FIELD OF INVENTION
The present invention relates to Bed Lance Burners of Circulating Fluidized Bed
Combustion (CFBC) boilers and more particularly to the purge air system employed in
CFBC boilers to prevent entrapment of bed material into the spray tips of Bed Lance
Burners and to avoid burner tip choking.
BACKGROUND OF THE INVENTION
In Circulating fluidized Bed Combustion boilers, Start-up Burners are mounted on the
water walls above the bed level and Bed Lance Burners are provided in the water wall
beneath the bed material and hence Bed Lance Burners are covered by the bed material.
Start-up Burners are used to heat the bed material in the combustor of CFBC boilers
above the auto-ignition temperature of solid fuel or liquid fuel, at which the fuel fed into
the combustor can burn by virtue of the temperature in the combustor. The liquid fuel is
fed in to the combustor in the form of fine spray with the aid of Bed Lance burners.
Liquid fuel oil is sprayed into the combustor by the Bed Lance Burners. The spray plate
provided in the Bed lance Burner, is provided with minute holes which are connected
suitably to metallic pipes feeding fuel oil and the atomizing medium into Bed Lance
Burner. Bed Lance burners are put in operation as required during the boiler operation.
When the Bed Lance burners are not in service, due to fluidization of bed material and
the combustor pressure, the bed material tends to get into the spray plate through the
minute holes and to choke the minute holes in the spray plate. To avoid this happening,
when bed lance burners are not in service, air at a higher pressure is made to pass
through the fuel feeding pipe and the pipe feeding atomising medium to the spray plate
so as to prevent the entrapment of bed material into the spray plate.
The arrangement as per the existing art for providing purge air to Bed Lance burners in
CFBC boilers (Figure-1) includes a purge air header (30) from which tap-offs (31,36,41)
provide purge air to bed lance burners as required. Opening and closing of Solenoid
valves (33, 38, 43) are through control logics.

When the Bed Lance Burner (27) is in operation, the pneumatic valves (3, 8) are opened
and pneumatic valve (9) is closed. Fuel oil flows through the fuel oil feeding tube (4) and
the atomising steam flows through the atomising steam feeding tube (10) to the Bed
Lance Burner (27). When the Bed Lance Burner (27) is in idle condition, pneumatically
operated valves (3, 8, 9) are closed. Solenoid valve (33) is opened so that purge air
flows through the fuel oil feeding tube (4) as well as the atomising steam feeding tube
(10) to the Bed Lance Burner (27), preventing the flow of bed material into the Spray
plate of the Bed Lance Burner (27).
Above operational methodology is adopted by other Bed Lances (28, 29) also and is
extended to any number of Bed Lance Burners. It is intended to provide the present art
to enhance the availability of Bed Lance Burners in CFBC boilers by preventing the
ingress of fuel oil into the purge air pipe lines.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a simplified purge air system
for Bed Lance Burners in CFBC boilers.
Another object of the present invention is to eliminate the use of dedicated purge air
system for Bed Lance Burners in CFBC boilers.
A further object of the present invention is to provide a purge air system for Bed Lance
Burners of CFBC boilers, that nullifies the disadvantages posed by the prior art.
SUMMARY OF INVENTION
Accordingly, there are provided methods (Fig. 2 & 3) to supply purge air to Bed Lance
Burners of CFBC boilers. The present art is designed to simplify the purge air system for
Bed Lance Burners and also is oriented to eliminate the dedicated purge air system for
Bed Lance Burners. Pneumatic valves are provided suitably and control logics is so
modified for opening and closing of the pneumatically operated valves provided near

. each Bed Lance Burner, to meet the objectives of the present art. For purging the Bed
Lance Burners, the present art enables either the flow of atomising medium or the purge
air through the fuel oil feeding tube and through the tube feeding atomising medium to
the Bed Lance Burner.
BRIEF DESCRIPTION
Figure-1 : Existing art of Purge air system for Bed Lance Burners of CFBC boilers.
Figure-2: Present art of Purge air system for Bed Lance Burners with steam atomization
Figure-3: Present art of Purge air system for Bed Lance Burners with air atomization
DETAILED DESCRIPTION
In the present art of purge air system (Fig. 1 ) for Bed Lances of CFBC boilers, there is
provided a header (1) to feed fuel oil and the header (5) to feed the atomising medium
to the Bed Lance Burners. Branch off pipe (2) from the header (1) provides fuel oil to
Bed Lance Burners (27) while the branch off pipes (6) from the header (5) provides
atomising medium to Bed Lance Burners (27). When the Bed Lance Burner is to be put in
operation, the pneumatically operated valve (3) is opened to allow the fuel oil into Bed
Lance Burners (27) through the pipe(4) and the pneumatically operated valve (9) is
closed to allow the atomising medium to flow into Bed Lance Burners (27) through the
pipe (10). Similar operational sequence is adopted to put in the other Bed Lance Burners
(28, 29) also into operation. Opening and closing of related valves are made through a
control logic of Burner Management System.
There is included in the present art of purge air system for the Bed Lance Burners
employing steam as atomising medium (Figure-2), the header (30) to provide purge air
to the Bed Lance burners (27,28,29). The pneumatically operated valve (45) is provided
in the header (5) to allow/stop the flow of atomising steam into the Bed Lance Burners
(27,28,29). The pneumatically operated control valve (46) is provided in the header (30)
to allow or stop the flow of purge air into the Bed Lance Burners. If the valve (45) in

the header (5) is opened, the valve (30) in the air header (46) is closed. The valve (45)
is kept opened, if any of the Bed Lance Burners is working, to allow the steam to
working Bed Lance Burners for atomization and the steam passing into the idle Bed
Lance Burners is used as the purging medium. When all the Bed Lance Burners are not
working, the valve (45) is closed and the valve (46) is opened, to allow the air to flow
into all the Bed Lance Burners for purging.
In the present art of purge air system for the Bed Lance Burners employing compressed
air as the atomising medium (Figure-3), compressed air flows through the header (5) to
provide air to the Bed Lance burners (27,28,29).
When the Bed Lance Burner (27) is put into operation, the pneumatically operated valve
(3) in the fuel oil line is opened and the interconnecting pneumatic valve (9) is closed.
Fuel oil and the air for atomization flow into the Bed Lance Burner (27). When the Bed
Lance Burner (27) is stopped from working, the pneumatic valve (3) in the fuel oil line is
closed and the interconnecting valve (9) is opened to provide air to the Bed Lance Burner
(27) for purging and preventing the entrapment of bed material into the Bed Lance
Burner (27). Opening and closing of the pneumatically operated valves are done through
control logics. Similar operational sequence is adopted to put in the other Bed Lance
Burners (28, 29) also into operation. Opening and closing of related valves are made
through a control logic of Burner Management System.

WE CLAIM
1. A simplified purge air system for Bed Lance Burners of CFBC boilers comprising:
- a header (1) for feeding fuel oil to the Bed Lance Burners (27, 28, 29) through branch
of pipes (2, 11, 19);
- a header (5) for supplying atomising medium through pipes (6, 14, 22) to the Bed
Lance Burners;
- an air header (30) for providing purge air to the Bed Lance Burners;
- a pneumatically operated valve (45) provided in the header (05) for allowing/ stopping
the flow of atomising steam into the Bed Lance Burners;

- a pneumatically operated control valve (46) provided in the air header (30) for
regulating or stopping the flow of purge air into the bed lance burners;
- pneumatically operated valves (3, 12, 20) provided for allowing or stopping the flow of
fuel oil into the bed lance burners;
-pneumatically operated valves (9, 17, 25) provided for allowing or stopping the flow of
atomizing medium or the plurge air into the bed lance burners;
- if light fuel oil only is used in Bed Lance Burners, pneumatically operated valves (45,
46) and purge air header (30) are not excluded;
wherein a series of manually operated valves and non-return are required for the system
characterized in that a simplified purge air system is established for the Bed Lance
Burners to prevent the flow of bed material into the spray plate of the Bed Lance
Burners.
2. The purge air system as claimed in claim 1 wherein a pneumatically operated
open/close valve (45) is disposed in the header (5) and a pneumatically operated
regulating valve (46) is disposed in the air header (30).
3. The purge air system as claimed in claim 1 wherein the valve (45) is in open condition
when any of the Bed Lance Burner (27, 28, 29) or all of the Bed Lance Burners (27, 28
29) are working.

4. The purge air system as claimed in claim 1 wherein the valve (45) is in closed position
only when all of the Bed Lance Burners (27, 28, 29) are not working.
5. The purge air system as claimed in claim 1 wherein the valve (46) is closed when
valve (45) is opened and valve (46) is opened when valve (45) is closed.
6. The purge air system as claimed in claim 1 wherein the opening and closing of valves
(45, 46) are done through control logics.
7. The purge air system as claimed in claim 1 wherein when the Bed Lance Burner (27)
is put in operation, fuel oil valve (3) is opened and the inter-connecting valve (9) is
closed so that fuel oil goes into the Bed Lance Burner (27) through the pipe (4) and the
atomising steam flows into the Bed Lance Burner (27) through the pipe (10).
8. The purge air system as claimed in claim 1 wherein when the Bed Lance Burner (27)
is to be stopped from its operation, fuel oil valve (3) is closed and the inter-connecting
valve (9) is opened so that the atomising steam goes into the Bed Lance Burner (27)
through the pipe (4) and also through the pipe (10).
9. The purge air system as claimed in claim 1 wherein the flow of steam into Bed lance
Burner (27) through the pipes (4, 10) cleans the spray plate and prevents the entry of
bed material into the spray plate.
10. The purge air system as claimed in claim 1 wherein when all the Bed Lance Burner
(27, 28, 29) are not working, all the fuel oil valves (3, 12, 20) and valve (5) are closed,
valve (46) and all the interconnecting valves (9,17,25) are opened so that purge air flows
into all the Bed Lance Burners (27,28,29) through the fuel oil feeding pipes and steam
feeding pipes to clean the spray plate and prevent the entry of bed material into the
spray plate.

11. The purge air system as claimed in claim 1 wherein the valve (46) is a regulating
valve and helps in modulating the parameters of purge air meeting the operational
requirements.
12. The purge air system as claimed in claim 1 wherein modulation of parameters of
purge air helps in controlling the erosion of spray plates.
13. The purge air system as claimed in claim 1 wherein the present art of purge air
system for Bed Lance Burners of CFBC boilers (Fig. 3) is a simplified system relevant to
Bed lances Burners using compressed air as atomising medium.
14. The purge air system as claimed in claim 1 wherein the present art of purge air
system for Bed Lance Burners of CFBC boiler (Fig. 2) is a simplified system relevant to
Bed Lance Burners using steam air as atomising medium.

ABSTRACT

The invention relates to operation of Bed Lance Burners in CFBC boilers and more
specifically to provide a simplified purge air system to Bed Lance Burners so as to
prevent the Bed material entering into the Bed Lance Burners. According to the present
invention (Fig 2, 3) there is provided a system, to provide purge air to Bed Lance Burners
in CFBC boilers, in such a way that the fuel oil line and the purge air line are no where
connected. The present art provided for Bed Lance firing heavy fuel oil (Fig 2) has the
valves (45, 46) and appropriate connection of header (5) and air header (30). The
present art provided for Bed Lance firing only light fuel oil (Fig 3) does not provide with
the valves (45, 46) and the purge air header (30). Through suitable Control logics for
opening and closing of relevant pneumatically operated valves near each Bed Lance
Burner, continuous purging of Bed lance Burners is done.