U.S. patent application number 12/641218 was filed with the patent office on 2010-07-01 for method for operating a regenerative heat exchanger and regenerative heat exchanger having improved efficiency.
This patent application is currently assigned to BALCKE-DURR GMBH. Invention is credited to Heinz-Guenter Raths.
Application Number | 20100163208 12/641218 |
Document ID | / |
Family ID | 40638070 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100163208 |
Kind Code |
A1 |
Raths; Heinz-Guenter |
July 1, 2010 |
Method For Operating A Regenerative Heat Exchanger And Regenerative
Heat Exchanger Having Improved Efficiency
Abstract
A regenerative heat exchanger, including a rotor mounted so it
is rotatable, which has at least one first gas volume flow to be
heated and at least one second gas volume flow to be cooled flowing
through it, as well as a method for operating the regenerative heat
exchanger, is provided. The inflowing first gas volume flow enters
the rotor at a first front side of the rotor and exits the rotor
again at a second front side of the rotor at an outflowing first
gas volume flow. To increase the heating performance, a leakage
volume flow is captured at the first front side of the rotor and
supplied to the inflowing first gas volume flow and/or a leakage
volume flow is captured at the second front side of the rotor and
supplied to the outflowing first gas volume flow.
Inventors: |
Raths; Heinz-Guenter; (Olpe,
DE) |
Correspondence
Address: |
BAKER & HOSTETLER LLP
WASHINGTON SQUARE, SUITE 1100, 1050 CONNECTICUT AVE. N.W.
WASHINGTON
DC
20036-5304
US
|
Assignee: |
BALCKE-DURR GMBH
Ratingen
DE
|
Family ID: |
40638070 |
Appl. No.: |
12/641218 |
Filed: |
December 17, 2009 |
Current U.S.
Class: |
165/7 ;
165/9 |
Current CPC
Class: |
F28D 19/041 20130101;
F28D 19/047 20130101; F28F 2265/16 20130101 |
Class at
Publication: |
165/7 ;
165/9 |
International
Class: |
F28D 19/04 20060101
F28D019/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2008 |
EP |
08021916.5 |
Claims
1. A method for operating a regenerative heat exchanger, including
a rotor having a first front side with a rotor seal and a second
front side with a rotor seal, through which a first gas volume flow
is heated and a second gas volume flow is cooled, the first gas
volume flow flowing into the rotor at the first front side and
flowing out of the rotor at the second front side, the method
comprising: capturing a leakage volume flow at the first front side
of the rotor in the area of the rotor seal; supplying the leakage
volume flow, captured at the first front side of the rotor, to the
inflowing first gas volume flow; capturing a leakage volume flow at
the second front side of the rotor in the area of the rotor seal;
and supplying the leakage volume flow, captured at the second front
side of the rotor, to the outflowing first gas volume flow.
2. The method according to claim 1, wherein the leakage volume flow
captured at the first front side of the rotor is introduced into
the inflowing first gas volume flow upstream from the rotor, and
the leakage volume flow captured at the second front side of the
rotor is introduced into the outflowing first gas volume flow
downstream from the rotor.
3. The method according to claim 2, wherein the leakage volume
flows are introduced into the first gas volume flow proximate to
the rotor.
4. The method according to claim 1, wherein the leakage volume
flows, captured at the first front side of the rotor and at the
second front side of the rotor, are separately supplied to the
inflowing first gas volume flow and the outflowing first gas volume
flow, respectively.
5. The method according to claim 4, wherein the regenerative heat
exchanger includes respective fan units to capture the leakage
volume flows from the rotor and supply the leakage volume flows to
the first gas volume flow.
6. The method according to claim 1, wherein the rotor seals are
radial seals, said capturing a leakage volume flow at the first
front side of the rotor in the area of the rotor seal is performed
by suctioning, and said capturing a leakage volume flow at the
second front side of the rotor in the area of the rotor seal is
performed by suctioning.
7. The method according to claim 1, wherein the rotor seals are
peripheral seals, said capturing a leakage volume flow at the first
front side of the rotor in the area of the rotor seal is performed
by suctioning, and said capturing a leakage volume flow at the
second front side of the rotor in the area of the rotor seal is
performed by suctioning.
8. The method according to claim 1, wherein the first gas volume
flow and the second gas volume flow pass through the rotor in
opposite directions.
9. The method according to claim 1, wherein an additional gas
volume flow flows through the rotor and is not supplied with
leakage volume flows.
10. A regenerative heat exchanger, comprising: a rotor, having a
first front side with a rotor seal and a second front side with a
rotor seal, through which a first gas volume flow is heated and a
second gas volume flow is cooled, the first gas volume flow flowing
into the rotor at the first front side and flowing out of the rotor
at the second front side; a first unit for capturing a leakage
volume flow at the first front side of the rotor in the area of the
rotor seal and supplying the leakage volume flow to the inflowing
first gas volume flow; and a second unit for capturing a leakage
volume flow at the second front side of the rotor in the area of
the rotor seal for supplying the leakage volume flow to the
outflowing first gas volume flow.
11. The regenerative heat exchanger according to claim 10, wherein
the first unit is connected to the rotor and the inflowing first
gas volume flow through a first line system, and the second unit is
connected to the rotor and the outflowing first gas volume flow
through a second line system.
12. The regenerative heat exchanger according to claim 11, wherein
the first and second units are fans.
13. The regenerative heat exchanger according to claim 10, wherein
the rotor seals are radial seals or peripheral seals.
14. The regenerative heat exchanger according to claim 10, wherein
the rotor seals are divided or provided with multiple openings.
15. The regenerative heat exchanger according to claim 10, wherein
the first and second units are suction units.
16. A regenerative heat exchanger, comprising: a rotor, including a
lower side with a rotor seal, an upper side with a rotor seal and a
heat storing mass disposed therebetween, through which a gas volume
flow is heated; a fan unit for capturing a leakage volume flow at
the lower side of the rotor in the area of the rotor seal and
supplying the leakage volume flow to the gas volume flow before the
gas volume flow enters the rotor.
17. The regenerative heat exchanger according to claim 16, further
comprising an additional fan unit for capturing a leakage volume
flow at the upper side of the rotor in the area of the rotor seal
and supplying the leakage volume flow to the gas volume flow after
the gas volume flow exits the rotor.
18. The regenerative heat exchanger according to claim 16, wherein
the rotor seal is a radial seal.
19. The regenerative heat exchanger according to claim 16, wherein
the rotor seal is a peripheral seal.
20. The regenerative heat exchanger according to claim 16, wherein
each rotor seal includes a plurality of openings.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to foreign Patent
Application EP 08021916.5, filed on Dec. 17, 2008, the disclosure
of which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates to a method for operating a
regenerative heat exchanger, in particular for air preheating in
power plants. Furthermore, the invention relates to a regenerative
heat exchanger.
BACKGROUND OF THE INVENTION
[0003] Regenerative heat exchangers of the relevant type (also only
referred to as heat exchangers hereafter) are used for heat
transfer from at least one gas volume flow to at least one other
gas volume flow. For this purpose, the heat exchanger can comprise
a rotating (and/or also revolving) storage mass (referred to
hereafter as a rotor), which moves relative to fixed flow
connections and is alternately heated by the at least one gas
volume flow and cooled down again by the at least one other gas
volume flow, whereby heat energy is transferable from at least one
gas volume flow to at least one other gas volume flow.
[0004] The rotor of a regenerative heat exchanger is typically
implemented as an essentially circular-cylindrical drum, slight
deviations from this shape being possible. The rotor has a central
rotational axis. The gas volume flows flow through the rotor
essentially parallel to the rotational axis. The flow through is
typically in opposite directions (so-called counter flow method).
In order to provide sufficient heat storage mass, but also increase
the mechanical stability of the rotor, it is sectored or segmented
into multiple cells or chambers, which are also used as the flow
channels for the gas volume flows. Heat-storage masses are
typically situated in these chambers, such as so-called heat
transfer plate packs.
[0005] In operation, a warm and/or hot gas volume flow flows
through the individual chambers of the rotor, the gas being able to
be flue gas from a combustion process, for example. Because the
warm or hot gas volume flow flows through, the heat-storing masses
of the chambers which it flows through heat up. Heat is withdrawn
from the gas volume flow flowing through, so that it has a lower
temperature upon exiting the rotor than upon entering. As a result
of the rotor rotation, the heated chambers finally reach the
section where a cooler or cold gas volume flow, such as fresh air,
flows through the rotor and is heated on the heat-storing masses of
these chambers, the heat-storing masses then cooling down again.
With this type of heat transfer, a type of heat storage capability
of the rotor is used in order to heat a first gas volume flow and
cool a second gas volume flow.
[0006] Alternatively, a rotor can also be implemented as fixed, for
example, and the flow connections may move relative thereto.
[0007] If the fresh air is used as the gas volume flow to be
heated, the heat exchanger can be used for so-called air
preheating. The efficiency of a power plant can be increased and
the pollutant discharge can be reduced by air preheating.
[0008] To reduce mass losses and/or volume losses in regard to the
gas volume flows, a complex seal is required on the rotor, which
has been the subject of numerous refinements for some time. The
sealing system for a rotor typically comprises at least one
peripheral seal and at least one radial seal. A peripheral seal
seals the gas volume flows flowing through the rotor at the
external circumference of the rotor to the outside. A peripheral
seal can comprise an axial seal and/or lateral seal on the outer
circumference of the rotor. A radial seal is to prevent a so-called
flow short-circuit and/or short-circuit volume flow between the
individual gas volume flows at a rotor front side. As a result of
the relative movement of the rotor to the seals and because of
changing heat expansion, gaps and/or residual gaps between the
seals and the rotor are unavoidable, through which leakage volume
flows occur, in particular between the gas volume flows (so-called
flow short-circuits), typically from the gas volume flow having the
higher pressure to the gas volume flow having the lower pressure.
In addition to volume losses, this also results in energy losses
and thus in unsatisfactory efficiency.
[0009] Suction methods and suction facilities are known from the
prior art for improving the efficiency of regenerative heat
exchangers, however, these methods and facilities typically do not
result in improvements of the efficiency for the transfer of the
heat energy in practice. Worsening of the efficiency has sometimes
even been observed.
SUMMARY OF THE INVENTION
[0010] Embodiments of the present invention advantageously improve
the efficiency of a regenerative heat exchanger.
[0011] In a method for operating a regenerative heat exchanger,
according to an embodiment of the invention, the rotor, which is
preferably mounted so it is rotatable, has at least one first gas
volume flow to be heated flowing through it, such as fresh air in
particular, the gas volume flow heating on the heat-storing masses
as it flows through the rotor. This is used in particular for air
preheating of fresh air for a power plant. Furthermore, the rotor
has at least one second gas volume flow to be cooled flowing
through it, such as flue gas and/or combustion gas or exhaust gas
in particular, which dissipates its heat to the heat-storing masses
of the rotor and is itself cooled in this way.
[0012] The rotor has a first front side or front face, at which the
inflowing first gas volume flow to be heated enters the rotor. The
rotor has a second front side or front face opposite to the first
front side, at which the outflowing first gas volume flow to be
heated exits the rotor again. The first front side is typically
also referred to as the "cold side" and the second front side as
the "hot side".
[0013] The first gas volume flow and the second gas volume flow are
sealed on the rotor using at least one rotor seal, in order to
limit volume losses and particularly flow short-circuits. A rotor
seal is particularly a peripheral seal, which seals a gas volume
flow on the outer circumference of the rotor, and/or a radial seal,
which seals the gas volume flows relative to one another and is to
prevent flow short-circuits and/or short-circuit volume flows.
[0014] Because leakage volume flows occur in the area of a rotor
seal, it is provided according to the invention that at least one
leakage volume flow is acquired and/or captured on the first front
side, or in the area of this front side, of the rotor and supplied
to the inflowing first gas volume flow, and/or at least one leakage
volume flow is acquired and/or captured on the second front side,
or in the area of this front side, of the rotor and supplied to the
outflowing first gas volume flow.
[0015] A leakage volume flow is particularly a short-circuit volume
flow from the first gas volume flow into the second gas volume
flow, which occurs in the area of a radial seal at the first front
side of the rotor or at the second front side of the rotor. Thus,
strictly speaking, this is a recirculation of a captured leakage
volume flow into the first gas volume flow to be heated.
[0016] The acquisition or capture of a leakage volume flow, which
occurs in the area of a rotor seal, typically cannot be performed
completely for technical reasons, so that acquisition or capture of
a leakage volume flow in the scope of this invention relates to a
substantial part of the leakage volume flow, which can be acquired
and/or captured under the particular technical conditions.
Acquisition and capture are to be understood broadly in the scope
of this invention and include all measures which are capable of
handling a leakage volume flow.
[0017] The method differs from the prior art at least in that a
leakage volume flow is only captured in the area of one of the
front sides or both front sides of the rotor. It can thus be
differentiated which temperature level a leakage volume flow has in
each case. Furthermore, the method, according to an embodiment of
the invention, also differs from the prior art in that, as a
function of the temperature level of the leakage volume flow, a
corresponding supply or recirculation is performed into the
inflowing first gas volume flow, which is still cool, or the
outflowing first gas volume flow, which has already been heated
(always on the same side of the rotor in regard to flow
technology). Energetic advantages are thus achieved, which increase
the efficiency relative to the prior art, as explained in greater
detail hereafter.
[0018] For a regenerative heat exchanger which is used in a power
plant for heat transfer from a hot flue gas volume flow (from a
combustion process) to a fresh air volume flow, for example, there
is typically a leakage volume flow (short-circuit volume flow) from
the fresh air volume flow into the flue gas volume flow in the area
of a radial seal. When determining the operating parameters and
designing the regenerative heat exchanger, such leakage volume
flows are taken into consideration, because the leakage volume flow
from the fresh air volume flow into the flue gas volume flow
results in additional cooling of the flue gas volume flow by
approximately 3.degree. to 7.degree. K. (so-called "corrected" flue
gas or exhaust gas temperature). There is thus a danger that the
temperature will fall below the acid dewpoint temperature of a
component of the flue gas to be cooled and damage (in particular
corrosion) of following facility components (such as dust removal
facilities and filter facilities) in the flue gas train will occur.
It must therefore be ensured that the temperature of the flue gas
volume flow at the exit of the rotor and/or upon exiting the
regenerative heat exchanger, in spite of the additional cooling by
the leakage volume flow from the fresh air volume flow, is higher
than a critical acid dewpoint temperature. The additional cooling
of the flue gas volume flow by the leakage volume flow from the
fresh air volume flow must therefore be taken into consideration in
the design of the regenerative heat exchanger and its operating
parameters. On the other hand, this additional cooling of the flue
gas volume flow is not energetically available for the heat
transfer from the flue gas volume flow to the fresh air volume
flow. Accordingly, a lower "uncorrected" flue gas temperature is
desirable.
[0019] Through the separate acquisition of a warm or hot leakage
volume flow and the supply or recirculation thereof into the
outflowing and already heated fresh air volume flow, and/or a cool
or cold leakage volume flow and the supply or recirculation thereof
into the inflowing and (still) cool fresh air volume flow, the
negative additional cooling effect can be largely avoided. In other
words: the now essentially "uncorrected" flue gas temperature can
be lowered to a similar level as the earlier "corrected" exhaust
gas temperature. With unchanged entry temperature of the gas volume
flows into the rotor and with unchanged gas volume flows, as a
result, the heat transfer from the flue gas volume flow to the
fresh air volume flow can be increased, without the temperature
falling below a critical acid dewpoint temperature in the flue gas
volume flow. The increase of the heat transfer is possible through
constructive design of the heat-storing masses, for example.
[0020] As a result of the defined recirculation, undesired cooling
of the flue gas volume flow before the rotor and also undesired
cooling of the flue gas volume flow after the rotor are also
largely avoided, which additionally increases the efficiency of the
regenerative heat exchanger.
[0021] As a result, the outflow-side temperature (i.e., the
temperature after the rotor and/or after the regenerative heat
exchanger) of the fresh air volume flow and thus the quantity of
heat in the combustion air for the power plant combustion process
are increased. This additional quantity of heat reduces the fuel
demand. In relation to a boiler performance of 700 to 800 MW,
savings in operating costs in the amount of .epsilon.150,000 to
.epsilon.400,000 per year may be reckoned without reduction of the
power, the savings increasing still further in the coming years
because of rising fuel prices. A reduction of the discharge of
pollutant gases, such as CO.sub.2 in particular, results as a
further substantial advantage.
[0022] According to an embodiment of the invention, it is
preferably provided that at least one leakage volume flow is
captured on the first front side of the rotor and supplied to the
inflowing first gas volume flow and, to be precise, introduced or
fed therein there, and at least one leakage volume flow is captured
on the second front side of the rotor and supplied to the
outflowing first gas volume flow, and, to be precise, introduced or
fed therein there. Through this acquisition on both sides (in
relation to the front sides of the rotor) and separate supply or
recirculation of leakage volume flows, the efficiency of the
regenerative heat exchanger improves significantly. Notwithstanding
this, of course, acquisition and supply or recirculation at only
one front side of the rotor is also possible and advantageous.
[0023] According to an advantageous refinement of the method, it is
provided that the supply or recirculation of the leakage volume
flow captured from the first front side of the rotor into the first
gas volume flow is not performed directly, but rather upstream from
the rotor. "Upstream" means that the supply occurs before the rotor
in the flow direction. Alternatively or additionally, it is
provided that the recirculation of the leakage volume flow captured
from the second front side of the rotor into the first gas volume
flow is not performed directly, but rather downstream from the
rotor. "Downstream" means that the supply occurs after the rotor in
the flow direction. The acquisition or capture of a leakage volume
flow and its supply or recirculation into the first gas volume flow
are thus separated in design and construction.
[0024] It is provided in particular for this purpose that the
supply or recirculation of a captured leakage volume flow in the
first gas volume flow occurs in spatial proximity, preferably in
direct proximity to the rotor. The flow distances may thus be kept
short in construction. A supplied or recirculated leakage volume
flow is only subject to a slight temperature influence.
[0025] It is advantageously provided that at least one leakage
volume flow acquired or captured at the first front side of the
rotor and at least one leakage volume flow acquired or captured at
the second front side of the rotor are recirculated on separate
paths in each case upstream into the inflowing first gas volume
flow and downstream into the outflowing first gas going flow. A
path or recirculation path is any unit which is capable of
transporting or conducting a gas volume flow. A path or
recirculation path is particularly a line system made of pipes and
pipe sections or the like.
[0026] It is preferably provided for this purpose that at least one
fan unit is used per path. A partial vacuum can be generated using
the fan unit, using which a leakage volume flow can be acquired or
captured at a front side of the rotor by suctioning. An
overpressure can also be generated using the fan unit, using which
the suction leakage volume flow can be supplied or recirculated
along the path or recirculation path to the first gas volume flow
and introduced or fed therein. A fan unit is particularly a
ventilator, which is preferably situated in a line system.
[0027] Furthermore, it is preferable that at least one leakage
volume flow is acquired or captured, preferably using suctioning,
at the first front side and/or the second front side of the rotor
in the area of a radial seal. This measure thus relates to a
particularly disadvantageous short-circuit volume flow, in
particular from the first gas volume flow into the second gas
volume flow.
[0028] It is also additionally or alternatively preferable that at
least one leakage volume flow is acquired or captured, preferably
by suctioning, at the first front side and/or the second front side
of the rotor in the area of a peripheral seal. This also results in
improvement of the efficiency.
[0029] According to a particularly preferred refinement of the
inventive method, it is provided that at least one first gas volume
flow to be heated and at least one second gas volume flow to be
cooled flow through the rotor in opposite directions, i.e., in the
counter flow method. Both gas volume flows have a lower temperature
level at the first front side ("cold side") than at the second
front side ("hot side"). It is thus easy to differentiate which
temperature level an acquired or captured leakage volume flow has.
A leakage volume flow acquired at the hot front side of the rotor
is supplied to the outflowing first gas volume flow or recirculated
therein and a leakage volume flow acquired at the cold front side
of the rotor is supplied to the inflowing first gas volume flow or
recirculated therein. Alternatively, the rotor can also have at
least two gas volume flows flowing through it in the same
direction.
[0030] In a preferred refinement of the method, at least two first
gas volume flows are provided, at least one captured leakage volume
flow, preferably all captured leakage volume flows, being supplied
into only one of these two first gas volume flows. This will be
discussed in greater detail in connection with the figures.
Alternatively, a separate recirculation into two or more first gas
volume flows is also possible.
[0031] The regenerative heat exchanger, according to an embodiment
of the invention, comprises a rotor having at least two gas volume
flows flowing through it, the rotor having a first front side, at
which an inflowing first gas volume flow to be heated enters the
rotor, and the rotor also having a second front side, opposite to
the first front side, at which the outflowing first gas volume flow
to be heated exits from the rotor again. Furthermore, the rotor
comprises at least one rotor seal, such as a radial seal and/or a
peripheral seal in particular, for sealing the first and the second
gas volume flows. The regenerative heat exchanger, according to an
embodiment of the invention, additionally comprises an acquisition
unit or capture unit for a leakage volume flow which occurs in the
area of a rotor seal, and at least one supply or supply unit or
recirculation unit, which is associated with this acquisition unit
or capture unit, for the acquired or captured leakage volume flow
into the first gas volume flow.
[0032] According to an embodiment of the invention, at least one
capture unit is provided on the first front side of the rotor
having at least one associated supply or supply unit for the
leakage volume flow captured at the first front side into the
inflowing first gas volume flow, and/or at least one capture unit
is provided on the second front side having at least one associated
supply or supply unit for the leakage volume flow captured at the
second front side into the outflowing first gas volume flow.
[0033] The regenerative heat exchanger, according to an embodiment
of the invention, is preferably capable of using the method
according to the invention described above. The method features
described above and the advantages thereof are therefore
transferable correspondingly to the regenerative heat exchanger
according to an embodiment of the invention.
[0034] A capture unit is any unit which is capable of acquiring or
capturing a leakage volume flow. A capture unit can be a system
made of individual components. A capture device is preferably a
suction unit.
[0035] A supply or supply unit is used for supplying or
recirculating a leakage volume flow acquired or captured using a
capture unit into the first gas volume flow. A supply or a supply
unit is preferably implemented by a line system, through which the
leakage volume flow acquired or captured on a rotor seal is
supplied in a defined manner to the first gas volume flow. If the
leakage volume flow originates from the first gas volume flow, the
supply or supply unit is, strictly speaking, a recirculation or
recirculation unit.
[0036] The line system of at least one supply or supply unit
preferably comprises at least one fan unit, using which a defined
flow can be generated in this line system.
[0037] The fan unit is designed so that a partial vacuum can be
generated in a connection line, which is situated between this fan
unit and a rotor seal, using which the leakage volume flow can be
suctioned at the relevant rotor seal. In particular, the rotor seal
is at least one radial seal and/or at least one peripheral seal
which has a flow connection to the fan unit via the connection
line. At least one radial seal and/or at least one peripheral seal
is preferably implemented as divided and/or has multiple openings,
so that a leakage volume flow occurring at this rotor seal can be
suctioned in a simplified manner.
[0038] The same fan unit also generates an overpressure in a
connection line which is situated between this fan unit and the
first gas volume flow, using which the leakage volume flow
suctioned at the rotor seal can be supplied to the first gas volume
flow and/or recirculated therein, strictly speaking, can be
introduced or fed therein.
[0039] It is particularly preferably provided that at least one
suction or suction unit for a leakage volume flow is provided on
the first front side of the rotor, in particular in the area of a
radial seal and/or a peripheral seal, having an associated supply
or supply unit for the suctioned leakage volume flow into the
inflowing first gas volume flow. It is also provided that at least
one suction unit for a leakage volume flow is provided on the
second front side of the rotor, in particular in the area of a
radial seal and/or a peripheral seal, having an associated supply
or supply unit for the suctioned leakage volume flow into the
outflowing first gas volume flow. The supplies or supply units are
implemented separately from one another and each comprise at least
one fan unit. This corresponds to a preferred and particularly
advantageous exemplary embodiment of the invention.
[0040] The invention may also be implemented similarly on a heat
exchanger having stationary heat-storing masses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows a preferred exemplary embodiment of the
invention in a schematic illustration.
[0042] FIG. 2 shows an alternative exemplary embodiment of the
invention in a schematic illustration.
DETAILED DESCRIPTION
[0043] The invention will now be described with reference to the
drawing figures, in which like reference numerals refer to like
parts throughout.
[0044] FIG. 1 shows a regenerative heat exchanger, identified as a
whole by 1, which is used in a power plant. It comprises a
circular-cylindrical rotor 2, which is horizontally oriented and is
mounted so it is rotatable around the vertical axis 3. Heat stores
4 (such as heat transfer plate packs as described at the beginning)
are located in the interior of the rotor 2. The rotor has a first,
lower front side 5a, a second, upper front side 5b, and a lateral
wall (peripheral wall).sub.7. Radial seals 8a and 8b (not specified
in greater detail) and peripheral seals 9a and 9b (not specified in
greater detail) are located on the front sides 5a and 5b.
[0045] According to the illustration, the rotor 2 has a first gas
volume flow 10, this being a fresh air volume flow, flowing through
it from bottom to top on the left side. The fresh air volume flow
10 is suctioned by a fan unit 14 and supplied to the rotor 2. The
fresh air volume flow 10 enters the rotor on the lower front side
5a of the rotor 2 and exits again on the upper front side 5b and is
heated on the heat stores 4 as it flows through the rotor 2, which
cool to the same extent in this case (as described at the
beginning). In relation to the rotor 2, the inflowing fresh air
volume flow is identified by 10a and the outflowing fresh air
volume flow by 10b.
[0046] On the right side, the rotor 2 has a second gas volume flow
11, this being a flue gas volume flow from a combustion process
flowing through it from top to bottom. The flue gas volume flow 11
enters the rotor 2 at the upper front side 5b and exits the rotor 2
again at the lower front side 5a and is cooled on the cool heat
stores 4 as it flows through the rotor 2, which heat up to the same
extent in this case and are subsequently available for heating the
fresh air volume flow 10 (as described at the beginning) After
leaving the rotor 2, the already cooled flue gas volume flow is
supplied to flue gas purification facilities and/or filter units
20.
[0047] As a result of the flow through in opposite directions, the
temperatures of both gas volume flows 10 and 11 are higher at the
upper, second front side 5b of the rotor 2 than at the lower, first
front side 5a. Therefore, the upper front side 5b can also be
referred to as the "hot side" and the lower front side 5a as the
"cold side".
[0048] In order to seal the two gas volume flows 10 and 11 on the
rotor 2, the radial seals 8a and 8b and the peripheral seals 9a and
9b are provided. The peripheral seals 9a and 9b are to seal the gas
volume flows 10 and 11 at the outer edge or outer circumference of
the rotor 2, while the radial seals 8a and 8b are to prevent mixing
of the gas volume flows 10 and 11 by flow short-circuits and/or
short-circuit volume flows. As a result of alternating thermal and
mechanical strain, there are always gaps or residual gaps between
the seals 8a, 8b, 9a, and 9b and the rotor 2, through which leakage
volume flows occur. In particular in the area of the radial seals
8a and 8b, leakage volume flows are additionally favored by
pressure differences in the gas volume flows 10 and 11, the fresh
air volume flow 10 usually having a higher pressure than the flue
gas volume flow 11 because of the fan unit 14. This results in
fresh air leakage volume flows 12a and 12b, so that fresh air is
transferred or flows into the flue gas volume flow 11 at a lower
temperature level, which results in an undesirable and
disadvantageous cooling effect in the flue gas volume flow 11 (as
described in greater detail above).
[0049] It is therefore provided that the leakage volume flows 12a
and 12b are captured in the area of the radial seals 8a and 8b and
the leakage volume flows from the "hot" front side 5b of the rotor
2 are to be supplied to the outflowing fresh air volume flow 10b or
introduced therein and the leakage volume flows from the "cold"
front side 5a of the rotor 2 are to be supplied to the inflowing
gas volume flow 10a or introduced therein. Through this separate
recirculation of the leakage volume flows from the "hot" front side
into the already heated outflowing fresh air volume flow 10b and
from the "cold" side into the still cool inflowing fresh air volume
flow 10a, the undesired and disadvantageous cooling effect
described above can be avoided in the flue gas volume flow 11,
whereby the efficiency of the heat exchanger and thus also of the
power plant can be increased as a result (as explained in greater
detail above). The condensation of critical flue gas components in
cold temperature strands can also be prevented or at least reduced
in the flue gas to be cooled.
[0050] The capturing of the leakage volume flows and/or fresh air
leakage volume flows 12a and 12b is performed by suctioning at the
radial seals 8a and 8b. In order to simplify the suctioning, the
radial seals 8a and 8b may be implemented as divided and/or having
a plurality of openings (not shown), through which a partial vacuum
may be effectively applied in the gap or residual gap between the
radial seal 8a and 8b and the rotor 2 and the leakage volume flows
may thus be captured. The partial vacuum is generated in each case
by a fan unit 16a and 16b, which can be a ventilator or the like,
for example. A connection line 17a or 17b, via which the captured
or suctioned leakage volume flows 12a and 12b are conducted away,
is situated in each case between the fan unit 16a and 16b and the
radial seals 8a and 8b. A connection line 18a or 18b, respectively,
extends from the fan unit 16a and 16b into the inflowing fresh air
volume flow 10a or 10b. These connection lines 18a and 18b are used
for supplying or recirculating the captured leakage volume flows
12a and 12b, which were conducted away, into the fresh air volume
flow 10. The fan units 16a and 16b are designed so that they
generate a partial vacuum in the connection lines 17a and 17b and
an overpressure in the connection lines 18a and 18b.
[0051] The connection lines 17a and 18a form, together with the fan
unit 16a here, a line system for the supply or recirculation of a
leakage volume flow 12a captured or suctioned at the first front
side ("cold side") 5a of the rotor 2 into the inflowing fresh air
volume flow 10a. Independently thereof, the connection lines 17b
and 18b form, together with the fan unit 16b here, a second
separate line system for the supply or recirculation of a leakage
volume flow 12b captured or suctioned at the second front side
("hot side") 5b of the rotor 2 into the outflowing fresh air volume
flow 10b. The line cross sections and the fan performance are
dimensioned correspondingly. It is also possible to segment the
connection lines or to situate multiple connection lines in
parallel. It is also possible to provide multiple fan units in
parallel or in series.
[0052] Alternatively to the exemplary embodiment described above,
it is also possible to provide suctioning and supply or
recirculation at only one of the front sides 5a and 5b of the rotor
2 (not shown), whereby a significant improvement of the efficiency
already results with less construction effort. Alternatively or
additionally, the leakage volume flows may also be captured at the
peripheral seals 9a and 9b and supplied to the inflowing fresh air
volume flow 10a or the outflowing fresh air volume flow 10b and fed
or introduced therein. This is shown for exemplary purposes on the
left side of the rotor 2 in FIG. 1 using a dashed line for the
peripheral seal 9a. A further fan unit can be used for the
suctioning and supply or recirculation (in this case into the
inflowing fresh air volume flow 10a) or the fan unit 16a can also
be used for suctioning the leakage volume flow 12a at the lower
front side 5a. In order to also simplify the suctioning at the
peripheral seals 9a and 9b, the radial seals 8a and 8b may be
implemented as divided and/or having a plurality of openings. The
efficiency of the regenerative heat exchanger 1 can be improved
further by the suctioning of a leakage volume flow at least one of
the peripheral seals 9a and 9b. According to the invention, the
supply or recirculation of a leakage volume flow acquired at a
peripheral seal 9a at the lower front side ("cold side") 5a is
performed into the inflowing, still cool fresh air volume flow 10a
and the supply or recirculation of a leakage volume flow acquired
at a peripheral seal 9b at the upper front side ("hot side") 5b is
performed into the outflowing, heated fresh air volume flow
10b.
[0053] FIG. 2 shows an alternative exemplary embodiment of the
invention. Only the differences from the exemplary embodiment of
FIG. 1 (see above statements) are discussed hereafter. Therefore,
the above statements on the exemplary embodiment of FIG. 1 apply
accordingly.
[0054] The essential difference from the exemplary embodiment of
FIG. 1 is that the rotor 2 has two separate gas volume flows 100
and 101 flowing through it in the same direction on its left side,
which are each heated as they flow through the rotor. The gas
volume flow 100 can be a secondary air volume flow, for example,
and the gas volume 101 can be a primary air volume flow, for
example. These gas volume flows 100 and 101 are used for different
intended purposes in a power plant. Notwithstanding the
illustration, in which the two gas volume flows 100 and 101 flow
through the rotor 2 adjacent to one another, they may also flow
through the rotor at different points in relation to the rotor
cross-section. The separate supply or recirculation of the leakage
volume flows captured or suctioned at the radial seals 8a and 8b is
performed here, on both sides of the rotor 2 according to the above
statements, into the same gas volume flow 100 in each case
(secondary air volume flow). Alternatively, it is also possible to
supply the captured leakage volume flows to the other gas volume
flow 101 (primary air volume flow).
[0055] It is also conceivable in the exemplary embodiment of FIG. 2
to provide the suctioning of a leakage volume flow at only one
front side 5a or 5b of the rotor 2. The suctioning of a leakage
volume flow can also be performed at a peripheral seal 9a and/or
9b, as described above.
[0056] The many features and advantages of the invention are
apparent from the detailed specification, and, thus, it is intended
by the appended claims to cover all such features and advantages of
the invention which fall within the true spirit and scope of the
invention. Further, since numerous modifications and variations
will readily occur to those skilled in the art, it is not desired
to limit the invention to the exact construction and operation
illustrated and described, and, accordingly, all suitable
modifications and equivalents may be resorted to that fall within
the scope of the invention.
* * * * *