U.S. patent application number 11/101603 was filed with the patent office on 2005-12-01 for process and device for the recovery of energy.
Invention is credited to Claassen, Dirk P., Wancura, Herbert.
Application Number | 20050262842 11/101603 |
Document ID | / |
Family ID | 34140242 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050262842 |
Kind Code |
A1 |
Claassen, Dirk P. ; et
al. |
December 1, 2005 |
Process and device for the recovery of energy
Abstract
The invention relates to a process and device for the recovery
of energy from the waste heat of thermal or chemical processes,
wherein at least a portion of said waste heat evaporates a liquid
via at least one heat transfer means or heats a vapour or a gas,
increasing the pressure thereof, and this pressure is transformed
into mechanical energy in an engine (FIG. 1).
Inventors: |
Claassen, Dirk P.; (Graz,
AT) ; Wancura, Herbert; (Seiersberg, AT) |
Correspondence
Address: |
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
2101 L Street NW
Washington
DC
20037-1526
US
|
Family ID: |
34140242 |
Appl. No.: |
11/101603 |
Filed: |
April 8, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11101603 |
Apr 8, 2005 |
|
|
|
PCT/AT03/00309 |
Oct 10, 2003 |
|
|
|
Current U.S.
Class: |
60/618 |
Current CPC
Class: |
F02M 26/28 20160201;
Y02P 20/10 20151101; Y02T 10/166 20130101; Y02T 10/12 20130101;
Y02E 20/16 20130101; F02M 26/24 20160201; F01K 23/065 20130101;
F02M 26/05 20160201; Y02B 30/52 20130101; Y02P 20/124 20151101;
F02G 5/02 20130101; Y02E 20/14 20130101 |
Class at
Publication: |
060/618 |
International
Class: |
F01K 023/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 2002 |
AT |
A 1832/2003 |
Claims
1. A process for the recovery of energy from the waste heat of a
combustion engine comprising an exhaust gas recirculation, in
particular of a mobile combustion engine, characterized in that at
least a portion of the waste heat of the recycled exhaust gas
evaporates a liquid and/or heats a vapour and/or a gas, increasing
the pressure thereof, and this pressure is transformed into
mechanical energy in an engine.
2. A process for the recovery of energy from the waste heat of a
combustion engine, in particular of a mobile combustion engine, and
of a fuel cell, characterized in that at least a portion of the
waste heat of the exhaust gas of the combustion engine, in
particular of a recycled exhaust gas, and at least a portion of the
waste heat of the fuel cell evaporate a liquid and/or heat a vapour
and/or a gas, increasing the pressure thereof, and this pressure is
transformed into mechanical energy in an engine.
3. A process according to claim 1, characterized in that the vapour
or gas is evaporated or heated, respectively, in two or more
stages.
4. A process according to claim 1, characterized in that the
conversion into mechanical energy is carried out via a steam
turbine.
5. A process according to claim 1, characterized in that the
conversion into mechanical energy is carried out via a gas
turbine.
6. A process according claim 1, characterized in that the
conversion into mechanical energy is carried out via a piston
engine.
7. A process according to claim 1, characterized in that at least
one heat transfer stage is a heat pump.
8. A process according to claim 1 characterized in that, in front
of the engine, energy is stored in an energy store.
9. A process according to claim 1, characterized in that the
mechanical energy is used as an auxiliary energy for the combustion
engine and/or for the fuel cell and/or as an auxiliary energy in
means of transport such as vehicles, preferably for driving a
coolant pump and/or a hydraulic unit and/or a compressor for an
air-conditioning system.
10. A process according to claim 1, characterized in that the
mechanical energy is transformed into electrical energy.
11. A process according to claim 10, characterized in that the
electrical energy is used as an auxiliary energy for the combustion
engine and/or for the fuel cell and/or as an auxiliary energy in
vehicles, preferably for driving a coolant pump and/or a hydraulic
unit and/or a compressor for an air-conditioning system.
12. A process according to claim 1, characterized by an exhaust gas
turbine of the combustion engine, wherein exhaust gas to be
recycled is branched off before the exhaust gas is introduced into
the exhaust gas turbine.
13. A process according to claim 12, characterized in that at least
a portion of the waste heat of the exhaust gas expanded in the
exhaust gas turbine evaporates a liquid and/or heats a vapour
and/or a gas, increasing the pressure thereof, and this pressure is
transformed into mechanical energy in an engine.
14. A process according to claim 12, characterized in that the
liquid or the vapour or the gas, respectively, heated by the
expanded exhaust gas, is heated further, in particular superheated,
by the exhaust gas to be recycled.
15. A process according to claim 12, characterized in that the
liquid or the vapour or the gas, respectively, heated by the
expanded exhaust gas, is mixed with the liquid or the vapour or the
gas, respectively, heated by the recycled exhaust gas.
16. A process according to claim 2, characterized in that a liquid
or a vapour or a gas, respectively, heated by the waste heat of the
fuel cell is mixed with a liquid or a vapour or a gas,
respectively, heated by the exhaust gas of the combustion
engine.
17. A device for the recovery of energy from the waste heat of a
combustion engine comprising an exhaust gas recirculation, in
particular of a mobile combustion engine, characterized by the
combination of the following features: at least one heat transfer
means for transferring the thermal energy of the recycled exhaust
gas to a heat carrier medium, a device for increasing the pressure
of the heat carrier medium, an engine, preferably a steam turbine,
which transforms the energy stored in the heat carrier medium into
mechanical energy.
18. A device for the recovery of energy from the waste heat of a
combustion engine, in particular of a mobile combustion engine, and
of a fuel cell, characterized by the combination of the following
features: at least one heat transfer means for transferring the
thermal energy of the exhaust gas of the combustion engine to a
heat carrier medium, at least one heat transfer means for
transferring the thermal energy of the fuel cell to a heat carrier
medium, a device for increasing the pressure of the heat carrier
medium, an engine, preferably a steam turbine, which transforms the
energy stored in the heat carrier medium into mechanical
energy.
19. A device according to claim 17, characterized by two or more
heat transfer means which gradually heat the heat carrier
medium.
20. A device according to claim 17, characterized in that the heat
carrier medium is identical with the cooling medium for the
combustion engine and/or the fuel cell.
21. A device according to claim 17, characterized in that at least
one heat transfer means is a heat pump.
22. A device according to claim 17, characterized in that an energy
store is arranged in front of the engine.
23. A device according to claim 17, characterized in that the
engine is coupled with at least one drive for at least one
auxiliary power unit for the thermal or chemical process,
preferably cooling or lubricant pumps.
24. A device according to claim 17, characterized in that the
engine is coupled with at least one drive for at least one
auxiliary power unit for a vehicle, preferably with the drive of a
hydraulic unit and/or a compressor for an air-conditioning
system
25. A device according to claim 17, comprising an electric power
generator, preferably a generator, which is drivable by the engine
and transforms at least a portion of the mechanical energy into
electrical energy.
26. A device according to claim 25, characterized in that the
electrical energy is provided for the operation of auxiliary power
units for the combustion engine and/or the fuel cell, preferably of
cooling or lubricant pumps.
27. A device according to claim 25, characterized in that the
electrical energy is provided for the operation of auxiliary power
units for a vehicle, preferably of a hydraulic unit and/or a
compressor for an air-conditioning system.
28. A device according to claim 17, characterized by an exhaust gas
turbine of the combustion engine, wherein an exhaust-gas branch
duct for exhaust gas to be recycled, which branches off--in the
flow direction of the exhaust gas--from the exhaust gas duct in
front of the exhaust gas turbine, runs into a heat transfer
means.
29. A device according to claim 28, characterized in that a heat
transfer means for exhaust gas expanded in the exhaust gas turbine
is arranged downstream of the exhaust gas turbine.
30. A device according to claim 28, characterized in that a heat
carrier medium duct runs from the heat transfer means arranged
downstream of the exhaust gas turbine to the heat transfer means
for the exhaust gas to be recycled.
31. A device according to claim 28, characterized in that a mixing
device for the heat carrier medium heated by the exhaust gas to be
recycled and the heat carrier medium heated by the remaining
exhaust gas is provided.
32. A device according to claim 28, characterized in that a heat
carrier medium heated by the fuel cell can be supplied via a duct
to a mixing device for mixing with a heat carrier medium heated by
the exhaust gas of the combustion engine.
Description
[0001] The invention relates to a process according to the
preambles of claims 1 and 2 and in each case to a device for
carrying out these processes.
[0002] Processes for the recovery of energy from exhaust gases in
the large-scale commercial section of industrial plants are known
from the prior art, wherein essentially stationary processes yield
a comparatively constant exhaust gas stream, which usually flows
directly back to the process via a recirculation process. The
so-called cogeneration, wherein the thermal energy arising, e.g.,
in a steam plant is used directly for heating purposes or as
process heat, is, by far, more widely used.
[0003] In U.S. Pat. No. 5,896,738, for instance, a system for the
generation of steam from the exhaust gas of a gas turbine is
described, wherein the superheated steam mixed with fuel is
returned to the turbine. This system makes sense in large
stationary plants with optimized efficiency. In a mobile use under
variable load conditions, the additional water consumption would be
unacceptable on the one hand and, on the other hand, the efficiency
gain for the auxiliary energy would be forgone.
[0004] U.S. Pat. No. 4,729,225 describes a system wherein the turbo
charger is designed for such an amount of excess energy that said
energy can be used for auxiliary drive purposes. Such a solution
has the drawback that it has a direct impact on the design of the
combustion engine and, reciprocally, depends more strongly on the
operating condition thereof and hence cannot be used as an
independent system for the generation of auxiliary energy.
[0005] Document WO 02/31319 discloses a Rankine-process device for
an internal combustion engine, wherein energy is recovered from the
waste heat of a process. In the abstract, it is explained that a
portion of the waste heat evaporates a liquid via a heat transfer
means, increasing the pressure thereof, and this pressure is
transformed into mechanical energy in an engine.
[0006] In a first stage, water is thereby preheated in a first heat
exchanger in the exhaust gas. The preheated water is guided around
the cylinder block to a water jacket. Thereupon, a steam turbine
transforms the pressure into mechanical energy.
[0007] The documents U.S. Pat. Nos. 5,327,987, 5,609,029, WO
94/28298, U.S. Pat. No. 6,155,212, JP2001-132538 and U.S. Pat. No.
4,470,476 also each disclose a device and a process of a similar
type.
[0008] The exhaust gas recirculation (EGR) is a known process in
order to be able to reduce the undesired NOx-emissions in the
exhaust gas of (diesel) motor vehicles or other means of transport
such as ships etc. A portion of the exhaust gases is returned to
the combustion air or to the fuel/air mixture, respectively, via
the engine's suction system. A temperature decrease and a delay in
the combustion and hence a reduction in the discharge of nitrogen
oxide by approx. 40% are feasible; as a rule, the EGR is also
associated with a slightly higher consumption of fuel.
[0009] As is known, the exhaust gases of the combustion engines of
freight and passenger vehicles reach temperatures of 700 or
450.degree. C., respectively. Those hot exhaust gases must be
cooled to temperatures in the order of 150 to 200.degree. C. so
that it is possible to return those gases, which are mixed with
combustion air, to the engine. A temperature decrease in the
exhaust gas is feasible via the incorporation of a heat exchanger,
and, in a standard design, this is indeed constructed in that
way.
[0010] In the heat exchanger, for example the coolant which cools
also the combustion engine itself can be located. The coolant then
flows in a machine-cooling system-loop: First, it absorbs heat from
the engine and subsequently also from the exhaust gas in order to
finally release heat into the environment via a radiator. However,
in this system, very high demands are made both on the heat
exchanger and on the radiator (compact design, material resistance
against high temperatures, corrosion and depositions) due to the
increased temperatures.
[0011] In EP 1 091 113 A, possibilities are shown which avoid or at
least minimize the problems just described. For example, the
incorporation of a second high-temperature exhaust gas cooler leads
to the absorption of a large portion of the heat, resulting in that
the actual machine-cooling system-loop can operate as usual and
that no restrictions due to the high temperatures have to be
imposed. This second exhaust gas cooler is provided in a cooling
loop comprising a second radiator. An altogether more effective
EGR-cooling can be achieved, which, in addition, is not necessarily
associated with an increase in the radiator surface.
[0012] In any case, thermal energy must be withdrawn from the hot
exhaust gas so that it can be used in an EGR in such a way that a
reduction in the discharge of nitrogen oxide will occur. By means
of the known methods, the temperature of the exhaust gas can be
brought to the required value, however--and that is clearly the
great potential of the invention--the energy of the exhaust gas is
merely discharged without being intended for any further use.
[0013] Therefore, the invention has the task, namely, first of all,
of obtaining a reduction in the thermal load for the cooling system
by coverting the thermal energy of the exhaust gas in the exhaust
gas recirculation into mechanically usable energy and, secondly, of
creating a use of the system in terms of a further decrease in the
emissions of the combustion engine.
[0014] According to the invention, this task is achieved in that at
least a portion of the waste heat of the recycled exhaust gas
evaporates a liquid and/or heats a vapour and/or a gas, increasing
the pressure thereof, and this pressure is transformed into
mechanical energy in an engine. Advantageous variants thereof are
illustrated in the dependent claims 3 to 15.
[0015] According to a variant, in a process for the recovery of
energy from the waste heat of a combustion engine, in particular of
a mobile combustion engine, and of a fuel cell, at least a portion
of the waste heat of the exhaust gas of the combustion engine, in
particular of a recycled exhaust gas, and at least a portion of the
waste heat of the fuel cell evaporate a liquid and/or heat a vapour
and/or a gas, increasing the pressure thereof, and this pressure is
transformed into mechanical energy in an engine. Advantageous
variants are included in the dependent claims 3 to 16.
[0016] Claims 17 to 32 include preferred embodiments of devices for
carrying out the claimed processes.
[0017] Solutions wherein, under variable practical operating
conditions, the waste heat of a combustion engine comprising an
exhaust gas recirculation and/or of a fuel cell, is transformed
into an energy different from thermal energy, have not been used so
far. Thereby, the use as auxiliary energy for different consumers
present in connection with the primary chemical or thermal process
must be mentioned as particularly advantageous. Those consumers may
require mechanical energy, such as, for example, a compressor for
an air-conditioning system, or also electrical energy, such as, for
example, servo motors in the control process, or the lighting of a
vehicle. The specific advantage in terms of energy technology
consists, for example, in that the use of energy produced via the
primary chemical or thermal process, respectively, is always
subject to the full losses of the process, i.e., any energy
withdrawn productively will always produce further waste energy
whereas the use of lost energy from the exhaust gas will not create
any further demand for primary energy. If efficiencies of 10 to 35%
are regarded as typical for an internal combustion engine which
sometimes even has to be kept in operation specially for the
required auxiliary energy, the energy recovered by the present
invention saves, as a primary energy input, three to ten times as
much.
[0018] Solutions wherein the auxiliary energy of a vehicle is
generated, e.g., via a separate small diesel engine or, e.g., also
via a fuel cell are likewise known from the literature. Both types
of auxiliary energy sources (APU=Auxiliary Power Unit) exhibit
comparatively large heat losses.
[0019] Therefore, the present invention makes use of the excess
energy of waste beat arising in a vehicle driven by an internal
combustion engine comprising an exhaust gas recirculation, by
supplying the same via a thermal intermediate circuit, preferably
involving superheated steam, to an additional engine, preferably a
steam turbine, and by withdrawing mechanical energy either directly
at the output of the steam turbine or transforming the same into
electric current via a generator known per se. In the same manner,
the waste heat of the auxiliary energy sources is used for energy
utilization.
[0020] Depending on the process and design of the thermal or
chemical process, respectively, temperatures of 300.degree. C. to
1000.degree. C. can be used for the recovery of energy. In
combustion engines, particularly the exhaust gas is usable and is
generally available at 300 to 600.degree. C. Similarly, fuel cells,
if designed as high-temperature fuel cells, also have high exhaust
gas and coolant temperatures, which can reach up to 1000.degree. C.
High-temperature fuel cells are also used because they have a
slightly higher efficiency and are more tolerant in terms of the
supplied fuel. However, as a guide value, it can also be assumed
that approx. 50% of the supplied energy will go into the exhaust
gas or is available from the cooling process.
[0021] In the thermal intermediate circuit, a medium, optionally
pressurized, circulates, which, via heat transfer means, absorbs
the thermal energy from the exhaust gas and/or the cooling circuit
of the thermal or chemical process and subsequently releases the
same in the additional engine. Such a medium can be any liquid
suitable for a cooling or heating circuit, or a vapour or a gas.
Since a mobile plant occasionally also has to be operated at
temperatures below 0.degree. C., the medium is chosen such that it
does not solidify at ambient temperatures normal for vehicles. A
simple and proven example thereof is water mixed with antifreeze. A
particularly favourable embodiment provides that the thermal
intermediate circuit is connected directly to the coolant circuit
of the internal combustion engine, the same medium is used and the
through-flow between the two circuits can be controlled via, e.g.,
a valve. In this way, on the one hand, the medium cooled after the
engine can contribute to the cooling of the internal combustion
engine, and, on the other hands the medium preheated by the
internal combustion engine can reach a higher temperature after the
heat transfer means from the exhaust gas. This means that, in
addition, another portion of the thermal energy flowing into the
cooling circuit of the internal combustion engine is recovered.
Reciprocally, the energy recovered from the exhaust gas of the
auxiliary energy source, for instance of a fuel cell, can also be
used for preheating the internal combustion engine prior to the
start. This guarantees a reduced exhaust-gas discharge during the
cold start and, optionally, also a preheating of the passenger
compartment via the conventional beating of the vehicle.
[0022] In a further advantageous embodiment, the medium of the
thermal intermediate circuit is heated in at least two stages. The
waste heat of the combustion engine is used for preheating in a
first stage, and the waste heat of a second thermal or chemical
process, for example of the auxiliary energy source, heats the
medium in a second stage to the higher final value for the supply
to the additional engine. By means of this design comprising at
least two stages, the efficiency of the device for the recovery of
energy from the exhaust gas can be increased substantially, since
the inlet temperature into the engine is higher.
[0023] In the normal case, the heating of the medium is performed
via heat exchangers in one of the usual designs. A particularly
advantageous embodiment of a heat exchanger consists in that the
ratio of surface to volume is maximized via extremely fine metal
structures. In doing so, the gas flow control is chosen such that
laminar streams, which reduce the heat transfer, are prevented from
occurring. Heat exchangers have the effect that the temperature of
the medium in the intermediate circuit is always cooler than the
waste heat used for the heat transfer. Thus, if the internal
combustion engine has an exhaust gas temperature of, e.g.,
300.degree. C. at the location where the exhaust gas can be guided
into the heat exchanger without negative repercussions on the
combustion process, the medium in the intermediate circuit can
reach only about 260-280.degree. C. In one embodiment of the
invention it is therefore suggested that a heat pump is used as a
heat transfer means either instead of or in addition to a heat
exchanger. Thereby, the temperature of the medium and the heat
content thereof can be increased clearly beyond those of the
exhaust gas of the internal combustion engine. This allows, in
turn, an improved efficiency of the engine, preferably the steam
turbine.
[0024] A preferred embodiment of the invention is described
below.
[0025] According to FIG. 1, after the possibly provided turbo
charger, the exhaust gas of a combustion engine 1 is guided through
a first heat transfer means 2, prior to proceeding to the further
exhaust gas aftertreatment and to the exhaust. In the heat transfer
means 2, it thus heats a medium 3, preferably the condensate of a
water/antifreeze mixture, which thereby forms superheated steam.
The medium 3 is passed on to a possible second heat transfer means
4, which is charged on the primary side, e.g., by the exhaust gas
or the coolant of a fuel cell 5, thus producing an additional
overheating of the medium 3.
[0026] Alternatively or additionally, the heat from an exhaust gas
recirculation 13 of the combustion engine 1 can also be supplied to
a heat transfer means, preferably to the second one 4--optionally
also to another one.
[0027] In the steam cycle, an energy store 6 makes sure that a
variable occurrence of power as well as a variable demand can be
compensated for. After the energy store, the medium 3 drives an
engine 7, preferably a steam turbine, which transfers its energy
via the output shaft to an electric generator 8 and/or to a
mechanical consumer 9. The medium is returned to the liquid state
via a condenser 10 and is re-pressurized by a pump 11 and again
returned to the circuit.
[0028] In an advantageous advanced embodiment, the medium 3 is
charged directly from the cooling circuit of the combustion engine
1 via a switch unit 12. In normal operation, the medium circulates
in a closed circuit. Under certain operating conditions, such as,
e.g., in a cold start, the two circuits can be interconnected so
that the warmer one preheats the other one.
[0029] In another embodiment according to the invention, the engine
7 is a piston engine, either a reciprocating piston engine or a
rotating piston engine, or a gas turbine.
[0030] In a further embodiment according to the invention, the heat
transfer means 2 can be a heat pump for increasing the temperature
level of the medium 3 beyond that of the waste heat from the
thermal process of the combustion engine 1.
[0031] According to the invention and according to FIG. 2, the heat
of the exhaust gas, which must be cooled for the EGR, is used such
that it evaporates the liquid agent flowing through the first heat
exchanger (EGR evaporator 1). The energy contained in the vapour
can be used for another energy utilization, before the reliquified
vapour again passes through the circuit. The energy rendered usable
for mechanical purposes is not necessarily discharged via the
engine heat exchanger (chiller, radiator). Thus, said heat
exchanger can either be designed smaller or can yield the required
cooling capacity for correspondingly higher exhaust gas
recirculation rates--involving a corresponding benefit in terms of
a decrease in the emissions of nitrogen oxide.
[0032] Since engines operating on the expansion of steam exhibit a
narrow optimal operating range, in a special embodiment, the mass
flow and the pressure applied on the engine are limited by a
waste-gate. In said embodiment, the surplus portion of the vapour
generated in the process is added to the combustion air. This is a
process known per se which also serves for the purpose of reducing
the amount of nitrogen oxide. A direct coupling of those measures
is advantageous, since the operating ranges which exhibit high
recoverable thermal energy flows (full load) are also those ranges
in which the discharge of nitrogen oxide emissions reaches its
peak. However, in this operating mode, the vapour is used up so
that it becomes necessary to refill the system (FIG. 3).
[0033] The vapour can be mixed with a vapour generated otherwise in
order to increase, in this manner, the volume rather than the
temperature (FIG. 4, 5, 6). An increased vapour volume can be used
for efficiency purposes in analogy to a vapour compressed by
pressure. The vapour generated otherwise can originate both from
energy sources of a heat engine and from a fuel cell. The coupling
of all heat sources is also provided according to the invention
(FIG. 6).
[0034] However, due to the higher temperature of the exhaust gas in
the exhaust gas recirculation circuit, the energy from the EGR can
also be used for superheating a vapour already generated otherwise
(FIG. 7), which then can drive, e.g., an engine connected to a
generator and/or mechanical consumers via a drive shaft.
[0035] The individual evaporators according to FIGS. 4, 5 and 6 are
operated in feedback with the evaporator output so that equal
pressure conditions prevail in the evaporator circuits and it
becomes possible to mix the vapour generated in the evaporator
connected in parallel. This is achieved by means of
output-controlled pumps P1, P2 and P3.
[0036] However, according to FIG. 7, two evaporators connected in
series are provided.
* * * * *