U.S. patent application number 12/412359 was filed with the patent office on 2009-10-01 for increasing power of steam plant with refrigerant cooled condenser at peak loads by using cooling thermal storage.
Invention is credited to Ahmed Sabry Hegazy.
Application Number | 20090241546 12/412359 |
Document ID | / |
Family ID | 41115070 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090241546 |
Kind Code |
A1 |
Hegazy; Ahmed Sabry |
October 1, 2009 |
Increasing power of steam plant with refrigerant cooled condenser
at peak loads by using cooling thermal storage
Abstract
A steam powered power plant and method of cooling a steam
powered plant. A boiler provides steam to turbine and the turbine
drives a generator to produce power. Exhaust steam from the turbine
is cooled in a condenser and returns to the boiler. A first dry
refrigeration cycle uses a first compressor to compress a first
flow of refrigerant and the compressed flow of refrigerant rejects
heat to the surrounding through an air cooled condenser and is then
expanded in the steam condenser to cool the exhaust steam. A second
refrigeration cycle includes a second compressor used to compress a
second flow of refrigerant and the second flow of refrigerant is
cooled in an air cooled condenser and is expanded to cool water in
a storage tank wherein the stored water can be used to cool the
condenser and exhaust steam during a peak load condition of the
power plant.
Inventors: |
Hegazy; Ahmed Sabry;
(Alexandria, SA) |
Correspondence
Address: |
MICHAEL RIES
318 PARKER PLACE
OSWEGO
IL
60543
US
|
Family ID: |
41115070 |
Appl. No.: |
12/412359 |
Filed: |
March 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61039980 |
Mar 27, 2008 |
|
|
|
Current U.S.
Class: |
60/670 ; 290/52;
62/115; 62/335; 62/498; 62/515 |
Current CPC
Class: |
F25B 2400/24 20130101;
F01K 9/003 20130101; F25B 2400/06 20130101; F25D 16/00
20130101 |
Class at
Publication: |
60/670 ; 62/335;
62/498; 62/515; 62/115; 290/52 |
International
Class: |
F01K 23/00 20060101
F01K023/00; F25B 7/00 20060101 F25B007/00; F25B 1/00 20060101
F25B001/00; F25B 39/02 20060101 F25B039/02; F01D 15/10 20060101
F01D015/10 |
Claims
1. A steam powered power plant includes; a first boiler for
providing steam to a turbine wherein said turbine drives a
generator to produce power and wherein exhaust steam from said
turbine is cooled in a condenser and returns to said boiler, and a
first refrigeration cycle wherein a first compressor compresses a
first flow of refrigerant and wherein said compressed flow of
refrigerant is cooled in an air cooled condenser, throttled and
expanded in said condenser to cool said exhaust steam, and a second
refrigeration cycle wherein a second compressor compresses a second
flow of refrigerant and said second flow of refrigerant rejects
heat in an air cooled condenser, throttled and expanded to cool a
thermal storage wherein said thermal storage can be used to cool
said steam condenser.
2. The steam power plant of claim 1 wherein said generator
generates electrical power to power a load and wherein said load is
sensed to determine the cooling operation of said power plant,
wherein during a low load condition said first refrigeration cycle
provides cooling to said steam condenser and said second
refrigeration cycle provides cooling to said thermal storage and
during a peak load said first refrigeration cycle and said second
refrigeration cycle are turned off and cooling of said condenser is
provided from said thermal storage.
3. The steam power plant of claim 1 wherein said thermal storage is
a tank of water.
4. The steam power plant of claim 1 wherein at a partial load
condition, wherein said load is greater than said low load but less
than said peak load said first refrigeration cycle provides cooling
to said steam condenser and said second refrigeration cycle is
turned off.
5. The steam power plant of claim 1 wherein said thermal storage
includes a tank of water and a heat exchanger and wherein coolant
from said condenser flows through said heat exchanger during said
peak loading.
6. The steam power plant of claim 5 wherein the flow of coolant
through said heat exchanger is controlled by valves that are opened
during said peak loading.
7. The steam power plant of claim 5 wherein said first and second
compressors are powered by said turbine.
8. A steam power plant includes; a steam driven turbine wherein
said turbine drives a generator to produce power and wherein
exhaust steam from said turbine is cooled in a condenser, and a
first dry refrigeration cycle wherein a first compressor compresses
refrigerant and wherein said compressed refrigerant is expanded in
said condenser to cool said waste steam, and a second dry
refrigeration cycle wherein a second compressor compresses a second
refrigerant and said second refrigerant is expanded to cool a
thermal storage media wherein said thermal storage media can be
used to cool said steam condenser.
9. The steam power plant of claim 8 wherein said generator
generates electrical power to power a load and wherein said load
determines the cooling operation of said power plant, wherein
during a low load condition said first refrigeration cycle provides
cooling to said condenser and said second refrigeration cycle
provides cooling to said thermal storage media and during a peak
load said first refrigeration cycle and said second refrigeration
cycle are turned off and cooling of said condenser is provided from
said thermal storage media.
10. The steam power plant of claim 9 wherein said thermal storage
media is held in a tank and a heat exchanger is located in said
tank in contact with said media and wherein refrigerant from said
steam condenser flows through said heat exchanger during said peak
loading to cool said exhaust steam.
11. The steam power plant of claim 9 wherein said thermal storage
media is water.
12. The steam power plant of claim 9 wherein at a partial load
condition, wherein said load is greater than said low load but less
than said peak load said first refrigeration cycle provides cooling
to said steam condenser and said second refrigeration cycle is
turned off.
13. The steam power plant of claim 10 wherein the flow of coolant
through said heat exchanger is controlled by valves that are opened
during said peak loading.
14. The steam power plant of claim 10 wherein said first and second
compressors are powered by said generator.
15. The method of operating a steam plant including the steps of;
boiling water to produce steam, powering a turbine driven generator
using said steam, condensing exhaust steam from said turbine with a
condenser, sensing a load on said generator, if said load is below
a threshold, driving a first compressor to provide refrigerant to
said condenser to cool said exhaust steam, if said loading is below
a second threshold driving a second compressor to cool a heat
sink.
16. The method of claim 15 wherein the step of driving a second
compressor to cool a heat sink includes the step of providing a
flow of refrigerant through said heat sink at a peak load of said
steam power plant.
17. The method of claim 15 wherein the step of providing a flow of
refrigerant through said heat sink is controlled by opening valves
to a heat exchanger in said heat sink and wherein said heat sink is
a water tank.
18. The method of claim 15 wherein if said load rises above said
second threshold said second refrigeration cycle is turned off.
19. The method of claim 15 wherein the flow of refrigerant is
controlled by opening valves to said condenser.
20. The method of claim 15 wherein the step of driving a first
condenser and driving a second condenser includes drawing
electrical power from said generator.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 61039980, filed 27 Mar. 2008, the
entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Most of the world electricity supply is covered by steam
generating power plants. In these plants, heat from the exhaust
steam of the turbine has typically been transferred in a condenser
to cooling water from a river, lake, sea or some other natural
water supply. However, with the increased number of power plants,
the number of natural sources of cooling water decreased,
necessitating the use of wet cooling towers, where the supply of
natural cooling water is insufficient. With developing and
foreseeable shortages of adequate water sources in the arid regions
alternate technologies are being sought for heat rejection.
[0004] United States Patent application US 2007/0137205 A1 to Brown
proposed to combine the conventional steam cycle with a
conventional refrigeration cycle and to replace the once through
cooling water condenser of the steam cycle with a refrigerant
cooling condenser. The refrigerant is heated in the steam condenser
while condensing the steam. It then completes the refrigeration
cycle to be cooled and recirculated through the steam condenser. In
a conventional steam plant, nearly double the rate of net-power
generation is rejected as waste heat. Nearly 80% of this rejection
occurs in the steam condenser, and accordingly plenty of cooling is
required. This calls for consuming a substantial portion of power
generated by the steam plant to drive the compressor of the
refrigeration machine. As a result, a material amount of reduction
in total net power of the plant is brought about. Hence, the net
power generated by the plant would be considerably less than the
demanding load of the end-users during the peak-loads.
[0005] As can be seen, there is a need for an improved apparatus
and method of cooling the exhaust steam from the turbine of a steam
power plant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows a schematic of the system of the present
invention, and
[0007] FIG. 2 shows a flow chart of the method of operation of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0008] An emerging alternative to the traditional water consumptive
water-cooling technology is dry cooling, where the heat is rejected
to air, directly or indirectly without any loss of water. The steam
condensing pressures and temperatures of a dry cooled unit are
significantly higher than a wet cooled unit, due to the low
transfer rates of dry cooling and operation at the dry bulb
temperature. This results in a reduction in net power output of the
steam plant. The current invention combines a conventional steam
plant cycle having a refrigerant-cooled condenser with two
conventional refrigeration cycles and a cooling thermal storage
container. Both refrigeration cycles are operated during
part-loads. The first one is used to cool directly the steam plant
condenser by cooling and condensing the refrigerant vapor and
re-circulating it back through the steam condenser. The other
machine serves for producing cooling to be stored in the cooling
storage container. During the period of peak-loads, both
refrigeration cycles are stopped, and the refrigerant vapor exiting
the steam condenser is condensed in the cooling storage container
and re-circulated through the refrigerant-cooled steam condenser.
In this way, the power generated during the peak loads is fully
made available to the end users.
[0009] The main intent of this invention is to maintain the net
power output of a steam plant, using refrigerant-cooled condenser,
at its maximum value during peak-loads. Dissipation of heat
absorbed by the cooling refrigerant in the steam condenser tubes
necessitates circulating it through a complete refrigeration cycle.
An appreciable portion of the steam plant power output is consumed
to operate the refrigeration compressor. To save the compressor
power at peak-loads for use by the end user, it is proposed in this
invention to produce excess cooling during the part-loads and store
it to be used over the peak-loads period for cooling the
refrigerant getting out of the steam condenser. Hence, the
refrigerant compressor is stopped during the peak loads period, and
the whole power generated by the steam plant is made available to
cover the demand of the end users at this period. This invention
saves investments in building new units for meeting the increasing
demands of the end users through the period of peak-loads.
[0010] The configuration of the proposed combined steam power plant
and cooling thermal storage system 100 is shown schematically in
FIG. 1. This system 100 consists of three cycles and a cooling
storage container. The three cycles are a steam power plant cycle
101 and two refrigeration cycles 103, 105 each cycle shown in a
dashed line box. The steam cycle 101 can comprise the components of
which a modern steam power plant is composed. Of these components
only the boiler 1, steam turbine 2, refrigerant-cooled condenser 3,
feed water pump 4 and generator 5 are shown in FIG. 1. The load on
generator 5 can be sensed and the first refrigeration cycle 103 is
used for direct cooling of the steam condenser 3 during part-loads
when the excess power generated by the steam plant 101 is above a
sufficient or greater for operating its compressor 6 and the load
is below a first threshold value. The first refrigeration cycle 103
is made up of a compressor 6, driven by an electric motor 7, a
condenser 8, a throttling valve 9 and an evaporator 3a within the
refrigerant-cooled condenser 3, which acts at the same time as part
of the steam condenser 3 of the steam plant 101. In this cycle 103,
the cold refrigerant liquid exiting the throttle valve 9 evaporates
as it passes through the tubes of the steam condenser (evaporator)
3 by absorbing vaporization heat of the turbine 2 exhaust steam.
The water condensate and refrigerant vapor leaving the steam
condenser (evaporator) 3 complete the steam cycle 101 and the first
refrigeration cycle 103 respectively. The second refrigeration
cycle 105 serves to produce cooling at low part-loads, below a
second low threshold of loading, to be stored for later use at the
peak-loads. It works simultaneously with the first refrigeration
cycle 103 when the excess power is sufficient to drive the
compressors 6, 10 of both cycles; otherwise the first refrigeration
cycle 103 works alone. The second refrigeration cycle 105 consists
of a compressor 10, operated by an electric motor 11, a refrigerant
condenser 12, a throttling valve 13 and an evaporator 14. The cold
refrigerant liquid leaving the throttle valve 13 evaporates as it
flows through the evaporator 14 by absorbing heat from a heat sink
such as cooling storage water container 15. In this way, media in
the cooling storage container 15 gets colder, where the cooled
media such as water is stored for later use during peak-loads. The
cooling storage container 15 might use water for example as the
storage media.
[0011] The two refrigeration cycles 103,105 have three different
operating periods along the time of a working day: the period of
direct cooling, the period of storing the cooling and the period of
outage of both refrigeration cycles 103, 105. The period of direct
cooling occurs at part-loads when the excess power of the steam
plant 101 is adequate or greater for running the refrigerant
compressor 6 of the first refrigeration cycle 103 for producing
cooling that is used to directly condense the exhaust steam of the
turbine 2. During this period, the valves 18 and 21 are opened and
the valves 19 and 20 are closed. The cool refrigerant liquid
getting out of the throttle valve 9 flows through the tubes of
steam condenser (evaporator) 3, absorbs the heat of vaporization of
the steam coming out of the steam turbine 2 and is vaporized. The
refrigerant vapor exiting the steam condenser (evaporator) 3 is
sent to the refrigerant compressor 6, where it then completes the
first refrigeration cycle 103.
[0012] The period of storing the cooling takes place at low
part-loads when the excess power of the steam plant 101 suffices to
drive the compressors 6, 10 of both refrigeration cycles 103, 105.
The cooling produced by the first refrigeration cycle 103 serves to
directly condense the exhaust steam of the turbine 2 at this
period, while the cooling produced by the second cycle 105 is
stored in the cooling storage container 15. During this period the
valves 19 and 20 are closed and the valves 18 and 21 are opened.
The refrigerant vapor coming out of the steam condenser
(evaporator) 3 and evaporator 14 are compressed in the compressors
6 and 10, respectively and complete the refrigeration cycles 103,
105 respectively. The period of outage of the refrigeration
machines comes about over the period of the steam plant 101
peak-loads. During this period, the refrigeration compressors 6 and
10 are stopped, and the valves 18 and 21 are closed, while the
valves 19 and 20 are opened. The cooling refrigerant of the steam
condenser of cycle 101 changes its loop, in which it no longer
flows through the first refrigeration cycle 103. Rather, the
refrigerant vapor exiting the steam condenser (evaporator) 3 flows
through the heat exchanger 16, where it rejects the heat absorbed
in the steam condenser 3 to the cooling storage container 15 and is
condensed. It is then pumped by the circulating pump 17 to the
steam condenser (evaporator) 3 for condensing the exhaust steam of
turbine 2. The refrigerant is vaporized in the steam condenser 3
and repeats this cooling loop until the demand of the end user gets
enough low, so that the first refrigeration cycle 103 is
re-activated.
[0013] FIG. 2 shows a simple control schematic 200 for the
refrigerant cycles of the steam power plant and cooling thermal
storage system 100. The power load on electrical line 50 is sensed
202 and the amount of load on line 50 determines the operation of
the system 100. If peak loading 204 is sensed then cooling 206 from
the storage tank 15 can supply the only source of cooling so long
as the tank 15 had a temperature low enough to provide the required
cooling. If the temperature of tank 15 was ever too high to provide
required cooling then the cooling cycle 103 would turn on and this
would result in some loss of efficiency. With proper system design
tank 15 could always be able to control the cooling. If the load at
line 50 is below peak load but above a low load a partial load 208
is sensed and single stage cooling 210 from cycle 103 is used. At a
low load level 212, low enough to supply all the energy required at
line 50 and still run both compressors 6 and 10, the system 100
will operate in dual stage cooling 214 with the second stage
cooling the tank 15.
[0014] It will be obvious to those skilled in the art that
modifications may be made to the embodiments described above
without departing from the scope of the invention. Thus the scope
of the invention should be determined by the claims in the formal
application and their legal equivalents, rather than by the
examples given.
* * * * *