U.S. patent application number 13/407354 was filed with the patent office on 2013-08-29 for dual chemistry steam drum.
This patent application is currently assigned to HRST, INC.. The applicant listed for this patent is Robert James Krowech. Invention is credited to Robert James Krowech.
Application Number | 20130220238 13/407354 |
Document ID | / |
Family ID | 49001472 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130220238 |
Kind Code |
A1 |
Krowech; Robert James |
August 29, 2013 |
Dual Chemistry Steam Drum
Abstract
A partitioned drum for a heat recovery steam generator
comprising a first chamber and a second chamber. The first chamber
has a chemical inlet for chemically treating a flow medium, at
least one inlet for the flow medium and at least one outlet for the
flow medium. The second chamber has one inlet for the flow medium
and at least one outlet for the flow medium. The flow medium
present in the first chamber is treated with a chemical to prevent
flow assisted corrosion, while the flow medium present in the
second chamber is available as a source of fluid for the boiler
feed pump.
Inventors: |
Krowech; Robert James; (Eden
Prairie, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Krowech; Robert James |
Eden Prairie |
MN |
US |
|
|
Assignee: |
HRST, INC.
Eden Prairie
MN
|
Family ID: |
49001472 |
Appl. No.: |
13/407354 |
Filed: |
February 28, 2012 |
Current U.S.
Class: |
122/491 |
Current CPC
Class: |
F22B 37/22 20130101;
F01K 23/106 20130101 |
Class at
Publication: |
122/491 |
International
Class: |
F22B 37/26 20060101
F22B037/26 |
Claims
1. A partitioned steam drum for a heat recovery steam generator
comprising: a first chamber in fluid communication with a chemical
source for treating a flow medium, the first chamber having at
least one outlet for the flow medium; a second chamber in fluid
communication with a flow medium source and in fluid communication
with the first chamber, wherein the flow medium is conveyed from
the flow medium source through the second chamber to the first
chamber.
2. The partitioned drum of claim 1, wherein a non-volatile chemical
from the chemical source is added to the flow medium in the first
chamber.
3. The partitioned drum of claim 2, wherein the non-volatile
chemical comprises phosphates.
4. The partitioned drum of claim 1, wherein an inlet of the second
chamber is connected to an economizer of the heat recovery steam
generator.
5. The partitioned drum of claim 1, wherein at least one outlet of
the second chamber is connected to a boiler feed pump of the heat
recovery steam generator.
6. The partitioned drum of claim 1, wherein the first chamber is
defined by a first body and the second chamber is defined by a
second body.
7. The partitioned drum of claim 6, wherein the second body is
disposed within the first chamber.
8. The partitioned drum of claim 6, wherein the first body is
disposed within the second chamber.
9. A heat recovery steam generator comprising: a low pressure
section comprising a low pressure evaporator, a low pressure drum,
and a low pressure superheater; and a high pressure section
comprising a high pressure economizer, a high pressure evaporator,
a high pressure drum, and a high pressure superheater, wherein the
low pressure drum is a partitioned drum having a first chamber and
a second chamber.
10. The heat recovery steam generator of claim 9, wherein the low
pressure drum has a chemical inlet that conveys a chemical to one
of the first chamber and the second chamber.
11. The heat recovery steam generator of claim 9, wherein the low
pressure drum comprises a first body having an inner surface
defining the first chamber; a second body disposed within the first
chamber, the second body defining the second chamber.
12. The heat recovery steam generator of claim 9, further
comprising: at least one intermediate pressure section, the at
least one intermediate pressure section comprising an intermediate
pressure economize, an intermediate pressure evaporator, an
intermediate pressure drum, and an intermediate pressure
superheater.
13. A partitioned drum for a heat recovery steam generator
comprising: a first body having an inner surface defining a first
chamber; the first body having a flow medium outlet and a chemical
inlet for chemically treating the flow medium within the first
chamber; a second body disposed within the first chamber, the
second body defining a second chamber; the second body having a
flow medium inlet, a first outlet connected to a boiler pressure
pump of the heat recovery steam generator, and a second outlet
connected to the first chamber for transferring a flow medium from
the second chamber to the first chamber.
14. The partitioned drum of claim 13, wherein a non-volatile
chemical from the chemical source is added to the flow medium in
the first chamber.
15. The partitioned drum of claim 14, wherein the non-volatile
chemical comprises phosphates.
16. The partitioned drum of claim 13, wherein the flow medium inlet
of the second body is connected to an economizer of the heat
recovery steam generator.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] None.
BACKGROUND OF THE INVENTION
[0002] Heat recovery steam generators are well known in the power
generation industry as an efficient means of electricity
production. Hot exhaust gas from gas turbines is inputted into the
heat recovery steam generator, along with a flow medium such as
water, to create steam to drive a steam turbine or for process use.
Heat recovery steam generators can be single pressure units, where
water is converted to steam at a single pressure range, or multiple
pressure units, where water is converted to steam at least at a low
pressure range and a high pressure range.
[0003] Heat recovery steam generators generally comprise an
economizer, an evaporator with a steam drum, and a superheater. The
economizer heats a flow medium, such as water, using heat from the
gas turbine. The flow medium is then transferred to the evaporator
and steam drum where it forms steam. Once the steam reaches the
superheater, it is heated to convert the saturated steam into
superheated steam. In steam generators with multiple sections,
often times the low pressure steam drum is used as a storage tank
for the suction of a high pressure boiler feed pump. The water is
taken from the low pressure drum and pumped to the economizer of
the higher pressure sections of the heat recovery steam
generator.
[0004] One consideration in the design of steam generators is
flow-accelerated (or flow-assisted) corrosion. Flow-accelerated
corrosion occurs when a fluid (such as water or a steam water
dual-phase mixture) passing through a portion of the steam
generator causes a protective layer of oxide on a metal surface to
dissolve. The metal corrodes, which creates a new oxide layer. As
more water passes through the portion of the steam generator, the
corrosive cycle continues, resulting in additional metal loss.
Flow-accelerated corrosion is dependent upon pH levels, oxygen
levels, phase of the fluid (water or steam water mixtures are
susceptible), and the velocity and turbulence of the fluid flow
(therefore making it dependent on geometry of tubes and pipes). To
reduce flow-accelerated corrosion, chemicals are used to increase
the pH level of the fluid entering the low pressure steam drum of
the low pressure unit. Volatile chemicals are carried away with the
low pressure steam and do not remain in the water of the low
pressure drum. This is critical when the low pressure drum is used
for suction to the higher pressure units and the associated
attemperator water supply as water cannot be treated with solids
when the water is used as feedwater for the higher pressure
units.
[0005] In some heat recovery steam generators, feedwater flows to
the boiler feed pump in one of two ways. The feedwater can flow
from the economizer to the boiler feed pump directly or from the
low pressure steam drum to the boiler feed pump. Where the
feedwater flows from the economizer to the boiler feed pump, there
is no reserve water supply for the boiler feed pump in the event it
has a fault of any kind. Where the feedwater flows from the steam
drum to the boiler feed pump, the water used for steam generation
must be treated with volatile chemicals. However, water treated
with these volatile chemicals increases flow accelerated corrosion
in the evaporator because it flashes off with the low pressure
steam leaving the water phase of the mixture in the steam drum with
low pH. Further aggravating the issue of flow accelerated corrosion
in the low pressure steam section is temperature. The low pressure
evaporator, which also takes its supply water from the low pressure
steam drum is in the temperature range of greatest susceptibility
for flow accelerated corrosion. Therefore the need is to protect
the low pressure evaporator pressure components from flow
accelerated wear while keeping non-volatile chemistry out of the
feedwater to the higher pressure feed water pump suction.
[0006] All US patents and applications and all other published
documents mentioned anywhere in this application are incorporated
herein by reference in their entirety.
[0007] Without limiting the scope of the invention, a brief summary
of some of the claimed embodiments of the invention is set forth
below. Additional details of the summarized embodiments of the
invention and/or additional embodiments of the invention may be
found in the Detailed Description of the Invention below.
[0008] A brief abstract of the technical disclosure in the
specification is also provided for the purposes of complying with
37 C.F.R. .sctn.1.72. The abstract is not intended to be used for
interpreting the scope of the claims.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention provides a partitioned drum, which
serves as a reservoir in the event of a failure of the water
supply. In the event of such a failure, the higher pressure boiler
feed pump is supplied with water for a given retention time, which
is commonly calculated to be between about two and five
minutes.
[0010] A partitioned drum for a heat recovery steam generator
comprises a first chamber in fluid communication with a chemical
source for treating a flow medium and a second chamber in fluid
communication with both a flow medium source and the first chamber.
The first chamber has at least one outlet for the flow medium. The
flow medium is conveyed from the flow medium source through the
second chamber of the partitioned drum to the first chamber of the
partitioned drum. In at least one embodiment, a non-volatile
chemical from the chemical source is added only to the flow medium
in the first chamber. Thus, the non-volatile chemical is not added
to the flow medium present in the second chamber. Prior to the flow
medium entering the second chamber, the flow medium is treated with
a volatile chemical, which are carried away with the low pressure
steam and do not remain in the water of the low pressure drum.
Throughout the rest of the application, the flow medium present in
the second chamber will be referred to as "untreated" because the
non-volatile chemical is not added to the flow medium present in
the second chamber, and in at least one embodiment, the
non-volatile chemical is only added to the flow medium present in
the first chamber. In other words, the non-volatile chemical source
is only in communication with the first chamber, not the second
chamber.
[0011] The chemical used to treat the flow medium in the first
chamber may be selected from the group consisting of phosphates and
other solid, non-volatile chemicals. In one embodiment, the first
outlet of the second chamber is connected to a boiler feed pump of
the heat recovery steam generator. A second outlet of the second
chamber can be in communication with the first chamber for
transferring an untreated flow medium from the second chamber to
the first chamber. In one embodiment, the partitioned drum is used
in a low pressure section of the heat recovery steam generator.
[0012] In one embodiment, the partitioned drum comprises a first
body having an inner surface defining the first chamber and a
second body disposed within the first chamber. The second body has
an inner surface that defines the second chamber.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0013] FIG. 1 shows a schematic view of a typical heat recovery
steam generator.
[0014] FIG. 2 shows an isometric view of a steam drum of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] While this invention may be embodied in many different
forms, there are described in detail herein specific preferred
embodiments of the invention. This description is an
exemplification of the principles of the invention and is not
intended to limit the invention to the particular embodiments
illustrated.
[0016] For the purposes of this disclosure, like reference numerals
in the figures shall refer to like features unless otherwise
indicated.
[0017] FIG. 1 shows a heat recovery steam generator 10 with a low
pressure section 20, an intermediate pressure section 30, and a
high pressure section 40. Heat recovery steam generators can have
just a single pressure section. They can also have simply two
units, a low pressure section 20 and a high pressure section 40.
Although FIG. 1 shows an example of a heat recovery steam generator
with a three pressure sections 20, 30, 40, additional intermediate
pressure sections can be used. Other configurations of heat
recovery steam generators may be used with the partitioned steam
drum of the present invention.
[0018] As shown in FIG. 1, the low pressure section 20 comprises a
low pressure economizer 22, a low pressure steam drum 24, a low
pressure evaporator 26, and a low pressure superheater 28. The low
pressure section 20 may or may not include the low pressure
economizer 22. As shown in FIG. 1, the intermediate pressure
section 30 comprises an intermediate pressure economizer 32, an
intermediate pressure steam drum 34, an intermediate pressure
evaporator 36, and an intermediate pressure superheater 38. As
shown in FIG. 1, the high pressure section 40 comprises a high
pressure economizer 42, a high pressure steam drum 44, a high
pressure evaporator 46, and a high pressure superheater 48.
[0019] In operation, a flow medium (such as water) provided by tank
50 enters either the drum 24 or the low pressure economizer 22
where exhaust heat from a gas turbine (not shown) is used to heat
up the flow medium. The flow medium is then transferred to the low
pressure steam drum 24 and the low pressure evaporator 26, where
the absorbed heat causes the flow medium to evaporate into a steam.
This steam is then superheated in the low pressure superheater 28.
The steam exits the low pressure superheater to drive a low
pressure turbine 70, to use in other processes, or for release from
the system.
[0020] Some of the heated flow medium from the steam drum 24 is
transferred to the boiler feed pump 60 where it is pumped to the
intermediate pressure economizer 32 and to the high pressure
economizer 42. The heated flow medium goes through the intermediate
pressure economizer 32 and then is transferred to the intermediate
pressure steam drum 34 and the intermediate pressure evaporator 36
to form steam. This steam is then superheated in the intermediate
pressure superheater 38. Likewise, in the high pressure section 40,
the heated flow medium from the boiler feed pump 60 goes through
the high pressure economizer 42 and then is transferred to the high
pressure steam drum 44 and the high pressure evaporator 46 to form
steam. This steam is then superheated in the high pressure
superheater 48. Steam exiting the intermediate pressure superheater
38 and the high pressure superheater 48 drive the intermediate
pressure turbine 80 and the high pressure turbine 90, respectively.
Alternatively, the steam is used in other processes or for release
from the system.
[0021] FIG. 2 shows a steam drum 100 of the present invention. The
steam drum 100 is preferably used as the low pressure steam drum,
because the low pressure section is most susceptible to flow
accelerated corrosion given the water flow velocity, water
temperature, pH level and oxygen level. The low pressure section is
also the pressure level used for higher pressure feed pump
suction.
[0022] Steam drum 100 is a partitioned steam drum having two
chambers 102, and 104. In some embodiments, steam drum 100 is
preferably a cylindrical body having an inner surface and a wall
contacting a portion of the inner surface to separate chamber 102
and 104. In at least one embodiment, the wall has the same
circumference as the cylindrical body. The wall may be joined to
the cylindrical body by a weld or another permanent or releasable
affixation mechanism that effectively seals, blocks or otherwise
prevents fluid from being transferred between the second chamber
104 and the first chamber 102 at the joint of the wall and the
cylindrical body. In other embodiments, such as the embodiment
shown in FIG. 2, the first chamber 102 is defined by the inner
surface of cylindrical body 106 and the second chamber 104 is
defined by the inner surface of a second body 108, the second body
108 being disposed within the first chamber 102. In at least one
embodiment, the first chamber 102 has a greater water capacity than
the second chamber 104. In other embodiments, the second chamber
104 has a greater water capacity than the first chamber 102.
[0023] By separating steam drum 100 into two separate chambers 102,
104, water in chamber 102 can be treated with non-volatile
chemicals from a chemical source, while water in chamber 104
receives no additional treatment from the chemical source. The
water in chamber 104 can be used as feedwater for the boiler feed
pump, or when necessary can flow to or be transferred to chamber
102 as supply demands.
[0024] In at least one embodiment, the first chamber 102 is in
fluid communication with a chemical fluid source (not shown), the
superheater 28, the second chamber 104, and the evaporator 26. The
first chamber 102 only receives the flow medium from the second
chamber 104. Steam can exit from the first chamber 102 to the
superheater 28, and the flow medium can exit from the first chamber
102 to the evaporator 26. In at least one embodiment, the second
chamber 104 is in fluid communication with the economizer 22, the
first chamber 102, and the boiler feed pump 60. Flow medium enters
the second chamber 104 from the economizer 22. The flow medium can
exit the second chamber 104 either to the boiler feed pump 60 or
the first chamber 102. Thus, the first chamber 102 only receives
flow medium from the economizer through a connection to the second
chamber 104, rather than directly, and the first chamber 102 and
the boiler feed pump 60 are not connected. This prevents flow
medium treated with the non-volatile chemicals from being used in
the boiler feed pump 60.
[0025] FIG. 2 shows a particular configuration of the first chamber
102 and the second chamber 104. As shown in FIG. 2, the first
chamber 102 is defined by the inner surface of a first body 106 and
the second chamber 104 is defined by the inner surface of a second
body 108, where the second body 108 is disposed within the first
body 106. As shown in the figures, each of these bodies is
cylindrical, but they may have other shapes or configurations. In
the embodiment shown, the first body 106 has an outlet 110 for
steam to exit from the first chamber 102 to the low pressure
superheater 28. In the embodiment shown in FIG. 2, the first body
106 has an opening 112 for a conduit that conveys the flow medium,
such as water, from the economizer 28 directly to the second
chamber 104 at inlet 114. In one embodiment, the first body 106
also has at least one opening 115 for a conduit that conveys a flow
medium to the first chamber 102 from the low pressure evaporator
26. In at least the embodiment shown in FIG. 2, the first body 106
has at least one outlet 122 to supply flow medium to the low
pressure evaporator 26 or other components of the system. As shown,
the second body 108 has an outlet 116 for transferring the flow
medium from the second chamber 104 to the boiler feed pump 60
(shown generally by the valve assembly at 120) and an outlet 118
for transferring the flow medium from the second chamber 104 to at
least the first chamber 102.
[0026] In at least the embodiment shown in FIG. 2, the first body
106 has a chemical inlet 130 for conveying chemicals comprising
phosphates and other non-volatile chemicals to the flow medium in
the first chamber 102. Any flow medium present in the first chamber
102 is separated from the second chamber 104 so that the flow
medium in the second chamber remains untreated. Untreated flow
medium from second chamber 104 can be transferred to the first
chamber 102 or to the boiler feed pump 60. Thus, the untreated
water in the second chamber 104 can be used as feedwater for the
boiler feed pump 60, or when necessary can be transferred to the
first chamber 102 as supply demands.
[0027] In at least one embodiment, the partitioned drum 100 serves
as a reservoir like a conventional drum in the event of a failure
of the water supply to the drum 100. In the event of a critical
failure of water supply to the partitioned drum 100, when the
second chamber 104 lacks the requisite flow medium for the boiler
feed pump, a pressure change causes the flow to reverse in the
connection shown at 118. The flow medium from the first chamber 102
is transferred, conveyed or otherwise flows into at least the
second chamber 104. It should be noted that this fluid from chamber
102 may be treated with the non-volatile chemicals. Thus, in
emergencies, the feed pump 60 is supplied with water treated with
non-volatiles for the retention time of between about two and five
minutes, allowing time for a controlled shut down or recovery of
the feedwater source.
[0028] Although the above disclosure describes a steam drum where
the first chamber 102, which is defined by first body 106 has
treated water and the second chamber 104, which is defined by a
second body 108 disposed within the first chamber 102, has
untreated water, the invention also contemplates embodiments where
the first chamber 102 is for untreated water and the second chamber
104 is for treated water. In such an embodiment, the first body 106
has at least one outlet for transferring untreated water from the
first chamber 102 to at least one of the boiler feed pump 60 and
the second chamber 104. The second body 108 has an outlet for steam
from the second chamber 104, an inlet for conveying untreated water
from the first chamber 102 to the second chamber 104. In one
embodiment, the second body 108 also has a chemical inlet for
conveying chemicals to the second chamber 104. Any treated water
present in the second chamber 104 is separated from the untreated
water in the first chamber 102 so that the water in the second
chamber 104 remains untreated.
[0029] The above disclosure is intended to be illustrative and not
exhaustive. This description will suggest many variations and
alternatives to one of ordinary skill in this art. All these
alternatives and variations are intended to be included within the
scope of the claims where the term "comprising" means "including,
but not limited to". Those familiar with the art may recognize
other equivalents to the specific embodiments described herein
which equivalents are also intended to be encompassed by the
claims.
[0030] Further, the particular features presented in the dependent
claims can be combined with each other in other manners within the
scope of the invention such that the invention should be recognized
as also specifically directed to other embodiments having any other
possible combination of the features of the dependent claims. For
instance, for purposes of claim publication, any dependent claim
which follows should be taken as alternatively written in a
multiple dependent form from all prior claims which possess all
antecedents referenced in such dependent claim if such multiple
dependent format is an accepted format within the jurisdiction. In
jurisdictions where multiple dependent claim formats are
restricted, the dependent claims should each be also taken as
alternatively written in each singly dependent claim format which
creates a dependency from a prior antecedent-possessing claim other
than the specific claim listed in such dependent claim below.
[0031] This completes the description of the preferred and
alternate embodiments of the invention. Those skilled in the art
may recognize other equivalents to the specific embodiment
described herein which equivalents are intended to be encompassed
by the claims attached hereto.
* * * * *