FIELD OF THE INVENTION
The present invention relates to a ladle cooling stand system adapted to use forced air
convection cooling of hot steel ladles. More particularly, the present invention relates to a
system for forced air-cooling of steel ladles after full life of campaign, needing cooling for
repair of working lining or relining. The cooling system of the ladle-cooling stand according
to the invention is capable of cooling of hot steel ladles of 130-300t capacity for changing of
working lining of such ladles used in steel melting shop and/or hot metal ladles used in Blast
furnace shop after full campaign life. Through forced air cooling, ladles are cooled very fast
such that cold air sweeps above the surface of refractory bricks of hot ladles kept under the
ladle cover in ladle cooling stand. The forced air convective heat transfer based air cooling
system enable cooling ladles heated to 1000°C-1200°C to working temperature within about
30 hrs as compared to 72hrs time by conventional natural air cooling. Advantageously, the
present ladle cooling system is particularly applicable for those steel ladles, which have cast
monolithic safety refractory lining in which water cooling is not permissible. The forced air
cooling system of the present ladle cooling stand is further beneficial for faster cooling of
hot ladles going for partial repair which otherwise takes about 50hrs to cool down to
working temperature. The present system and method of ladle cooling using forced air
convection cooling thus favour improving the ladle availability leading to reduction in the
number of circulation of ladles. The ladle cooling stand system for forced air cooling of large
steel ladles is thus capable of wide industrial application in steel melting shops/blast furnace
shop in integrated steel plants with reduced downtime for maintenance, reduced cost of
operation and hence improved productivity by longer availability of ladles in operation.
BACKGROUND ART
It is well known in the art of iron and steel production that steel ladles heated upto 1000 -
1200°C temperature requires cooling for its repair/relining after full life of campaign. The
hot ladles are cooled conventionally by natural cooling, which is a slow process and may
take about 60 - 70 hrs. Cooling by spraying water jet is also adopted for faster cooling. Hot
steel ladles used in steel melting shop or hot metal ladles used in Blast Furnace shop goes
for regular re-lining of working lining after its normal life. During re-lining process, generally
water spry is used for faster cooling of the ladles, which leads to damage of safety linings.
Thus, after every normal life of ladles, the safety lining as well as working linings needs to
be replaced for preparing the green ladles. However, ladles having safety lining of
monolithic casting cannot be cooled by water, in which case safety lining will be damaged.
Thus, ladles with safety lining of monolithic casting can only be forced air cooled for faster
cooling.
There has thus been a need in the art to develop a system for ladle cooling stand which
would provide means for faster cooling of steel ladles heated up to 1000°C to 1200°C for
large ladles used in steel melting shop or Blast furnace shop and after full campaign to
repair/reline with refractory by cooling them to working temperature using forced air
cooling. The ladle cooling stand would favour relining process to be completed in less time
increasing ladle availability and also save damages of the safety lining avoiding undesired
water cooling, particularly for cast monolithic safety lining.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to develop a system of ladle
cooling stand for forced air cooling of hot steels ladles adapted to faster and safer cooling of
hot ladles required for repair/relining of refractory lining after full campaign life.
Another object of the present invention is directed to develop said ladle cooling stand
system wherein a forced draft fan and an Induced draft fan is used in said system to
generate the required forced air circulation through the ladle for desired faster cooling.
A further object of the present invention is directed to develop said ladle cooling stand
system wherein ladle cover and inlet and outlet ducting/piping is used to direct required
forced air flow rate inside the ladle to cool the refractory lining to bring down the
temperature to working limits for repair/relining and remove the hot air to atmosphere.
A still further object of the present invention is directed to develop said ladle cooling stand
system wherein an indirect connection of cold air nozzle to the receiving duct is provided to
allow air entry to through ladle cover to facilitate the ladle cover swinging up and down
around the axis of the ladle cover lifting arm mechanism.
A still further object of the present invention is directed to develop said ladle cooling stand
system wherein to enhance the life of the ladle cover, it is thermally insulated with ceramic
fiber modules/blanket protected from falling due to mechanical abrasion, being held by
means of close spaced anchors.
A still further object of the present invention is directed to develop said ladle cooling stand
system wherein to limit the initial air temperature handled by the exhaust induced draft fan
below safe working limit of 300°C, atmospheric cold air is allowed to enter through a dilution
air pipe with butterfly valve to save damage of blades of ID fan.
A still further object of the present invention is directed to develop said ladle cooling stand
system wherein said system is designed to handle and FD as well as ID fan capacities or
ducting sizes are selected to maintain air flow rate, velocity and pressure sufficient to cool
ladles of 130-300t capacity within desired time.
A still further object of the present invention is directed to develop said ladle cooling stand
system wherein said ladle cooling stand system is capable to cool steel ladles heated up to
1000°C-1200°C is cooled to the working temperature using forced air cooling within 30 hrs
as compared to 72 hrs time in conventional natural circulation air cooling.
A still further object of the present invention is directed to develop said ladle cooling stand
system wherein hot air after cooling of the hot refractory lining of ladles is removed to the
safer height in the atmosphere through the hot air pipes of suitable size.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a ladle cooling stand system for
faster cooling of hot steel ladles by forced air convection, comprising
a forced draft fan to supply air at desired flow rate inside the hot ladle;
a ladle cover for covering a hot steel ladle placed in ladle stand for forced air cooling;
air inlet ducting to carry cold air from said forced draft fan to inside of ladle through
said ladle cover;
an air nozzle for supplying cooling air at high velocity to the ladle;
said nozzle movably connected to a cold air receiving duct connected to the ladle
cover through said air inlet ducting;
said ladle cover comprising an inlet air header;
hot air outlet ducting to remove hot air from inside the ladle through hot air main
header to which said outlet ducting is connected;
an induced draft fan for sucking out hot air from ladle to safer height in the
atmosphere through said hot air pipe/ducting;
Another aspect of the present invention is directed to said ladle cooling stand system
wherein said forced draft fan is of capacity of 25,000-60,000 Nm3/hr at a delivery pressure
of400-600mm WC.
In said ladle cooling stand system, the said air nozzle is adapted to supply cold air at a
velocity of 40-60m/sec.
Also in said ladle cooling stand system wherein said inlet ductings are two in numbers
connected to the ladle cover for supply of cold air to the ladle.
A further aspect of the ladle cooling stand system, wherein the cold air flows to the ladle
kept under cover through an air header box provided in the ladle cover, on the hot face of
ladle lining.
A still further aspect of the present invention is directed to said ladle cooling stand system,
wherein said air inlet nozzle for supplying cold air is adapted to provide an indirect
connection to the cold air receiving duct to allow for swinging up and down movement of the
ladle cover around the axis of the ladle cover lifting arm mechanism.
A still further aspect of the present invention is directed to said ladle cooling stand system
wherein a pressure gauge is provided at outlet of forced draft fan to measure the cold air
supply pressure.
According to yet another aspect of the present invention directed to said ladle cooling stand
system wherein, said induced draft fan is of suction capacity of 30,000-70,000Nm3/hr at
200-300mm WC.
Further in said ladle cooling stand system according to the present invention, the impeller of
the induced draft fan is adapted for hot air temperature of 300°C (Max).
A still further aspect of the present invention is directed to said ladle cooling stand system,
wherein said hot air outlet duct are two in numbers connected to the ladle cover to evacuate
the hot air from ladle.
In said ladle cooling stand system, wherein the hot air ducts are connected to the hot main
air header to facilitate the movements of ladle cover.
According to yet another aspect of the present invention a ladle cooling stand system,
wherein a dilution air pipe is connected to the hot air main header and a butterfly valve of
suitable size provided in said dilution air pipe which remains opened during start up of ladle
cooling to allow atmospheric cold air entry to control the hot air temperature below 300°C to
avoid damage of impeller of ID fan.
Advantageously, said ladle cooling stand system of the present invention, wherein said
cooling system is suitable for those steel ladles which have cast monolithic safety refractory
lining in which water cooling is not permissible.
A still further aspect of the present invention directed to said ladle cooling stand system,
wherein the life of the ladle cover is enhanced by thermally insulating it with ceramic fiber
modules/blanket, protected from falling due to mechanical abrasion, being held by means of
close spaced anchors.
According to an advantageous aspect of the present invention directed to said ladle cooling
stand system adapted for cooling hot steel ladles of 130-300t capacity heated up to 1000-
1200°C, cooled to working temperature by about 30 hrs time.
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 schematic illustration of the equipments and piping layout for the FD fan of
ladle cooling stand system according to the present invention.
Figure 2: is the schematic illustration of the equipments and piping layout for the ID fan of
ladle cooling stand system according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to a ladle cooling stand system used for cooling of ladles by
forced air convection system and in particular for ladles with cast monolithic refractory
safety lining for which water cooling is not permissible. Through forced air cooling, cold air
sweeps above the surface of refractory bricks of hot ladle kept under the ladle cover in the
ladle cooling stand such that ladles are cooled very fast. The steel ladles heated up to
1000°C-1200°C temperature after full life of campaign requires cooling for repair of its
lining.
In forced convection, the heat transfer between a solid boundary and a fluid takes place by
a combination of convection and mass transport. If the boundary is at a higher temperature
than the fluid, heat flows first by conduction from the solid to fluid particles in the
neighborhood of the wall. The energy thus transmitted increases the internal energy of the
fluid and is carried away by the motion of the fluid. The fluid velocity becomes zero at the
interface of solid and fluid. The heat transfer coefficients for laminar flow are considerably
smaller than turbulent flow. In turbulent flow, all the molecules in the flowing fluid move in
a very random manner. They transfer the momentum and energy from one place to another
by mixing the fluid. As the molecules move with highly fluctuating velocities, the rate of
heat transfer is very high as compared with laminar flow. Thus, overall rate of heat transfer
in the forced convection is much faster than that in natural convection. The ladle cooling
stand thus uses the forced air cooling as a means for faster cooling of hot ladle withdrawn
from production shop for relining.
Reference is first invited to the accompanying Figure 1 that schematically illustrates the
equipments and ducting for the FD fan used in the ladle cooling stand system of the present
invention. The ladle cooling stand system comprising one ladle cover, a forced draft (FD)
fan, an induced draft (ID) fan and pipe ducts, valves and pressure gauges. The airflow from
the forced draft fan is blown on the hot face of ladles. For this, a special ladle cover is
designed having a facility to blow cold air coming from the forced draft fan on the hot face
of ladle lining kept under the cover. The air becomes hot after impinging on the hot face of
the ladle refractory lining. An induced draft fan is provided to remove hot air from ladle to
the atmosphere above the safe height. For this, a hot air exit duct is provided in the
specially designed ladle cover. Further, the hot air is ducted out through a flue duct above a
safe height.
According to an embodiment of the ladle cooling stand of the present invention comprises a
Forced Draft (FD) fan (1) for supplying cold air though the pipeline/ducting of suitable size
(2) to a ladle cover (3). Since the ladle cover (3) swings up and down around the axis of the
ladle cover lifting arm mechanism, the direct connection to the ladle cover is not possible. A
suitable air nozzle (4) is designed to supply air at higher velocity to ladle cover (3) through
the cold air receiving duct (5) and two numbers of air inlet duct (6) provided in the specially
designed ladle cover of circular cross section. Cold air flows to the ladle through the air
header box (7) provided in the ladle cover. The cold air entry nozzle (4) provided in the
ladle cover facilitates the blowing of cold air coming from the air header box on the hot face
of ladle refractory lining kept under the cover.
A pressure gauge (8) has been provided at outlet of FD fan to know the cold air pressure.
To enhance the life of ladle cover, it is insulated with ceramic fibre module/blanket. The
spacing between the anchors is kept closer to prevent falling of fibre due to mechanical
abrasion. To enhance the life of ceramic fibre blanket, studs of AISI - 310 grade are welded
on inside face of the ladle cover.
Reference is now invited to the accompanying Figure 2 that schematically illustrates the
arrangement of equipments and ducting for the ID fan used in the ladle cooling stand
system of the present invention. Two numbers hot air duct of suitable size (9) are
connected to the ladle cover to evacuate the hot air from the ladle. Since, direct pipeline
connection for removing out the hot air from ladle to the atmosphere cannot be provided to
allow for the ladle cover movement, two numbers of suitable hot air ducts (10) are designed
and connected to hot air main header (11) and an induced draft fan (12). Now, hot air is
removed to the safer height in the atmosphere through the hot air pipe of suitable size (13)
under the action of desired induced draft created by the ID fan.
To measure the temperature of hot air ducted out from ladle to the induced draft fan, a
temperature gauge (14) is provided in the hot air main header (11). The impeller of the
induced draft fan is designed for the hot air temperature of 300°C (Max.). A butterfly valve
of suitable size (15) is provided in the dilution air pipe (16) connected to the hot air main
header (11). During start-up of ladle cooling, there is possibility of hot air temperature
going beyond 300°C. Hence, the butterfly valve needs to be opened to allow atmospheric
cold air entry to control the hot air temperature below 300°C, thereby avoiding the damage
of impeller of induced draft fan.
The ladle cooling stand of the present invention is designed for cooling of 130t - 300 t ladle
capacity. The system has a commensurate cold air supply capacity at a velocity of 40 - 60
m/sec through the air nozzle with the capacity of forced draft fan rated at 25,000 - 60,000
Nm3/hr. The air delivery pressure of forced draft fan is 400 - 600 mm WC. The suction
capacity of the induced draft is 30,000 - 70,000 Nm3/hr at 200 - 300 mm WC. The forced
air circulation so created is capable to cool 130 t capacity hot ladle from 1000-1200°C to
working temperature by about 30 hrs time, as compared to 70-72 hrs time taken by
conventional natural circulation cooling. Instruments like, air pressure gauges at the outlet
of FD fan know the cold air pressure and temperature gauge provided in the inlet of ID fan
to record and monitor the safe operating temperature to ensure safe operation as well as
longer operating life of the ladle cover and impeller of ID fan.
The ladle cover (3) is fabricated of Boiler grade steel plate (IS 2002:1992), while remaining
portions of the ducting or nozzle is fabricated from mild steel.
It is thus possible by way of the present invention to developing a ladle cooling stand
system wherein ladles of 130t-300t capacities can be cooled to working temperature by
forced air convection cooling by flowing cold atmospheric air at desired volumetric rate to
cool the refractory lining heated up to 1000°C-1200°C to working temperature for necessary
repair/relining of the working lining, partial lining or total relining. The ladle cooling stand
system attains faster cooling of ladles by forced air convective heat transfer involving a FD
fan, an ID fan, air ducting and inlet flow nozzle and a hot air exhaust duct arranged in said
system providing desired cooling rate by turbulent air flow impinging on the hot refractory
lining of ladle at desired velocity and pressure, eliminating the need for water cooling. The
cooling time has been substantially reduced from existing 70-72 hrs by conventional natural
convection cooling to about 30 hrs to cool hot ladle to working temperature. The forced air
convective cooling according to the present invention is thus particularly beneficial for cast
monolithic safety lining of steel ladles to thereby avoiding damage of such lining due to
conventional water cooling. The ladle cooling stand involving force air convection system
according to the invention is thus having prospect of wide scale application for ladle cooling
in the steel melting shop or the blast furnace shop in steel plants.
We Claim:
1. A ladle cooling stand system for faster cooling of hot steel ladles by forced air
convection, comprising
a forced draft fan to supply air at desired flow rate inside the hot ladle;
a ladle cover for covering a hot steel ladle placed in ladle stand for forced air cooling;
air inlet ducting to carry cold air from said forced draft fan to inside of ladle through
said ladle cover;
an air nozzle for supplying cooling air at high velocity to the ladle;
said nozzle movably connected to a cold air receiving duct connected to the ladle
cover through said air inlet ducting;
said ladle cover comprising an inlet air header;
hot air outlet ducting to remove hot air from inside the ladle through hot air main
header to which said outlet ducting is connected;
an induced draft fan for sucking out hot air from ladle to safer height in the
atmosphere through said hot air pipe/ducting;
2. A ladle cooling stand system as claimed in claim 1, wherein said forced draft fan is of
capacity of 25,000-60,000 IMm3/hr at a delivery pressure of 400-600mm WC.
3. A ladle cooling stand system as claimed in any one of claims 1 or 2, wherein the air
nozzle is adapted to supply cold air at a velocity of 40-60m/sec.
4. A ladle cooling stand system as claimed in anyone of claims 1 to 3, wherein said inlet
ducting are two in numbers connected to the ladle cover.
5. A ladle cooling stand system as claimed in anyone of claims 1 to 4, wherein the cold
air flows to the ladle kept under cover through an air header box provided in the
ladle cover, on the hot face of ladle lining.
6. A ladle cooling stand system as claimed in anyone of claims 1 to 5, wherein said air
inlet nozzle for supplying cold air is adapted to provide an indirect connection to the
cold air receiving duct to allow for swinging up and down movement of the ladle
cover around the axis of the ladle cover lifting arm mechanism.
7. A ladle cooling stand system as claimed in anyone of claims 1 to 6, wherein a
pressure gauge is provided at outlet of forced draft fan to measure the cold air
supply pressure.
8. A ladle cooling stand system as claimed in anyone of claims 1 to 7, wherein said
induced draft fan is of suction capacity of 30,000-70,000Nm3/hr at 200-300mm WC.
9. A ladle cooling stand system as claimed in anyone of claims 1 to 8, wherein the
impeller of the induced draft fan is adapted for hot air temperature of 300°C(Max).
10. A ladle cooling stand system as claimed in anyone of claims 1 to 9, wherein said hot
air outlet duct are two in numbers connected to the ladle cover to evacuate the hot
air from ladle.
11. A ladle cooling stand system as claimed in anyone of claims 1 to 10, wherein the hot
air ducts are connected to the hot main air header to facilitate the movements of
ladle cover.
12. A ladle cooling stand system as claimed in anyone of claims 1 to 11, wherein a
dilution air pipe is connected to the hot air main header and a butterfly valve of
suitable size provided in said dilution air pipe which remains opened during start up
of ladle cooling to allow atmospheric cold air entry to control the hot air temperature
below 300°C to avoid damage of impeller of ID fan.
13. A ladle cooling stand system as claimed in anyone of claims 1 to 12, wherein said
cooling system is suitable for those steel ladles having cast monolithic safety
refractory lining in which water cooling is not permissible.
14. A ladle cooling stand system as claimed in anyone of claims 1 to 13, wherein the life
of the ladle cover is enhanced by thermally insulating it with ceramic fiber
modules/blanket, protected from falling due to mechanical abrasion, being held by
means of close spaced anchors.
15. A ladle cooling stand system as claimed in any one of claims 1 to 14 is adapted for
cooling hot steel ladles of 130-300t capacity heated up to 1000°C-1200°C cooled to
working temperature by about 30 hrs time.
16. A ladle cooling stand system for faster cooling of hot steel ladles by forced air
convection as hereindescribed with reference to the accompanying non limiting
figures.

A ladle cooling stand system adapted to use forced air convection cooling of hot steel ladles,
for repair of working lining or relining after full life of campaign. The ladle-cooling stand
system is capable of cooling hot steel ladles of 130-300t capacity. The system uses forced
air convection cooling of ladles for faster cooling wherein cold air sweeps above the surface
of refractory bricks of hot ladles kept under the ladle cover in ladle cooling stand. The forced
air convective heat transfer based air cooling system enable cooling ladles heated to
1000°C-1200°C to working temperature within about 30 hrs as compared to 72hrs time by
conventional natural air cooling. Advantageously, the system can cool steel ladles, which
have cast monolithic safety refractory lining in which water cooling is not permissible. The
ladle cooling using forced air convection thus favour improving the ladle availability leading
to reduction in the number of circulation of ladles favouring wide industrial application in
steel melting shops/blast furnace shop in integrated steel plants.