FIELD OF THE INVENTION
The present invention relates to developing an improved pilot burner system to light up
main burner for gaseous fuel based combustion systems. More particularly, the invention
relates to an improved configuration of injection type pilot burner system to light up the
main burners for gas based combustion systems such as those for radiant tube furnace,
adapted to sucking in ambient air for combustion of gaseous fuel, without the need for any
additional equipment such as he blower for supplying the combustion air. Advantageously,
an outer concentric pipe is provided over the gas nozzles for sending more than 95% of the
total combustion air through a plurality of holes of preferred sizes selectively disposed along
the circumference of the nozzle as well as the surrounding tube covering the nozzle adapted
to sucking in more ambient air required for total combustion due to higher gas velocity in
the range of 60 m/s at the exit point of burner nozzle generating higher injection effect.
Combustible gas mixes with combustion air at the exit point of the nozzle of the pilot burner
and the fuel gas stream issuing through the gas nozzle is completely surrounded by
combustion air stream at the tip of the burner nozzle. The improved design configuration of
the pilot burner according to the invention is adapted to generate desired stable and fully
anchored flame within the available space for firing. Total gas pipe line of the improved pilot
burner system of the invention is adapted to minimize deposits and choking by the tar,
naphtha or dirt carried by the coke oven gas used as fuel. The new improved pilot burner
based combustion system is thus simple, efficient and cost effective, capable of saving
power and maintenance costs on account of the combustion air blower and thus making
such pilot burners having scope for wide scale application in iron and steel industry for
lighting up of main burners of different gas based combustion systems such as in radiant
tube furnace and slow cooling zone of hot dip galvanizing line of cold rolling mill and the
like.
BACKGROUND ART
It is well known that main burners using liquid or gaseous fuel are extensively used in
combustion systems for various intermediate process steps in Iron and Steel industries. For
smooth and effective operation of the main burners, proper lighting up is essential. Pilot
burner is a very important component of any heating system of Iron and Steel industries. It
is also known in the art that the Coke Oven gas is a High Calorific value gas generated as
by-product in Coke Ovens of Iron and Steel industry, used as fuel for combustion system.
This coke oven gas having high calorific value in the range of ~4200-4250Kcal/Nm3 is being

used as fuel in the pilot burners. There is a requirement in the existing gas based
combustion systems that the fuel gas and the combustion air be mixed as issuing through
the burner nozzle to generate stable flame for igniting the main burners.
The conventional pilot burners used to light up the main burners using coke oven gas as
fuel is pre-mixed type wherein coke oven gas and combustion air are supplied through two
different pipelines and both mix at one point called mixing box. Then the mixture goes to
the gas nozzles of the burners. It is also known that air from blower is used as combustion
air in case of pre-mixed type burner. As the coke oven gas carries a lot of tar, naptha, dirt
etc which get deposited in the pipelines resulting in narrowing down of the inner diameter.
Due to such decrease in the internal diameter of gas supply pipe lines, less quantity of coke
oven gas flows to the burners. Gradually, the pipe line gets fully chocked because of the
smaller inner diameter of the pipe line usually of 1 inch size. To over come this problem, the
diameter has been increased to 1.5 inch and the diameter of the gas nozzle of the existing
burner is 8mm and the fuel gas is flowing through the nozzle at the rate of 11-12
meter/second. Due to such low gas velocity at nozzle exit, it generates less injection effect.
The existing nozzle configuration for the pilot burners having only 4 holes of 5.6 mm
diameter equispaced on the outer pipe of the burner. In the existing pilot burner
configuration, only small amount of atmospheric air for combustion is sucked due to
injection effect of the mixture e.g. coke oven gas and combustion air. In the existing
configuration, total combustion air comprises injection air and air in pre-mixed mixture.
There has thus been a need in the art to developing an efficient pilot burner system for
lighting up main burner in combustion systems using gaseous fuel and in particular coke
oven gas in steel plants wherein the burner system would be adapted for high gas velocity
and higher suction of combustion air so that efficient complete combustion can be achieved
without needing any additional equipment e.g. electrical motor driven blower to meet the
requirement of supply of air for complete combustion. The pilot burner system would be
further improved for higher injection effect adapted to sucking in more ambient air and on
the other hand would be adapted to selectively adopt higher gas impinging velocity. The
improved configuration of the simple, cost effective pilot burner system as of the present
invention thus would be capable of obtaining stable and fully anchored flame particularly to
light up main radiant tube burners with reduced energy consumption.

OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to developing a pilot burner
system for lighting up main burner of gaseous fuel based combustion system which is
simple, cost effective and efficient burner adapted to generate stable and fully anchored
flame within available space for firing, suitable for radiant tube furnace burners and the like.
Another object of the present invention is directed to developing a pilot burner system for
lighting up main burner of gaseous fuel based combustion system wherein combustion air
required for complete combustion of coke oven gas as fuel would be sucked in from
atmosphere at higher rate by injection effect in the nozzle configuration.
A further object of the present invention is directed to developing a pilot burner system for
lighting up main burner of gaseous fuel based combustion system wherein no additional
equipment for supplying the combustion air such as an electric motor driven blower will not
be required at all.
A still further object of the present invention is directed to developing a pilot burner system
for lighting up main burner of gaseous fuel based combustion system wherein higher
injection effect is generated due to higher velocity of the coke oven gas fuel flown through
the nozzle exit.
A still further object of the present invention is directed to developing a pilot burner system
for lighting up main burner of gaseous fuel based combustion system wherein the
combustible gas mixes with combustion air at the exit point of the nozzle of pilot burner for
efficient combustion.
A still further object of the present invention is directed to developing a pilot burner system
for lighting up main burner of gaseous fuel based combustion system wherein the system
saves electrical energy and cost of maintenance of combustion air blower, as used in
conventional system.
A still further object of the present invention is directed to developing a pilot burner system
for lighting up main burner of gaseous fuel based combustion system wherein gas pipe line

has been modified, higher gas flow rate used and selective size of pipe used to eliminate the
problem of section reduction by deposit on inner wall and resultant choking.
A still further object of the present invention is directed to developing a pilot burner system
for lighting up main burner of gaseous fuel based combustion system wherein plug valve of
appropriate size is installed in each gas pipe line of the pilot burner to ensure better control
of fuel gas flow to the burner required to achieve stable and anchored flame.
A still further object of the present invention is directed to developing a pilot burner system
for lighting up main burner of gaseous fuel based combustion system wherein whenever the
main burner goes off, the pilot burner immediately ignites and complete combustion of gas
flowing to the burners takes place, not allowing unburnt fuel gas to escape through
chimney.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a pilot burner system to light
up main burner for gaseous fuel based combustion systems comprising,
a gas nozzle with gas/air passages therein;
an outer concentric air pipe surrounding the nozzle for allowing ambient air for
combustion to enter;
a plurality of holes disposed circumferentially on the nozzle and the concentric air pipe
and adapted such as to allow atmospheric air to be sucked in by injection effect through
said holes for complete combustion of gaseous fuel.
Another aspect of the present invention is directed to a pilot burner system to light up main
burner wherein said plurality of holes disposed circumferentially on the nozzle and the
concentric air pipe are circumferentially equispaced and are of desired selective diameters
depending upon the burner specifications and requirement.

A further aspect of the present invention is directed to a pilot burner system to light up
main burner wherein said gas nozzle of 3.5 mm diameter is made of thermally resistant
grade AISI-310 grade.
A still further aspect of the present invention is directed to a pilot burner system to light up
main burner wherein, said gas nozzle is adapted such that the gas velocity is maintained at
the rate of 60 meters/second at the exit point of the burner nozzle.
Advantageously, in said pilot burner system to light up main burner wherein, higher gas
velocity generates higher injection effect of fuel gas resulting in suction of more ambient air
for total combustion of said fuel gas, preferably mixed gas/coke oven gas.
A still further aspect of the present invention is directed to a pilot burner system to light up
main burner wherein, there are 8 holes of 7mm diameter are made equispaced on
circumference of air pipe in two levels for sucking combustion air.
In said pilot burner system to light up main burner wherein, holes in both levels are
maintained at the distance of 15mm.
A still further aspect of the present invention is directed to a pilot burner system to light up
main burner wherein, said pilot burner is adapted such that the combustible gas mixes with
combustion air at the exit point of the nozzle of the burner.
A still further aspect of the present invention is directed to a pilot burner system to light up
main burner comprising:
said outer concentric air pipe provided over the gas nozzle for supplying more than 95%
of the total combustion air through said holes;
stainless steel impregnated corrugated flexible hosepipe connecting the gas pipe line to
the pilot burners, due to high temperature around the vicinity of the furnace; and
plug valves are installed in each gas pipeline for better control of gas flow to the burner
for achieving stable and anchored flame.

The present invention and its objects and advantages are described in greater details with
reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the sectional view of the conventional pilot burner
using combustion air as pre-mix and ambient air sucked in requiring supply of additional air
from blower.
Figure 2: is the schematic illustration of the sectional view of the pilot burner according to
the present invention showing the provision of additional holes for ambient air suction in the
surrounding tube portion, requiring no blower.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to improved configuration of injection type pilot burner system
to light up the main burners for combustion systems such as those for radiant tube furnace
using gaseous fuels and slow cooling zone of hot dip galvanizing line of cold rolling mill and
the like, adapted to sucking in ambient air for combustion of gaseous fuel, without the need
for any additional equipment such as the blower for supplying the combustion air.
Advantageously, an outer concentric pipe is provided over the gas nozzles for sending more
than 95% of the total combustion air through a plurality of holes of preferred sizes
selectively disposed along the circumference of the nozzle as well as the surrounding tube
covering the nozzle adapted to sucking in more ambient air required for total combustion of
coke oven gas by higher injection effect caused due to higher velocity of gas at the exit of
the nozzle.
Reference is first invited to the accompanying Figure 1 that schematically illustrates the
conventional pre-mixed type pilot burner previously in use adapted to burn coke oven gas
as fuel. In the existing design, coke oven gas and combustion air is supplied through two
different pipe lines and both mix at a point called mixing box. The pre-mixed gas then goes
to the gas nozzles of the burners. In the existing set up for pilot burners, blower air is used
as combustion air in pre-mixed type burners. More over, as the coke oven gas carries a lot

of tar, naptha, dirt etc that get deposited in the pipelines resulting in narrowing down of the
inner diameter. Due to such decrease in the internal diameter of gas supply pipelines, less
quantity of coke oven gas flows to the burners. The problem is aggravated due to small
diameter of pipes and lower gas flow velocity. Gradually, the pipeline gets fully chocked
because of the smaller inner diameter of the pipe line usually of 1 inch size.
To over come this problem, the diameter of supply pipes to conventional pilot burners have
been increased to 1.5 inch and the diameter of the gas nozzle of the existing burner is 8mm
and the fuel gas is flowing through the nozzle at the rate of 11-12 meter/second. Due to
such low gas velocity at nozzle exit, it generates less injection effect. It is clearly apparent
from the accompanying Figure 1, that the existing nozzle configuration for the pilot burners
having only 4 holes of 5.6 mm diameter, equispaced on the periphery of outer pipe of the
burner. In the existing pilot burner configuration, only small amount of atmospheric air for
combustion is sucked due to injection effect of the mixture e.g. pre-mixed coke oven gas
and combustion air as velocity is low. In the existing configuration, total combustion air
comprises injection air and air in pre-mixed mixture.
The improved pilot burner configuration has been developed by way of the present invention
providing for efficient burning of fuel coke oven gas for lighting up main burners, without
needing blower or any additional equipment but is adapted to supply adequate ambient air
from atmosphere required for complete combustion by sucking in atmospheric air due to
injection effect.
Reference is now invited to the accompanying Figure 2, that schematically illustrates the
sectional view of the pilot burner according to the present invention showing the disposition
of required holes for ambient air suction in the nozzle and the surrounding tube portion. In
the new configuration of the pilot burner according to the invention, 3.5mm diameter gas
nozzle is used. Gas velocity is maintained at the rate of 60 to 65 meters/second at the exit
point of the burner nozzle. Higher gas velocity generates higher injection effect resulting in
suction of more ambient air for combustion. There are 8 holes of 7 mm diameter for sucking
combustion air. All 8 holes are made equispaced on circumference of air pipe in two levels.
Both levels having holes maintained at a distance of 15 mm. In this configuration, the
burner do not require any additional equipment for supply of air for combustion of gaseous
fuel. Importantly, the combustible gas mixes with combustion air at the exit point of the
nozzle of the pilot burner. Ambient air for total combustion is sucked from the atmosphere

due to enhanced injection effect of the fuel gas emerging at high velocity from nozzle tip. It
is clearly evident from the accompanying Figure 2, that an outer concentric air pipe is
provided over the gas nozzles for sending more than 95% of the total combustion air
through holes. In the modified and improved pilot burner configuration as of the invention,
the gas stream issuing through the gas nozzle is completely surrounded by combustion air
stream at the tip of burner nozzle. The present nozzle/burner configuration is adapted to
generate stable and fully anchored flame within the available space of the firing/combustion
chamber.
The modified and improved pilot burners have been successfully installed at the radiant tube
furnace for lighting up the main radiant tube burners. These burners use mixed gas as fuel.
Provision has been made in the shell plate of the radiant tube furnace for installation of the
pilot burners. The nozzle of the newly developed pilot burner is made of AISI-310 grade
that is thermal resistant. Stainless steel impregnated corrugated flexible hosepipe of 1-inch
diameter of 500mm length has been used to connect the gas pipe line to the pilot burners.
Stainless steel impregnated corrugated flexible hosepipe has been chosen due to high
temperature around the vicinity of the furnace. Plug valves, preferably 1 inch size, have
been installed in each gas pipeline of the pilot burner for better control of gas flow to the
burner required for achieving stable and anchored flame. Total gas pipelines for new pilot
burners have been modified to minimize the deposits in the gas supply line.
If the main gas burner goes off due to any reason such as power failure, mechanical fault,
and if pilot burner is also not working then the fuel gas flows through idle burner and
unburnt gas leaves through the chimney and thus wasting the heat value of gas not utilized.
Required amount of gas flows to the furnace as per recorder but do not contribute to
heating the furnace, as the gas is not burnt. However, when the pilot burner is in operation
facilitate burning of the fuel gas and recovering the heat of combustion so as to
increase/maintain furnace temperature as necessary.
The modified and improved pilot burner of the present invention is thus simple in
construction, efficient in operation and economizing power consumption by eliminating the
need for any air blower or like equipment. It can generate stable and properly anchored
flame within the available limited space of the combustion chamber. Moreover, the
maintenance of the pilot burner of the invention is easy, faster and less expensive . This
helps in increasing the zonal temperature of radiant tube furnace as because all radiant tube

main burners works on the basis of on-off operation. Thus improved design and
performance of the pilot burners is of extreme importance for on-off operation of the
furnace. Whenever the main burner goes off, it ignites immediately to carry out complete
combustion of gas flowing to the burners, thus saving wastage of unutilized fuel gas. The
modified and improved pilot burner for lighting up main burners according to the invention
is thus capable of wide industrial application and in particular in radiant tube furnaces and
slow cool zone of hot dip galvanizing line of the cold rolling mill in steel plants.

We Claim:
1. A pilot burner system to light up main burner for gaseous fuel based combustion
systems comprising,
a gas nozzle with gas/air passages therein;
an outer concentric air pipe surrounding the nozzle for allowing ambient air for
combustion to enter;
a plurality of holes disposed circumferentially on the nozzle and the concentric air
pipe and adapted such as to allow atmospheric air to be sucked in by injection effect
through said holes for complete combustion of gaseous fuel.
2. A pilot burner system to light up main burner as claimed in claim 1 wherein said
plurality of holes disposed circumferentially on the concentric air pipe are
circumferentially equispaced and are of desired selective diameters depending upon
the burner specifications and requirement.
3. A pilot burner system to light up main burner as claimed in anyone of claims 1 or 2
wherein said gas nozzle of 3.5 mm diameter is made of thermally resistant grade
AISI-310 grade.
4. A pilot burner system to light up main burner as claimed in anyone of claims 1 to 3
wherein, said gas nozzle is adapted such that the gas velocity is maintained at the
rate of 60 meters/second at the exit point of the burner nozzle.
5. A pilot burner system to light up main burner as claimed in anyone of claims 1 to 4
wherein, higher gas velocity generates higher injection effect of fuel gas resulting in
suction of more ambient air for total combustion of said fuel gas, preferably mixed
gas/coke oven gas.
6. A pilot burner system to light up main burner as claimed in anyone of claims 1 to 5
wherein, there are 8 holes of 7mm diameter are made equispaced on circumference
of air pipe in two levels for sucking combustion air.

7. A pilot burner system to light up main burner as claimed in anyone of claims 1 to 6
wherein, holes in both levels are maintained at the distance of 15mm.
8. A pilot burner system to light up main burner as claimed in anyone of claims 1 to 7
wherein, said pilot burner is adapted such that the combustible gas mixes with
combustion air at the exit point of the nozzle of the burner.
9. A pilot burner system to light up main burner as claimed in anyone of claims 1 to 8
comprising:
said outer concentric air pipe provided over the gas nozzle for supplying more than
95% of the total combustion air through said holes;
stainless steel impregnated corrugated flexible hosepipe connecting the gas pipe line
to the pilot burners, due to high temperature around the vicinity of the furnace; and
plug valves are installed in each gas pipeline for better control of gas flow to the
burner for achieving stable and anchored flame.
10. A pilot burner system to light up main burner for gaseous fuel based combustion
systems substantially as hereindescribed with reference to the accompanying non
limiting drawings.

The invention relates to an improved configuration of injection type pilot burner system to
light up the main burners for gas based combustion systems adapted to sucking in ambient
air for combustion of gaseous fuel without the need for blower for supplying the combustion
air. Advantageously, an outer concentric pipe is provided over the gas nozzles in said pilot
burner for sending more than 95% of the total combustion air through a plurality of holes
disposed along the circumference of the surrounding tube covering the nozzle. Higher gas
velocity in the range of 60-65 m/s at the exit point of burner nozzle generates sufficient
suction effect. The pilot burner according to the invention is adapted to generate desired
stable and fully anchored flame within the available space for firing. The new improved pilot
burner is thus simple, efficient and cost effective, capable of saving power and maintenance
costs eliminating blower, and thus having scope for wide scale industrial application in gas
based combustion systems.