FIELD OF THE INVENTION
The Present invention relates to Bed Lances, located beneath the bed material of
combustor of a boiler. More particularly, the present invention relates to an
improved Bed Lance assembly for CFBC boilers.
BACKGROUND OF THE INVENTION
Bed Lances immersed in the dense region of bed material (sand) in CFBC boilers
perform basically two operations viz. a) Atomiszation of fuel oil - breaking the
fuel oil into mist like spray and b) Projection of this atomized oil spray into the
furnace. This spray possessing combustion characteristics enables the
temperature increase inside the combustor.
A thorough mixing of the fuel oil spray with a proportionate supply of air is
performed on the fuel immediately preceding and at the initiation of the
combustion process. These factors influence combustion and boiler efficiency.
The air is provided through a plurality of air nozzles from the combustor bed.
As shown in fig.l, prior art Bed Lance arrangement mainly consists of a Seal Box
(1), a primary air connection (2), an Isolation Ball valve (3), a Bed Lance guide
pipe (4), a Lance (5), and an atomizing nozzle (6).
As the Bed Lances are buried inside the bed material, during fluidization bed
material tend to enter into the guide pipe (4). Primary air is continuously made
to flow into the guide pipe at required pressure and flow through the primary air
connection (2). This primary air also helps to cool the atomizing nozzle (6) of
the Lance (5). While dismantling the Lance (5) for maintenance, the isolation Ball
valve (3) prevents the flow of primary air to atmosphere.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an improved Bed
Lance assembly for CFBC boilers, which eliminates the disadvantages of prior art.
Another object of the present invention is to propose an improved Bed Lance
assembly for CFBC boilers, which enables easy withdrawal/replacement of the
Lances.
A still another object of the present invention is to propose an improved Bed
Lance assembly for CFBC boilers, requires which reduced quantity of cooling air.
A further object of the present invention is to propose an improved Bed Lance
assembly for. CFBC boilers, which is enabled to easily control the purge air flow
through the guide pipe.
A still further object of the present invention is to propose an improved Bed
Lance assembly for CFBC boilers, which enhances availability of the Lances for
operation.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved Bed Lance assembly for CFBC boilers,
comprising one each short and inclined limb for cooling an air connection
connecting a seal box, an isolation Ball valve, a guide pipe with annular air
passages, one lance, and an atomizing nozzle. The guide pipe acts as a chamber
to provide curtain air for the lances including disposition of the lances. The
guide pipe is fabricated with two concentric pipes, and having at a first end
a hot end piece, and an air inlet tube including a flange at a second end. The
pipes forming the guide pipe and the Hot end piece of the guide pipe, essentially
enables to achieve the technical solution of the prior art disadvantages.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure -1: Prior art Bed Lance assembly for CFBC Boilers
Figure - 2: An improved bed lance assembly for CFBC boilers according to the
present invention.
Figure - 3: A guide Pipe assembly of the bed lance assembly according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
As shown in fig.2, the improved bed lance assembly for CFC boilers comprises a
seal box (1), a compressed air connection (2), an isolation Ball valve (3), a
plurality of guide pipe (4) with annular air passages, one lance (5) and an
atomizing nozzle (6).
As shown in fig.3, each guide pipe (4) of the improved Bed Lance assembly
comprises an outer tube (7), an inner tube (8), an end piece (9), a stub (10) for
compressed air, and a connecting flange (11).
As shown in fig.3, the outer tube (7) is provided with a stub (10) for providing
compressed air. The inner tube (8) has one or more grooves made along its axis.
At first end of the outer tube (7) and that of the inner tube (8) are welded to the
connecting flange (11). At a second end of the outer tube (7) and inner tube (8),
an end piece (9) is welded. The end piece (9) is configured to collect air from the
grooves in the annular space of the inner tube (8) and directs the air to form a
curtain inside the inner surface of the inner tube (8). The end piece (9) also
allows an atomizing nozzle (6) to be located inside the guide tube assembly.
When the Lance (5) is in service position, the flow of compressed air from the
end piece (9) gets reduced due to the restriction in the free flow area caused by
the atomizing nozzle (6), resulting in minimum consumption of the compressed
air. When the Lance is withdrawn from its service position for maintenance, the
free flow area for the compressed air gets automatically increased and an
effective curtaining occurs. This effective air curtaining in turn allows smooth
withdrawal of the Lance (5).
ADVANTAGES OF THE INVENTION
The improved Bed lance assembly of the invention reduces cooling air
requirement, allows reduction in operation and maintenance cost. The inventive
Bed Lance assembly eliminates the prior art disadvantages of withdrawal of the
bed lances due to entrapment of bed material into the guide pipe of the bed
lance. The invention allows increased availability of the Lances during operation.
WE CLAIM
1. An improved Bed Lance assembly for CFBC boilers a compressed air
connection (2) connected on a seal box (1); an isolation Ball valve (3),
isolating flow of compressed air to one atomizing nozzle (6); a plurality of
guide pipe (4) with annular air passages internally accommodating the
one atomizing nozzle (6); and one lance (5) detachably attached to the
other end of the isolation ball valve (3), wherein each guide pipe (4) is
fabricated with an outer tube (7) having a stub (10) to provide
compressed air, an inner tube (8) comprising one or more grooves,
wherein a connecting flange (11) adjoining a first end of both the inner
and outer tubes (8, 7), while a hot end piece (9) rigidly connecting a
second end of both the inner and outer tubes (8, 7), and wherein the hot
end piece (9) is configured to collect air from said one or more grooves
and form a curtain inside the inner surface of the inner tube (8).
2. The Bed Lance assembly for CFBC boilers as claimed in claim-1 wherein
the plurality of Guide Pipe (4) is fabricated from SCH40 SA106 Gr. B
pipes.

ABSTRACT

An improved Bed Lance assembly for CFBC boilers a compressed air connection
(2) connected on a seal box (1); an isolation Ball valve (3), isolating flow of
compressed air to one atomizing nozzle (6); a plurality of guide pipe (4) with
annular air passages internally accommodating the one atomizing nozzle (6);
and one lance (5) detachably attached to the other end of the isolation ball valve
(3), wherein each guide pipe (4) is fabricated with an outer tube (7) having a
stub (10) to provide compressed air, an inner tube (8) comprising one or more
grooves, wherein a connecting flange (11) adjoining a first end of both the inner
and outer tubes (8, 7), while a hot end piece (9) rigidly connecting a second end
of both the inner and outer tubes (8, 7), and wherein the hot end piece (9) is
configured to collect air from said one or more grooves and form a curtain inside
the inner surface of the inner tube (8).