes (116) may be fluidly coupled to suction device through a manifold as shown in Figure. 1.

In an embodiment, upon completion of sintering of the wet granulated mixture (thus, the sinter bed (109)), sinter strand (107) may be tilted, and sinter cake falls on spike crusher (117) and crushed sinter is transported to sinter cooler. Cooled sinter, thereafter, screened into three fractions, minus 5 mm which goes to granulation unit (103) for recycling, plus 5 mm which goes to blast furnace stock house.

In an embodiment, coating the granules aids in generating a thin slag layer on surface of the micro granules at higher temperature and increases the diffusion rate during subsequent sintering
In an embodiment, during subsequent sintering the dried and wet core granules have larger impact on the cracking and bursting tendency. The dried layer on the surface of granules mitigates the granules from facing sudden thermal shock in the sintering process and, hence the granules may not burst during sintering process, thus maintaining the bed permeability and reduce the bed emissions.
The permeability of the middle and bottom layer depends on bed load on top layer. However, producing the compact bed in top layers do not necessarily reduce the air flow rate in middle and bottom layer of the sinter bed (109). The supply of air across the sinter bed (109) is now uniformly maintained. This results in reducing the flame front speed (FFS) on top layer of the sinter bed (109) and in similar way it matches FFS with the middle and bottom layers of the sinter bed (109).

Example:

Embodiments of the present disclosure will now be described with an example of particular compositions of raw materials used for coating (110). Experiments have been carried out with respect to conventional sintering process and sintering process of the present disclosure. The composition of raw materials used for coating is as shown in below table 1.
Raw Mixture Fe (t) Al2O3 SiO2 CaO MgO TiO2 MnO LOI
Calcined Lime fines 62.2 2.4 3.48 0.05 0.01 0.11 0.03 2.6
Calcined dolomite 1.2 1.45 4.8 67.34 23.45 0.08 0.06 3.14
Limestone 0.6 0.78 6.45 47.96 0.54 0.04 0 38.84
Bentonite 10.6 14.2 41.23 1.87 2.14 1.07 0.26 17.33
Olivine 5.33 0.61 37.19 4.41 36.03 0.18 0.01 2.11

Table 1
The sinter raw mix of 100 kg is mixed in the granulator drum (103) and moisture or binder is added to convert the fines into micro ball having mean particle size of 2.5mm. The material is mixed with moisture of about 6% to 7% and coating material is sprayed on the surface of the green granules. The coated granules are subjected to moisture analysis in order to investigate the actual effect of coating (110) on the final moisture content of the granules.
The sinter mix is then transferred to pot sinter. During the experiment, the initial suction rate and the ignition flame temperature for firing the sinter in sintering process is kept constant (1200 mm of water column) and at 11000 C, respectively.
The fired sinter is then removed from the pot and stabilized by dropping the whole mass of sinter for 4 times from 2-meter height. After dropping, minus 5 mm fraction of sinter fines is removed and weighed, and the remaining sinter is further screened in size (100) range -40 mm to +10 mm for tumbler test. The sinter is then tested microstructural analysis. During sintering process, the top temperature of sinter bed (109) has been measured to note the thermal behavior in top layer of the sinter bed (109).
Figure. 3a revels that the coated granules have better physical strength after coating as compared to normal green granules. The coated granules owing to better granulometry helps in better distribution across the sinter bed (109) and hence improve air flow efficiency and better control in flame front is observed that the granules of conventional sintering process [as seen in Figure. 3b].
Further, the sinter mixture has made with target chemistry i.e., the basicity (CaO/SiO2) of 2.5 and MgO at 2 %. The Coke rate in all set of trials was kept constant at 6 %. The bulk density of the sinter bed (109) of sinter in 600 mm pot maintained around 1.8 to 2 g/cc. However, in all the coated granules sinter trial tests, the bulk density increase to 2-2.3 gm/cc
The finesse of the coating material is kept below 80-micron (µm) size 100% passing with 45microm is more than 60%. This help in increasing the surface area of the powder and hence it adhere well on the mini granules of the sinter mixture.
Hereinafter, experimental results i.e., properties of the sinter bed (109) possessed as a result of the techniques of the present disclosure has been described. Figure. 4 shows a graphical representation of drop strength and green compressive strength (GCS) of the coated granules and granules formed by conventional sintering. The drop strength is a measure of granules from the height of 300 mm and the green compressive strength (GCS) is the measure of the material compressive strength under compression loading in universal tensile testing material. From Figure. 4 it is apparent that, the drop strength is found to be maximum in case of bentonite coat sinter, as bentonite is highly hygroscopic material and in similar manner to that of calcined lime fines. However, the material like limestone and olivine is having lower water absorbity and hence it is giving low drop strength and green compressive strength.

Now, Figure. 5 shows a graphical representation of granulation index (GI) of granulated mixture processed by conventional process and coated granulated mixture of the present invention. It is evident in Figure. 5 that, granulation index is largely increased in case of calcined lime fines and calcined dolomite as the presence of CaO will absorb the water from the core and tends to form dry and hard layer on the surface of the granules. Further, the coating (110) on micro granules not only increases the physical strength of the granules, but also helps in increasing the flame front speed by the virtue of the rate of moisture removal across the sinter bed (109) during sinter. Mainly the rate of water condensation is increased and the removal of moisture rate near the flame as compared to conventional sintering process, and the same is shown in below table 2.
Sinter Process Moisture across the sinter bed, %
Initial moisture A B C
Normal Sintering 6.3 4.505 5.35 5.92
Calcined Lime fines 6.45 4.01 4.34 4.68
Calcined dolomite 6.32 4.1 4.76 5.01
Limestone 6.54 4.1 4.76 5.01
Bentonite 6.38 4 4.3 4.7
olivine 6.43 5.3 5.7 6

Table 2

The rate of moisture removal is found to be more in calcined lime fines power coat granules and similar effect is observed in calcined dolomite case. However, the lower water absorbability of limestone and olivine has low rate of water condensation and removal. The water absorbability plays vital role in controlling the rate of moisture removal across the depth of the sinter bed (109).
As seen in Figure. 6, the FFS in top surface of the sinter bed is very high in case of normal sintering. The airway sintering helps in reducing the Flame front speed almost by 30%. Similarly, it may be noted that, the coated green granules used for making sinter helps in increasing the tumbler index of sinter to 2-4 points [as seen in Figure. 7]. The presence of the coated granules on the surface generate the low melting point slag on the surface of the granules as compared to the conventional sintering.
The retention of sinter at higher temperature for more than 5-6 minutes as explain before allowing the formation of SFCA/SFCA-I and primary hematite phase which is beneficial for increasing the tumbler strength of the iron ore sinter and so the abrasion index of sinter also gets improved.
When the flame front travel beneath the sinter bed the top layer of sinter experiences the maximum amount of thermal shock. The temperature of top layer is drop in higher magnitude compare to middle and bottom layer. Hence the top layer of sinter is fragile owing to results in sinter fine, this is more crucial as per the yield of sinter plant is considered. The partial pressure of oxygen is also high at top portion and hence the coke burns at faster rate in top layer as compare to middle and bottom layer. The excess available oxygen in top layer results in conversion of hot form wustite into hematite, and so the top layer is so porous and fragile. Around 20-30% of the total sinter bed is unusable owing to its fragile nature and hence it is always reported as return sinter fines (-5mm).

In the present work the percentage of return fines of sinter is largely reduced to 5-6% (as seen in Figure. 8]and hence it helps in increasing the productivity, and the bed shrinkage of sinter in proposed sintering process /system (100) is found to be max of 27 mm (as seen in Figure. 9).
Figure. 10a illustrates a scanning electron microscope images of sinter granules formed by conventional sintering process and Figures. 10b to 10f illustrates a scanning electron microscope images of coated sinter granules of the present disclosure. From the Figures. 10 b to 10f, it can be clearly that the in elemental analysis the normal sinter granules and coated sinter granules shown a major difference in the content at the surface and in the core of the sinter granules. The granules after sinter at temperature above 1000 OC -1350 OC results in diffusion of CaO, MgO, Al2O3 and SiO2, which results in formation of calcium ferrite and calcium silicate which are beneficial to form complex silico ferrite of calcium and aluminium phase in final sinter. However, in case of bentonite coated granules, the content of alumina and silica increases. The olivine coated granules contain more Mgo. It is observed that the thickness of the coated granules layer depends on the coated material used. Based on this the quantity of the material the coating thickness is shown in table 3.
Sinter Case Coating thickness (Micron)
Normal Sintering 0
Calcined Lime fines coated 150
Calcined dolomite coated 135
Limestone coated 100
Bentonite Coated 400
Olivine Coated 80

Table 3
Equivalents:

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.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral numerals:

Feature Numeral
System 100
Feeding stations 102
Granulator drum 103
Hearth feeding station 104
Hopper 105
Pallet car 106
Strand 107
Ignition furnace 108
Sinter bed 109
Coating 110
Spraying unit 113
Feeding unit 114
Wind boxes 116
Crusher 117
Entry side 118
Exit side 119
Hearth layer 123