U.S. patent application number 13/448909 was filed with the patent office on 2013-10-17 for retrofit for power generation system.
The applicant listed for this patent is Chandrashekhar Sonwane, Kenneth M. Sprouse. Invention is credited to Chandrashekhar Sonwane, Kenneth M. Sprouse.
Application Number | 20130269345 13/448909 |
Document ID | / |
Family ID | 49323837 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130269345 |
Kind Code |
A1 |
Sonwane; Chandrashekhar ; et
al. |
October 17, 2013 |
RETROFIT FOR POWER GENERATION SYSTEM
Abstract
A method of retrofitting a power generation system includes
modifying a pre-existing power generation system that includes a
combustor and a steam-based cycle to include a super-critical
carbon dioxide-based Brayton cycle that is directly coupled through
the combustor. The steam-based cycle is converted into a
steam-based Rankine cycle that is in thermal-receiving
communication with the super-critical carbon dioxide-based Brayton
cycle.
Inventors: |
Sonwane; Chandrashekhar;
(Canoga Park, CA) ; Sprouse; Kenneth M.; (Canoga
Park, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sonwane; Chandrashekhar
Sprouse; Kenneth M. |
Canoga Park
Canoga Park |
CA
CA |
US
US |
|
|
Family ID: |
49323837 |
Appl. No.: |
13/448909 |
Filed: |
April 17, 2012 |
Current U.S.
Class: |
60/645 ; 60/715;
60/716 |
Current CPC
Class: |
F01K 25/103 20130101;
F01K 23/10 20130101 |
Class at
Publication: |
60/645 ; 60/716;
60/715 |
International
Class: |
F01K 13/00 20060101
F01K013/00; F01K 11/02 20060101 F01K011/02; F01K 7/16 20060101
F01K007/16 |
Claims
1. A method of retrofitting a power generation system, the method
comprising: in a pre-existing power generation system including a
combustor and a steam-based cycle, modifying the pre-existing power
generation system to include a super-critical carbon dioxide-based
Brayton cycle that is directly coupled through the combustor; and
converting the steam-based cycle into a steam-based Rankine cycle
that is in thermal-receiving communication with the super-critical
carbon dioxide-based Brayton cycle.
2. The method as recited in claim 1, wherein: the super-critical
carbon dioxide-based Brayton cycle includes at least one turbine
and the steam-based cycle includes at least one turbine, and
mounting the at least one turbine of the super-critical carbon
dioxide-based Brayton cycle and the at least one turbine of the
steam-based cycle on a common shaft to drive a generator.
3. The method as recited in claim 1, wherein the modifying includes
providing superalloy tubes that extend through the combustor.
4. The method as recited in claim 3, including locating the
superalloy tubes through a first portion of the combustor that is
hotter than a second, different portion of the combustor through
which tubes of the steam-based cycle extended prior to the
modification.
5. The method as recited in claim 1, wherein the converting
includes removing tubes of the steam-based cycle from the
combustor.
6. The method as recited in claim 1, wherein the converting
includes connecting a heat exchanger in communication with the
super-critical carbon dioxide-based Brayton cycle and the
steam-based Rankine cycle.
7. The method as recited in claim 1, wherein the combustor is a
fluidized-bed reactor.
8. The method as recited in claim 7, including thermally coupling
the super-critical carbon dioxide-based Brayton cycle directly
through the fluidized-bed reactor.
9. A method of retrofitting a power generation system, the method
comprising: providing a pre-existing power generation system
comprising a combustor and a steam-based cycle, the steam-based
cycle including a first working fluid circuit extending through the
combustor and at least one turbine in fluid communication with the
first working fluid circuit, the at least one turbine being mounted
on a shaft that is coupled to drive a generator, the first working
fluid circuit and the at least one turbine defining a first maximum
operating temperature; replacing the first working fluid circuit
with a second working fluid circuit extending through the
combustor; and adding at least one additional turbine mounted on
the shaft, the at least one additional turbine being in fluid
communication with the second working fluid circuit and the at
least one turbine, the second working fluid circuit and the at
least one additional turbine defining a second maximum operating
temperature that is greater than the first maximum operating
temperature.
10. The method as recited in claim 9, wherein the adding of the at
least one additional turbine includes arranging the at least one
additional turbine upstream of the at least one turbine such that
the at least one turbine is in flow-receiving communication with
the at least one additional turbine.
11. The method as recited in claim 9, wherein the first working
fluid circuit includes steel tubes and the second working fluid
circuit includes superalloy tubes.
12. The method as recited in claim 9, wherein the at least one
additional turbine includes superalloy blades.
13. A retro-fitted power generation system comprising: a combustor;
a working fluid circuit extending through the combustor; at least
one pre-existing turbine having a first maximum operating
temperature; at least one retrofit turbine arranged in fluid
communication with the working fluid circuit and the at least one
pre-existing turbine, the at least one retrofit turbine having a
second, greater maximum operating temperature.
14. The system as recited in claim 13, wherein the combustor is
selected from the group consisting of a coal-fired boiler and a
fluidized bed reactor.
15. The system as recited in claim 13, wherein the working fluid
circuit includes superalloy tubes extending through the
combustor.
16. The system as recited in claim 13, wherein the at least one
pre-existing turbine includes steel and the retrofit turbine
includes a superalloy material.
17. The system as recited in claim 13, wherein the at least one
pre-existing turbine and the retrofit turbine are mounted on a
common shaft.
18. The system as recited in claim 13, wherein the at least one
retrofit turbine is arranged upstream of the at least one
pre-existing turbine such that the at least one pre-existing
turbine is in flow-receiving communication with the at least one
retrofit turbine.
Description
BACKGROUND
[0001] This disclosure relates to power plants for generating
electricity.
[0002] Existing coal-fired power plants that have been in operation
for many years, such as supercritical pulverized coal plants,
typically suffer from high carbon dioxide emissions. One approach
to reduce carbon dioxide emissions is to outfit an existing plant
with a post-combustion device, such as a chilled ammonia or
hindered amine device, to capture carbon dioxide from combustion
exhaust. Although such devices are effective in reducing net carbon
dioxide emissions, the devices typically debit overall plant
efficiency and thus increase levelized cost of energy.
[0003] More recently, there have been proposals to regulate carbon
dioxide emissions by capping emissions per unit of electricity
produced. Because post-combustion devices debit plant efficiency,
the carbon dioxide emissions per unit of generated electricity
increases. Therefore, existing plants are ill-equipped to meet such
regulations and are faced with the possibility of forced
retirement.
SUMMARY
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The various features and advantages of the present
disclosure will become apparent to those skilled in the art from
the following detailed description. The drawings that accompany the
detailed description can be briefly described as follows.
[0005] FIG. 1 is a schematic view of a pre-existing power
generation system.
[0006] FIG. 2 is a schematic view of a retrofit power generation
system based upon the pre-existing power generation system of FIG.
1.
[0007] FIG. 3 is a schematic view of another example retrofit power
generation system based upon the pre-existing power generation
system of FIG. 1.
[0008] FIG. 4 is a schematic view of another example pre-existing
power generation system.
[0009] FIG. 5 is a schematic view of a retrofit power generation
system based upon the pre-existing power generation system of FIG.
4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0010] FIG. 1 shows a schematic view of selected portions of a
pre-existing power generation system 20 ("system 20"). The term
"pre-existing" generally refers to the system 20 having been in
operation for its intended use for some period of time. As
disclosed herein, as an alternative to retiring the system 20, the
system 20 can be retrofitted with new, more efficient hardware,
while retaining at least some of the pre-existing hardware of the
system 20, to produce more power per unit of coal or fuel input. As
examples, a retrofit system as disclosed herein is expected to
achieve 5-10% increase in overall net thermal efficiency, 10-30%
lower carbon dioxide emissions, up to 25% reduction in levelized
cost of energy and the ability to meet proposed regulations with
regard to efficiency and emissions per unit of electricity
produced.
[0011] The system 20 includes a combustor 22, such as a coal-fired
boiler, which receives an input coal feed 24a and an input oxidant
feed 24b (e.g., air) that generate heat within the combustor 22. A
steam-based cycle 26 (power cycle) absorbs heat from the combustor
22 to generate electricity. The steam-based cycle 26 includes a
first turbine 28, a second turbine 30 and third turbine 32. The
turbines 28/30/32 are mounted on a shaft 34, which is coupled to
drive a generator 36. The third turbine 32 is in communication with
a condenser 38, which is connected in circuit to the combustor 22.
The combustor 22, turbines 28/30/32 and condenser 38 are connected
within a closed loop, working fluid circuit 40. For example, the
working fluid circuit 40 includes steel tubes that convey water,
steam or both between the combustor 22, turbines 28/30/32 and
condenser 38, as generally indicated by the arrows in the working
fluid circuit 40.
[0012] In operation, liquid water is discharged from the condenser
38 into the combustor 22. The combustor 22 generally operates in a
temperature regime of less than 700.degree. F./371.degree. C. and
pressure of less than 3000 pounds per square inch/20.5 megapascals
due to the limits of the materials of the working fluid circuit 40
and the turbines 28/30/32. The water absorbs heat within the
combustor 22 and turns to steam. The steam is then expanded over
the first turbine 28. The expanded steam from the first turbine 28
is circulated back through the combustor 22 for a reheat. The
reheated steam is then expanded over the second turbine 30 and then
the third turbine 32. The expanded steam from the third turbine 32
is condensed in the condenser 38 prior to circulation into the
combustor 22 for another thermodynamic cycle.
[0013] In this example, the system 20 utilizes relatively
inefficient technology. For example, the tubes of the working fluid
circuit 40 and components of the turbines 28/30/32 are made of
steel. In that regard, the working fluid circuit 40 and turbines
28/30/32 have a maximum operating temperature to which the
materials of these components can be exposed. For example, the
temperature in the combustor 22 is controlled using a water quench
or the like to ensure that actual operating temperatures of the
steam do not exceed the maximum operating temperature limit of the
materials of the working fluid circuit 40 and the turbines
28/30/32. Overall, the operating efficiency of the system 20 is
limited by the maximum allowed temperature in the combustor 22 and
steam-based cycle 26. Thus, even if carbon dioxide is captured from
an exhaust 42 of the combustor 22, the system 20 as-is has only
limited ability to improve carbon dioxide emissions per unit of
generated electricity and levelized cost of energy.
[0014] As will be appreciated from FIG. 2, the system 20 of FIG. 1
has been retrofitted with efficiency enhancements to produce a
retrofitted power generation system 20' (retrofit system 20'). In
this disclosure, the term "retrofit" or variations thereof may be
used to refer to an individual hardware component or to a system,
for example. When used with reference to an individual hardware
component for use in a system, the term indicates that the
component was not part of the operable initial or prior system and
is not a mere replacement in kind of a like component of the
operable initial or prior system. When used with reference to a
system, the term indicates that the system includes at least some
pre-existing hardware components and at least one added hardware
component that was not part of the operable initial or prior system
and is not a mere replacement in kind of a like component of the
operable initial or prior system. The modifying terms
"pre-existing" and "retrofit" as used herein thus indicate a
physical distinction between components and/or systems.
[0015] In this example, the retrofit system 20' utilizes a portion
of the pre-existing hardware of the system 20, including the
pre-existing combustor 22, the pre-existing turbines 28/30/32 and
the pre-existing condenser 38. However, the working fluid circuit
40 is replaced with a second (retrofit) working fluid circuit 50
that is directly coupled through the combustor 22 and the retrofit
system 20' includes at least one additional, retrofit turbine 52
mounted on the shaft 34. Although only one retrofit turbine 52 is
shown, it is to be understood that additional retrofit turbines 52
could be used.
[0016] In the retrofit system 20', the retrofit turbine 52, the
combustor 22, the turbines 28/30/32 and condenser 38 are connected
within the second working fluid circuit 50. For example, the second
working fluid circuit 50 includes superalloy tubes that convey
water, steam or both between the combustor 22, retrofit turbine 52,
turbines 28/30/32 and the condenser 38, as generally indicated by
the arrows in the second working fluid circuit 50. A "superalloy"
as used herein refers to a nickel-based, cobalt-based or
nickel-iron-based alloy.
[0017] In operation, liquid water is discharged from the condenser
38 into the combustor 22. The water absorbs heat within the
combustor 22 and turns to steam. The steam is then expanded over
the retrofit turbine 52. The expanded steam from the retrofit
turbine 52 is then serially expanded over the first turbine 28, the
second turbine 30 and the third turbine 32. The expanded steam from
the third turbine 32 is then condensed in the condenser 38 prior to
being circulated to the combustor 22 for another thermodynamic
cycle.
[0018] The retrofit system 20' has enhanced efficiency in
comparison with the system 20 with regard to carbon dioxide
emissions per unit of electricity generated. For example, the tubes
of the second working fluid circuit 50 and components of the
retrofit turbine 52 are made of superalloy materials. In that
regard, the second working fluid circuit 50 and retrofit turbine 52
have a second maximum operating temperature that is greater than
the maximum operating temperature of the prior working fluid
circuit 40 and turbines 28/30/32 that include steel or other lower
melting point materials. The second working fluid circuit 50 can
thus be routed through a hotter portion 22a of the combustor 22
than the prior working fluid circuit 40, or the combustor 22 can be
operated at a higher temperature to generate higher temperature
steam. For example, the combustor 22 operates in a temperature
regime of up to 1300.degree. F./705.degree. C. and pressure of up
to 6000 pounds per square inch/41 megapascals. Once the higher
temperature steam is expanded over the retrofit turbine 52, the
steam cools to a temperature that is within the maximum operating
temperature of the turbines 28/30/32. Thus, the retrofit system 20'
can be operated at higher, more efficient temperatures to improve
carbon dioxide emissions per unit of generated electricity and to
reduce levelized cost of energy.
[0019] As will be appreciated from another example of a retrofit in
FIG. 3, the system 20 of FIG. 1 is retrofitted with efficiency
enhancements to produce a retrofitted power generation system 20''
(retrofit system 20''). In this example, the system 20 has been
retrofitted with a super-critical carbon dioxide-based Brayton
cycle 54 to enhance efficiency. The retrofit system 20'' utilizes a
portion of the pre-existing hardware of the system 20, including
the pre-existing combustor 22, pre-existing turbine 32 and
pre-existing condenser 38, The working fluid circuit 40 is replaced
with a second (retrofit) working fluid circuit 50' that extends
through the combustor 22. The retrofit system 20'' also includes at
least one additional, retrofit turbine 52' mounted on the shaft
34.
[0020] The super-critical carbon dioxide-based Brayton cycle 54 is
thermally coupled through the combustor 22 and the prior
steam-based cycle 26 is converted to a steam-based Rankine cycle
26' that is in thermal-receiving communication with the
super-critical carbon dioxide-based Brayton cycle 54.
[0021] As an example of the retrofit, the prior steel tubes of the
working fluid circuit 40 are removed, including removal from the
combustor 22. Superalloy tubes of the second working fluid circuit
50' are added and are directly coupled through the combustor 22,
The addition of the super-critical carbon dioxide-based Brayton
cycle 54 includes adding a retrofit compressor 56, a retrofit first
turbine 58 and a retrofit second turbine 60. The prior steam-based
cycle 26 is modified to add a retrofit heat exchanger 62 for
thermal communication between the super-critical carbon
dioxide-based Brayton cycle 54 and the steam-based Rankine cycle
26'. The retrofit compressor 56, the retrofit first turbine 58, the
retrofit second turbine 60 and the pre-existing turbine 32 are
mounted on the common shaft 34 to drive the generator 36. The
retrofit first turbine 58 and the retrofit second turbine 60 each
includes a rotor having a disk 66 and a plurality of blades 68
mounted on the disk 66.
[0022] In operation, a working fluid, such as carbon dioxide or a
carbon dioxide-containing mixture (e.g., with helium), in the
second working fluid circuit 50' absorbs heat within the combustor
22 and is then expanded over the retrofit first turbine 58. The
expanded working fluid is then circulated back into the combustor
22 for a reheat. The reheated working fluid is then expanded over
the retrofit second turbine 60 and then circulated to the retrofit
heat exchanger 62. The working fluid in the retrofit heat exchanger
62 heats water within the steam-based Rankine cycle 26'. The
working fluid is then pressurized in the retrofit compressor 56
prior to circulating to the combustor 22 for another thermodynamic
cycle. The heated steam from the heat exchanger 62 expands over the
pre-existing turbine 32 and then circulates to the condenser 38 for
another thermodynamic cycle.
[0023] The retrofit system 20'' has enhanced efficiency in
comparison with the system 20 with regard to carbon dioxide
emissions per unit of electricity generated. For example, the tubes
of the second working fluid circuit 50' and the disks 66 and blades
68 of the retrofit turbines 58/60 are made of superalloy materials.
In that regard, the second working fluid circuit 50' and retrofit
turbines 58/60 have a second maximum operating temperature that is
greater than the maximum operating temperature of the prior working
fluid circuit 40 and turbines 28/30/32 that include steel
materials. The second working fluid circuit 50' can thus be routed
through a hotter portion 22a of the combustor 22 than the prior
working fluid circuit 40, or the combustor 22 can be operated at a
higher temperature to generate higher temperature working fluid.
For example, the combustor 22 operates in a temperature regime of
up to 1300.degree. F./705.degree. C. and pressure of up to 6000
pounds per square inch/41 megapascals. Thus, the retrofit system
20'' can be operated at higher, more efficient temperatures to
improve carbon dioxide emissions per unit of generated electricity
and to reduce levelized cost of energy.
[0024] FIG. 4 illustrates another example pre-existing power
generation system 120. In this example, the pre-existing power
generation system 120 includes a combustor 1 which in this example
is a fluidized bed reactor that receives a coal feed 124 and an
adsorbent feed 125, such as limestone, which facilitates the
reaction within a fluidized bed 122a. Alternatively, the combustor
122 can be a coal-fired boiler that is then replaced with a
retrofit fluidized bed reactor, coal feed 124 and adsorbent feed
125.
[0025] A steam--based cycle 126 absorbs heat from the combustor 122
to generate electricity. The steam-based cycle 126 includes a heat
exchanger 170 and a turbine 132 that is mounted on a shaft 134. The
turbine 132 is coupled through the shaft 134 to drive a generator
136. The heat exchanger 170 is in communication with circuit 140,
which receives a hot exhaust stream from the combustor 122 as
generally indicated by the arrows in the circuit 140. Similar to
the system 20, in the system 120 the tubes of the circuit 140 and
components of the turbine 132 are made of steel and have a maximum
operating temperature.
[0026] In operation, the combustor 122 produces a hot exhaust
stream that is discharged through circuit 140 to the heat exchanger
170. The hot exhaust stream heats water in the heat exchanger 170
to produce steam. The hot exhaust stream may then be recycled
downstream from the heat exchanger 170 such that at least a portion
of the product stream, such as carbon dioxide, is fed back into the
combustor 122. The steam in the steam-based cycle 126 expands over
the turbine 132 to drive the generator 136.
[0027] As will be appreciated from FIG. 5, the system 120 of FIG. 4
has been retrofit with efficiency enhancements to produce a
retrofitted power generation system 120' (retrofit system 120'). In
this example, the retrofit system 120' has been retrofitted with a
super-critical carbon dioxide-based Brayton cycle 154 to enhance
efficiency. The retrofit system 120 utilizes a portion of the
pre-existing hardware of the system 120, including the pre-existing
turbine 132 and pre-existing heat exchanger 170. A second
(retrofit) working fluid circuit 150' that extends through the
combustor 122 is added. The retrofit system 120'' also includes at
least one additional, retrofit turbine 152 mounted on the shaft
134.
[0028] The super-critical carbon dioxide-based Brayton cycle 154 is
thermally coupled through the combustor 122 and the prior
steam-based cycle 126 is converted to a steam-based Rankine cycle
126' that is in thermal-receiving communication with the
super-critical carbon dioxide-based Brayton cycle 154.
[0029] As an example of the retrofit, superalloy tubes of the
second working fluid circuit 150' are added and are directly
coupled through the combustor 122. The addition of the
super-critical carbon dioxide-based Brayton cycle 154 includes
adding a retrofit compressor 156, a retrofit first turbine 158 and
a retrofit second turbine 160. The prior steam--based cycle 126 is
modified to add a retrofit heat exchanger 162 for thermal
communication between the super-critical carbon dioxide-based
Brayton cycle 154 and the steam-based Rankine cycle 126. The
retrofit compressor 156, the retrofit first turbine 158, the
retrofit second turbine 160 and the pre-existing turbine 132 are
mounted on the common shaft 134 to drive the generator 136. The
retrofit first turbine 158 and the retrofit second turbine 160 each
includes a rotor having a disk 166 and a plurality of blades 168
mounted on the disk 166.
[0030] In operation, a working fluid, such as carbon dioxide or a
carbon dioxide-containing mixture (e.g., with helium), in the
second working fluid circuit 150' absorbs heat within the
fluidized-bed 122a and is then expanded over the retrofit first
turbine 158. The expanded working fluid is then circulated back
into the combustor 122 for a reheat. The reheated working fluid
expands over the retrofit second turbine 160 and then circulates to
the retrofit heat exchanger 162. The working fluid in the retrofit
heat exchanger 162 heats water within the steam-based Rankine cycle
126'. The working fluid is then pressurized in the retrofit
compressor 156 prior to circulating to the combustor 122 for
another thermodynamic cycle. The heated steam from the heat
exchanger 162 expands over the pre-existing turbine 132 and then
circulates to a condenser 138 for another thermodynamic cycle.
[0031] The retrofit system 120' has enhanced efficiency in
comparison with the system 120 with regard to carbon dioxide
emissions per unit of electricity generated. For example, the tubes
of the second working fluid circuit 150' and the disks 166 and
blades 168 of the retrofit turbines 158/160 are made of superalloy
materials. Thus, the second working fluid circuit 150' and retrofit
turbines 158/160 have a second maximum operating temperature that
is greater than the maximum operating temperature of the circuit
140 and turbine 132 that include steel materials. The second
working fluid circuit 150' can thus be routed through the
fluidized-bed 122a, or the combustor 122 can be operated at a
higher temperature. For example, the combustor 122 operates in a
temperature regime of up to 1300.degree. F./705.degree. C. and
pressure of up to 6000 pounds per square inch/41 megapascals. Thus,
the retrofit system 120' can be operated more efficiently to
improve carbon dioxide emissions per unit of generated electricity
and to reduce levelized cost of energy.
[0032] Although a combination of features is shown in the
illustrated examples, not all of them need to be combined to
realize the benefits of various embodiments of this disclosure. In
other words, a system designed according to an embodiment of this
disclosure will not necessarily include all of the features shown
in any one of the Figures or all of the portions schematically
shown in the Figures. Moreover, selected features of one example
embodiment may be combined with selected features of other example
embodiments.
[0033] The preceding description is exemplary rather than limiting
in nature. Variations and modifications to the disclosed examples
may become apparent to those skilled in the art that do not
necessarily depart from the essence of this disclosure. The scope
of legal protection given to this disclosure can only be determined
by studying the following claims.
* * * * *