FIELD OF THE INVENTION
The present invention relates to a lean gas burner of high volumetric capacity. More
particularly, the present invention is directed to providing a lean gas burner adapted
to efficiently utilize low calorific value combustible gas (Lean gas) like blast furnace
gas (calorific value ~ 780 Kcal/Nm3). Importantly, the lean gas burner according to
the present invention comprises rectangular shaped gas slot(s) of suitable
dimensions worked out in a gas distributor within the burner body adapted to split
the lean gas stream into multiple rectangular and identical lean gas streams that
travels horizontally parallel to the burner axis, and an air distributor which is also
rectangular in shape adapted to distribute air stream uniformly over these gas
streams to facilitate rapid mixing of gas and air streams at the burner nozzle to
generate stable flame with lean gas. The rectangular gas slots are arranged in
selective number of columns and rows that ensures each gas stream coming out
from gas slots at the burner front is surrounded by air stream from all the four sides.
Advantageously, the lean gas burner according to the invention is suitable for rapid
mixing of gas and combustion air at low combustion air pressure (50-70mmWC) to
generate desired stable flame with lean gas. The burner of the present configuration
do not require any refractory checker work or premix of gas and air inside burner
body, eliminating any maintenance of refractory checker work and ensuring
improved burner availability for burning surplus BF gas to generate steam or power
favouring wide scale application and use of such burner in industry.
BACKGROUND ART
Low calorific value combustible gas (Lean gas) like blast furnace gas (calorific value
~ 780 Kcal/Nm3) is generated as by-product gas in the Blast Furnaces (BF) of Iron
and Steel Industries in large quantity. Most of the BF gas generated in Steel plant is
gainfully utilised by burning it in a combustion chamber of boiler at a high volumetric
flow rate to produce steam.
Lean gas like blast furnace (BF) gas does not burn easily. Lean gas requires rapid
mixing with combustion air for generation of stable flame. To burn blast furnace gas
in large quantity, it requires fast, uniform as well as thorough mixing of gas and air
to attain desired flame configuration.

It is therefore the first and foremost requirement for design of high capacity low
calorific value gas burner to ensure fast and thorough inter-mixing between gas and
combustion air with minimum excess air at burner to generate stable flame.
According to the known configuration of gas burners, inter mixing of gas and
combustion air is facilitated by tangential entry of air and/or gas streams to the
burner. Use of swirlers in air and/or gas passages is also commonly known in the
existing art to facilitate rapid mixing. In both the cases air and/or gas flow is
turbulised in the burner nozzle by imparting swirling / whirling motion to gas or air
stream. The curved or spiral path, followed by air or gas stream causes higher
hydraulic resistance in gas or air path and hence requires higher gas or air pressure
for their flow. Apart from this, air stream is sent to the burner in separate parts like
primary air, secondary air, tertiary air etc. for higher inter-facial contact area
between gas and air streams for better mixing. Tangential gas or air entry or
provision of swirler (made of vanes) in gas or air line is possible only in circular type
of gas or air pipe. Hence most of the BF gas burners existing in the art are of
cylindrical shape. In rectangular shaped gas or air passage, tangential entry of gas
or air is not possible to create swirling / whirling motion in gas or air stream for
better inter mixing of gas-air. It is also not possible to provide swirler in rectangular
gas or air passage. In the existing technology, either a refractory checker work is
provided in front of rectangular shaped burner mouth for pre-mixing of gas and air
or metallic premixing chamber is provided in the burner itself. Failure/damage of
such refractory checker work needs frequent maintenance causing increased
downtime of burner and poor utilization of BF gas.
There has been thus a continuing need in the art to developing a lean gas burner
adapted to utilize low CV BF gas which would avoid the difficulties and limitations of
the existing burners with cylindrical configuration by providing rectangular flow
passages for thorough intermixing of gas and air and more importantly ensuring
diffusion of gas into combustion air and vice versa to achieve fast and uniform
mixing between gas and combustion air to attain desired flame stability. The burner
system would have simple and cost effective configuration, eliminating the
requirement of refractory checker work or a metallic premixing chamber within the
burner body while ensuring maintenance free longer operation with efficient high
capacity burning of BF gas.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
arranged in row and column in selective numbers adapted to ensure quick and
thorough mixing of lean gas with combustion air and generating stable and firmly
anchored flame at the burner nozzle while burning lean/low calorific value gas such
as blast furnace gas at high volumetric flow rate.
Another object of the present invention is directed to providing a high capacity
rectangular section lean gas burner favouring desired lean gas distribution through a
gas distributor to split the lean gas stream into multiple rectangular and identical
lean gas streams through rectangular shaped gas slot(s) of suitable dimensions
worked out within the burner body and an air distributor which is also rectangular in
shape and adapted to distribute air stream uniformly over the said gas streams for
desired fast and through mixing.
A further object of the present invention is directed to providing a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
wherein each of the lean gas stream, issuing through the individual gas slots, is
completely surrounded by combustion air stream at the burner nozzle.
A still further object of the present invention is directed to providing a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
wherein the lean gas burner need no involvement of any refractory checker work or
pre-mixing of gas and air in the burner.
A still further object of the present invention is directed to providing a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
through which adjacent gas and air streams flow parallel to the axis of the burner for
increased interfacial area to ensure uniform mixing of gas and air to generate stable
flame.
Yet another object of the present invention is directed to providing a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
which would ensure fast and uniform mixing of lean gas and combustion air for
desired flame configuration which can be achieved even with very low combustion air
pressure of only about 50-70 mm WC near the burner.
A further object of the present invention is directed to providing a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
which would ensure fast and uniform mixing of lean gas and combustion air for
desired flame configuration which can be achieved with BF gas pressure in the range
of 400-500 mm WC.
A still further object of the present invention is directed to providing a high capacity
rectangular section lean gas burner with multiple rectangular gas slots/air passages
which would ensure fast and uniform mixing of lean gas and combustion air for
desired flame stability which would involve burner turn down ratio of 1:4.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a high capacity burner for
lean gas comprising
a gas distributor comprising a gas inlet operatively connected to plurality of gas
distributing passages formed therein adapted to split the lean gas into plurality of
lean gas streams emanating through said gas distributing passages such that the
lean gas travels horizontally along the burner axis;
an air distributor enclosing the said gas distributor having an air inlet and adapted
to distribute combustion air stream through plurality of passages such that each gas
stream coming out from gas distributing passages at the burner front is surrounded
by air streams from all the four sides facilitating diffusion of gas into air and vice-
versa for rapid and uniform mixing of gas and combustion air for desired flame
stability.
A further aspect of the present invention is directed to a high capacity burner for
lean gas comprising
a gas distributor comprising a gas inlet cooperatively connected to said plurality of
gas distributing passages adapted to split the lean gas stream into multiple identical
and gas distributing passages formed in multiple row(s) and column(s) through
which gas travels horizontally along the burner axis;
said air distributor enclosing the gas distributor having an air inlet and cooperating
with plurality of air passages such as to distribute combustion air stream through
plurality of said passages such that each gas stream coming out from gas
distribution passages at the burner front is surrounded by air streams from all the
four sides facilitating diffusion of gas into air and vice-versa for rapid and uniform
mixing of gas and combustion air for desired flame stability;
said gas distributor connected to said air distributor by means of detachable
connection.
A still further aspect of the present invention is directed to a high capacity
rectangular section lean gas burner wherein said gas distributor is made of
rectangular plates and the top portion of gas distributor is inclined and adapted to
give direction and proper distribution of BF gas through all the gas passages also
formed of rectangular plates welded to the back plate.
A still further aspect of the present invention is directed to a high capacity
rectangular section lean gas burner wherein plurality of said rectangular and axial
gas passages of selective dimensions are arranged in rows and columns in said gas
distributor, which are made by welding plates and all such gas passages are welded
perpendicularly on the back plate cum flange of the gas distributor, with front and
backend of gas slots kept open.
According to yet another aspect of the present invention directed to said high
capacity rectangular section lean gas burner wherein equal horizontal and vertical
gaps are maintained between any two adjacent gas slots, where said gaps for gas
slots decided based on the calorific value of the lean gas and spacers are provided to
maintain the slots in position.
In said high capacity rectangular section lean gas burner, BF gas enters through said
gas inlet which is a circular pipe connected to the bottom of the gas distributor
welded to a blast furnace gas pipe.
and wherein air enters into said air distributor through said air inlet which is a
circular air pipe connected to the bottom of the air distributor connected to an air
supply source.
A still further aspect of the present invention is directed to said high capacity
rectangular section lean gas burner wherein back end of the air distributor is welded
to a rectangular air flange matching with the back plate cum flange of the gas
distributor, where said flanges are tightened together with nuts and bolts and
gaskets.
A still further aspect of the present invention is directed to a high capacity
rectangular section lean gas burner wherein the combustion air pressure requirement
is low in the range of 50-70mmWC and the lean gas pressure requirement is in the
range of 400mm to 500 mmWC for rapid mixing of gas and combustion air to
generate desired stable flame with lean gas.
According to yet another advantageous aspect of the present invention, said high
capacity rectangular section lean gas burner is adapted to generate stable and firmly
anchored flame with lean gas such as low calorific value blast furnace gas at high
volumetric flow rate of 8,000Nm3/hr with 12 nos. of gas slots or 16,000Nm3/hr with
24 nos. of gas slots.
The objects and advantages of the invention and manner of attaining the same are
described hereunder in greater details in relation to following non-limiting illustrative
accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1: is the schematic illustration of an embodiment of the lean gas burner
according to the present invention, showing the arrangement of the rectangular gas
slots and the rectangular air passages inside the burner along with a front view of
the burner in the direction marked 'A'.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWING
The present invention relates to a high capacity rectangular section lean gas burner
with multiple rectangular gas slots/air passages which would ensure fast and uniform
mixing of lean gas and combustion air for desired flame configuration and favour
utilization of thermal energy of lean gas such as blast furnace gas by burning it at
high volumetric flow rates.
Reference is first invited to the accompanying Figure 1 which illustrate the
rectangular section lean gas burner of high volumetric capacity providing for multiple
gas streams split through a plurality of rectangular gas slots within the gas
distributor located in the burner body and each such gas stream is surrounded by
combustion air streams favouring fast and thorough mixing of lean gas and
combustion air.
It is clearly apparent from the accompanying Figure 1 that a plurality of rectangular
shaped gas slots (1) of suitable dimensions has been worked out within the burner
body surrounded by combustion air streams to facilitate rapid mixing of gas and air
streams at the burner nozzle to generate stable flame with lean gas. The burner
design according to the invention does not require any refractory checker work in
front of burner or gas-air premix chamber in the burner body. The rectangular
shaped gas slots surrounded by air passages are provided inside the invented burner
body which has a rectangular section unlike the conventional cylindrical configuration
existing in the similar applications.

According to an embodiment of the lean gas burner of the present invention suitable
for burning Blast Furnace gas with high volumetric capacity comprises of a gas
distributor ( 2 ) which is a rectangular box having inclined top, adapted to split the
lean gas stream into multiple, preferably 12 number rectangular and identical lean
gas streams. These 12 number gas slots are arranged in 4 columns and 3 rows as
shown accompanying Figure 1. The back end of all the gas slots are welded
perpendicularly to a rectangular back plate cum flange (3) of the gas distributor. BF
gas enters through the circular pipe (4) connected to the bottom of the gas
distributor (2). The top portion of the gas distributor is kept inclined (5) to give
direction to the up-coming BF gas towards the gas slots and ensure proper
distribution of gas through all the 12 gas slots welded to the back plate(3). Both the
front and back ends of the rectangular gas slots are open. Equal horizontal and
vertical gaps are maintained between any two adjacent gas slots. The gaps for gas
slots are decided based on the calorific value of the lean gas. The front and back
ends of the gas slots are kept open. The bottom end of the gas distributor ( 2 ) is
welded to a blast furnace gas pipe ( 4 ). The gas slots are held in position by
providing spacers of suitable size in between the slots and fixed inside the air
distributor housing.
It is also apparent from the illustration of the lean gas burner according to the
present invention comprises an air distributor ( 6 ) which is also rectangular in shape
adapted to distribute air stream uniformly over the gas streams. All the gas slots
through which gas travels horizontally and along the burner axis are enclosed in this
air distributor (6). This arrangement ensures each gas stream coming out from gas
slots at the burner front is surrounded by air stream from all the four sides favoring
rapid and thorough mixing of adjacent streams of lean gas and combustion air for
desired flame configuration and stability. Air enters into the air distributor through
the circular air pipe (7) connected to the bottom of the air distributor (6). V-shaped
plates are provided at the front side of the air distributor located in between two
columns of rectangular gas slots to give proper direction to air streams. The back
end of the air distributor is welded to a rectangular air flange (8) matching with the
back plate cum flange (3) of the gas distributor. The flanges (3 & 8) are tightened
together with nuts and bolts and gaskets.
The gas distributor ( 2 ) assembly is fixed with the air distributor ( 6 ) by connecting
rectangular back plate cum flange (3) of gas distributor and rectangular flange (8) of
air distributor ( 6 ). The air enters the air distributor through an air pipe ( 7 )
connected at the bottom and get distributed into the surrounding gas slots and travel
towards the burner front along the burner axis.
In the above described configuration of lean gas burner, total blast furnace gas
stream is thus distributed into multiple rectangular and identical gas slots arranged
in one or more row(s) and column(s) in a gas distributor. Air distributor distributes
air surrounding each of out-coming gas stream.
This arrangement of gas coming at desired velocity through multiple gas slots
surrounded by air streams has ensured fast diffusion of gas into combustion air and
vise versa and thereby helped in achieving fast and uniform mixing between gas and
combustion air streams and in achieving desired flame stability. The present design
does not require any refractory checker work or premix of gas and air inside burner
body. The above invention has thus simplified the burner design. Non-requirement of
any refractory checker work has eliminated any maintenance of refractory checker
work and improved burner availability for burning surplus BF gas to generate steam
or power.
It is thus possible by way of the present invention to provide a lean gas burner of
rectangular section comprising a plurality of rectangular gas slots, such that each of
the lean gas stream issuing through the individual gas slots, is completely
surrounded by combustion air stream at the burner nozzle, ensuring desired rapid
and uniform mixing of gas and air for desired stable flame. Importantly, the lean gas
burner of this configuration does not require any refractory checker work or pre-
mixing of gas and air in the burner, favouring longer operating life free of
maintenance. This burner configuration enable rapid and uniform mixing of gas and
combustion air at very low combustion air pressure in the range of 50-70mmWC
near the burner to generate desired stable flame with lean gas. The BF gas pressure
requirement near the burner is 400mm to 500mmWC. Advantageously, the lean gas
burner of this configuration having rectangular section enable generating stable and
firmly anchored flame with lean gas such as the blast furnace gas having low
calorific value, at high volumetric flow rate of the order of 8,000Nm3/nr with 12 nos.
of gas slots or 16,000Nm3/hr with 24 nos. of gas slots in a burner. The lean gas
burner of rectangular configuration would thus be suitable for burning lean gas/BF
gas as fuel for a number of auxiliary services/applications in steel plants.
We Claim:
1. A high capacity burner for lean gas comprising
a gas distributor comprising a gas inlet operatively connected to plurality of gas
distributing passages formed therein adapted to split the lean gas into plurality of
lean gas streams emanating through said gas distributing passages such that the
lean gas travels horizontally along the burner axis;
an air distributor enclosing the said gas distributor having an air inlet and adapted
to distribute combustion air stream through plurality of passages such that each gas
stream coming out from gas distributing passages at the burner front is surrounded
by air streams from all the four sides facilitating diffusion of gas into air and vice-
versa for rapid and uniform mixing of gas and combustion air for desired flame
stability.
2. A high capacity burner for lean gas as claimed in claim 1 comprising
a gas distributor comprising a gas inlet cooperatively connected to said plurality of
gas distributing passages adapted to split the lean gas stream into multiple identical
and gas distributing passages formed in multiple row(s) and column(s) through
which gas travels horizontally along the burner axis;
said air distributor enclosing the gas distributor having an air inlet and cooperating
with plurality of air passages such as to distribute combustion air stream through
plurality of said passages such that each gas stream coming out from gas
distribution passages at the burner front is surrounded by air streams from all the
four sides facilitating diffusion of gas into air and vice-versa for rapid and uniform
mixing of gas and combustion air for desired flame stability;
said gas distributor connected to said air distributor by means of detachable
connection.
3. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 or 2 wherein said gas distributor is made of rectangular plates and the top portion
of gas distributor is inclined and adapted to give direction and proper distribution of

BF gas through all the gas passages also formed of rectrangular plates welded to
the back plate.
4. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 to 3 wherein plurality of said rectangular and axial gas passages of selective
dimensions are arranged in rows and columns in said gas distributor, which are
made by welding plates and all such gas passages are welded perpendicularly on the
back plate cum flange of the gas distributor, with front and backend of gas slots kept
open.
5. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 to 4 wherein equal horizontal and vertical gaps are maintained between any two
adjacent gas slots, where said gaps for gas slots decided based on the calorific value
of the lean gas and spacers are provided to maintain the slots in position.
6. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 to 5 wherein BF gas enters through said gas inlet which is a circular pipe connected
to the bottom of the gas distributor welded to a blast furnace gas pipe.
7. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 to6 wherein air enters into said air distributor through said air inlet which is a
circular air pipe connected to the bottom of the air distributor connected to an air
supply source.
8. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 to 7 wherein back end of the air distributor is welded to a rectangular air flange
matching with the back plate cum flange of the gas distributor, where said flanges
are tightened together with nuts and bolts and gaskets.
9. A high capacity rectangular section lean gas burner as claimed in anyone of claims
1 to 8 wherein the combustion air pressure requirement is low in the range of 50-
70mmWC and the lean gas pressure requirement is in the range of 400mm to 500
mmWC for rapid and uniform mixing of gas and combustion air to generate desired
stable flame with lean gas.
10. A high capacity rectangular section lean gas burner as claimed in anyone of
claims 1 to 9 which is adapted to generate stable and firmly anchored flame with
lean gas such as low calorific value blast furnace gas at high volumetric flow rate of
8,000IMm3/hr with 12 nos. of gas slots or 16,000Nm3/hr with 24 nos. of gas slots.
11. A high capacity rectangular section lean gas burner substantially as
hereindescribed with reference to the accompanying figure.

The present invention relates to a lean gas burner of high volumetric capacity
adapted to efficiently utilize Lean gas like blast furnace gas (calorific value ~ 780
Kcal/Nm3). Importantly, the lean gas burner comprises rectangular shaped gas
slot(s) of suitable dimensions worked out in a gas distributor arranged in selective
number of columns and rows, adapted to split the lean gas stream into a plurality of
lean gas streams that travels horizontally parallel to the burner axis, and an air
distributor which is also rectangular in shape and enclosing the gas distributor
adapted to distribute air stream uniformly surrounding the gas streams to facilitate
rapid and uniform mixing of gas and air streams at the burner exit to generate stable
flame at the burner front where each gas stream is surrounded by air streams from
all the four sides. Advantageously, the lean gas burner is suitable for low combustion
air pressure (50-70mmWC) to generate desired stable flame with lean gas.