U.S. patent application number 12/969102 was filed with the patent office on 2011-04-07 for piping, header, and tubing arrangements for solar boilers.
This patent application is currently assigned to Babcock Power Services, Inc.. Invention is credited to Andrew Plotkin, Russell Ricci.
Application Number | 20110079217 12/969102 |
Document ID | / |
Family ID | 43828385 |
Filed Date | 2011-04-07 |
United States Patent
Application |
20110079217 |
Kind Code |
A1 |
Ricci; Russell ; et
al. |
April 7, 2011 |
PIPING, HEADER, AND TUBING ARRANGEMENTS FOR SOLAR BOILERS
Abstract
A header system for fluid circulation in a boiler includes a
header configured to conduct fluid therethrough for circulating
fluids in a boiler. A plurality of suction lines are connected in
fluid communication with the header. Each suction line is
configured and adapted to connect a respective pump in fluid
communication with the header. A plurality of downcomers are
connected in fluid communication with the header. Each downcomer is
configured and adapted to connect the header in fluid communication
with a steam drum. The header, suction lines, and downcomers are
configured and adapted to draw substantially equal amounts of fluid
from each of the downcomers even when flow is uneven among the
suction lines. A plurality of cascaded headers can fluidly connect
the circulation header to a steam generator. The plurality of
cascaded headers is configured and adapted to provide a
substantially equal flow to panels of the steam generator.
Inventors: |
Ricci; Russell; (Brookfield,
MA) ; Plotkin; Andrew; (Worcester, MA) |
Assignee: |
Babcock Power Services,
Inc.
Worcester
MA
|
Family ID: |
43828385 |
Appl. No.: |
12/969102 |
Filed: |
December 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12547650 |
Aug 26, 2009 |
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12969102 |
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12620109 |
Nov 17, 2009 |
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12547650 |
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61151984 |
Feb 12, 2009 |
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61152011 |
Feb 12, 2009 |
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61152035 |
Feb 12, 2009 |
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61152049 |
Feb 12, 2009 |
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61152077 |
Feb 12, 2009 |
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61152114 |
Feb 12, 2009 |
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61152286 |
Feb 13, 2009 |
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61151984 |
Feb 12, 2009 |
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61152011 |
Feb 12, 2009 |
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61152035 |
Feb 12, 2009 |
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61152049 |
Feb 12, 2009 |
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61152077 |
Feb 12, 2009 |
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61152114 |
Feb 12, 2009 |
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61152286 |
Feb 13, 2009 |
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Current U.S.
Class: |
126/663 ;
122/360 |
Current CPC
Class: |
Y02E 10/41 20130101;
F22B 1/006 20130101; Y02E 10/40 20130101; F24S 80/30 20180501; F22B
37/225 20130101; F24S 20/20 20180501 |
Class at
Publication: |
126/663 ;
122/360 |
International
Class: |
F24J 2/24 20060101
F24J002/24; F22B 37/22 20060101 F22B037/22 |
Claims
1. A header system for fluid circulation in a boiler comprising: a)
a header configured to conduct fluid therethrough for circulating
fluids in a boiler; b) a plurality of suction lines connected in
fluid communication with the header, each suction line being
configured and adapted to connect a respective pump in fluid
communication with the header; and c) a plurality of downcomers
connected in fluid communication with the header, wherein each
downcomer is configured and adapted to connect the header in fluid
communication with a steam drum, wherein the header, suction lines,
and downcomers are configured and adapted to draw substantially
equal amounts of fluid from each of the downcomers even when flow
is uneven among the suction lines.
2. A header system as recited in claim 1, wherein the header
defines a longitudinal axis and has an inlet section and an opposed
outlet section that is spaced apart from the inlet section along
the longitudinal axis, and wherein the suction lines are all
connected to the outlet section of the header, and wherein the
downcomers are all connected to the inlet section of the
header.
3. A header system as recited in claim 2, wherein there are four
downcomers, an inner two of the downcomers being inboard with
respect to two outboard downcomers.
4. A header system as recited in claim 3, wherein each inner
downcomer is connected to the header at a first common axial
position on the header, and wherein each outer downcomer is
connected to the header at a second common axial position on the
header, and wherein the first and second axial positions are spaced
apart axially along the longitudinal axis of the header.
5. A header system as recited in claim 2, wherein the downcomers
are oriented perpendicular to the header where connected
thereto.
6. A header system as recited in claim 5, wherein the downcomers
are all oriented parallel to one another at inlet ends thereof.
7. A header system as recited in claim 2, wherein one or more of
the suction lines are oriented perpendicular to the header where
connected thereto.
8. A header system as recited in claim 7, wherein the suction lines
are all oriented parallel to one another at outlet ends
thereof.
9. A header system as recited in claim 7, wherein two suction lines
are staggered axially with respect to one another where connected
to the header.
10. A header system as recited in claim 7, wherein two suction
lines are axially aligned with respect to one another where
connected to the header.
11. A header system as recited in claim 7, wherein a third suction
line is connected to the header in axial alignment therewith.
12. A header system as recited in claim 7, wherein two suction
lines are axially aligned with respect to one another where
connected to the header, and wherein a third suction line is
connected to the header in axial alignment therewith.
13. A solar boiler for solar power production comprising: a) a
steam generator and a superheater each connected in fluid
communication with a steam drum; b) a plurality of downcomers
connected in fluid communication with the steam drum; c) a
vertically oriented circulation header fluidly connected to the
downcomers; and d) a plurality of suction lines in fluid
communication with the circulation header, the suction lines each
being configured and adapted to place a circulation pump in fluid
communication with the circulation header, wherein the circulation
header, suction lines, and downcomers are configured and adapted to
draw substantially equal amounts of fluid from each of the
downcomers even when flow is uneven among the suction lines.
14. A solar boiler as recited in claim 13, wherein the circulation
header defines a longitudinal axis and has an inlet section and an
opposed outlet section that is spaced apart from the inlet section
along the longitudinal axis, wherein the inlet section is above the
outlet section, and wherein the suction lines are all connected to
the outlet section of the header, and wherein the downcomers are
all connected to the inlet section of the header.
15. A solar boiler as recited in claim 13, further comprising a
plurality of cascaded headers fluidly connecting the circulation
header to the steam generator, wherein the plurality of cascaded
headers is configured and adapted to provide a substantially equal
flow to panels of the steam generator.
16. A boiler for power production comprising: a) a steam generator
and a superheater each connected in fluid communication with a
steam drum; b) a circulation header in fluid communication with the
steam drum and the steam generator for circulating water from the
steam drum into the steam generator; and c) a plurality of cascaded
headers fluidly connecting the circulation header to the steam
generator, wherein the plurality of cascaded headers is configured
and adapted to provide a substantially equal flow to panels of the
steam generator.
17. A boiler as recited in claim 16, wherein the plurality of
cascaded headers includes a flow path that passes through a series
of progressively smaller headers from the circulation header to the
panels of the steam generator.
18. A boiler as recited in claim 17, wherein there are at least
three header sizes between the circulation header and individual
tubes of the steam generator panels.
19. A boiler as recited in claim 16, wherein a second plurality of
cascaded headers fluidly connects the steam generator to the steam
drum to provide a saturated mixture of water and steam from the
steam generator to the steam drum.
20. A boiler as recited in claim 19, wherein the second plurality
of cascaded headers includes a flow path that passes through a
series of progressively larger headers from the panels of the steam
generator to the steam drum, wherein there are at least two header
sizes between individual tubes of the steam generator panels and
the steam drum.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S. patent
application Ser. No. 12/547, 650, filed Aug. 26, 2009. This
application is also a continuation in part of U.S. patent
application Ser. No. 12/620,109, filed Nov. 17, 2009. U.S. patent
application Ser. Nos. 12/547,650 and 12/620,109 each claim priority
to U.S. Provisional Application No. 61/151,984, filed Feb. 12,
2009, to U.S. Provisional Application No. 61/152,011, filed Feb.
12, 2009, to U.S. Provisional Application No. 61/152,035, filed
Feb. 12, 2009, to U.S. Provisional Application No. 61/152,049,
filed Feb. 12, 2009, to U.S. Provisional Application No.
61/152,077, filed Feb. 12, 2009, to U.S. Provisional Application
No. 61/152,114, filed Feb. 12, 2009, and to U.S. Provisional
Application No. 61/152,286, filed Feb. 13, 2009. Each of the
above-referenced applications is incorporated by reference herein
in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to solar power production, and
more particularly to boilers for solar power production.
[0004] 2. Description of Related Art
[0005] Solar power generation has been considered a viable source
to help provide for energy needs in a time of increasing
consciousness of the environmental aspects of power production.
Solar energy production relies mainly on the ability to collect and
convert energy freely available from the sun and can be produced
with very little impact on the environment. Solar power can be
utilized without creating radioactive waste as in nuclear power
production, and without producing pollutant emissions including
greenhouse gases as in fossil fuel power production. Solar power
production is independent of fluctuating fuel costs and does not
consume non-renewable resources.
[0006] Solar power generators generally employ fields of controlled
mirrors, called heliostats, to gather and concentrate sunlight on a
receiver to provide a heat source for power production. A solar
receiver typically takes the form of a panel of tubes conveying a
working fluid therethrough. Previous solar generators have used
working fluids such as molten salt because it has the ability to
store energy, allowing power generation when there is no solar
radiation. The heated working fluids are typically conveyed to a
heat exchanger where they release heat into a second working fluid
such as air, water, or steam. Power is generated by driving heated
air or steam through a turbine that drives an electrical
generator.
[0007] More recently, it has been determined that solar power
production can be increased and simplified by using water/steam as
the only working fluid in a receiver that is a boiler. This can
eliminate the need for an inefficient heat exchanger between two
different working fluids. This development has lead to new
challenges in handling the intense solar heat without damage to the
system. In a solar boiler, heat transfer rates can reach levels
around 2-3 times the heat transfer rate of a typical fossil fuel
fired boiler. This high heat transfer rate intensifies problems
related to maintaining even heating and flow distribution
throughout known designs of boiler panels. The high heat transfer
rate gives rise to high pressures and temperatures in the boiler
tubing and related structures.
[0008] In typical forced circulation boilers, such as coal fired
boilers, single or multiple circulation pumps are used to circulate
water from the drum through the steam generator panels, and back
into the drum as a mixture of saturated water and steam.
Traditional boilers often use multiple circulation pumps operating
in parallel for capacity and redundancy reasons. In a traditional
configuration, a plurality of pumps are connected in parallel along
the length of a horizontal header, each pump being connected to the
header by way of a suction line. The horizontal header is in turn
connected to the drum through a plurality of vertical downcomers.
Each pump draws water primarily from a specific portion of the drum
through the nearest downcomers. In the event of failure of one or
more of the pumps, the functioning pump or pumps draw uneven
amounts of water from the drum through the different downcomers,
creating an unbalance of flow in the drum. Unbalance along the
length of the drum can lead to varying drum water level along the
length of the drum. Uneven water level in the drum can cause many
problems including high carry-under (when saturated fluid enters
the downcomers) to a false low water level alarm or low water level
trip. Prolonged operation with large unbalances in drum water level
can also lead to constant water level alarms, water level trips,
long-term fatigue and metallurgical problems from overheating, and
affect the life and performance of the circulation pump.
[0009] Another aspect of traditional boilers, such as coal fired
boilers, is that there are typically downcomers from the drum that
feed four waterwall headers, namely two sidewall headers, a front
wall header, and a rear wall header. Each of these headers, in
turn, feeds a portion of the steam generator. This header
arrangement, when applied to solar boiler applications, can lead to
uneven flow from panel to panel, which can give rise to panel
failure due to the intense heating described above. This, together
with the with the circulation header arrangement described above,
can result in detrimental uneven flow throughout the boiler system,
and causes a risk of emergency shutdown or even failure of key
components.
[0010] Such conventional methods and systems have generally been
considered satisfactory for their intended purpose. However, there
is still a need in the art for boilers in general, and in
particular solar boilers, that allow for improved flow distribution
between the drum and circulation pumps. There also remains a need
in the art for such boilers with improved flow distribution to the
boiler panels. The present invention provides solutions for these
problems.
SUMMARY OF THE INVENTION
[0011] The subject invention is directed to a new and useful header
system for forced fluid circulation in a boiler. The system
includes a header configured to conduct fluid therethrough for
circulating fluids in a boiler. A plurality of suction lines are
connected in fluid communication with the header. Each suction line
is configured and adapted to connect a respective pump in fluid
communication with the header. A plurality of downcomers are
connected in fluid communication with the header. Each downcomer is
configured and adapted to connect the header in fluid communication
with a steam drum. The header, suction lines, and downcomers are
configured and adapted to draw substantially equal amounts of fluid
from each of the downcomers even when flow is uneven among the
suction lines.
[0012] In accordance with certain embodiments, the header defines a
longitudinal axis and has an inlet section and an opposed outlet
section that is spaced apart from the inlet section along the
longitudinal axis. The suction lines are all connected to the
outlet section of the header, and the downcomers are all connected
to the inlet section of the header.
[0013] In certain exemplary embodiments, there are four downcomers,
wherein an inner two of the downcomers are inboard with respect to
two outboard downcomers. Each inner downcomer is connected to the
header at a first common axial position on the header. Each outer
downcomer is connected to the header at a second common axial
position on the header. The first and second axial positions can be
spaced apart axially along the longitudinal axis of the header.
[0014] It is contemplated that the downcomers can be oriented
perpendicular to the header where connected thereto, and can all be
oriented parallel to one another at inlet ends thereof. Similarly,
one or more of the suction lines can be oriented perpendicular to
the header where connected thereto, and parallel to one another at
outlet ends thereof. Two suction lines can be staggered axially or
can be axially aligned with respect to one another where connected
to the header. A third suction line can be connected to the header
in axial alignment therewith.
[0015] The invention also provides a solar boiler for solar power
production. The solar boiler includes a steam generator and a
superheater each connected in fluid communication with a steam
drum. A plurality of downcomers are connected in fluid
communication with the steam drum. A vertically oriented
circulation header is fluidly connected to the downcomers. A
plurality of suction lines is in fluid communication with the
circulation header. The suction lines are each configured and
adapted to place a circulation pump in fluid communication with the
circulation header. The circulation header, suction lines, and
downcomers are configured and adapted to draw substantially equal
amounts of fluid from each of the downcomers even when flow is
uneven among the suction lines. It is contemplated that the
circulation header can have axially spaced apart inlet and outlet
sections as described above, wherein the inlet section is above the
outlet section.
[0016] The invention also provides a boiler for power production
having a plurality of cascaded headers fluidly connecting a
circulation header to a steam generator. The circulation header is
configured to circulate water from a steam drum into the steam
generator. The plurality of cascaded headers is configured and
adapted to provide a substantially equal flow to panels of the
steam generator.
[0017] In certain embodiments, the plurality of cascaded headers
includes a flow path that passes through a series of progressively
smaller headers from the circulation header to the panels of the
steam generator. There can be at least three header sizes and/or
levels between the circulation header and individual tubes of the
steam generator panels.
[0018] In accordance with certain aspects, a second plurality of
cascaded headers can be provided to fluidly connect the steam
generator to the steam drum to provide a saturated mixture of water
and steam from the steam generator to the steam drum. The second
plurality of cascaded headers can include a flow path that passes
through a series of progressively larger headers from the panels of
the steam generator to the steam drum. There can be at least two
header sizes and/or levels between individual tubes of the steam
generator panels and the steam drum.
[0019] These and other features of the systems and methods of the
subject invention will become more readily apparent to those
skilled in the art from the following detailed description of the
preferred embodiments taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] So that those skilled in the art to which the subject
invention appertains will readily understand how to make and use
the devices and methods of the subject invention without undue
experimentation, preferred embodiments thereof will be described in
detail herein below with reference to certain figures, wherein:
[0021] FIG. 1 is a front elevation view of an exemplary embodiment
of a solar boiler constructed in accordance with the present
invention, showing the solar boiler atop a solar receiver tower,
with a cut-away portion showing the steam drum and piping within
the interior boiler space;
[0022] FIG. 2 is an elevation view of a portion of an exemplary
circulation header typical of the prior art, showing the horizontal
header arrangement;
[0023] FIG. 3 is an elevation view of a portion of the solar boiler
of FIG. 1, showing the circulation header in a vertical header
arrangement with the inlets and outlets of the header spaced out
axially along the length thereof;
[0024] FIG. 4 is an elevation view of another exemplary embodiment
of a circulation header constructed in accordance with the present
invention, showing two staggered suction lines connecting the
header to two respective pumps; and
[0025] FIG. 5 is schematic view of a portion of the solar boiler of
FIG. 1, showing a cascading header arrangement for circulating
fluids through the boiler panels.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Reference will now be made to the drawings wherein like
reference numerals identify similar structural features or aspects
of the subject invention. For purposes of explanation and
illustration, and not limitation, a partial view of an exemplary
embodiment of a solar boiler in accordance with the invention is
shown in FIG. 1 and is designated generally by reference character
100. Other embodiments of solar boilers in accordance with the
invention, or aspects thereof, are provided in FIGS. 3-5, as will
be described. The systems of the invention can be used improve
circulation reliability and flow distribution within boilers, and
particularly in solar boilers.
[0027] With reference now to FIG. 1, solar boiler 100 for solar
power production is shown at the top of a solar receiver tower 102,
which can be surrounded by a field of heliostats for focusing solar
radiation on solar boiler 100. Solar boiler 100 includes a
plurality of solar boiler panels 104 forming a perimeter
surrounding a boiler interior space 106, which is visible through
the cut-away portion in FIG. 1. A support structure 108 within
boiler interior space 106 supports solar boiler panels 104. Boiler
panels 104 include a steam generator 110 with a superheater 112
contiguous therewith on top of boiler 100, and with a reheater 114
contiguous with steam generator 110 on the bottom of boiler 100.
Panels 104 for steam generator 110, superheater 112, and reheater
114 are described in commonly owned, co-pending U.S. patent
application Ser. No. 12/552,724, filed Sep. 2, 2009, which is
incorporated by reference herein in its entirety.
[0028] As can be seen in the cut-away portion of FIG. 1, a steam
drum 116 is mounted to support structure 108 within boiler interior
space 106. Boiler panels 104 define upper and lower extents of
boiler interior space 106, and drum 116 is mounted below the upper
extent of boiler interior space 106. More particularly, drum 116 is
mounted in interior space 106 within the elevation of superheater
112.
[0029] Since boiler panels 104 form a substantially contiguous heat
transfer surface configured to block solar radiation incident
thereon from boiler interior space 106, drum 116 is protected by
panels 104 from the intense thermal radiation incident on the solar
receiver during operation. Solar boiler panels 104 form four boiler
walls surrounding boiler interior space 106. Any other suitable
number of walls can be used without departing from the spirit and
scope of the invention. Four wall boiler configurations are
described in greater detail in commonly owned, co-pending U.S.
patent application Ser. Nos. 12/547,650 and 12/617,054, filed Aug.
26, 2009 and Nov. 12, 2009, respectively, each of which is
incorporated by reference herein in its entirety. Downcomers 152a,
152b, 152c, and 152d connected to steam drum 116 are also supported
by support structure 108.
[0030] Referring now to FIG. 2, an example of a traditional steam
drum 16 and circulation header 50 are shown. Four downcomers 52a,
52b, 52c, and 52d connect steam drum 16 to circulation header 50,
which is in turn connected to pumps 54a, 54b, and 54c by way of
suction lines 56a, 56b, and 56c, respectively. Under normal
operation, pumps 54a-54c circulate saturated water out from drum
16, through downcomers 52a-52d, header 50, suction lines 56a-56c,
through the steam generator, and back into drum 16 as a mixture of
saturated steam and water. However, if one or more of the pumps
54a-54c fails or otherwise loses capacity or reduces its flow rate,
the fluid levels inside drum 16 will become uneven. For example, if
pump 54a stops working, suction line 56a will effectively be
rendered inoperative. Since suction line 56a is in closest
proximity to downcomers 52a and 52b, the flow in those two
downcomers 52a and 52b will be reduced much more than will the flow
in the more distant downcomers 52c and 52d. The result is that
portions of drum 16 proximate the openings into downcomers 52a and
52b will have a higher fluid level than portions proximate
downcomers 52c and 52d, which may still provide suction at
near-normal levels. The uneven fluid levels across drum 16 will
create a flow unbalance in drum 16, which can cause high
carry-under or a false low water level alarm or low water level
trip. Prolonged operation with large unbalances in drum water level
can also lead to long-term fatigue and metallurgical problems
arising from overheating drum 16.
[0031] Referring now to FIG. 3, the header system for fluid
circulation in boiler 100 provides for even flow in the downcomers
even when flow in one or more of the suction lines is reduced. The
system includes circulation header 150 configured to conduct fluid
therethrough for circulating fluids in boiler 100. Three suction
lines 156a, 156b, and 156c are connected in fluid communication
with circulation header 150. Each suction line 156a, 156b, and 156c
is configured and adapted to connect a respective pump 154a, 154b,
and 154c in fluid communication with circulation header 150. Four
downcomers 152a, 152b, 152c, and 152d are connected in fluid
communication with circulation header 150. Each of the downcomers
152a-152d connects circulation header 150 in fluid communication
with steam drum 116.
[0032] Header 150 defines a longitudinal axis A and has an inlet
section 158 and an opposed outlet section 160. Outlet section 160
is spaced apart axially from inlet section 158 along the
longitudinal axis A. The suction lines 156a-156c are all connected
to outlet section 160, and the downcomers 152a-152d are all
connected to inlet section 158. All of the fluid passing from inlet
section 158 to outlet section 160 must pass through a common
section 162 between the outlets of downcomers 152a-152d and the
inlets of suction lines 156a-156c. Since all of the fluid must pass
through common section 162, in the event flow through one or more
of suction lines 156a-156c is reduced relative to the others,
suction flow will be decreased for all of the downcomers 152a-152d
substantially evenly. Header 150, suction lines 156a-156c, and
downcomers 152a-152d are thus configured and adapted to draw
substantially equal amounts of fluid from each of the downcomers
152a-152d even when flow is uneven among the suction lines
156a-156c during single or multiple pump operation. Flow rate can
be completely or partially reduced in a given pump due to a system
failure, or without any failure, for example if it is desired to
operate at a lower overall mass flow rate. The overall flow in such
events would decrease, but the balance of the flow would remain
substantially uniform along drum 116 and through downcomers
152a-152d. The problem of flow unbalance from losing one or more
pumps is eliminated, which means the boiler can continue operating
after loss of one or more pumps. This configuration also reduces or
eliminates ill effects from water level unbalance including metal
fatigue, overheating, boiler trips, and control issues.
[0033] The inner two downcomers 152b and 152c are inboard with
respect to the two outboard downcomers 152a and 152d. Each of the
inner downcomers 152b and 152c is connected to header 150 at a
first common axial position 164 on the header, i.e., downcomers
152b and 152c connect to header 150 at the same elevation along
axis A. Each of the outer downcomers 152a and 152d is connected to
header 150 at a second common axial position 166 on header, i.e.,
downcomers 152a and 152d connect to header 150 at a common
elevation along axis A, which is lower than where inner headers
152b and 152c connect to header 150, as oriented in FIG. 3.
[0034] With continued reference to FIG. 3, downcomers 152a-152d are
all oriented perpendicular to header 150 where connected thereto.
All of the downcomers 152a-152d are oriented parallel to one
another at inlet ends thereof, i.e., where they connect to drum
116. Similarly, suction lines 156a and 156c are oriented
perpendicular to header 150 where connected thereto, and are
parallel to one another at outlet ends thereof, i.e., where
connected to the respective pumps 154a and 154c. The third suction
line 156b is connected to header 150 in axial alignment therewith.
All of the suction lines 156a-156c and downcomers 152a-152d are
predominantly oriented parallel to circulation header 150 and
perpendicular to drum 116.
[0035] Referring now to FIG. 4, another exemplary embodiment of a
header system 200 constructed in accordance with the subject
invention is shown. Header system 200 includes drum 216,
downcomers, 252a, 252b, 252c, and 252d, circulation header 250 with
longitudinal axis B, inlet section 258, outlet section 260, common
section 262, pumps 254a and 254b similar to those described above
with respect to FIG. 3. Header system 200 has two pumps 254a and
254b connected to circulation header 250 by way of two respective
suction lines 256a and 256b. Rather than connecting to header 250
at a common elevation as do suction lines 156a and 156c in FIG. 3,
suction lines 256a and 256b are staggered axially with respect to
one another where connected to header 250. Since all the fluid must
be pumped through common portion 262, even if one of the two pumps
254a and 254b loses power or s otherwise diminished or reduced in
capacity or mass flow rate, flow through downcomers 252a-252d will
remain substantially equal, and fluid levels in drum 216 will
remain substantially even. Staggering inlets for suction lines 256a
and 256b provides advantages such as prevention of a false low
level alarm or low level trip, decreased carry-under, and increased
pump performance.
[0036] Referring again to FIGS. 1 and 3, steam generator 110 and
superheater 112 are each connected in fluid communication with
steam drum 116. Downcomers 152a-152d are connected to the bottom of
steam drum 116 where the fluid resides. Circulation header 150 is
vertically oriented within boiler 100, as are downcomers 152a-152d,
and suction lines 156a-156c. In this vertical header orientation,
the inlet section 158 of header 150 is above outlet section 160.
While described herein in the exemplary context of having a
vertically oriented circulation header, those skilled in the art
will readily appreciate that a circulation header can be oriented
horizontally, or in any other suitable orientation and still
achieve benefits, as long as the downcomers and suction lines
connect to the header in such a way as to provide substantially
even flow through the downcomers even when flow is unequal in the
suction lines.
[0037] With reference now to FIG. 5, steam generator 110 of boiler
100 is shown schematically. Substantially equal flow rates to each
solar receiver panel 104 of steam generator 110 are provided by the
system of cascaded headers fluidly connecting circulation header
150 (not shown in FIG. 5, but see FIG. 3) to steam generator
110.
[0038] The circulation pumps, e.g., circulation pumps 154a-154c and
254a-254b, feed into primary headers 168, as indicated in FIG. 5 by
the arrows pointing into each primary header 168. The exemplary
configuration shown in FIG. 5 has two lines feeding each primary
header 168, such as if two circulation pumps, e.g., 254a and 254b,
each have two discharge nozzles/lines, with each pump feeding one
line into each primary header 168. In the event of one pump losing
power, the remaining pump can still feed the entire steam generator
110 through both primary headers 168. Those skilled in the art will
readily appreciate that the number of pumps and/or lines feeding
primary headers 168 can be varied without departing from the spirit
and scope of the invention. For example, if three pumps are used,
such as pumps 154a-154c, each pump can have two feed lines, one to
each primary header 168 so each primary header 168 can be fed by
all three pumps.
[0039] Each primary header 168 has four outlet lines, each
connected to a respective secondary header 170, for a total of
eight secondary headers 170. Each secondary header 170 has eight
outlet lines, with two outlet lines feeding into each panel inlet
header 172. In FIG. 5, the components are all shown laid flat for
clarity. Dotted line C indicates where the feed lines between
secondary headers 170 and panel inlet headers 172 actually change
direction in the constructed boiler 100, starting downward from the
exits of headers 170, then bending upward at line C and continuing
upward into panel inlet headers 172. This arrangement causes the
flow through each panel to be in the upward direction. The benefits
of having all steam generator panels in an up-flow configuration is
described in greater detail in commonly owned, co-pending U.S.
patent application Ser. No. 12/547,650.
[0040] Having two lines feeding each panel inlet header 172 helps
provide even flow through the tubes of the panels 104. Each panel
104 feeds into a respective panel outlet header 174. In FIG. 5,
only one panel 104, one panel inlet header 172, and one panel
outlet header 174 are labeled with reference characters for sake of
clarity. Each panel outlet header 174 has two outlet lines that
feed into an intermediate outlet header 176. Each intermediate
outlet header 176 is fed by a pair of panels 104, and feeds into
steam drum 116 through a single feed line. Steam drum 116 is not
shown in FIG. 5, but the flow into drum 116 is indicated by arrows
pointing out of the intermediate outlet headers 176.
[0041] The plurality of cascaded headers 168, 170, and 172 define a
branching flow path that passes through a series of progressively
smaller headers from the supply (e.g., circulation header 150) to
panels 104 of steam generator 110. There are three header sizes and
three levels (168, 170, 172) between the source (e.g., circulation
header 150) and individual tubes of the panels 104 in steam
generator 110. On the outlet side of panels 104, a second plurality
of cascaded headers, i.e. headers 174 and 176, fluidly connect
steam generator 110 to steam drum 116 to provide a saturated
mixture of water and steam from steam generator 110 to steam drum
116. This second plurality of cascaded headers 174 and 176 defines
a flow path that passes through a series of progressively larger
headers from panels 104, through headers 174, into headers 176, and
then into steam drum 116. There are two header sizes and levels
between individual tubes of the panels 104 of steam generator 110
and steam drum 116. This arrangement of cascaded inlet and outlet
headers provides a substantially balanced flow to the individual
tubes of panels 104 in steam generator 110, since each header
provides mixing and balancing. With multiple levels of mixing,
balancing headers between relatively large components like
circulation header 150 and relatively small components like the
tubes of panels 104, there are multiple places for the working
fluid flow to mix and balance. Another benefit of having multiple
stages of headers is that it facilitates modularization during
boiler construction, maintenance, repairs, and the like. A cascaded
header configuration, with increased number of headers, allows for
the headers to be smaller and therefore the headers can have
thinner walls. Given that a solar boiler is typically cycled daily,
going from a hot state to a cold state, minimal wall thickness is
advantageous for reducing creep, fatigue, and high stresses.
[0042] While described herein in the exemplary context of having
three levels of cascading inlet headers and two levels of cascaded
outlet headers, those skilled in the art will readily appreciate
that any suitable number of header levels can be used on the inlet
and outlet sides of boiler panels. Moreover, any suitable number or
size of headers and feed lines can be used on any level of a
cascaded inlet or outlet header system without departing from the
spirit and scope of the invention. The systems and methods
described herein provide particular advantages when applied to
solar boilers, however those skilled in the art will readily
appreciate that the systems and methods described herein can be
applied to any other suitable type of boiler without departing from
the spirit and scope of the invention.
[0043] The methods and systems of the present invention, as
described above and shown in the drawings, provide for boilers, and
particularly solar boilers, with superior properties including
improved flow distribution in circulation components and receiver
panels. While the apparatus and methods of the subject invention
have been shown and described with reference to preferred
embodiments, those skilled in the art will readily appreciate that
changes and/or modifications may be made thereto without departing
from the spirit and scope of the subject invention.
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