Claims:We Claim:

1. A hood assembly (118) for covering a sinter bed (109) in an iron-ore sintering system (100), the hood assembly (118) comprising:
a plate (119) supported by at least one support member (120), wherein the plate (119) is defined with a plurality of through apertures (121) and is configured to extend along at least a portion of a length and a width of the sinter bed (109);
wherein, the plurality of through apertures (121) are configured to control suction force in the sinter bed (109), thereby creating airway resistance across the sinter bed (109).

2. The hood assembly (118) as claimed in claim 1, wherein diameter of each of the plurality of through apertures (121) ranges from about 5 mm to 8 mm.

3. The hood assembly (118) as claimed in claim 1, wherein each of the plurality of through apertures (121) are defined at a distance ranging from about 3 mm to 5 mm.

4. The hood assembly (118) as claimed in claim 1, wherein length of the hood assembly (118) substantially corresponds to length of the sinter bed (109) and width is about 1.2 to 1.4 times of width of the sinter bed (109).

5. The hood assembly (118) as claimed in clam 1, wherein the hood assembly (118) comprises a seal (122) made with a heat resistance material.

6. A method of sintering iron ore, the method comprising:
feeding, raw materials into a mixing and granulation unit (103) by a plurality of feeding stations (102) arranged in series, to form a wet granulated mixture;
feeding, the wet granulated mixture on to pallet cars movably disposed on a sintering strand (107) by a feeding hopper (105), to form a sinter bed (109) having a plurality of wet granulated mixture layers;
generating, a flame front in each of the plurality of wet granulated mixture layers, by at least one ignition furnace (108);
positioning a hood assembly (118) on the sinter bed (109), enclosing the sinter bed (109); and
applying suction through the plurality of layers of the wet granulated mixture; wherein the hood assembly (118) is configured to control suction force to create airway resistance, thereby causing slow movement of the flame front in each of the plurality of wet granulated mixture layers for sintering each of the plurality of wet granulated mixture layers.

7. The method as claimed in claim 6, comprising feeding sintered material to form a hearth layer (123) at bottom of each of the pallet cars by a hearth feeding station (104).

8. The method as claimed in claim 7, wherein height of the hearth layer (123) ranges from 10 mm to 25 mm.

9. The method as claimed in claim 6, wherein height of the sinter bed (109) ranges from 550 mm-600 mm.

10. The method as claimed in claim 6, 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.

11. The method as claimed in claim 6, wherein the hood assembly (118) decreases air velocity magnitude to a range of 1.8 to 2.2 m/sec.

12. The method as claimed in claim 6, wherein the airway resistance results in pressure drop across the sinter bed (109) with uniform distribution of air across the width of the sinter bed (109).

13. The method as claimed in claim 6, comprises feeding the sintered iron-ore into a crusher (117) and crushed sintered iron-ore into a sinter cooler.

14. A system (100) for sintering iron-ore, the system (100) comprising:
a plurality of feeding stations (102) arranged in series;
a mixing and granulation unit (103), configured to receive raw material from each of the plurality of feeding stations (102), wherein the mixing and granulation unit (103) is configured to form a wet granulated mixture;
a hopper (105), configured to feed the wet granulated mixture from the mixing and granulation unit (103) on to pallet cars 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);
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; and
a hood assembly (118) positioned to enclose the sinter bed (109), wherein the hood assembly (118) is configured to control suction force to create airway resistance thereby causing slow movement of the flame front in each of the plurality of wet granulated mixture layers for sintering each of the plurality of wet granulated mixture layers.

15. The system (100) as claimed in claim 14, comprising a hearth feeding station (104) to feed sintered material from a hearth layer (123) at bottom of each of the pallet cars.

16. The system (100) as claimed in claim 14, wherein the hood assembly (118) comprises:
a plate (119) supported by at least one support member (120), wherein the plate (119) is defined with a plurality of through apertures (121) and is configured to extend along at least a portion of a length and a width of the sinter bed (109);
wherein, the plurality of through apertures (121) are configured to control suction force in the sinter bed (109), thereby creating airway resistance across the sinter bed (109).

17. The system (100) as claimed in claim 16, wherein each of the plurality of through apertures (121) include a diameter ranging from about 5mm to 8mm.

18. The system (100) as claimed in claim 16, wherein each of the plurality of through apertures (121) are positioned at a distance ranging from about 3mm to 5mm.

19. The system (100) as claimed in claim 16, wherein length of the hood assembly (118) substantially corresponds to length of the sinter bed (109) and width is about 1.2 to 1.4 times of width of the sinter bed (109).

20. The system (100) as claimed in claim 16, wherein the hood assembly (118) comprises a seal (122) made with a heat resistance material.

Dated this 25th day of March 2021

Signature:
Name: NIKHIL S R
To: Of K&S Partners, Bangalore
The Controller of Patents Agent for the Applicant
The Patent Office, at Kolkata
, Description: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 hood assembly for covering a sinter bed in the iron ore sintering system.

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 via melt formation at the particle interface of different constituents of the mixture. These large sized agglomerates are then crushed and sized as per requirement of the blast furnace.

Generally, Dwight Lloyd sintering machine is used for iron ore sintering. Initially, a blended raw material is prepared by mixing fluxes such as limestone and quartz, fuel such as coke breeze and water are added to fine iron ore and mixed with each other and granulated. Above blended raw material is charged onto sintering pallets and raw mixture bed is formed. The sintering pallets are successively moved in the horizontal direction, and a surface of the raw mixture bed is ignited in an ignition furnace. After that, air is sucked from a lower portion of the sintering bed such that, fuel such as coke breeze contained in the blended raw material is burned. The burning zone is gradually shifted from top portion of the raw mixture bed to bottom portion, and the iron ore is sintered.

Often in conventional sintering process, there would be a heat deficiency at top portion of sinter bed. Such heat deficiency may be caused due to insufficient presence of fuel materials at the top portion causes generation of weak sinter fines leading to reduction in ‘yield’ of sinter production. The heat pattern in the sintering bed of a conventional sintering machine is nonuniform in the vertical direction of the bed, and there is a general tendency that the maximum temperature reached in the bed increases with increasing depth and that the temperature-fall speed slows down accordingly.

During sintering process, the top portion of the sintering material layer will often have lower bulk temperature because of shorter of time for exposure to elevated temperature than the intermediate and lower portions. This leaves the problem that a sintered ore formed in the top portion is low in melt bonding, thus have less mechanical strength, resulting in reduced sintering yield. Further, when the flame front travel beneath the sinter bed, the top portion of the sinter bed experiences maximum amount of thermal shock. Hence, the top portion of sinter bed is fragile owing to results in sinter fine, and yield in the top portion of the bed is less, because of wustite (FeO) deficient as compared to the middle and the bottom potion of the sinter bed. Furthermore, partial pressure of oxygen is also high at the top portion and, hence the coke burns at faster rate in top portion as compared to the middle and the bottom portions. The excess available oxygen in top portion results in conversion of wustite into hematite making the top portion 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).

With advancement, different techniques have been emerged and some of these known techniques are described herein.

One of the process, namely a hybrid pelletized sinter (HPS) process, in which production of both sinter and pellets are incorporated, to enable the use of large amounts of finer iron ores, includ¬ing pellet feed with high iron content. In contrast to the conventional sintering process, the blended ore, limestone, and burned lime are first mixed and pelletized in the HPS pro¬cess using disk pelletizers to produce green pellets. The green pellets are then coated with coke breeze in a coating mixer before charging onto the sinter machine. Sinter pot tests have confirmed the benefits of the preferential addition of coke onto the surface of the green pellets and the superior properties of the final agglomerates, which are produced by HPS process.
Another process, namely a mosaic embedding iron ore (MEBIOS) process is a multiple sintering process that arranges dense pre-granu¬lated pellets (called the aging bed), that do not easily deform during the sintering, in an ordinary sinter mixture (called the induction bed). In the MEBIOS process, a pisolitic ore, which includes coarse particles has been used for the induction bed and a Marra Mamba-type ore, which includes many fine particles used for the aging bed. The aim of the MEBIOS process is formation of a ventilation route in the sintering bed by creating a low-density area around the large pellets and suppression of sinter bed shrinkage due to support of the load by the dense large pellets in the upper part of the sinter bed. Small dry particles charged into the packed sinter bed are found to have a similar effect on controlling the bed structure due to friction between the dry and wet particles.

One of the patent publication i.e., Japanese Patent Publication No. 61-223136 discloses a technique for reducing density of a sintering material layer to be formed on a pallet, 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, sintering material is segregated with fine particles held in an upper layer and with coarse particles held in intermediate and lower layers, in order to make the upper layer highly permeable to air with eventual improvement of yield and productivity of a sintered ore. However, this technique pose a problem that, since the 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 as originally desired.

In another patent publication CN102032790 (A), a supporting plate clean chute segregation distributor and segregation distributing device for segregating wet granulated raw material and increasing productivity has been disclosed. Though, such method improves the permeability, but shall not avoid formation of fragile layer at the top of the sinter bed, thus affecting the yield.

In yet another patent publication US 6349833 B1, discloses a method of magnetic loading of a sintering material. 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. Further, a method for increasing yield of sintering ore by utilizing siderite has been disclosed in patent publication CN103834799A, wherein sized siderite ore is used as hearth layer and roasted siderite has been added to sinter production for calculating overall sinter yield.

Furthermore, in one of Japanese patent publication 61-243131 discloses a hood positioned on the upper surface of sintered ore on the endless pallets, and air is forcibly fed into the hood so that the pressure in a wind box under the endless pallets is made negative. In this way, the cost can be decreased." However, an object of the above Japanese patent publication is to decrease a total electric power of the forced fan and the ventilating fan, and no explanations has been made for enhancing the productivity by increasing a moving speed of the combustion and melting zone on the raw mixture bed. According to the sintering machine of the conventional method, in order to maintain a pressure, drop between the upper portion and the lower portion of the raw mixture bed, air pressure necessary for the sintering process is maintained at a constant rate, and pressure of the forced draft fan and that of the ventilating fan are balanced with each other. On the other hand, according to the above patent publication, air at the room temperature is supplied into the apparatus, so that the total electric power can be decreased. However, the sintering speed of the combustion and melting zone on the raw mixture bed is not positively increased for the purpose of enhancing the productivity.

The above-mentioned prior arts involves the transfer of magnetic susceptible material present in sinter mix to travel in such a way that it gets a accumulated in the top bed of the sinter by virtue magnetically operated sophisticated chutes or hoppers.
Such methods demand for 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 accumulate in sinter top portion. Further, extra segregation of such material at the top portion, results in more assimilation, more melt generation, which deteriorates permeability of the bed. The extra segregation also tends to affect the overall segregation of coke and magnetic material across the sinter bed. As top portion gets richer in magnetic material, the middle portion get deficient in wustite rich material, thus disturbing the overall material balance of the sinter bed.
The present disclosure is intended to overcome one or more limitations stated above or other relevant limitations associated with the conventional arts.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional techniques are overcome by system (i.e., hood assembly) and 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 hood assembly for covering a sinter bed in an iron-ore sintering system, is disclosed. The hood assembly includes a plate supported by at least one support member. The plate is defined with a plurality of through apertures and is configured to extend along at least a portion of a length and a width of the sinter bed. The plurality of through apertures are configured to control suction force in the sinter bed, thereby creating airway resistance across the sinter bed.

In an embodiment of the disclosure, diameter of each of the plurality of through apertures ranges from about 5 mm to 8 mm and each of the plurality of through apertures are defined at a distance ranging from about 3 mm to 5 mm from each other.

In an embodiment of the disclosure, length of the hood assembly substantially corresponds to length of the sinter bed and width is about 1.2 to 1.4 times of width of the sinter bed.

In an embodiment of the disclosure, the hood assembly is sealed with a heat resistance material.

In another non-limiting embodiment of the disclosure, a method of sintering iron ore is disclosed. The method includes feeding raw materials into a mixing and granulation unit by a plurality of feeding stations arranged in series, to form a wet granulated mixture. The method further includes feeding the 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 wet granulated mixture layers. Further the method includes generating a flame front in each of the plurality of wet granulated mixture layers, by at least one ignition furnace and positioning a hood assembly on the sinter bed, enclosing the sinter bed. Furthermore, the method includes applying suction through the plurality of layers of the wet granulated mixture through the hood assembly. The hood assembly is configured to control suction force to create airway resistance, thereby causing slow movement of the flame front in each of the plurality of wet granulated mixture layers for sintering each of the plurality of wet granulated mixture layers.

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

In an embodiment of the disclosure, height of the hearth layer ranges from 10 mm to 25 mm.

In an embodiment of the disclosure, height of the sinter bed ranges from 550 mm-600 mm.

In an embodiment of the disclosure, 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.

In an embodiment of the present disclosure, wherein the hood assembly decreases air velocity magnitude to a range of 1.8 to 2.2 m/sec.

In an embodiment of the disclosure, the airway resistance results in pressure drop across the sinter bed with uniform distribution of air across the width of the sinter bed.

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

In yet another non-limiting embodiment of the 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 mixing and granulation unit, which is configured to receive raw material from each of the plurality of feeding stations. The mixing and granulation unit is configured to form a wet granulated mixture. Furthermore, the system includes a hopper, configured to feed the wet granulated mixture from the mixing and granulation unit 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 and a hood assembly positioned to enclose the sinter bed. The hood assembly is configured to control suction force to create airway resistance thereby causing slow movement of the flame front in each of the plurality of wet granulated mixture layers for sintering 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.

Figure. 2 is a schematic representation of a hood assembly of the system of Figure. 1, enclosing the sinter bed, in accordance with an embodiment of the present disclosure.

Figures. 3a and 3b illustrates schematic representation of sinter bed depicting air flow pattern through hood assembly of the present disclosure and conventional sintering process, respectively in accordance with an embodiment of the present disclosure.

Figures. 4a and 4b illustrates schematic view of sinter bed, formed by system/process of the present disclosure and conventional sintering process, respectively in accordance with an embodiment of the present disclosure.

Figures. 5a to 5c illustrates step-by-step process of sintering the iron ore, in accordance with an embodiment of the present disclosure.

Figure. 6a to 6c are graphical representation of temperature distribution during sintering process, when performed by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 7 is graphical representation of flame front speed during sintering process, when performed 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 tumbler index of sinter formed by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.
Figure. 9 is graphical representation of abrasion index of sinter formed by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 10 is graphical representation of sinter return fines of sinter formed by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 11 is graphical representation of sintering time, when sintered by conventional process and by the system/method of the present disclosure, in accordance with an embodiment of the present disclosure.

Figure. 12 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.

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 characteristic 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 hood assembly, which may enclose a portion of the sinter bed to control suction force in order to create airway resistance, thereby causing slow movement of a flame front in each of a plurality of wet granulated mixture layers in the sinter bed.
Often in conventional sintering process, the top portion of the sintering material layer would have lower bulk temperature, because of shorter in the length of time for exposure to elevated temperature, than the intermediate and bottom portions. This leaves the problem that a sintered ore formed in the top portion is low in melt bonding, thus less mechanical strength, resulting in reduced sintering yield. Further, when the flame front travels beneath the sinter bed, the top portion of the sinter bed experiences maximum amount of thermal shock. Hence, the top portion of sinter bed is fragile owing to less yield, because of wustite (FeO) deficient in the top portion as compared to the middle and the bottom potion of the sinter bed. Around 20% to 30% of the total sinter bed is unusable owing to its fragile nature.

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 mixing and granulation unit. The mixing and granulation unit may be configured to rotate for mixing the raw materials. Simultaneously, water and lime fines may be sprayed into the mixing and granulation unit to form a wet granulated mixture. Further, the system may include a hopper, which may be configured to receive the wet granulated mixture from the mixing and granulation unit. 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. Additionally, the system may include a hood assembly, which may be positioned next to the ignition furnace and may be configured to enclose the ignited sinter bed.

The hood assembly may include a plate, which may be supported by at least one support member. The plate may be defined with a plurality of through apertures. The hood assembly [thus, the plurality of through apertures] aids in reducing total suction pressure across the sinter bed, thereby reducing temperature gradient across the sinter bed. Further, the hood assembly may aid in increasing heating index and reduce thermal shock to the top portion of the sinter bed. Additionally, the hood assembly decreases air velocity magnitude to a range of 1.8 to 2.2 m/sec, which aids in uniform distribution of air across the bed, which leads to effective sinter bed burning throughout width of the sinter bed and hence increases yield of the sinter.

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 12. 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 mixing and granulation unit (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 mixing and granulation unit (103) may be configured to rotate for mixing the raw materials. Simultaneously, water or binder such as lime fines may be sprayed into the mixing and granulation unit (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 40-80 mm.

Referring further to Figure. 1, the system (100) may include a hopper (105), which may be configured to receive the wet granulated mixture from the mixing and granulation unit (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 (110) 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 (110) of the sinter bed (109) gets ignited and flame front may be generated in the sinter bed (109). Additionally, the system (100) may include a hood assembly (118), which may be positioned next to the ignition furnace (108) and may be configured to enclose the ignited 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 through the hood assembly (118) into the sinter bed (109), which may cause the flame front to travel through the sinter bed (109) from the top portion (110) towards the bottom portion (112) 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.

Turning now to Figure. 2, which illustrates a schematic view of a hood assembly (118), which may be configured to enclose the sinter bed (109), post ignition of the sinter bed (109) by the at least one ignition furnace (108). The hood assembly (118) may include a plate (119), which may be supported by at least one support member (120). The hood assembly (118) may extend along a length and width of the sinter bed (109) to enclose the sinter bed (109). In an embodiment, height of the at least one support member (120) may be slightly higher than the height of the sinter bed (109) to be enclosed and width of the plate (119) may be configured to be about 1.2 to 1.4 times greater than width of the sinter bed (109). As apparent from Figure. 2, the plate (119) may be defined with a plurality of apertures (121). In an embodiment, each of the plurality of apertures (121) may be through apertures (121). Each of the plurality of apertures (121) are configured to include a diameter ranging from about 5mm to 8mm and may be spaced to each other at a distance ranging from 3mm to 5mm. In an embodiment, the hood assembly (118) may be refractory coated or metallic coated. Further, the hood assembly (118) may include a seal (122) from the bottom, which may be made of heat resistant material, to mitigate extra air being sucked from sides of the hood assembly (118).

In an embodiment, configuration of the hood assembly (118) aids in reducing total sucking pressure across the sinter bed (109), thereby reducing temperature gradient across the sinter bed (109). Further, the hood assembly (118) may aid in increasing heating index and reduce thermal shock to the top portion (110) of the sinter bed (109). Additionally, the hood assembly (118) decreases air velocity magnitude to a range of 1.8 to 2.2 m/sec, which aids in uniform distribution of air across the sinter bed (109), which leads to effective sinter bed (109) burning throughout width of the sinter bed (109), which is evident from Figure. 3a. Figure. 3a depicts resistance in air flow lines (A), due to positioning of the hood assembly (118) over the sinter bed (109). As seen in Figure. 3a, resistance in flow of air, results in reducing the overall suction pressure across the sinter bed (109). The resistance in flow of air also results in developing a uniform flow pattern line in the top portion (110) of the sinter bed (109). The channeling effect [as seen in Figure. 3b, which depicts air flow lines (A) in conventional process] is negated under such resistance flow of air. Owing to drop in pressure, which is inversely proportional to the air flow rate, results in better interaction of air across the sinter bed (109) mainly the highest resistance area. This helps in uniform distribution of air across the sinter bed (109) and lower pressure results in more compact sinter on the top portion (110) of the sinter bed (109), as flame front speed in the top portion (110) of the sinter bed (109) is reduced, which may be equal to flame front speed in the middle portion (111) and the bottom portion (112) of the sinter bed (109).

Referring to Figure. 4a, which illustrates a schematic view of the sinter bed (109), which is sintered by enclosing with the hood assembly (118) of the present disclosure. As apparent from Figure. 4a, the higher kinetic of assimilation on top portion (110) of the sinter bed (109) make the top portion (110) denser. When the sinter bed (109) travels out from the ignition furnace (108), the top portion (110) get benefits of lower thermal shocks owing to low pressure (low suction pressure) and also restrict the sinter bed (109) from being exposed to the atmosphere. The top portion (110) may remain at higher temperature as compared to conventional sintering process, resulting in higher assimilation at given temperature, similar to that of the middle portion (111) and the bottom portion (112). This may help to achieve dense metallurgical structure having better physical strength. Further, as the top portion (110) bed remain at higher temperature throughout the process of sintering, owing to which more air gets preheated when it gets entrapped from top portion (110) to the middle portion (111) and the bottom portion (112) of the sinter bed (109), thus improving kinetics at the middle portion (111) and the bottom portion (112) of the sinter bed (109), unlike the sinter bed which is formed by conventional process [as seen in Figure. 4b], in which the top portion (110) is so porous and fragile.

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, efficiency of the sintering may further be improved by a provision of supplying hot recirculated air back to the hood assembly (118). The temperature of the hot air may be around 180-220ºC. The resistance to the hot air passing through the hood assembly (118) increases thermal efficiency of the sintering process and aids in widening the sinter flame width. This tempo of hot recirculated air along with the resistance in flow produce beneficial dense sinter at the top portion (110), without increase in sintering time.

Example:

Embodiments of the present disclosure will now be described with an example of particular compositions of raw materials. Experiments have been carried out for a specific composition of raw materials, subjected to conventional sintering process and sintering process of the present disclosure. The composition of the sinter for which the tests are carried out is as shown in below table 1.
Sinter Chemistry (%)
Serial number Fe(T) CaO MgO SiO2 Al2O3 Basicity
1 54.77 12.55 2.02 4.98 2.54 2.52
2 54.32 12.8 2.01 5.02 2.41 2.55
3 54.41 12.6 2.02 5.04 2.51 2.50

Table 1
A sinter raw mix of 100 kg is mixed in the mixing and granulation unit (103) and moisture has been added to convert the fines into micro balls having mean particle size of 2. 5mm. The material is mixed with moisture of about 6% to 7%. The wet granulated mixture is then transferred to sinter pot in form of a sinter bed. During experiment, the initial suction rate and the ignition flame temperature for firing the sinter bed (109) in sintering process has been kept constant (1200 mm of water column) and at 1100 °C, respectively. As seen in Figure. 5a the sinter bed (109) is ignited by ignition furnace (108) through LPG. Once the ignition has been completed the hood assembly (118) may be placed such that, the hood assembly (118) encloses the sinter bed (109) [as seen in Figure. 5b].

In an embodiment and as seen in Figure. 5a, a plurality of thermocouples may be embedded in sinter pot at different height of the sinter pot. As an example, a first thermocouple (113) may be positioned between 1mm to 183 mm from the top portion (110) of the sinter bed (109), a second thermocouple (114) may be positioned between 2 mm to 367 mm from the top portion (110) of the sinter bed (109) and a third thermocouple (115) may be positioned between 3 mm to 550 mm from the top portion (110) of the sinter bed (109). Once the temperature of a first thermocouple (113) reaches the maximum value and then decreases, the second thermocouple (114) starts increasing the temperature and the hood has to be removed from the pot. Increase in temperature reading of the second thermocouple (114) is an indication that the top portion (110) is completed firing and the flame has now reached to the middle portion (111). After this as seen in Figure. 5c, the hood assembly (118) is removed and the remaining sintering process is allowed to complete, which is indicated by a fourth thermocouple (124), which is termed as burn out through point (BTP) in the art. The sinter so produced in the pot is dense and well assimilated, that is the reason the sinter in the bed may not be able to remove easily as it gets shrink and assimilated more.

Hereinafter, experimental results (i.e., properties of the sinter bed (109) possessed as a result of the techniques of the present disclosure and conventional process) has been described. Figures. 6a to 6c shows the time temperature curves of the conventional sintering and sintering using method and system of preset disclosure, respectively. It is apparent from the Figure. 6a, that in conventional sintering the area covered by the first thermocouple (113) denoted as (T1) covers lesser area, which is an indication that the sinter bed (109) cooled at faster rate in top portion (110), as compared to bottom portion (112) and the middle portion (111). Moment of flame front and heat front disturb the equilibrium while travelling the flame from top portion (110) to the bottom portion (112) of the sinter bed (109). Similarly, the retention time of sinter at top portion (110) around 180-200 mm against total of 600 mm top portion (110) at high temperature is very low. Whereas the middle portion (111) and the bottom portion (112) are exposed to high temperatures compared to top portion (110). This is confirmed by the temperature distribution shown by the thermocouple embedded in the sinter bed (109). The area under the temperature distribution curve reviles that the top portion (110) of sinter bed (109) covers the lesser area as compared to the middle portion (111) and the bottom portion (112) of the sinter bed (109). This makes the top portion (110) approx. 200 mm weaker as compared to the middle portion (111) and the bottom portion (112). Further, heavy suction inside the sinter bed (109) does not allow the top portion (110) to retain higher temperature at the range of 1200 °C to 1250 °C. However, the hot gases which decent downs to the middle portion (111) and the bottom portion (112) from the top portion (110) give sufficient heat to the both the portions.

Now, Figures. 6b and 6c show improvement in term of temperature in the top portion (110) of the sinter bed (109). The nature of graph for the first thermocouple (113) is totally changed. The sinter senses higher temperature in the top portion (110) and retains there for longer times as compared to conventional sintering process. Once the flame front is broader as compared to normal sintering process, the area under the temperature distribution graph across the sinter bed (109) is more, which means that the top portion (110) sinter will remain at higher temperature for longer period of time. The sinter in top portion (110) faces more temperature, which facilitates in generating beneficial sinter phases, which helps in reducing thermal shocks. Owing to higher temperature of the top portion (110) of the sinter bed (109), the gases that comes in contact with remaining two portions gets higher temperature, which do not exceed 1290 ºC to 1310 ºC and thus resulting in formation of more silicoferrite of calcium and aluminum-1.
Further, from table 3 and table 4, it may be noted that, the system (100) and method of the present disclosure yields better temperature distribution in top portion (110) of the sinter bed (109). It is also clear that, in the conventional sintering process, the top portion (110) of the sinter bed (109) has not attained the demanded sintering temperature and hence generate poor quality sinter in the top portion (110) as compared to sinter in the middle portion (111) and bottom portion (112).
% Area Above 1200 ºC
Process Bed thermocouple1 Bed thermocouple 2 Bed thermocouple 3
Conventional process Did not reach temperature 14.56 30.22
Present process 17.33 18.56 32.11
Present process with hot recirculated air 19.05 19 33.42

Table 3

Time above 1200 ºC, minutes
Process T1 T2 T3 Total time
Conventional process Did not reach temperature 3 5 8
Present process 3 4 6 13
Present process with hot recirculated air 4 4 7 15

Table 4
As seen in Figure. 7, the flame front speed (FFS) in top portion (110) of the sinter bed (109) is very high in conventional process. However, in the process of the present disclosure, the flame front speed is reduced almost by 30% and even bit lower if hot air is recirculated through the hood assembly (118).
Further, it may be noted from Figure. 8 that, from the sintering process /system (100) of the present disclosure, the tumbler index of the sinter has been increased to 2-3 points. The resistance in air flow in the sintering system (100)/process of the present disclosure helps in maintaining the flame front temperature and speed and, the flame front covers the entire section of sinter bed (109) smoothly at lower time. Similarly, as seen in Figure. 9, abrasion index of sinter has been improved from the sintering process/method of the present disclosure.
As described in the above paragraphs, when the flame front travel beneath the sinter bed (109) the top portion (110) of the sinter bed (109) experiences maximum amount of thermal shock. The temperature of top portion (110) drops in higher magnitude when compared to the middle portion (111) and the bottom portion (112). Hence the top portion of sinter bed (109) is fragile. The partial pressure of oxygen is also high at top portion (110) and hence the coke burns at faster rate in top portion (110) as compared to the middle portion (111) and bottom portion (112). The excess available oxygen in top portion (110) results in conversion of hot wustite into hematite, and so the top portion (110) is so porous and fragile. Around 20-30% of the total sinter bed (109) is unusable owing to its fragile nature and hence it is always reported as return sinter fines (-5mm).
However, sinter formed by the sintering process /method of the present disclosure, it may be noticed from Figure. 10, that the percentage of return fines of sinter is largely reduced to 5-6% and hence it helps in increasing the productivity.
Further, as described in the above paragraphs, in the sintering process /method of the present disclosure, the flame front speed will increase horizontally as well as vertically, owing to which the time of sintering also get reduced to the larger extent. The time of sintering in conventional process is 22 minutes while that for sintering process /system (100) of the present disclosure decreases to 21 minutes, as shown in Figure. 11.
Additionally, owing to higher rate of assimilation in top portion (110) due to the presence of retention of top portion (110) of sinter bed (109) at temperature more than 1200 ºC for more time, results the bed to shrink more as compared to conventional sintering process. The bed shrinkage of sinter in proposed sintering process /system (100) is found to be 23 mm and even better if hot air also circulated along the hood assembly (118) [as seen in Figure. 12].
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 (108) 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 (108) 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
Mixing and granulation unit 103
Hearth feeding station 104
Hopper 105
Pallet car 106
Strand 107
Ignition furnace 108
Sinter bed 109
Top portion 110
Middle portion 111
Bottom portion 112
First thermocouple 113
Second thermocouple 114
Third thermocouple 115
Wind boxes 116
Crusher 117
Hood assembly 118
Plate 119
Support member 120
Apertures 121
Seal 122
Hearth layer 123
Fourth thermocouple 124