FIELD OF THE INVENTION
The present invention relates to gas burners and, in particular, to producer gas burners
for reheat furnaces adapted to generate high flame temperature by way of high thrust so
that the flame and hot gases can sweep above the surface of the metal stock e.g. while
used for heating the metal billets/ pencil ingots inside the reheating furnace.
Advantageously, the high thrust flame generated by the burner according to the
invention further ensures proper and uniform heating of stock to desired temperature.
Importantly, the present invention directed to said improved configuration of the
producer gas burner adapted to attain high and uniform thrust flame temperature
favouring better mixing of fuel gas and air for combustion and thereby achieving proper
anchoring/stabilizing the flame. This configuration ensures minimum level of oxygen in
flue gas resulting in higher flame temperature. Importantly, the burner of the invention
achieves desired stabilization of the flame even at very low gas flow rate. The improved
producer gas burner of the present invention is thus adapted to generate stable uniform,
high thrust and high temperature flame for desired heating of the billet/ingot in reheating
furnace, is advantageously simple in construction, yet highly fuel efficient conserving
energy and therefore having prospects of wide industrial application in steel plants or
downstream application.
BACKGROUND ART
It is an well known requirement for the reheat furnaces utilizing producer gas for the
heating/soaking of cast metal billets /pencil ingots or further down stream processing,
that the flame temperature is of important consideration. The existing system utilized
conventional combustion system comprising burners without provision for
adequate/exact excess air supply for the producer gas having a specific calorific value
used as fuel in burners which are incapable to ensure stable flames with consistently high
temperature and thrust, due to lack of control on flow parameters and pressure of gas
and excess combustion air for a given calorific value of fuel gas and thus leading to either
variation of flame temperatures or incomplete combustion leading to inefficiency of the
combustion system.
There has been therefore a continuous need for developing an improved burner with
provision for adequate control on supply of producer gas as fuel and excess combustion
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air maintaining required optimum air fuel ratio, desired supply pressure and means for
thorough mixing of the gas-air mixture so as to obtain desired high temperature and high
thrust flames generated by the burners having specially configured air and gas nozzle
with devices for measurement and control on flow rates of air/fuel and the respective
supply pressure, corresponding to a specific Calorific Value of gas and a mixing means in
said burner adapted to heating of billets and ingots for proper and uniform heating of the
metal stock in reheating furnace with improved thermal/energy efficiency.
OBJECTS OF THE INVENTION
It is therefore the basic object of the present invention to provide for an improved
producer gas burner adapted to generate high temperature flames uniformly with high
thrust so that the flames and hot gases sweep above the furnace of the metal stock e.g.
metal billet/pencil ingots in reheat furnace, for proper and uniform heating of stock in
reheating furnace.
Another object of the present invention directed to an improved producer gas burner for
reheat furnace wherein the burner is provided with a swirler involving means for better
mixing of gas and air and thereby proper anchoring/stabilizing the flame, obtainable even
at very low gas flow rate and even at very high gas flow rate especially at cold condition.
A still further aspect of the present invention is directed to provide for an improved
producer gas burner adapted to generate high temperature high thrust flames for
uniform heating of metal stock in reheat furnace comprising a combustion air nozzle
communicating operatively with said gas nozzle, such that requisite amount of air is
supplied receiving through air connecting pipe and air inlet pipe to a means for thorough
mixing with the producer gas ensuring complete combustion of fuel gas and maintain
desired uniform high thrust and high temperature flames for heating of stock in the
reheating furnace.
A still further object of the present invention directed to provide for an improved
producer gas burner adapted to generate high temperature and high thrust flames, is
control the respective supply pressure and flow rate for the producer gas and the
combustion air by means of control valves provided in the respective inlet pipes of gas
and air to the nozzles of the burner.
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According to another object of the present invention directed to said improved producer
gas burner adapted for uniform high temperature and high thrust flame wherein said
high velocity burner is capable of burning producer gas having calorific value in the range
of about 1000-1200 Kcal/Nm3 with a burning capacity of 100-500 Nm3/hr, the gas being
supplied at a pressure in the range of 50-250mmWC.
According to yet another object of the present invention directed to said improved
producer gas burner adapted for uniform high temperature and high thrust flame wherein
the combustion air is supplied from a air blower, preheated to 250°C maintaining the
supply pressure in the range of 800-1000mmWC and the excess combustion air level is
kept at 10%, ensuring complete combustion and consistent high uniform flame
temperature.
A still further object of the present invention directed to said improved producer gas
burner for uniform heating of metal stock in reheating furnace wherein the supply system
for air and gas to the respective nozzles of the burner, connected through the connector
and inlet pipes, each of which are provided with required instruments e.g. a separate
orifice plate, pressure gauges, differential pressure transmitter and flow indicator, for
achieving and maintaining desired measurement and controlled level of said flow and
pressure parameters in order to ensure optimum air fuel ratio for complete combustion of
producer gas and generate consistent uniform high temperature flames with high thrust.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a gas
burner adapted for stabilizing the flame even at low gas flow rates comprising:
a gas inlet pipeline operatively connected to a gas nozzle;
a combustion air pipeline operatively connected to a combustion air nozzle; and
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an air adapted to stabilize the flame even at very low gas flow rate and at cold
condition, especially at very high gas flow rate and at cold condition, especially at
very high gas flow rate.
In accordance with a preferred aspect of the invention there is provided a gas burner for
producer gas burning adapted for stabilizing the flame even at low gas flow rates
comprising:
a producer gas pipeline operatively connected to a producer gas outlet nozzle;
a combustion air pipeline concentrically disposed over said producer gas pipeline
and having a operatively connected combustion air outlet nozzle; and
a swirler tube provided over said combustion air nozzle and supporting theron a
swirler near the exit for stabilizing the flame even at very low gas flow rate.
In the above disclosed gas burner of the invention the gas is supplied to gas connecting
pipeline through a mild steel inlet pipe.
In accordance with another aspect of the invention, the burner is supported on a burner
holding pipe which is welded to a shell plate of the furnace with the gas nozzle part and
air nozzle part inserted inside the burner block of refractory materials.
Advantageously, the gas burner further comprises a valve in the gas inlet pipe to the
burner to control the flow of gas and a control valve provided in the combustion air inlet
pipe to the burner.
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Importantly, the gas burner of the invention is adapted for combustion of producer gas
having calorific value in the range of 1000-1200 Kcal/Nm3 depending upon the quality of
coal used for gasification with a firing capacity of 100-500Nm3/hr while the gas supply
pressure is in the range of 50-250mmWC.
Also, preferably in the gas burner of the invention, the combustion air is supplied
through a combustion air blower, the supply pressure of the combustion air blower
being about 800-1000 mmWC with excess combustion air kept at about 10% and air
is preheated upto 250°C.
Advantageously, the provision of the swirler means is adapted such as to achieve the
burner turn down ratio of 1:10.
The details of the invention, its objects and advantages are explained hereunder in
greater detail in relation to non-limiting exemplary illustration as per the following
accompanying figure:
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1: is the illustration of the schematic arrangement of the Producer Gas Burner
according to the invention along with air and gas nozzle and their inlet connections and
mounting of the burner in burner block of refractory material in reheating furnace.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURE.
The present invention relates to an improved configuration of the producer gas burner
adapted for heating the metal billets/pencil ingots inside the reheating furnace with
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controlled supply of fuel gas and combustion air to said burner to obtain desired flame
characteristics and stable high temperature for uniform heating of metal stock. It is well
known in the art that such heating process requires very high thrust flame so that the
flame and hot gases can sweep above the surface of the metal stock such that the proper
and uniform heating of stock is ensured. The high flame temperature has also significant
impact for obtaining high furnace temperature. The flame temperature is a function of
Calorific value of the gas composition and the level of excess air used to correctly
determine and ensure complete combustion of fuel. It is thus essential to achieve
optimum air/fuel mixture to achieve high flame temperature for proper and uniform
heating of the metal stock to high temperatures according to the need of the process
variables. The appropriate air fuel ratio is achieved for a particular calorific value of fuel
by controlling the various flow parameters installed in the gas-air supply system
connected to the burner through inlet pipes, by adjusting the air and gas flow rates to
ensure desired excess air required for complete combustion, stable flame generation and
attaining consistent high temperature in reheat furnace.
Reference is now invited to the accompanying Figure 1 that illustrates the schematic
arrangement of the improved configuration of the producer gas burner for heating metal
stock in reheat furnaces. In the present improved configuration of the producer gas
burner, according to an embodiment of said burner adapted to generate stable flames
having high thrust and uniform high temperature, involving selective use of a swirler for
better mixing of the air and gas and thereby anchoring/stabilizing the flame. This
arrangement ensures maintaining minimum level of Oxygen in flue gas by way of
complete combustion and thus providing high stable flame temperature. The improved
performance and combustion efficiency of the burner according to the present invention
and the manner of achieving the high temperature and high thrust flames by burning of
producer gas maintaining proper air fuel ratio can be explained with the help of said
accompanying Figure 1. The burner of the invention comprising a gas nozzle(l) for gas
emerging out of nozzle and firing in flame when mixed with air, being lighted with a
flame torch or a pilot burner. A swirler(2) has been provided over the swirler tube(3)
near the exit of the nozzle/burner to stabilize the flame even at very low gas flow rate.
The swirler is also provided for favored flame stabilization at cold condition especially at
very high flow rate of gas. This swirler is capable of creating a re-circulation zone for
efficient combustion of gaseous fuel near the discharge tip of gas nozzle. The swirler also
helps achieving favored burner turn down ratio in the order of 1:10. The burner tip and
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adjacent portion comprising the gas nozzle(l), the swirler(2), the swirler tube(3) and the
combustion air nozzle(5) are components fabricated from AlSI-St 310 grade steel
material to derive longer service life. The remaining portion of the burner is fabricated
from the ordinary grade weldable structural steel.
A gas-connecting pipe (4) is connected with the gas nozzle to supply gas at desired flow
rate and desired pressure. The gas is supplied to the gas connecting pipe(4) through a
mild steel inlet pipe, connected with flanged joint with said gas connecting pipe portion of
burner. The producer gas is supplied to the burner at a pressure range of 50-250mmWC.
A combustion air nozzle(5) has been provided and is connected to air connecting pipe(6)
to supply the requisite amount of air flow for complete combustion of the gas. The air
connecting pipe(6) is connected to air inlet pipe(7). A burner holding pipe(8) is welded to
the shell plate of the furnace for mounting and holding the burner securely while installed
on furnace. The gas nozzle (1) and the air nozzle (5) are inserted inside the burner block
of refractory material (9). The combustion air is supplied from a combustion air blower
through the air inlet and air connecting pipe to the Burner nozzle at a selective pressure
range of 800-lOOOmmWC. The air supplied may be preheated up to a temperature of
250°C.
To obtain desired flow rates, control valves have been provided in the gas inlet pipe to
the burner and the combustion air inlet pipe to the burner to obtain optimum air fuel
ratio through operative control of said valves ensuring an excess air level of about 10%,
favoring complete combustion of producer gas and thereby obtaining high flame
temperature. The additional instruments like orifice plate, pressure gauge, differential
pressure transmitter and flow indicators are provided on each of gas and the combustion
air supply inlet/connecting pipes. These instruments facilitate required measurement and
controlled supply of the producer gas and combustion air to optimize the air-fuel ratio to
obtain selective 10% of excess air supply to achieve desired complete combustion and
thereby maximize the flame temperature in a stable and consistent manner, economizing
reheating operation for metal stocks.
The improved configuration of the burner having high thrust/velocity of flame is designed
for combustion of producer gas having Calorific value in the range of 1000-1200
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Kcal/Nm3, depending upon the quality of coal used for gasification. The firing capacity
achieved from the present high velocity gas burner is in the order of 100-500 Nm3/hr,
such as to obtain stable high flame temperature in the range of 1500 to 1600°C, so as to
favor obtaining uniform heating of the metal stock in the reheat furnace in the desired
temperature range of 1200 to 1250°C.
It is thus possible by way of this invention to achieve producer gas burner for reheating
furnace for desired heating of metal billets and or pencil ingots at high temperatures for
further treatment/forming by providing high thrust and high temperature flames
generated at the burner tip ensuring complete combustion of fuel gas with appropriate
supply of excess air. The burner of the system is further adapted to provide desired flow
rate and supply pressure of gas and combustion air in controlled manner through a
number of control instruments. The producer gas burner according to the present
invention is simple in construction and cost effective to produce, yet highly energy
efficient in operation and thereby economizing on fuel utilization and maintaining desired
stable high temperature of the metal stock in reheating furnace, having wide application
in steel plants or the like down stream operations.
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WE CLAIM:
1. A gas burner adapted for stabilizing the flame even at low gas flow rates
comprising:
a gas inlet pipeline operatively connected to a gas nozzle;
a combustion air pipeline operatively connected to a combustion air nozzle ;and
an air swirler adapted to stabilize the flame even at very low gas flow rate and at
cold condition, especially at very high gas flow rate also.
2. A gas burner for producer gas burning adapted for stabilizing the flame even at
low gas flow rates comprising:
a producer gas pipeline operatively connected to a producer gas outlet nozzle;
a combustion air pipeline concentrically disposed over said producer gas pipeline
and having a operatively connected combustion air outlet nozzle; and
a swirler tube over said combustion air nozzle and supporting theron a swirler
near the exit for stabilizing the flame even at very low gas flow rate.
3. A gas burner as claimed in anyone of claims 1 or 2 wherein the gas is supplied to
gas connecting pipeline through a mild steel inlet pipe.
4. A gas burner as claimed in anyone of claims 1 to 3 wherein the burner is
supported on a burner holding pipe which is welded to a shell plate of the furnace
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with the gas nozzle part and air nozzle part inserted inside the burner block of
refractory materials.
5. A gas burner as claimed in anyone of claims 1 to 4 comprising a valve means in
the gas inlet pipe to the burner to control the flow of gas and a control valve
provided in the combustion air inlet pipe to the burner.
6. A gas burner as claimed in anyone of claims 1 to 5 adapted for combustion of
producer gas having calorific value in the range of 1000-1200 Kcal/Nm3
depending upon the quality of coal used for gasification with a firing capacity of
100-500Nm3/hr while the gas supply is in the range of 50-250mmWC.
7. A gas burner as claimed in anyone of claims 1 to 6 wherein the combustion air is
supplied through a combustion air blower, the supply pressure of the combustion
air blower being about 800-1000 mmWC with excess combustion air kept at about
10% and air preheated upto 250°C.
8. A gas burner as claimed in anyone of claims 1 to 7 comprising said swirler means
adapted for burner turn down ratio of 1:10.
9. A gas burner for producer gas burning substantially as herein described and
illustrated with reference to the accompanying figures.


Dated this the 22nd day of February, 2008

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The invention is directed to producer gas burners for reheat furnaces adapted to
generate high flame temperature by way of high thrust flame and hot gases that sweep
above the metal stock e.g. metal billets/ pencil ingots inside the reheating furnace.
Advantageously, the high thrust flame further ensures proper and uniform heating of
stock to desired temperature. Importantly, the improved configuration of the producer
gas burner adapted to attain high and uniform thrust flame temperature, better mixing of
fuel gas and air for combustion and thereby achieving proper anchoring/stabilizing the
flame through a swirler. Importantly, the burner of the invention achieves desired
stabilization of the flame even at very low gas flow rate and minimum level of oxygen in
flue gas, resulting in higher flame temperature. The gas burner is thus adapted to
generate stable uniform, high thrust and high temperature flame in reheating furnace, is
simple in construction, yet highly fuel efficient conserving energy and therefore having
prospects of wide industrial application in steel plants or downstream application.