DESCRIPTION
TECHNICAL FIELD
The present invention relates to condensed water recovery devices,
particularly, but not exclusively, for power plants including one or more
thermal machines which in operation need to be supplied with air for
tit combustion and/or ventilation purposes. Further, the present invention
relates to a method for improving the overall efficiency in a power plant of
the above mentioned type.
BACKGROUND ART
A power plant for the production of electric or mechanical energy may
include thermal machines, e.g. internal or external combustion engines like
gas turbine engines or reciprocating engines or others.
Power plants of the above mentioned type normally includes an air inlet for
providing combustive air inside the thermal machines of the power plant
and an air ventilation circuit for providing cooling air on the outer surfaces
of the same thermal machines. Such power plants are frequently needed to
perform in hot environment or season and, particularly, they may be
requested to provide peak power on the hottest hours of each day or on
specific seasons, i.e. summer. When the power plant includes a gas
turbine, unfortunately, as the inlet air temperature to a power plant goes up,
the power that the turbine can generate goes down. This has driven the
need for inlet-chilling systems including one or more heat exchangers
installed at the air inlet, particularly within an air filter device, of the power
plant.
Traditionally, there have been three options available for cooling down such
heat exchangers: mechanical or evaporative or absorptive. Mechanical
cooling uses mechanical compression to reduce the inlet air temperature to
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optimize the output of the thermal machine. Evaporative cooling sprays
water into the turbine inlet air stream where it evaporates, cooling the air.
Absorption cooling uses a source of heat, normally extracted from the
exhaust of the thermal machine, to provide the energy needed to drive the
cooling process.
In all the above cases, the cooling process produces condensed water
downstream the heat exchangers. Such water is normally considered as an
industrial waste and is therefore discharged in the waste liquid treatment
plant.
Alternatively, the condensed water which is produced by the cooling
process is recovered and recycled for further industrial use in the power
plant. For example, in a power plant including a gas turbine, it is known
from US patent n. 5390505 to use such water, which is essentially
demineralised water, in closed cycle, by injecting it into combustion zones
of the gas turbine, in order to achieve power augmentation, fuel saving and
nitrogen oxide (NOx) abatement. The above solution permits to increase
the efficiency of the gas turbine but shows also some inconveniences. In
fact, adding in the power plant a circuit for the introduction of the
condensed water in the gas turbine may result in an increase of corrosion
damages and thermal stresses in the hot section of the gas turbine and
therefore in an increase of maintenance interventions, which imply stopping
the power plant. Consequently the overall availability and reliability of the
power plant would be reduced.
Inserting a water recovery device at the air inlet of the power plant normally
results in a large production of condensed water. In some cases, when a
lower amount of condensed of water is requested, (for example 0.5 - 3
m3/h) such solution may not be convenient and it would be desirable to
derive another source of condensed water within the power plant.
SUMMARY
An object of the present invention is to provide a power plant comprising a
condensed water recovery device which allows recovering water from
humid air flowing in the power plant, thus optimizing the overall efficiency
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and minimizing water waste.
According to a first embodiment, the present invention accomplish the
object by providing a power plant comprising a thermal machine, an inlet
duct for delivering a combustive first fluid in said thermal machine and a
ventilation circuit for delivering a cooling second fluid to said thermal
machine, the first and/or the second fluid including water therein; wherein
the power plant further includes a water recovery device connected with the
inlet duct and/or the ventilation circuit for condensing and collecting water
from the first and/or the second fluid, the water recovery device being
associated with at least one heat exchanger thermally connected with the
inlet duct and/or the ventilation circuit, for cooling said first and/or said
second fluid beyond the dew point thereof, the water recovery device
further including connecting means for delivering the water condensed from
the first and/or the second fluid to a water using device.
According to a further advantageous feature of the first embodiment, the
water using device is of the open-cycle type.
According to a further advantageous feature of the first embodiment, the
water using device includes heating means for producing steam from the
water separated and collected by the water recovery device and a steam
expander for producing energy from said steam.
By providing a device for water recovery from the first combustive fluid or
from the second ventilation fluid or from both the first and the second fluids,
the present invention permits to conveniently generate the requested flow
of recovered water, according to the needs of the power plant. If a large
amount of recovered water is requested, the water recovery device is
connected with the inlet duct and, optionally, with the ventilation circuit. If a
reduced amount of recovered water is needed by the power plant, the water
recovery device is connected only with the ventilation circuit. In the latter
case, the needed amount of water can be obtained, in an existing power
plant, with simpler and less costly modifications than those required to
connect the inlet duct to the water recovery device.
The present invention allows optimizing the overall efficiency a power plant
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including a recovered water using device, particularly when the water using
device is of the open-cycle type, for example a device including heating
mean, like a boiler, for producing steam and a steam expander for
producing energy from such steam. The cold source for the cooling power
to be transferred to the heat exchangers of the water recovery device of the
present invention can be of any type: mechanical, evaporative or
absorptive.
A further object of the present invention is to develop a method for
improving efficiency in a power plant including a thermal machine.
According to a second embodiment, the present invention accomplishes
this further object by providing a method comprising the steps of thermally
connecting at least one heat exchanger with an inlet duct of the thermal
machine and/or the ventilation circuit of the thermal machine; operating the
heat exchanger to cool a first fluid flowing in the inlet duct and/or a second
fluid flowing in the ventilation circuit, the first and/or the second fluid
including water therein, bringing said first and/or said second fluid beyond
the dew point thereof in order to condensate the water therein, collecting
the water condensed from the first and/or the second fluid, using the
condensed water to improve the efficiency of the power plant.
According to a further advantageous feature of the second embodiment, the
step of using the condensed water consists in delivering the condensed
water to a combined cycle power unit and/or to a water treatment unit for
producing drinkable water and/or to heating means for producing steam.
The same advantages described above with reference to the first
embodiment of the present invention are accomplished by the second
embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
Other object feature and advantages of the present invention will become
evident from the following description of the embodiments of the invention
taken in conjunction with the following drawings, wherein:
- Figure 1 is a general schematic view of a power plant according to
present invention;
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- Figure 2 is a schematic view of a variant of the power plant in Figure 1;
- Figure 3 is a more detailed schematic view of the variant in figure 2;
- Figure 4 is a schematic view of a further variant of the power plant in
Figure 1;
- Figure 5 is a schematic view of a further variant of the power plant in
Figure 1;
- Figures 6 is a flow chart diagram of a method for improving efficiency in a
power plant according to the present invention.
DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS OF
THE INVENTION
- With reference to the embodiment figures 1-5, a power plant 1 comprises a
thermal machine 2, an inlet duct 3 for delivering a combustive first fluid in
the thermal machine 2 and a ventilation circuit 4 for delivering a cooling
second fluid to the thermal machine 2, the first and/or the second fluid
including water therein. Typically, the first and the second fluid is humid air.
When the thermal machine 2 is a gas turbine, the flow rate of the second
fluid in the ventilation circuit is lower than the flow rate of the first fluid in
the inlet duct. For a different type of the thermal machine 2, for example a
reciprocating combustion engine, the flow rate of the second fluid in the
ventilation circuit 4 may be greater than the flow rate of the first fluid in the
inlet duct 3.
The thermal machine 2 can be of various types, all requiring to be supplied
with a combustive first fluid and a ventilation circuit 4. For example, in
known embodiments of the power plant 1, the thermal machine 2 is a
reciprocating engine. In the embodiment of the power plant 1 shown in
figure 3, the thermal machine 2 is a gas turbine engine including an
upstream air compressor 2a, a downstream turbine 2b and a combustor 2c
between them. In embodiments in figures 1-4, the thermal machine 2
includes an exhaust stack 12 and is connected with an electric power
generator 13.
In another embodiment of the present invention, which is shown in figure 5,
the thermal machine 2 is a combined cycle power unit including a steam
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turbine and a steam condenser 2d, which is cooled, at least partially by the
second fluid in the ventilation circuit 4.
The power plant 1 further includes a water recovery device 10 connected
with the inlet duct 3 and the ventilation circuit 4 for condensing and
collecting water from the first and the second fluid, the water recovery
device being associated with a first heat exchanger 30 and a second heat
exchanger 40 thermally connected with the inlet duct 3 and the ventilation
circuit 4, respectively, for cooling the first and the second fluid beyond the
dew point thereof. The first and/or second heat exchangers are, for
example, constituted by air coils.
The first heat exchanger 30 assures, particularly in hot environments or
seasons, that the combustive first fluid is cooled in order to maximize the
power generated by the thermal machine 2.
In addition, the combustive fluid to be supplied to the thermal machine 2
needs to be filtered from impurities to avoid damaging or excessive wearing
of the components, in particular rotary components, of the thermal machine
2.
In order to assure the desired quality of the combustive fluid the power
plant 1 further includes, on a suction side of inlet duct 3, an inlet air
treatment system 5 including the first heat exchanger 30 and one or more
filtering modules 6, 7, respectively upstream and downstream the first heat
exchanger 30, for removing solid impurities and/or other impurities. The
inlet air treatment system 5 can be arranged in a plurality of configurations,
depending on the specific requirements of the power plant 1. For example,
the inlet air treatment system 5 may include a weather hood, or a plurality
of weather hoods, for protecting the inlet air treatment system 5 from
weather agents. In some embodiments, the upstream filtering modules 6 of
the inlet air treatment system 5 comprise HEPA and/or ULPA filters for
removing, respectively, bacteria and viruses from the humid air entering the
first heat exchanger 30.
Optionally, filtration may be requested also in the ventilation circuit 4. In
such a cases (figures 1, 4 and 5) an upstream filtering modules 40a,
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comprising HEPA and/or ULPA filters, are provided upstream the heat
exchanger 40.
For the chilling of the first and second heat exchanger 30, 40, the power
plant 1 comprises cold sources 31, 41 respectively connected to the first
and second heat exchanger 30, 40 for respectively extracting heat from the
first and the second fluid.
In the embodiments in figures 1-5, the cold source 31 is constituted by an
absorption refrigeration cycle, which is connected to a heat recovery
vapour generator 35 having a plurality of tubes thermally contacting the
exhaust stack 12.
• The tubes of heat recovery vapour generator 35 extract the thermal energy
from the exhaust gas of the gas turbine, for use in the absorption
refrigeration cycle 31. The absorption refrigeration cycle which constitutes
the cold source 31 in the embodiments in figure 1-5 is well-known in the art
and for this reason is not described in detail. For example, in an
embodiment of the present invention, absorption refrigeration cycle is of the
water-ammonia type.
In the embodiments in figures 1-5, the cold source 41 is of the mechanical
type, including a compression stage (not represented), which is well-known
in the art and for this reason is not described in more detail.
In general, for the scopes of the present invention, cold sources 31, 41
could be of any type, including also the evaporative type, provided that the
correct amount of cooling power is generated for the heat exchangers 30,
40, respectively. The type of could source 31, 41 is chosen considering the
specifications and requirements of the power plant 1. For example, it has to
be considered that normally the amount of water that can be condensed
from one of the first and second fluid is lower than the amount of water to
be condensed from the other fluid. For example, when the thermal machine
is a gas turbine, the amount of water that can be condensed from the
second fluid is lower than the amount of water to be condensed from the
first fluid. Therefore in such cases, when lower quantities of condensed
water are needed, only the second heat exchanger 40 is provided on the
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ventilation circuit 4 of the power plant 1.
In embodiments like that in figure 1, where both the first and the second
heat exchangers 30, 40 are present, the ventilation circuit 4 comprises an
inlet section which is open to the atmosphere for receiving humid air. In
embodiments like that in figures 2 and 3, where only the first heat
exchanger 30 is present, the inlet section of ventilation circuit 4 is directly
connected with the inlet duct 3 or the inlet air treatment system 5,
downstream the first heat exchanger 30, for receiving the same dry air
which flows in the inlet duct towards the thermal machine 2. In
embodiments like that in figure 4, where only the second heat exchanger 40
is present, the inlet section of ventilation circuit 4 is directly connected with
the inlet duct 3 or the inlet air treatment system 5, for receiving the same
humid air which flows in the inlet duct towards the thermal machine 2.
When dew point conditions are reached in the first and second heat
exchanger 30, 40, water is separated from the first and second fluid,
respectively, and collected at the bottom of the first and second heat
exchanger 30, 40. The water recovery device 20 includes connecting
means 25, 26, 27 for delivering the condensed water recovered from the
first and/or the second fluid to a water using device 20. Connecting means
25, 26, 27 include a feed pump 27 and pipes 25, 26 for respectively
providing water from he first and second heat exchanger 30, 40 to the
pump 27. The condensed water is delivered to the water user device 20
through the pump 27. Optionally, between the pump 27 and the water user
device 20 a water treatment device 50 is provided for improving the quality
of the water which enters the water user device 20.
In the embodiments in figures 1-5, the water using device 20 is of the opencycle
type, i.e. the condensed water recovered from the first and/or the
second fluid is delivered to a using device which is not re-used within the
thermal machine 2, but is sent to other using devices of the power plant 1.
In some embodiments the water using device 20 includes heating means
for producing steam from the water separated and collected by the water
recovery device 10. For example, in the embodiments in figures 2 and 3,
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the water using device 20 includes heating means for producing steam
which are constituted by an heat exchanger 35a provided along the exhaust
of the thermal machine 2, downstream heat recovery vapour generator 35.
Alternatively, in other (not shown) embodiment such heating means is
constituted by a boiler. The steam produced by such heating means is
delivered to a steam expander 51 for producing energy. After expansion,
steam exiting the steam expander 51 is then delivered to the exhaust stack
12 of the thermal machine 2. Steam expander 51 is connected to a second
electric power generator 52.
According to another (not shown) embodiment of the present invention, the
water using device 20 includes a water treatment unit for producing
drinkable water.
According to a further (not shown) embodiment of the present invention the
water using device 20 includes a combined cycle power unit.
In a third embodiment of the present invention, diagrammatically
represented in figure 6, a method 100 for improving efficiency in the power
plant 1 comprises five main steps 101-105.
In a first step 101 of the method 100, a first and a second heat exchangers
30, 40 are thermally connected with an inlet duct 3 of a thermal machine 2
of the power plant 1 and/or the ventilation circuit 4 of the thermal machine
2.
In a second step 102 of the method 100, the heat exchanger 30, 40 are
operated to cool a first fluid flowing in the inlet duct 3 and/or a second fluid
flowing in the ventilation circuit 4, the first and/or the second fluid including
water therein.
In a third step 103 of the method 100, are brought beyond the dew point
thereof in order to condensate the water therein.
In a fourth step 104 of the method 100, the water condensed from the first
and/or the second fluid is collected.
In a fifth step 105 of the method 100, the condensed recovered water is
used to improve the efficiency of the power plant.
In respective embodiment of the method 100, the fifth step 105 consists in
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delivering the condensed water to a combined cycle power unit and/or to a
water treatment unit for producing drinkable water and/or to heating means
for producing steam.
The present invention allows accomplishing the object and advantages
cited above, by providing a water recovery device which allows generating
the required flow of condensed water for any configuration or working
condition of the power plant. In addition, the present invention allows
reaching further advantages. In particular, the method above described can
be used in refurbishing an existing power plant by including therein a water
recovery device according to the present invention.
This written description uses examples to disclose the invention, including
the preferred embodiments, and also to enable any person skilled in the art
to practice the invention, inclUding making and using any devices or
systems and performing any incorporated methods. The patentable scope
of the invention is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other example are intended to
be within the scope of the claims if they have structural elements that do
not differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from the literal
languages of the claims.

WE CLAIM:
1. A power plant (1) comprising:
- a thermal machine (2);
- an inlet duct (3) for delivering a combustive first fluid in said thermal
machine (2) and a ventilation circuit (4) for delivering a cooling second fluid
to said thermal machine (2), the first and/or the second fluid including water
therein;
wherein the power plant (1) further includes a water recovery device (10)
connected with the inlet duct (3) and/or the ventilation circuit (4) for
condensing and collecting water from the first and/or the second fluid, the
water recovery device (10) being associated with at least one heat
exchanger (30, 40) thermally connected with the inlet duct (3) and/or the
ventilation circuit (4) for cooling said first and/or said second fluid beyond
the dew point thereof, the water recovery device (20) further including
connecting means (25, 26, 27) for delivering the water condensed from the
first and/or the second fluid to a water using device (20).
2. The power plant (1) according to claim 1, wherein the water recovery
device (10) is thermally connected with the ventilation circuit (4) for
separating and collecting water from the second fluid.
3. The power plant (1) according to claim 1, wherein the water using
device (20) is of the open-cycle type.
4. The power plant (1) according to claim 1 or claim 2, wherein the
water using device (20) includes:
- heating means for producing steam from the water separated and
collected by the water recovery device (10) and
- a steam expander for producing energy from said steam.
5. The power plant (1) according to claim 1 or claim 2, wherein the
water using device (20) includes a water treatment unit for producing
drinkable water.
6. The power plant (1) according to claim 2, wherein the water using
device (20) includes a combined cycle power unit.
7. The power plant (1) according to claim 1 or claim 2, wherein the heat
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exchanger is chilled by an absorption refrigeration cycle.
8. A water recovery device (10) for a power plant (1) including a thermal
machine (2), the water recovery device (10) being connected with the
thermal machine (2) for condensing water from a combustive first fluid
flowing in an inlet duct (3) of the thermal machine (2) and/or from a cooling
second fluid flowing in a ventilation circuit (4) of said thermal machine (2),
the water recovery device (10) being associate to at least one heat
exchanger (30, 40) thermally connected with the inlet duct (3) and/or the
ventilation circuit (4) for cooling said first and/or said second fluid beyond
the dew point thereof, wherein the water recovery device (10) further
• includes connecting means (25, 26, 27) for delivering the water condensed
from the first and/or the second fluid to a water using device (20).
9. Method (100) for improving efficiency in a power plant (1) including a
thermal machine (2), such method (100) comprising the steps of:
- thermally connecting (101) at least one heat exchanger (30, 40)
with an inlet duct (3) of the thermal machine (2) and/or the ventilation
circuit (4) of the thermal machine (2);
- operating (102) the heat exchanger (30, 40) to cool a first fluid
flowing in the inlet duct (3) and/or a second fluid flowing in the ventilation
circuit (4), the first and/or the second fluid including water therein,
- bringing (103) said first and/or said second fluid beyond the dew
point thereof in order to condensate the water therein,
- collecting (104) the water condensed from the first and/or the
second fluid,
- using (105) the condensed water to improve the efficiency of the
power plant.
10. Method (100) according to claim 9, wherein the step (105) of using
(105) the condensed water consists in delivering the condensed water to a
combined cycle power unit and/or to a water treatment unit for producing
drinkable water and/or to heating means for producing steam.