Claims:WE CLAIM:

1) A process of producing a wet iron ore pellet, comprising:
preparing a wet mixture of a pellet feed in a mixer;
applying compressive shear force by means of a differential speed roller press on the pellet feed, to obtain a flattened wet mixture;
crushing the flattened wet mixture to top size range of 0.6mm-1.5mm; and
feeding the flattened wet mixture, to a pelletizer for producing the wet iron ore pellet.

2) The process as claimed in claim 1, wherein the pellet feeds are of hematite or magnetite or goethite or sinter return fines.

3) The process as claimed in claim 1, wherein the flattened wet mixture size is -1.0 mm.

4) The process as claimed in claim 1, wherein ratio of speed of one roll with other of the differential speed roller press is 0.7 – 0.9.

5) The process as claimed in claim 4, wherein ratio of speed of the one roll with other of a differential speed roller press is 0.9.

6) The process as claimed in claim 1, wherein pressure applied by the differential speed roller press is 180-200 MPa.

7) The process as claimed in claim 1, wherein the composition of the pellet feed is hematite ore, limestone, olivine, coal and bentonite is 90-98, 2-7, 1-7, 0.5-2.5 and 0.3-1% (all in wt. %) respectively.

8) The process as claimed in claim 7, wherein Green Crushing Strength of the wet iron ore pellets is 2-3.5 kg/pellet.

9) The process as claimed in claim 7, wherein drop strength of the wet iron ore pellets is 10-16 points.

10) The process as claimed in claim 7, wherein dry crushing strength of the wet iron ore pellet is 5-7.5 kg/pellet.

11) The process as claimed in claim 7, wherein cold crushing strength of the wet iron ore pellets is 320-335 Kg/pellet.

12) The process as claimed in claim 7, wherein porosity of the wet iron ore pellets is 28-28.30%.

13) The process as claimed in claim 1, wherein the composition of the wet mixture is magnetite ore 95-98%, preferably 97.5%, limestone 1-3%, preferably 2%, bentonite 0.3-4%, preferably 0.5%.
14) The process as claimed in claim 13, wherein Green Crushing Strength of the wet iron ore is 1.5-2.2 Kg/pellet.

15) The process as claimed in claim 13, wherein drop strength of the wet iron ore pellets is 2.5-3.7 points.

16) The process as claimed in claim 13, wherein dry crushing strength of the wet iron ore pellets is 3-4 kg/pellet.

17) The process as claimed in claim 13, wherein cold crushing strength of the wet iron ore pellets is 230-250 Kg/pellet.

18) The process as claimed in claim 13, wherein porosity of the wet iron ore pellets is 18-19%.

19) The process as claimed in claim 1, wherein the composition of the pellet feed is goethite ore 92-98%, preferably 96%, limestone 1-3%, preferably 2%, coal 1-3%, preferably 1.5%, bentonite 0.3-4%, preferably 0.5%.

20) The process as claimed in claim 19, wherein Green Crushing Strength of the wet iron ore pellets is 3-4 Kg/pellet.

21) The process as claimed in claim 19, wherein drop strength of the wet iron ore pellets is 30-60 points.

22) The process as claimed in claim 19, wherein dry crushing strength of the wet iron ore pellets is 7-9.5 kg/pellet.

23) The process as claimed in claim 19, wherein cold crushing strength of the wet iron ore pellets is 210-225 Kg/pellet.

24) The process as claimed in claim 19, wherein porosity of the wet iron ore pellets is 26-26.30%.

25) The process as claimed in claim 1, wherein the composition of the pellet feed is sinter return fines 95-99.7%, preferably 99.5%, bentonite 0.3-5%, preferably 0.5%.

26) The process as claimed in claim 25, wherein Green Crushing Strength of the wet iron ore pellets is 2-2.8 Kg/pellet.

27) The process as claimed in claim 25, wherein drop strength of the wet iron ore pellets is 2.3-2.8 points.

28) The process as claimed in claim 25, wherein dry crushing strength of the wet iron ore pellets is 2-3 kg/pellet.

29) The process as claimed in claim 25, wherein cold crushing strength of the wet iron ore pellets is 200-215 Kg/pellet.

30) The process as claimed in claim 25, wherein porosity of the wet iron ore pellets is 21-23%.

31) An arrangement (200) of preparing iron ore pellet, the arrangement comprising:
a mixer (2.2) being configured to prepare a wet mixture (2.3a) from a pellet feed;
a differential speed roller press (2.3) being configured to apply compressive shear force to the wet mixture to obtain a flattened wet mixture (2.3b);
a crushing means (2.4) being configured to the size the flattened wet mixture (2.3b) to top size range size of 0.6mm-1.5mm;
a pelletizer (2.5) being configured to be fed with the flattened wet mixture (2.3b) to produce the wet iron ore pellet; and
a furnace (2.5) configured to receive the wet iron ore pellet (2.5b) to be fired.

32) The arrangement as claimed in claim 31, wherein the ratio of speed of one roll with other of the differential speed roller press (2.3) is 0.7 – 0.9.

33) The arrangement as claimed in claim 32, wherein ratio of speed of the one roll with other of a differential speed roller press (2.3) is 0.9.

34) The arrangement as claimed in claim 31, wherein pressure applied by the differential speed roller press (2.3) is 180-200 MPa.
The arrangement as claimed in claim 31, wherein the pelletizer is disc or drum.

35) The arrangement as claimed in claim 31, wherein the pelletizer is disc or drum.

Dated 11th day of February 2020

Gopinath Arenur Shankararaj
IN/PA 1852
OF K&S PARTNERS
AGENT FOR THE APPLICANT
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of the subject matter:
METHOD OF PRODUCING A WET IRON ORE PELLETS

Name and address of the Applicant:
TATA STEEL LIMITED, Jamshedpur, Jharkhand, India 831001
Nationality: INDIAN

The following specification describes the subject matter and the manner in which it is to be performed.
TECHNICAL FIELD
The present invention relates to a pellet industry.
BACKGROUND
Iron ore pellet making is an agglomeration process in which powdered iron ore, fluxes (olivine, limestone, pyroxenite, dolomite etc.), binder (bentonite, organic binder), Anthracite coal or Coke Fines (as solid reducing agent) and water is added to form wet pellet or ball which is later on dried and subsequently fired at 1250- 1300°C to get the required strength acceptable in iron making furnaces such as Blast Furnace, Corex, DRI, Midrex, etc.
Due to generation of fines during mechanized mining it is necessary to agglomerates iron ore fines for easy handling which also act as a feed in blast furnace. Iron ore pellets provide good permeability in Blast furnace because of its uniform shape and size as well as adjusted chemistry.
Physical properties of wet and dried Pellets plays a major role during iron ore pelletizing process whereas fired pellets properties are important for handling and transportation and iron making furnaces.
Importance of different physical properties are described below.
Wet ball properties: Once the wet pellets are made, they are discharged from disc/drum pelletizer on the roller screen and then on different conveyor belts so that it can be transferred to induration unit (travelling grate or rotary kiln) for firing. During this process, the wet iron ore pellet undergoes impact force due to a number of drops from certain height (which varies from plant to plant) it experience during conveying operation from balling equipment to induration unit. It also experience compressive load by bed of pellet burden itself. During transfer from disc pelletizer to induration unit, through conveyor belts, wet pellets should not break therefore, these pellets should have sufficient drop strength. Additionally, when these wet pellets are charged in pellet car they should have sufficient crushing strength to resist the compressive load by wet pellet bed. Any major deformation or even slight breakage in wet pellet will affect the permeability across the pellet bed during induration process.
Dry ball properties: Due to removal of moisture from wet pellets after drying, crushing strength of pellet increases slightly but at the same time there is no plasticity in the pellets to absorb any shock due to movement of machine or compressive loading from pellet bed. At this step of pellet preparation, it is most vulnerable to crack because there is no moisture to provide strength through bridging and plasticity to absorb any shock. Due to release of the surface moisture and onset of release of combine moisture pellets have tendency to break. Lower crushing strength of dried pellet can also lead to breakage/fines generation due to compressive loading from pellet bed. To minimize or avoid this, dry pellet should have higher crushing strength
Fired pellet properties: It measures the ability of pellet to withstand the compressive loading during handling and transportation as well as during use in iron making furnaces (blast furnace, midrex, DRI furnaces). Lower crushing strength will lead to pellet breakage and fines generation in furnace which leads to lower permeability and hence, lower productivity in furnace.
Prior Arts:
A significant amount work has been reported to improve the above described physical properties. These are described below:
Ni Rongfu et al., in their Patent No. CN101215632A reported the use of an iron ore pellet binder, whose composition in percentage by weight is sodium bentonite 20-70%, boron-containing mineral tailings 30-79%. With this binder they shows the increase in cold compressive strength and high temperature metallurgical properties.
But the drawback associated with this is that addition of higher sodium in pellet making, increases sodium content of blast furnace burden which is not good for blast furnace operation. Sodium is responsible for scaffold formation, hanging and slipping in furnace, deterioration of furnace refractory lining, increase in coke consumption in blast furnace. Also, addition of boron containing material will lead to increase in boron content in final steel product which is not suitable for various grade of steel.
Liu Guitang et al., in their Patent No. CN102337395A prepared pellet additive by using raw materials namely cellulose ether, iron powder, starch ether and sodium bentonite. These material are prepared in particular manner to obtain the pellet additive which improve the physical and metallurgical properties and also the quality and yield of finished pellet.
Drawback associated with this method is first the raw material are costly (cellulose ether, iron powder, starch ether, etc.) additionally the processing of these material makes the final product further expensive due to which total pellet production cost will increase.
Schieroh et al., in their Patent No. US3765869 described how to use organic binder (low temperature binders) by reducing slag forming binders. According to this invention, the raw material used by him was mainly iron ore, starch/dextrin and iron powder (produced after grinding or milling of sponge iron product). Due to the chemical reaction between iron oxide of the ore, iron powder and the carbon produced, due to pyrolytic decomposition of organic binder, pellet developed greater strength after firing.
The above mentioned prior art shows that physical properties of pellet can be increased by adding MgO based material, organic binder and iron powder. The use of these additives increases the cost of pellets considerably, and even slag amount increases.
Another drawback of using organic binder is that it increases the dust generation in induration.
This dust travel from one zone to another along with process gas/air and creates difficulty in operation.
OBJECTS
An object of the invention is to provide a method and system to improve Green Crushing Strength of the wet iron ore pellets.
Another object of the invention is to provide a method and system to improve drop strength of the wet iron ore pellets
Still another object of the invention is to provide a method and system to improve dry crushing strength of the wet iron ore pellet
Still another object of the invention is to provide a method and system to improve cold crushing strength of the wet iron ore pellet
Still another object of the invention is to provide a method and system to improve porosity of the wet iron ore pellet.
The present disclosure is directed to overcome one or more limitations stated above or any other limitation associated with the prior arts.
Disclosure of the Invention
The present invention provides a method of producing a wet iron ore pellet, comprising preparing a wet mixture of a pellet feed in a mixer, applying compressive shear force by means of a differential speed roller press on the pellet feed, to obtain a flattened wet mixture, crushing the flattened wet mixture to top size range of 0.6mm-1.5mm and feeding the flattened wet mixture, to a pelletizer for producing the wet iron ore pellet.
In another embodiment an arrangement for preparing iron ore pellet is described. The arrangement comprises a mixer to prepare a wet mixture from a pellet feed, a differential speed roller press to apply compressive shear force to the wet mixture to obtain a flattened wet mixture, a crushing means being configured to the size the flattened wet mixture to top size range size of 0.6mm-1.5mm, a pelletizer being configured to be fed with the flattened wet mixture to produce the wet iron ore pellet and a furnace configured to receive the wet iron ore pellet to be fired.
For a better understanding of the invention and to show how the same may be performed, a preferred embodiment thereof may will now be described, by way of non-limiting example only, with reference to accompanying drawings.
Brief description of the drawings
FIG. 1 shows a conventional schematic of iron ore pellet making.
FIG. 2 shows a system for making iron ore pellet in accordance with an embodiment of the invention.
FIG. 3 shows a process for making iron ore making pellet in accordance with an embodiment of the invention.
FIG. 4 shows an XRD analysis of (a) hematite (b) bentonite as per experiment 1.
FIG. 5 shows (a) Drop no, (b) Wet crushing strength, (c) Dry crushing strength, (d) Cold crushing strength and (e) Porosity of wet iron ore as per experiment 1.
FIG. 6 shows swelling test of bentonite (a) without applying shear and compressive force (b) with shear and compressive force for 20 min (c) shear and compressive force for 30 min as per experiment 1.
FIG. 7 shows an Elemental mapping of dried pellet (a) original microstructure (b) without applying shear and compressive force (c) after applying shear and compressive force as per experiment 1.
FIG. 8 XRD analysis of (a) Magnetite (b) Bentonite as per experiment 2.
FIG. 9 shows a) Drop no, (b) Wet crushing strength, (c) Dry crushing strength, (d) Cold crushing strength and (e) Porosity as per experiment 2.
FIG. 10 shows XRD analysis of (a) Goethite (b) Bentonite as per experiment 3.
FIG. 11 shows a) Drop no, (b) Wet crushing strength, (c) Dry crushing strength, (d) Cold crushing strength and (e) Porosity as per experiment 3.
FIG. 12 shows XRD analysis of (a) Sinter Return Fines (b) Bentonite as per experiment 4.
FIG. 13 shows a) Drop no, (b) Wet crushing strength, (c) Dry crushing strength, (d) Cold crushing strength and (e) Porosity as per experiment 4.
Description of the preferred embodiments
Shown in Fig. 1 is a schematic for conventional iron ore pellet making. Various bins are shown as ore fines bin (1.1a), flux bin (1.1b), solid reducing agent bin (1.1c) and bentonite bin (1.1d). The bins are the one for carrying various raw materials or pellet feed in desired proportion to be used in making of pellets. The bins are the set up used in a pellet making plant having standard shape and size.
The iron ore fines bin (1.1 a) is configured to carry iron ore fines. These fines can be the one from hematite or magnetite or goethite or sinter return fines or any iron bearing ore. The fluxes in flux bin (1.1b) can be limestone, olivine, dolomite, pyroxenite or their combination etc. in an appropriate proportion. The solid reducing agent in the solid reducing agent bin (1.1c) can be coal/coke powder etc. Collectively iron ore fines, flux, solid reducing agent and bentonite are called here as a pellet feed.
The pellet feed from the bins are fed into a mixer (1.2).
The mixer (1.2) is configured to uniformly mix the pellet feed with water (6-9%) to prepare a wet mixture. The wet mixture is fed to a pelletizer (1.3). The pelletizer is inclined and can be a drum or disc based. The pelletizer (1.3) comprises a motor (1.3a) to rotate it for necessary operation. The pelletizer is configured to prepare a wet iron ore pellets (1.3b). These wet iron ore pellets have a size of 6-16mm size.
These wet iron ore pellets are fed into an induration furnace (1.5) via a conveyor belt (1.4) and fired at suitable temperature.
Shown in Fig. 2 is an arrangement (200) for making pellets in accordance with an embodiment of the present invention.
Shown are the similar bins as depicted in Fig. 1. Iron ore fines bin (2.1a), flux bin (2.1b), solid reducing agent bin (2.1c) and bentonite bin (2.1d) with similar function as described in Fig.1.
The pellet feed or raw material from the bins can be of hematite or magnetite or goethite or sinter return fines.
Similarly, a mixer (2.2) is configured to uniformly mix the pellet feed from the bins (in desired proportion) with water (6-9%) to prepare the wet mixture (2.3a).
In an embodiment the mixer (1.2) can be muller mixer.
Shown is a differential speed roller press (2.3). The press (2.3) is configured to receive the wet mixture (2.3a) and apply compressive shear force to obtain a flattened wet mixture (2.3b). The two roll of the press (2.3) move in opposite direction in order to apply the shear and compressive forces on each and every particles of the wet mixture.
In an embodiment, the ratio of speed of one roll with other of the differential speed roller press is 0.7 – 0.9. In an embodiment the ratio is 0.9.
The pressure applied by the differential speed roller press is 180-200 MPa.
In an embodiment the differential speed roller press (2.3) can be roller crusher, or concentric ring ribbon mixer.
The flattened wet mixture (2.3b) so obtained is fed into a crushing means (2.4) (such as breaker/cutter/ mechanical vibrating screen) for bringing its size to 0.6-1.5mm (2.4a). It is to be appreciated that the size of 0.6mm-1.5mm as a prerequisite for the pelletizer (2.5).
The flattened wet mixture (2.3b) is further fed into the pelletizer (2.5) to produce the wet iron ore pellet. After the production of wet iron ore pellet, it is passed through different size roller screen so that, right size pellet (say 9-12mm) can be charged into the induration furnace (2.7) (via conveyor belt (2.6)) and, the oversized and undersized pellets are made again to meet this size.
In an embodiment the screening device can be crusher/shredder/ mechanical vibrating screen.
Fig. 3 shows a process (300) with series of steps to make the wet iron ore pellet. At step 304, the wet mixture is prepared of the pellet feeds in the mixer (2.2). At step (308) compressive shear force is applied by means of a differential speed roller press (2.3) on the pellet feed (2.3a), to obtain the flattened wet mixture (2.3b). The flattened wet mixture (2.3b) is crushed to a top size of 0.6mm-1.5mm as per step 312. The flattened and screened wet mixture is fed into the disc/drum pelletizer (2.5) to make the wet iron ore pellet as per as per step 316.
The method (300) and system (200) when applied, results in increase in physical properties of wet, dried and fired pellets, by forming improved bonding between particles of pellets due to increase in swelling property of bentonite and uniform distribution of silica (due to which silicate bond improve).
The embodiments of the invention are directed in making of wet iron ore pellets, by applying compressive shear force which results in increase in physical properties such as: wet pellet crushing strength, drop strength, dry strength and cold crushing strength of fired pellets.
The obtained wet iron ore pellets gives much higher compressive strength to pellets as compared with conventional route.
The embodiments described here relates to development of a method wherein shear and compressive forces are applied on wet mixture of pellet feed (containing bentonite).
As per the conventional process of making iron ore pellet as shown in Fig. 1, raw material is mixed simply by rubbing action, which cause interaction between roller and particles of raw materials, particles and wall of mixer rather than between particles-particles. While in the accordance with an embodiment of the invention, the compressive shear force applied on wet mix help each particle to mix properly with other constituent of raw material, and as bentonite is a montmorillonite material which means it has a octahedral sheet sandwiched between two tetrahedral sheets. So, when shear force act on wet mix particles, the bentonite particles experience structural transformation due to which its surface area increases and it shows better bonding with other particles and hence the wet ball strength, dry ball strength and fired pellet strength increases.
Hence, the method developed is to enhance the physical properties of wet, dried and fired pellets.
In accordance with an embodiment of the invention, for the composition of the pellet feed hematite ore 90-98%, preferably 92.67, olivine 1-7%, preferably 3.16% limestone 2-7%, preferably 2.27, coal 0.5-2.5%, preferably 1.41,bentonite 0.3-1%, preferably 0.5%.
Green Crushing Strength of the wet iron ore pellets is 2-3.5 Kg/pellet.
Drop strength of the wet iron ore pellets 10-16 nos/pellet.
Dry crushing strength of the wet iron ore pellets 5-7.5 kg/pellet.
Cold crushing strength of the wet iron ore pellets 320-335 Kg/pellet.
Porosity of the wet iron ore pellets is 28-28.30%.
In another embodiment, for the composition of the wet mixture being magnetite ore 95-98%, preferably 97.5%, limestone 1-3%, preferably 2%, bentonite 0.3-4%, preferably 0.5%.
Green Crushing Strength of the wet iron ore pellets is 1.5-2.2 Kg/pellet.
Drop strength of the wet iron ore pellets is 2.5-3.7 nos/pellet.
Dry crushing strength of the wet iron ore pellets is 3-4 kg/pellet.
Cold crushing strength of the wet iron ore pellets is 230-250 Kg/pellet.
Porosity of the wet iron ore pellets is 18-19%.
In yet another embodiment, for the composition of the pellet feed is goethite ore 92-98%, preferably 96%, limestone 1-3%, preferably 2%, coal 1-3%, preferably 1.5%, bentonite 0.3-4%, preferably 0.5%.
Green Crushing Strength of the wet iron ore pellets is 3-4 Kg/pellet.
Drop strength of the wet iron ore pellets is 30-60 nos/pellet.
Dry crushing strength of the wet iron ore pellets is 7-9.5 kg/pellet.
Cold crushing strength of the wet iron ore pellets is 210-225 Kg/pellet.
Porosity of the wet iron ore pellets is 26-26.30%.
In still yet embodiment, for the composition of the pellet feed being sinter return fines 95-99.7%, preferably 99.5%, bentonite 0.3-5%, preferably 0.5%.
Green Crushing Strength of the wet iron ore pellets is 2-2.8 Kg/pellet.
Drop strength of the wet iron ore pellets is 2.3-2.8 nos/pellet.
Dry crushing strength of the wet iron ore pellets is 2-3 kg/pellet.
Cold crushing strength of the wet iron ore pellets is 200-215 Kg/pellet.
Porosity of the wet iron ore pellets is 21-23%.
To establish this fact experimental analysis is discussed below.
Experimental Analysis:
Four experiments were conducted with various chemical compositions. Particle size distribution of raw materials used for the Exp. 1, 2, 3 and 4 are shown in Table 1, 2, 3 and 4 respectively.
The chemical compositions and obtained properties are defined below in Table 6. Also the similar processes were followed as per Process 300. For all the experiments the flattened wet mixture was sized to -1mm. The differential speed roller press is 0.9 and pressure applied by the differential speed roller press is 180-200 MPa.

Table 1 Table 2
Size range (µm) Ground Ore Concentrate Bentonite
+150 28.63 7.87
74-150 15.62 16.37
63-74 2.9 6.03
45-63 6.06 17.7
-45 46.79 52.03
Size range (µm) Magnetite Ore Limestone Bentonite
+150 0.24 19.0 7.87
74-150 2.45 5 16.37
63-74 3.59 2.9 6.03
45-63 14.55 1.9 17.7
-45 79.17 71.2 52.03

Table 3 Table 4
Size range (µm) Goethite Ore Limestone Bentonite Coal Size range (µm) Sinter return fines Bentonite
+150 10.1 19.0 7.87 17 +150 45.79 7.87
74-150 24.43 5 16.37 9.5 74-150 21.97 16.37
63-74 6.01 2.9 6.03 7.2 63-74 3.86 6.03
45-63 11.84 1.9 17.7 6.3 45-63 7.51 17.7
-45 47.62 71.2 52.03 60 -45 20.87 52.03

Raw material mix for GOC for the Exp. 1 is shown in Table 5.
Table 5
Raw material mix Weight (%)
Noamundi ore (Hematite) 92.67
Olivine 3.16
Limestone 2.27
Bentonite 0.50
Coal 1.41

Table 6
Chemical Composition Wet Pellet Properties Fired Pellet Properties (CCS in Kg/pellet Porosity (in%)
GOC/Bentonite (all in wt%) Conventional New Conventional New Conventional New
Exp. 1 (Hematite) Fe(T)- 60.27/10.15
FeO- 0.77/-
CaO- 0.45/1.85
MgO- 1.68/2.23
SiO2- 4.84/42.05
Al2O3- 2.52/2.23
TiO2- 0.11/1.22
Na2O- 0.05/1.94
C- 0.87/-
LOI- 3.63/20.12 GCS-1.44 Kg/pellet GCS-2.36 kg/pellet 291 327.32 28.86 28.19
DS-4.1 DS-14.8
DCS-3.25 kg/pellet DCS-6.99 kg/pellet
Magnetite/limestone/Bentonite (all in wt%) Before After Before After Before After
Exp.2 (Magnetite) Fe(T)- 66.25/0.1/10.15
FeO- 24.64/0/-
CaO- 0.32/49.42/1.85
SiO2- 5.21/1.9/42.05
MgO- 0.36/4.33/2.23
Al2O3- 0.15/0.25/14.72
TiO2- -/0.01/1.22
Na2O- -/0.11/1.94
LOI- -/43.17/20.12 GCS-1.26 Kg/pellet GCS-1.9 kg/pellet 177 242 19.76 18.54
DS-1.85 DS-3.1
DCS-1.31 kg/pellet DCS-3.26 kg/pellet
Goethite/limestone/Bentonite/Coal (all in wt%) Before After Before After Before After
Exp.3 (Goethite) Fe(T)- 66.25/0.1/10.15
FeO- 0.90/0/-/0
CaO- 0.001/49.42/1.85/0.82
SiO2- 3.36/1.9/42.05/11.5
MgO- 0.04/4.33/2.23/0.32
Al2O3- 2.27/0.25/14.72/5.05
TiO2- 0.006/0.01/1.22/0.28
Na2O- 0.04/0.11/1.94/-
C- 0.11/-/-/72.12
LOI- 6.08/43.17/20.12/77.65 GCS-2.14 Kg/pellet GCS-3.24 kg/pellet 196 215.34 27.01 26.18
DS-15.55 DS-47.65
DCS-4.17 pellet DCS-8.7 kg/pellet
SRF/Bentonite (all in wt%) Before After Before After Before After
Exp.4 (Sinter return fines) Fe(T)- 53.62/10.15
CaO- 11.65/1.85
SiO2- 5.43/42.05
MgO- 2.07/2.23
Al2O3- 2.92/14.72
TiO2- 0.07/1.22
Na2O- 0.04/1.94
C- 0.58/-
LOI- 0.54/20.12 GCS-1.05 Kg/pellet GCS- 2.33 kg/pellet 186 210 26.59 21.69
DS-2.05 DS-2.56
DCS-1.04 kg/pellet DCS-2.56 kg/pellet
Exp. 1:
Two process are being used to make wet pellets. One is the conventional route (as shown in FIG 1), and another route is as per the FIGS. 2 and 3 which apply shear and compressive forces on the wet mixture of pellet before sending it to disc/drum pelletizer. Wet pellets were prepared by using raw materials like iron ore fines, flux (limestone, olivine, pyroxenite, dolomite etc), solid reducing agent (coke fines, anthracite coal, GCP sludge etc) and bentonite. After mixing raw material, moisture is added (6-9%). The wet mixture then used to make wet pellets in disc pelletizer and later wet pellets get fired at temperature 1300°C in muffle furnace.
XRD analysis of raw material (Hematite and Bentonite) is shown in FIG. 4. The difference between properties of conventional and claimed process have been shown in FIG. 5a -5e depicting differences in properties such as Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength and Porosity. Evidently, Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength have increased and Porosity has been reduced.
FIG. 6 shows swelling test of bentonite (a) without applying shear and compressive force (b) with shear and compressive force for 20 min (c) shear and compressive force for 30 min.
Swelling test was performed on bentonite before and after applying shear and compressive force.
Swelling index of normal bentonite was 22 ml/2g, after applying shear compressive force for 20 and 30 minutes continuously it reached to 37ml/2g and 40ml/2g respectively. As the bentonite property depend on its swelling property, higher the swelling property better the bentonite property. Bentonite being montmorillonite consist of three layered structure of a central octahedral alumina (Al2O3) layer, and two tetrahedral silica (SiO2) layers while absorbing water, this layer tends to expand and the electrostatic interaction between platelets tends to decrease due to which bentonite able to spread over a larger area improving the binding efficiency. The rational is applicable for all the four experiments Exp. 1-Exp 4.

Elemental mapping is shown in FIG. 7a-7c depicting after applying shear and compressive force, silica distribution increases showing better dispersal of homogenised oxides in comparison to pellets made through conventional route. This is because due to shear and compressive forces the oxides particles spread evenly over other constituents of pellets thereof improving the bonding (silicate bonding) between different constituents of pellets. The rational is applicable for all the four experiments.
Exp-2
As per the experiment 1 similar experiment has been conducted for Exp. 2.
XRD analysis of raw material Magnetite and Bentonite is shown in FIG. 8.
The difference between properties of conventional and inventive process have been shown in FIG. 9a -9e depicting differences in properties such as Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength and Porosity. Evidently, Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength have increased and Porosity has been reduced.
Exp-3
As per the experiment 1 similar experiment has been conducted for Exp. 3.
XRD analysis of raw material Goethite and Bentonite is shown in FIG. 10.
The difference between properties of conventional and inventive process have been shown in FIG. 11a -11e depicting differences in properties such as Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength and Porosity. Evidently, Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength have increased and Porosity has been reduced.
Exp-4
As per the experiment 1 similar experiment has been conducted for Exp. 4.
XRD analysis of raw material Sinter returns and Bentonite is shown in FIG. 12.
The difference between properties of conventional and inventive process have been shown in FIG. 13a -13e depicting differences in properties such as Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength and Porosity. Evidently, Green Compressive Strength, Compressive Strength, Dry Strength, Dry Compressive Strength, Cold Compressive Strength have increased and Porosity has been reduced.
Advantages
Embodiments of the invention have shown improvement in Green Crushing Strength of the wet iron ore pellets.
Embodiments of the invention have shown improvement in drop strength of the wet iron ore pellets.
Embodiments of the invention have shown improvement in dry crushing strength of the wet iron ore pellet.
Embodiments of the invention have shown improvement in cold crushing strength of the wet iron ore pellet.
Embodiments of the invention have shown reduction in porosity of the wet iron ore pellet.
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.