DESC:FORM 2

THE PATENT ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006

COMPLETE SPECIFICATION
(See section 10 and rule 13)

TITLE OF THE INVENTION
A method of enhancing the whiteness of white portland clinker and cement thereof.

APPLICANTS
Aditya Birla Science and Technology Company Pvt Ltd, Plot number 1 and 1-A/1, Taloja, MIDC, Taluka- Panvel, District- Raigad- 410208, Maharashtra, India.

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[001] The present invention relates to a method of enhancing the whiteness of white portland clinker and cement thereof. More particularly, the present invention relates to a method of enhancement of whiteness of white portland clinker as well as its reactivity and burnability.

BACKGROUND OF THE INVENTION
[002] Whiteness is one of the most important properties of white cement. White Cement manufacturers face the variation in clinker raw material owing to the geological distribution in the limestone mine and clay. This sometime leads to decrease in whiteness index of white cement. However, this inconsistency is not accepted in the market place.

[003] Any increase in whiteness must be considered at the very early stages of cement manufacturing, preferably in selection of the raw materials for clinker making. White cement is made from raw materials with a low content of colouring elements such as Fe, Mn, Cr and Ti. It is made of high-grade limestone less than 0.068 wt.% Fe2O3 and white clay or kaolin and other materials which should not contain more than 0.35 wt.% Fe2O3.

[004] During Clinkerization, the clinker is present either in solid phase or a liquid phase. Majority of the clinker remains as solid. At the highest temperatures reached by the clinker, perhaps only about 25% of the clinker is in a liquid state. The solid phases are mainly Alite, Belite and free lime. The ionic liquid is vital in that it acts a flux, promoting reactions by ion transfer and without the liquid phase, combinability would be poor, and it would be very difficult to make cement clinker.

[005] The liquid phase is composed largely of oxides of aluminium, with some silicon and other minor elements. Iron oxide also plays an important role for liquid formation in case of grey cement. As the clinker leaves the kiln and cools down, crystals of aluminate and ferrite form from the liquid. Although there is SiO2, Al2O3 and Fe2O3 in the limestone, these oxides are mainly contributed by the clay. However, for the manufacturing of white cement clinker, along with Al2O3, clay also contains some amount of Fe2O3, that adversely affects the whiteness index of white cement.

[006] The content of Fe2O3 in white cement may vary over the range of 0.35 to 0.5 wt.%. The iron oxides are responsible for a greenish shade of the clinker which would be undesirable for example for architectural applications of white cement.

[007] Moreover, in the white Portland Cement manufacturing process, fuel costs during the clinkering stage account for approximately 30–50% of cement production costs. This percentage is due to the high kiln operation temperature, which is around 1500°C. Many solutions have been proposed to address these drawbacks. The use of mineralizers has proven to be a very good option in this regard. Mineralization accelerates the formation process of the main constitutive phases of the clinker (C3S and C2S) by changing their thermodynamic stability. This allows them to appear at a lower temperature.

[008] The inclusion of minor elements from mineralizers can lead to modifications in the hydraulic activity of silicates, due to the formation of solid solutions or changes in their structure. Moreover, mineralizers can act as fluxes and melt at a lower temperature than the compound of interest, in this case the calcium silicates. Fluxes decrease the temperature at which aluminium and iron oxide melt. Furthermore, they decrease the viscosity and surface tension of the liquidus that facilitate the transport of reactants and allow silicates to form at lower temperatures. However, mineralizers are very costly, and it increases the cement production cost.

[009] Lastly, aluminium scrap recycling generates important amounts of dross, which forms on the surface of the aluminium liquid bath. There are several methods for the treatment of this by-product and most of them focus on the recovering of metallic aluminium; its composition varies depending on the purification procedure, in general, it may contain Al2O3, SiO2, MgO, Al and very minor quantities of Si, Fe and Mg. Therefore, there is a need of a method that overcomes some of the difficulties of the prior art.
SUMMARY OF THE INVENTION
[010] An object of the invention is to provide a method to improve the whiteness of white cement/clinker by overcoming the drawback of the prior art.

[011] Another object of the invention is to replace the mineralizers used during cement production to reduce cost and improve whiteness.

[012] To achieve the objects, the invention provides a method to enhance the whiteness index of a white cement comprising by partly substituting clay and mineralizer with aluminium dross during clinkerization.

[013] The partial replacement of clay and mineralizer with aluminium dross increases the formation of alite and tri-calcium aluminate clinker phase.

BRIEF DESCRIPTION OF THE EMBODIMENTS
[014] The invention summarized above and defined by the enumerated claims may be better understood by referring to the following description, which should be read in conjunction with the accompanying claims. This description of an embodiment, set out below to enable one to build and use an implementation of the invention, is not intended to limit the invention, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention.

[015] It is to be noted that, as used in the specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds.

[016] It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[017] The expression of various quantities in terms of “%” or “% w/w” means the percentage by weight, relative to the weight of the total solution or composition unless otherwise specified.

[018] The term “clinker” used herein refers to nodular material produced in the kilning stage during the production of cement and is used as the binder in many cement products.

[019] The term “clinkerization” used herein refers to a process that signifies conversion of raw meal into clinker minerals mainly consisting of C4AF(Aluminoferite), C3A(Aluminite), C2S(Belite) and C3S (Alite) phases along with small percentage of free lime CaO, MgO, Alkalies, Sulphates etc. The conversion taking place in kiln system as raw meal is heated gradually to clinkerization temperature (1450 0C).

[020] The term “aluminium dross” used herein refers to a by-product of the aluminium smelting process, can be mechanically recycled to separate the residual aluminium metal from the aluminium oxide.

[021] The embodiments of the present invention aim at decreasing the total Fe and Ti content of white cement clinker for the enhancement of whiteness index of white cement. The present invention relates to a method of employing aluminium dross in raw materials as a partial replacement of clay and mineralizer for the enhancement of whiteness index of white Portland clinker and cement thereof.

[022] In an embodiment, the invention provides a method to enhance the whiteness index of a white cement comprising partly substituting clay and mineralizer with aluminium dross during clinkerization.

[023] The replacement of clay and mineralizer increases the aluminium oxide concentration in the clinker raw material and reduces the concentration of ferric oxide and titanium oxide in the clinker raw material. The partial replacement of aluminium dross augments the formation of alite and tri-calcium aluminate clinker phase during clinkerization.

[024] In an embodiment, the amount of aluminium dross added during clinkerization is in the range of 0.2 % to 10%. Partial blending (0.2 % to 10%) of aluminium dross in raw materials of clinker as a partial replacement of clay and mineralizer enhanced the whiteness index of white Portland Cement. It also improves the burnability of the white cement clinker besides enhancing the formation of key cement clinker phases responsible for the improvement of whiteness index of white cement clinker/white cement.

[025] The present invention aims to increase the whiteness index of white cement/ clinker by 1% to 10% by using aluminium dross in raw material by partial replacement of clay and mineralizer to decrease the iron and other colour bearing oxides/phases in the raw meal.

[026] In the present invention, the use of aluminium dross decreases the use of mineralizer. The extra alumina in aluminium dross increases the liquid percentage during clinkerization process and works as a flux during clinkerization process.

WORKING EXAMPLES
[027] Advantages and benefits of the present process according to the embodiments of the present invention would become more apparent from the below experimental details to a person skilled in the art.

[028] For this purpose, two kinds of clinkers were prepared: one was prepared by the use of Aluminium Dross by partial replacement of Clay and Mineralizer (Limestone, White Clay, Aluminium Dross and Fluorspar); the other was prepared by regular raw material (Limestone, White Clay and Fluorspar) as a reference. Raw meals (RM) were made into nodules of roughly 1gm each with distilled water by hand. These nodules were left to dry in an oven at 60°C for a few hours. They were heated in platinum crucibles in the furnace; furnace program is given as follows:
i. Ramping at 10°/min till 1200°C
ii. Ramping at 5°/min till 1450°C
iii. Dwelling for 45 mins at 1450°C

[029] The clinkers thus formed were removed and quenched by dipping into the quenching liquid, removing immediately and keeping for drying on filter paper. The damp clinkers were then left to dry in the oven at 60°C for several hours. The dried clinkers were ground in a cup mill for roughly 2-3 minutes to get required blain size. Each powdered sample was then submitted for spectrophotometric measurements for determination of Hunter Whiteness.

[030] Hunter Whiteness was found to increase up to 10 points in experimental sample prepared with Dross as compared to the control. The reactivity and burnability of raw meal, mineralogical composition and physical properties of clinker, and hydration characteristic of cement were also studied by burnability analysis, X-ray diffraction, and hydration analysis. In addition, the use of Dross was found to improve the reactivity and burnability than the raw meal containing clay. The use of Dross did not affect the formation of characteristic mineralogical phases.

EXPERIMENTAL DATA I
[031] The chemical analysis of clinker samples was carried out to study the various chemicals present in it. Partial blending (0.2 % to 10%) of Aluminium Dross in Raw materials as a partial replacement of clay and Mineralizer enhanced the whiteness index of White Portland Cement.

[032] This decreased the total Fe and Ti content (as seen in table) of white cement clinker for the enhancement of whiteness index of white cement. It also improved the burnability of the white cement clinker and enhanced the formation of key cement clinker phases responsible for the improvement of whiteness index of white cement clinker/white cement.

Oxides CaO SiO2 Al2O3 MgO Fe2O3 TiO2 K2O SO3 Cr2O3 P2O5 MnO
Control Clinker Sample 64.16 24.39 6.71 3.83 0.51 0.26 0.03 0.03 0.03 0.02 0.03
Clinker with Dross 64.72 22.99 8.45 3.14 0.39 0.15 0.04 0.03 0.03 0.03 0.03
Table 1
EXPERIMENTAL DATA II
[033] Repeated lab scale experiments were carried out using Aluminium Dross in Raw meal. Consistent results were observed. In all cases Hunter whiteness index of clinkers was found to increase from 88 to 94. Low iron increases the whiteness of the clinker.

Experiment Description WI Hunter:
1 Control sample prepared with regular raw materials (Limestone+ Clay + Fluorspar) 88.3
2 Clinkers prepared by Dross by partial replacement of clay (Limestone+ Clay + Aluminium Dross + Fluorspar) 94.1

EXPERIMENTAL DATA III
[034] XRD Rietveld Analysis was carried out for control sample (prepared with regular raw meal) and experimental sample (prepared with aluminium dross with raw materials), it was observed that the Alite phase (C3S) and Tri-calcium Aluminate (C3A) phases were comparatively high in experimental sample prepared with Aluminium Dross. The whiteness of cement increased with increasing content of tricalcium silicate (C3S) and aluminate.
Experiments with white cement raw Meal) Mineral Phases (XRD Rietveld Analysis of White Cement Clinker)
Alite
(C3S) Belite
(C2S) Tricalcium
Aluminate
(C3A) Calcium
Aluminoferrite
(C4AF) Free Lime
(CaO) Periclase
Control sample prepared with regular raw materials 50.10 38.03 7.26 -- 1.58 3.03
Clinkers prepared by Dross by partial replacement of clay 55.21 32.53 7.95 -- 1.42 2.89

[035] The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application thereby enabling others, skilled in the art, to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.

,CLAIMS:We Claim:

1) A method to enhance the whiteness index of a white cement comprising, partly substituting clay and mineralizer with aluminium dross during clinkerization, thereby augmenting the formation of alite and tri-calcium aluminate clinker phase.

2) The method as claimed in claim 1, wherein the amount of aluminium dross added during clinkerization is in the range of 0.2 % to 10%.

3) The method as claimed in claim 1, wherein the whiteness index of white cement is increased by 1% to 10%.

4) The method as claimed in claim 1, wherein said aluminium dross improves the burnability of the clinker for the formation of alite and tri-calcium aluminate clinker phase.

5) The method as claimed in claim 1, wherein said aluminium dross decreases formation of colour bearing phases during clinkerization.

Dated 25 March 2021
-Digitally Signed-
M. Kisoth
IN/PA-2259
Agent for the Applicant