AN IMPROVED STOVE FOR BLAST FURNACES AND A METHOD OF FABRICATING THE
SAME
FIELD OF THE INVENTION
The present invention, in general relates to hot blast stoves for blast furnaces and in
particular to an improved top fired stove for blast furnaces and a method of fabricating the
same, whereby higher blast temperature in the vicinity of 1250°C is achieved and also
reduction in coke rate and alternate fuel injunction (coal/tar/oxygen), at higher rates, are
facilitated.
BACK GROUND OF THE INVENTION
Traditionally, hot blast stoves for blast furnaces included internal combustion chamber
having horizontal mechanical burner design and there existed a partition wall, between the
combustion chamber and checker chamber. These hot blast stoves had the vital
disadvantage of direct impingement of flame over the combustion chamber wall, resulting in
deformation and in extreme cases, even collapse of the combustion chamber lining.
Subsequently, hot blast stove with internal combustion chamber and ceramic burner were
designed, having a partition wall between combustion chamber and checker chamber. In this
design, ceramic burner, expansion joints and metallic partition wall jacket were introduced,
to sort out the problems in the aforesaid design. However, this design had certain limitations
with respect to high temperature stress corrosion, particularly in dome area.
Furthermore, in general, in the aforesaid two designs of hot blast stove, inherent design
deficiencies cropped up, due to the layout of combustion chamber and checker chamber side
by side and being separated by a common combustion chamber wall. Due to operation of
these two zones at significantly different thermal conditions, the following major drawbacks
were encountered:
i) During operation of hot blast stoves, leakage of gases between combustion chamber and
checker chamber used to take place due to developing of cracks and bricks joints in the
partition wall. This resulted in lowering of hot blast temperature.
ii) Due to different temperature conditions at either sides of the partition wall, buckling of
the combustion chamber towards the checker work, used to take place. This effect,
commonly known as 'Banana' effect, used to affect the performance as well as refractory
stability of the combustion zone and checker zone.
Having encountered the aforesaid problems in hot blast stoves with internal combustion
chamber, hot blast stoves with external combustion chamber were designed. Such design
was able to overcome the aforesaid problems, however, it was found that designing this sort
of stove was highly expensive and required larger space for installation. Hence, hot blast
stoves with external combustion chamber were, in general not found to be perfect in all
respects, particularly while applying on brown field projects.
Hence, research was on over the years to overcome the aforesaid problems and Dr. Kalugin
of Russia introduced the concept of "Top Fired Stoves" which did not have combustion
chambers or such rigorous domes as before. This design was able to sort out majority of the
disadvantages, as described hereinbefore, however, apart from being very expensive, stoves
having such design used smaller checker hole and thereby required gas cleanliness of high
order. Ensuring such high gas cleanliness, required state of the art gas cleaning system not
prevalent/available, in majority of Indian blast furnaces.
Accordingly, there was a long felt need to design a blast furnace stove which is reasonably
cheap, requires moderate gas cleanliness, requires less installation space, is capable of

achieving higher blast temperature in the vicinity of 1250°C and also avoids the other
disadvantages such as buckling of combustion chamber towards checker work, direct
impingement of burner flame over the combustion chamber wall, gas leakage problems and
deformation/collapse of combustion chamber lining.
The present invention meets the aforesaid long felt need.
All through out the specification, the words "stove", "blast furnace", "Top-fired" are to be
interpreted in the broadest sense of the respective terms and includes similar items referred to by
other terms as may be known to persons skilled in the art, and restriction/limitation, if any,
referred to in the specification, is solely by way of example and understanding the present
invention and not by way of any sort of limitation/restriction.
OBJECTS OF THE INVENTION
It is a principal object of the present invention to provide a hot blast stove having an
improved design which is reasonably cheap and is capable of achieving higher blast
temperature in the vicinity of 1250°C.
It is yet another object of the present invention to provide a hot blast stove having an
improved design which is reasonably cheap, requires less installation space and requires
moderate gas cleanliness.
It is yet another object of the present invention to provide a hot blast stove having an
improved design whereby the buckling of combustion chamber towards checker work, direct
impingement of burner flame over the combustion chamber wall and gas leakage problems
are nullified.
It is yet another object of the present invention to provide a hot blast stove having an
improved design whereby deformation/collapse of combustion chamber lining is eliminated.
It is a further object of the present invention to provide a hot blast stove having an improved
design which is suitable for both green field projects as well as brown field projects.
It is yet another object of the present invention to provide a hot blast stove having an
improved design which increases hot blast stove campaign life, facilitates saving through
reduction in coke rate and ensures alternate fuel injection(coal/tar/oxygen) possible at
higher rates.
It is a further object of the present invention to provide a hot blast stove having an improved
design which is applicable on blast furnaces of sizes ranging from 157m3 to 1700m3.
It is a further object of the present invention to provide a hot blast stove provided with
burner at the top of the hot stove, popularly known as "top fired stove", which does not have
combustion chamber and a rigorous dome.
It is yet another object of the present invention to provide a method of fabricating a hot
blast stove having an improved design which is reasonably cheap and is capable of achieving
higher blast temperature in the vicinity of 1250°C.
How the foregoing objects are achieved and the other aspects of the present invention will
be clear from the following description which is purely by way of understanding and not by
way of any sort of limitation.
SUMMARY OF THE INVENTION
Accordingly the present invention provides an improved stove for blast furnaces including a
minor dome, at least one each of a burner chamber, a conical portion, a checker chamber
wall, blast furnace gas and combustion air system, cold blast and hot blast system, waste

gas main and chimney system along with valves and controls all operatively connected to
each other, wherein the burner(s) is(are) provided at the top of the stove and said stove is
top fired with welded material and lining made up of indigenous ingredients such as herein
described, whereby said stove is reasonably cheap, requires moderate gas cleanliness,
requires less installation space and is adapted to achieve high blast furnace temperatures in
the vicinity of 1250°C.
In accordance with preferred embodiments of the stove according to the present invention:
-said stove is top fired with welded steel construction lined with silica and alumina
refractories and there exists hot blast outlet beneath said conical portion, waste gas branch
and cold blast main beneath said checker chamber wall, all having lining such as herein
described.
-the upper part of said checker chamber wall has the following layers, from the inner side to
the outer side: 305mm silica bricks(21), 5mm expanded polystyrene at the boundary of the
former(19), 114mm insulation bricks (Type-II)(20), 114mm insulation bricks (Type-IV)(ll),
75mm insulation bricks (Type-IV)(18), 40mm insulation slab(17), 1mm oil paper(5) in the
114mm insulation bricks (Type-IV) layer(ll), 75mm insulation bricks (Type-IV) layer(18)
and 40mm insulation slab(17), Ceramic wool(22) , middle part of said checker chamber
wall has the following layers from the inner side to the outer side : 230mm 62% Alumina
bricks (25), 114mm insulation bricks(Type-IV)(ll), 75mm insulation bricks (Type-IV)(18),
shell of hot blast stove(23), lower part of said checker chamber wall has the following
layers from the inner side to the outer side : 230mm 45% Alumina bricks(13), 5mm
expanded polystyrene(19), 114mm insulation bricks(Type-III)(24), 75mm insulation
bricks(Type-IV)(18), 1mm oil paper(5) in the 75mm insulation bricks(Type-IV) layer(18)
and 40mm insulation slab layer(17).
-checker chamber hole is designed to have an optimum diameter, such as in the vicinity of
40mm to reduce clogging during operation and checkers used in the checker chamber are of
hexagonal shape with a system dimension of 124 mm having twelve numbers of 40mm
diameter hole.
-said conical portion of the stove exists between said burner chamber and said checker
chamber, the hot face of said portion consists of silica bricks backed by four insulating layers
and the fourth layer is 40mm thick slab against 35% gunning castable.
-said dome is of hemispherical shape for better stability at high temperature and consists of
two layers of high alumina refractory bricks(62% Alumina/45% Alumina) backed by three
layers of insulation, 35%Alumina gunning castable and insulation slab.
-said burner chamber is equipped with blast furnace gas inlet and combustion air inlet having
the following layers from the inner side to the outer side in that order-114mm 45% Alumina
Bricks(3), 25mm insulation slab(4), lmmoil paper(5), and said burner is of ceramic origin
constructed with the combination of 62% and 45% Alumina bricks, the latter being backed
up with SS steel, insulation slab and 35% Alumina gunning castable.
-said valves and the recommended sizes and drives thereof are such as herein described, the
sizing of the various openings provided in the stove shell are selected on the basis of
maximum operating/working conditions likely to occur during stove operation and there are
provided suitable platforms at various elevations with climbing means for easy operation
and maintenance.
The present invention also provides an improved stove system comprising a battery of at
least three stoves as described hereinabove, operatively connected to each other and to a

programme logic controller(PLC) for automatic control stove mechanisms and for remote
manual operation of stove mechanisms through human machine interface(HMI) station.
The present invention also provides a method of fabricating an improved stove for blast
furnaces including operatively connecting a minor dome, at least one each of a burner
chamber, a conical portion, a checker chamber wall, blast furnace gas and combustion air
system, cold blast and hot blast system, waste gas main and chimney system along with
valves and controls , wherein said method further comprises installing the burner(s) at the
top of the stove and top firing said stove with welded material and lining made up of
indigenous ingredients such as herein described.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature and scope of the present invention will be better understood from the
accompanying drawings, which are by way of illustration of some preferred embodiments
and not by way of any sort of limitation. In the accompanying drawings:
Figure 1 illustrates a preferred embodiment of the hot blast stove in accordance with the
present invention.
Figure 2 illustrates an enlarged view of the dome, burner chamber and conical chamber of
the hot blast stove in accordance with the present invention.
Figure 3 illustrates an enlarged view of the upper, middle and lower part of the checker
chamber wall of the hot blast stove, in accordance with the present invention.
Figure 4 illustrates an enlarged view of the exhaust chamber of the hot blast stove according
to the present invention and its cross-sectional view along the line X-X.
DETAILED DESCRIPTION OF THE INVENTION
The following describes some preferred embodiments of the present invention, which are
purely for the sake of understanding the performance of the invention, and not by way of
any sort of limitation.
As stated before, hot blast stoves known in the art encountered some vital disadvantages
such as being very expensive, requirement for large insatallation space, incapability of
achieving higher blast temperature in the vicinity of 1250°C, buckling of combustion
chamber towards checker work, direct impingement of burner flame over the combustion
chamber wall, gas leakage problems and deformation/collapse of combustion chamber lining.
The present invention provides a hot blast stove for blast furnaces, which provides an
optimum solution to the problems, hitherto encountered in the art.
The hot blast stove in accordance with the present invention includes burner at the top of the
hot stove. There are no combustion chamber and a rigorous dome. This stove is fabricated
applying indigenous material and is much cheaper. That apart, due to its design it requires
moderate gas cleanliness, requires less installation space and is capable of achieving very
high blast temperature, in the vicinity of 1250°C. This achievement of very high blast
temperature, ensures saving through reduction in coke rate and also makes possible,
alternate fuel injection(coal/tar/02) at higher rates. Furthermore, the design according to
the present invention eliminates problems such as the buckling of combustion chamber
towards checker work, direct impingement of burner flame over the combustion chamber
wall, gas leakage problems, deformation and collapse of combustion chamber lining. The
stove in accordance with the present invention is suitable for installation in green field area
as well as brown field area, for a blast furnace having a useful volume capacity of 262m3.

According to a preferred embodiment and as illustrated in the accompanying figure 1, the
hot blast stove of the present invention includes a minor dome (A), a burner chamber (B), a
conical portion (C), a checker chamber wall (D) and an exhaust chamber. On one flank of
the burner chamber, there exists blast furnace gas inlet (E) and combustion air inlet (F).
There also exists hot blast outlet, just beneath the conical section and immediately above
the checker chamber wall. The checker hole of the hot blast stove, in accordance with the
present invention is selected to have an optimum diameter, say 40mm to ensure that holes
are not clogged during operation.
As shown in the accompanying figure 2, the lining of dome, burner chamber and conical
section comprises the following:
1. Dome has the following layers from inner side to outer side in that order. 345mm 62%
Alumina bricks(14), 230mm 45%Alumina bricks(13), 230mm insulation bricks(Type-I)(12),
114mm insulation bricks(Type-IV)(ll),lmm oil paper(5), 75mm IE quality insulation
bricks(lO). The boundaries between the various layers comprises, 25mm ceramic fibre
blank(6) , 13mm ceramic blanket(7), 6mm ceramic felt(9), 25mm insulation slab(4), 50mm,
35 % Alumina Gunning Castable(8). The central portion of dome comprises ceramic wool (2)
and standard 75 bricks to be filled without mortar(l).
2. Burner chamber has the following layers from inner side to outer side in that order-
345mm 62% Alumina bricks(14), 5mm ceramic felt(27), 230mm 45% Alumina bricks, 3mm
SS sheet, 230mm 45% Alumina bricks(13), 5mm ceramic felt(27), 25mm insulation slab(4),
50mm 35% Alumina Gunning Castable(8).
At the distal end of the burner chamber, there is a peep hole and flame sensor (16).
3. Blast furnace gas inlet and combustion air inlet have the following layers from the inner
side to the outer side in that order-114mm 45% Alumina Bricks(3), 25mm insulation slab(4),
lmmoil paper(5).
4.Conical portion has the following layers from the inner side to the outer side in that order :
305mm silica bricks(21), 114mm insulation bricks(Type-II)(20), 114mm insulation bricks
(Type-IV)(ll), 5mm expanded polystyrene(19), 40mm insulation slab(17), 75mm insulation
bricks(Type-IV)(18), 1mm oil paper between the boundaries of the layers(5), 40mm
insulation slab(17), followed by 50mm, 35% Alumina Gunning Castable(8).
5. There is a symmetrical disposition of layers about the hot blast outlet. The layers from the
inner side to the outer side, comprise the following in that order: 152mm 62% Alumina
bricks (28), 114mm insulation bricks (Type-I)(29), 152mm insulation bricks(Type-IV)(30),
25mm insulation slab(4). 1mm thick oil paper (5) exists at the boundary between 114mm
insulation bricks (Type-I)(29) and 152mm insulation bricks(Type-IV)(30). 5mm thick
ceramic felt(27), exists at the boundary between 152mm 62% Alumina bricks(28) and
114mm insulation bricks(Type-I)(29).
The checker chamber wall has been lucidly illustrated in the accompanying figure 3, which is
an enlarged version.
6. The upper part of the checker chamber wall has the following layers, from the inner side
to the outer side: 305mm silica bricks(21), 5mm expanded polystyrene at the boundary of
the former(19), 114mm insulation bricks (Type-II)(20), 114mm insulation bricks (Type-
IV)(11), 75mm insulation bricks (Type-IV)(18), 40mm insulation slab(17), 1mm oil paper(5)
in the 114mm insulation bricks (Type-IV) layer(ll), 75mm insulation bricks (Type-IV)
layer(18) and 40mm insulation slab(17). Ceramic wool (22) exists at the boundary of the
upper part of checker chamber wall.

7.Middle part of the checker chamber wall has the following layers from the inner side to the
outer side : 230mm 62% Alumina bricks (25), 114mm insulation bricks(Type-IV)(ll), 75mm
insulation bricks (Type-IV)(18), shell of hot blast stove(23).
8. Lower part of checker chamber wall has the following layers from the inner side to the
outer side : 230mm 45% Alumina bricks(13), 5mm expanded polystyrene(19), 114mm
insulation bricks(Type-III)(24), 75mm insulation bricks(Type-IV)(18), 1mm oil paper(5) in
the 75mm insulation bricks(Type-IV) layer(18) and 40mm insulation slab layer(17).
As shown in the accompanying figure 4, exhaust chamber has three main components,
namely waste gas branch, manhole and cold blast main. This is further elaborated in the
cross sectional view along the line X-X.
The waste gas branch, basically comprises the following from the inner side to the outer
side-114mm 45% Alumina bricks(3), 25mm insulation slab(4), 1mm oil paper(5).
As can be seen from the cross-sectional view in the accompanying figure 4, along the line X-
X, the exhaust chamber in general has the following layers from the inner side to the outer
side : 230mm 45% Alumina bricks(13)-per ring 135 pieces), 5mm expanded
polystyrene(190, 114mm insulation bricks(Type-III)(24)-per ring 213 pieces per ring, 75mm
insulation bricks(Type-IV)(18)- per ring 145 pieces, 40mm insulation slab(17).
The method of fabricating the improved stove for blast furnaces, according to the present
invention, includes forming the various components, applying indigenous material, as
discussed before and operatively connecting the components such that the burner is placed
at the top of the stove, whereby the stove obtained is reasonably cheap, requires lesser
installation space and is capable of achieving higher blast temperature, in the vicinity of
1250°C.
The battery of stoves may comprise of three stoves to supply hot blast at temperature of
approximately 1250°C for maximum blast volume of around 45000 Nm3/h. This temperature
is achieved by providing a surface area of 92 m2/m3 of useful furnace volumeand a dome
temperature of 1450 °C. The stove is of top fired with welded steel construction, lined with
silica and alumina refractory. The stoves system consists of blast furnace gas and
combustion air system along with top ceramic burners, cold blast and hot blast system,
waste gas main and chimney system along with valves and controls.



In the event of non- availability of rich gas, waste gas preheating system shall be provided.
Refractory configuration of the stove in accordance with the present invention has been
described previously with reference to the accompanying figures 2 to 4. The salient features
of the construction of refractories for different area, are as described below.

There are two parts of Checker Chamber from bottom to top. Bottom part of Checker
Chamber consists of four layers. The hot face consists of High Alumina dense bricks (45 %
Alumina/62 % Alumina) and is backed by three insulating layers. The third layer is of 40 mm
thick slab insulation against the shell of stove. Top part of Checker Chamber consists of 5
layers. The hot face consists of Silica bricks backed by four layers of insulating layers. The
fourth layer is of 40mm thick slab insulation against the shell of stove.
Checkers used in the checker chamber, as a preferred embodiment, is of hexagonal shape
with a system dimension of 124 mm having 12 nos. of 40 mm diameter hole. Checker
construction has been split into three sections so as to suit the design criteria of 1450°C
dome temperature and thermal condition across the height of the stove. Combination of 45 %
Alumina checkers, 62 % Alumina checkers and silica checker bricks are provided.
The use of Silica bricks has been envisaged owing to following inherent silica brick quality:
i)Practically negligible expansion/contraction coefficient above 600 ° C.
ii) Resistance of silica bricks against sticking of dust.
Conical portion of the stove exists between burner chamber and checker chamber. The hot face
consists of silica bricks and is backed by four insulating layers. The 4th layer is a 40 mm thick
slab insulation against, 35 % gunning castable.
Preferably, the minor dome is of hemispherical shape, for better stability at high
temperature. Dome refractory construction consists of two layers of high alumina refractory
bricks (62 % Alumina/45 % Alumina) backed up by three layers of insulation, 35% alumina
gunning castable and insulation slab.
The annular ignition chamber with ceramic burner to supply BF gas and combustion air is
arranged at the top dome .BF gas and combustion air are supplied into the ingnition chamber
through slots of size 154 mm X 75 mm. Mixing of the gas and air in the ignition chamber ensure
complete combustion of the fuel mixture before entering the checker work .Ceramic burner is
constructed with the combination of 62 % and 45 % Alumina bricks . 45 % Alumina bricks is
backed up with SS sheet, insulation slab and 35 % Alumina gunning castable.
Checker supporting system consists of grids, columns and girders. The design of the checker
supporting system allows the grids section only limited horizontal movement completely
independent of the refractory lining. The material selected for the checker supporting system is
as follows:


Estimated load of checker supporting system approximately 26.0 t/stove.
Estimated load on checker support 320 t/stove.
The cast iron with above chemical analysis has an advantage of little deformation under load
and high temperature and there is no introduction of residual stress during manufacturing
process.

A stove building is provided on Hot Blast Main side. The building is equipped with electric hoist
of 7ton capacity for handling of various valves in hot blast branch, BF gas branch lines and
combustion air branch lines.
Combustion air required for burning of BF gas in stoves is supplied by combustion air fan
system. There may be two fans, one working and one stand by. Capacity of each fan is
20000 Nm3/h. Motorised VIV damper is provided at the inlet of each fan for automatic
control of air flow. Multi louvered manual damper is provided at outlet of each fan, with close
position limit switch.
Air is supplied to stoves through ducts. There are total three numbers of stoves. Air is
supplied to maximum two numbers of stoves at a time. Supply air pressure at the inlet of
stove will be 600mmWC minimum.
Delivery header pressure shall be maintained at required level by controlling air flow quantity
through inlet VIV damper of working fan. Inlet VIV damper of working fan & outlet manual
damper of stand by fan shall remain closed at starting of fan. After this, the inlet VIV damper
shall open as per requirement mentioned
Continuous water is required for cooling of hot blast valves in stoves. Water at the rate of 36
m3/h per valve is required. Water supply and return lines are provided to supply cooling
water and take out hot water from each valve. These water supply and return water pipe line
are connected to existing supply and return lines of the plant at stove battery.

The sizing of various openings provided in the stove shell is based on the maximum
operating/working conditions, likely to occur during stove operation. For sizing of gas and air
inlets to ceramic burner and waste gas branches, two stoves operation conditions have been
used. The sizing of cold blast inlet is based on input conditions. Hot blast stove has been
sized on maximum hot blast temperature of 1250°C.
Based on the above criterion, the inner diameter (ID) steel of various opening has been arrived at
and are given below.

Suitable platforms at various elevations along with stair case have been provided for easy
operation and maintenance of the valves and instruments. Also platforms with suitable
approach have been provided for manhole at various levels.
For Power supply and control of drives and solenoids required for Hot Blast Stoves four numbers
of MCC (one MCC each for drives and solenoids of each Stove and a common MCC for all other
drives and solenoids) are provided. The voltages used for various purposes are as follows:

DOL starters are provided for all the motors except the Combustion Air Fan motors. The
combustion Air Fans are provided with Star-Delta Starters. One number 2.5 KVA UPS with
sealed maintenance free Battery set is provided for power supply to PLC and associated
equipment.
Illumination: Appropriate illumination of the electrical and control rooms, hydraulic room,
stoves platforms, stairs and so on are provided.
EARTHING AND CABLE LAYOUT
Earth grids around stoves are buried at approximately 800mm below ground and this is
connected to existing plant grid at at least four places. All the equipment of the stoves is
suitably earthed through the above buried grid. Similarly, grid is provided in electrical room,
control room and hydraulic room for equipment earthing in these rooms. Lightning protection
is provided for the Stoves Chimney by providing two nos. 2.5m long air terminations and
connecting the same to earth pits independently.

PROGRAMMABLE CONTROLLER AND ASSOCIATED EQUIPMENT
One number PLC , one number industrial PC, two numbers printers and one 19" industrial
colour monitors with keyboards and so on are installed for data acquisition, monitoring and
control of drives and instrumentations systems, apart from generation of operation reports,
maintenance reports, graphics(overview and individual), trends display and prints and the
like . PLC is provided with CPU and one remote I/O unit. One PC based PLC programming
unit is required as engineering terminal for PLC programming, editing and trouble shooting
purposes.
The Battery of stoves may consist of three numbers high efficiency, high temperature top fired
type stoves for supply of hot blast continuously to the Blast Furnace by heating up the cold blast.
The stove system is designed to supply a specified quantity of hot blast at a desired temperature
to the Blast furnace. These stoves run in a sequential manner. Normally one stove supplies
hot blast to the furnace and the other two stoves are under heating. When the stove on blast is
cooled, the stove which has completed heating first is brought into blast phase and the cooled
stove is put on heating.
Stoves are heated up by burning clean BF/mixed gas. Two numbers of combustion air fans are
provided with suction control dampers and dampers on the delivery side (for fan isolation only)
for supply of combustion air at a desired constant pressure to the stoves. The ratio of gas and
combustion air is controlled such that the desired combustion chamber temperature is achieved and
within the permissible time limit. This status of the stove under the above conditions is called ON
GAS. On completion of heating, the stove is isolated. This status of the stove is called GAS-TO-
ISOLATION stage.
The status of the stove which is taken form blast to isolation is called ON BLAST- TO-ISOLATION.
The stove which is on blast cools down progressively and reaches a stage when it will not be
possible to supply hot blast at desired temperature. Then the stove which is in ISOLATION stage
is put on blast and the cooled stove is taken to isolation and then to heating. The status of the
stove which is supplying hot blast to the furnace is called ON -BLAST.
It may be noted that for maintaining a continuous supply of hot blast to the blast furnace, it is
essential that at least one stove must be ON BLAST at all times. Therefore, the incoming stove
must be brought ON BLAST before taking the outgoing stove TO ON BLAST-TO-ISOLATION stage
and subsequently to ON GAS.
In case of non-availability of one stove, supply of hot blast to the furnace is achieved with two
stoves.
COMMON MECHANISMS FOR STOVES(3 NO.S)
l.Cold Blast Mixer Main Shut-off Valve (CB MMSV) - I No. - Hydraulically
operated
2. Cold Blast Mixing Regulating Valve (CB MRV / TCV- 1101) - 1 No. - Motorised actuator
operated . 3.Moisture Control valve (MCV-103) - 1 No. - Motorised actuator operated
4.Back Draught Valve (BDV) - 1 No, - Hydraulically operated.
5.Combustion Air Fans (CAF1/2) - 2 Nos. (1W+1S)

6.Combustion dampers for combustion air pressure (at the out let side of combustion air fans)
- 2 Nos. - Manually operated.
7.Hydraulic power pack for the following stove valves:
-4 Nos. Hot Blast Valve (HBV)
-3 Nos. Cold Blast & 3 Nos. Cold Blast by Pass Valve (CBV)/(CBBPV)
-3 Nos. Chimney Valves with Built in Port (CV)
-3 Nos. Combustion Air Shut off Valve (CASV)
-3 Nos. Gas Shut off Valve, (GSV)
-3 Nos. Gas Safety Shut off Valve (GSSV)
-3 Nos. Gas Shut off Goggle Valve (GSGV)
-1 No. Mixer Main Shut off Valve (MMSV)
-1 No. Back Daft Valve (BDV)
INDIVIDUAL STOVE MECHANISMS
l.Hot Blast Valve (HBV) -1 No. -Hydraulically operated.
2.Cold Blast Valve (CBV) -1 No. - Hydraulically operated.
3.Cold Blast Bypass Valve (CBBPV) - 1 No. - Hydraulically operated.
4.Chimney valve with equalising port (CV) - 1 No. - Hydraulically operated.
5.Gas shut off goggle valve (GSGV) - 1 No. Travel of disc by motorised
actuator, clamping/de-clamping by hydraulic.
6.Gas regulating valve (GRV - FCV - 1202 FOR STOVE-1, FCV-1302 FOR STOVE - 2, FCV- 1402
FOR STOVE - 3,) 1 No.- Motorised actuator operated.
7. Gas safety shut-off valve (GSSV) - 1 No, - Hydraulically operated.
8. Gas bleeder valve - 1 No, - mechanically linked to GSSV
9 Gas shut-off valve (GSV) - 1 No. - Hydraulically operated.
10.Combustion air regulating valve (CARV-FCV-1201 forstove-1, FCV-1301 for stove-2, FCV-
1401 for sove-3) - 1 No, Motorised actuator operated.
11.Combustion Air shut-off valve (CASV) - 1 No. - Hydraulically operated.
Control of Stove Mechanisms
PLC located in the control room is used for automatic control of stove mechanisms and for
remote manual operation of stove mechanisms through human machine Interface (HMI)
station.
The following control modes are available for the stove mechanisms:
i) Local Mode
ii)Remote - Manual - For operating mechanisms individually through
HMI
iii)Remote - Auto - For cyclic operation through HMI
i) Local Mode: -
It is possible to operate the various stove mechanisms from the local control boxes provided near
the drive of each mechanism for electrically operated drives and LCBs located near the respective
valve stand for hydraulically operated mechanisms.
Local mode is selected for each stove valve individually through a Local-Remote Selector
Switch
provided in the LCB.
This mode is used during commissioning, maintenance and repair work.

ii) Remote - Manual Mode
In this mode of operation the various mechanisms of each stove can be operated through HMI
station. It is possible to operate each individual mechanism with all safety and sequential
interlocks through the A key board/mouse. Further, the state of each stove is changed by
initiating cyclic operation through HMI station.
iii) Remote -Auto Mode
Under this mode of operation the stoves are totally under PLC control either cyclic or time mode
of operation can be selected through HMI under auto mode. The stoves are switched from one
state to another sequentially by PLC. The change cover from On-blast to isolation can be
initiated as a function of mixing regulating valve position or temperature of refractory
> above checker chamber is case of cyclic mode and as per fixed time sequence set by the
operator in case of time mode.
OPERATING DEVICES ON LCBS
1) For Hydraulically Operated Valves
a) Local / remote selector switch
b) Stop push button (mushroom head lockable)
c) Open / close push buttons
d) Open / close indication
For Electrically Operated Valves
a)Local / remote selector switch
b)Stop push button (mushroom head lockable)
c)Open / close push buttons.
FACILITIES ON VDU
For operation and control of stoves from BF control room. 21" colour VDUs with keyboards
and mouse may be used.
Following displays shall be provided on the VDUs.
Display of Day, Date & time at the corner of VDU screen.
Sub-menu like command menu, report menu and so on.
Operation mode (Remote manual or AUTO)
Mimic display of stoves, hydraulics system of stove valves
PID loop display and display of other parameters (OverView Screens).
Display of local/remote selection, local PB operation, I/O address etc.
Display of READY FOR AUTO OPERATION before plant start command is given.
Faults with description, date and time of occurrence. Occurrence of any kind of fault is displayed
with brief description on VDU with flashing and with acknowledging facility. Once the fault is

acknowledged, the flashing becomes steady. The fault remains on VDU screen, till same is
rectified.
Shift-wise, daily, weekly, monthly, yearly logging of faults for various mechanisms and so on.
Also, logging of reports/events/data etc. the same intervals.
Display of trend / History graphics of process parameters with operator scalable time axis.
Help screens for trouble shooting.
OPERATION & CONTROL MODES
All the individual and common stove valves & hydraulic system for stove valves, are provided
with following modes of operation and control : -
1)Local
2)Remote Manual
3)Automatic
GSGV for stove, is provided with only local mode of control from the LCB located near the
valve stand.
The selection of local mode of operation is carried out with the help of selector switch LOCAL
and REMOTE, which is provided on respective LCB for the individual drives. Automatic
operation of stoves come into effect, when remote operation is selected from LCB and
automatic selection from HMI.
The stoves can be operated under following mode of controls :-
1) Individual (Remote manual)
2) Cyclic (remote manual)
3) Automatic - Cyclic mode
Time mode
The selection of individual, cyclic and automatic mode of operation of individual stove valves
shall be done from HMI station.
Under individual selection, operation of each drive shall be carried out by the operator
through PLC keyboard with process interlocks provided by the PLC.
LOCAL MODE OF OPERATION
Under this mode, the valves and other drives are controlled form local control stations (LCS)
located near each mechanism for all regulating valves and near respective valve stands for
all hydraulically operated valves. This mode is only for maintenance and testing purposes.
PLC provides safety interlocks / permission for operation of valves under this mode.
REMOTE MANUAL MODE OF OPERATION
Remote manual mode of operation is possible from following two ways:-

The operator shall select individual or cyclic operation and operation desired ( ON GAS TO
ISOLATION/ ISOLATION TO ON BLAST / ON BLAST TO ISOLATION ETC. ) through the key
board.
Individual stove valves, common stove valves and combustion air fan system are controlled from
this station
Individual mode of operation of stoves:
Under individual mode of operation, PLC opens/ closes various valves and starts / stops various
drives with correct sequence of operation and all interlocks. Valves / drives on process view of
the HMI screen blinks in order to draw the attention of operator for correct sequential operation of
valves after executing safety interlocks by PLC. After the current valve is operated, next valve
corresponding to correct process sequence blinks and so on. In case of any wrong sequence of
operation of valves / mechanisms by operator, PLC does not accept the command to open / close
/ start / stop any mechanism and raise audio visual alarm as wrong operation.

Cyclic mode of operation of stoves :
Under this mode of operation all valves of the stove are operated from the HMI
station by selecting operation required through key board. Starting of the drives
as per desired sequence is carried out by the PLC. All safety interlocks, sequence
of operation of valves / mechanisms depending upon the stove duty selected are
executed by PLC. Under this mode, in case of any fault or failure of operation of a valve /
mechanism, audio- visual alarm is raised for operator's intervention on the VDU and printed
out.
AUTOMATIC MODE OF OPERATION OF STOVES
This is the normal mode of operation of stoves. Under this mode of operation all stove valves,
change over of stoves from one state to the other are executed by PLC. All safety interlocks,
sequence of operation of valves/mechanisms are executed by PLC. Under this mode, in case of
any fault or failure of operation of a valve/mechanism, audio visual alarm are raised on VDU for
operator's intervention. The detailed fault is displayed on the VDU and also printed out on priority.
Under this mode, stoves are controlled using VDU-key board located at BF control room. When
the system is made ON and VDU-Key board is powered up, the screen automatically shows the
main menu.
The AUTO mode is selected through key board/ mouse form the HMI station. Under auto mode
1) cyclic 2) time mode of operation can be selected.
Once a command is selected (or is effective), it is highlighted in the display. It is possible to
select any item from the main menu.
Facility is provided in each menu, to switch over to any other menu/sub menu in accordance with
operator's choice. The fault message appears on the VDU in all pages.
Depending upon the menu page selected, the operator is able to give commands, view mimic
pages/data/fault summary etc.
Before start of automatic operation of hot blast stoves system following have to be ensured: -
1. Auto & cyclic / time mode of operation is selected.

2. All the valves/drives are selected as remote mode of operation from LCB. Stop push button
at LCBs are not kept in pressed condition.
3. Working and stand by selection of hydraulic pumps for stove valves, combustion air fans
are ready
4. Control and power supply to all connected drives are healthy and are free form fault.
5. Selection of stoves are completed. In case one stove is to be taken out for
service, same is selected as withdrawn form VDU.
6. PLC system and related instrumentation control system are healthy.
DESCRIPTION OF INTERLOCKS FOR TP FIRED STOVES
Safety interlocks
The following safety interlocks for various stove equipment are provided for hot blast stoves;
Hot Blast Valves
This Hot blast valve will not close if the hot blast valve for the next stove is not open.
This Hot blast valve will not open, when the pressure difference across the cold blast valve
exceeds a preset value.
Gas safety shut off valve
Gas safety shut off valve will not open under the following conditions:
-When the gas pressure is below 300 mm WC (Adjustable)
-When the chimney valve and combustion air shut off valve are not open
-When the combustion fan not in on state.
-GSGV is not open.
During the normal operation in gas phase the gas safety shut off valve automatically closes
under the following conditions:
-When the combustion air supply stops or the pressure is lower than the present value.
-When the gas pressure drops below 300 mm WC (Adjustable)

-When the waste gas temperature rises above the set value-when the stove top temperature
exceeds the set value.
-When any of the equipment related to gas phase closes.
Gas control valve(FCV-1202/FCV-1302/FCV-1402)
This valve does not open when the stove is on blast or is being switched form isolation to
blast. This valve is operated only in gas phase. PID control function for this valve is enabled
in gas phase when the valve open at ignition angle and flame has been detected.
Combustion air valve
Combustion air valve is not open
-When the stove is on blast
-When the stove is switched from blast to isolation or vice-versa
-When the combustion air fan outlet damper has not opened.
GAS SHUTOFF VALVE
Gas shutoff will not open.
-When the stove is on blast.
-When the stove is being switched from blast to isolation or vice-versa.
Chimney Valve
-Chimney valve will not open
-When the stove is on blast
-When the stove is being switched form blast to isolation or vice-versa
Pressure relief valve (chimney valve- port)
This valve is used to equalize the stove pressure with atmospheric pressure while the stove is
taken from isolation to ON Gas. This will not open.
-When the stove is on blast state.
-When the stove is being switched form blast to isolation or vice versa.
Cold blast valve
Cold blast valve does not close, if the next stove to be on blast does not complete the
changeover to blast phase. The valve does not open:
-When the stove is on gas
-When the stove is being switched form isolation to gas or vice versa
Gas shutoff Goggle valve (not operated through PLC) is to be closed when

The corresponding stove is in isolation state
The corresponding stove is "withdrawn" form operation
Process interlocks
The following process interlocks are provided:
If during ON GAS, the combustion air pressure drops to below 300 mm WC ) (adjustable), the gas
regulating valve and gas safety shutoff valve is closed automatically and stove is switched to
isolation.
If the gas line pressure drops below 300 mm WC (Adjustable) the gas safety shutoff is closed
automatically and the stove is switched to isolation.
If the flue gas temperature exceeds 400 degree C or the set value, gas safety shutoff valve
closes and the purging/bleeding of gases, starts automatically.
Cold blast valve does not open till pressure equalization takes place between the cold blast main
and stove.
The back draughting valve opens only when all the hot blast valves and mixer shutoff valve
are closed.
PROCESS ALARMS / INTERLOCKS TO BE GENERATED THROUGH PLC SOFTWARE
A) When time of operation of any of the valves exceeds the normal values, alarm is generated.
B) PLC permission contacts in local mode ensures all process interlocks such that the stoves
under operation are not affected by local operation of,valves for the stove taken on Local mode.
C) When the cold blast pressure falls below 1.0 kg/cm2 (Adjustable), an alarm is generated.
D) When the hot blast temperature falls below 800°C (Temp, set point adjustable) an alarm is
generated through PLC software.
E) When the flue gas temperature reaches above 400°C during on gas cycle, and alarm is
generated through PLC software.
F) When the combustion chamber refractory temperature falls below 700°C , (Adjustable) an
alarm is generated through PLC software.
G) Pressure of BF gas is in the range of 400 to 700 mm We. When BF gas pressure, is less than
400 mm WC, an alarm is generated through PLC software.
H) When the temperature above checker chamber reaches more than 1400°C, an alarm is
generated through PLC software.
I)When the temperature of Silica bricks falls below 800 °C( adjustable), an alarm is generated
through
PLC software.

J) When the combustion air pressure falls below preset value, an alarm is generated through PLC
software and gas shut off and gas safety shut off valve is closed.
OPERATION OF COMBUSTION AIR FAN SYSTEM
Under following conditions the standby fan start command is given by PLC with necessary
alarm.
The selected fan trips due to overload or any other fault either during starting or during running.
The suction control valve fails to open or close due to any fault like overload, torque switch etc.
either during initial starting or during subsequent control.
The system is not able to build up required pressure after 3 minutes.
(Adjustable) of running of the selected fan.
Combustion air pressure is low for 5 second (Adjustable) during running of the fan.
In case of any electrical fault, change of selector switch form remote to local
Position, operation of stop PB from LCB during automatic operation of stoves.
The exact fault, date, time of occurrence etc. is printed out automatically. The stove
tenderer ensures closing and opening of manual valves at fan outlet.
One fan runs for 75 % of time and other one runs for 25 % time only and the changeover
intimation appears on the screen for operator's information and action.
OPERATION OF HYDRAULIC PUMPS
The hydraulic pump is started whenever any hydraulic valve is operated to change the state,
i.e. ON GAS-ISOLATION - ON BLAST or vice versa. The pump stops, when none of the stoves
need change of state. Under normal operation of furnace, one stove changes from ON GAS -
ISOLATION - ON BLAST and immediately it is followed by another stove changing from ON
BLAST - ISOLATION - ON GAS. The filtration pump remains running continuously and is
stopped by only temperature high contact. The detailed control logic and equipment
associated with hydraulic system has been described separately below.
FROM ISOLATION TO ON GAS STATE
Initially let us assume that the stove is in isolated state. Under isolated state all the
stoves valves are closed. Only the gas bleeder valve which is mechanically linked
to Gas safety Shut-off valve (GSSV) is open. The hydraulic system is ON and auto
Mode selected in MCC. This starts the pump and keep the line pressurized.
Now suppose this stove is to be taken to ON GAS or heating, then the following sequence of
operation is executed by PLC one after the other.

1) Open Chimney valve with port. Port will open and the drive stops as soon as the port open
limit switch signal is received.
2) As soon as port starts opening, the stove starts depressurizing. The pressure switch
gives signal that the stove is depressurized. In case the stove is not depressurized within 1
minute (Adjustable), alarm is raised on the VDU.
3) PLC checks the combustion air pressure, in case same is within limit, chimney valve open
command is given.
4)PLC checks the combustion chamber temperature. In case same is more than 700 Deg. C
(Adjustable), command to open Combustion air shut-off valve (CASV) and Combustion air
regulating valve (CARV- FCV- x 1201 FOR STOVE- 1, FCV-1301 FOR STOVE - 2, FCV - 1401
FOR
STOVE - 3) up to ignition angle is given (Inlet damper fan control is transferred to PID controller
to maintain combustion air pressure at preset value). CASV opens fully and Combustion air
regulating valve opens upto ignition angle as sensed by PLC from external limit switch contact.
In case, the temperature is below 700 deg. C, necessary alarm is raised on VDU and valves in
combustion air line does not open.
5) Command to open Gas shut-off valve (CSV) is given. Same opens fully as sensed by limit
switch contact. )
6)Command to open Gas safety shut-of valve (GSSV) is given. Same
opens fully as sensed by limit switch contact. The bleeder valve which is mechanically linked
to GSGV closes.
7) Command to open Gas regulating valve (GRV FCV- 1202 FOR STOVE-1, FCV - 1302 FOR
STOVE - 2, FCV - 1402 FOR STOVE - 3) up to ignition angle is given. GRV opens up to ignition
angle as sensed by limit switch contact.
8)As soon as flame is detected (sensed by PLC from flame detector), PID controller for GRV (FCV
- 1 202 FOR STOVE- 1 , FCV - 1 302 FOR STOVE 2,FCV - 1402 FOR STOVE- 3), and Combustion air
regulating valve > (FCV- 1201 FOR STOVE -1, FCV -1301 FOR STOVE-CV- 1401 FOR STOVE - 3) is
enabled for continuous control by PLC. The heating control during the first phase till the stove top
temperature reaches the set valve and during the second phase till the flue gas temperature reaches
the set value with dome temperature maintained at the set value is achieved by controlling the
gas to air ratio.
9) In case flame is not detected within 5 seconds (Adjustable), close command for GSSV and
GSV are given. Suitable audio visual alarm is raised and is taken to manual mode.
10) The stove is now ON GAS state or on heating.
11) The stove continues to be ON GAS as long as heating is not complete or it is called for
supplying the hot blast to the furnace under emergency conditions.
12)During ON GAS state of stove, PLC monitors the following faults and closes GSSV & GSV.
-Combustion airflow low,
-Combustion air pressure low.
-Clean BF Gas pressure low.
-Stove top temperature is exceeding set limit.
-Waste gas temperature is exceeding the set limit.
-Necessary alarm is raised on the VDU.
13) During opening of any valve, in case of any faults, suitable alarm are raised on the VDU.

14) During the ON GAS state of the stove, in case of power failure and other emergency
conditions indicated below, the GSSV closes automatically by counterweight.
-When air supply stops or the pressure is lower than the set value
-When gas pressure falls below 150 mm WC
-When gas temperature rises above set value
-Flame is not detected
-When the combustion chamber temperature falls below the set value
When any of the valves related to gas phase closes
FROM ON GAS TO ISOLATION STATE
It may be noted that a stove is to be transferred from ON GAS state to ISOLATION state, when
-The stove supplying the hot blast has cooled down, indicated by 90% closure of Cold Blast
mixing control valve, and this is the hottest stove or
-The stove is fully heated. This is sensed by PLC when the temperature at the top of checker
chamber has reached the set value and waste gas temperature has reached the set limit.
For transferring the stove from ON GAS to ISOLATION state, following sequence of operations are
executed by PLC one after the other:
1)PLC gives command to close Gas regulating valve (GRV - FCV - 1202 FOR STOVE - 1 , FCV - 1
302 FOR STOVE - 2, FCV - 1402 FOR STOVE - 3,), fully closed signal is checked by PLC from
limit switch contact.
2) Close Gas shut-off valve (CSV).
3) Close Gas safety shut-off valve (GSSV). As soon as GSSV is fully closed, Gas bleeder
valve is opened since they are mechanically linked.

4) The command is released to fully open the combustion air regulating valve (CARV- FCV- 1201
FOR STOVE- 1, FCV- 1301 FOR STOVE - 2, FCV - 1401 FOR STOVE - 3) for purging of stoves
(i.e. remove any unburnt gases).
5) CARV close command is given after lapse of 60 seconds (Adjustable)
6)Close Combustion air shut -off valve (CASV)
7) Close chimney valve CV.
FROM ISOLATION TO ON BLAST STATE
The changeover of stoves from ISOLATED state to ON BLAST is done as a function of
following: -
1) Cold Blast Mixing regulating Valve (CBMRV-TCV- 1101) position mode
of operation,

2) Time mode of operation
The selection of above modes of operation are done by operator form VDU-
key board in the BF control room.
i) CBMRV - TCV - 1101 POSITION MODE OF OPERATION
It is essential that the stove system supplies hot blast to the blast furnace continuously at a
desired constant temperature. This is achieved by mixing
cold blast through mixing control valve with the hot blast. As the stove which is supplying
hot blast to the blast furnace loses the heat, the amount of cold blast being mixed reduces
continuously. The temperature of the hot blast is maintained constant by PLC by regulating
the closing of the CBMRV (TCV - 1 101) through PID control. When the CBMRV - (TCV -
1101) is closed about 90 %, (Limit switch contact is sensed by PLC system), it indicates
that the stove which is on blast is sufficiently cooled down and a new stove has to be put on
blast.
Since the stove is fully heated up initially, the cold mixing regulating valve (CBMRVATCV -
1101) is opened fully by PLC and kept open for about 1 minute (Adjustable). After lapse of
this time, the control of this valve is taken over by the control loop for maintaining the blast
temperature at the set value.
ii) TIME MODE OF OPERATION
Under this mode of operation of stoves, the change over of the stove from ON BLAST to isolation
is determined by the time the stove is ON-BLAST. This time is set by the operator from VDU-key
board After lapse of the set time, the stove which has completed heating and in ON GAS-TO -
ISOLATION status is brought to ON BLAST and the stove which is ON BLAST is taken to isolation
by PLC automatically.
Now suppose the stove is to be taken to ON blast, then the following sequence of operations are
executed by PLC one after the other.
1) Open the Cold blast by pass valve (CBBPV)
2) The stove pressurizes as the cold blast fills the stoves. This is sensed by PLC from the
pressure switch. In case, the stove is not pressurized within 60 seconds (Adjustable), alarm is
raised on VDU.
3) After stove is pressurized, open hot blast valve (HBV).
4) Cold blast Mixing Main shut-off valve (MMSV) is opened if same is not in open condition. MMSV
remains fully open during the normal operation of stoves.
5) Open cold blast valve (CBV) & Cold blast mixing regulating valve (CBMRV-TCV-101 ) fully.
After lapse of 60 sec. (adjustable ) , control of CBMRV- TCV - HOlis transferred to continuous
control by PLC.
6) Close Cold blast bypass valve (CBBPV)

7) The stove is now ON BLAST state. Now the cooled stove can be taken to isolation and then to
on gas for heating.
FROM ON BLAST TO ISOLATION
Following sequence of operation is executed by PLC: -(Is carried out by PLC only if
another stove is ON - BLAST)
1) Close Cold Blast Valve (CBV)
2) Close Hot Blast Valve (HBV)
Now the stove is in ISOLATION state and can be taken to ON GAS .
TO BACK DRAUGHT
Considering the furnace condition, the operator decides to take the furnace on back draught.
When taking for back draughting all other sequential changeover of stoves cannot take place.
The stoves ON GAS remains as they are and the stove ON BLAST is isolated. The furnace is
taken on back draught through a separate stack. Operator selects back draught command
from command menu using VDU-key board. The operator reduces pressure in hot blast line to
the extent possible.
Following sequence of operations are executed by PLC : -
1) Close Cold blast mixing regulating valve CBIMRV (TCV-1101) and cold blast mixing main
shut off valve (MMSV).
2) Close all three (3) Hot Blast Valves (which ever is not closed) and Isolation valve.
3) Open Back draught valve (BDV).
Now the furnace is in BACK DRAUGHT state.
When back draught valve is operated from local control station, PLC gives permission
contact for BDV to open only when
-All three hot valve and Isolation valve closed are closed.
-CBMRV - (TCV - 1 101) & MMSV are closed.
-Hydraulic system is ON
FROM BACK BRAUGHT TO ON BLAST
Considering the furnace condition, the operator decides to take the furnace form back
draught to on blast. Operator selects form back draught command from command menu
using VDU-key board.

1) Close Back draught Valve (BDV)
2) Put one of stove, which is heated on blast.
3) Open command to Cold blast mix regulating valve (TCV-1 101) and MMSV are given. After
the valve CBMRV (TCV- 1101) is opened control of the valve, is transferred to PLC.
COMMON POWER PACKJGeneral Description & Control Logic for Valve Operation Through
Common Power Pack)
One common hydraulic power pack has been provided for operation of following valves:
1) 4 Nos. Hot Blast Valves (one valve for each stove & one isolation valve)
2) 3 number cold blast &. 3 Nos. Cold blast bypass valve (one number each for each stove)

3) 3 Nos. Gas Safety shut-off & 3 Nos. gas shut - off valve (one number each for each stove)
4) 3 Nos. Gas Shut-off Goggle valve (one number for each stove), for clamp/declamp only.
5) 3 Nos. combustion air shut of valve (one number for each stove).
6)3 Nos. chimney valve (one number for each stove).
7)One No. Cold blast mixer main shut off valve (common valve).
8)1 No. Back Draught valve.
The hydraulic power pack has been provided with two numbers of pumps
(1W+1S). Each pump has been provided with one number of solenoid operated
pressure relief cum unloading valve. Selection of working and standby pump is
done by operator through selector switch located in the MCC module. In case
of failure of working pump, the standby pump is started automatically.
The hydraulic power pack is controlled form following places: -
1) Local control cabinet
2) MCC module
OPERATING DEVICES ON LOCAL CABINET FOR HYDRAULIC POWER PACK

A) PUSH BUTTONS, SELLETOR SWITCH
1) Emergency OFF Push button
2) Local-remote selector switch for Hydraulic pump
3) Local-remote selector switch for filtration pump
4)Start/stop push button for hydraulic pump
5) Start/stop push button for filtration pump
6) Pump-1/Pump - 2 ON indication tanks
B)ALARM ANNUNCIATOR:
An enunciator in the MCC module provides for audio visual alarm under the following
fault condition of hydraulic power pack.
1) Tank oil level low (Red)
2) Low accumulator pressure (Red)
3) Oil temperature high (Red)
4) Main line filter clogged (Red)
5) Cooling system filter clogged (Red)
6) Low pressure on main line (Red)
7) Pump change over
On occurrence of any of the above faults, the corresponding annunciation
window lamp flashed with hooter on. When the fault is accepted by "accept
push button", the hooter stops and window lamp glows continuously without blinking. On
reset if the fault is removed, the lamp goes off. Test push button glows all the lamps with
hooter on.
One composite fault signal for the hydraulic power pack is provided to the
PLC.

CONTROL LOGIC
Pump - 1 / pump -2 selection is provided in the MCC
The selected pump motor is started under no load condition with the pressure relief- cum-
unloading valve in the closed position. After lapse of about 4 seconds (Adjustable), the
respective solenoid of pressure relief cum unloading valve is energized and the valve is
opened to load the system. In case of tripping of the working pump, the solenoid is de-
energised to close the valve and the standby pump, is started automatically in the same
manner.
When any of the hydraulic valves are operated, a common command for hydraulic
power pack pump start is given to start the selected pump. These are carried out
in the MCC through relay logic.
An accumulator station is provided for storage of pressurized oil for emergency operation of
GSSV, HBV & BDV in case of power failure. The accumulator is provided with a pressure
switch. When the oil pressure in the accumulator falls below set pressure (90 bar-Adjustable),
pressure switch gives alarm signal both on VDU and on annunciator. The pump gets started
automatically to built-up the pressure, in accumulator above set pressure.
Two filters are provided one on the main line and the other on cooling system. Both filters are
provided with mechanical and electrical clogging indicators. When the working filter is
clogged, it develops back pressure and in turn I raises alarm in the VDUs as well as on the
annunciator.
A low-level float switch is provided in the oil tank for monitoring the oil level. In case of low oil
level in the tank, the working pump trips and both pumps can not be started unless oil level
in the tank is above low level. Alarm is indicated in VDU and annunciator when oil level is
low.
The VDU reports fault in hydraulic power pack and the type of fault can be seen by the
operator in the annunciator.
One number heat exchanger has been provided with the system just after continuous
filtration system along with one single solenoid operated direction control valve for flow of
cooling water and one number of the temperature switch.

The temperature switch is mounted on tank. In case, the temperature of the tank exceeds
set value, this switch gives contact to initiate alarm and starts the circulation pump. Solenoid
for cooling water is energised whenever circulation pump is on.
Each hydraulically operated valve has been provided with two numbers of solenoid valves one
for opening and the other for closing the valve. When the valve needs to be opened,
the solenoid meant for opening is to be energised. As soon as the valve is fully opened, the
open limit switch mounted externally on valve operates and give signal to de-energise the
solenoid coil. Similarly for closing the valve, second solenoid is energised. The full closing of
the valve is sensed by close limit switch mounted externally on valve to give signal to de-
energise the solenoid coil.
The Gas safety shut off valve is provided with an additional safety feature, so that in case of
emergency condition or power failure, the valve closes with the help of counter weight. For
this purpose the valve has been provided with a spring return type, single solenoid operated
direction control valve. Under normal operation, this solenoid is kept continuously
energised. In case of emergency of power failure, the solenoid is de-energised, so that the
valve closes automatically with the help of counter weight.
Further, three numbers of Gas Shut-off Goggle valves are also be operated with help of the
common hydraulic power pack. During normal operation, the Goggle Valves are kept in open
position. The valve is operated form local control station near the valve stand. The operation of
Goggle Valve is electro hydraulic. Hydraulic system is used for clamping and de-clamping,
whereas travel of disc is electrical through motorized actuator mounted on valve. VALVE
OPENA/ALVE CLOSE indication signals are given to the PLC for status information on VDU.
HMI STATION .
SYSTEM FEATURES
The over system has the following minimum features
- System configuration & system debugging
-Process control security and data integrity through redundancy
-Friendly administration of user access rights to specific functions, tags, screen and commands.
-Project development environment (with fast access to project data & global settings)
-Graphic editor with alignment and zoom features
-Event management system/ event driven priority system
-Development facility
-Complete peripheral support

-open communication
-Data management
-Memory error logging
-Use archives, freely structurable data
base with run time display and
import/export functions
-Mathematical computations
-High level language support
-Power fail save and restart
-System diagnostics up to card level.
APPLICATION SOFTWARE
The application software employs the following:
-Modular structural program approach
-Complete flow charting
-Flexibility in program development methodology to accommodate changes
easily
-Plant control and regulation through command menu for easy and fast selection of
operational modes, selection / deselection of equipments, sequential / time mode operation
of stoves etc.
-Standard programmable multifunction PID controllers and diagnostic unit for real time
monitoring of controller operation
-Plant related mimic synoptic displays
-Alarm data display- status, priority, alarm messages
-Failure mode task priority scheduling for automatic execution depending on failure
recognition by the diagnostic concerned.
-Pressure and temperature compensation for cold blast flow loop
-Averaging of dual MV inputs form 5 Nos. 'S' type duplex T/Cs for temperature control above
checker bricks and hot blast temperature measurement and display of these values on VDU.

Rejection of low MV input with alarm display on VDU in case is 1% less than the other MV input
of the thermo-couple
-Alarm management tool-Storage, Change of status logic variable and associated changes
with annunciator.
-Data logging
— Acquisition of both analog and digital process data
—Sampling time for monitoring loops - 500 milli seconds (alarm interlocks)
—Bad input detection
—Input limit checking
—Flexible zero/span corrections
—Averaging if required at time selectable in minutes, hours, days and months.
—Conversion to engineering units
—Time span for data storage (i.e Nos. of days) and Nos. of data to be stored for trending of
analog inputs shall be decided in consolation with client.
-User friendly
-Interface to external modules
HMI STATION FEATURES :
HMI Screens presents to the operator complete information about process
and status of various equipment levels with varying degrees of details and provide
interface to operator to supervise and control the complete plant form the HMI
station.
Provision is made for operator interaction on line through key board/mouse associated with the
CRT unit to.
-Modify control selections, set-points calculations, and so on.
-Control operation of devices (drives, solenoid valves, control valves etc.)
-Access to process graphics & supervisory reports and so on.
-Acknowledge and silence alarms and access alarm summary
-Access and print reports
-View and customize trend display of real time and historic data with multiple trends on top of one
another for comparison for all analog inputs.

Different colors are used to display status of drive mechanisms ON/READY/FAULT.
Details of fault conditions (Torque switch, over load, local stop, in auto mode etc.)
Data logging and reporting functions include Trends for all analog process parameters with
selectable time scale for analysis and determination of corrective measures.
Alarm status as they occur is presented on CRT and is stored for presentation as per operator
selection (area-wise/sequence of occurrence/date/ time sequence/ priority/ combination of two
or more).
Software provision is made to display the following Minimum requirements:
1. Opening page with project description, name of supplier, name of consultant, Sub-menu like
command menu, report menu etc.
2. Display of READY FOR AUTO OPERATION before plant start command is given. Command
menu in the form of buttons for start and stop of each equipment under remote manual mode of
operation.
Auto operation selected form system mode selection menu.
Drives healthy and remote selected from LCB, Stop PB not pressed for
drives of all groups as required by
programme.
3. Operation mode (Remote manual or AUTO)
Display of Local/ Remote selection of each mechanism, status of all inputs and outputs each
drive wise.
Each diagram should depict current status of each drive,ON/OFF/trip, etc.
4. Display of operation of Local Stop Push Button.
5. Display of Day, Date and time at the corner of VDU screen
6. Over views and sub-menus like command menu, report menu and so on.
a) Minic display of stoves.
b) Minic, bar graph trend of temperature pressure flow and utilities

7. PID Loop displays
Each PID loop depicts loop diagram, operation mode, set-point, process
value, PID valves, manipulated variables, etc. selectable as engineering units
or in percentage.
Sampling time (max) Pressure & flow - 250 Millie second
Temperature - 500 Millie second
8.Help screens for trouble shooting
OVERVIEWSCREENS
OVER VIEW
A) Stove Proper
This overview includes status of all the stoves together along with the display of process
parameters.
i) Stove No. 1
This overview includes display of all process monitoring parameters for stove 1.
ii) Stove No. 2
This overview includes display of all process monitoring parameters for stove 2.
iii) Stove No. 3
This overview includes display of all process monitoring parameters for stove 3.
A) Hot Blast System
Cold Blast System
Steam System
This overview includes display of all process monitoring parameters for the above 3 systems
B) BF Gas System
Combustion Air System
Cooling Water System >
This overview includes display of all process monitoring parameters for the above 3 systems
C) Control loops
This overview includes page-wise display of all control loops.

Trend display and History
Online trend display and history is available for all the process monitoring parameters The above
display also includes display of totalized flow for 9 Nos. of flow parameters
LOG Report Display
Log report display is provided for all process monitoring parameters.
.Alarms & Alarm Summary
Alarms are displayed at particular places on screen, as when they occur irrespective of what
is on display. Same is printed immediately with the help of alarm printer. The alarm message
flashes accompanied by beep sound. Once the fault is acknowledged, the flashing becomes
steady and audio signal is silenced. The fault remains on VDU screen, till same is rectified and
reset.
Apart from faults and process alarms, whenever time of operation of any of the mechanisms
or group operation exceeds the normal values (indicated in the cyclogram), alarm is
recorded and displayed.
Summary of faults/alarms for at least previous seven days is stored in PLC memory with text
description and time and date of occurrence. The summary of faults reflects every week,
month and year. Further, the summary includes description of fault, frequency of their
operation, number of times of the fault occurrence, time taken to rectify faults etc. It is also
possible to view and or print the alarm summary at any time. Alarm displays include list of
unacknowledged alarms.
Reports
Interactive query report and data maintenance is employed for unsophisticated computer
users and includes the following minimum features.
1. Log reports giving details of gas and steam consumption.
2. Shift-wise, daily, monthly, yearly report of individual fuel / steam consumption. The
report includes time operation of each stoves, change over times and so on.
3. Shift-wise, daily, weekly, monthly, yearly logging of faults for various mechanisms
reports, events, data and so on.

4. Configurable current value and periodic reports.
5. Plant event and alarm reports.
Trends

a. Display of Trend/history graphics of major process parameters with operator scalable X-
axis from 60 seconds to 24 hours (Past 24 hours history to be stored as 10 seconds value
for each variable).
b. Display of Trend/history graphics of major process parameters with operator scalable X-
axis from 8 hours to one Month (Past one Month history to be stored as 10 Minutes average
value for each variable).
c.Display of multiple trends on top of one another for comparison.
INSTRUMENTATION
The control room for stove complex houses the programmable logic controllers (PLC) system
and instrument panel for stoves. Instrumentation system in general is electronic based on 4-
20 mA DC signal output. The controller is microprocessor based having single loop integrity.
The principal advantages of the stove according to the present invention, also popularly
known as top fired stove, may be summarized as below:
1. Costs less, requires lesser installation space, requires moderate gas cleanliness and is
capable of achieving higher blast temperature (approximately 1250°C).
2. Buckling of combustion chamber towards checker work is eliminated. Direct
impingement of burner flame over the combustion chamber wall is also
eliminated.
3. Deformation and collapse of combustion chamber lining and requirement of
larger installation space associated with conventional stoves is eliminated.
4. Improvement of hot blast stove campaign life is achieved.
5. Facilitates saving through reduction in coke rate and ensures alternate fuel
injection(coal/tar/oxygen) possible at higher rates.
6. Applicable on Blast Furnaces of sizes ranging from 157m3 to 1700m3.
7. Suitable for green field projects as well as brown field projects.
The present invention has been described with reference to some drawings and preferred
embodiments, purely for the sake of understanding and not by way of any limitation and the
present invention includes all legitimate developments within the scope of what has been
described hereinbefore and claimed in the appended claims.

WE CLAIM
1. An improved stove for blast furnaces including a minor dome, at least one each of a
burner chamber, a conical portion, a checker chamber wall, blast furnace gas and
combustion air system, cold blast and hot blast system, waste gas main and chimney system
along with valves and controls all operatively connected to each other, wherein the burner(s)
is(are) provided at the top of the stove and said stove is top fired with welded material and
lining made up of indigenous ingredients such as herein described, whereby said stove is
reasonably cheap, requires moderate gas cleanliness, requires less installation space and is
adapted to achieve high blast furnace temperatures in the vicinity of 1250°C.
2. The improved stove as claimed in claim 1 wherein said stove is top fired with welded steel
construction lined with silica and alumina refractories and there exists hot blast outlet
beneath said conical portion, waste gas branch and cold blast main beneath said checker
chamber wall, all having lining such as herein described.
3.The improved stove as claimed in any preceding claim , wherein the upper part of said
checker chamber wall has the following layers, from the inner side to the outer side: 305mm
silica bricks(21), 5mm expanded polystyrene at the boundary of the former(19), 114mm
insulation bricks (Type-II)(20), 114mm insulation bricks (Type-IV)(ll), 75mm insulation
bricks (Type-IV)(18), 40mm insulation slab(17), 1mm oil paper(5) in the 114mm insulation
bricks (Type-IV) layer(ll), 75mm insulation bricks (Type-IV) layer(18) and 40mm
insulation slab(17), Ceramic wool(22) , middle part of said checker chamber wall has the
following layers from the inner side to the outer side : 230mm 62% Alumina bricks (25),
114mm insulation bricks(Type-IV)(ll), 75mm insulation bricks (Type-IV)(18), shell of hot
blast stove(23), lower part of said checker chamber wall has the following layers from the
inner side to the outer side : 230mm 45% Alumina bricks(13), 5mm expanded
polystyrene(19), 114mm insulation bricks(Type-III)(24), 75mm insulation bricks(Type-
IV)(18), 1mm oil paper(5) in the 75mm insulation bricks(Type-IV) layer(18) and 40mm
insulation slab layer(17).
4.The improved stove as claimed in claim 3, wherein checker chamber hole is designed to
have an optimum diameter, such as in the vicinity of 40mm to reduce clogging during
operation and checkers used in the checker chamber are of hexagonal shape with a system
dimension of 124 mm having twelve numbers of 40mm diameter hole.

5. The improved stove as claimed in any preceding claim , wherein said conical portion of
the stove exists between said burner chamber and said checker chamber, the hot face of
said portion consists of silica bricks backed by four insulating layers and the fourth layer is
40mm thick slab against 35% gunning castable.
6.The improved stove as claimed in any preceding claim, wherein said dome is of
hemispherical shape for better stability at high temperature and consists of two layers of
high alumina refractory bricks(62% Alumina/45% Alumina) backed by three layers of
insulation, 35%Alumina gunning castable and insulation slab.
7. The improved stove as claimed in any preceding claim, wherein said burner chamber is
equipped with blast furnace gas inlet and combustion air inlet having the following layers
from the inner side to the outer side in that order-114mm 45% Alumina Bricks(3), 25mm
insulation slab(4), lmmoil paper(5), and said burner is of ceramic origin constructed with
the combination of 62% and 45% Alumina bricks, the latter being backed up with SS steel,
insulation slab and 35% Alumina gunning castable.
8. The improved stove as claimed in any preceding claim, wherein said valves and the
recommended sizes and drives thereof are such as herein described, the sizing of the various
openings provided in the stove shell are selected on the basis of maximum
operating/working conditions likely to occur during stove operation and there are provided
suitable platforms at various elevations with climbing means for easy operation and
maintenance.
9. An improved stove system comprising a battery of at least three stoves as claimed in any
preceding claim, operatively connected to each other and to a programme logic
controller(PLC) for automatic control stove mechanisms and for remote manual operation of
stove mechanisms through human machine interface(HMI) station.
10. A method of fabricating an improved stove for blast furnaces including operatively
connecting a minor dome, at least one each of a burner chamber, a conical portion, a
checker chamber wall, blast furnace gas and combustion air system, cold blast and hot blast
system, waste gas main and chimney system along with valves and controls , wherein said
method further comprises installing the burner(s) at the top of the stove and top firing said
stove with welded material and lining made up of indigenous ingredients such as herein
described.

An improved stove for blast furnaces including a minor dome(A), at least one each of a
burner chamber(B), a conical portion(C), a checker chamber wall(D), blast furnace
gas(E) and combustion air system(F), cold blast and hot blast system, waste gas main
and chimney system along with valves and controls all operatively connected to each
other, wherein the bumer(s) is(are) provided at the top of the stove and said stove is top
fired with welded material and lining made up of indigenous ingredients such as herein
described, whereby said stove is reasonably cheap, require moderate gas cleanliness,
require less installation space and is adapted to achieve high blast furnace temperatures
in the vicinity of 1250°C. The present invention also includes a method of fabricating the
improved stove.