U.S. patent application number 11/753801 was filed with the patent office on 2008-11-27 for pulse detonation cleaning apparatus.
This patent application is currently assigned to UNITED TECHNOLOGIES CORPORATION. Invention is credited to Thomas R.A. Bussing, John P. Harty, James R. Hochstein, JR., David E. Steele.
Application Number | 20080292998 11/753801 |
Document ID | / |
Family ID | 39731616 |
Filed Date | 2008-11-27 |
United States Patent
Application |
20080292998 |
Kind Code |
A1 |
Hochstein, JR.; James R. ;
et al. |
November 27, 2008 |
PULSE DETONATION CLEANING APPARATUS
Abstract
The burning of fuel (e.g., coal) in industrial equipment
generates an exhaust flow containing airborne particulate. The flow
is passed through a rotary heat exchanger to preheat inlet air. The
heat exchanger element is subject to fouling and is cleaned by a
pulsed combustion device. The device is operated by introducing a
fuel and oxidizer charge to at least one conduit and initiating
combustion of the charge. The combustion generates a shock wave to
which the element is exposed, dislodging and/or otherwise removing
the deposits.
Inventors: |
Hochstein, JR.; James R.;
(Seattle, WA) ; Steele; David E.; (Seattle,
WA) ; Bussing; Thomas R.A.; (Sammamish, WA) ;
Harty; John P.; (Bellevue, WA) |
Correspondence
Address: |
MCCORMICK, PAULDING & HUBER LLP
CITY PLACE II, 185 ASYLUM STREET
HARTFORD
CT
06103
US
|
Assignee: |
UNITED TECHNOLOGIES
CORPORATION
Hartford
CT
|
Family ID: |
39731616 |
Appl. No.: |
11/753801 |
Filed: |
May 25, 2007 |
Current U.S.
Class: |
431/1 ;
431/3 |
Current CPC
Class: |
F28G 7/00 20130101; F28G
7/005 20130101 |
Class at
Publication: |
431/1 ;
431/3 |
International
Class: |
F23C 15/00 20060101
F23C015/00; F23J 99/00 20060101 F23J099/00 |
Claims
1. An apparatus comprising: a combustor; an inlet air flowpath
extending to the combustor; an exhaust flowpath extending from the
combustor; a rotary heat exchanger along the inlet air flowpath and
exhaust flowpath; and a pulsed-combustion device positioned to
direct a shock wave toward a core of the heat exchanger and
comprising: a source of fuel and oxidizer; at least one combustion
conduit coupled to the source to receive charges of said fuel and
oxidizer; and at least one ignitor coupled to the combustion
conduit to ignite the charges.
2. The apparatus of claim 1 wherein: the combustor is a
coal-burning furnace.
3. The apparatus of claim 1 wherein: the pulsed combustion device
comprises first and second said conduits, the first conduit having
an outlet upstream of the core along the exhaust flowpath and the
second conduit having an outlet downstream of the core along the
exhaust flowpath.
4. The apparatus of claim 3 wherein: the first and second conduits
each have a plurality of outlets at different radial positions
relative to an axis of rotation of the core.
5. The apparatus of claim 4 wherein: the first and second conduits
have a decreasing cross-sectional area within the exhaust flowpath;
and the plurality of outlets are along respective portions of
different cross-sectional area.
6. The apparatus of claim 1 wherein: said combustion conduits have
outlets aimed transverse to a downstream direction of the
flowpath.
7. The apparatus of claim 1 wherein: at least four of said
combustion conduits are positioned at essentially a common
streamwise location along the exhaust flowpath.
8. The apparatus of claim 1 further comprising: a smokestack
forming an outlet of the exhaust flowpath to atmosphere.
9. The apparatus of claim 1 wherein the source comprises: a first
source of said fuel, said fuel consisting in majority part, by
mass, of fuel selected from the group consisting of hydrogen,
hydrocarbon fuels, and their mixtures; and a second source of said
oxidizer, said oxidizer consisting essentially of oxygen.
10. The apparatus of claim 1 wherein: said combustion conduits have
lengths of 0.5-4 m and cross-sectional areas of 20-730
cm.sup.2.
11. The apparatus of claim 1 further comprising: a controller
configured to fire the device a plurality of times to provide
circumferential coverage of the core.
12. The apparatus of claim 11 wherein: the controller configured to
synchronize firing of the device relative to rotation of the
core.
13. An apparatus comprising: a combustor; an exhaust flowpath
extending from the combustor; an inlet air flowpath extending to
the combustor; a rotary heat exchanger along the inlet air flowpath
and exhaust flowpath; and pulsed-combustion means for cleaning a
core of the rotary heat exchanger.
14. The apparatus of claim 13 wherein the combustor is a fossil
fuel-burning furnace;
15. The apparatus of claim 13 being a boiler system
16. A method for operating a plant comprising: burning a plant fuel
and generating a flow containing particles; passing the flow
through a heat exchanger to heat an inlet air flow; and cleaning a
core of the heat exchanger by a pulsed detonation process
including: introducing a fuel and oxidizer charge to at least one
conduit; initiating combustion of the charge; and exposing the core
to shock waves generated by combustion.
17. The method of claim 16 wherein: the passing of the flow
comprises an axial flow through the core while the core rotates
about a core axis.
18. The method of claim 16 wherein: the plant fuel is selected from
the group consisting of coal, fuel oil, hydrocarbon gas biomass,
trash, and combinations thereof.
19. The method of claim 16 wherein: the cleaning comprises exposing
said core to said shock waves from a plurality of said
conduits.
20. The method of claim 16 wherein: the cleaning comprises exposing
the core to shock waves from opposed outlets of one or more pairs
of said conduits.
21. The method of claim 16 wherein: the charge comprises hydrogen
as a by weight majority of the fuel.
22. The method of claim 16 wherein: the at least one conduit is
operated with an air purge before each charge introduction.
23. The method of claim 16 wherein: the cleaning is initiated
responsive to a sensed condition of the core.
24. The method of claim 16 wherein: the conduit is fired a
plurality of times in synchronization with rotation of the core so
as to provide a full circumferential cleaning of the core.
Description
BACKGROUND
[0001] The disclosure relates to coal-fired industrial equipment.
More particularly, the disclosure relates to the cleaning of from
coal-fired industrial equipment such as pulverized coal-fired
utility boilers.
[0002] One feature of many pieces of such equipment is the use of a
rotary heat exchanger to pre-heat inlet air by transferring heat
from the exhaust flow. Exemplary rotary heat exchangers are found
in U.S. Pat. Nos. 4,487,252 and 5,950,707. In an exemplary axial
rotary heat exchanger, the exhaust and inlet flows pass along
respective angular sectors of the heat exchanger. The flows pass
through a rotating core of the heat exchanger. The core has plates
or other features that absorb heat when in the exhaust flowpath and
then lose that heat while passing through the inlet air flow. Steam
or air purges may be used to clean the core plates.
[0003] Within equipment such as boilers, sootblowers have been used
to clean surfaces such as boiler tubes. Steam lance sootblowers
have mainly been used. Detonative or pulsed combustion sootblowers
have recently been proposed. An example of such a sootblower is in
U.S. Pat. No. 7,011,047.
SUMMARY
[0004] The burning of fuel (e.g., coal) in industrial equipment
generates an exhaust flow containing airborne particulate. The flow
is passed through a rotary heat exchanger to preheat inlet air. The
heat exchanger element is subject to fouling and is cleaned by a
pulsed combustion device. The device is operated by introducing a
fuel and oxidizer charge to at least one conduit and initiating
combustion of the charge. The combustion generates a shock wave to
which the element is exposed, dislodging and/or otherwise removing
the deposits.
[0005] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages of the invention will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a partially schematic view of a coal-fired boiler
system.
[0007] FIG. 2 is a view of a boiler unit of the system of FIG.
1.
[0008] FIG. 3 is a longitudinally cut-away view of a heat exchanger
of the system of FIG. 1 with a first detonative core cleaning
system.
[0009] FIG. 4 is a partially schematic streamwise view of the heat
exchanger of FIG. 3.
[0010] FIG. 5 is a longitudinally cut-away view of a heat exchanger
of the system of FIG. 1 with a second detonative core cleaning
system.
[0011] FIG. 6 is a partially schematic streamwise view of the heat
exchanger of FIG. 5.
[0012] FIG. 7 is a longitudinally cut-away view of a heat exchanger
of the system of FIG. 1 with a third detonative core cleaning
system.
[0013] FIG. 8 is a partially schematic streamwise view of the heat
exchanger of FIG. 7.
[0014] FIG. 9 is a longitudinally cut-away view of a heat exchanger
of the system of FIG. 1 with a fourth detonative core cleaning
system.
[0015] FIG. 10 is a partially schematic streamwise view of the heat
exchanger of FIG. 9.
[0016] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0017] FIG. 1 shows a schematic view of a pulverized coal-fired
electric power plant 20. The exemplary plant may be an electrical
power plant having a steam generator 22 providing steam to a steam
turbine electrical generator unit 24. Along a combustion flowpath,
the steam generator 22 has an upstream radiant (furnace) zone 26
followed by a downstream convective (backpass) zone 28. The steam
generator 22 receives input flows of coal 30, air 32, and water
34.
[0018] The coal 30 passes through a pulverizer system 40. The air
flow 32 passes through an air heater 50 (discussed below) at a
downstream end of the backpass 28. The backpass heat exchangers may
comprise vertical/streamwise or horizontal/transverse tube arrays.
The air enters the furnace 42 as a preheated flow 52 partially
including entrained pulverized coal 44. The furnace serves as a
combustor combusting the coal and air mixture. A combustion flow 54
passes downstream along the combustion/exhaust flowpath.
[0019] The water flow 34 enters the convective zone 28 where it is
preheated in an economizer 56 before entering the vertical walls
(water walls-typically vertically extending tube arrays) 58 of the
furnace 42. Heat exchange from the combustion products 54 boils the
water to produce steam. Downstream along both the gas/combustion
products flowpath and water/steam flowpath, the steam is
superheated to high temperature and, in turn, delivered to a high
pressure turbine 60. Exemplary superheating occurs in a two-stage
process, first in a primary superheater 62 across the convective
zone upstream of the economizer 56 and then in a pendant secondary
superheater 64 on the radiant zone. In the radiant zone 26, flow is
primarily upward and, in the convective zone, primarily downward.
The two zones are separated by a bull nose 66 adjacent the pendant
heat exchanger(s).
[0020] Steam from the high pressure turbine 60 continues along the
water/steam flowpath and returns to the boiler to be reheated.
Exemplary reheating is in a two-stage process, with a primary
reheating (e.g., in a heat exchanger 70 across the convective zone
between the primary superheater 62 and economizer 56) and a
secondary reheating (e.g., in a pendant reheater 72 spanning the
radiant and convective zones). Thereafter, the re-heated steam is
delivered to an intermediate pressure turbine 80.
[0021] Steam exiting the intermediate pressure turbine 80 is
directed to a low pressure turbine 82. Steam (and optionally water)
exiting low pressure turbine 82 may proceed to a condenser 84 for
correction and processing (e.g., to return as the stream 34).
Energy extracted by the turbines drives an electrical generator 90
to produce electrical power.
[0022] After heating the water in the backpass region, the flow 54
heats the incoming air in the air heater 50 and then may proceed to
a pollution control system 100. The exemplary system 100 includes
an upstream chemical scrubber 102 and a downstream particulate
removal device 104 (e.g., a bag house or electrostatic
precipitator). Thereafter, the combustion products may pass through
a stack 110 for discharge to atmosphere.
[0023] FIG. 2 shows the air heater 50 as a rotary air heater having
a housing or body 120. The housing 120 has a first portion 122
along the exhaust flowpath 124 and a second portion 126 along the
inlet air flowpath 128. A heat transfer core 130 is mounted within
the housing to rotate about an axis 132. FIG. 3 shows the exemplary
core 130 as including a hub 140 supported by an axle to be driven
by an electric motor for rotation about the axis 132. A plurality
of heat transfer surfaces 142 (e.g., plates) extend radially
outward from the hub to a periphery 144. The core has a first axial
surface 150 and a second axial surface 152. In the exemplary
implementation, the first axial surface 150 is upstream along the
exhaust flowpath and the second axial surface 152 is downstream.
Depending upon implementation, the surface will not be a single
face but, rather, will be formed by discrete portions (e.g., edge
portions of plates). The rotation of the core brings heat transfer
portions of the core 130 sequentially through the exhaust gas
flowpath and the inlet air flowpath. The exemplary heat exchanger
is positioned so that the heat exchange is counterflow (i.e., the
exhaust flow and air inlet flow are in opposite directions).
[0024] As so-far described, the system is illustrative of just one
of a variety of plant configurations to which the present invention
may be applied. According to the present invention, one or more
detonative cleaning systems may be located along the air/combustion
products flowpath and positioned to clean the element.
[0025] FIGS. 3 and 4 show an exemplary cleaning system 220. The
exemplary system 220 includes a plurality of pulsed combustion
devices 222 and 223. In the exemplary implementation, two devices
are shown, the first device 222 being upstream of the core along
the exhaust flowpath and the second device 223 being downstream of
the core along the exhaust flowpath. Each device 222, 223 has a
conduit 224 having an outlet 226 at one end in interior 228 of the
housing 120 and facing an associated core axial end 150, 152.
Exemplary combustion conduits have lengths of 0.5-4m and
cross-sectional areas of 20-730 cm.sup.2. The conduit 224 may
include one or more inlets for receiving fuel and oxidizer. FIG. 2
shows exemplary fuel and oxidizer lines 240 and 242 coupled to
common fuel and oxidizer sources 244 and 246 (e.g., tank systems).
Exemplary fuel consists in majority part, by mass, of fuel selected
from the group consisting of hydrogen, hydrocarbon fuels, and their
mixtures. Exemplary oxidizer consists essentially of oxygen (e.g.,
from liquid oxygen tanks). Alternative oxidizer is compressed air.
Ignitors (e.g., spark plugs 248) may be positioned to ignite
admitted fuel/oxidizer charges.
[0026] The exemplary system further includes a control module 250
which may be connected to a central control system 252. Additional
structural and operational details may be similar to those of
pulsed combustion cleaning apparatus such as shown in US Pregrant
Patent Publications 2005-0112516 and US 2005-0199743, the
disclosures of which are incorporated by reference herein as if set
forth at length.
[0027] The control system 252 may operate the devices 222 and 223
to repeatedly combust charges of the fuel and oxidizer. Exemplary
combustion includes detonation producing associated shock waves
270. The shockwaves may pass along the core plates, cleaning the
plate surfaces.
[0028] Particular physical and operational parameters will depend
on the characteristics of the heat exchanger. For coal-powered
plants, this may partially be influenced by the nature of the
particular coal being burned. and the nature of the particular
heart exchanger core. The exemplary devices 222 and 223 may be
fired simultaneously (e.g., repetitively and without interruption
while the furnace is in operation or sequentially).
[0029] An exemplary control and firing protocol involves a series
of discharges timed to provide full circumferential coverage. For
example, the coverage of a single firing may be deemed effective
for a relatively small sector (e.g., .about.10.degree., more
broadly 5-20.degree.). The firing may be synchronized to the
rotation of the core so as to provide complete coverage. If the
firing cycle is short enough, consecutive sectors may be
progressively sequentially cleaned with the next uncleaned sector
being cleaned immediately after the prior sector. If the
cycle/refresh rate is not sufficient for this, an uncleaned sector
may be allowed to pass unaddressed through the cleaning zone. For
example, one full revolution plus the sector increment (e.g., the
.about.10.degree.) could pass between each of the firings (an
exemplary thirty-six total firings, each separated from the prior
firing by 370.degree., if the increment is 10.degree.).
[0030] Other timing variations involve redundant coverage of
firings, repeat firings along a given sector, and the like. Other
variations involve different delays between firings. For example,
if the cycle/refresh rate is sufficient the second firing could be
made before a full revolution has passed from the first firing, but
sill leaving an intervening uncleaned portion. With the 10.degree.
example, the second firing could be more than 10.degree. but less
than 370.degree. after the first, etc. For example the second
firing could be 180.degree. after the first. The third could be
190.degree. after the second. The fourth could be 180.degree. after
the third, with subsequent alternating 190.degree. and 180.degree.
intervals. There could be a rotation sensor 280 for detecting
rotation of the core and coupled to the control system to permit
the synchronization.
[0031] An exemplary operation is a continuous operation with
individual discharges/firings at a fixed frequency (or nearly fixed
due to the synchronization with rotation noted above). An exemplary
nominal frequency is 0.5-2.0 firings per minute. Alternatively,
each full cleaning of the core may be initiated responsive to
sensed parameters passing a predetermined first threshold and/or
the passage of a predetermined interval. An exemplary interval may
be up to daily. An exemplary sensed condition may involve a
pressure difference across the core on one or both of the hot side
and cool side (e.g., as detected by upstream pressure sensor 284
and downstream pressure sensor 286). The cleaning may continue
until the sensed condition has passes (below for a pressure drop) a
predetermined second threshold.
[0032] FIGS. 5 and 6 show an alternate system configuration having
respective upstream and downstream devices 320 and 322. the devices
have conduits 324 which may be similar to conduits 224 except for
the outlet 326. Relative to the outlet 226, the outlet 326 is
closer to the wall surface of the body 120. The outlet 326, however
is directed obliquely relative to the adjacent core surface/end
150, 152 to compensate so that the wave 340 has adequate
coverage.
[0033] FIGS. 7 and 8 show an alternate system configuration having
respective upstream and downstream devices 420 and 422. the devices
have conduits 424 which may be similar to conduits 224 except for
having multiple outlets 426, 428, 430, and 432 in a linear array
along the side of the conduit. The array extends to a closed end
434. The conduit 424 may thus have a greater penetration into the
flowpath. The outlets, however may produce overlapping shock waves
450 which yield a more radially uniform and circumferentially
concentrated net effect.
[0034] FIGS. 9 and 10 show an alternate system configuration having
respective upstream and downstream devices 520 and 522. the devices
have conduits 524 which may be similar to conduits 424 except for
one-to-all of: a progressive (e.g., step-wise) decrease in conduit
cross-sectional area along the array of outlets 526, 528, 530, and
532; a progressive decrease in outlet size ; and a progressive
decrease in outlet spacing. The array extends to a closed end 534.
The outlets, may produce overlapping shock waves 450, 452, 454, and
456 which yield a more radially progressive distribution that
compensates for the relatively slower speed of inboard portions of
the core passing through the influence of the shock waves. The
circumferential span of the effective shockwave footprint on the
core may thus radially increase.
[0035] One or more embodiments have been described. Nevertheless,
it will be understood that various modifications may be made. For
example, when implemented in a reengineering or upgrade of an
existing system configuration or system, details of the existing
configuration may influence details of any particular
implementation. Although illustrated with respect to a coal-burning
plant, the invention applies to other heat transfer facilities that
produce particulate. Some prime examples would be trash
incinerators and biomass/wood burners. Although shown fixed, the
conduits may be retractable (e.g., as are retractable sootblowers).
Accordingly, other embodiments are within the scope of the
following claims.
* * * * *