U.S. patent application number 11/062960 was filed with the patent office on 2006-08-24 for thermal power plant.
This patent application is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Lutz Kahlbau, Wilfred Ulm.
Application Number | 20060185366 11/062960 |
Document ID | / |
Family ID | 36911174 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060185366 |
Kind Code |
A1 |
Kahlbau; Lutz ; et
al. |
August 24, 2006 |
Thermal power plant
Abstract
The invention relates to a thermal power plant including a
turbine (1, 2, 3) operated using at least one water-steam-loop (4),
and a generator (5) driven by said turbine (1, 2, 3). According to
the present invention, means (6, 7, 8, 9, 10) for cooling said
generator (5) are provided, which means (6, 7, 8, 9, 10) are de
signed for extracting condensate from said water-steam-loop (4),
transporting it to said generator (5) and returning it into said
water-steam-loop (4).
Inventors: |
Kahlbau; Lutz; (Chuluota,
FL) ; Ulm; Wilfred; (Longwood, FL) |
Correspondence
Address: |
Siemens Corporation;Intellectual Property Department
170 Wood Avenue South
Iselin
NJ
08830
US
|
Assignee: |
Siemens Aktiengesellschaft
|
Family ID: |
36911174 |
Appl. No.: |
11/062960 |
Filed: |
February 22, 2005 |
Current U.S.
Class: |
60/645 |
Current CPC
Class: |
F01K 13/006 20130101;
F01K 7/18 20130101; F01K 27/02 20130101 |
Class at
Publication: |
060/645 |
International
Class: |
F01K 13/00 20060101
F01K013/00 |
Claims
1. A thermal power plant, comprising: a turbine utilizing a
water-steam-cycle for energy transfer; a generator coupled to the
turbine for generating electricity; a generator cooling device for
cooling the generator, the generator cool ing device configured to
discharge a condensate from the water-steam-cycle, feeding the
condensate to the generator and returning the condensate to the
water-steam-cycle.
2. The thermal power plant according to claim 1, wherein the
generator cooling device comprises an extraction device for
extracting the condensate from the water-steam-cycle, the
extraction device arranged at such location of the
water-steam-cycle having the lowest condensate temperature within
the water-steam-cycle.
3. The thermal power plant according to claim 2, wherein the
extraction device is arranged adjacent to a condenser adapted to
convert steam exiting the turbine into the condensate.
4. The thermal power plant according to claim 2, wherein the
extraction device is arranged adjacent to a condensate pump.
5. The thermal power plant according to claim 4, further comprising
a low-pressure pre-heating device for pre-heating the condensate,
the low-pressure pre-heating device connected to the condensate
pump, wherein the extraction device is arranged upstream the
condensate pump and downstream a low-pressure pre-heating device
for pre-heating the condensate, the extraction device powered by
excess steam discharged from the turbine.
6. The thermal power plant according to claim 2, wh erein the
generator cooling device includes a returning device for
re-circulating the condensate into the water-steam-loop.
7. The thermal power plant according to claim 6, wherein the
condensate is re-circulated after being heated up during a cooling
pro cess including a heat transfer from at least one generator
component to the condensate.
8. The thermal power plant according to claim 5, wherein the
turbine comprises a low pressure turbine for supplying the
low-pressure pre-heating device with the excess steam.
9. The thermal power plant according to claim 1, wherein the
generator cooling device includes a circulation pump for feeding
the discharged condensate to the generator.
10. The thermal power plant according to claim 1, wherein the
generator cooling device includes a pipeline system for routing the
condensate through the generator cooling device.
11. A method of cooling a generator of a thermal power plant having
a turbine and a water-steam-cycle, the method comprising
discharging a condensate from the water-steam-cycle, feeding the
condensate to the generator and returning the condensate to the
water-steam-cycle, wherein heat emerging from at least one
generator component is transferred to the condensate.
12. The method according to claim 11, wherein the condensate is
discharged from the water-steam-cycle at such location of the
water-steam-cycle having the lowest condensate temperature within
the water-steam-cycle.
Description
FIELD OF THE INVENTION
[0001] This invention relates in general to a thermal power plant
including a turbine operated using at least one water-steam-loop,
and a generator driven by said turbine. The thermal power plant
referred to can e.g. be a conventional steam power plant, a
combined gas and steam power plant or a nuclear power plant.
BACKGROUND OF THE INVENTION
[0002] Thermal power plants known in the prior art comprise a
turbine, which is supplied with pressurized steam from a steam
raising unit. The pressurized steam expands in the turbine and
thereby causes the turbine to rotate. This rotational motion is
transferred via a drive shaft to an electric generator, which
generator converts the mechanical energy into electrical energy.
The inevitable energy losses during the energy conversion in the
generator lead to an undesirable heating of the generator. In order
to avoid excessive generator temperatures, it is necessary to cool
the generator during operation. In the prior art this task is achi
eved using air, hydrogen or pure water as cooling media. The heated
up cooling media is thereafter released directly into the
environment or is re-cooled by a cooling device if a closed cycle
cooling system is employed, in which case the thermal energy is
released into the environment indirectly. However, the thermal
efficiencies displayed by the above described thermal power plants
of the prior art are considered unsatisfactory.
[0003] Due to the above drawbacks in the prior art it is an object
of the present in vention to provide a thermal power plant with an
improved thermal efficiency.
SUMMARY OF THE INVENTION
[0004] In order to solve the above object, according to the present
invention, a power plant of the aforementioned type is provided,
which is characterized in that means for cooling the generator are
provided, which means are designed for extracting condensate from
the water-steam-loop, transporting it to the generator and
returning it into the water-steam-loop.
[0005] The present invention is based on the insight, that by using
condensate from the water-steam-loop for cooling the generator and
returning the heated up condensate into the loop, the excess
thermal energy produced by the generator can be transferred into
the water-steam-loop with minimal energy loss. This measure
improves the thermal efficiency of the overall thermal power plant
significantly.
[0006] It is advantageous, if the means for cooling the generator
comprise an extraction device for extracting the condensate from
the water-steam-loop, wherein the extraction device is arranged
close to a location of the lowest condensate temperature within the
water-steam-loop. Therewith the condensate transported to the
generator is essentially of the lowest temperature available within
the water-steam-loop. This allows for an optimum cooling effect of
the generator. The generator can therefore be cooled to a
relatively low temperature, which increases its efficiency.
Further, no or very little additional cooling, like air cooling
etc., needs to be provided to the gen erator, which results in the
thermal energy produced by the generator being transferred to the
water-steam-loop to a very high degree. This again leads to a high
thermal efficiency of the overall power plant.
[0007] Further, it is practical if the extraction device is
arranged in close proximity to a condenser converting the steam
exiting the turbine into condensate. After the expanded steam exits
the turbine it needs to be cooled down further in order to cause a
phase transition into water. This task can be achi eved using a
condenser, which may be connected via a cooling circuit to a
cooling facility, like a cooling tower etc. The water or condensate
exiting the condenser is of a temperature considerably below the
vaporization temperature and is therefore well suited for cooling
the generator. In order to utilize the condensate of relatively low
temperature for generator cooling, it is therefore practical to
position the extraction device in close proximity after the
condenser.
[0008] Additionally, it is advantageous if the extraction device is
arranged close to a condensate pump. A condensate pump is usually
positioned immediately after the condenser in order to move the
condensate on in the loop. If the extraction device is arranged as
above, it is due to the proximity to the condenser ensured, that
the temperature of the condensate is very low, and further the
momentum provided to the condensate by the condensate pump may be
of assistance for moving the condensate to the generator.
[0009] Further, it is expedient in case the extraction device is
arranged between the condensate pump und a low-pressure pre-heating
device designed for pre-heating the condensate and fed with excess
steam from the turbine. The low -pressure pre-heating device
represents the first stage for raising the temperature of the
condensate before it is again converted into high-pressure steam
for driving the turbine. For this purpose thermal energy provided
by excess steam supplied from the turbine is used. As the
condensate used for cooling the generator needs to be of a
comparatively low temperature, it is expedient to extract the
respective condensate for this purpose before it enters the low
-pressure pre-heating device.
[0010] In addition, it is advantageous if the means for cooling the
generator further comprise a return device for returning the
condensate into the water-steam-loop after the condensate has been
heated up during cooling the generator. The thermal energy
extracted from the generator in the form of an elevated temperature
of the condensate is mo st effectively fed back into the
water-steam-loop by returning it into the loop before pre-heating
takes place. As the condensate in the loop is at this point still
of a relatively low temperature, the injection of higher
temperature condensate has a signi ficant effect on the resulting
temperature of the combined condensate. In this case the generator
takes over part of the function of the low pressure pre -heating
device, as the condensate entering the device already has an
elevated temperature. Thereby, a higher temperature can be achieved
for the condensate after passing the low-pressure pre-heating
device.
[0011] It is further advantageous, if the turbine comprises a low
pressure turbine, which feeds the low-pressure pre-heating device
with excess steam. The turbine expediently comprises a
high-pressure turbine, a medium-pressure turbine and a low-pressure
turbine, through which turbines the high pressure steam produced in
a steam raising unit is routed consecutively, while successively
loosing pressure and temp erature. As the low pressure pre-heating
device is the first stage of heating the condensate and therefore
operates at non-maximum temperatures, it is expedient to heat the
device with excess steam from the turbine operating at the lowest
temperature of all turbines, which is the low-pressure turbine.
[0012] It is further expedient, if the means for cooling the
generator comprise a circulation pump for transporting the
extracted condensate to the generator. This measure speeds up the
circulation of the extracted condensate and therefore ensures a
sufficient stream of condensate to circle to the generator in order
to provide for the required cooling effect. By adjusting the
pumping speed of the circulation pump and therewith its suction
effect, it is further possible to control the amount of condensate
extracted from the water-steam-loop. It is therefore not required
to provide a special mechanical diverting device within the
extraction device in order to divert enough condensate towards the
generator. The amount of condensate required for cooling the
generator can rather be easily controlled by adjusting the
operating speed of the circulation pump.
[0013] Additionally, it is advantageous if the means for cooling
the generator comprise a generator cooling device, through which
the condensate extracted from the water-steam-loop is routed. The
generator cooling device is expediently in contact with the
generator, advantageously attached to it, and operates as a heat
exchanger between the generator and the condensate flowing through
the generator cooling device.
[0014] All features included in the dependent claims can be
essential to the invention individually and/or in any combination
with other features independent of the formal references of the
claim(s) containing the respective features.
BRIEF DESCRIPTION OF THE DRAWING
[0015] A detailed description of the present invention is provided
herein below with reference to the following drawing, in which:
[0016] FIG. 1 is a schematic representation of a thermal power
plant according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] A preferred embodiment of the thermal power plant according
to the present invention is shown in FIG. 1. The power plant
comprises three turbines, namely a high pressure turbine 1, a
medium pressure turbine 2 and a low pressure turbine 3, which are
all mounted on a single drive shaft 21 connected to an electric
generator 5. The turbines are operated by a water-steam-loop 4. The
high pressure turbine 1 is supplied with highly pressurized hot
steam from a steam raising unit 19. The steam expands to a certain
extent in the high pressure turbine 1 and thereby causes the
turbine and therewith the drive shaft 21 to rotate. The expanded
steam exiting the high pressure turbine 1 is both of reduced
pressure and of reduced temperature. Some of this steam is then
diverted to a high-pressure pre-heater 18 arranged prior to the
steam raising unit 19 in the water-steam-loop 4. The remaining
portion of the steam is routed to a re-heater 20 from where it is
forwarded to the medium-pressure turbine 2. In the medium-pressure
turbine 2 the steam expands further, thereby applying torque to the
medium-pressure turbine 2 and accordingly to the drive shaft 21. A
portion of the steam exiting the medium-pressure turbine 2 is
guided to a feed water container arranged prior to the
high-pressure pre-heater 18 in the water-steam-loop 4. The
remaining steam is routed to the low-pressure turbine 3, where the
steam expands even further causing torque to be applied to the low
pressure turbine 3 and accordingly to the drive shaft 21. The
combined torque of the three turbines drives the electric generator
5 via the drive shaft 21. The generator 5 converts this mechanical
energy into electrical energy.
[0018] A portion of the steam exiting the low-pressure turbine 3 is
fed to a low-pressure pre-heating device 13 arranged prior to the
feed water container 16 in the water-steam-loop 4. The remaining
steam, which is of very low pressure and of reduced temperature is
routed to a condenser 11, in which the steam is cooled down in
order to transfer into the liquid phase. The cooling can be
achieved by a cooling tower 14, which is thermally connected to the
condenser 11 via a cooling circuit 15. The condensate in the form
of water exiting the condenser 11 is then moved on in a
loop-pipeline 22 to the low pressure pre-heating device 13. For
this purpose a condensate pump 12 is arranged immediately after the
condenser 11. Closely after the condensate pump 12 some of the
condensate is diverted from the loop -pipeline 22 using an
extraction device 6. This extraction device 6 consists of branching
means, which allow some of the condensate to branch off into a
cooling pipeline 8. The amount of condensate to be diverted into
the cooling pipeline 8 can be controlled by adjusting the operating
speed of a circulation pump 7 arranged shortly after the extraction
device 6 in the path of the cooling pipeline 8. When running at a
high operating speed the circulation pump 7 generates a significant
suction activity causing more condensate to be diverted into the
cooling pipeline 8.
[0019] The condensate in the cooling pipeline 8 is then moved
through a generator cooling device 9, which is attached to the
generator 5. The generator 5 is thereby cooled, i.e. the thermal
energy is transferred from the generator 5 to the condensate. The
heated up condensate is then returned into the loop-pipeline 22
prior to entering the low pressure pre-heating device 13. This is
achieved using a return device 10, which consists of branching
means similar to the extraction device 6.
[0020] Extracting the condensate from the loop-pipeline 22, as
described, at a location shortly after the condensate pump 12 takes
advantage of the fact that the condensate at this location has
essentially the lowest temperature within the overall
water-steam-loop 4 due to the close proximity to the condenser 11.
This leads to a high cooling efficiency of the generator 9.
Further, returning the condensate heated up by the generator 5 back
into the loop-pipeline 22 before the pipeline enters the
low-pressure pre-heating device 13 increases the temperature of the
overall condensate stream entering the low-pressure pre-heating
device 13. The low-pressure pre-heating device 13 can therefore
achieve a higher target temperature for the condensate. This
improves the thermal efficiency of the overall thermal power
plant.
[0021] The low-pressure pre-heating device 13 uses, as described
above, excess steam from the low-pressure turbine 3 in order to pre
-heat the condensate under low pressure conditions. Thereafter, the
condensate enters the feed water container 16, which is supplied
with excess steam from the medium-pressure turbine 2. A feed pump
17 forwards the condensate to the high-pressure pre-heater 18,
which uses excess steam from the high pressure turbine 1 for
further pre-heating the condensate under high pressure conditions.
Finally, the condensate reaches the steam raising unit 19, which
uses the thermal energy produced by the power plant in order to
transfer the condensate into high pressure steam.
* * * * *