DESC:FIELD OF THE INVENTION
[001] The invention relates to field of construction material, more particularly to a clinker composition and especially to the sodium aluminium silicate-based cement clinker composition and a preparation method thereof.

BACKGROUND OF THE INVENTION
[002] Concrete is a man-made material. A typical concrete is made by mixing Portland cement, water and aggregates such as sand and crushed stone. Portland cement is a synthetic material made by burning a mixture of ground limestone and clay, or materials of similar composition in a rotary kiln at a specified sintering temperature.
[003] Cement clinker can be described essentially as a solid material produced during the manufacture of Portland cement as an intermediary product. Clinker occurs as lumps or nodules and is produced by sintering i.e., fusing together without melting to the point of liquefaction, limestone and aluminosilicate materials such as clay during the cement kiln stage.
[004] The process of making hydraulic binders, and specifically cements, involves calcining a mixture of precisely chosen and dosed raw materials, also referred to as "crude." This crude is cooked to produce clinker, an intermediate product that, when crushed with potential mineral additives, produces cement.
[005] Clinker is lumps or nodules that are typically 3 mm to 25 mm in diameter and are produced as a result of the burning of the kiln stage. CaO, SiO2, Al2O3, and Fe2O3 make up more than 95% of cement clinker, while MgO, TiO2, P2O5, and alkalis make up the remaining less than 3%.
[006] These elements do not exist as single oxides, but rather as compounds made up of two or more oxides. The clinker's component minerals are C3S, C2S, C3A, and C4AF.
[007] Alite (C3S), which accounts for 50–70% of typical Portland cement clinkers, is the most significant component. It is tricalcium silicate (Ca3SiO5) that has undergone ionic substitutions to alter its chemistry and crystal structure. It produces most strength up to and including 28 days. The 28-day EN 196 mortar strength improves by around 5 MPa for every 10% increase in C3S concentration.
[008] Cement clinker manufacturing is an energy-intensive process. The chemical makeup of the feed affects the melt's actual melting temperature. Therefore, the efficiency of cement plants and energy usage depend greatly on the chemical composition of cement raw materials and clinker.
[009] There has been growing effort to reduce the energy required for manufacturing the cement clinker especially by reducing the sintering temperature at the same time enhancing the properties of the clinker composition. Hence to overcome at least one of the problems, there exists a need for cement clinker composition which can be prepared in a less energy intensive process thereby reducing the cost of production and demonstrates enhanced properties.
[010] To meet this formidable challenge, a revolutionary approach to cement clinker manufacturing has been developed that significantly reduces the energy requirement of a cement plant.
[011] With the mass exploitation of natural resources, cement production raw materials are increasingly scarce, the high-value industrial raw materials results in a high production cost and this can impact the large-scale production of cement. Therefore, various cheap industrial solid wastes are adopted to produce the mineral based cement clinker, to enable the low-cost preparation of the cementing material. The waste material are low quality, highly crystalline, hard and compact in nature.
[012] Further, the present invention provides the cement clinker composition which can be prepared in a less energy intensive process, by reducing the sintering temperature and thereby further reducing the cost of production with enhanced properties.
[013] The mining waste materials are preferably selected from sodium aluminium silicate-based which is thought to provide the cement with early strength and quick hardening.

SUMMARY OF THE INVENTION
[014] Accordingly, an aspect of the present invention is to provide a cement clinker composition comprising Limestone, Laterite, Industrial waste and Mining waste wherein the industrial waste is selected from Basic Oxygen Furnace (BOF) slag, a waste material from iron & steel Industry.
[015] Another aspect of the present invention is to provide a method of preparing clinker composition in a less energy intensive process thereby reducing the cost of production and enhancing the properties.
[016] Yet another aspect of the present invention is to provide utilization of clinker composition in the preparation of concrete.

FIGURES OF THE INVENTION:
[017] Figure 1 depicts clinker nodules - raw mix.
[018] Figure 2 depicts clinker nodules after overnight drying of at 100°C.
[019] Figure 3 depicts sintering of clinker nodules - Sintered at high temperature of 1300°C ,1350°C, 1400 °C & 1450 °C for 30 Minutes.
[020] Figure 4 depicts the clinker nodules produced according to the present invention.

DEFINTIONS:
[021] As used in the present invention, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
[022] Limestone: limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3), usually in the form of calcite or aragonite. It may contain considerable amounts of magnesium carbonate (dolomite) as well; minor constituents also commonly present include clay, iron carbonate, feldspar, pyrite, and quartz. It is used as a raw material for cement clinker.
[023] Laterite: A laterite in the context of the present invention is defined as a soil, rich in Fe2O3 and Al2O3 and yellowish to reddish in colour. Laterite is derived from weathering.
[024] Industrial and mining waste: An industrial and mining waste in the context of the present invention is defined as waste material generated from iron and steel industry during manufacture of pig iron.
[025] Mining waste includes amphibolite’s, pegmatite and basalt which are present as intercalation with limestone. Amphibolite is the metamorphic rock and pegmatite & basalt are igneous rock.
[026] Basic Oxygen Furnace (BOF) slag: A BOF slag is commonly known as steel slag or LD slag, waste material from iron & steel industry. LD slag is generated in the steel-making process during the transformation of pig iron to liquid steel. The letters LD come from the fact that the steel is produced in an LD type oxygen converter.
[027] Alite: Alite (C3S) constitutes 50-70% in normal Portland cement clinkers. It is tricalcium silicate (Ca3SiO5). C3S is responsible for early strength i.e. upto 1D strength.
[028] Belite: Belite (C2S) constitutes 15-30% of normal Portland cement clinkers. It is dicalcium silicate (Ca2SiO4), it reacts slowly and improves later strength (=28 days).
[029] Aluminate: Aluminate (C3A) constitutes 5-10% of normal Portland cement clinker; it is tricalciumaluminate (Ca2Al2O6). It releases a lot of heat, shortens setting time and improves very early strength, but it lead the cement to make prone to sulphate attack.
[030] Ferrite: (C4AF) it constitutes up to 5-15% of normal Portland cement clinkers. It is a tetracalcium aluminoferrite (Ca4AlFeO5).
[031] Lime saturation factor (LSF): The lime saturation factor is a measure of the degree of conversion of silica, alumina, and iron oxide into the corresponding lime in the Kiln during the clinker preparation.
[032] Silica modulus (SM): Silica modulus essentially governs the proportion of silica phases in clinker or is the indicator of burnability of the feed or clinker. It is ration of contents of oxides of silica and oxides of alumina and iron.
[033] Alumina modulus (AM): The alumina modulus is also used as an indicator of burning temperature and flux characteristic in the kiln. It is the measure of the proportion of alumina to iron oxide in the mix.
[034] It is to be noted that the term "comprising", used in the description and claims are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps and should not be interpreted as being restricted to the means listed thereafter. It is thus to be interpreted as specifying the presence of the stated features, steps or components as referred to, but does not preclude the presence or addition of one or more other features, steps or components, or groups thereof.
[035] Throughout this specification, reference to "embodiment” “aspect” indicate that a particular feature or function respectively, described in relation to the embodiment or aspect is included in at least one embodiment or aspect of the present invention. Thus, appearances of the phrases "in one embodiment" or "in preferred embodiment" or “in one aspect” or “in preferred embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, or aspect.
[036] Dependent claims features may be combined with features of the other independent or dependent claims or with the features mentioned in the description as appropriate for interpretation of scope and enablement of the claims and description. Furthermore, the features or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art.

DETAILED DISCRIPTION:
[037] Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminium, iron and other ingredients. Limestone, shells and chalk or marl are frequently combined with shale, clay, slate, blast furnace slag, silica sand and iron ore to make cement. These materials form a rock-like substance that is pulverised into the fine powder when heated to high temperatures (about 1350–1400°C).
[038] During the manufacturing of Cement clinker are produced during the manufacture of Portland cement as an intermediary product and occurs as lumps or nodules of diameter 3-25 mm. Clinker, when added with gypsum (to control the setting properties of cement and ensure compressive strength) and ground finely, produces cement.
[039] Clinker can be kept dry for extended periods of time without losing quality, it is traded internationally and used by cement producers when raw materials are in short supply.
[040] Effects and control of chemical composition of clinker is an important of the cement manufacturing process. In cement production the effects of chemical composition of clinker in the process materials and finished products has to be analyzed, monitored and effectively control to optimize the process and a consistent desired product quality of cement.
[041] In a preferred embodiment of the present invention, the clinker composition comprises limestone, laterite, industrial waste and mining waste.
[042] In another preferred embodiment of the present invention, the composition comprises: limestone in the range of 95 % to 99 % by weight of the composition; laterite in the range of 0.1 to 2.5% by weight of the composition; industrial waste in the range of 0.5% to 2% by weight of the composition; and mining waste in the range of 0.3% to 2.5 % by weight of the composition.
[043] In yet another preferred embodiment of the present invention, the composition comprises: limestone in the range of 97 % to 98 % by weight of the composition; laterite in the range of 0.5 to 0.8% by weight of the composition; industrial waste in the range of 1% to 2% by weight of the composition; and mining waste in the range of 0.3% to 0.5 % by weight of the composition.
[044] In another embodiment of the invention, industrial waste is selected from Basic Oxygen Furnace (BOF) slag, a waste material from iron & steel Industry. produced during the conversion of pig iron to liquid steel in the process of manufacturing steel. It is essentially the result of the oxidation of hot metal elements (Si, Mn, and Fe) and the dissolving of lime and dolomite.
[045] Other industrial waste such as ceramic waste, Fly Ash, Rice Husk Ash (RHA), Petcoke Ash, silica fume, hypo sludge, quarry dust, sewage sludge ash, Ground-granulated blast-furnace slag (GGBS) or any other industrial waste as replacement may be utilized.
[046] In another embodiment of the invention, the mining waste of composition comprises preferably of sodium aluminium silicate-based mineral. Further, mining wastes include waste generated during the extraction, beneficiation, and processing of minerals.
[047] Present invention utilizes the Sodium aluminium silicate mining waste which is thought to which is thought of to promote the formation of alite and provide the early cement early strengthening and quick hardening and high impermeability.
[048] In another preferred embodiment of the invention, the mining waste is selected from pegmatite, amphibolite and basalt or combination thereof.
[049] In an exemplary embodiment of the present invention the pegmatite is composed of alkali feldspar usually micro perthite which occur as anhedral megacrysts characterized by fine strings and braided veinlets of albite intrusions. It occurs as small veins, lenses and large conspicuous bodies within limestone bands and as well as separate entities. It has a specific gravity 2.60 to 2.63 and bulk density of 2.70 to 2.71. Microcline (KAlSi3O8), quartz (SiO2) and albite (NaAlSi3O8) are the major minerals followed by accessory minerals like muscovite (KAl2(AlSi3O10)(F,OH)2 and calcite (CaCO3).
[050] In an exemplary embodiment of the present invention the amphibolite occurs within limestone. They are dark brown and grey in colour, medium to fine grained, massive and compact. These are inter-bedded with limestone and generally follows bedding planes. It has specific gravity of 2.9 to 3.0, bulk density of 2.9 to 3.0. Further, hornblende (Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22(OH)2 and albite (NaAlSi3O8) are the major mineral whereas quartz(SiO2), calcite(CaCO3), dolomite(MgCO3), anorthite(CaAl2Si2O8), and magnetite(Fe3O4) are present as the accessory minerals in the rock.
[051] In an exemplary embodiment of the present invention the basalt is a fine grained, dark coloured igneous rock composed mainly of plagioclase and pyroxene group of minerals. The physical property of basalt like specific gravity is 2.70 –3.3 and bulk density is 2.79. The mineralogy of basalt includes quartz (SiO2), anorthite (CaAl2Si2O8), pyroxene [Ca (Mg, Fe) Si2O6], fayalite (Fe2SiO4), kaolinite -Al2Si2O5(OH)4 present as major and minor minerals.
[052] Another aspect of the invention discloses the method of preparation of the mineral based clinker, wherein mineral based clinker is obtained by mixing and jointly grinding the raw materials; or respectively grinding the raw materials and then mixing to obtain the homogenous mixture.
[053] In one aspect of the invention the method of preparing clinker composition comprises the steps:
- Mixing and grinding of limestone, laterite and industrial waste to form a homogenous mixture;
- Adding industrial waste to the homogenous mixture resulting in ‘raw mix’;
- the ‘raw mix’ is sintered in a high temperature furnace to make the clinker composition.
[054] In one aspect of the invention the method comprises the step of mixing and grinding of:
- limestone in the range of 95 % to 99 % by weight of the composition;
- laterite in the range of 0.1 to 2.5% by weight of the composition;
- industrial waste in the range of 0.5% to 2% by weight of the composition; and
- mining waste in the range of 0.3% to 2.5 % by weight of the composition.
[055] In preferred aspect of the invention the limestone is in the range of 97 % to 98 % by weight of the composition, laterite is in the range of 0.5 to 0.8% by weight of the composition, industrial waste is in the range of 1% to 2% by weight of the composition are mixed and grinded to obtain the homogenous mixture.
[056] In preferred aspect of the invention the 97% limestone, 2% laterite and 1% industrial waste from steel industries are mixed to form a homogenous mixture.
[057] In another aspect of the invention, grinding of limestone, laterite and LD slag is done by keeping 14-15 % residue at 90-micron sieve.
[058] In said method of preparation of clinker composition, the suitable alumina-silicate mining waste is added separately resulting in ‘raw mix’.
[059] In a preferred embodiment of the preparation, the suitable alumina-silicate mining waste like Pegmatite, Amphibolite & Basalt are added separately resulting in ‘raw mix’.
[060] In preferred aspect of preparation, the suitable alumina-silicate mining waste like Pegmatite, Amphibolite & Basalt in the range of 0.3% to 0.5 % is added separately resulting in ‘raw mix’.
[061] The prepared ‘raw mix’ nodules is further sintered in a high temperature furnace in the range of 1200°C to 1500 °C, preferably 1300°C to 1450 °C.
[062] In a preferred embodiment, the ‘raw mix’ nodules is further sintered in a high temperature furnace in the range of 1300°C, 1350°C, 1400 °C & 1450 °C for retention period of 30 minutes inside the Kiln. The mixture inside the slightly inclined kiln is rapidly cooled from 2000°C to 100°C-200°C. Thus, the final product, is produced, and then stored, ready to produce cement.
[063] In a preferred embodiment of the present invention, the industrial and mining waste is adopted to clinker composition so that the resource utilization of the solid waste can be promoted. The synergistic and complementary advantages of utilizing various solid industrial and mining wastes are beneficial for waste utilization and coordinated development of energy reduction and waste resources utilization and environment cleaning.
[064] EXAMPLES:
[065] Example 1: Raw Material Analysis
Chemical composition of the raw materials (wt%) used in the invention are as follows:
Table 1: Raw Materials Analysis (wt%)
Limestone Laterite LD Slag Basalt Pegmatite Amphibolite Petcoke Ash
LOI 39.02 9.83 8.16 4.07 2.06 1.87 0.41
SO3 0.04 0.12 0.01 0.02 0.1 0.06 14.82
SiO2 7.54 23.6 12.2 47.91 69.16 54.32 41.46
Al2O3 2.45 19.07 4.3 14.14 14.85 16.84 21.83
Fe2O3 1.27 46.18 22.85 12.96 2.11 7.78 20.78
CaO 46.2 0.78 47.04 12.22 1.15 13.44 0
MgO 2.62 0 3.63 4.24 0.45 3.43 0
Na2O 0.15 0.1 0.35 2.28 2.48 1.32 0.29
K2O 0.08 0.31 0.73 1.41 7.62 0.36 0.05
Total 99.37 99.99 99.27 99.25 99.98 99.42 99.64

[066] Example 2: Preparation of clinker
The clinker composition was prepared through the following steps:
a. Ground the raw material by keeping 14-15% residue on 90 micron sieve;
b. mixing limestone (97%), laterite (2%) and industrial waste from steel industries (1%) to form a homogenous mixture;
c. Adding 1-2% Alumino-silicate based material like Pegmatitie, Amphibolite & Basalt separately;
d. Around 1-2 mm nodule have prepared and dried overnight at 100°C
e. Sintering the nodule to a temperature in the range of 1300°C to 1350°C, 1400 °C & 1450 °C;
f. The heating and cooling rate is 10 °C/min and retention time at 1300°C, 1350°C, 1400 °C & 1450 °C is 30 minutes.

[067] Analysis of the chemical composition of the ‘raw mix’ for the clinker is as follows:
Table 2: Raw Mix preparation for Clinker
Types of RM RM% SiO2 Al2O3 Fe2O3 CaO MgO LOI Na2O K2O SO3 LSF SM AM
Limestone 97.0 11.32 3.29 2.09 40.95 3.44 36.32 0.15 0.08 0.01 110.67 2.1 1.57
Laterite 2.0 23.6 19.07 46.18 0.78 0 9.83 0.18 0.06 0.12 0.66 0.36 0.41
LD slag 1.0 12.2 4.3 25.2 47 3.63 8.16 0.35 0.73 0.01 84.38 0.41 0.17
Raw Mix 100 11.57 3.62 3.2 40.21 3.37 35.51 0.15 0.09 0.01 103.55 1.7 1.13
Ignited Mix 98.75 17.95 5.61 4.97 62.34 5.23 0 0.23 0.13 0.02 103.55 1.7 1.13
Ash 1.25 41.46 21.83 20.78 0 0 0 0.29 0.05 14.82 --- --- ---
Clinker 100 18.24 5.81 5.16 61.56 5.16 0 0.23 0.13 1.54 98.5 1.66 1.12

[068] The clinker prepared according to the method is shown in Figure 4.
[069] Example 3: Analysis of the clinker-1
Chemical and mineralogical analysis of clinker prepared with Pegmatite according to the present invention is provided below:
Table 3: Clinker comprising Pegmatite
@ 1300°C @ 1350°C @ 1400°C @ 1450°C
Chemical Analysis (Wt%)
SiO2 21.04 21.01 21.13 20.89
Al2O3 5.26 5.39 5.33 5.3
Fe2O3 3.35 3.41 3.43 3.43
CaO 63.72 63.63 63.67 63.91
MgO 4.56 4.46 4.49 4.47
P2O5 0.08 0.08 0.08 0.08
SO3 0.3 0.13 0.10 0.11
K2O 0.62 0.83 0.73 0.73
Na2O 0.35 0.33 0.34 0.35
TiO2 0.31 0.32 0.31 0.32
Mn2O3 0.11 0.11 0.10 0.11
Mineralogical Analysis
C3S 58.52 57.92 57.61 60.53
C2S 16.15 16.51 17.10 14.23
C3A 8.26 8.51 8.33 8.25
C4AF 10.21 10.38 10.42 10.43
fCaO 10.51 3.11 1.42 1.25

[070] Clinker made with pegmatite having free lime content is around 1.42% @ 1400 °C indicates good burning and the thermal saving is around 50°C. Accordingly, the reactivity and burnability of the raw mix improved.
[071] At 1450°C, C3S content has increased around 2.9% after adding the pegmatite will increase one day strength.
[072] Example 4: Analysis of the clinker-2
Chemical and mineralogical analysis of clinker prepared with Amphibolite according to the present invention is provided below:
Table 4: Clinker comprising Amphibolite
@ 1300°C @ 1350°C @1400°C @ 1450°C
Chemical analysis of clinker (Wt%)
SiO2 20.51 20.44 20.58 20.62
Al2O3 5.36 5.37 5.32 5.28
Fe2O3 3.47 3.52 3.54 3.54
CaO 64.05 64.22 64.06 64.2
MgO 4.52 4.45 4.48 4.46
P2O5 0.08 0.08 0.08 0.08
SO3 0.15 0.09 0.11 0.05
K2O 0.78 0.76 0.74 0.70
Na2O 0.34 0.35 0.35 0.35
TiO2 0.32 0.32 0.32 0.32
Mn2O3 0.11 0.10 0.11 0.11
Mineralogical analysis of clinker (Wt%)
C3S 63.43 64.74 63.29 64.02
C2S 10.95 9.75 11.23 10.79
C3A 8.34 8.27 8.13 8.00
C4AF 10.57 10.71 10.76 10.76
fCaO 10 3.76 2.19 1.62

[073] Clinker made with amphibolite having free lime content is around 2.19% also indicating good burning of clinker with 50°C saving of thermal energy. No impact of C3S content have been noticed.
[074] Example 4: Analysis of the clinker-3
Chemical and mineralogical analysis of clinker prepared with Basalt according to the present invention is provided below:
Table 5: Clinker comprising Basalt
@ 1300°C @1350°C @ 1400°C @ 1450°C
Chemical Composition (Wt%)
SiO2 19.67 19.94 20.18 20.22
Al2O3 5.14 5.11 5.06 5.00
Fe2O3 3.29 3.33 3.31 3.29
CaO 65.32 65.22 65.23 65.31
MgO 4.66 4.51 4.37 4.40
P2O5 0.07 0.07 0.07 0.07
SO3 0.00 0.01 0.00 0.02
K2O 0.79 0.77 0.73 0.67
Na2O 0.34 0.34 0.35 0.35
TiO2 0.32 0.32 0.32 0.32
Mn2O3 0.09 0.10 0.09 0.10
C3S 77.23 74.90 73.47 73.98
C2S 1.89 0.64 2.43 2.16
C3A 8.05 7.92 7.81 7.68
C4AF 10.02 10.13 10.06 10.00
fCaO 11.8 6.87 5.43 4.81

[075] No improvement in clinker behaviour both in terms of thermal energy & C3S content have been noticed with clinker prepared from basalt.
[076] Clinker burned with basalt indicates no improvement in thermal and C3S content compared with amphibolite and basalt.
[077] The foregoing description of the invention has been set merely to are only the preferred embodiments to illustrate the invention and is not intended to be limiting. Since the modifications and equivalent can be made in the technical solution of the disclosed embodiments incorporating the spirit and substance of the invention may occur to the person skilled in the art, the invention should be construed to include everything within the protection scope of the invention.
,CLAIMS:We Claim:

1. A clinker composition comprising:
- Limestone
- Laterite;
- Industrial waste; and
- Mining waste;
wherein the industrial waste is selected from Basic Oxygen Furnace (BOF) slag or a waste material from iron & steel industry.

2. The clinker composition as claimed in claim 1, wherein mining waste comprise sodium aluminium silicate.

3. The clinker composition as claimed in claim 1 to 2, wherein the mining waste is selected from pegmatite, amphibolite and basalt or combination thereof.

4. The clinker composition as claimed in claim 1 to 3, wherein:

- limestone in the range of 95 % to 99 % by weight of the composition;
- laterite in the range of 0.1 % to 2.5 % by weight of the composition;
- industrial waste in the range of 0.5 % to 2 % by weight of the composition; and
- mining waste in the range of 0.3 % to 2.5 % by weight of the composition.

5. The clinker composition as claimed in claim 1 to 4, wherein limestone is 97 wt%, laterite is 2 wt% and industrial waste from steel industries is 1 wt% of the composition.

6. A method of preparing clinker composition comprises the steps:
(a) mixing and grinding of limestone, laterite and industrial waste to form a homogenous mixture;
(b) adding industrial waste to the homogenous mixture resulting in ‘raw mix’;
(c) the ‘raw mix’ is sintered in a high temperature furnace to make the clinker composition.

7. The method as claimed in claim 6, wherein the
- limestone in the range of 95 % to 99 % by weight of the composition;
- laterite in the range of 0.1 % to 2.5 % by weight of the composition;
- industrial waste in the range of 0.5 % to 2 % by weight of the composition; and
- mining waste in the range of 0.3 % to 2.5 % by weight of the composition.

8. The method as claimed in claim 6, wherein 97 wt% limestone, 2 wt% laterite and 1 wt% industrial waste from steel industries are mixed and grinded to form a homogenous mixture.

9. The method as claimed in claim 6, wherein mining waste comprise sodium aluminium silicate preferably selected from pegmatite and amphibolite in the range of 0.3 wt% to 0.5 wt% of the composition.
10. The method as claimed in claim 6, wherein the ‘raw mix’ is sintered in a high temperature furnace in the range of 1200°C to 1500 °C, preferably 1300°C to 1450 °C.

11. The method as claimed in claim 6, wherein the heating and cooling rate during sintering is 10 °C/min and retention time at 1300°C ,1350°C, 1400 °C & 1450 °C is 30 Minutes.

12. The method as claimed in claim 6, wherein step (a) is done by keeping 14-15 % residue at 90-micron sieve.

13. The method as claimed in claim 6, wherein 1-2 mm nodule is prepared and dried overnight at 100°C before step (c).

Dated this 28th day of June 2022.
Nuvoco Vistas Corporation Limited
By their Agent & Attorney

(Adheesh Nargolkar)
of Khaitan & Co
Reg. No. IN/PA-1086