FIELD OF INVENTION
The present invention relates to an improved spies valve for draining of ash in
circulating fluidized bed combustion (CFBC) boilers. More particularly the
invention relates to an ash draining spies valve arrangement which eliminates
the issue of non-draining bed material from the combustor.
BACKGROUND OF THE INVENTION
Circulating fluidized bed combustion (CFBC) is an efficient and known method of
burning various grades of fuels in particular, coal, lignite, anthracite coal etc.
The CFB process utilizes a Fluidized Bed Combustor in which crushed coal and
limestone are suspended in a stream of upward flowing air. Due to the fine
particle size of the coal feed and high gas velocity, the bulk of the solids is
carried out of the combustor along with the flue gases, collected in a recycling
cyclone and returned to the combustor. This gives the process its name
circulating fluidized bed.

Combustion: The fuel is burnt at a temperature of about 850C. It is fed directly
to the combustor without requiring costly fuel preparation and distribution
systems. The combustion air is fed in two stages - Primary Air through the
combustor and Secondary Air part way up the combustor above the fuel feed
point. The limestone required for desulphurization is added near the bottom of
the combustor.
Spies valves are provided to drain ash from combustor to ash coolers. During
boiler operation, a certain differential pressure of solid material column is
required for heat transfer. In CFBC boiler's combustor and fluidized bed heat
exchanger (FBHE) zone, heat transfer is by conduction of heat from hot material
to water in the tube. To achieve maximum heat transfer certain quantity of
material should be circulated in the combustor to cyclone and then back to the
combustor. The optimum quantity of material required is arrived by measuring
the differential pressure between the grate level solid column and the top portion
of the combustor. The reduction in DP indicates reduction in material circulation
and thus reduction in heat transfer.

Spies valves are located at the following locations for draining ash:
1) In combustor to ash cooler - 2 nos
2) One spies valve in each seal pot to FBHE - totally 4 nos
3) Between super heater FBHE and Ash cooler-1 no.
The number of spies valve varies depending on boiler capacity. For 125 MW
CFBC plant 7 Nos of spies valve are installed.
In the combustor these valves have to handle ash at very high temperature
(around 800 - 850°C). During boiler operation, to reduce the material inventory
in the combustor, the spies valve needs to be opened to drain out the material.
The problem faced is that the material does not get drained when the valve is
opened. On analysis it is identified that the ash material in front of spies valve,
becomes non-fluidising and thus does not flow to the ash cooler.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved spies valve for
draining of ash in circulating fluidized bed combustion boilers, which ensures
trouble free operation of the spies valve maintaining continuous flow of the drain
ash.

Another object of the invention is to propose an improved spies valve for
draining of ash in circulating fluidized bed combustion boiler which is capable of
disturbing the static portion of bed material to make the material flow.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be explained with reference to the accompanying
drawings where
Figure 1 shows a CFBC boiler consisting of combustor (01), cyclone (04),
FBHE (03) and back pass (05).
Figure 2 shows a spies valve assembly consisting of a shaft (06) provided
with cooling water inlet (08) and outlet line (09), a lance pilot (11).
Figure 3 shows the spies valve according to the invention with a rod (12)
welded to the lance pilot (11).

DETAILED DESCRIPTION
As shown in Figure 1 the CFBC boiler consist of combustor (01), cyclone (04),
FBHE (03), back pass (05) and spies valve (06).
In CFBC boiler the material kept over the distributor plate is fluidized due to the
primary air 02 supplied from bottom. The process utilizes a Fluidized
Bed Combustor 01 in which crushed coal and limestone are suspended in a
stream of upward flowing air. Due to the fine particle size of the coal feed and
high gas velocity, the bulk of the solids is carried out of the combustor along
with the flue gases, collected in a recycling cyclone 04 and returned to the
combustor or through FBHE 03. This gives the process its name Circulating
Fluidized Bed. The FBHEs are made to be effective by opening the spies valve, so
that hot material will flow through FBHEs and heat transfer will take place. The
bigger size particles will be collected at cyclone due to vortex effect in vortex
finder.
Very fine fly ash and flue will be passed through back pass 05, due to the
Induced draft fan suction effect. The back pass 05 is provided with heat transfer
coils.

As shown in Figure 2, the spies valve assembly consists of shaft (06), actuator
assembly for the operation of spies valve.
The lance pilot 11 will move to and fro for opening and closing of the hole
provided at the seating block 07. While the shaft moves back a circular opening
will be created between pilot and seating block. Through the opening material 10
will flow. While moving forward, opening will be closed and material flow will be
stopped to ash cooler (13).
Since the material handled by the spies valve is around 850 deg C, the shaft is
provided with cooling water inlet 08 and outlet line 09.
In order to reduce the material inventory in the combustor during boiler
operation, the spies valve needs to be opened to drain out the material to ash
cooler (13). The problem faced is that the material does not get drained when
the valve is opened, due to the solid formation at the front portion of spies valve
lance pilot (11). On analysis it is identified that the ash material in front of spies
valve becomes, solid, agglomerated and non-fluidising and thus does not flow to
the ash cooler (13). The bigger agglomerated solid mass will be hit by the rod
(12) and fragmented into small size particle.

Hence, the improved arrangement of spies valve disturbs the static portion of
bed material and makes the material to flow to the ash cooler (13).
To make free flow of material and to disturb the material, a rod is provided at
the tip of the lance front. The bigger agglomerated solid mass will be hit by the
rod (12) and fragmented into small size particle. And now after opening the
valve, due to the disturbance, the solid material will flow freely to the ash cooler.
A rod 12 provided at the tip of the lance to disturb the material in front and after
opening, due to the disturbance the solid material will flow freely to ash cooler.
The rod 12 is welded to the lance pilot (11). The angle of said rod is mounted
vertical to the lance pilot (11). The length of the rod (12) is 1.5 times of the
diameter of the rod.

WE CLAIM
1. An improved spies valve for draining of ash in circulating fluidized bed
combustion (CFBC) boilers, comprising:
- a shaft (06);
- a lance pilot (11) attached to the shaft (06);
- a cooling water inlet (08);
- outlet lines (09);
- seating block (07);
Characterized in that,
at least a rod (12) is provided at the tip of the lance for disturbing the
material in front and for hitting the bigger agglomerated solid mass
fragmenting them into small size particle.
2. An improved spies valve as claimed in claim 1, wherein the rod (12) is
welded to lance pilot (11).
3. An improved spies valve as claimed in claim 1, wherein the rod (12) is
mounted vertical to the lance pilot (11).

4. An improved spies valve as claimed in claim 1, wherein the length of the
rod (12) is 1.5 times of the diameter of the rod (12).

An improved spies valve for draining of ash in circulating fluidized bed
combustion boiler consists of a shaft (06), a lance pilot (11) attached to the shaft
(06), a cooling water inlet (08), outlet lines (09), seating block (07) when a rod
(12) is provided at the tip of the lance for disturbing the material in front and for
hitting the bigger agglomerated solid mass fragmenting them into small size
particle making them flow freely to the ash cooler (13).