U.S. patent application number 11/937086 was filed with the patent office on 2009-05-14 for impulse combustion cleaning system and method.
This patent application is currently assigned to General Electric Company. Invention is credited to Michael J. Bultman, David M. Chapin, Anthony J. Dean.
Application Number | 20090120336 11/937086 |
Document ID | / |
Family ID | 40622508 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090120336 |
Kind Code |
A1 |
Chapin; David M. ; et
al. |
May 14, 2009 |
IMPULSE COMBUSTION CLEANING SYSTEM AND METHOD
Abstract
A system for removing accumulated debris from a surface of a
vessel. The system comprises a vessel having a surface to be
cleaned. A impulse cleaning device defines a combustion chamber in
which combustible fuel and air are mixed and ignited to produce
supersonic combustion that is directed at the surface to be cleaned
within the vessel. A sensor is associated with the impulse cleaning
device. The sensor is for detecting a condition within the impulse
cleaning device and generating a signal in response to a detected
condition.
Inventors: |
Chapin; David M.; (Kansas
City, MO) ; Dean; Anthony J.; (Scotia, NY) ;
Bultman; Michael J.; (Jacksonville, FL) |
Correspondence
Address: |
GE ENERGY GENERAL ELECTRIC;C/O ERNEST G. CUSICK
ONE RIVER ROAD, BLD. 43, ROOM 225
SCHENECTADY
NY
12345
US
|
Assignee: |
General Electric Company
|
Family ID: |
40622508 |
Appl. No.: |
11/937086 |
Filed: |
November 8, 2007 |
Current U.S.
Class: |
110/236 ;
110/185; 110/346; 134/113 |
Current CPC
Class: |
F28G 7/005 20130101;
F28G 7/00 20130101; F23D 91/02 20150701; F23J 3/023 20130101; F23C
15/00 20130101; F23N 5/16 20130101; F23N 5/123 20130101; F23N 1/022
20130101 |
Class at
Publication: |
110/236 ;
110/185; 110/346; 134/113 |
International
Class: |
F23G 5/00 20060101
F23G005/00; F23N 5/00 20060101 F23N005/00 |
Claims
1. A system for removing accumulated debris from a surface of a
vessel, the system comprising: a vessel having a surface to be
cleaned; a impulse cleaning device defining a combustion chamber in
which combustible fuel and air are mixed and ignited to produce
supersonic combustion that is directed at the surface to be cleaned
within the vessel; and a sensor associated with the impulse
cleaning device, the sensor for detecting a condition within the
impulse cleaning device and generating a signal in response to a
detected condition.
2. The system of claim 1 wherein the sensor detects a supersonic
combustion event in the impulse cleaning device.
3. The system of claim 2 further including an apparatus that
generates an alarm signal in response to a predetermined period of
time elapsing before supersonic combustion in the impulse cleaning
device is detected by the sensor.
4. The system of claim 1 wherein the sensor generates a signal as a
function of the combustion in the impulse cleaning device.
5. The system of claim 1 further including a controller for
receiving the signal generated by the sensor to control production
of combustion in response to the signal.
6. The system of claim 5 in which the controller controls
production of combustion by controlling at least one of the
delivery of combustible fuel to the combustion chamber, the
delivery of air to the combustion chamber and the delivery of
ignition energy to the combustion chamber.
7. The system of claim 1 wherein the sensor is selected from the
group comprising a strain gage, an accelerometer, an acoustic
detection device, a pressure gage and an ion probe.
8. The system of claim 7 wherein the sensor is a strain gage
mounted outside of the combustion chamber of the impulse cleaning
device to sense displacement of the impulse cleaning device.
9. The system of claim 7 wherein the sensor is an accelerometer
mounted outside of the combustion chamber of the impulse cleaning
device to sense acceleration of a component of the impulse cleaning
device.
10. The system of claim 7 wherein the sensor comprises an ion probe
spaced from a know location a predetermined distance along the
impulse cleaning device, the ion probe being in communication with
the combustion chamber and being capable of detecting the movement
of a combustion event past the ion probe.
11. A cleaner for removing accumulated debris from a surface of a
vessel, the cleaner comprising: a impulse cleaning device defining
a combustion chamber in which combustible fuel and air are mixed
and ignited to produce combustion that results in a shock wave
directed at the surface to be cleaned within the vessel; and a
sensor operably connected with the impulse cleaning device, the
sensor detecting a condition of the impulse cleaning device and
generating a signal in response to a detected condition.
12. The cleaner of claim 11 wherein the sensor detects supersonic
combustion in the impulse cleaning device.
13. The cleaner of claim 2 further including an apparatus that
generates an alarm signal in response to a predetermined period of
time elapsing before supersonic combustion in the impulse cleaning
device is detected by the sensor.
14. The cleaner of claim 11 wherein the sensor generates a signal
as a function of the combustion in the impulse cleaning device.
15. The cleaner of claim 14 wherein the sensor generates a signal
having frequency information to determine the quality of the
combustion as a function of a change in the frequency
information.
16. The cleaner of claim 15 further including a controller to
adjust detonation parameters based on the sensor signal frequency
information.
17. The cleaner of claim 14 wherein the sensor generates signal
intensity level information to determine the quality of the
combustion as a function of a change in intensity level.
18. The cleaner of claim 17 further including a controller to
adjust detonation parameters based on the sensor signal intensity
level information.
19. The cleaner of claim 14 further including a windowed counter to
determine the quality of the combustion event by establishing the
duration of combustion
20. The cleaner of claim 14 further including a sensor having a
local integrated gain stage to enhance the transmission of the
signal from the sensor to the controller.
21. The cleaner of claim 11 further including a controller for
receiving the signal generated by the sensor to control production
of combustion in response to the signal.
22. The cleaner of claim 21 in which the controller controls
production of combustion by controlling at least one of the
delivery of combustible fuel to the combustion chamber, the
delivery of air to the combustion chamber and the delivery of
ignition energy to the combustion chamber.
23. The cleaner of claim 11 wherein the sensor is selected from the
group comprising a strain gage, an accelerometer, an acoustic
detection device, a pressure gage and an ion probe.
24. A method for removing accumulated debris from a surface within
a vessel, the method comprising: providing a impulse cleaning
device defining a combustion chamber; delivering a flow of air to
the combustion chamber; delivering a flow of combustible fuel into
the flow of air in the combustion chamber; mixing the combustible
fuel and air within the combustion chamber; periodically igniting
the fuel and air mixture to produce supersonic combustion;
directing the supersonic combustion into the vessel at a surface to
be cleaned to loosen and remove accumulated debris from the surface
of the vessel; and sensing the supersonic combustion in the impulse
cleaning device and generating a signal in response to sensing the
supersonic combustion.
25. The method of claim 24 further including the step of generating
an alarm signal in response to a predetermined period of time
elapsing before supersonic combustion in the impulse cleaning
device is sensed.
26. The method of claim 24 further including the step of
controlling production of combustion as a function of the signal
generated in the sensing step by controlling at least one of the
delivery of combustible fuel to the combustion chamber, the
delivery of air to the combustion chamber and the delivery of
ignition energy to the fuel and air mixture in the combustion
chamber.
Description
BACKGROUND
[0001] The invention relates generally to an impulse combustion
cleaning system. More specifically, the invention relates to
sensing a condition in the impulse combustion cleaning system.
[0002] Industrial boilers operate by using a heat source to create
steam from water or another working fluid, which can then be used
to drive a turbine in order to supply power. The heat source may be
a combustor that burns a fuel in order to generate heat, which is
then transferred into the working fluid via a heat exchanger.
Burning the fuel may generate residues that can be left behind on
the surface of the combustor or heat exchanger. Such buildups of
soot, ash, slag, or dust on heat exchanger surfaces can inhibit the
transfer of heat and therefore decrease the efficiency of the
system. Periodic removal of such built-up deposits maintains the
efficiency of such boiler systems.
[0003] Pressurized steam, water jets, acoustic waves, and
mechanical hammering have been used to remove built-up deposits.
These systems can be costly to maintain and the effectiveness of
these systems varies.
[0004] A supersonic combustion or impulse cleaning system has
recently been used in an attempt to remove built-up deposits.
Supersonic combustion events create strong impulse waves that
remove the built-up deposits and accumulated debris from the heat
exchanger surfaces. Typically, the impulse cleaning system would
need to be located in an area either visually or audibly accessible
by an operator or attendant in order to verify operation of the
device. Sensors, such as pressure or temperature probes, can be
used but these must be located such that the sensors are exposed to
hot and sometimes caustic gases of the combustion process. This
exposure can decrease the service life of the sensors.
[0005] Therefore, there is a need for development of effective and
reliable impulse cleaning systems.
BRIEF DESCRIPTION
[0006] An effective and reliable impulse cleaning system for
removing built-up deposits and accumulated debris from a surface
within a vessel is provided, according to one aspect of the
invention. The system includes a vessel having a surface to be
cleaned. The system also includes an impulse cleaning device that
defines a combustion chamber in which combustible fuel and air are
mixed and ignited to produce supersonic combustion that is directed
at the surface to be cleaned within the vessel. A sensor is
associated with the impulse cleaning device. The sensor is for
detecting a condition within the impulse cleaning device and
generating a signal in response to a detected condition.
[0007] According to another aspect of the invention a cleaner for
removing built-up deposits and accumulated debris from a surface of
a vessel is provided. The cleaner includes an impulse cleaning
device defining a combustion chamber in which combustible fuel and
air are mixed. The fuel and air mixture is ignited to produce
supersonic combustion that is directed at a surface to be cleaned
within the vessel. A sensor is operably connected with the impulse
cleaning device. The sensor detects a condition within the impulse
cleaning device and generates a signal in response to a detected
condition.
[0008] According to yet another aspect of the invention a method
for removing built-up deposits and accumulated debris from a
surface within a vessel is provided. The method comprises the steps
of providing an impulse cleaning device defining a combustion
chamber. A flow of air is delivered into the combustion chamber. A
flow of combustible fuel is delivered into the flow of air in the
combustion chamber. The combustible fuel and air are mixed within
the combustion chamber. The fuel and air mixture is periodically
ignited to produce supersonic combustion. The supersonic combustion
is directed into the vessel at a surface to be cleaned to loosen
and remove accumulated debris from the surface of the vessel. The
supersonic combustion in the impulse cleaning device is sensed and
a signal is generated in response to detecting the supersonic
combustion.
DRAWINGS
[0009] These and other features, aspects, and advantages of the
invention will be better understood when the following detailed
description is read with reference to the accompanying drawing, in
which:
[0010] FIG. 1 is a schematic representation of an impulse cleaning
system according to one aspect of the invention;
[0011] FIG. 2 is an enlarged schematic representation of a portion
of the impulse cleaning system illustrated in FIG. 1;
[0012] FIG. 3 is a schematic representation of an impulse cleaning
system according to another aspect of the invention; and
[0013] FIG. 4 is an enlarged schematic representation of a portion
of the impulse cleaning system illustrated in FIG. 3.
DETAILED DESCRIPTION
[0014] Soot or other buildup on heat exchanger surfaces in
industrial boilers can cause losses in the overall efficiency of
the boiler due to a reduction in the amount of heat that is
actually transferred into a working fluid. This is often reflected
by an increase in the exhaust gas temperature from the process, as
well as an increase in the fuel-burn rate required to maintain
steam production and a given energy output. Traditionally, the
complete removal of buildup from the heat exchanger surfaces
requires the boiler to be shut down while a cleaning process is
performed. Online cleaning techniques generally have high
maintenance costs or incomplete cleaning results.
[0015] In one aspect of the invention, an impulse cleaning system
located external to the boiler is used to generate a series of
detonations or quasi-detonations that are directed into a fouled
portion of the boiler. The resulting impulse waves impact boiler
surfaces and loosen buildup from the surfaces. The loosened debris
is free to fall to the bottom of the boiler and then may exit the
boiler through hoppers. As will be discussed below, the use of
repeated impulses has advantages over traditional cleaning
techniques, such as steam blowers or purely acoustic soot removal
devices.
[0016] It is also desirable that a cleaning system for a boiler be
able to operate to quickly remove buildups in order to minimize the
downtime for the boiler. It is also desirable that the installation
of such cleaner be reliably monitored to assure that it is
functioning and functioning at a high level of performance. An
impulse based cleaning system that can provide these and other
features will be described in more detail below.
[0017] As used herein, the term "impulse cleaning system" will
refer to a device or system that produces both a pressure rise and
velocity increase from the detonation or quasi-detonation of a fuel
and oxidizer. The impulse cleaning system can be operated in a
repeating mode to produce multiple detonations or quasi-detonations
within the device. These detonations or quasi-detonations form a
pulse of energy in the form of a shock wave that can be used for
cleaning built-up deposits and accumulated debris from surfaces of
a boiler vessel. A "detonation" is a supersonic combustion event in
which a shock wave is coupled to a combustion zone. The shock wave
is sustained by the energy release from the combustion zone,
resulting in combustion products at a higher pressure than the
combustion reactants. For simplicity, the term "detonation" as used
herein will be meant to include both detonations and
quasi-detonations. A "quasi-detonation" is a supersonic turbulent
combustion process that produces a pressure rise and velocity
increase higher than a pressure rise and velocity increase produced
by a sub-sonic deflagration wave.
[0018] Exemplary impulse cleaning systems, some of which will be
discussed in further detail below, include an ignition device for
igniting a fuel/oxidizer mixture, and a detonation chamber or zone
in which pressure wave fronts initiated by the combustion coalesce
to produce a detonation wave. Each detonation or quasi-detonation
is initiated either by an external ignition source, such as a spark
discharge, laser pulse, heat source, or plasma igniter, or by gas
dynamic processes such as shock focusing, auto ignition or an
existing detonation wave from another source (cross-fire ignition).
The detonation chamber geometry allows the pressure increase behind
the detonation wave to drive the detonation wave and also to blow
the combustion products out of the impulse cleaning system.
[0019] Various chamber geometries can support detonation formation,
including round chambers, tubes, resonating cavities and annular
chambers. Such chambers may be of constant or varying
cross-section, both in area and shape. Exemplary chambers include
cylindrical tubes and tubes having polygonal cross-sections, such
as, for example, hexagonal tubes or including obstacles to promote
detonation, such as disclosed in U.S. patent application Ser. No.
11/669,582 filed Jan. 31, 2007. As used herein, "downstream" refers
to a direction of flow of at least one of fuel or oxidizer.
[0020] One embodiment of an exemplary impulse cleaning device 20
suitable for use with an industrial boiler is illustrated
schematically in FIG. 1. The impulse cleaning system 20, according
to one aspect of the invention, includes an impulse cleaning device
22, a sensor 24 associated with the impulse cleaning device and a
monitor/controller 26. The impulse cleaning system 20 is
constructed and mounted such that it can direct shock waves or
cleaning pulses of energy E at a wall 40 of a boiler vessel.
[0021] A plurality of tubes 42 are located in the boiler vessel and
supported by wall 40. The cleaning pulses of energy E are also
directed at the tubes 42. The wall 40 and tubes 42 tend to have
soot or other buildup resulting from a combustion process in the
boiler vessel that can cause losses in the overall system
efficiency due to a reduction in the amount of heat that is
actually transferred into a working fluid flowing through the
tubes.
[0022] The impulse cleaning device 22 has a tubular body 60 that
extends longitudinally with an open "horn" end 62 directed at the
wall 40 and tubes 42 of a boiler vessel to be cleaned. The body 60
has an opposite closed head end 64 and air inlet ports 66 and a
fuel inlet port 68. The body 60 defines a combustion chamber 80
that has a deflagration zone "a" and a detonation zone "b". In the
illustrated embodiment, the impulse cleaning device 22 is mounted
to structure by at least one bracket 82 (FIG. 2) so the impulse
cleaning device can be used to perform a cleaning operation of the
boiler vessel.
[0023] The head end 64 of the impulse cleaning device 22 has its
air inlet ports 66 connected to a source of air that can be
provided under pressure through a valve 102 to deliver a flow of
air P to the combustion chamber 80. This air source is used to fill
and purge the combustion chamber 80, and also provides air to serve
as an oxidizer for the combustion of the fuel. The inlet ports 66
may be connected to a facility air source such as an air compressor
(not shown).
[0024] The fuel inlet port 68 is located at the head end 64 of the
impulse cleaning device 22 and extends in a direction transversely
relative to the air inlet ports 66. The fuel inlet port 68 is
connected to a supply a flow of fuel F to the combustion chamber 80
through valve 104. The fuel F will be burned within the combustion
chamber 80. The fuel F that is supplied to the combustion chamber
80 is mixed with the flow of air P.
[0025] The mixing of the fuel F and air P may be enhanced by the
relative arrangement of air inlet ports 66 and the fuel inlet port
68. For example, a plurality fuel inlet ports 68 may be provided
around the periphery of the combustion chamber 80. By placing the
fuel inlet port or ports 68 at a location such that fuel F is
injected into regions of high turbulence generated by the flow air
P, the fuel and air may be more rapidly mixed to provide a more
readily detonatable fuel/air mixture. As with the air inlet ports
66, the fuel inlet ports 68 may be disposed at a variety of axial
and circumferential positions. The fuel inlet ports 68 may be
aligned to extend in a purely radial direction, or may be canted
axially or circumferentially with respect to the radial
direction.
[0026] Fuel F is supplied to the fuel inlet ports 68 through the
valve 104 that controls when fuel is allowed into the combustion
chamber 80 of the impulse cleaning device 22. The valve 104 may be
disposed within the fuel inlet port 68, or may be disposed upstream
in a supply line that is connected to the fuel inlet port. The
valve 104 may be a solenoid valve and may be controlled
electronically by the controller 26 to open and close in order to
regulate the flow of fuel F into the combustion chamber 80. The
controller 26 may also electronically control the valve 102 and the
flow of air P to the combustion chamber 80.
[0027] As illustrated in FIG. 1, an ignition device 120 is located
near the head end 64 of the impulse cleaning device 22. In the
illustrated embodiment, the ignition device 120 ignites the
fuel/air mixture to create combustion C in the deflagration zone a.
The ignition device 120 may take various forms. In particular, the
ignition device 120 need not produce immediate detonation of the
fuel/air mixture in every embodiment. However, the ignition device
120 provides sufficient energy for ignition that allows the
combustion of the fuel/air mixture which can transition to a
supersonic shock wave D, within the detonation zone b of the
combustion chamber 80. The ignition device 120 may be connected to
the controller 26 to operate the ignition device at desired or
periodic times.
[0028] The controller 26 may be of any suitable type or combination
of components to control the timing and operation of various
systems, such as the valves 102, 104 and ignition device 120. As
used herein, the term controller 26 is not limited to just those
integrated circuits generally referred to in the art as a
controller, but broadly refers to a master networked computer 128,
processor, a microprocessor, a microcontroller, a programmable
logic controller, an application specific integrated circuit, other
programmable circuits suitable for such purposes and software or
any suitable combination thereof.
[0029] The impulse cleaning device 22, constructed according to one
aspect as illustrated in FIG. 1, includes the elongate body 60
defining the combustion chamber 80 that extends from the head end
64 to the horn end 62. Combustion of the fuel/air mixture takes
place within the combustion chamber 80. In general, the combustion
C will progress from the ignition device 120 through the mixture
that is within the combustion chamber 80. FIG. 1 illustrates a
cross-section of body 60 in the shape of a substantially round
cylinder having a constant cross-sectional area. It will be
apparent that other configurations of the body 60 and combustion
chamber 80 are possible.
[0030] The body 60 may contain a number of obstacles (not shown) in
the combustion chamber 80 disposed at various locations along the
length of the body. The obstacles are used to enhance the
combustion as it progresses along the length of the body 60, and to
accelerate the combustion front C into a supersonic shock wave D
before the combustion front reaches the horn end 62 at the
downstream end of the body. The body 60 and obstacles may be
fabricated using a variety of materials suitable for withstanding
the temperatures and pressures associated with the repeated
detonations. Such materials include but are not limited to:
Inconel, stainless steel, aluminum and carbon steel.
[0031] The horn end 62 is formed as a diverging chamber that is
connected directly to the body 60 of the impulse cleaning device
22. It will be apparent that although the diverging chamber need
not be in direct contact with the impulse cleaning device 22, it is
desirable that the combustion chamber 80 of the impulse cleaning
device is in fluid flow communication with the diverging chamber of
the horn end 62. The inner surface of the combustion chamber 80 is
smooth and substantially circular in cross-section normal to the
longitudinal central axis of the combustion chamber. It will be
apparent hat other cross sectional shapes are also possible, as
well as other axial profiles for the diverging chamber. Obstacles
may also be placed in the flow, which can create alternate cross
section profiles.
[0032] The cleaning system 20 incorporating the impulse cleaning
device 22 uses supersonic shock waves D that form cleaning energy E
to loosen accumulated debris, deposits and coatings that can
accumulate on the walls 40 and tubes 42 of a boiler vessel or other
device. High pressure fluid flow that follows the detonation helps
blow the loosened material away from the cleaned surfaces. In
operation, the impulse cleaning device 22 creates a supersonic
shock wave D and its associated high-pressure flow from a
combustion cycle, which is preferably repeated at high frequency.
The impulse cleaning devices 22 can operate at frequencies of less
than 1 Hz up to 100 Hz. Each combustion cycle generally includes a
fill phase, an ignition event, a flame acceleration into detonation
or supersonic phase, and a blowdown phase.
[0033] A single occurrence of a fuel fill phase, a combustion
ignition, an acceleration of the flame front to supersonic, and the
blow down and purge of the combustion products will be referred to
as "a combustion cycle" or "a detonation cycle". The portion of
time that the impulse cleaning system 20 is active is referred to
as "cleaning operation". Time when the vessel to be cleaned is
being actively used for its purpose will be referred to as "boiler
operation". As noted above, the parts to be cleaned need not be
part of a boiler vessel; however, for simplicity of reference, the
term "boiler operation" will be used to refer to the operation of
any device being cleaned by the cleaning system 20.
[0034] One advantage of the cleaning system 20 is that, unlike
other cleaning Systems, there is no need to shut down the boiler
vessel or other parts being cleaned in order to operate the
cleaning system. Specifically, it is possible for the cleaning
operation to take place during the boiler operation. The cleaning
system 20 need not be run continuously during the boiler operation.
However, by providing the flexibility to operate the cleaning
system on a regular cycle during boiler operation, an overall
higher level of cleanliness can be maintained without significant
downtime in boiler operation.
[0035] In the fill phase of the detonation cycle, air P and fuel F
are fed into the impulse cleaning device 22. As shown in FIG. 1 and
discussed above, pressurized air flow P is introduced into the
combustion chamber 80 through the air inlet ports 66 and fuel F
through the fuel inlet port 68. The fuel F and air flow P will mix
to form a fuel/air mixture suitable for combustion within the
impulse cleaning device 22. As more fuel and air are introduced and
mixed, the combustion chamber 80 will tend to fill with the
fuel/air mixture, starting near the closed head end 64 and
proceeding along the length of the combustion chamber 80 as more
fuel and air are introduced. Air flow P can be continuously fed to
the impulse cleaning device 22 through the air inlet ports 66
during cleaner operation.
[0036] It may be desirable to use the valve 104 to control the
introduction of fuel F into the impulse cleaning device 22 by means
of the controller 26. It may also be desirable to control the air
flow P for times when the cleaning system 20 is not operating.
According to one aspect of the invention, the controller 26 can
track the amount of time that has passed since the opening of a
fuel valve 104. Based upon the rate of air input to the impulse
cleaning device 22, the controller 26 can close the fuel valve 104
once a sufficient amount of fuel F has been added that the fuel/air
mixture has filled the desired portion of the combustion chamber
80. The controller 26 then provides activation or ignition energy
to the ignition device 120.
[0037] The ignition device 120 is controlled to initiate the
combustion of the fuel/air mixture within the combustion chamber
80. If, for example, a spark initiator is used as the ignition
device 120, the controller 26 sends electrical current to the spark
initiator to create a spark at a predetermined time. In general,
the ignition device 120 delivers sufficient energy into the mixture
near the ignition device to form an expanding combustion front C in
the fuel/air mixture. As this combustion front C consumes the fuel
by burning it with the oxidizer present in the mixture, the
combustion flame will propagate through the mixture within the
combustion chamber 80.
[0038] As the combustion front C propagates through the combustion
chamber 80 of the impulse cleaning device 22, the combustion front
will reach the walls of the body 60 and any obstacles that are
disposed within the combustion chamber. The interaction of the
combustion front C with the walls of the body 60 and the obstacles
will tend to generate an increase in pressure and temperature
within the combustion chamber 80. Such increased pressure and
temperature tend to increase the speed at which the combustion
front C propagates through the combustion chamber 80 and the rate
at which energy is released from the fuel/air mixture by the
combustion front. This acceleration continues until the combustion
speed raises above that expected from an ordinary deflagration
process in the deflagration zone a to a speed that characterizes a
quasi-detonation or detonation in the detonation zone b. This
deflagration to detonation process desirably takes place rapidly
(in order to sustain a high cyclic rate of operation), and so the
obstacles are used to decrease the run-up time and distance that is
required for each initiated flame to transition into a
detonation.
[0039] The detonation or supersonic shock wave D travels down the
length of the body 60 and out of the horn end 62 as cleaning energy
E. From the horn end 62, the cleaning energy E may be directed at
the object to be cleaned, such as the wall 40 and tubes 42. High
pressure combustion products follow the supersonic shock wave D and
flow through the horn end 62.
[0040] As the high-pressure products blow out of the impulse
cleaning device 22, the continued supply of air flow P through the
air inlet ports 66 will tend to push the combustion products
downstream and out of the horn end 62. Such continued supply of air
flow P is used to purge the combustion products from the body 60 of
the impulse cleaning device 22. Once the combustion products are
purged, the valve 104 for the fuel port 68 is opened, and a new
fill phase may be started to begin the next combustion cycle.
[0041] The impulse cleaning device 22 can be controlled by the
controller 26 to produce multiple supersonic shock waves D in rapid
succession. The supersonic shock wave D that exits from the horn
end 62 includes an abrupt pressure increase, as cleaning energy E,
that will impact the parts of the object to be cleaned such as the
wall 40 and tubes 42 of the boiler vessel. This cleaning energy E
has several beneficial effects by breaking up accumulated debris
and slag from the wall 40 and tubes 42 of the boiler vessel.
[0042] In one aspect, the cleaning energy E can produce pressure
waves that travel through the accumulated slag and debris. Such
pressure waves can produce flexing and compression within the
accumulations that can enhance crack formation within the debris
and break portions of the debris away from the rest of the
accumulation, or from the wall 40 and tubes 42 of the boiler
vessel. This is often seen as "dust" that is liberated from the
surface of the accumulated stag.
[0043] In addition, the pressure change associated with the passage
of the cleaning energy E can produce flex in the walls of the
boiler itself, which can also assist in separating the slag from
the wall 40 and tubes 42 of the boiler vessel. The repeated impacts
from the cleaning energy E of repeating combustion cycles may
excite resonances within the slag that can further enhance the
internal stresses experienced and promote the mechanical breakdown
of the debris. The repeated action of shock and purge is used to
erode build-up that accumulates upon the wall 40 and tubes 42 of
the boiler vessel.
[0044] It is important that the impulse cleaning system 20 be
properly operating during boiler operation. The impulse cleaning
device 22 may be located in an area that is either visually or
audibly inaccessible by an operator or attendant so that verifying
operation of the impulse cleaning device is not possible.
[0045] In one aspect of the invention the sensor 24 is mounted
externally to the impulse cleaning device 22 in order to provide
operational feedback to a control system or operator/attendant of a
cleaning system 20. The sensor 24 can detect if a detonation or
supersonic shock wave D occurred and can also provide information
that can be monitored to establish if any decline in performance or
loss of energy of the impulse cleaning device 22. This information
can be used to perform diagnostics on the impulse cleaning device
22, to provide feedback for an emergency cutoff circuit, or to
verify operation of the impulse cleaning device when it is located
remotely relative to an operator/attendant or otherwise not readily
accessible to a person.
[0046] The sensor 24 may be a strain gage, an accelerometer, an
acoustic detection device, a pressure gage and an ion probe.
According to one aspect of the invention as illustrated in FIG. 2,
a strain gage 140 is located outside the impulse cleaning device 22
to provide the feedback information or detect an event, such as the
occurrence of a detonation wave D in the impulse cleaning device.
By mounting the sensor 24 externally of the combustion chamber, the
hot and acidic gases from the combustion process do not contact the
sensor and cause early degradation of the sensor and prolong its
life.
[0047] The strain gage 140 of the sensor 24 is attached directly to
a bracket 82 that mounts the body 60 relative to the boiler vessel.
The stain gage 140 is oriented on the bracket so that it extends in
a direction substantially parallel to the longitudinal central axis
of the body 60. The strain gage 140 is electrically connected to
the controller 26. The strain gage 140 detects thrust forces in the
bracket that are indicative of a detonation event occurring in the
combustion chamber 80. The thrust forces are also indicative of the
displacement of the body 60 of the impulse cleaning device 22.
[0048] The strain gage 140 can be selected and calibrated to
provide an information signal to the controller 26 that a
detonation event has taken place and the intensity of the
supersonic shock wave D. The controller 26 can be programmed to
generate an alarm signal that activates an audible or visual signal
on alarm 142 in response to a predetermined period of time elapsing
before a detonation wave in the impulse cleaning device is detected
by the sensor 24. The lack of a combustion event when expected can
also trigger this alarm. The alarm signal can also be used to
signal an alarm on the master computer 128.
[0049] The sensor 24 can also generate a signal as a function of
the supersonic shock wave D in the impulse cleaning device 22, such
as intensity. The controller 26 can use this information to control
the delivery of fuel F to the combustion chamber 80, the delivery
of pressurized air flow P to the combustion chamber and/or the
delivery of ignition energy to the ignition device 120. Thus, the
controller 26 receives the signal generated by the sensor 24 to
control production of the supersonic shock wave D in response to
the signal. This allows automatic feedback to the controller 26 as
to whether impulse cleaning device 22 is operating correctly, or
not at all, or if there is any degradation/improvement in
performance. The sensor 24 and controller 26 provides accurate and
quick time response feedback to the operator/attendant as to what
the status of the impulse cleaning device 22 is and whether it is
operating properly without requiring periodic inspection of the
impulse cleaning device.
[0050] The sensor 24 may also be in the form of an accelerometer
that can be selected and calibrated to provide an information
signal to the controller 26 that a detonation event has taken place
and the intensity of the supersonic shock wave D. The accelerometer
sensor 24 would also be located outside the impulse cleaning device
22 to provide the feedback information or detect an event, such as
the occurrence of a detonation wave D in the impulse cleaning
device. By mounting the accelerometer sensor 24 externally of the
combustion chamber, the hot and acidic gases from the combustion
process do not contact the accelerometer sensor and cause early
degradation of the accelerometer sensor and prolong its life.
[0051] The accelerometer sensor 24 could be attached directly to
the bracket 82 or the body 60. The accelerometer sensor 24 would be
mounted so that one of its axes extends in a direction
substantially parallel to the longitudinal central axis of the body
60. The accelerometer sensor 24 would be electrically connected to
the controller 26. The accelerometer sensor 24 detects acceleration
of the component that it is attached to that is indicative of a
detonation event occurring in the combustion chamber 80.
[0052] The controller 26 can be programmed to generate an alarm
signal that activates an audible or visual signal on alarm 142 in
response to a predetermined period of time elapsing before a
supersonic shock wave D in the impulse cleaning device is detected
by the accelerometer sensor 24. The lack of a combustion event when
expected can also trigger this alarm. The alarm signal can also be
used to signal an alarm on the master computer 128.
[0053] In another aspect of the invention illustrated in FIGS. 3
and 4, the sensor 24 is a robust sensor arrangement mounted to the
impulse cleaning device 22. The sensor 24 can detect if a
detonation event or supersonic shock wave D occurred in the
combustion chamber 80 and can also provide information that can be
monitored to establish if any decline in performance or loss of
energy of the impulse cleaning device 22. This information can be
used to perform diagnostics on the impulse cleaning device 22, to
provide feedback for an emergency cutoff circuit, or to verify
operation of the impulse cleaning device when it is located
remotely relative to an operator/attendant or not readily
accessible to a person. By using a robust sensor 24 that can
withstand the hot and acidic gases from the combustion process,
degradation of the sensor is avoided and it can provide a
relatively long service life.
[0054] According to this aspect of the invention, the sensor 24
includes a pair of ion probes 160, as illustrated in FIGS. 3 and 4.
The ion probes 160 are mounted so that a portion of each ion probe
extends through the wall of the combustion chamber 80. The
controller 26 provides a voltage bias across a gap in a portion of
each of the ion probes 160 located in communication with the
combustion chamber 80. When a combustion event occurs, the ions
that are present in the gap of each ion probe 160 allow current to
flow. The current varies based on amount of ions present in each
gap.
[0055] Voltage across the gap of each ion probe 160 is monitored as
the output signal. A spike in voltage is detected as the combustion
event passes each ion probe 160. The ion probes 160 are located a
predetermined distance d apart along the detonation zone b of the
body 60. The velocity of the combustion wave front can be
calculated across this predetermined distance d. The velocity
determines if it is a combustion front C or supersonic shock wave
D. The ion probes 160, thus, detect an event, such as the
occurrence of a supersonic shock wave D in the impulse cleaning
device 22 and provide feedback information about the combustion
event in the combustion chamber 80.
[0056] The ion probes 160 can be selected and calibrated to provide
an information signal to the controller 26 that a detonation event
or supersonic shock wave D has passed the sensor 24 and the
intensity of the combustion event. The controller 26 can be
programmed to generate an alarm signal that activates an audible or
visual signal on alarm 162 in response to a predetermined period of
time elapsing before a supersonic shock wave D in the impulse
cleaning device 22 is detected by the sensor 24. The alarm signal
can also be used to signal an alarm on the master computer 128.
[0057] Another aspect of the invention concept uses a single ion
probe 160 located a known distance from the ignition device 120. A
spike in voltage is detected as the combustion event passes the ion
probe 160. The average velocity of the combustion event can be
calculated across this known distance. The average velocity
determines if it is a combustion front C or supersonic shock wave
D. The ion probe 160, thus, detects an event, such as the
occurrence of a supersonic shock wave D in the impulse cleaning
device 22 and provides feedback information about the combustion
event in the combustion chamber 80.
[0058] The sensor 24 may be used to detect any or all of the
following: the occurrence of a detonation or supersonic shock wave
event; the intensity level (such as soft through loud); and the
frequency content of the event (such as thud through ping). The
signal information from the sensor 24 may be monitored or processed
for multiple uses integral to aspects of the invention. Such uses
include, but are not limited to, confirming that a detonation
occurred; identifying a change in performance or loss of energy of
the impulse cleaning device 22; providing feedback to the system 20
which enables adjustment of detonation parameters (such as:
fuel/air ratios, fuel flow, air flow, charge/spark setup, and/or
fill times) for optimal performance; facilitating diagnostics on
the impulse cleaning device 22; providing feedback for an emergency
cutoff circuit; or verifying operation of the impulse cleaning
device when it is located remotely relative to an
operator/attendant or otherwise not readily accessible to a
person.
[0059] The output of sensor 24 may be sent directly, without
anti-alias filtering, to an analog-to-digital converter for
multiple uses, such as: detecting the occurrence of the event;
providing minimal delay to identify the start of detonation;
determining the intensity level of the event; and to a lesser
degree, frequency content of the event. The output of the sensor 24
may be conditioned (filtered, amplified, etc.). The signal can have
for multiple uses, such as: detecting the occurrence of the
detonation event; providing identification of the start of
detonation; determining the intensity level of the event; frequency
content of the event, and detection of out-of-band frequency
input.
[0060] Conditioning of the signal of the sensor 24 can be done in
analog and/or digital form. The desired frequency band(s) and
amplitude of the signal can then be processed for making
operational decisions on the detonation parameters and/or
notifications to the operator that may be needed. The signal
conditioning provides a means to preserve signal to noise ratio in
high-noise applications and/or to prepare the signal of the sensor
24 for use with following stages or process steps. Conditioning the
signal by scaling and band-limiting for anti-aliasing purposes when
interfacing to analog-to-digital converters (ADC) is one example.
Another example is to filter (high, low or band) the signal to
remove non-desired frequency content, improving the ability of the
controller 26 to make operation decisions and/or notifications.
[0061] In one aspect of the invention, when high ambient noise
exists, the use of a sensor 24 with an integrated gain stage
(localized near the sensor) allows the signal to be sent to a
remote location away from the impulse cleaning device 22 while
preserving the signal to noise ratio. The sensor 24 may or may not
require this feature, depending on the particular application and
setup.
[0062] Using the signal of the sensor 24, one or multiple
thresholds may be set to signify a particular event has occurred.
For example, a low threshold may identify that "no detonation has
occurred", a mid-level threshold may identify that "a weakened
detonation has occurred", and third high-level threshold may
identify that "a good detonation has occurred". The use of at least
one threshold is required to enable proper operation of the impulse
cleaning device 22, while the other thresholds may provide
additional capability of the impulse cleaning device that is useful
to the operation of the impulse cleaning device. The use of
"intensity level" threshold(s) can involve the use of an ADC and
logic/processor device or simply an analog comparator.
[0063] "Windowing" the event in time with a start point and an end
point, using the scheduled start determined by the controller 26,
allows a counter to be used with a threshold circuit to enhance
proper detection of a detonation event, as opposed to spurious
noise. For example, a signal may need two out of five samples, or
fifty out of a hundred samples, to be called a "good detonation".
The actual percentage of samples can be adjusted above or below the
examples noted for a particular application and sensor
configuration. Noisy environments may require a higher count to be
achieved before declaring a "good detonation". A higher capability
signal processing device may use more samples to further extend
operation into a noisy environment or provide better resolution
information on the detonation event. Measuring the duration of the
signal of the sensor 24 that meets a particular threshold or total
count from a start point is another "windowing" implementation.
Each of these windowing applications, and in combination, allow the
controller 26 to provide detonation parameter modification and
operator notification when necessary.
[0064] Selection of a particular frequency response of the signal
of sensor 24 can indicate a "good detonation". A high frequency
"ping" may indicate a non-optimal detonation in which the fuel/air
ratio or flow, charge/spark, and/or fill time may be adjusted to
improve performance. For example, a detonation with relatively high
frequency content may cause the impulse cleaning system 20 to
increase the fill time. Conversely, a low frequency response may
also indicate a non-optimal detonation, but cause the system to
decrease the fill time. Fill time is but one example. Adjustment of
the other detonation parameters can be made using the same
frequency response information.
[0065] Characterization of a particular installation or setup using
intensity and/or frequency response detected by the sensor 24
enables enhanced operation of the impulse cleaning device 22. For
example, if a frequency response exists with relatively clean
(minimal spurious and out-of-band) content and then later during
operation, the signal begins to contain spurious or out-of-band
signals, the system can flag a warning to the operator of a problem
at that installation site. Thresholds or upper or lower frequency
limits enable "good detonation" decisions to be made by the system.
For example, an installation may have detonations that produce
"main" frequencies from 15 Hz to 250 Hz and ones from 2 kHz to 4
kHz. These can be stored and/or analyzed for any shift in or
absence of content allowing the system to adjust the detonation
parameters to restore "good detonation" operation. The "main"
frequencies used to make the determination may be multiple bands,
single bands, or simply a single frequency.
[0066] An order of "modifying decisions" may be designed such that:
adjustment of the fill time to a particular point, then fuel/air
ratio may be adjusted to a prescribed limit, then total flow of
fuel or air may be modified. The system 20 can then optimize
performance without outside intervention, and if necessary, notify
an operator that maintenance will be needed. The above is but one
example. Adjustment of the other detonation parameters in various
orders can be made for a particular installation or system setup
along with notifications when particular thresholds or limits are
reached. Thresholds set and/or trending data collected on signal
content can allow health and maintenance prediction for
installations, reducing the need for scheduled maintenance which
could be unnecessary.
[0067] To provide a check on the condition of the sensor 24, during
a period before or after a detonation event, a sensor "quiescent"
value can be tested. If it exceeds a threshold, a decision can be
made that the environment is "too noisy" or the sensor 24 is
faulty, enabling a maintenance notification to be sent to an
operator and/or a system protection function to be activated (such
as disabling operation of the cleaning device, fuel valves, spark,
etc.).
[0068] It will be appreciated that such an impulse cleaning system
20 is not limited to industrial boilers, but may be used to provide
cleaning on a variety of different surfaces which may experience
fouling or accumulation of debris. Examples of vessels having
surfaces which may be cleaned using the systems and techniques
described herein include but are not limited to: vessels used in
cement production, waste-to-energy plants, and coal-fired energy
facilities, as well as reactors in coal gasification plants.
[0069] The various embodiments of cleaning systems described above
thus provide a way to achieve soot or ash removal from the wall 40
and tubes 42 of the boiler vessel. These techniques and systems
also allow for periodic operation without the need to shut down the
device being cleaned for extended periods of time.
[0070] Although the systems herein have been disclosed in the
context of certain preferred embodiments and examples, it will be
understood by those skilled in the art that the invention extends
beyond the specifically disclosed embodiments to other alternative
embodiments and/or uses of the systems and techniques herein and
obvious modifications and equivalents thereof. Thus, it is intended
that the scope of the invention disclosed should not be limited by
the particular disclosed embodiments described above, but should be
determined only by a fair reading of the claims that follow.
* * * * *