U.S. patent application number 11/296261 was filed with the patent office on 2007-06-14 for method and apparatus for cooling and repairing of power plant boiler.
This patent application is currently assigned to AVISTAR, INC.. Invention is credited to Philip R. Gangloff.
Application Number | 20070130949 11/296261 |
Document ID | / |
Family ID | 38137914 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070130949 |
Kind Code |
A1 |
Gangloff; Philip R. |
June 14, 2007 |
Method and apparatus for cooling and repairing of power plant
boiler
Abstract
A method for repairing power plant boilers provides for a water
mist insertion into the furnace to provide for more rapid cooling,
which allows personnel to enter into the furnace to conduct repairs
in a shorter time. Water mist is provided by air-water mixing
atomizing sprayers that are inserted into the boiler. Existing
power plant oil igniter lighters may be switched from oil to water
to provide the air-water mixed atomized mist.
Inventors: |
Gangloff; Philip R.;
(Farmington, NM) |
Correspondence
Address: |
SNIDER & ASSOCIATES
P. O. BOX 27613
WASHINGTON
DC
20038-7613
US
|
Assignee: |
AVISTAR, INC.
Albuquerque
NM
|
Family ID: |
38137914 |
Appl. No.: |
11/296261 |
Filed: |
December 8, 2005 |
Current U.S.
Class: |
60/646 |
Current CPC
Class: |
F22B 35/00 20130101;
F01K 13/025 20130101 |
Class at
Publication: |
060/646 |
International
Class: |
F01K 13/02 20060101
F01K013/02; F01K 21/06 20060101 F01K021/06 |
Claims
1. A method for repairing a power plant comprising the steps of:
identifying a condition in a power plant that requires repair;
shutting down of the power plant; switching oil igniter fluid from
oil to water; turning on the oil igniter to provide an atomized
water mist inside of a combustion area of the power plant;
measuring temperature inside of the power plant; initiating repair
when the temperature is reduced to a first predetermined level
which is tolerable by a human being inside of a work area of the
power plant, and repairing the power plant.
2. A method for repairing a power plant according to claim 1
further comprising the step of: turning on the oil igniter atomized
water mist that provides the atomized water mist when power plant
burners are turned off.
3. A method for repairing a power plant according to claim 2
further comprising the step of: turning off the oil igniter
atomized water mist when repair is being made in an area where the
mist interferes with repair procedures.
4. A method for repairing a power plant according to claim 2
further comprising the step of: turning off the oil igniter
atomized water mist when it is no longer required to maintain
temperature at a tolerable level in a work area.
5. A method for repairing a power plant according to claim 2
wherein the step of measuring temperature comprises measuring wet
and dry bulb temperatures in the work area.
6. A method for repairing a power plant according to claim 1
wherein there are a plurality of oil igniters that produce atomized
water when switched from oil to water.
7. A method for repairing a power plant according to claim 1
wherein the oil igniter is a lighter used in a coal fired
boiler.
8. A method for repairing in a power plant according to claim 1
wherein the oil igniter is a lighter that inserts a mixture of oil
and air into the boiler during boiler start up.
9. A method for repairing a power plant according to claim 1
wherein the step of switching from oil to water comprises
activating a transfer valve which switches feed fluid to a oil
igniter nozzle from oil to water.
10. A method for repairing a power plant according to claim 1
wherein the oil igniter as a lighter used in a coal fueled power
plant.
11. A method for repairing a power plant according to claim 1
wherein the oil igniter is a primary burner used in an oil fueled
power plant.
12. A method for repairing a power plant according to claim 1
wherein the repair is a tube repair.
13. A method for repairing a power plant according to claim 1
wherein the lighter or igniter internally mixes air with water in a
nozzle.
14. A method for repairing a power plant boiler according to claim
1 further comprising the step of: spraying said mist into corners
of said boiler.
15. A method for repairing a power plant boiler comprising the
steps of: identifying a tube leak condition in a power plant
boiler; shutting down of the power plant; inserting into the boiler
an air and water mixing nozzle; turning on the air and water mixing
nozzle that provides an atomized water mist inside of a combustion
area of the boiler; measuring temperature inside of the power plant
boiler; initiating tube repair when the temperature is reduced to a
first predetermined level which is tolerable by a human being in a
work area of the power plant boiler, and repairing the power
plant.
16. A method for repairing a power plant according to claim 15
further comprising the step of: turning on the atomized water mist
when power plant burners are turned off.
17. A method for repairing a power plant according to claim 15
further comprising the step of: turning off the oil igniter
atomized water mist when repair is being made in an area where the
mist interferes with repair procedures.
18. A method for repairing a power plant according to claim 15
further comprising the step of: turning off the oil igniter
atomized water mist when it is no longer required to maintain
temperature at a tolerable level in a work area.
19. A method for repairing a power plant according to claim 15
wherein the step of measuring temperature comprises measuring wet
and dry bulb temperatures.
20. A method for repairing a power plant according to claim 15
wherein there are a plurality of nozzles.
21. A method for repairing a power plant according to claim 15
wherein the nozzle is an internal or external air and water mixing
nozzle which is placed on the end of a tube which conveys both air
and water to the nozzle.
22. A method for repairing a power plant according to claim 15
wherein the air and water mixing nozzle is a nozzle of an oil
ignitor lighter.
23. An apparatus for cooling a power plant boiler comprising: a
port located in a wall of the boiler; an air and water mixing
mister which is inserted into the port; and an air and water supply
that is connected to said mixing mister; wherein the air and water
mixing mister inserts an air water mist into the power plant boiler
and cooling is provided by evaporation of the mist.
24. An apparatus for cooling a power plant boiler in accordance
with claim 23 wherein the air and water mister is an oil igniter
that has water inserted into oil lines.
25. An apparatus for cooling a power plant boiler in accordance
with claim 24 wherein the oil igniter is an ignitor used to ignite
a coal fired boiler.
26. An apparatus for cooling a power plant boiler in accordance
with claim 23 wherein the air and water mister is an air and water
mixing nozzle on the end of an insertion pipe.
Description
FIELD OF THE INVENTION
[0001] This invention is for operation and maintenance of power
plant boilers that are used for generating electricity. The
invention by reducing the amount of down time during a forced
outage reduces cost incurred as a result of the outage.
BACKGROUND OF THE INVENTION
[0002] When a condition in a power boiler forces an outage, it is
necessary for personnel to enter the boiler to perform repair
operations. A typical condition that requires repair is a tube leak
that may be found in a coal, gas or oil fired boiler. Such tube
leaks necessarily force outages, which must be quickly
repaired.
[0003] A typical power boiler may experience from four to five
outages per year with each forced outage lasting approximately 72
hours. Each forced outage may cost the power utility approximately
1.3 million in net revenue. Therefore, if the outage time can be
reduced, the cost per outage will also necessarily be reduced.
[0004] Before inspectors and/or welders can enter a boiler to make
repairs, it must be cooled from 800 to 1000.degree. F. to a barely
tolerable 105.degree. F. The tolerance level is often specified by
the standard set forth by OSHA. Such tolerance standards may
require that the temperature not exceed 95.degree. F. at a
specified humidity.
[0005] In the prior art it is known to use fans, which are present
in a power plant boiler's air supply system to reduce the boiler
temperature after turning off the boiler. The use of such fans
generally takes from 12 to 24 hours to cool the power plant
depending upon the outside ambient air temperature and humidity
conditions.
[0006] In the case where cooling is accomplished by ambient air
forced through a boiler using the power plant's own large force
draft fans, the force draft fans heat the ambient air by 10 to
15.degree. F. as it is pumped into the unit. This becomes a
significant problem when the ambient air outside is already greater
than 90.degree. F. and where it is necessary to cool the boiler to
105.degree. F. or less for entry of personnel into the boiler for
repair purposes.
[0007] Even a five to eight percent reduction in down time results
in substantial savings to a power plant operator. In the case of
the San Juan Power Plant located in New Mexico, in 2003 and 2004,
there were a total of 1,490,994 megawatts lost due to 44 tube
leaks. Approximately 82,000 to 124,000 megawatts in output are
gained if down time is reduced 5 to 8%. At a cost $41.08/mw this
represents $3,368,000 to $5,093,000 over the two-year period. This
is a significant savings.
BRIEF SUMMARY OF THE INVENTION
[0008] This invention utilizes a spray, which is a mixture of
high-pressure air, and water, which produces a fine mist of very
small droplets within the boiler. The mist has an advantage of
preventing tube cracking due to sustained contact of the water
directly with tubes (saturation) during a period when the tubes are
at a high temperature. A phenomenon known as hydrogen embrittlement
can result in subsequent tube cracking in a power plant boiler. Use
of a mist avoids impinging a sustained water stream directly on the
boiler water wall when the boiler water wall is at a maximum
temperature condition (typically a 350 to 400.degree. F.
differential temperature between the water used and the metal
temperature for SA210A1 or similar materials). Direct water
impingement or "wetting" can cause a rapid quenching, which can
result in cracking or hydrogen embrittlement of boiler tubes. When
a mist is used, it provides for a condition inside of the boiler,
which prevents droplets from impinging directly on high temperature
boiler tubes for a sustained period when the misting devices are
turned on.
[0009] When a water mist is sprayed into the firebox, the boiler
becomes a large evaporative cooler. There is an increase in the
humidity of the cooling air, which allows the heat of vaporization
to work in the favor of the plant operator to reduce temperature
more quickly. In this invention, a fine mist is produced by air and
water mixing atomizer nozzles. The fine mist can be conveniently
produced by existing igniter oil lighters which are used in coal
fired plants, by separate tubes which are inserted into the boiler
which have at their tip, nozzles for mixing air with water or a
combination of existing igniter lighter systems and additional
air-water mist insertion tubes. In a-typical power plant
operation., air and fuel are supplied to the igniters from a
centralized source. When igniter nozzles are utilized, the igniter
is inserted into the boiler and its fluid supply is switched from
oil to water. This same source of compressed air can also be
utilized for supplying air to the separate mist spray insertion
devices, which combine air and water at the tip to produce a
mist.
[0010] As the mist is inserted into the boiler, the latent heat of
evaporation removes large quantities of heat from the air. The fans
in the boiler plant are left on, thereby forcing the high humidity
and therefore high heat content air through the boiler and to its
exhaust system.
[0011] Although tube leaks are the most common cause of a forced
outage, there may be other reasons for a forced outage, or other
reasons for temporarily shutting down a power plant boiler for
repair purposes. In any event, it is important as a matter of
economics to perform all necessary repairs as rapidly as possible.
This in turn requires rapid reduction in boiler temperatures, which
will allow quicker entry into the boiler area for purposes of
repair. In a typical boiler, repair may occur to tubes located
directly in the burner area, tubes located in the superheat areas
of the convection pass, the convection pass heat recovery area,
tubes associated with the economizers, and systems located
downstream from the boiler towards the gas outlet, which would
include the dampers, electrostatic precipitators and regenerative
air heaters.
[0012] It is known in the prior art, such as U.S. Pat. No.
6,015,099 and U.S. Pat. No. 5,540,383, both to Ducey, to use
sprayed pressurized water for evaporative cooling. However, the
prior art devices shown in these patents do not mix air and water,
and rely on high-pressure water only to cool locations where people
may assemble at outdoor events. There is no suggestion in this
non-analogous prior art to utilize existing water and air supplies
and existing oil fired igniters in a power plant for producing a
mist to accelerate cooling of the power plant during a forced shut
down.
[0013] A method for repairing a power plant comprises the steps of
identifying a condition in a power plant that requires repair;
shutting down of the power plant; switching oil lighter fluid from
oil to water; turning on the oil lighter which provides an atomized
water mist inside of a combustion area of the power plant;
measuring temperature inside of the power plant boiler; initiating
repair when the temperature is reduced to a first predetermined
level which is tolerable by a human being inside of a work area of
the power plant, and repairing the power plant.
[0014] The method further comprises steps of:
[0015] (1) turning on the oil igniter atomized water mist that
provides the atomized water mist when power plant burners are
turned off;
[0016] (2) turning off the oil lighter atomized water mist when
repair is being made in an area where the mist interferes with
repair procedures;
[0017] (3) turning off the oil lighter atomized water mist when it
is no longer required to maintain temperature at a tolerable level
in a work area;
[0018] (4) measuring temperature that comprises measuring wet and
dry bulb temperatures in the work area;
[0019] (5) using a plurality of oil lighters that produce atomized
water when switched from oil to water;
[0020] (6) using an ignitor used in a coal fired boiler;
[0021] (7) using a transfer valve to switch feed fluid to a burner
nozzle from oil to water;
[0022] (8) using a primary burner used in an oil fueled power
plant;
[0023] (9) repairing a tube leak;
[0024] (10) using an internal or external mixing nozzle to mix air
with water;
[0025] (11) spraying the mist into corners of said boiler;
[0026] (12) inserting into the boiler an air and water mixing
nozzle, which is on the end of a pipe that is inserted into a
boiler port.
[0027] This apparatus for cooling a power plant boiler has a port
located in a wall of the boiler, an air and water mixing mister
that is inserted into the port, and an air and water supply that is
connected to a mixing mister nozzle. The air and water mixing
mister inserts an air water mist into the power plant boiler and
cooling is provided by evaporation of the mist.
DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 shows a power plant of the type manufactured by
Babcock and Wilcox, which is rapidly cooled in accordance with this
invention.
[0029] FIG. 2 shows a tip of an oil igniter lighter used typically
in coal fired plants.
[0030] FIG. 3 shows an igniter lighter having a transfer valve for
switching from oil to water.
[0031] FIG. 4 shows a water-injecting nozzle on the tip of an air
and water-conducting pipe, which may be inserted into a boiler.
[0032] FIG. 5 shows an atomizing oil burner head, mounted on
concentric pipes, that is creating an atomized mist of this
invention.
[0033] FIG. 6 shows a second view of the atomizing mist head of
FIG. 5.
[0034] FIG. 7 shows a third view of the atomizing mist head of FIG.
5.
DETAILED DESCRIPTION
[0035] In FIG. 1 there is shown a Babcock and Wilcox radiant reheat
boiler of the type used by the Power Company of New Mexico's San
Juan Station located at Waterflow, New Mexico. The boiler (10) has
a furnace area (12) and is fired by coal burners (14). The coal
burners are provided with an air supply or an air input (16). There
are a large number of coal burners, such as a group of three high
and seven wide or a total of twenty-one burners on one side of the
furnace (12). A boiler having burners on two sides may have 42 coal
burners. Although not shown in FIG. 1, there is a second group of
burners located to the left hand side of the furnace (12).
Associated with each burner is an oil igniter (18). The oil igniter
guns are supplied with oil and air, which is supplied by a central
air supply within the power plant. In this invention, the oil
igniter guns (18) may also be connected to a water supply for the
plant. When the oil igniter guns (18) are connected to a water
supply and turned on, they will inject a mist spray, which is
produced by the water and air forced into the furnace (12) by the
oil igniter guns. The oil igniter guns (18) are shown in FIG. 1 in
a position where they are actually inserted into the furnace.
During normal furnace operation, after ignition of the coal burners
(14) the oil igniter guns are retracted from the furnace to prevent
damage due to heat.
[0036] In addition to oil igniter guns (18) there are also provided
tubes (20) that have at their tip air-water mixing nozzles (22)
located at their tip. These additional tubes are fed with water and
air from the power plant. The air mix nozzles produce a mist and
can be located anyplace within the boiler that there is a
convenient access port.
[0037] Depending from the top of the boiler are shown pendent super
heater walls, which may require repair in addition to tube walls
located in the furnace area (12). Still further, to the right hand
side of FIG. 1 are shown reheaters and economizers (26), which may
require repair. When a mist is inserted into the furnace 12 by
either the oil igniter guns (18) supplied with water, or the
misting nozzles (22) which are supplied by the air and water
systems available in the power plant, cooling may be effected at
different locations within the boiler and at rates which provide
evaporative cooling in order to quickly cool areas of the boiler
which may require personnel to enter and make necessary
repairs.
[0038] Boilers of the type shown in FIG. 1 are generally
constructed with a rectilinear cross-section, and not a circular
cross-section. Since the cross-section is rectilinear, the mist
produced by this invention is particularly advantageous because the
mist can travel into the corners of the furnace. Also, the cool air
but no mist travels to super heater areas of the convection pass or
heat recovery area (28) in order to provide uniform and efficient
cooling during cooling of the boiler. The cool air travels past
area (24), but this air has only vapor and no water mist because if
water is present it can react with ash in this area and cause
damage to the convection pass.
[0039] FIG. 2 shows a nozzle of the type typically used on an oil
igniter gun, see (22), FIG. 1. The nozzle (30) has a tip (32),
which is an internal mixing tip. As shown in the drawing, there are
two spray ports, which mix oil and water at points (34) internally
of the head. However, there may be typically five or six such
internal mixing ports, which are provided by drilling the head
along the drill holes shown. A first central passage way (36)
supplies oil to the head and a second outer passage way (38)
provides air to the head. The drill hole at an angle of 45.degree.
carries the oil to the mixing point while the drill hole at an
angle of approximately 150 carries the air to the mixing point
(34). An outer pipe (38) receives the mixing head (32) that is
secured by a threaded connection. The internal pipe (40) is
inserted into the base of the nozzle and a seal may be provided by
o-rings or the like. Pipe (40) provides passage (36) for oil
supplied to the head.
[0040] FIG. 3 shows an igniter lighter assembly of an oil igniter
gun (18) of FIG. 1, where the tip (30) is at the end of a pipe
section (52). The tip (30) can be inserted into the furnace for
igniting the coal, and withdrawn from the furnace (12) when the not
in use in order to prevent damage to the igniter (18) from the coal
firing. The oil igniter gun includes an assembly (53) for attaching
the tubes (52) to the (boiler) plant air supply and oil supply. In
this invention, water is used in place of the oil. Water is also
readily available in a power plant. A transfer valve (56) is
provided for switching from oil to water. The transfer valve is
preferably an electrically operated valve, which can be controlled
from a single location by pressing of button by an operator or by a
computer, which operates the power plant. Once the oil igniter gun
is switched from oil to water, it is operated in a manner typical
of any other igniter with the exception that water is substituted
for the oil, which is sprayed into the power plant boiler. In a
large coal fired boiler it is not necessary to use all igniters to
produce a cooling mist.
[0041] Any number of igniters (18) may be used at any one time to
supply a mist to the furnace area (12). Any number of igniters can
be controlled simultaneously by electrical controls that are either
manual or computer operated. The igniter (18) and igniter valves
(56) can also be each operated manually.
[0042] In FIG. 4 there is shown a mist-injecting pipe (62), which
is essentially the same as the pipe (52) and is connected also to a
nozzle (30). In this arrangement, air is inserted into the outside
pipe (38) (FIG. 2), and water is inserted into the inside pipe.
Manually controlled air valve and manually controlled water valve
(66) provide for control of the mist ejected from nozzle (30). This
assembly is made to be manually inserted through convenient ports
in the furnace walls for purposes of providing cooling at selected
locations.
[0043] FIG. 2 shows a typical internal mixing atomizing head used
for oil igniters. If separate injecting pipes (FIG. 4) are used, an
external mixing head of the type known in paint spraying may be
used. External mixing heads combine the fluid and air at a point
outside of the nozzle where the streams intersect.
[0044] In the case where the igniter burners are gas fired instead
of oil fired, there will, of course, be no atomizing air fuel
mixing nozzles that can be connected to a water air source.
However, boiler cooling during shut down can still be performed by
inserting mist injecting pipes (62) into the boiler. These may be
inserted at any convenient opening in the boiler, such as at doors
that hold flame observation windows, other access ports, or at
openings created by withdrawal of gas burners.
* * * * *