Claims:WE CLAIM:
1. A composition for preparing a brown tabular alumina aggregate, said composition comprising:
- bauxite in an amount in the range of 15 wt % to 85 wt % of the total composition;
- clay containing high amount of alumina, said clay in an amount in the range of 3 wt % to 15 wt % of the total composition;
- alumina ore in an amount in the range of 10 wt % to 75 wt % of the total composition; and
- a sintering aid in an amount in the range of 0.5 wt % to 5 wt % of the total composition;
wherein said brown tabular alumina aggregate obtained by employing said composition is characterized by having
- Los Angeles abrasion loss value in the range of 5-15%;
- Bulk density in the range of 3 g/cm3 to 4 g/cm3; and
- Apparent porosity in the range of 3-6%.
2. The composition as claimed in claim 1, wherein
- said bauxite is in an amount in the range of 45 wt % to 85 wt % of the total composition;
- said clay is in an amount in the range of 5 wt % to 10 wt % of the total composition;
- said alumina ore is in an amount in the range of 10 wt % to 50 wt % of the total composition; and
- said sintering aid is in an amount in the range of 2 wt % to 4 wt % of the total composition.
3. The composition as claimed in claim 1 or claim 2, wherein said sintering aid is at least one selected from magnesium oxide and titanium oxide.
4. A process for preparing a brown tabular alumina aggregate, said process comprising the following steps:
? providing a composition by mixing:
o bauxite in an amount in the range of 15 wt % to 85 wt % of the total composition;
o clay containing high amount of alumina, said clay in an amount in the range of 3 wt % to 15 wt % of the total composition;
o alumina ore in an amount in the range of 10 wt % to 75 wt % of the total composition; and
o a sintering aid in an amount in the range of 0.5 wt % to 5 wt % of the total composition;
? pulverizing said composition to obtain a powder, having a particle size in the range of 10 ?m to 45 ?m;
? blending said powder with a binder in an amount in the range of 1 wt % to 3 wt % of the total composition, to obtain a slurry;
? granulating said slurry to obtain green granules having a predetermined size;
? drying said green granules at a first predetermined temperature to obtain dried green granules;
? sintering said dried green granules at a second predetermined temperature and at a predetermined pressure to obtain sintered granules; and
? cooling said sintered granules to obtain the brown tabular alumina aggregate.
5. The process as claimed in claim 4, wherein said binder is aqueous polyvinyl alcohol.
6. The process as claimed in claim 4, wherein said predetermined size of said green granules is in the range of 2 mm to 30 mm, preferably in the range of 5 mm to 25 mm.
7. The process as claimed in claim 4, wherein said first predetermined temperature is in the range of 200 ?C to 400 ?C, and/or said second predetermined temperature is in the range of 1550 ?C to 1700 ?C.
8. The process as claimed in claim 4, wherein said predetermined pressure is atmospheric pressure.
9. The process as claimed in claim 4, wherein said drying is carried out for a time period in the range of 10 minutes to 60 minutes and/or said sintering is carried out for a time period in the range of 15 minutes to 120 minutes.
, Description:FIELD
The present disclosure relates to brown tabular alumina and a process for preparing the same.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which it is used indicates otherwise.
BTA: Brown tabular aluminium (BTA) is a re-crystallized sintered material containing alpha alumina phase having density in the range of 3.4 to 3.6g/cc.
High alumina clay: is an alumino-silicate clay with high content of alumina (44-49%) and comparatively low content of silica (23-28%) after calcination.
Abrasion: Abrasion is a measure of the degradation of a coarse aggregate sample. Low abrasion value indicates that the aggregate is tough and has high abrasion resistance.
Spalling: The term “spalling” refers to a process of breaking or splitting into chips or bits.
Spalling resistance: The term “spalling resistance” refers to the ability of a refractory material to maintain its true form when exposed to thermal shock.
Apparent porosity: The term “apparent porosity” refers to the volume of the open pores in the refractory material in the percentage.
Bulk density: The term “bulk density” refers to the ratio of the weight of the refractory material to its volume in g/cc.
L.A. Abrasion test: The Los Angeles (L.A.) abrasion test is a common test method used to measure aggregate toughness and abrasion characteristics.
Monolithic refractory: The term ‘monolithic refractory” refers to unshaped materials in suspension form that ultimately harden to form a solid mass.
CCS: Cold crushing strength (CCS) is the ability of a product to resist failure under compressive load at room temperature.
Casting: The term “casting” refers to the manufacturing process in which a liquid material is usually poured into a mold, containing a hollow cavity of desired shape, which is allowed to solidify.
Corrosion resistance: The term “corrosion resistance” refers to the parameter that describes the resistance to the deterioration of intrinsic properties of a material caused by reaction with a surrounding environment.
Brown Fused Alumina (BFA): The term “Brown Fused Alumina (BFA)” is both hard and tough material, produced by the smelting of calcined bauxite in an electric arc furnace at temperatures greater than 2000 oC.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Road safety is of utmost importance and hence measures are taken by concerned authorities to make the road safe for driving. One such measure is high friction surface treatment of the roads. High-friction surface treatment is done to augment the skid resistance of the road; particularly in the areas where the risk of an accident due to vehicle skidding is high. These areas can include, but are not limited to, areas in and around the traffic signals, dangerous bends, and steep inclination on the road. The surface treatment process comprises applying a resin to an existing road surface along with a high abrasion resistant aggregate. The coated resin layer grips and fixes the high abrasion resistance aggregate comprising calcined bauxite, which provides the road with anti-skidding characteristics.
A high abrasion resistance property of the calcined bauxite-based aggregate is necessary due to the high friction between the road surface and the vehicle tyres. Further, the higher abrasion resistance of the aggregate enhances the performance and life of the treated surface. The refractory aggregate plays the role of a skeleton in the manufacturing of the refractory body.
Tabular alumina prepared by the conventional technique using crude raw material has low abrasion resistance value in the range of 20-25%, high porosity in the range of 8-12% and bulk density in the range of 3-3.2g/cc. Therefore, it is not suitable for making a brown tabular alumina applicable for high friction surface treatment (HFST) purposes.
Refractories are non-metallic materials that are hard to melt at very high temperatures. They are desired to have good mechanical strength and heat resistance, and are generally classified into two different categories viz,
a. shaped refractories that are used in furnaces and kilns e.g., bricks; and
b. unshaped refractories that can form joint-less refractories to give better corrosion resistance and better life e.g., ramming masses, gunning masses, castables, mortar, fettling mix and the like.
Conventionally, tabular alumina has been used in high performance refractories for many applications in steels, ceramics, foundries, and the like. The raw materials used in the process comprise bauxite along with sintering aid and other additives. The conventional processes for manufacturing tabular alumina involve calcination of the raw material in a rotary kiln. However, the conventional processes lead to low chemical homogeneity which further leads to various defects like black spot, blotting, difference in mechanical strength among the grains, and the like.
Other properties that are of interest with reference to tabular alumina include spalling resistance and better corrosion resistance property.
There is, therefore, felt a need for a composition and a process for overcoming the above mentioned limitations.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide brown tabular alumina (BTA).
Another object of the present disclosure is to provide brown tabular alumina having high density and low porosity.
Yet another object of the present disclosure is to provide a castables obtained from brown tabular alumina having relatively higher cold crushing strength after heating and after spalling.
Still another object of the present disclosure is to provide a process for preparing brown tabular alumina having a relatively high density, low porosity, and enhanced abrasion resistance.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to brown tabular alumina with enhanced abrasion resistance, enhanced spalling resistance and corrosion resistance and a process for preparing the same.
In accordance with an aspect, the present disclosure relates to a composition for preparing a brown tabular alumina aggregate. The composition comprises bauxite in an amount in the range of 15 wt % to 85 wt % of the total composition, clay containing high amount of alumina, wherein the clay is in an amount in the range of 3 wt % to 15 wt % of the total composition, alumina ore in an amount in the range of 10 wt % to 75 wt % of the total composition, and a sintering aid in an amount in the range of 0.5 wt % to 5 wt % of the total composition, wherein the brown tabular alumina aggregate obtained by employing the composition is characterized by having a Los Angeles abrasion loss value in the range of 5-15%; a bulk density in the range of 3 g/cm3 to 4 g/cm3; and an apparent porosity in the range of 3-6%.
The sintering aid, in accordance with the present disclosure, is at least one selected from magnesium oxide and titanium oxide.
In accordance with another aspect of the present disclosure, a process for preparing a brown tabular alumina aggregate is provided. The process comprises providing a composition by mixing bauxite in an amount in the range of 15 wt % to 85 wt % of the total composition, clay containing high amount of alumina, wherein the clay in an amount in the range of 3 wt % to 15 wt % of the total composition, alumina ore in an amount in the range of 10 wt % to 75 wt % of the total composition, and a sintering aid in an amount in the range of 0.5 wt % to 5 wt % of the total composition; pulverizing the composition to obtain a powder having a particle size in the range of 10 ?m to 45 ?m, blending the powder with a binder in an amount in the range of 1 wt % to 3 wt % of the total composition, to obtain a slurry, granulating the slurry to obtain green granules having a predetermined size, drying the green granules at a first predetermined temperature to obtain dried green granules, sintering the dried green granules at a second predetermined temperature and at a predetermined pressure to obtain sintered granules, and cooling the sintered granules to obtain the brown tabular alumina aggregate.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The properties of brown tabular alumina (BTA) aggregate of the present disclosure will now be described with the help of the accompanying drawing, in which:
FIG. 1 illustrates a scanning electron microscope (SEM) image of a conventional aggregate (brown fused alumina (BFA));
FIG. 2 illustrates a scanning electron microscope (SEM) image of a brown tabular alumina aggregate prepared in accordance with an embodiment of the present disclosure;
FIG. 3 illustrates a graph of apparent porosity (AP) and bulk density (BD) of the conventional aggregate (BFA) and that of the brown tabular alumina aggregate (BTA), prepared in accordance with an embodiment of the present disclosure;
FIG. 4 illustrates a graph of particle distribution of finer and coarser raw mix of the brown tabular alumina aggregate prepared in accordance with an embodiment of the present disclosure;
FIG. 5 illustrates a graph of apparent porosity (AP) and bulk density (BD) of aggregate made of coarser and finer particles of the brown tabular alumina aggregate, prepared in accordance with an embodiment of the present disclosure;
FIG. 6a illustrates an image of the castables made up of a conventional aggregate (BFA), wherein the castables are subjected to corrosion resistance testing; and
FIG. 6b illustrates an image of the castables made up of the brown tabular alumina aggregate prepared in accordance with the present disclosure, wherein the castables are subjected to corrosion resistance testing.

DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The present disclosure overcomes one or more drawbacks associated with the conventional aggregates (BFA) and the process for manufacturing the same.
In an aspect, the present disclosure provides a composition for preparing a brown tabular alumina (BTA) aggregate, wherein the composition comprises bauxite in an amount in the range of 15 wt % to 85 wt % of the total composition, clay containing high amount of alumina, the clay in an amount in the range of 3 wt % to 15 wt % of the total composition, alumina ore in an amount in the range of 10 wt % to 75 wt % of the total composition; and a sintering aid in an amount in the range of 0.5 wt % to 5 wt % of the total composition.
The brown tabular alumina aggregate obtained by employing the above-mentioned composition is characterized by having a Los Angeles abrasion loss value in the range of 5-15%; a bulk density in the range of 3 g/cm3 to 4 g/cm3; and an apparent porosity in the range of 3-6%.
In one embodiment, in accordance with the present disclosure, the composition for preparing the brown tabular alumina aggregate comprises bauxite in an amount in the range of 15 wt % to 80 wt % of the total composition, clay containing high amount of alumina, the clay in an amount in the range of 5 wt % to 15 wt % of the total composition, alumina ore in an amount in the range of 15 wt % to 70 wt % of the total composition; and the sintering aid in an amount in the range of 1 wt % to 3 wt % of the total composition.
The sintering aid is at least one selected from magnesium oxide and titanium oxide. The sintering aid helps in reducing the sintering temperature and improves the properties of BTA.
It is observed that the strength of the aggregate depends on the porosity of the aggregate and the porosity in turn depends on the size, shape and the composition of the aggregate. It is found that the composition employed for the preparation of the brown tabular alumina aggregate along with the process employed for preparation thereof, leads to the reduced porosity and hence enhanced strength. In particular, apparent porosity is an important parameter for any aggregate. The strength of the individual grain as well as cast or body made of the BTA aggregate decreases with increasing apparent porosity. Further, the water requirement also increases with the increasing apparent porosity.
Further, the amount and distribution of closed porosity plays important role to arrest crack propagation and enhance spalling resistance of the refractory body or the cast made (castables) from the BTA aggregate. The castables prepared from the BTA aggregate of the present disclosure is characterized by having a cold crushing strength (CCS) after heating at a temperature in the range of 1100 oC to 1500 oC is in the range of 1200 Kg/cm2 to 1400 Kg/cm2; and cold crushing strength (CCS) after spalling in the range of 900 Kg/cm2 to 1300 Kg/cm2. In an exemplary embodiment, the castables prepared from the BTA aggregate of the present disclosure is characterized by having a cold crushing strength (CCS) after heating 1500 oC is 1377 Kg/cm2; and cold crushing strength (CCS) after spalling test is 1129 Kg/cm2 after 10 cycles; and 1019 Kg/cm2 after 20 cycles.
In accordance with another aspect of the present disclosure, a process for preparing a brown tabular alumina aggregate is provided. The process comprises the steps of providing a composition by mixing bauxite in an amount in the range of 15 wt % to 85 wt % of the total composition, clay containing high amount of alumina, the clay in an amount in the range of 3 wt % to 15 wt % of the total composition, alumina ore in an amount in the range of 10 wt % to 75 wt % of the total composition, and a sintering aid in an amount in the range of 0.5 wt % to 5 wt % of the total composition. The composition is pulverized to obtain a powder having a particle size in the range of 10 ?m to 45 ?m, preferably the particle size is less than 40 ?m. The pulverization is carried out using any known method such as ball milling, and the like.
The pulverization/grinding of the composition to obtain a particle size below 10 ?m is not economically viable (difficult to achieve) and the particle size more than 45 ?m (coarser size) restricts the formation of alpha alumina and particle-particle interaction between the ingredients.
It is observed that the particle size of the powder has an impact on the porosity and density of the aggregate formed. Lower the particle size, lesser is the porosity (including apparent porosity) and higher is the density. This in turn leads to improved strength and other parameters including abrasion values, cold crushing strength, and spalling resistance.
The powder so obtained is then blended with a binder to obtain slurry. The binder is in an amount in the range of 1 wt % to 3 wt % of the total composition. The binder, in one embodiment, is polyvinyl alcohol.
In the next step, the slurry is granulated to obtain green granules having a predetermined size. The slurry is granulated by employing known granulating methods and apparatus. The green granules so obtained have a predetermined size, which is in the range of 2 mm to 30 mm and preferably in the range of 5 mm to 25 mm.
The green granules are then dried by heating at a first predetermined temperature to obtain dried green granules. The first predetermined temperature is in the range of 200 ?C to 400 ?C. The drying time period is in the range of 10 minutes to 60 minutes, preferably the drying time period is in the range of 10 minutes to 20 minutes.
The drying step is important to remove the moisture or water. The drying is necessary prior to sintering because sudden evaporation of water from the matrix (in case of sintering) tends to explode the green granules and do not sustain the granular shape.
The dried green granules so obtained are then sintered at a second predetermined temperature and at a predetermined pressure to obtain sintered granules. In an embodiment, the dried green granules are sintered in a sintering furnace.
In an embodiment, the second predetermined temperature, wherein the sintering is carried out, is in the range of 1550 ?C to 1700 ?C and the predetermined pressure is atmospheric pressure. The aforestated temperature range is required to achieve the desired apparent porosity (AP) and the bulk density (BD) of the sintered green granules. The sintering temperature lower than 1550 oC may lead to un-sintered product whereas the sintering temperature higher than 1700 oC is not appropriate for the preparation of BTA aggregate. Therefore, the temperature range of 1550 ?C to 1700 ?C is optimized with extensive experimentation for obtaining desired sintered green granules.
The sintering time is in the range of 15 minutes to 120 minutes, preferably the sintering time is in the range of 15 minutes to 60 minutes.
In the next step, the sintered granules are cooled to obtain the brown tabular alumina (BTA) aggregate.
The BTA aggregate prepared by the above process is suitable for refractory application for making bricks and castables and in the high friction surface treatment (HFST) application. The additional step of grinding the raw materials into fine powder and compacting the granulation process makes the material compositionally homogenous, thus leading to uniform interaction throughout the matrix. Further, the relatively higher surface area of the fine powder enhances diffusion in sintering, resulting in uniform tabular microstructure. The abrasion resistance property of the brown tabular alumina is better due to the diffusion process during sintering.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
EXPERIMENTAL DETAILS:
Experiment 1: Process for preparing BTA aggregate
General procedure:
A predetermined amount of bauxite, alumina ore, high-alumina clay, and a sintering aid were pulverized to obtain powder, having a particle size in the range of 10 ?m (micron) to 40 ?m (micron). The powder so obtained was blended with a binder (aqueous polyvinyl alcohol) to obtain slurry. The slurry so obtained was granulated to obtain green granules having a size of 10-25 mm. The green granules were dried at a predetermined temperature and for a predetermined time period to obtain dried green granules. The dried green granules were sintered in a sintering furnace at a predetermined temperature and predetermined pressure for a predetermined time period to obtain sintered granules. The sintered granules were cooled to room temperature to obtain the brown tabular aggregate.
Three experiments were carried out employing the above-mentioned procedure. The amount of the components added, reaction parameters and the properties of the BTA aggregates formed are summarized in Table 2.
TABLE 2
S. NO. INGREDIENTS EXPERIMENT NUMBER
1 2 3
1 Bauxite (gm) 82 70 52
2 Alumina Ore (gm) 12 26 45
3 High Alumina Clay (gm) 6 4 3
4 Sintering aid_MgO (gm) 0.08 0.09 0.08
Sintering aid_TiO2 (gm) 3.60 3.40 3.20
5 Binder (Polyvinyl Alcohol) (gm) 1.1 1.3 1.6
PROPERTIES OF GRANULES
S. NO. PARAMETER 1 2 3
1 Granule size (mm) 10-25 10-25 10-25
PROCESS PARAMETERS
S. NO. PARAMETER 1 2 3
1 Drying temperature of granules (?C) 300 200 200
2 Sintering temperature (?C) 1550 1600 1600
3 Drying time (minutes) 20 20 10
4 Sintering time (minutes) 40 40 50
5 Sintering pressure (atm) 1 1 1
6 Pulverized particle size (?m) 44 37 37
PROPERTIES OF AGGREGATES
S. NO. PROPERTIES 1 2 3
1 Abrasion value (%) 8.33 8.91 9.3
2 Apparent Porosity (%) 5.10 4.40 4.11
3 Bulk Density (g/cm3) 3.40 3.5 3.5

TESTING DETAILS:
The aggregates obtained in experiments 1 to 3 were tested for measurement of various properties and compared with conventional brown fused alumina aggregates. The various values are listed in table 2 herein above and the testing details are as follows:
A. MICROSTRUCTURE COMPARISON:
FIG. 1 illustrates a scanning electron microscope (SEM) image of a conventional aggregate (BFA), whereas FIG. 2 illustrates a scanning electron microscope (SEM) image of a brown tabular alumina aggregate prepared in accordance with the embodiment of the present disclosure (experiment 3). In FIG. 2, relatively larger tabular shape corundum grains are seen which are obtained by employing the process of the present disclosure, whereas the grain size of the conventional brown fused alumina (BFA) is relatively smaller in size (FIG. 1). The relatively larger tabular shaped grains enhance the refractory properties of BTA.
B. Los Angeles (L. A.) ABRASION LOSS VALUE
Table 3 herein below lists the abrasion loss values of the conventional tabular alumina and the brown tabular alumina prepared as per experiment 3 of the present disclosure. It is evident that the abrasion loss value for the brown tabular alumina of the present disclosure is lower as compared to that of the conventional brown fused alumina.
TABLE 3
S. NO. PROPERTIES BFA BTA
1 L. A. Abrasion loss value (%) 20 - 25 8.3-9.3
BFA – Brown Fused Alumina
BTA – Brown Tabular Alumina (in accordance with the present disclosure)
C. APPARENT POROSITY AND BULK DENSITY
FIG. 3 illustrates a graph of apparent porosity (AP) and bulk density (BD) of conventional aggregate (BFA) and that of the brown tabular alumina aggregate prepared in accordance with the embodiment of the present disclosure (experiment 3). Sintering at elevated temperature makes the granules of BTA highly densified. Higher bulk density and lower apparent porosity were achieved due to process steps involved in preparing compacted green granules. These superior properties enhance the thermo-mechanical properties of the castable product.
D. EFFECT OF PARTICLE SIZE ON PHYSICAL PROPERTIES OF THE AGGREGATE
FIG. 4 illustrates a graph of particle distribution of finer and coarser raw mix of the brown tabular alumina aggregate prepared in accordance with the embodiments of the present disclosure and FIG. 5 illustrates a graph of apparent porosity (AP) and bulk density (BD) of aggregate made of coarser and finer particles of the brown tabular alumina aggregate prepared in accordance with the embodiment of the present disclosure (experiment 3).
Fine and coarse grinding was carried out individually and corresponding values has been tabulated in table 4. The most commonly used metrics when describing particle size distributions are D-Values which are the intercepts for 10%, 50%, 90% and 97% of the cumulative mass. Table 4 indicates the values of finer and coarser particle size raw mix data. Granules were made from both ground raw mix followed by drying, sintering and characterization.

TABLE 4
Sample D10 D50 D90 D97
Coarser 2.148 31.256 97.152 145.78
Finer 1.170 12.075 43.946 60.53
E. CASTABLE PROPERTIES:
A comparison of castable properties of BTA aggregates of experiment 3 of the present disclosure and conventional aggregate i.e. brown fused alumina (BFA) was made as provided in table 5.
TABLE 5
CASTABLE PROPERTIES
Castable type LOW CEMENT CASTABLE
Base raw material BFA BTA
Max grain size (mm) 5 5
Water requirement for casting (%) 5.5 5
Dry density (gm/cc) after drying at 110 °C/24 hr. 2.84 2.97
CCS (kg/cm2) after heating at 1500 °C/3 hr. 1156 1377
CCS (kg/cm2) after spalling test 10 cycles 835 1129
20 cycles 746 1019
BFA – Brown Fused Alumina
BTA – Brown Tabular Alumina (in accordance with the present disclosure)
From the above, it is evident that the water requirement of a conventionally prepared aggregate for castable cement is high due to the higher amount of apparent porosity than that of BTA of the present disclosure. The castable cement made with BTA of the present disclosure has relatively higher bulk density (BD) and displays higher cold crushing strength (CCS), highly compacted interlocking grains and less water requirement during casting. The dry density value of BTA of the present disclosure is higher than that of the conventionally prepared product indicating a high degree of compactness of the green granules which is important for deciding the target value of the fired BD with specific heating cycle. Due to uniformly distributed closed pores and difference in grain size and degree of interlocking, the reduction of CCS after thermal spalling is lesser in case of BTA of the present disclosure than that of conventional aggregates. The reduction of CCS after thermal spalling is 27.76% (10 cycles) and 35.46% (20 cycles) for the conventional product while the same is 18.01% and 26.57% for 10 and 20 cycles respectively for the BTA aggregate of the present disclosure.
F. CORROSION RESISTANCE
FIG. 6a illustrates an image of conventional aggregate made of calcined bauxite, wherein the sample of the conventional aggregate is subjected to corrosion resistance testing; and FIG. 6b illustrates an image of the brown tabular alumina aggregate prepared in accordance with the present disclosure, wherein the sample of the brown tabular alumina aggregate is subjected to corrosion resistance testing.
Corrosion resistance of BTA when compared with the conventional brown fused alumina (BFA) aggregates, shows significant low value which is tabulated in table 6. This property makes it suitable for refractory application.

TABLE 6
AGGREGATE TYPE PENETRATION DEPTH (%)
HORIZONTALLY VERTICALLY
BTA – 1
(Experiment 1) 27.72 10.69
BTA – 2
(Experiment 3) 30.33 7.82
BFA 37.50 28.58

TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of the composition and a method for producing high density tabular aggregate having comparatively higher abrasion resistance, wherein the BTA:
(i) has relatively low apparent porosity and high bulk density, thereby enhancing the spalling resistance of the refractory product;
(ii) has relatively low abrasion loss value, thereby implying high abrasion resistance; and
(iii) has relatively better corrosion resistance value compared to conventional aggregates (BFA).
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, 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.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation