FIELD OF THE INVENTION
The present invention relate to a composite lining on the abrasion prone shell walls of steel
plants and in particular to an improved composite lining system involving high alumina
ceramic liner for application in abrasion prone areas of steel plants such as the wind
leg/bend leading to wind box for desired air suction by exhauster sucking air through the
sinter bed in sintering plant. The invention ,more particularly, relates to ceramic lining of
the wind legs, specifically the end wind legs and bends where erosion is maximum, with
ceramic tiles made of dense high alumina materials having a-AI203 phase containing high
alumina in the range of 85%(min) to prevent air/gas suction leakage of exhaust ducting
below the sinter bed. The invention is further directed to laying and fixing of ceramic tiles of
preferred composition and characteristics thereof which are found to be of prime
importance to ensure prolonged lining life. Importantly, the manner of providing the
composite lining would favour achieving high abrasion resistance with ceramic tiles on wind
legs and favour a working life of over 20 months without any leakage. In view of such
extended working life resulting reduction/no leakage from the suction wind leg, the machine
speed is maintained at faster level exceeding 1.36 m/min, increased productivity of plant
and reduction in exhauster load and saving in exhauster power consumption by over 10%
and thus having wide economic application in the related field in industry.
BACKGROUND ART
It is well known in the conventional art of sinter making in steel plants for catering to BF
operation as main iron bearing agglomerated charge. Such sintering operation is carried out
in sintering machine, wherein air is sucked from below through sinter bed for burning of
coke and thus to facilitate sintering reaction. This hot air/gas generated during
sintering/burning then goes to the chimney through wind legs and wind main. Any leakage
in the system decreases sintering efficiency and machine speed resulting in loss of
production. An exhauster with adequate suction capacity is operated to maintain the desired
pressure difference for preferred air flow rate required for sintering reaction. Leakage in the
system increases load on the exhauster and consequent increase in power consumption by
exhauster motor.
Conventionally, sintering machines are provided with a large numbers of wind legs in a row,
as for example 15 wind legs are connected to a single sinter machine and there may be
about 4 such machines in a row. These wind legs are situated in one side of the machine
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and connected to respective wind boxes below the moving sinter bed of the machine. Air
containing hot gases and fine solid particles, is sucked through these wind boxes and legs to
wind main which finally escapes through chimney through cyclone. Fine sinter particles
(-10mm) suspended with the hot air/gas strikes the steel plate shell lining of wind legs.
Maximum erosion takes place in the bend portion of wind legs due to increased abrasion
and higher temperature. Out of these wind legs, maximum damage occurs in the end legs
and their lower part in wind main. Temperatures in end legs are generally in the range of
150-200°C and maximum up to 300°C. The wind leg construction material is mild steel and
the average working life of last two wind legs near finishing side of the sinter machine, is
normally about 3 months. The down time for repair/ replacement of wind legs ranges
between 16 to 32 hrs, causing serious interruption in production and shortage of feeding
down the line processes.
There has been, therefore, a persistent need to develop an improved system of erosion and
abrasion resistant durable lining for the wind legs/boxes, specifically at the end legs or the
bend portion of legs or main duct and also the exhaust main for protecting the shell wall
normally fabricated with ordinary mild steel, from erosion and or abrasion due to striking
solid particles carried along with hot air/flue gas and at high temperatures. Further, the
lining need to provide leak proof handling of air suction by selective laying procedure on
inner wall of wind legs/main, so that the exhauster is not overloaded and the power
consumption of the exhauster motor is economized. The improved lining thus would be able
to operate for longer life without repair/replacement, reducing down time and thereby
increasing the productivity of the sinter plant.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for an improved abrasion
resistant inner walls of wind legs/boxes/mains of suction line of the sinter machines, to
ensure leakage free suction by exhauster and provide protection from erosion and abrasion
due to the hot air carrying erosive chemicals/gases and hot sinter particles impinging on the
shell wall made of mild steel, by selective disposition of the lining.
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A further object of the present invention is directed to provision of ceramic tiles of selective
composition and properties for desired erosion/abrasion resistive leak proof lining on the
wind legs/boxes and exhaust main at selective damage prone locations.
A still further object of the present invention is directed to selective laying arrangement of
the ceramic tiles such that longer life of the lining is ensured without leakage or
reair/replacement or any interruption of operation and thus increasing the productivity of
the sinter machines in large steel plants.
A still further object of the present invention is directed to selective laying of the ceramic
tiles on wind legs/bends or suction main, wherein the leakproof laying of tiles reduces the
exhauster load and power consumption.
A still further object of the present invention is directed to selective laying of the ceramic
tiles wherein the end wind legs and their lower part to wind main, subjected to maximum
erosion due to abrasive action of fine particle containing gases at high temperature, are
lined with dense high alumina materials having a-AI203 phase containing high alumina
ceramic tiles adapted to prevent air/gas suction leakage and erosion of exhaust ducting.
A still further object of the present invention is directed to selective laying of the ceramic
tiles wherein the bend portion of end wind legs subjected to high abrasion are lined with
high alumina ceramic tiles having 85%(min) Al203 to provide longer lining operating life.
A still further object of the present invention is directed to selective laying of the ceramic
tiles to favour obtaining the desired composite lining system involving improved abrasion
resistant charcateristics.
A still further object of the present invention is directed to selective laying of the ceramic
tiles wherein the laying pattern of the tiles ensure protection of shell/duct wall for wind
suction created by the exhauster fan with motor and prevent leakage of air such that the
speed of the sinter machine could be maintained as high as 1.36 m/min, reduce exhauster
load and save power consumption by over 10%.
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SUMMARY OF THE INVENTION
Thus according to the basic aspect of the invention there is provided a composite lining
system for abrasion prone areas of steel plant comprising:
dense High alumina material having a-AI203 phase containing high alumina ceramic
tiles having atleast 85% Al203.
A further aspect of the present invention directed to a composite lining system wherein said
ceramic tiles have following properties:
Bulk density (gms/cm3) in the range of 3.2-3.4;
Water absorption (%) 1.0 (max.);
Hardness in Moh scale : more than 8;
Flexural Strength (Kg/cm2) 2200 ( min.)and
Cold crushing strength (kg/cm2) 3000 (min).
A still further aspect of the present invention directed to a composite lining system wherein
said ceramic tiles are adapted for fixing over steel shell.
According to another important aspect of the present invention directed to said
composite lining system comprising each said ceramic tile having a tapered hole at the
center accommodating a tapered metallic ring with the inside of said metallic ring being
filled with welding, a ceramic spacer pasted over said welding area for protection.
A still further aspect of the present invention directed to said process for the
manufacture of a composite lining system comprising:
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selectively providing the dense High alumina material having a-AI203 phase
containing high alumina ceramic tiles having atleast 85% Al203 in the
abrasion prone areas of steel plant.
A still further aspect of the present invention directed to a process for the manufacture
of a composite lining system comprising:
providing said high alumina ceramic tiles with said tapered hole in the center;
initially fixing the said tiles with the metal shell of said steel plant by silicon
paste and drying the silicon paste ;
inserting the metal ring in each tile and filling hole inside the metal ring by
welding;
pasting a ceramic spacer over the weld area for protection, wherein each tile
*
was welded with the metal shell with said silicon paste driven away due to
high temperature.
According to a preferred aspect of the present invention directed to said process for the
manufacture of a composite lining system, Wind legs in steel plants/ sintering machines
comprising abrasion and temperature resistant lining comprising:
atleast in the abrasion prone area composite lining system comprising
dense High alumina material having a-AI203 phase containing high alumina ceramic
tiles having atleast 85% Al203 preferably each said ceramic tile in the lining having a
tapered hole at the center accommodating a tapered metallic ring with the inside of
said metallic ring being filled with welding, a ceramic spacer pasted over said welding
area for protection.
6

A still further aspect of the present invention directed to Wind legs in steel plants/ sintering
machines wherein the said high alumina ceramic tiles are provided in the end legs and lower
part of the main wind pipe especially the bend portion of wind leg.
According to yet another aspect of the present invention Wind legs in steel plants/ sintering
machines wherein the ceramic tiles are fixed over steel shell.
The present invention and its objects and advantages are described in greater details with
reference to the accompanying non limiting illustrative figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the illustration of the bend portion of wind leg where high alumina (85% min)
ceramic lining is installed, according to the present invention.
Figure 2: is the illustration of the schematic diagram showing arrangement of fixing of
ceramic tiles on wind leg casing by selective application of silicon paste, plug welding and
fixing of ceramic spacer over welding, according to the present invention.
Figure 3: is the illustration of lining with laid down ceramic tiles inside the wind leg, free of
any leakage, according to the invention.
DETAILED DESCRIPTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
As already described, sintering machines in steel plants comprise numerous wind legs that
are situated in one side of the machine and connected to respective wind boxes below the
moving sinter bed of the machine. Air is sucked through these wind boxes and legs and hot
air then flows through wind main and finally escapes through chimney through cyclone. Air
is sucked through the sinter bed for supply of required air for combustion of coke and thus
7

facilitating sintering reactions at desired rate. An exhauster of required capacity is provided
to maintain desired draft/maintain pressure difference. Because of suction through burning
sinter bed, fine sinter particles (-10mm) carried along with the hot air strikes the steel plate
lining of wind legs. As a result maximum erosion takes place in the bend portion of wind
legs due to abrasion at high temperature. Out of the 15 wind legs normally existing in a
sinter machine, maximum damage occurs in the end legs and their lower part in wind main.
Temperatures in end legs are generally in the range of 150-200°C and maximum up to
300°C. The wind legs are made from mild steel and the life of last two wind legs affected
most, is about 3 months. The down time for repair/ replacement of wind legs is between 16
to 32 hrs.
In order to improve the life of wind legs and critical areas of wind main, an improved
ceramic lining has been developed. As the erosion is maximum in end wind legs, high
abrasion ceramic tiles were used in bend portion of wind legs. Usually, hard materials are
ranked according to Moh's scale from 1 to 10. Hardest mineral available naturally, is
diamond, having hardness of 10 and the softest material is talc, having hardness of 1. The
second hardest mineral in nature is Corundum i.e. a-AI203. Hence, dense high alumina
material having a-AI203 phase containing high alumina ceramic tiles were used in wind leg to
prevent leakage and High alumina ceramic tiles having 85% (min) Al203, having about 15
times higher abrasion resistance than mild steel are used for lining in the bend portion of
end wind legs of sinter machine. Reference is thus invited to Figure 1, that illustrates the
bend portion of wind leg on which high alumina ceramic tiles having 85%(min) Al203 is
installed.
The erosion and abrasion resistive properties of the high alumina ceramic tiles are given in
the following Table 1 and Table 2.
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Table-1 : Properties of ceramic tiles

Properties Specification Test results
Al203 (wt.%) 85,min 90.15 - 90.48
Bulk density (gms/cm3) 3.2-3.4 3.45, 3.45, 3.45, 3.45,
3.45 (Avg. = 3.45)
Water absorption (%) 1.0, max 0.029 - 0.042
Hardness in Moh scale More than 8 >8
Flexural strength (kg/cm2) 2200, min 2299, 2544, 2888,2513
(Avg. =2561)
Cold crushing strength(kg/cm2) 3000, min 8029, 7640, 8704, 9693
(Avg.=8517)
Table -2 : Results of wear test by rotating wheel method with 5kg sand

Sample
No. Initial
wt. (gm) Final wt.
(gm) Sand wt.
(gm) Wt.
Loss
(gm) Bulk
density
(g/cc) Vol. Loss
(mm3) Relative
Abrasion
Index
Sample: Ceramic tile material
1 47.7431 47.7095 5322 0.0336 3.45 9.7391 15.68
2 49.1828 49.1493 5326 0.0335 9.7101 15.12
3 46.9452 46.9134 5346 0.0318 9.2174 14.03
4 48.1514 48.1217 5265 0.0297 8.6087 20.13
5 47.3471 47.3151 5215 0.0320 9.2754 15.92
Sample: Mild steel
6 69.8705 68.6720 5117 1.1985 7.85 152.6720 1
7 69.8243 68.6721 5138 1.1522 146.7770 1
8 69.9172 68.9019 5174 1.0153 129.3380 1
9 70.0320 68.6716 5276 1.3604 173.2990 1
10 68.8975 67.7386 5286 1.1589 147.6310 1
Reference is next invited to accompanying Figure 2, that illustrate the method of laying or
fixing the high alumina ceramic tiles. The high alumina ceramic tiles with high abrasion
resistance are fixed over steel shell/casing of the wind legs/box. The shell designing, fixing
mechanism and installation of tiles are very important to achieve maximum performance.
Tiles are initially fixed with the metal shell by silicon paste layer of thickness of 1mm
approx. Each of the Ceramic tiles of 20mm thickness and appropriate cross section were
9

laid inside the wind leg. Each tile had a tapered hole of 16.5 /14 mm in diameter at the
centre. After drying of silicon paste, metal rings were inserted in each tile and the hole
inside the metal ring was filled by welding. Inside this hole a tapered metallic ring of 2.5mm
thickness and 16/13.5 mm diameter and 12mm height was inserted. After welding, a
ceramic spacer was pasted over the welded area for protection. Each tile was thus plug
welded with the metal shell, eliminating any scope of being displaced or removed while in
service leaving chance of leakage. Silicon paste being an organic material , goes away at
high temperature and is used for initial setting of tiles only. Welding with the metal shell
keeps the ceramic tile in position during operating condition.
The accompanying Figure 3, illustrates laid down pattern of ceramic tiles inside the wind
leg of sinter machine following steps in the preceding paragraph. High abrasion resistance
ceramic tiles are lined in wind legs following selective method to provide longer service life
of over 20 months without any leakage, so that the sinter machine operating speed is
higher than convention, ranging to about 1.36m/min and the productivity in sinter machine
is improved. Further, the exhauster load is reduced (190Amp) as compared to load under
leakage condition (230Amp) such that the exhauster power consumption is reduced by over
10%.
It is thus possible by way of this invention to provide a high alumina(85% min) ceramic tile
lining and dense high alumina material having a-AI203 phase containing high alumina
ceramic tiles for inner wall of the wind legs of exhaust duct for the sinter machine, for
favored prevention of any leakage for sustained period and enhanced operating life and
thereby ensure higher sinter machine speed and productivity and lower load and power
consumption by the exhauster motor, making the invention capable being widely applied in
allied field in the large integrated steel plants.
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We Claim:
1. A composite lining system for abrasion prone areas of steel plant comprising:
dense High alumina material having a-AI203 phase containing high alumina ceramic
tiles having atleast 85% Ai203.
2. A composite lining system as claimed in claim 1 wherein said ceramic tiles have
following properties:
Bulk density (gms/cm3) in the range of 3.2-3.4;
Water absorption (%) 1.0 (max.);
Hardness in Moh scale : more than 8;
Flexural Strength (Kg/cm2) 2200 ( min.)and
Cold crushing strength (kg/cm2) 3000 (min).
3. A composite lining system as claimed in anyone of claims 1 or 2 wherein said
ceramic tiles are adapted for fixing over steel shell.
4. A composite lining system as claimed in anyone of claims 1 to 3 comprising each said
ceramic tile having a tapered hole at the center accommodating a taperea metallic
ring with the inside of said metallic ring being filled with welding, a ceramic spacer
pasted over said welding area for protection.
5. A process for the manufacture of a composite lining system as claimed in anyone of
claims 1 to 4 comprising:
selectively providing the dense High alumina material having a-AI203 phase
containing high alumina ceramic tiles having atleast 85% Al203 in the
abrasion prone areas of steel plant.
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6. A process for the manufacture of a composite lining system as claimed in claim 5
comprising:
providing said high alumina ceramic tiles with said tapered hole in the center;
initially fixing the said tiles with the metal shell of said steel plant by silicon
paste and drying the silicon paste ;
inserting the metal ring in each tile and filling hole inside the metal ring by
welding;
pasting a ceramic spacer over the weld area for protection, wherein each tile
was welded with the metal shell with said silicon paste driven away due to
high temperature.
7. Wind legs in steel plants/ sintering machines comprising abrasion and temperature
resistant lining comprising:
atleast in the abrasion prone area composite lining system comprising
dense High alumina material having a-AI203 phase containing high alumina ceramic
tiles having atleast 85% Al203 preferably each said each said ceramic tile in the lining
having a tapered hole at the center accommodating a tapered metallic ring with the
inside of said metallic ring being filled with welding, a ceramic spacer pasted over
said welding area for protection.
8. Wind legs in steel plants/ sintering machines as claimed in claim 7 wherein the said
high alumina ceramic tiles are provided in the end legs and lower part of the main
wind pipe especially the bend portion of wind leg.
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9. Wind legs in steel plants/ sintering machines as claimed in anyone of claims 7 or 8
wherein the ceramic tiles are fixed over steel shell.
10. A composite lining system for abrasion prone areas of steel plant substantially as
hereindescribed and illustrated with reference to the accompanying figures.


Dated this 7th day of February, 2007.

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A composite lining system on the shell walls of the abrasion prone areas of steel
plant/equipments such as wind leg/bend leading to wind box for desired air suction in
sintering plant. The composite lining of the end wind legs and bends, where
erosion/abrasion is maximum, provided with ceramic tiles made of dense high alumina
materials having a-AI2O3 phase containing high alumina in the range of 85%(min) to
prevent air/gas suction leakage. The laying and fixing of ceramic tiles involves tiles of
appropriate cross-section laid on inside metal shell wall, initially fixed in position with silicon
paste and allowed to dry; tapered metallic rings then fixed through tapered holes provided
at the center of each tile, which is finally plug welded with the shell wall, ensuring providing
working life of over 20 months without any leakage, as against 3 months before the
invention. As a result, faster speed of sinter machine exceeding 1.36 m/min and increased
productivity with reduction in exhauster load and power consumption by over 10% is
achieved and thus having wide economic application in the related field in industry.
Figure 2.