Claims:We Claim:
1. A binder comprising cold rolling mill oxide (CRM oxide/dust), humic acid and lime.

2. The binder as claimed in claim 1, wherein the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of about 75-85 wt%, humic acid at a concentration of about 10-15 wt% and lime at a concentration of about 5-10 wt%.

3. The binder as claimed in claim 2, wherein the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of about 80 wt%, humic acid at a concentration of about 13 wt% and lime at a concentration of about 7 wt%.

4. The binder as claimed in claim 1, wherein the cold rolling mill oxide (CRM oxide/dust) is obtained from pickling line as red oxide.

5. The binder as claimed in claim 1, wherein the humic acid is alkali based humic acid.

6. The binder as claimed in claim 5, wherein the alkali based humic acid is sodium based or potassium based.

7. A method for synthesizing the binder as claimed in claim 1, comprising steps of:
 mixing cold rolling mill oxide (CRM oxide/dust), humic acid and lime dissolved in water; and
 ageing the mixture to obtain the binder.

8. The method as claimed in claim 7, wherein the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of 75-85 wt%,, humic acid at a concentration of 10-15 wt% and lime at a concentration of 5-10 wt%.

9. The binder as claimed in claim 8, wherein the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of about 80 wt%, humic acid at a concentration of about 13 wt% and lime at a concentration of about 7 wt%.

10. The method as claimed in claim 7, wherein the cold rolling mill oxide (CRM oxide/dust) is generated by spray roasting of acid pickling liquor in cold rolling mill of steel plant.
11. The method as claimed in claim 7, wherein the humic acid is alkali based humic acid.

12. The method as claimed in claim 11, wherein the alkali based humic acid is sodium based or potassium based.

13. The method as claimed in claim 7, wherein the ageing is carried out for about 2 to 8 days.

14. The method as claimed in claim 13, wherein the ageing is carried out for about 5 days.

15. A method for improving thermal shock properties of iron ore pellets comprising steps of:
 mixing of iron ore fines, flux, carbon source, bentonite, and the binder as claimed in claim 1 along with moisture; and
 pelletizing the mixture to obtain the iron ore pellets with improved thermal shock properties.

16. The method as claimed in claim 15, wherein the iron ore fines are hematite-based iron ore fines.

17. The method as claimed in claim 15, wherein the flux is selected from a group comprising CaO based flux, MgO based flux and combinations thereof.

18. The method as claimed in claim 17, wherein the CaO based flux is selected from a group comprising limestone, slaked lime, calcined limestone and combinations thereof.

19. The method as claimed in claim 17, wherein the MgO based flux is selected from a group comprising olivine, pyroxenite, dolomite and combinations thereof.

20. The method as claimed in claim 15, wherein the carbon source is selected from a group comprising anthracite coal, coke fines and combinations thereof.

21. The method as claimed in claim 15, wherein the method involves dry mixing of iron ore fines, flux, carbon source, bentonite and the binder followed by wet mixing with addition of moisture.
22. The method as claimed in claim 15, wherein the pelletization is carried out in disc pelletizer to obtain green pellets followed by induration in a furnace at a temperature ranging from about 1200°C - 1300°C to obtain the iron ore pellets.

23. The method as claimed in claim 15, wherein the iron ore pellets of size ranging from 10 mm to 12.5 mm is obtained.

24. The method as claimed in claim 15, wherein the binder partially replaces bentonite in pelletization.

25. The method as claimed in claim 24, wherein the binder replaces bentonite in pelletization at a replacement ratio of 1:1.

26. The method as claimed in claim 15, wherein the iron ore pellets show better thermal shock properties as compared to the iron ore pellets with bentonite binder alone.

27. Use of the binder of any of the claims 1-6 in preparation of iron ore pellets.

28. Iron ore pellets obtained by the method of any of the claims 15-26.
, Description:TECHNICAL FIELD
The present disclosure relates to the field of material sciences and metallurgy. In particular, the present disclosure relates to a binder for improving thermal shock properties of iron ore pellets. The binder comprises cold rolling mill oxide (CRM oxide/dust), humic acid and lime. Also, disclosed are corresponding method for synthesizing the binder and a method for improving thermal shock properties of iron ore pellets using the binder.

BACKGROUND AND PRIOR ART
Iron ore pelletization involves the process of making spherical ball of size 9-16 mm diameter by rolling raw materials like mixture of iron ore fines, fluxes (such as limestone, dolomite, dunite, olivine, pyroxenite, etc.), carbon source (such as anthracite, coke breeze, etc.) together with the binder such as bentonite and moisture. The prepared wet balls are then indurated in travelling grate/rotary grate kiln furnace at 1300°C, so that they can be used as a feed material for iron making units.
One of the major problems with respect to iron ore pellets is its tendency to have lower thermal shock properties. Thermal shock properties can be described as tendency of green/wet pellets to resist internal pressure due to sudden evaporation of moisture during drying. Therefore, green/wet pellets should be dried slowly to avoid sudden release of moisture which results in bursting/spalling. But, this would take longer time and requires excessive amount of heat which is not economically feasible.
Various materials have been used to improve thermal shock properties of iron ore pellets. Conventionally, bentonite is most commonly used, because it provides acceptable green, dried and fired strength along with thermal shock properties. Green strength is necessary to endure the load caused due to two kinds of forces i.e., impact force and compressive force (a) impact force act while dropping through several conveyors on the way from disc pelletizer to induration furnace and (b) compressive force act due to load of wet pellet bed inside the furnace. Dry strength is required when there is no plasticity in the pellet to protect it from cracking during induration. Fired strength is crucial for transportation of fired pellets to iron making unit.
However, bentonite usage contributes to high alumina, silica and undesirable constituents to final pellet chemistry which is not desirable. Also, it reduces total iron content of pellets and is expensive due to its limited availability.
Several prior arts teach to improve thermal shock properties of iron ore pellets as discussed below:
Haiyong et al., in their Patent No. CN104988308A used iron mud and carboxymethyl cellulose to replace bentonite and achieve better burst temperature and green strength. But, iron mud contains high percentage of moisture approximately 25% of which must be lowered down to 5% so that it can be acceptable for pellet making. This process of drying adds cost to finished pellets. Also, iron mud scan pose a significant environmental hazard and storage problem due to its alkaline nature. Moreover, iron mud contains detrimental compound such as alumina and silica.
Guitang et al., in their Patent No. CN102329951A mentioned the use of iron powder and organic binder such as cellulose ether to achieve better drop strength, burst temperature and fired strength. As bentonite contributes high alumina and silica to final pellet chemistry, organic binder is used as an alternative since it burns out at its oxidizing temperature completely and does not contribute any alumina/silica to final pellet. However, the drawback associated with its use is lower fired pellet strength properties since it leaves behind the pores after burning out, which results in lower strength. Moreover, this patent is silent on green crushing strength and dry crushing strength. Also, cellulose ether is costly and adds extra cost of production for pellet making.
Chaoyang et al., in their Patent No. CN101921911A stated the use of pellet binder which comprises iron tailing, an activator (sodium carbonate, sodium silicate and sodium hydroxide) and bentonite. 46-65% iron containing tailings are dried and dehydrated to 3-10% moisture content and then an activator and bentonite is added and mixed, and later carried to pulveriser to ground finely to size of 100-300 mesh. Pellet produced using pellet binder showed improvement in burst temperature and, physical properties achieved was comparable to bentonite-based pellet. However, addition of iron tailing increases alumina and silica in pellets and detrimental compounds such as sulphur and phosphorus. Moreover, activator also increases alkali in the pellets.
Ward et al., in their Patent No. US3425823A synthesizes the ammonium alkali metal humate salts by using raw materials like, alkali metal hydroxide or ammonium with humate salts. This binder was used along with bentonite to improve thermal shock properties of iron ore pellet while maintaining the strength of the pellets. However, the drawback associated with it is that alkali content of the final pellets will significantly increase due to excess addition of sodium humate and alkali metal as claimed in the art.
Thus, there exists a need for binder/method for improving thermal shock properties of iron ore pellets and the present disclosure achieves the same.

SUMMARY OF THE DISCLOSURE
The present disclosure relates to a binder which enables integrating reduction in bentonite consumption, better thermal shock property and cost effectiveness in pellet making.

In an embodiment of the present disclosure, the binder comprises cold rolling mill oxide (CRM oxide/dust), humic acid and lime.

In another embodiment of the present disclosure, the binder is a red oxide based binder. The cold rolling mill oxide (CRM oxide/dust) in the binder is obtained from pickling line as red oxide.
The present disclosure also relates to a method for synthesizing the binder, comprising steps of:
 mixing cold rolling mill oxide (CRM oxide/dust), humic acid and lime dissolved in water; and
 ageing the mixture to obtain the binder.

The present disclosure also relates to a method for improving thermal shock properties of iron ore pellets comprising steps of:
 mixing of iron ore fines, flux, carbon source, bentonite and the binder along with moisture; and
 pelletizing the mixture to obtain the iron ore pellets with improved thermal shock properties.
The present disclosure also relates to use of the binder in preparation of iron ore pellets.
The present disclosure also relates to Iron ore pellets obtained by the above method.
In an embodiment of the present disclosure, the binder partially replaces bentonite in pelletization.

In another embodiment of the present disclosure, the iron ore pellets so obtained show better thermal shock properties as compared to the iron ore pellets with bentonite binder alone.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the disclosure may be readily understood and put into practical effect,
reference will now be made to exemplary embodiments as illustrated with reference to
the accompanying figures. The figures together with detailed description below, are
incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the
present disclosure where:

Figure 1: Illustrates drop strength of green pellets; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (bentonite based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

Figure 2: Illustrates green crushing strength of green pellets; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (base case - bentonite-based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

Figure 3: Illustrates dry crushing strength of dried pellets; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (base case - bentonite-based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

Figure 4: Illustrates relative change in un-cracked pellets with base case as 100%; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (base case - bentonite-based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

Figure 5: Illustrates relative change in cracked pellets with base case as 100%; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (base case - bentonite-based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

Figure 6: Illustrates relative change in burst pellets with base case as 100%; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (base case - bentonite-based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

Figure 7: Illustrates cold crushing strength of pellets at 1300°C; Set 1- pellets prepared using 99.5% GOC and 0.5% bentonite (base case - bentonite-based pellets); Set 2- pellets prepared using 99.5% GOC, 0.4% bentonite and 0.1% red oxide binder (red oxide based pellets); Set 3- pellets prepared using 99.5% GOC and 0.4% bentonite (bentonite based pellets)

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 product/methods do not depart from the scope of the disclosure.

Definitions:
Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

As used herein, the singular forms ‘a’, ‘an’ and ‘the’ include both singular and plural referents unless the context clearly dictates otherwise.

The term ‘comprising’, ‘comprises’ or ‘comprised of’ as used herein are synonymous with ‘including’, ‘includes’, ‘containing’ or ‘contains’ and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. Likewise, certain terms may be interchangeably used throughout the specification and thus have the same meaning even when they are referred interchangeably. For example, lime dissolved in water may be interchangeably referred as lime and moisture or lime water, CRM Oxide as red oxide, binder of the present disclosure as red oxide binder/red oxide based binder, iron ore pellets with bentonite binder alone as bentonite based pellet or bentonite-based pellet, etc.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.

The present disclosure relates to a binder which enables integrating reduction in bentonite consumption, better thermal shock property and cost effectiveness in pellet making. Particularly
the present disclosure relates to a binder comprising cold rolling mill oxide (CRM oxide/dust), humic acid and lime.
In another embodiment of the present disclosure, the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of about 75-85 wt%, humic acid at a concentration of about 10-15 wt% and lime at a concentration of about 5-10 wt%.
In another embodiment of the present disclosure, the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of about 80 wt%, humic acid at a concentration of about 13 wt% and lime at a concentration of about 7 wt% .
In another embodiment of the present disclosure, the cold rolling mill oxide (CRM oxide/dust) is obtained from, but not limiting to, pickling line as red oxide.
In another embodiment of the present disclosure, the humic acid is alkali based humic acid.
In another embodiment of the present disclosure, the alkali based humic acid is sodium based or potassium based.
The present disclosure also relates to a method for synthesizing the binder, comprising steps of:
 mixing cold rolling mill oxide (CRM oxide/dust), humic acid and lime dissolved in water; and
 ageing the mixture to obtain the binder.

In an embodiment of the present disclosure, the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of 75-85 wt%, humic acid at a concentration of 10-15 wt% and lime at a concentration of 5-10 wt%.In another embodiment of the present disclosure, the binder comprises cold rolling mill oxide (CRM oxide/dust) at a concentration of about 80 wt%, humic acid at a concentration of about 13 wt% and lime at a concentration of about 7 wt%.
In another embodiment of the present disclosure, the cold rolling mill oxide (CRM oxide/dust) is generated in cold rolling mill of steel plant.
In another embodiment of the present disclosure, the cold rolling mill oxide (CRM oxide/dust) is generated by spray roasting of acid pickling liquor in cold rolling mill of steel plant.
In another embodiment of the present disclosure, the humic acid is alkali based humic acid.
In another embodiment of the present disclosure, the alkali based humic acid is sodium based or potassium based.
In another embodiment of the present disclosure, lime is dissolved in water to obtain a slurry. Fume Extraction System (FES) dust and humic acid are mixed in the slurry to obtain a mixture;
In another embodiment of the present disclosure, lime at a concentration of about 5-10% is dissolved in water at a concentration of about 20-30% to obtain the slurry;
In another embodiment of the present disclosure, the ageing is carried out for about 2 to 8 days.
In another embodiment of the present disclosure, the ageing is carried out for about 5 days.
The present disclosure also relates to a method for improving thermal shock properties of iron ore pellets comprising steps of:
 mixing of iron ore fines, flux, carbon source, bentonite, and the binder along with moisture; and
 pelletizing the mixture to obtain the iron ore pellets with improved thermal shock properties.
The present disclosure also relates to a method for improving thermal shock properties of iron ore pellets comprising steps of:
 mixing of Ground Ore Concentrate (GOC), bentonite and the binder along with moisture; and
 pelletizing the mixture to obtain the iron ore pellets with improved thermal shock properties.
In an embodiment of the present disclosure, the iron ore fines are hematite-based iron ore fines.
In another embodiment of the present disclosure, the flux is selected from a group comprising CaO based flux, MgO based flux and combinations thereof.
In another embodiment of the present disclosure, the CaO based flux is selected from a group comprising, but not limiting to, limestone, slaked lime, calcined limestone and combinations thereof.
In another embodiment of the present disclosure, the MgO based flux is selected from a group comprising, but not limiting to, olivine, pyroxenite, dolomite and combinations thereof.
In another embodiment of the present disclosure, the carbon source is selected from a group comprising, but not limiting to, anthracite coal, coke fines and combinations thereof.
In another embodiment of the present disclosure, the method involves dry mixing of iron ore fines, flux, carbon source, bentonite and the binder followed by wet mixing with addition of moisture.
In another embodiment of the present disclosure, the Ground Ore Concentrate (GOC) comprises of hematite-based iron ore fines, limestone fines, olivine fines and carbon bearing solid fuel. GOC is produced during co-grinding of these raw materials in industrial unit of dry-grinding mill in steel plant.
In another embodiment of the present disclosure, the pelletization is carried out in disc pelletizer to obtain green pellets followed by induration in a furnace at a temperature ranging from about 1200°C - 1300°C to obtain the iron ore pellets.
In another embodiment of the present disclosure, the iron ore pellets of size ranging from 10 mm to 12.5 mm is obtained.
In another embodiment of the present disclosure, the binder partially replaces bentonite in pelletization.
In another embodiment of the present disclosure, the binder replaces bentonite in pelletization at a replacement ratio of 1:1.
The present disclosure also relates to use of the binder in preparation of iron ore pellets.
The present disclosure also relates to Iron ore pellets obtained by the above method.
In an embodiment of the present disclosure, the iron ore pellets of the present disclosure show better thermal shock properties as compared to the iron ore pellets with bentonite binder alone.
In another embodiment of the present disclosure, the iron ore pellets of the present disclosure show comparable physical strength such as green crushing strength, drop strength and dry crushing strength as that of the iron ore pellets with bentonite binder alone.
In another embodiment of the present disclosure, the iron ore pellets of the present disclosure show better cold crushing strength as that of the iron ore pellets with bentonite binder alone.
In an embodiment of the present disclosure, the red oxide based pellets show better thermal shock properties as compared to the bentonite based pellets.
In another embodiment of the present disclosure, the red oxide-based pellets show comparable physical strength such as green crushing strength, drop strength and dry crushing strength as compared to that of the bentonite-based pellets.
In another embodiment of the present disclosure, the red oxide-based pellets show better cold crushing strength as compared to that of the bentonite-based pellets.
In another embodiment of the present disclosure, use of the binder of the present disclosure leads to decrease in alumina and silica content in iron ore pellets produced by conventional methods. The red oxide-based binder of the present disclosure does not add any impurity material more than the bentonite binder such as Alkali and decreases gangue addition such as SiO2, Al2O3 etc.
In another embodiment, the binder of the present disclosure is easier to produce in terms of processing steps and decreases the cost of binders used in iron ore pelletizing.
In another embodiment, the present disclosure aims to decrease the bentonite consumption which contributes to higher alumina and silica in finished pellets.
In another embodiment, the CRM oxide used in the binder of the present disclosure is ultrafine in nature and does not require any grinding or milling process like bentonite. Due to its finer nature, it will age more properly along with humic acid and lime water. Moreover, the LOI is much lower than the bentonite.
Thus, the present disclosure relates to a red oxide based binder and methods thereof. CRM oxide is used as red oxide and a main raw material to prepare red oxide based binder along with humic acid and lime water, both of which act as an activator. These three components are mixed and then aged for 2-8 days. The present disclosure does not involve any costly process like drying and grinding. Therefore, its processing is cost efficient.
Red oxide based binder used in the present disclosure improves the thermal shock properties better than the bentonite based pellets. In this method, 75-85% CRM oxide, 10-15% humic acid and 5-10% lime (dissolved in water) is mixed and aged for 2-8 days. The binder prepared is used directly without grinding to replace bentonite partially.
The present invention is also directed to method of producing iron ore pellets by using, iron ore (hematite), CaO based fluxes (limestone, slaked lime, calcined limestone) and MgO based fluxes (olivine, pyroxenite and dolomite), carbon bearing solid fuel (anthracite coal, coke fines), binder (bentonite) and the red oxide binder along with moisture. Physical properties such as drop strength, Green Crushing Strength (GCS), Dry Crushing Strength (DCS) and Cold Crushing Strength (CCS)] achieved by using red oxide binder and bentonite is almost same as with bentonite-based pellets.
In conventional method, iron ore fines, fluxes, carbon bearing solid fuel and bentonite along with moisture is used to prepare iron ore pellet. It is known that haematite-based pellets generally show poor thermal shock properties if bentonite is not added in sufficient amount. However, there is a limit upto which bentonite can be added due to its negative impact such as high alumina and silica content plus it is costly. Therefore, the present disclosure aims to reduce consumption of bentonite by replacing the red oxide binder partially.
The present disclosure replaces bentonite successfully without deteriorating the physical strength and thermal shock properties of pellets.
It is to be understood that the foregoing description is illustrative not a limitation. While considerable emphasis has been placed herein on particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.
Descriptions of well-known/conventional methods/steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure, certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments may be practiced and to further enable those of skill in the art to practice the embodiments. Accordingly, following examples should not be construed as limiting the scope of the embodiments herein.
EXAMPLES:
Example 1: Synthesis of red oxide binder
In synthesizing the binder of the present disclosure, 80% CRM oxide, 13% humic acid and 7% lime dissolved in 28% moisture is mixed and aged for 5 days. The binder prepared is used directly without grinding to replace bentonite partially.
Initially, 7% lime is dissolved in 28% moisture/water to obtain a slurry. 80% CRM oxide and 13% humic acid are mixed in the slurry to obtain a mixture which is aged for 5 days to obtain the binder.
Particle size analysis of raw materials used for preparing the red oxide based binder is done by using wet sieving method and is provided in Table 1.

Table 1: Particle size analysis of raw material used for red oxide binder preparation
Size range (μm) CRM dust (wt.%) Lime (wt. %) Humic acid (wt. %)
-45 98.03 82.8 94

Example 2: Pellet Preparation

Three sets of green pellets were prepared to observe the improvement in thermal shock properties based on the red oxide binder. Comparison was done between bentonite-based pellet and bentonite plus red oxide binder based pellet. Chemical analysis of raw material used for pellet preparation is provided in Table 2.

Table 2: Raw material chemical analysis
Raw Material Fe(T) FeO CaO SiO2 MgO Al2O3 K2O Na2O C LOI
GOC 58.4 9.68 1.6 4.65 1.87 2.87 0.05 0.02 0.87 5.59
Bentonite 10.23 - 1.48 38.02 1.98 13.99 0.08 2.23 - 24.6
CRM Dust 69.09 0.26 0.01 0.01 0.027 0.16 - - 0.01 -
Lime 0.45 - 89.85 1.02 0.84 0.04 - - - 7.11
Red Oxide binder 59.53 - 7.23 0.09 0.09 0.05 0.005 0.021 - 14.16

The process of green pellet preparation involves use of Ground Ore Concentrate (GOC) which is collected from Tata Steel Pellet Plant. GOC comprises of hematite-based iron ore fines, limestone fines, olivine fines and carbon bearing solid fuel. GOC is produced during co-grinding of these raw materials in industrial unit of dry-grinding mill in Tata Steel pelletizing plant at Jamshedpur, India.
The amount of ingredients added for preparing green pellet is shown in Table 3. Based on this amount, raw material on dry basis was weighed and mixed together in turbo mixer (make- Insmart, capacity 10L) for 30 minutes in dry condition. Then, wet mixture is prepared in high intensity bladed mixer with 8.5% moisture. Prepared wet mixture is then used for preparation of green pellets in disc pelletizer. The size of prepared green pellet was 10-12.5 mm.

Table 1: Mass balance for preparing green pellet
Pellet Id GOC Bentonite Red oxide binder
Set 1
(base case) 99.5% 0.5% 0.0%
Set 2 99.5% 0.4% 0.1%
Set 3 99.5% 0.4% 0.0%

Example 3: Properties of the prepared pellets
Tests like GCS - green crushing strength (Figure 2) and drop strength test (Figure 1) was performed on green pellets so prepared in Example 2. After drying green pellet at temperature 105°C±5, dry crushing strength (DCS) test was done (Figure 3). The green pellets were also exposed to the thermal shock test designed with heating patterns like Tata Steel 6 MTPA Pellet plant. The peak shock temperature given to pellet was 500°C wherein pellets were heated to reach 500°C at a heating rate of ~67 °C/min. The number of un-cracked pellets (Figure 4), cracked pellets and burst pellets (Figure 5) were counted and relative percentage, with Set 1 being the reference, is reported. Further, pellets were also fired at 1300 °C to see its effect on Cold Crushing Strength (Figure 6).
According to Figures 1-3, green properties such as drop strength, GCS and DCS for all set of pellets are comparable
Figure 4 shows that relative percentage of un-cracked pellet for set 2 was on the higher side in comparison with sets 1 and 3. Figure 5 shows that no cracked pellet was observed for sets 1 and 2 but for set 3, relative percentage of cracked pellet was 13%. Even relative percentage of burst pellet was lower for set 2 when compared with set 1 and 3 as shown in Figure 6. Cold crushing strength achieved for set 2 is higher than set 1 and 3 as shown in Figure 7. Thus, set 2 pellets show better thermal shock properties in comparison with only bentonite-based pellets (Sets 1 and 3).