Canadian Patents Database / Patent 2344033 Summary

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(12) Patent Application: (11) CA 2344033
(54) English Title: A NOVEL GAS-SOLID SEPARATOR FOR FLUIDIZED BED BOILER
(54) French Title: NOUVEAU SEPARATEUR DE SOLIDE ET DE GAZ POUR LES CHAUDIERES A LIT FLUIDISE
(51) International Patent Classification (IPC):
  • B01D 45/16 (2006.01)
  • F22B 31/00 (2006.01)
  • F23C 10/00 (2006.01)
  • F23C 10/10 (2006.01)
  • F23C 10/18 (2006.01)
  • F23J 15/02 (2006.01)
  • F23L 5/02 (2006.01)
  • F23L 9/02 (2006.01)
(72) Inventors :
  • BASU, PRABIR (Canada)
(73) Owners :
  • BASU, PRABIR (Canada)
(71) Applicants :
  • BASU, PRABIR (Canada)
(74) Agent:
(74) Associate agent:
(45) Issued:
(22) Filed Date: 2001-04-18
(41) Open to Public Inspection: 2001-10-19
Examination requested: 2003-10-22
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
2,306,203 Canada 2000-04-19

English Abstract





An apparatus for separation of solids from a mixture of solid and fluid, which
is supplied
tangentially into a box shaped separation chamber, and leaves horizontally
though
opening (s) on side walls of the chamber. The invention also provides novel
methods for
converting a flame fired boiler into a circulating fluidized bed boiler and
for building new
compact circulating fluidized bed boiler.


Note: Claims are shown in the official language in which they were submitted.



Claim



The embodiments of the invention in which an exclusive property or privilege
is claimed
are defined as follows

I claim

1. A process for removing particles from a gas stream, comprising the step of
providing a gas stream containing gas and particles;
separating said gas stream into a first and second portion;
increasing the concentration of the first portion;
removing the first portion from the separator through a different point than
that
from the second portion
2. A method of adapting a fossil fuel fired boiler into a circulating
fluidized bed
boiler comprising the steps of
a) installing a grid plate at a lower section of a furnace;
b) installing fans under the grid plate to blow air up through the gird plate
when in
operation;
c) installing a solids return system to the furnace
d) providing fuel feeding devices
e) providing secondary air openings;
f) providing an ignition system;
g) providing the method of claim 1 wherein solids separated are sent to the
solids
return system
3. The method of claim 2 wherein the hopper communicates with the lower solid
recycle system through a vertical channel
4. The method of claim 2 wherein the solids gas solid separators are placed at
the
exit of the furnace through which gas-solid suspension leaves the furnace.
5. The method of claim 4 comprising at least one separator formed as
rectangular
chamber with and open end facing upstream with respect to the gas flow, and
closed at downstream
a. gas-solid mixture is directed towards a the device and is made to travel at
a high velocity
b. The mixture enters the device through a rectangular opening
c. The mixture travels in a near circular path
d. The solids are separated during this travel



12



e. The gas continues in the circular path into a spiral which leaves the
chamber through a circular aperture located on the side wall of the
chamber of the device
f. Relatively clean gas leaves the chamber while the solids, separated from
the gas, drops into the chamber from where it is collected in a preferred
way.
6. Heat exchangers which also serve as gas-solid separator
7. Heat exchangers which generates superheated steam by absorbing heat from
hot gas or hot gas-solid suspension
8. Heat exchangers which preheats water
9. Heat exchangers which generate steam by absorbing heat from hot gas or hot
gas-solid suspension
10. A novel gas-solid separator with a geometry which can easily be adapted to
the
rectangular heating surface arrangements of existing boilers
11. A gas-solid separator comprising more than one separation chamber and
collection chamber
12. A gas-solid separator with one circular exit on one of the vertical side
wall
13. A gas solid separator with two circular exits on two vertical side walls
of the
separation chamber
14. A gas-solid separator with one circular exit located off axis on one
vertical side
wall
15. A gas-solid separator with two circular exit located off axis on two side
walls of
the separator
16. A gas-solid separator with recess wall in the rear wall of the separator
chamber
17. A gas-solid separator as in claim 6- 15 with shelves in the rear wall
18. Gas -solid separator of claim 6-17 wherein the side walls are made of heat
absorbing surfaces.
19. Gas solid separator of claim 6-18 wherein the roof, side, rear wall and
front walls
are made of heat absorbing surfaces
20. Gas solid separator of claim 19 wherein heat absorbing front, rear and
roof walls
are covered with thin refractory.
21. Gas-solid separator of claim 19 wherein the side walls are lined with
refractory
22. Gas solid separator a hollow cylinder is inserted in the circular opening
of the
side walls



13




23. A gas-solid separator of claim 22 wherein the exit cylinder is flush with
the inner
face of the side wall
24. A gas-solid separator of claim 22 wherein the exit cylinder is flush with
the outer
face of the side walls
25. Gas-solid separators of claim 10-24 wherein the both front and rear wall
tapers
inward to form a discharge hopper.
26. Gas-solid separator claim 10-24 wherein the front wall is vertical but the
rear wall
tapered inward to form a hopper for the exit of the collected solids
27. A circulating fluidized bed boiler with gas-solid separator of claim 10-28
wherein
a loop seal is connected to the discharge left of the separator
28. A circulating fluidized bed boiler wherein two discharge end of the loop
seal are
on two sides of the rectangular dip leg which is also the discharge ed of the
separator
29. A CFB boiler with gas-solid separator described in 10-26 wherein solids
collected
in the rectangular dip leg enters one loop seal which is located towards the
front
wall of the separator
30. A CFB boiler with gas-solid separator described in claims 10-29 wherein
the
openings on front wall are made be bending vertical tubes sideways
31. A CFB boiler with gas-solid separator described in claims 10-29 wherein
openings on the front walls are made by terminating tubes in horizontal
headers.
32. A separator described in claim 5 where the gas solids enter with a
velocity in the
range of 20-30 m/s range
14

Note: Descriptions are shown in the official language in which they were submitted.


CA 02344033 2001-04-18
A NOVEL GAS-SOLID SEPARATOR FOR FLUDIZED BED BOILERS
This invention relates to process equipment and boilers particularly, a device
for
separating solids from a fluid-solid suspension. This invention also relates
to a novel
method for converting an existing fossil fuel fired (FFF) boiler into
circulating fluidized
bed {CFB) boiler.
Backgiround to the invention
Gas-solid or liquid-solid separators are essential parts of many equipment
including fluidized bed boilers. Circulating fluidized bed boilers and
reactors in particular
use gas solid separator to separate the solids from the gas-solid suspension
and return
the separated solids back to the reactor or boiler-furnace. Another important
application
of gas-solid separation in revamping of old fossil fuel fired (FFF) boilers is
described in
Canadian patent application no 2,159,949.
There are known methods of separating solids from the gas-solid suspension
leaving a furnace. Khanna, in U.S patent No. 5,535,687 teaches the use of
vertical
upright un-cooled (hot) cylindrical cyclone to separate gas from the gas-solid
mixture.
Such cyclones are bulky, requires a large amount of refractory and have high
surface
heat loss. Garcia-Mallol in Canadian patent 2,080,319 teaches the use of
horizontal
cylindrical uncooled cyclone in circulating fluidized bed boilers. Such hot
cyclones
suffers from the same problems of uncooled vertical cyclones. Gorzegno in
Canadian
patent, 2081401, teaches the use of plurality of above type of horizontal
cylindrical
cyclone for building new CFB boilers. This system is also complex owing to its
cylindrical
construction. U.S patent nos 4,891,052, and no 4, 992,085 and Canadian patent
2,160,650 teach use oif uncooled impact type particle separators in CFB
boilers. Such
separators are geometric in shape and as such allow building compact CFB
boilers.
However, these separators work on the principle impact of solids on separator
surfaces.
Impact separation results in wear of the impacting surfaces. Furthermore
efficiency of
such separators are lower than those which works on the principle of
centrifugal
separation. Weitzke and Ganesh (CFB- Technology V, Science Press, Beijing, p.
289,1997) describe the use of a rectangular water cooled vertical cyclone for
use in
circulating fluidized bed boilers. Such separators have collection efficiency
higher than
that impact types separators. These are not suitable for revamping existing
boilers as it
2


CA 02344033 2001-04-18
requires a head room above the exit of the cyclone, which is not easily
available within
the existing structure of an old boiler.
SUMMARY OF THE INVENTION
One aspect of i:he present invention is an arrangement for particle collection
and
separation which is more efficient, easily adaptable to existing boilers and
cost effective
than other known systems and arrangements. It also provides a novel method for
converting an existing FFF boiler into CFB boiler.
In accordance with one aspect of the present invention there is provided
separators for use in a CFB boilers, wherein at least one separator is formed
as a
rectangular box with an open slit facing upstream into the flow of gas/solid
suspension,
when in use, and wherein holes on side walls allows clean gas to leave the
separator
chamber. Flow axis of the entering gas solid suspension is generally
perpendicular to
that of the gas leaving the separator.
In accordance with another aspect of the invention a plurality of separation
chambers are arranged in parallel with a common chamber for the clean gas.
In accordance with another aspect of the invention there is provided
rectangular
box shaped separators, wherein gas-solid mixture enters through a horizontal
slit
extending from the top of the front wall down to the outer periphery level of
the circular
exit of two vertical side walls. Two cylindrical pipes are placed horizontally
on the two
side walls. These tubes leave adequate room for the gas to enter from their
open end
inside the separator chamber. Clean gas leaves the separator chamber through
these
tubes. The solids are collected at the bottom of the separation chamber, from
where
they are removed appropriately.
In accordance with yet another aspect of the present invention, there is
provided
a method for adapting a fossil fuel fired boiler into a circulating fluidized
bed boiler
comprising the steps (a) installing a grid plate at lower section of a
furnace; (b) installing
fans under the grid plate to blow air up through the grid plate when in
operation; (c)
changing the shape of the water and steam carrying tubes to form a rectangular
separation chambers, (d) installing circular exits on side walls of the
separation
chambers; (e) installing a solids return system at the bottom of the
separation chamber
to recycle the solids back to the furnace; (f) providing particulate fuel
feeding devices; (g)
providing secondary air openings; (h) providing a fluidized bed ignition
system ; and (i)
providing means for draining ash from the furnace.
3


CA 02344033 2001-04-18
In accordance with another aspect of the present invention, there is provided
a
compact CFB boiler comprising (a) a grid plate at lower section of a furnace;
(b) fans
under the grid plate to blow air up through the grid plate when in operation;
(c)
rectangular gas-solid separation chambers formed of water and steam carrying
tubes,
(d) circular exits on side walls of the separation chambers; (e) solids return
systems at
the bottom of the separation chamber to recycle the solids back to the
furnace; (f) fuel
feeding devices; (g) secondary air openings; (h) a fluidized bed ignition
system ; and (i)
means for draining ash from the furnace.
Advantages of the invention over prior devices:
The advantages and benefits of the present device for separating solids from a
mixture
of gas and solids include the followings:
1. The traditional means of separating solids from gas is a cylindrical
vertical
cyclone. Such a device with a tapered bottom requires a large cylindrical
volume
of space. It is very difficult to integrate that in the existing structure of
a boiler. It
would, therefore, require a large amount of space outside the existing boiler.
In
most older or even newer generation boilers such space is unavailable. Thus
this
type of conventional device does not permit conversion of an existing flame
fired
boiler into circulating fluidized bed firing. The present device does not
require that
space. Its design allows it to be easily fitted inside existing walls of the
fossil fuel
fired boiler.
2. The vertical cyclone uses a tapered conical hopper for solid collection,
construction of which is complex. Also, it is difficult to incorporate it
within the
generally rectangular configuration of conventional boilers. The present
device
does not use such a conical section. Thus the above difficulty is absent here.
3. The conical section makes it difficult to construct it out of boiler tubes.
A complex
tube arrangement is required to do that. Present device uses more regular
geometric shape, which makes it easily amenable to boiler tube construction.
4. One type of horizontal cylindrical cyclone is used which do not require the
conical
collection hopper. This device solves one problem, but its cylindrical shape
does
not allow it to blend in the rectangular geometric shape of conventional
boilers.
So it is difficult to adapt it in the existing boiler configuration. The
present device
does not use such a cylindrical body. Thus it can be used for both new CFB
4


CA 02344033 2001-04-18
boiler of regular geometry and for adopting existing fossil fuel fired boilers
to CFB
firing.
5. One type of square cyclone is used in some CFB boilers. Here the gas exits
from
the top. Thus a large space is required above the separator floor. It is very
difficult to find such space in an existing boiler. The present device does
not need
this additional space because here the gas exits from the sides of the boiler.
Thus it can be easily used for converting FFF boiler into CFB firing.
6. The walls and the roof of the present device are straight. This allows easy
manufacture if made of refractory or steel. Furthermore, it can be easily made
of
existing superheater panels or water wall simply through appropriate
repositioning.
7. In conventional impact type separators the gas-solid mixture enters the
device
from an entry section at a high velocity. As a result the gas-solid mixture
often
hits the opposite wall with a high velocity resulting in erosion of this part
of the
separator. The present device incorporates a novel arrangement in this part of
the wall which greatly reduces the chances of erosion.
8. Unlike circular cyclone the present device is modular in construction. One
can
increase the throughput of the device simply by increasing number of geometric
shaped separation modules.
Use of the device
1. This device can be used for separating gas from a mixture of gas and solid
or
solids from a mixture of solid and gas.
2. This device can be used for separating solids from a mixture of solid-
liquid or
liquid from a mixture of liquid-solid
3. The device can be used for converting an existing fossil fuel fired boiler
into
circulating fluidized bed firing
4. The device can be used to enhance the combustion efficiency of a bubbling
fluidized bed bailer by recycling unburnt carbon in the bed
5. The device can be used to design compact and economic circulating fluidized
bed boilers
6. The device can be used for.designing and building high performance and
compact circulating fluidized bed reactor.
7. The device can be used for heat exchange purposes
8. The device for can be used for generation of steam


CA 02344033 2001-04-18
9. The device can be used for superheating steam
10. The device can be used to reduce erosion of gas-solid separation device
11. The device can be used for moving solids after collection from one chamber
to
another predefined chamber.
12. The device can be used for pre-cleaning dust-laden gases entering a heat
exchanger
13. The device obviates the need of external cyclone of a circulating
fluidized bed
boiler
14. The device can be used to eliminate the external stand pipe of a
circulating
fluidized bed boiler
15. The device can be used to cool the flue gas entering the back pass of a
boiler
16. The device can be used to reduce the erosion potential of downstream heat
exchanger surfaces of a boiler.
17. The device can be used to reduce the use of refractory in a circulating
fluidized
bed
18. The device can be used to reduce the start up time of a circulating
fluidized bed
boiler
19. The device can be used to improve the separation efficiency of impact type
or
vertical cavity separators where solids are separated through multiple changes
in
the flow direction.
20. The device could reduce the maintenance cost of equipment using gas-solid
separation.
Brief description of the Drawings
The present invention will be further understood from the following
description by way of
example with reference to the drawings in which:
Fig. 1 is an isometric view of a separator with single cylindrical exit
Fig. 2 is a cross section view of a separator with single cylindrical exit and
collection chute tapered on both sides
Fig. 3 shows a separator with single taper collection chute. Fig 3a shows
notch
with shelves. Fig. 3b shows rear wall with shelves alone.
Fig. 4 shows the cross-section elevation taken through two parallel separators
with cylinder exits. The vertical section is taken through the centre line of
the gas exit.
6


CA 02344033 2001-04-18
Fig. 5 shows two locations of the exit section with reference to the
separator. It
also shows the erosion protecting layer on the rear wall.
Fig 6 shows three arrangements of gas exit from the separator. It also shows
parallel arrangements, in which all separators would not necessarily have
different exit
design as shown here.
Fig. 7 shows an arrangement for conversion of a FFF boiler into circulating
fluidized bed boiler by using the novel separators.
Fig. 8 shows an isometric view of use of multiple rows of novel separators
Detail description of the preferred embodiment
One embodiment of the separator is shown in figure 1. The box shaped separator
comprises four vertical walls (21, 20, 18 & 19) and a horizontal roof (23).
The bottom
of the separator (7) is a collection chamber for dust. One cylindrical exit
(3) is located
on the vertical side wall (20). A rectangular opening (1 ) is located at the
top of the
front vertical wall ('19). This opening is located such that its flow axis is
perpendicular
to axis of the cylindrical exit (3), also the suspension enters tangent to the
an
imaginary cylinder passing through the gas exit. The exit (3) is generally on
the
vertical centre line of the side wall (20). Dust laden gas or gas-solid
suspension
enters the separatar through opening (1). Relatively clean gas leaves the
separator
though exit (3) into the exit chamber (6) outside the side wall (20).
Separated solids
leaves the separator through dust channel (7) which may exit through the front
wall
(19) or behind this wall.
The gas solid suspension is made to enter the separator through section (1 ).
The
axis of this entry section (1) is tangent to the exit section. The upper edge
of the exit
pipe (3) is below but as close to the lowest edge of the entry section (1) as
possible
to maintain the tangent entry of the dust laden gas (Fig. 2). The shape of the
separation chamber induces a flow pattern as a result of which the gas solid
mixture
try to travel straight: towards the rear wall (18), but the presence of the
rear wall and
the resulting pressure gradient make the mixture move around a near circular
path
around the axis of the exit section (3). The solids, by virtue of its higher
momentum
tend to move towards the rear wall continuing on its original travel path
while the gas
which has lower momentum follows the pressure gradient. While travelling in
circular
trajectory, centrifugal force drives the solids towards the wall where the gas
velocity
is too low to convey the solids further. Solids are, therefore, separated from
the gas
7


CA 02344033 2001-04-18
carrying them Then the solids drop under gravity. The collected solids drop
into the
hopper (5) from where it slides down into the solid collecting chute (7).
The dust collection section (5) can be made of vertical walls which are
essentially
continuation of side walls (20, 21 ) as shown in Fig. 1 and that of the front
wall (19) as
shown in Fig. 3. The rear wall (18) may also drop vertically without creating
separate
collecting chute. In another preferred arrangement shown in Figure (3), the
rear wall
(18) is bent at an angle exceeding the angle of repose of the solids and then
drops
vertically forming the collecting chute (7). This collection chute is made of
uncovered
metal for cold solids. For hot solids it is covered high temperature
refractory. In
another preferred arrangement it is made of heat absorbing surfaces carrying
fluids
being heated. The dust collection chute (7) is made circular in cross-section
like a
stand pipe in places where the neighbouring configuration demands it.
Another embodiment of the invention is shown in figure (4). Here two
cylindrical
exits are located on two vertical side walls (20, 21 ). Gas-solid suspension
enters
through the entry section (1 ) in a direction tangent to an imaginary cylinder
passing
through the circular exit sections (3, 3). The gas after it is separated from
the
suspension leaves the separator chamber (2) from both sides of the separator.
The
solids drop into the collecting hopper (5). In a preferred arrangement,
cylindrical
sections (3,3) are replaced with the circular exits (9,9) as shown in Fig. 5.
In another
preferred arrangement (Fig. 5) the exit cylinder (10) is flush with the inner
face of the
side walls (20, 21 ). In another arrangement (Fig. 5) the exit cylinder (8) is
flush with
the outer face of the side walls (21, 20).
The rear wall is subject to wear due to direct impact of solids. This wall is
protected against the erosion potential by using one of three alternative
designs. In
the first embodiment shown in figure 5, the vertical rear wall (18) is covered
with
wear resistant materials like refractory (24). In another embodiment, shown in
figure
3a, a number of horizontal shelves of varying size and shape and size as shown
are
attached to rear wall (18). Solids trapped between these shelves protect the
target
zone of the rear wall from erosion.
In another embodiment shown in figure 3b, a notch (4) is created in the upper
part of the rear wall (18) directly opposite to the entry section (1 ). While
in operation,
a static layer of solids sits here. The solids abrade against these solids
saving the
wall. In a still improved design a number of horizontal shelves (17) are
located inside
this notch for better capture of the solids.
8


CA 02344033 2001-04-18
The exit hole (1) of the separator is generally located on the vertical centre
line
of the side wall as shown on figure 5(a). In a preferred design as shown in
figure 5b,
the exit hole is located on either side of the centre line according the flow
field. Here
the exit is located at the centre of the vortex created by the tangentially
entering gas
solid. Thus such location of the exit (fig. 5b) minimizes flow separation
around the
exit section (3). This would enhance solid separation efficiency of the
separator.
In another embodiment of the separator, more than one separators are located
parallel to each other. This arrangement is shown in figures 4, 6 and 8. In
fig.4 two
separators are placed side by side each sharing a common exit chamber (6). The
front wall (19) is a continuous with discrete rectangular openings in front
wall (19) of
the separator chambers (2). The rear wall (18) is not necessarily continuous.
It
covers only the individual separator chambers. In case of multiple parallel
separators, the last separator could have only either one exit or only one
exit
chamber as shown in figure 4. Here all separators are shown to use cylindrical
exits.
In Fig. 6, three alternative arrangement of separator's exit are shown. For
the sake of
explanation alternative designs of exit section each separator are shown to
have
different exit design. However, it is not a requirement for parallel
arrangement. Fig. 8
shows isometric view of two rows of parallel separators set for optimum
utilization of
space. Here the second row receives gas-solid suspension from the top of exit
section (6) of the first row. Such an arrangement makes it easy to adapt such
separators within limited space available in an existing boiler, which is
required for
conversion of an existing FFF boiler into CFB boiler.
The entry sectian (1) generally covers the entire width and height of the
front wall
above the periphery line of the exit cylinder (3). In a preferred shape the
height of the
entry section is reduced from the top.
In a preferred embodiment all walls (21,20, 23, 18 & 19) are made of panels of
heat exchanger tubes. The hopper (5) and chute (7) are also made of heat
exchanger tubes obviating the need of refractory and saving additional cost
and
space required for heating surfaces required in boilers.
In another preferred shape the entry section (1) is narrower than the width of
the
separator.
In another embodiment this separator is used in existing boilers to convert it
into
circulating fluidized bed firing. Figure 7 shows one possible arrangement. The
entrance (1 ) of the separator is located near the top of the rear wall of the
furnace
9


CA 02344033 2001-04-18
(28) of the existing boiler. Lower section of the furnace comprises a grid
plate (29) for
entry of primary air. The lower section (15) of the furnace is lined with
refractory,
while the upper section (28) is made of water wall tubes. Secondary air enters
through a plurality of openings (16) located above the refractory lined lower
section
(15). The air velocity is controlled such that it creates the appropriate
hydrodynamic
condition in the furnace for circulating fluidized bed operation, where gas-
solid
suspension continuously leave the upper section (28) of the furnace and enters
the
separator through openings (1 ) and are recycled back through (7). The
suspension
enters one or multiple separators stacked in parallel. The hopper (5) is
slanted
towards the furnace (28). Solids after separation drops down rectangular
channels
(7). All sides of the channel are made of heat exchanger tubes as such they
serve as
heat exchanger. The solids drops into a loop seal (13) located at the bottom
of the
channel (7). The loop seal (13) comprises two chambers. The first chamber
called
supply chamber (7) is the bottom of the collection chute (7), which is closed
at the
bottom but opened on sides. Only a small amount of air may be passed through
its
bottom to facilitate solids transfer. The second chamber (12) of the loop seal
is
located adjacent to this. Depending upon the space available it can be located
either
in front as shown in figure 7 or on sides. This chamber, defined as recycle
chamber
(12) is fluidized by air which enters through a grid located at its base. The
hot
combustion gas, after cleaned of solids, leaves through exit (3) and enters
the set of
exit chambers (6) located in between adjacent separation chambers (2). The hot
gas
flows down the exit chamber (6) and then over heat exchangers tubes (11)
located
downstream of the separators and finally leaves the boiler through (17). These
heat
exchanger surfaces are modified within the existing confines of the boiler to
absorb
the required amount of heat from the combustion gas cooling it down and to
contribute to the generation of steam as per the design parameters of the
boiler. For
initial ignition of the fuel a start up burner is located in the air box below
the grid.
Preheated air and hot gas from the burner enters the furnace and heat the
granular
solids fluidized in the furnace.
In one particular application this type of separator is used to revamp old
plant. In
particular design the rear furnace wall tubes are bent to make room for entry
of gas
solid mixture from the furnace into the separation chamber. Panels of steam
tubes
form the separation chamber. These tubes leave one common gas exit passage
between two separators forming multiple chambers. However, in the end chamber


CA 02344033 2001-06-05
the cleaner gas passage is formed by between the vertical side wall of the
existing
boiler and last wall of the separator. The steam tubes bends at an acute angle
to form
the collection hopper. The same tube panel extends below down to the loop
seal. On
both sides of the dip leg just formed. On both sides of the collection chamber
there are
one fluidized bed that serves as the recycle chamber. Solids from these two
fluidized
bed overflow into the main furnace. These solids enter the main furnace
through
openings made in the water wall by bending the tubes away from the furnace.
Thus the
bottom of the empty gas passage between two separators form the recycle
chamber of
the loop seal while the bottom of dip leg of the separator is the supply
chamber of the
loop seal.
In another embodiment a compact circulating fluidized bed boiler is built
following
the above description except that furnace which is sized and shaped to give
optimum
design.
In one embodiment of the design the entry velocity of the gas-solid through (1
) is
within 20-30 m/s to give the ideal separation efficiency.
11

A single figure which represents the drawing illustrating the invention.

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Admin Status

Title Date
Forecasted Issue Date Unavailable
(22) Filed 2001-04-18
(41) Open to Public Inspection 2001-10-19
Examination Requested 2003-10-22
Withdrawn Application 2004-12-20

Abandonment History

Abandonment Date Reason Reinstatement Date
2003-04-22 FAILURE TO PAY APPLICATION MAINTENANCE FEE 2003-06-23
2004-04-19 FAILURE TO PAY APPLICATION MAINTENANCE FEE

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $150.00 2001-04-18
Reinstatement: Failure to Pay Application Maintenance Fees $200.00 2003-06-23
Maintenance Fee - Application - New Act 2 2003-04-22 $50.00 2003-06-23
Request for Examination $200.00 2003-10-22
Current owners on record shown in alphabetical order.
Current Owners on Record
BASU, PRABIR
Past owners on record shown in alphabetical order.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Document
Description
Date
(yyyy-mm-dd)
Number of pages Size of Image (KB)
Claims 2001-06-05 3 129
Claims 2001-04-18 4 127
Representative Drawing 2001-09-19 1 5
Abstract 2001-04-18 1 12
Description 2001-04-18 10 554
Drawings 2001-04-18 8 182
Description 2001-06-05 10 553
Cover Page 2001-10-12 1 29
Correspondence 2001-05-15 1 25
Assignment 2001-04-18 3 87
Correspondence 2001-04-18 1 50
Prosecution-Amendment 2001-06-05 14 687
Correspondence 2001-06-05 5 186
Prosecution-Amendment 2003-10-22 1 24
Correspondence 2003-05-21 1 2
Fees 2003-04-29 1 18
Fees 2003-06-23 1 23
Correspondence 2004-12-20 1 19
Correspondence 2004-12-23 1 11