FIELD OF THE INVENTION
The present invention relates to an improved ash discharge valve (ADV) in
Circulating Fluidized Bed Combustion Boilers control and recirculation of flue gas
for heat recovery. The lance tip is made of high temperature, corrosion resistant
material. Lance assembly is water cooled suitably so that it could sustain high
temperature.
BACKGROUND OF THE INVENTION
In Circulating Fluidized Bed Combustion (CFBC) boiler, crushed coal and
limestone are used as fuel, which are suspended in a stream of upward flowing
air. The combustion air is fed in two stages for example, primary Air through the
combustor and Secondary Air through a part above the combustor's fuel feed
point. The limestone required for desulfurization is added near the bottom of the
combustor. The fuel is burnt at a temperature of about 850°C. It is fed directly to
the combustor. This gives the process its name Circulating Fluidised Bed.
Depending on the mode of operation of a CFB power plant (base load or variable
load) as well as the plant size and the type of fuel used, the plant may be
designed either with or without a Fluid Bed Heat Exchanger (FBHE). In FBHE-
equipped plants, the heat transfer surfaces for steam generation are located
both in the combustor and in the FBHE. On leaving the recycling cyclone, a
portion of the hot solids is diverted to the Fluid Bed Heat Exchanger where it is
cooled before being returned to the combustor. Ash Discharge Valve diverts the
flue gas to heat exchanger.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved ash discharge
valve (ADV) in Circulating Fluidized Bed Combustion Boilers control and
recirculation of flue gas for heat recovery.
Another object of the invention is to propose an improved ash discharge valve
(ADV) in Circulating Fluidized Bed Combustion Boilers control and recirculation of
flue gas for heat recovery, which is provided with a combustor housing to allow
exit of the un-burnt fuel towards the heat exchanger.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved ash discharge valve (ADV) in
Circulating Fluidized Bed Combustion Boilers control and recirculation of flue gas
for heat recovery, the improvement is characterized by comprising : a lance
tube (1) having an end cover and supported by a support assembly (2); an
adjusting lever (3) connected to the lance tube (1) at a distal end, and a shaft of
an electrical linear actuator (6) connected to the adjusting lever (3); a tip (04) of
the lance tube (1) at proximal end senses the temperature of the solid fuel in the
combustor which allows the actuator (6) to provide a corresponding backward
stroke to the lance tube (1); a refractory-lined combustor housing (5) with a
sight glass encompassing the ash discharge valve to control the flow of solid
materials to exit and transfer the heat to the heat exchanger of the boiler; and
an inner tube with at least one helix plate disposed inside the lance tube (1) for
cooling the lance tube (1) through passing cooling water which enables longer
retention of the cooling water inside the lance tube (1) for better cooling and
generate a spiral profile for the exiting cooling water.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - Shows an improved ash discharge valve (ADV) in Circulating Fluidized
Bed Combustion Boilers control and recirculation of flue gas for heat recovery,
according to the invention.
DETAIL DESCRIPTION OF THE INVENTION
According to the invention, the ash discharge valve consists of a Lance tube (1),
a Support assembly (2), an adjusting lever assembly (3), a Lance Tip (04) an
electrical linear actuator (6), and a Housing (5). The Support assembly (2)
support the lance tube (1), and the adjusting lever (3) is connected with the
lance tube (1) and the actuator shaft (6). The lance tip (4) senses the high
temperature solid fuel and the actuator (6) provides a stroke backward to the
Lance tube (1); The lance tube (1) being exposed to high temperature for
cooling purpose, an inner tube is provided inside the lance tube (1), Cooling
water is passed through the inner tube and after striking on an end cover of the
lance tube (1); the water stream comes out making a spiral profile because of a
helix plate disposed on the inner tube, which further allow the cooling water to
remain inside the lance tube (1) for greater amount of time. By using a single
plate as the end cover of the lance tube (1) the performance of water cooling is
maintained.
Support is provided to hold the Lance tube (1) and for proper stroke of the lance
tube. The support assembly (2) comprises three support tubes and two support
plates and holds the lance tube (1) in an ADV Combustor (5). Angle plate,
Stiffener plate and Padding plate are constructed over said support tubes for

connecting the adjusting lever (3) with the Actuator (6). Combustor housing (5)
is provided to guide partially burnt fuel to the heat exchanger, which is filled with
refractory, and a Sight glass is attached to the combustor housing chamber (5).
The provision of the sight glass is given so that the stroke of the lance tube (1)
can be seen and required action can be taken in case of any fault. The adjusting
lever (3) is tightly connected with the lance tube (1). The actuator shaft (6) is
connected with the adjusting lever (3) and responsible for lance stroke. When
the boiler attains a defined load then, the solid materials will be redirected to
heat exchanger of the boiler to transfer the heat by operating the ash discharge
valve. This valve is operated by the actuator which inturn makes the lance tube
to move in backward direction. Solid materials and Un-burnt fuel through the
combustor housing (5) is directed towards the heat exchanger. The lance tip is
made of high temperature, corrosion resistant material. Lance assembly is water
cooled suitably so that it could sustain high temperature.

WE CLAIM :
1. An improved ash discharge valve (ADV) in Circulating Fluidized Bed
Combustion Boilers control and recirculation of flue gas for heat recovery,
the improvement is characterized by comprising :
- a lance tube (1) having an end cover and supported by a support
assembly (2);
- an adjusting lever (3) connected to the lance tube (1) at a distal end, and
a shaft of an electrical linear actuator (6) connected to the adjusting lever
(3);
- a tip (04) of the lance tube (1) at proximal end senses the temperature of
the solid fuel in the combustor which allows the actuator (6) to provide a
corresponding backward stroke to the lance tube (1);
- a refractory-lined combustor housing (5) with a sight glass encompassing
the ash discharge valve to control the flow of solid materials/ un-burnt
fuel to exit and transfer the heat to the heat exchanger of the boiler; and
- an inner tube with at least one helix plate disposed inside the lance tube
(1) for cooling the lance tube (1) through passing cooling water which
enables longer retention of the cooling water inside the lance tube (1) for
better cooling and generate a spiral profile for the exiting cooling water.
2. The ash discharge valve as claimed in claim 1, wherein the support
assembly (2) comprises at least three tubes and two plates to hold the
lance tube (01) in the valve.

3. The ash discharge valve as claimed in claim 1, wherein the helix plates are
disposed at equidistant locations in the inner tube.
4. The ash discharge valve as claimed in claim 1, wherein the lance tip (04)
is made of high grade temperature resistant material for sustaining high
temperature.

ABSTRACT

The invention relates to an improved ash discharge valve (ADV) in Circulating
Fluidized Bed Combustion Boilers control and recirculation of flue gas for heat
recovery, the improvement is characterized by comprising : a lance tube (1)
having an end cover and supported by a support assembly (2); an adjusting
lever (3) connected to the lance tube (1) at a distal end, and a shaft of an
electrical linear actuator (6) connected to the adjusting lever (3); a tip (04) of
the lance tube (1) at proximal end senses the temperature of the solid fuel in the
combustor which allows the actuator (6) to provide a corresponding backward
stroke to the lance tube (1); a refractory-lined combustor housing (5) with a
sight glass encompassing the ash discharge valve to guide un-burnt fuel to exit
and transfer to the heat exchanger of the boiler; and an inner tube with at least
one helix plate disposed inside the lance tube (1) for cooling the lance tube (1)
through passing cooling water which enables longer retention of the cooling
water inside the lance tube (1) for better cooling and generate a spiral profile for
the exiting cooling water.