U.S. patent application number 11/740413 was filed with the patent office on 2008-10-30 for control of detonative cleaning apparatus.
This patent application is currently assigned to UNITED TECHNOLOGIES CORPORATION. Invention is credited to Raymond N. Henderson, Donald W. Kendrick, Erik G. Liljegren, Kirk R. Lupkes, Mark W. Parish.
Application Number | 20080264357 11/740413 |
Document ID | / |
Family ID | 39596450 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080264357 |
Kind Code |
A1 |
Liljegren; Erik G. ; et
al. |
October 30, 2008 |
CONTROL OF DETONATIVE CLEANING APPARATUS
Abstract
An apparatus is provided for cleaning one or more surfaces
within a vessel having a vessel wall separating a vessel exterior
from a vessel interior and having a wall aperture. The apparatus
has at least one elongate conduit having an upstream first end and
a downstream second end and positioned to direct a shockwave from
the second end into the vessel interior. A source of fuel and
oxidizer is coupled to the conduit to deliver the fuel and oxidizer
to the conduit An initiator is positioned to initiate a reaction of
the fuel and oxidizer to produce the shockwave. At least one sensor
coupled to the conduit to detect motion indicative of a detonation.
A control system coupled to the initiator, the source, and the
sensor for receiving input from the sensor and controlling
operation of the initiator and source responsive to said input.
Inventors: |
Liljegren; Erik G.;
(Issaquah, WA) ; Parish; Mark W.; (Des Moines,
WA) ; Henderson; Raymond N.; (Renton, WA) ;
Kendrick; Donald W.; (Bellevue, WA) ; Lupkes; Kirk
R.; (Renton, WA) |
Correspondence
Address: |
BACHMAN & LAPOINTE, P.C. (P&W)
900 CHAPEL STREET, SUITE 1201
NEW HAVEN
CT
06510-2802
US
|
Assignee: |
UNITED TECHNOLOGIES
CORPORATION
Hartford
CT
|
Family ID: |
39596450 |
Appl. No.: |
11/740413 |
Filed: |
April 26, 2007 |
Current U.S.
Class: |
122/379 |
Current CPC
Class: |
B08B 7/0007
20130101 |
Class at
Publication: |
122/379 |
International
Class: |
F22B 37/48 20060101
F22B037/48 |
Claims
1. An apparatus for cleaning one or more surfaces within a vessel
having a vessel wall separating a vessel exterior from a vessel
interior and having a wall aperture, the apparatus comprising: at
least one elongate conduit having an upstream first end and a
downstream second end and positioned to direct a shockwave from the
second end into the vessel interior; and a source of fuel and
oxidizer coupled to the conduit to deliver the fuel and oxidizer to
the conduit; an initiator positioned to initiate a reaction of the
fuel and oxidizer to produce the shockwave; at least one sensor
coupled to the conduit to detect motion indicative of a detonation;
and a control system coupled to the initiator, the source, and the
sensor for receiving input from the sensor and controlling
operation of the initiator and source responsive to said input.
2. The apparatus of claim 1 wherein: the sensor is a piezoelectric
sensor.
3. The apparatus of claim 1 wherein: the sensor is a contact
accelerometer.
4. The apparatus of claim 1 wherein: the sensor is a contact
vibration sensor.
5. The apparatus of claim 1 wherein: the sensor is in contact with
an exterior of the conduit without an associated aperture to the
interior of the conduit.
6. The apparatus of claim 1 wherein: there are a plurality of such
conduits and such initiators, each of the conduits associated with
an associated one or more of the initiators; and the sensors are
series coupled to the control system.
7. The apparatus of claim 6 wherein: the control system is
programmed to generate maintenance or service requests responsive
to the input.
8. The apparatus of claim 6 wherein: the control system is
programmed to determine detonation failures of the conduits
individually.
9. The apparatus of claim 8 wherein: the control system is
programmed to individually adjust operational parameters of the
conduits responsive to the determined failures.
10. The apparatus of claim 1 wherein: the control system
communicates with a remote monitoring system.
11. The apparatus of claim 1 wherein: the control system is
programmed to determine a detonation success or failure status.
12. The apparatus of claim 1 wherein: the control system is
programmed with a plurality of different cleaning processes and to
execute the processes responsive to corresponding sensed
conditions.
13. A method for cleaning a surface within a vessel, the method
comprising: introducing fuel and oxidizer to at least one elongate
conduit having an upstream first end and a downstream second end
and positioned to direct a shockwave from the second end into the
vessel interior; initiating a reaction of the fuel and oxidizer;
detecting a motion of the conduit; responsive to the detecting,
determining a characteristic of the reaction; and responsive to the
determined characteristic, adjusting at least one parameter of the
introducing and initiating so as to provide feedback control of the
characteristic.
14. The method of claim 13 wherein: the detecting comprises
detecting an acceleration.
15. The method of claim 13 wherein: the detecting comprises
detecting a vibration parameter.
16. The method of claim 13 wherein: the determining comprises
determining a sufficiency of a detonation.
17. The method of claim 13 further comprising: responsive to the
determined characteristic, generating an automated maintenance or
service request.
18. An apparatus for cleaning one or more surfaces within a vessel
having a vessel wall separating a vessel exterior from a vessel
interior and having a wall aperture, the apparatus comprising: at
least one elongate conduit having an upstream first end and a
downstream second end and positioned to direct a shockwave from the
second end into the vessel interior; and a source of fuel and
oxidizer coupled to the conduit to deliver the fuel and oxidizer to
the conduit; an initiator positioned to initiate a reaction of the
fuel and oxidizer to produce the shockwave; a pressure switch
coupled to the conduit to be exposed to pressure associated with
the reaction; and a control system coupled to the initiator, the
source, and the pressure switch for receiving input from the
pressure switch and controlling operation of the initiator and
source responsive to said input.
19. The apparatus of claim 18 wherein the pressure switch is a
binary switch, with an open condition associated with pressure
below a threshold and a closed condition associated with pressure
above the threshold.
20. The apparatus of claim 18 wherein the pressure switch is along
an upstream half of a length of the conduit.
Description
BACKGROUND
[0001] The disclosure relates to industrial equipment. More
particularly, the disclosure relates to the detonative cleaning of
industrial equipment.
[0002] Surface fouling is a major problem in industrial equipment.
Such equipment includes furnaces (coal, oil, waste, etc.), boilers,
gasifiers, reactors, heat exchangers, and the like. Typically the
equipment involves a vessel containing internal heat transfer
surfaces that are subjected to fouling by accumulating particulate
such as soot, ash, and minerals, more integrated buildup such as
slag and/or fouling, and the like. Such particulate build-up may
progressively interfere with plant operation, reducing efficiency
and throughput and potentially causing damage. Cleaning of the
equipment is therefore highly desirable and is attended by a number
of relevant considerations. Often direct access to the fouled
surfaces is difficult. Additionally, to maintain revenue it is
desirable to minimize downtime associated with cleaning. A variety
of technologies have been proposed.
[0003] An exemplary detonative cleaning apparatus includes a
conduit into which fuel and oxidizer are introduces and then
ignited. The ignition causes a shock wave to be discharged from the
conduit to impact the surfaces to be cleaned. By way of example,
U.S. patent application publication 20050199743, the disclosure of
which is incorporated herein by reference in its entirety as if set
forth at length, discloses a detonative cleaning apparatus control
system and has a specific illustration relative to a segmented
conduit assembly. Alternative apparatus are of the retractable
lance-type. Such systems are often identified as "soot blowers"
after the key application for the technology.
SUMMARY
[0004] One aspect of the disclosure involves an apparatus for
cleaning one or more surfaces within a vessel having a vessel wall
separating a vessel exterior from a vessel interior and having a
wall aperture. The apparatus has at least one elongate conduit
having an upstream first end and a downstream second end and
positioned to direct a shockwave from the second end into the
vessel interior. A source of fuel and oxidizer is coupled to the
conduit to deliver the fuel and oxidizer to the conduit An
initiator is positioned to initiate a reaction of the fuel and
oxidizer to produce the shockwave. At least one sensor coupled to
the conduit to detect motion characteristic of a detonation. A
control system coupled to the initiator, the source, and the sensor
for receiving input from the sensor and controlling operation of
the initiator and source responsive to said input.
[0005] The details of one or more embodiments of are set forth in
the accompanying drawings and the description below. Other
features, objects, and advantages will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a view of an industrial furnace associated with
several soot blowers positioned to clean a level of the
furnace.
[0007] FIG. 2 is a side view of one of the blowers of FIG. 1.
[0008] FIG. 3 is a schematic view of a control system for multiple
cleaning apparatus.
[0009] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0010] FIG. 1 shows a furnace 20 having an exemplary three
associated soot blowers 22. In the illustrated embodiment, the
furnace vessel is formed as a right parallelepiped and the soot
blowers are all associated with a single common wall 24 of the
vessel and are positioned at like height along the wall. Other
configurations are possible (e.g., a single soot blower, one or
more soot blowers on each of multiple levels, and the like).
[0011] Each soot blower 22 includes an elongate combustion conduit
26 extending from an upstream (e.g., distal/inlet) end 28 away from
the furnace wall 24 to a downstream (e.g., proximal/outlet) end 30
closely associated with the wall 24. Optionally, however, the end
30 may be well within the furnace. In operation of each soot
blower, combustion of a fuel/oxidizer mixture within the conduit 26
is initiated proximate the upstream end (e.g., within an
upstreammost 10% of a conduit length) to produce a detonation wave.
The detonation wave is expelled from the downstream end as a
shockwave along with associated combustion gases for cleaning
surfaces within the interior volume of the furnace.
[0012] Each soot blower may be associated with a fuel/oxidizer
source 32. Such source or one or more components thereof may be
shared amongst the various soot blowers. An exemplary source
includes a liquified or compressed gaseous fuel cylinder 34 and an
oxygen cylinder 36 in respective containment structures 38 and 40.
In the exemplary embodiment, the oxidizer is a first oxidizer such
as essentially pure oxygen. A second oxidizer may be in the form of
shop air delivered from a central air source 42. In the exemplary
embodiment, air is stored in an air accumulator 44. Fuel, expanded
from that in the cylinder 34 is generally stored in a fuel
accumulator 46. Each exemplary source 32 is coupled to the
associated conduit 26 by appropriate plumbing below. Similarly,
each soot blower includes a spark box 50 for initiating combustion
of the fuel oxidizer mixture and which, along with the source 32,
is controlled by a control and monitoring system (discussed
below).
[0013] FIG. 2 shows further details of an exemplary soot blower 22.
The exemplary detonation conduit 26 is formed with a main body
portion formed by a series of doubly flanged conduit sections or
segments 60 arrayed from upstream to downstream and a downstream
nozzle conduit section or segment 62 having a downstream portion 64
extending through an aperture 66 in the wall and ending in the
downstream end or outlet 30 exposed to the furnace interior 68. The
term nozzle is used broadly and does not require the presence of
any aerodynamic contraction, expansion, or combination thereof.
Exemplary conduit segment material is metallic (e.g., stainless
steel). The outlet 30 may be located further within the furnace if
appropriate support and cooling are provided. FIG. 2 further shows
furnace interior tube bundles 70, the exterior surfaces of which
are subject to fouling.
[0014] An overall length L between ends 28 and 30 may be 1-15 m,
more narrowly, 5-15 m. A fuel/oxidizer charge may be introduced to
the detonation conduit interior in a variety of ways. There may be
one or more distinct fuel/oxidizer mixtures. Such mixture(s) may be
premixed external to the detonation conduit, or may be mixed at or
subsequent to introduction to the conduit. FIG. 2 shows conduit
configured for distinct introduction of two distinct fuel/oxidizer
combinations: a predetonator combination; and a main combination.
In the exemplary embodiment, at an upstream first location, one or
more predetonator fuel injection conduits 90 are coupled to one or
more ports 92 in the conduit to define fuel injection ports.
Similarly, one or more predetonator oxidizer conduits 94 may be
coupled to oxidizer inlet ports 96. A purge gas conduit 98 may be
similarly connected to a purge gas port 100 yet further upstream.,
An igniter/initiator 106 (e.g., a spark plug) may be located near
the upstream end of the combustion conduit.
[0015] In the exemplary embodiment, a main fuel is carried by a
number of main fuel conduits 112 and a main oxidizer is carried by
one or more main oxidizer conduits 110. In exemplary embodiments,
the fuels are hydrocarbons. In particular exemplary embodiments,
both fuels are the same, drawn from a single fuel source but mixed
with distinct oxidizers: essentially pure oxygen for the
predetonator mixture; and air for the main mixture. Exemplary fuels
useful in such a situation are propane, MAPP gas, or mixtures
thereof. Other fuels are possible, including ethylene and liquid
fuels (e.g., diesel, kerosene, and jet aviation fuels). The
oxidizers can include mixtures such as air/oxygen mixtures of
appropriate ratios to achieve desired main and/or predetonator
charge chemistries. Further, monopropellant fuels having
molecularly combined fuel and oxidizer components may be
options.
[0016] In operation, at the beginning of a use cycle, the
combustion conduit is initially empty except for the presence of
air (or other purge gas). The predetonator fuel and oxidizer are
then introduced through the associated ports to fill an upstream
section (e.g., just beyond the main fuel/oxidizer ports). The
predetonator fuel and oxidizer flows may then be shut off. An
exemplary volume filled the predetonator fuel and oxidizer is
1-40%, more narrowly 1-20%, of the combustion conduit volume. The
main fuel and oxidizer are then introduced, to substantially fill
some fraction (e.g., 20-100%) of the remaining volume of the
combustor conduit. The main fuel and oxidizer flows are then shut
off. The prior introduction of predetonator fuel and oxidizer past
the main fuel/oxidizer ports largely eliminates the risk of the
formation of an air or other non-combustible slug between the
predetonator and main charges. Such a slug could prevent migration
of the combustion front between the two charges.
[0017] With the charges introduced, the spark box is triggered to
provide a spark discharge of the initiator igniting the
predetonator charge. The predetonator charge being selected for
very fast combustion chemistry, the initial deflagration quickly
transitions to a detonation within the segment 84 and producing a
detonation wave. Once such a detonation wave occurs, it is
effective to pass through the main charge which might, otherwise,
have sufficiently slow chemistry to not detonate within the conduit
of its own accord. The wave passes longitudinally downstream and
emerges from the downstream end 30 as a shockwave within the
furnace interior, impinging upon the surfaces to be cleaned and
thermally and mechanically shocking to typically at least loosen
the contamination. The wave will be followed by the expulsion of
pressurized combustion products from the detonation conduit, the
expelled products emerging as a jet from the downstream end 30 and
further completing the cleaning process (e.g., removing the
loosened material). After or overlapping such venting of combustion
products, a purge gas (e.g., air from the same source providing the
main oxidizer and/or nitrogen) is introduced through the purge port
100 to drive the final combustion products out and leave the
detonation conduit filled with purge gas ready to repeat the cycle
(either immediately or at a subsequent regular interval or at a
subsequent irregular interval (which may be manually or
automatically determined by the control and monitoring system)).
Optionally, a baseline flow of the purge gas may be maintained
between charge/discharge cycles so as to prevent gas and
particulate from the furnace interior from infiltrating upstream
and to assist in cooling of the detonation conduit.
[0018] The apparatus may be used in a wide variety of applications.
By way of example, just within a typical coal-fired furnace, the
apparatus may be applied to: the pendants or secondary
superheaters, the convective pass (primary superheaters and the
economizer bundles); air preheaters; selective catalyst removers
(SCR) scrubbers; the baghouse or electrostatic precipitator;
economizer hoppers; ash or other heat/accumulations whether on heat
transfer surfaces or elsewhere, and the like. Similar possibilities
exist within other applications including oil-fired furnaces, black
liquor recovery boilers, biomass boilers, waste reclamation burners
(trash burners), and the like.
[0019] A variety of systems may be provided for monitoring and/or
controlling operation of the detonative cleaning apparatus. The
implementation of any particular control and monitoring system may
be influenced by the physical environment including the nature and
configuration of the vessel and its surfaces and the arrangement of
the combustion conduit(s). FIG. 3 schematically shows one of a
number of levels of a vessel 200. At this level, a number of
combustion conduits 202A-D are positioned. In the exemplary
embodiment, downstream outlets of the conduits are positioned in
the interior of the vessel and upstream ends are external to the
vessel. Although shown straight, the conduits may have non-straight
configurations to discharge shockwaves in desired locations with
desired directions. Each conduit is closely associated with an
interface module 204A-D which may provide local control of various
operational parameters (e.g., including fuel and oxidizer
introduction, purge and cooling gas introduction, initiation, and
the like). Further details of an exemplary interface module are
discussed below. The given vessel level may also include sensors
206, 207, and 208. However, the sensors need not be level-specific.
Similarly, the conduits could be other than level-specific and
other than oriented to discharge in parallel planes. The sensors
may be conduit-specific (e.g., close to the outlet of a specific
associated conduit or to the furnace surface cleaned by such
conduit) or may be more generally located. The sensors may detect
one or more of thermal conditions, pressures, flows, chemical
conditions, and/or visual conditions. Exemplary sensor operation is
discussed in further detail below.
[0020] For signal communication, the modules and sensors are
coupled via communication lines 209 to a hub (e.g., ethernet) 210.
In the exemplary embodiment, the sensors are coupled to the hub via
the modules (e.g., coupled to the modules by communication or
signal lines). For physical input (e.g., fuel, oxidizer, purge gas,
coolant, power, and the like), the modules are coupled to a central
supply unit 212 via fluid and power lines 213. The hub and supply
unit may be level-specific, common, or some combination. The hub is
coupled for signal communication (e.g., via network lines 215 such
as a fiber optic line, Ethernet line, or the like) to a control and
monitoring system 214 of the facility (e.g., a general purpose
computer running control/monitoring software) which may be specific
to the vessel or central to a group of vessels at a site (e.g., a
given facility). The supply unit may similarly be coupled to the
system 214 via the hub 210 or may exist independently. The system
214 is in communication with a remote control and monitoring system
216. The system 216 may be in secure communication with a number of
systems 214 at a number of different sites. In such a situation,
however, the system 216 may be colocated with one or more of those
systems 214 and off-site of the others. The exemplary communication
between the system 216 and systems 214 is via a wide area network
217 such as the internet. Alternative public and private networks
or other communication systems may be used. The supply unit 212
may, itself, be fed from a remotely located tank farm 218 (e.g., a
central tank farm of the facility) via lines 219 for supply of
non-air gases and other fluids and from appropriate shop air and
power sources (not shown) which may also be central sources of the
facility). The system 214 may communicate with several central
systems. For example, the system 216 may be a central system of a
facility owner/operator communicating with systems 214 at various
facilities of that owner/operator. A central system 223 may be a
central system of a service vendor communicating with systems 214
of various facilities of various owners/operators either directly
or via the systems 216. Based ultimately upon data provided by the
sensors 206 and 208, the systems 214 may inform the system 223 that
service or routine maintenance is necessary or otherwise
appropriate (the decision being made at any of the systems 214,
216, or 223).
[0021] In the exemplary embodiment, an emergency control panel 220
is in close proximity to the system 214. The exemplary emergency
control panel includes one or more status lights and one or more
switches (e.g., red/green status lights and emergency kill switches
for each conduit plus a master kill switch for all conduits). These
are coupled by lines 222 extending to the individual interface
modules. In the event of a control system failure which might
prevent control (namely safing) of the conduits via the system 214
and hub 210, the kill switches may be tripped by a technician to
safe the conduits (e.g., shut the fuel and oxidizer valves, disable
the ignition, and the like, to safely shut down and/or disable the
associated conduits). The interface modules themselves may be set
up in a failsafe mode whereby a break in the associated line(s) 215
or 222 causes a module to transition to a safe mode.
[0022] The sensors 206 and/or 207 may also represent motion sensors
used to sense conduit motion responsive to the combustive event. In
particular, the sensors may be used to verify detonation,
generally, and the magnitude/sufficiency of the detonation, in
particular. An exemplary motion sensor is an accelerometer. An
exemplary accelerometer is a piezoelectric sensor such as a ceramic
shear accelerometer. Another exemplary sensor is a vibration
sensor. An exemplary vibration sensor is a mercury-free mechanical
vibration switch. Another exemplary sensor is a strain gauge. Such
sensors do not need direct exposure to the conduit interior or
vessel interior (although the microphone in particular may also be
amenable to interior exposure for more direct measurement). Such
sensors may be mounted on the conduit exterior without an
associated aperture to the conduit interior. This can save
complexity, sensor robustness, etc. Advantageous sensor positioning
may be outside the vessel to limit sensor exposure to severe
environments.
[0023] Exemplary sensor coupling is a series coupling of the
sensors (or back end signal processing circuit) for a plurality
(e.g., all) of the conduits. The series circuit may be normally
closed. In the event of a detonation on any conduit, the sensor
will toggle and the circuit will open. The signal processing
circuit may be configured to hold the open circuit open long enough
(e.g., greater than a second) for the controller to read. At this
point, if a particular conduit was commanded to fire and the
circuit doesn't open, the controller knows which conduit failed to
detonate. After a pre-defined number of failures of a given conduit
to successfully fire, the control system may alert the operator and
takes that particular conduit offline (e.g., while allowing for
continued operation of the remaining conduits).
[0024] Another option for the sensors 206 and/or 207 is a pressure
switch (as distinguished from a continuous pressure sensor). The
switch threshold may be selected in view of its positioning to
correspond to a desired threshold for the pressure associated with
detonation. Triggering of the switch would thus indicate a
successful detonation, while a failure to trigger would indicate an
unsucccessful or sub-threshold event. An exemplary positioning is
in an upstream half of a length of the conduit.
[0025] Such sensing of the detonation (or lack thereof) may be
combined with further control aspects and inputs such as are
identified in the above-mentioned U.S. patent application
publication 20050199743.
[0026] One or more embodiments have been described. Nevertheless,
it will be understood that various modifications may be made. For
example, the invention may be adapted for use with a variety of
industrial equipment and with variety of soot blower technologies.
For example, the principles may be adapted to various existing or
yet-developed detonative cleaning apparatus, including fixed and
extensible/retractable units. Aspects of the existing equipment and
technologies may influence aspects of any particular
implementation. Accordingly, other embodiments are within the scope
of the following claims.
* * * * *