FIELD OF THE INVENTION
The present invention relates to a method of developing an abrasion and erosion
resistant Bauxite based composition which can be cured at a low temperature.
More particularly, the present invention relates to a method of producing an
abrasion and erosion resistant Bauxite based composition for applications as
liners on coal ash slurry handling pipes in thermal power stations.
BACKGROUND OF THE INVENTION
Wear resistance of ceramics among others mainly focuses on abrasion resistance
and erosion resistance for coal and ash handling applications in thermal power
plants. In case of ash slurry transportation, both the abrasion and erosion are
involved and hence the liner component for such applications must satisfy both
these requirements. Hence the term "wear" shall henceforth imply a combination
of abrasion and erosion properties of the material in context of the instant
disclosure. The abrasion resistance of tiles in particular when used as liner is
measured by rubber lined wheel test following ASTM G-65 standard wherein the
air jet erosion resistance is measured following ASTMG-72 standard at different
impeachment angles with a default angle of 90°.

High Alumina based abrasion resistance materials are used to extend the life of
equipment or parts by lining the pipes, bends and other equipment of coal and
ash handling in power plants and other industries where the erosion is very
severe. Alumina based abrasion resistance tiles are most preferred than other
raw materials based tiles because of many advantages, which interalia include:
Negligible water absorption with high bulk density, high abrasion and erosion
resistance, low thermal expansion, high bending and compression strength, high
hardness and homogenously distributed microstructure and moderate cost
compared to costly carbide and nitride ceramics.
Generally the tiles are prepared from ceramic materials containing about 85 to
90 wt. % AI203 and balance being sintering aids or additives. The sintering aid is
typically oxides and aluminosilicate minerals which form the liquid phase during
sintering at around 1500 to 1600 °C. These products are made from calcined
alumina and aluminosilicate mineral and other additives which are mixed in dry
or wet form and spray dried if mixed in wet form and pressed into tiles and fired
at 1500 to 1600 °C to get complete densification characterized by near zero
water absorption.

As the tiles are sintered at very high temperatures i.e. from 1580-1600 °C, a high
amount of energy is consumed for processing. The process cycle involves batch
making, mixing, fabrication of shapes by hydraulic pressing, drying and high
temperature sintering. Since, this is a high alumina composition, the sintering
temperature is high in spite of undergoing liquid phase sintering since the main
raw material is relatively coarse in nature. This has been in practice in order to
avoid high cost for fine alumina powder which can be sintered at a lower
temperature. The production cost of these abrasion resistance products are
mainly attributed to energy cost of high temperature sintering and also the raw
material. Hence a cheaper raw material, bauxite has been identified which
constitutes impurities like TO2 and Fe2O3 which helps in sintering at lower
temperature.
A known process for densification of high-modulus ceramics in particular for
large scale processing is sintering of alumina powder in the presence of a
reactive liquid. For this type of sintering to occur, three criteria must be met.
First, a predetermined amount of liquid must form at the sintering temperature.
Second, the liquid phase must completely be able to wet the solid phase, and
third, the solid phase must be partially soluble in the liquid. Liquid phase
sintering is an effective densification process for most high-alumina ceramics due

to low sintering temperature and shorter sintering time. These materials contain
80 to 99 % alumina with alkaline-earth oxides, silica and other additives. At the
sintering temperature, the components react to form a liquid phase within the
compact. On cooling, the liquid may completely crystallize or remain as an
amorphous phase, depending on the cooling rate and the liquid composition.
As stated above, in the first step, the liquid formed either by a eutectic reaction
between different phases in the compact or by melting one of them, and particle
rearrangement takes places under the influence of surface tension to give a
more efficient particle packing. This rearrangement is one reason for the faster
densification in liquid phase sintering as compared to solid state sintering. In the
second step, densification proceeds by a solution of the solid material at contact
points, faster diffusion through the liquid phase, and precipitation at solid surface
sites outside the contact area. In the third step, a solid skeleton forms in which
the liquid phase will not penetrate the grain boundaries. This occurs when the
energy of the solid-state interface becomes less than twice the energy of the
solid-liquid interface. In general, the solid-solid interfacial energy decreases as
the crystallographic mis-orientation of adjacent grains decreases

The main purpose of sintering is to provide densification without grain growth.
Therefore, in many cases sintering agents are used to hinder grain boundary
mobility. Additives have been used either as a second phase forming agents or
as a solid solution in alumina ceramics for several purposes. In both the cases,
the aim is to enhance the densification and suppress the grain growth. Formation
of a liquid phase by using an agent within the body provides a rapid diffusion
pathway
to enhance densification. Additives as solid solutions not only enhance the
densification but also inhibit the grain growth by lowering the boundary mobility.
Also, they are used to accelerate sintering or shrinkage rate, to reduce firing
temperature, to change pore shape, to change the physical and chemical
properties, and to remove impurities.
US 3784388 discloses a low cost, strong, highly wear resistant ceramic articles,
the wear resistance being comparable to that of cemented carbides. The ceramic
articles are hot-pressed bauxite compositions, 78-94 percent Al2O3, less than 9
percent SiO2, 2-8 percent Fe2O3, 2-4 percent TiO2 and a total of less than 3
percent CaO, MgO, Na2O, GB1269144 discloses a ceramic containing Al2O3 78-
O3 2-8 %; TiO2 2-4 %; and a total of 0-3% impurities such as CaO, MgO and

and Na2O and a numerical average crystal size not greater than 18 µm is
obtained by milling a natural or synthetic bauxite until chemically uniform,
calcining (to remove contained water) and hot pressing a 1100-1400 °C and at
least 800 psi pressure. Before hot pressing metallic inserts or reinforcements,
e.g. screws, lugs, mesh can be inserted, and a preliminary cold forming to shape
can also be done.
GB 1155783 discloses a barrel finishing media comprising preformed and
sintered bodies consisting essentially of bauxite and finely divided fused alumina
particles. The fused alumina comprises from 10 to 80% by weight of said bodies
and the media is made by forming a mixture containing comminuted bauxite
having an average particle size of 5 µm and finely divided fused alumina together
with a small amount, e.g. between 2 and 8% of bentonite binder, then adding
water to the dry mixture to provide a plastic workable mass after which the
plastic mass is formed into bodies by shaping. The shaped bodies are then
heated to a higher temperature in the range of 1400 to 1750 °C to sinter them in
a neutral, reducing or oxidizing atmosphere; the bodies are then allowed to cool
and if desired they are tumbled with water from 15 to 30 minutes in a rotating
barrel to remove minor edge faults.

GB 578280 discloses that the lining element of a ball mill has at least the inner
wearing portion made from a solidified casting obtained from a mixture
containing from 85-98 per cent of aluminous material compound predominately
of alumina, the remainder being glass.
US 929517 teaches adding of finely ground sodalime or borosilicate glass to
comminuted pure alumina or aluminous material containing 54-98 % AI2O3, such
as bauxite, gibbsite, diaspore, laterite, corundum or emery, the mixture fused
preferably in an electric furnace. The molten material runs into a mould, which
may be insulated and preheated to form linings or lining blocks, the latter being
cemented in position. The castings produced had feather-like structure with
elongated crystals with their major axes approximately perpendicular to the face
of the casting.
GB 1563784 describes improvements in pipes and pipe elbows for conveying
materials. Pipes and pipe elbows are commonly manufactured in cast iron, and
when used for the supply of pulverized fuel to the furnaces of power stations and
on other applications where abrasives are passed through the pipes causing the
pipes and particularly the elbows to rapidly become worn and furthermore cast
iron pipes and elbows do not comply with standards as they are not contained
within a ductile material such as mild steel to withstand possible explosions.

The object of the invention was to obtain an abrasive resistant lining for a mild
steel elbow and pipe. According to the invention a pipe elbow for conveying
abrasive or corrosive material each comprise a ductile shell having a cast basalt
lining, the elbow being reinforced with impact resistant tiles grouted to the shell.
GB 2194222 discloses a tile of a wear-resistant material having two adjacent
edges 1, 2 withrear flanges 3, 4 which can overlap with complementary front
flanges 8, 9 of a similar tile so that the tiles tend to hold each other in place in
the lining. This invention is concerned with wear-resistant linings to chutes,
vessels and other items of plant. Chutes for conveying abrasive material such as
coal or coal slurry are often lined by wear resistant tiles. Each tile is individually
secured to the chute by bolts or other fixing means, but as the bolts wear it is
not uncommon for the tile to come free and be lost completely. The tile is
generally rectangular and is formed of cast steel to BS 4844, commonly known
as Ni-Hard, although it could also be cast of another hard-wearing abrasion
resistant material such as basalt or alumina.
GB 1476392 teaches an improved method of forming pipes for conveying
abrasive materials and apparatus for their manufacturing. Pipes for conveying
abrasive materials have been proposed in which a fabricated steel shell is lined
with basalt liners bonded to the shell by cement grout. However, problems have

arisen when the pipes are used for conveying ash in powerhouse and other ash
lines, due to a reaction with the grout causing a break down thereof and
corrosion within the steel pipe. The object of the invention was a method of
forming pipes or hollow members for conveying abrasive materials comprising
moulding a basalt liner, applying a glass reinforced plastics filaments to the
moulded liner. Another aspect of the invention was the method comprising
moulding a basalt liner, spraying or laying a coating of a liquid mixture of
chopped stranded glass and resin onto the basalt and consolidating the coating
on the liner with grooved rollers to provide a self-adhering shell thus producing
a basalt lined pipe or hollow member impervious to liquid.
GB 2051281 discloses a pipe bend or elbow containing a cast basalt or similar
lining, the lining being recessed over an arc of the outer periphery inside the
bend or elbow to accommodate all impact resistant tile to tiles, or the pipe wall
itself is recessed to accommodate the tile or tiles to provide a pipe having a
reinforced bed or elbow,
US 2, 350,759 describes an improvement in the transportation of finely divided
solids through curved conduits by means of gas streams. A particular aspect of
the invention relates to an Improvement in the methods of carrying out various

catalytic conversions with finely divided solid catalysts wherein the catalyst is
transported through curved conduits by gas streams. In numerous processes
finely divided solids are transported by means of gas streams through fixed
conduits usually constructed of ferrous metals. In these various cases the
conduits are subjected to more or less severe erosion and this is the cause of
considerable difficulty. This erosion is largely concentrated on certain points of
the conduits, notably on the deflecting surfaces of the bends. In many cases, this
difficulty is largely overcome by inserting hardened steel wear plates in the
bends. This is fairly satisfactory expedient in many cases, even though it is
sometimes necessary to replace the wear plates frequently. In many other cases,
however, iron is a highly undesirable impurity and is not desired in the material
transported. In these cases the use of steel wear plates is of little advantage
since the eroded steel contaminates the transported material. In these cases, it
is often necessary to line the conduit particularly at points subjected to serve
erosion with special alloys and other non-ferrous lining materials. These
developments operate satisfactorily but are generally very costly. Furthermore,
the materials available are eroded much faster than steel and require frequent
replacement.

US 3794359 teaches a tubular pipe fitting adapted to withstand abrasive and
corrosive attack in changing the direction of fluid flowing therein. The fitting is
made of a plurality of wear plates of ceramic material molded or cast to a semi-
circular shape and assembled in circumferentially spaced opposed relationship in
the area of the fitting subject to attach. Grout consisting of a mixture of epoxy
resin and metallized ceramic pellets is disposed in semi-circular form in the
circumferential space between the opposed wear plates and longitudinally of the
fitting fiber glass filaments impregnated with resin which surround the wear
plates and grout, and the entire assembly is cured to present a completed fitting.
US 3,802,893 describes a polycrystalline abrasion resistant alumina composition
consists essentially of 99.5 % - pp.9% of aluminium oxide of average particle
size in the range of 2-5 µm, 0.01- 0.25 % MgO, and 0.01-0.25 % Sm2O3 and
sintered in the temperature exceeding 1500 °C. CA 1253176 teaches a method
to develop alumina based abrasion resistant material by adding sintering agents
such as 0.5- 4.0 wt % each of TiO2 and CuO, and 0.5-4.0 wt % each of 3 or 4
oxides selected from the group consisting of Fe2O3, MnO2, ZrO2 and SiO2 to 100
parts of Al2O3 powder and then sintering the resultant raw batch in a
temperature range of 1200-1350 °C.

JP 2180747 describes a process in which magnesia and silica each having
< 0.3 µm average particle size are added to alpha-alumina powder having 0.05-
0.3 micron average particle size by 0.025-0.12 %, in total, in 2-15 molar ratio of
MgO to SiO2, they are pulverized and mixed and the mixture is moulded and
sintered at 1,300- 1,550 °C to obtain wear resistant alumina ceramics. CA
2020486 discloses a wear-resistant alumina material by liquid phase sintering a
mixture of about 70 to 95 wt % of crystalline AI2O3 particles and about
30 to 5 wt % of glass phase-forming components in a nitrogenising atmosphere
with sintering at about 1550 °C.
US 5,447,894 describes a method of sintering alumina for corrosion resistance
applications in a temperature range of 1400-1800 °C using 3-7 % additives such
as La2O3, and 0.02-0.08 % SiO2.
US 5658838 discloses a method to use TiO2, Mn3O4, SiO2 additives for sintering
alumina at 1350 °C for producing materials with low coefficient of friction for
sliding application.

Indian Patent 138068 discloses an improved additive composition useful for the
preparation of 4-5 µm alumina based abrasion resistant material having
improved wear properties when sintered in the temperature range of 1480 to
1500 °C. The process involves wet milling of 90-92% by weight of alpha alumina
with an admixture of sintering agent substantially containing SiO2, MgO, BaO,
CaO and B2O3.
CN 1673173 discloses a method of low temperature liquid-phase sintering of
bimodal alumina with nanocrystalline a-AI2O3 through wet chemical process
using MgO and Si02 as sintering aids and sintering at 1420-1500 °C for 3h.
US 6,395,214 describes high pressure and low temperature sintering of
nanophase ceramic powders using hot pressing. The inventors have shown that
under appropriate high pressure conditions, a sintered grain size can be realized
that is actually smaller than the original powder particle size.
US 6,723,674 discloses a method for developing a multi-component wear
resistant AI2O3 ceramic containing a combination of ceramic oxide additives
including rare earth ceramic oxide additive, wherein the total of the additives
comprise from about 0.1 wt % to < 50 wt % based on the total weight the
multi-component ceramic composite, and wherein all of the components are
nanostructured. JP 2009091196 describes a process in which alumina ceramic of
excellent wear resistance was prepared from 99% Al2O3 and total 0.2 % sintering
aid comprising three components Si02. CaO and MgO.

All the known arts for producing Alumina ceramics with high abrasion resistance
involve experimental data generated in the laboratory. Most of such data are not
compatible when demonstrated in large scale in the commercial production
process. Most of the patents have either used many expensive additives like
Sm2O3 or Y2O3, or used multiple additives making the process difficult to
establish a commercial scale. Many other reports highlight reduction in sintering
temperature either by using nanostructured materials or by using expensive and
difficult process like hot pressing, which are good in the laboratory scale for
generation of data but difficult to implement in large scale. Some other report
used different atmosphere for processing alumina such as in IM2, which will make
the process more expensive for the product. Therefore, these processes are not
economically viable for commercial production of alumina based abrasion
resistance products for power plant applications. Most of the commercially
available alumina based compositions are sintered at very high temperature
using one or two additives. In order to reduce the cost of raw material the
alumina can be replaced by bauxite and consequently sintering temperature can
be reduced. Bauxite is the major source of alumina and the alumina content
varies in different bauxite grades. The most of inventions reveal the use of
bauxite to produce alumina ceramics with the complicated process of hot
pressing and with the high sintering temperature of 1400 - 1750 °C. Further the
main raw material bauxite is much cheaper compared to similar grade alumina.
Therefore, the main aim of this invention is to utilize a low cost bauxite material
and with suitable additives, produce a wear resistant material, which can find
application as liner material in ash handling in Thermal power plants.

OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a method of
producing an abrasion and erosion resistant Bauxite based composition for
applications as liners on coal ash slurry handling pipes in thermal power
stations.
Another object of the invention is to propose a method of producing an abrasion
and erosion resistant Bauxite based composition for applications as liners on
coal ash slurry handling pipes in thermal power stations in which the wear
resistant ceramic composition is based on low Bauxite material with additives
which can be sintered below 1300 °C.
A still another object of the present invention is to propose a method of
producing an abrasion and erosion resistant Bauxite based composition for
applications as liners on coal ash slurry handling pipes in thermal power stations
which can be produced in mass scale-
Yet another object of the present invention is to propose a method of producing
an abrasion and erosion resistant Bauxite based composition for applications as
liners on coal ash slurry handling pipes in thermal power stations which can be
used as tiles including extruded tubes for lining purpose in ash handling
applications.

A still further object of the present invention is to propose a method of producing
an abrasion and erosion resistant Bauxite based composition for applications as
liners on coal ash slurry handling pipes in thermal power stations and
simultaneous validate the applicability by comparing the properties of the
inventive product with that of prior art wear resistant material for similar
applications.
SUMMARY OF THE INVENTION
According to the present invention, a method is disclosed for producing a low
cost bauxite based wear resistant ceramic composition (Bauxline) which can be
sintered below 1300 °C in air. The present invention also relates to the
development of ceramic tiles of the said composition which can be densified at
that temperature. Another embodiment of the present invention is to extrude the
said composition in the form of tubes and study the densification behavior of the
same. A further embodiment of the present invention is to conduct a validation
process to compare the wear properties of the inventive product with that of
prior art wear resistant products used for similar applications.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 depicts the x-ray diffraction pattern of sintered Bauxline, the major
phase identified from the pattern was alumina.
Figure 2 depicts scanning electron micrographs of sintered BAUXLINE after
polishing, chemical etching and gold coating.

DETAILED DESCRIPTION OF THE INVENTION
The present invention is focused on utilizing a naturally occurring material
Bauxite as the main source for developing a wear resistant composition. Bauxite
is the main source of alumina, but contained lot of impurities as it is mined from
earth. The composition is planned without substantially altering the known
processes and other raw materials. According to the present invention, the
known main raw materials such as Bauxite and a source of aluminosilicate are
used along with other liquid phase forming additives. The weight fraction of the
bauxite in the composition is in excess of 88 % and that of the aluminosilicate
and oxide additive is not exceeding 12 %. The bauxite chemical analysis reveals
that the alumina content in the bauxite was in the range of 75-78 %, silica in the
range of 4-5 %, ferric oxide in the range of 3-4 %, Titania in the range of 3-4%,
Calcia in the range of 2-3 %. The alumina content as estimated in the
aluminosilicate source is in the range of 5-20 %. The purity of MnO2 is more than
80%. The average particle size of the bauxite is in the range of 125-150 µm and
that of the oxide additive less than 100 µm.
The method comprises the steps of:
batch formation with pre-determined amount of raw materials, mixing the raw
materials in a high speed mixer along with an organic binder, forming shapes s
of the product in a hydraulic press, allowing natural drying, and sintering at
temperature below 1300 °C. The unintentional impurities present in the Bauxite
alongwith the additives result in liquid phase sintering of the product.

The amount of additive varies depending on the alumina content in the bauxite;
higher the alumina content, more additives or different proportion additives are
used for full densification at a particular sintering temperature. A typical high
alumina composition with average particle size of alumina >5 micron undergoes
liquid phase sintering at a sintering temperature range of 1550-1600 deg C with
typical alumina content in the range of 85-88 %. By varying the alumina content
in the range of 77-80 % with combination of additives, it is possible to density
the Bauxite based composition at a temperature as low as 1240-1260 °C. This
substantial reduction in sintering temperature leads to low cost of production of
liner components resulting lower energy cost and eventually lower product cost.
The composition thus developed can be used for fabrication of tiles by uniaxial
pressing using a multi cavity die or can be extruded in the form of tubes with
suitable binder system.
The tiles manufactured by the new composition were sintered in the temperature
range of 1230-1270 °C in a continuous kiln which resulted in homogeneous
glassy phase distribution among the pores and close binding with alumina
particles with the outcome of high density material, low water absorption and
low abrasion volume loss (AVL). The densification studies have been extended to
the tiles of different shapes such as bend, straight, triangular etc with size
varying in the range of 120-150 mm in length, 50-60 mm in width and 15-30 mm
in thickness. The batch size of final compositions were varied from 5 Kgs to
10 Kgs. and finally in 150 Kgs. batch for demonstrating the product in the

commercial kiln. The bulk density (BD) was in the range of 3.00 -310 g/cc, water
absorption (WA): 0.05-0.1 %, and Hardness: 8 as per Mohr's scale. The adjusted
volume loss as measured following ASTM G 65 standard was in the range of 12-
18 mm3. The sand erosion volume loss has also been calculated using ASTM
G-76 method and found in EV (Average erosion value) in the range of 0.44-0.46
mm3/g of AEV (Average erosion value). The presently developed material is
named as 'BAUXLINE".
By closely analyzing the composition of main raw material Bauxite, it was noted
that the presence of Titania and silica act as sintering air and enhances
densification rate. Titania is known to use as a sintering additive in alumina.
However, impurities like Fe2O3 melts at a lower temperature and results in more
glass formation in the product resulting in poor mechanical properties. Therefore,
it is essential to suitably chose the composition without any beneficiation of the
raw materials to achieve best densification of the product. The naturally made
raw materials like Bauxite though is a rich source of alumina is very cost effective
compared to the processed alumina of various particle sizes. Therefore, if the
application demands for a low cost wear resistant product such as replacement
of volcanic by product Basalt, then alumina based wear resistant product is not a
good choice rather bauxite based materials are more suitable for such
applications. Therefore, the focus of this study here is to develop a low cost
bauxite based product which can compete with currently used basalt material.
The main advantages of the new composition are: increasing the bulk density

and low abrasion volume loss with low water absorption, better microstructures
with homogeneously distributed viscous liquids among the pores along with close
binding of alumina particles. All these advantages translate into low fuel
consumption, cycle time reduction and improve the life of refractory kiln furniture
resulting in overall reduction in cost of production in commercial scale when
compared to the conventional high alumina based wear resistant products
processed at a temperature of approx. 1600 °C.
The present invention can better be explained with few suitable examples.
Example 1:
A batch consisting of bauxite of 4775 g, aluminosilicate and additive mixture of
225g was mixed manually for 15 min. followed by addition of organic binder and
mixed again for 15 min. The mixed powder was used for fabrication of bend and
straight tiles of approximate dimension 150mm L x 30 mm width and 60 mm
height. The tiles were dried and sintered in the production kiln at a sintering
temperature of 1250 °C. The firing yielded results as follows: bulk density: 3.17
g/cc, water absorption: 0.06 % and AVL in the range of 8-12 mm3.
Example 2
A batch consisting of bauxite of 4450 g, aluminosilicate and additive mixture of
550g was mixed manually for 15 min. followed by addition of organic binder and
mixed again for 15 min. The mixed powder was used for fabrication of bend and

straight tiles of approximate dimension 150mm L x 30 mm width and 60 mm
height. The tiles were dried and sintered in the production kiln at a sintering
temperature of 1250 °C. The firing yielded results as follows: bulk density: 3.11
g/cc, water absorption: 0.07-0.09 % and AVL in the range of 8-16 mm3.
Example 3
A batch consisting of bauxite of 4675 g, aluminosilicate and additive mixture of
325g was mixed manually for 15 min. followed by addition of organic binder and
mixed again for 15 min. The mixed powder was used for fabrication of bend and
straight tiles of approximate dimension 150mm L x 30 mm width and 60 mm
height. The tiles were dried and sintered in the production kiln at a sintering
temperature of 1250 °C. The firing yielded results as follows: bulk density: 3.11
g/cc, water absorption: 0.05-0.16 % and AVL in the range of 12-20 mm3.
Example 4
A batch consisting of bauxite of 1,33,550 g, aluminosilicate and additive mixture
of 16,500 g was mixed in an intensive mixer for 15 min. followed by addition of
organic binder and mixed again in the same condition for 15 min. The mixed
powder was kept for ageing for 24h prior to use for fabrication of bend and
straight tiles ofapproximate dimension 150mm L x 30 mm width and 60 mm
height. The tiles were dried and sintered in the production kiln at a sintering
temperature of 1250 °C. The firing yielded results as follows: bulk density: 3.07-
3.10 g/cc, water absorption: 0.1 %, AVL in the range of 14-18 mm3 and AEV in
the range of 0.44-0.46 mm3/g.

Example 5
A batch consisting of bauxite of 10,680 g, aluminosilicate and additive mixture of
1,320 g was mixed with 600 g of a suitable cellulose powder and are cone
blended for 2 hours. This was further mixed in the zigma mixer with water of
about 2000 ml and made into an extrudable mass. It was kept for curing in the
cold room overnight. Then the mass was mixed with 30-50 ml water and zigma
mixed and compacted in the piston extruder. The mass was extruded into long
hollow tubes of 80/60 mm diameters. The extruded tubes of 200 mm in height
were dried for 2 days in room temperature followed by oven drying and finally
fired at 1250 °C in a production kiln. The results of fired extruded tube indicated
a bulk density of 3.02-3.05 g/cc with water absorption in the range of
0.04-0.06 %. The linear shrinkage was in the range of 11-12 % after firing. The
final results obtained in this study was compared with that of Basalt, which is
presently used as liner material in ash handling applications in the power plant.
It was noted that the presently developed material Bauxline is superior than that
of basalt and hence can be used as liners in ash handling pipelines as liners in
thermal power plants.

WE CLAIM:
1. A method of producing a bauxite based abrasion resistant ceramic liner for
structures transporting coal ash slurry in thermal power stations produced
at low sintering temperature, the starting material consisting of wt. % of
bauxite >88%, an aluminosilicate and oxide additive mixture not
exceeding 12%, and manganese oxide additive of 3 % with organic
binding adhesive of 5-10% concentration, the method comprising the
steps of
a) selecting a composition with Bauxite as the main source of
alumina for imparting wear resistance;
b) dry mixing said constituting components of the starting material
in a high speed mixer to produce a moist mixture;
c) pressing the moist powder in the form of tiles of different sizes
and shapes by a hydraulic press followed by natural drying;
d) sintering the tiles in a batch kiln furnace to obtain an abrasion
'resistant tile.
2. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein a naturally occurring Bauxite is used for wear resistant tile
composition.

3. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein a complete densification of the Bauxite based composition is
achieved at a low temperature range of 1240-1260 °C in an industrial kiln.
4. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein the bauxite raw material is having particle size 125-150 µm, and
wherein the alumina content in aluminosilicate is in the range of 10-12%.
5. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein manganese dioxide is used as an additive among others in the
range of 1-4 % and in the form of high temperature flux, the MnO2%
being more than 80% pure having no particles above 100 µm.
6. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein the bulk density is 3.00-3.15 g/cc against 2.9-3.3 g/cc density for
prior based basalt and water absorption (WA) of 0.05- 0.1 % against
<0.1% for Basalt.
7. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein the produced ceramic tiles are homogenous and densed by liquid
phase sintering of the Bauxite based composition.

8. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein the produced ceramic liners possess adjusted volume loss (AVL)
in the range of 13-16, compared to ~ 100 that of mild steel as defined by
ASTM G-65 standard.
9. A method of producing ceramic liner Bauxline as claimed in claim 1, where
in the average erosion volume loss (AEV) is 0.44-0.46 mm3/g compared
to ~ >1.0 mm3/g that of prior used Basalt as measured following ASTM
standard G 76.
10. A method of producing ceramic liner Bauxline as claimed in claim 1,
wherein the produced product can be extruded in a pin type extruder as
tubes and sintered , and wherein the sintered extruded body exhibits bulk
density of 3.02-3.05 g/cc with ~ 0.04-0.06 % WA.

ABSTRACT

The invention relates to a method of producing wear resistant ceramic liner at
low sintering temperature consisting of wt. % of bauxite >88%, an
aluminosilicate and oxide additive mixture not exceeding 12%, with organic
binding adhesive of 5-10% concentration. The method comprising the steps of a)
formulating a composition of Bauxite of specific alumina content with other
additives, b) dry mixing in a high speed mixer of the said ingredients;
c) pressing the moist powder in the form of tiles of different sizes and shaping by
a hydraulic press; d) natural drying of the formed tiles; e) sintering the tiles in a
continuous kiln at 1240-1260 °C temperature to obtain an abrasion resistant tile
of bulk density 3.0-3.15 g/cc and water absorption of < 0.1%, adjusted abrasion
volume loss (AVL) of 13- 16 mm3 and average air jet erosion value (AEV) of
0.44-0.46 mm3/g with homogenous dense microstructure. The material has
potential as wear resistant low cost ceramic liner replacing the melt casted Basalt
for ash handling application in thermal power plants.