U.S. patent application number 13/641900 was filed with the patent office on 2013-02-07 for apparatus for the electrical production of hydrogen.
The applicant listed for this patent is Freimut Gadeke, Stefan Holler, Uwe Kuter, Nils Mantal, Claus Wurfel. Invention is credited to Freimut Gadeke, Stefan Holler, Uwe Kuter, Nils Mantal, Claus Wurfel.
Application Number | 20130032472 13/641900 |
Document ID | / |
Family ID | 42646487 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130032472 |
Kind Code |
A1 |
Holler; Stefan ; et
al. |
February 7, 2013 |
APPARATUS FOR THE ELECTRICAL PRODUCTION OF HYDROGEN
Abstract
An apparatus for the electrical production of hydrogen from
water includes an electrolyzer (1) of the PEM type. The
electrolyzer (1) has an inlet (2) for the introduction of water and
a first outlet (3) for the hydrogen which is enriched with water
and/or water vapor and is produced in the electrolyzer (1) and also
a second outlet (4) for oxygen. A water separation device (7) which
has at least a thermal separation stage (10) adjoins the
electrolyzer (1).
Inventors: |
Holler; Stefan; (Lubeck,
DE) ; Gadeke; Freimut; (Lubeck, DE) ; Wurfel;
Claus; (Lubeck, DE) ; Mantal; Nils; (Lubeck,
DE) ; Kuter; Uwe; (Lubeck, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Holler; Stefan
Gadeke; Freimut
Wurfel; Claus
Mantal; Nils
Kuter; Uwe |
Lubeck
Lubeck
Lubeck
Lubeck
Lubeck |
|
DE
DE
DE
DE
DE |
|
|
Family ID: |
42646487 |
Appl. No.: |
13/641900 |
Filed: |
April 14, 2011 |
PCT Filed: |
April 14, 2011 |
PCT NO: |
PCT/EP11/01899 |
371 Date: |
October 18, 2012 |
Current U.S.
Class: |
204/262 |
Current CPC
Class: |
C01B 3/56 20130101; Y02E
60/366 20130101; C01B 2203/043 20130101; C01B 2203/0465 20130101;
B01D 2256/16 20130101; C01B 2203/145 20130101; C01B 3/506 20130101;
C25B 15/08 20130101; C01B 2203/146 20130101; Y02E 60/36 20130101;
C25B 1/04 20130101; B01D 53/265 20130101; C01B 2203/04
20130101 |
Class at
Publication: |
204/262 |
International
Class: |
C25B 9/08 20060101
C25B009/08 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2010 |
EP |
10004114.4 |
Claims
1. An apparatus for the electrical production of hydrogen from
water, the apparatus comprising: an electrolyzer of the PEM type,
which has an inlet for introducing water and a first outlet for the
hydrogen enriched with water and/or water vapor and produced in the
electrolyzer, as well as a second outlet for oxygen and water; and
a water separation device with an inlet connected to the first
outlet of the electrolyzer by means of a line and with a
gas-carrying outlet leading to a hydrogen removal port in or at the
apparatus, wherein the water separation device comprises a thermal
separation stage.
2. An apparatus in accordance with claim 1, wherein the water
separation stage further comprises a second separation stage
wherein the thermal separation stage is followed by the second
separation stage.
3. An apparatus in accordance with claim 2, wherein the second
separation stage is also a thermal separation stage such that there
are first and second thermal separation stages.
4. An apparatus in accordance with claim 3, further comprising a
common cooling circuit wherein the first and second thermal
separation stages are connected to the common cooling circuit.
5. An apparatus in accordance with claim 2, wherein the second
separation stage has a pressure swing adsorption apparatus.
6. An apparatus in accordance with claim 1, further comprising a
mechanical preseparator between the first outlet of the
electrolyzer and the inlet of the thermal separation stage.
7. An apparatus in accordance with claim 6, wherein the water
separated in the separation stage is introduced into the
preseparator via return lines.
8. An apparatus in accordance with claim 7, wherein the return
lines are provided with shut-off valves and a bypass line, which
bypasses the preseparator and can be shut off by means of a valve,
and wherein gas-carrying inlet and outlet lines of the preseparator
can be shut off by means of valves.
9. An apparatus in accordance with claim 7, wherein the
preseparator is connected to the inlet for introducing water by
means of a line in the form of a return line that can be shut off
by means of a valve.
10. An apparatus in accordance with claim 1, wherein the water
separation device has a water-carrying outlet of at least the first
separation stage, which said outlet is connected to the inlet of
the electrolyzer for returning the water by means of a line at
least from time to time.
11. An apparatus in accordance with claim 1, wherein the thermal
separation stage has an electrically operated cooling
apparatus.
12. An apparatus in accordance with claim 11, wherein the cooling
apparatus comprises an absorber cooling apparatus, a compressor
cooling apparatus or a cooling apparatus operated with Peltier
elements.
13. An apparatus in accordance with claim 1, wherein the separation
stage is designed such that hydrogen arriving from the electrolyzer
and enriched with water and/or hydrogen is cooled to a temperature
below 5.degree. C. and above the freezing point.
14. An apparatus in accordance with claim 2, wherein the second
separation stage is a thermal separation stage, which is designed
such that the hydrogen discharged from the first separation stage
and enriched with water and/or water vapor is cooled to below
0.degree. C.
15. An apparatus in accordance with claim 2, wherein the second
separation stage is a thermal separation stage and is operated
intermittently.
16. An apparatus in accordance with claim 1, wherein hydrogen that
is produced is maintained under a pressure of 20 bar or more.
17. An electrical hydrogen from water production apparatus
comprising: a polymer electrolyte membrane electrolyzer comprising
an electrolyzer body with an electrolyzer inlet for introducing
water, an electrolyzer first outlet for hydrogen enriched with
water and/or water vapor and a second electrolyzer outlet for
oxygen and water; an electrolyzer outlet line; and a water
separator with a separator inlet connected to the electrolyzer
first outlet via said electrolyzer outlet line and with a
gas-carrying outlet leading to a hydrogen removal port, the water
separator comprising a thermal separation stage.
18. An apparatus in accordance with claim 17, wherein said water
separator further comprises another separation stage wherein the
thermal separation stage is followed by the another separation
stage.
19. An apparatus in accordance with claim 18, wherein the another
separation stage is also a thermal separation stage such that there
are first and second thermal separation stages.
20. An apparatus in accordance with claim 19, further comprising a
cooling apparatus cooling the first and second thermal separation
stages.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a United States National Phase
application of International Application PCT/EP2011/001899 and
claims the benefit of priority under 35 U.S.C. .sctn.119 of
European Patent Application EP 10 004114.4-1227 filed Apr. 19,
2010, the entire contents of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention pertains to an apparatus for the
electrical production of hydrogen from water.
BACKGROUND OF THE INVENTION
[0003] The use of electrolyzers for producing hydrogen from water
by means of electric energy belongs to the state of the art. Such
electrolyzers exist in various designs. The present invention
pertains to an apparatus with an electrolyzer of the PEM type
(Polymer Electrolyte membrane), i.e., an electrolyzer that operates
with a proton-permeable polymer membrane. Such electrolyzers are
typically built in so-called stacks in order to achieve the highest
possible gas yield in the smallest possible space. Water is fed on
one side here to each membrane, and splitting into hydrogen and
oxygen takes place by the electrodes, which are arranged on both
sides of the membrane and are supplied with the electrolysis
voltage, and hydrogen is produced on one side of the membrane and
oxygen on the other side, on which the water is fed.
[0004] To guarantee the permeability to protons of the polymer
electrolyte membrane, it is necessary to keep the membrane moist at
all times, which does, however, cause the hydrogen produced to be
also typically provided with water vapor and/or water in the form
of droplets. This water burden being entrained in the hydrogen is
undesired in many industrial applications, and it is therefore to
be removed. For example, the water burden being entrained is thus
to be removed before storage in case of storage of the hydrogen in
the metal hydride storage means commonly used now. Mechanical water
separators are usually insufficient here, because they are unable
to sufficiently free the hydrogen stream of water.
[0005] Arranging a water separation device, which operates
according to the principle of pressure swing adsorption, downstream
of the electrolyzer on the outlet side for drying the hydrogen
therefore belongs to the state of the art. The hydrogen stream,
which leaves the electrolyzer and is enriched with water and water
vapor, is sent now via one or more molecular sieve beds, which bind
the water. However, such binding takes place only as long as the
molecular sieve beds are not saturated. The molecular sieve beds
must therefore be regenerated at regular intervals. Two molecular
sieve beds are therefore provided in practice, and flow takes place
through them alternatingly, and the non-active bed is being
regenerated by being flushed with dried hydrogen in counterflow.
This method is comparatively complicated and impairs especially the
efficiency of the apparatus, because the hydrogen used for the
backwash usually escapes unused. The method reaches its limits
especially with increasing water load in the hydrogen stream, and
these apparatuses, which are known from the state of the art, are
therefore rather ineffective.
SUMMARY OF THE INVENTION
[0006] Against this background, a basic object of the present
invention is to provide an apparatus of this type for the
electrical production of hydrogen from water such that it operates
with the highest possible efficiency for generated dried hydrogen,
i.e., hydrogen freed of a majority of the water.
[0007] The apparatus according to the present invention for the
electrical production of hydrogen from water has an electrolyzer of
the PEM type, i.e., one that operates with a proton-permeable
polymer membrane. This electrolyzer is provided with an inlet for
introducing water and with a first outlet for the hydrogen, which
is enriched with water and/or water vapor and is produced in the
electrolyzer, as well as with a second outlet for oxygen and water.
The apparatus has, moreover, a water separation device, whose inlet
is connected by a line with the first outlet of the electrolyzer
and whose gas-carrying outlet leads to a hydrogen removal port in
or at the apparatus, wherein the water separation device has at
least one thermal separation stage.
[0008] Thus, the basic idea of the present invention is to provide
an electrolyzer with water separation device within the apparatus,
wherein the water separation device has at least one first thermal
separation stage. It is apparent that a mechanical separation
apparatus may be provided as a separator, for example, a cyclone
separator or a gravitational separator, in principle, as part of
the separation apparatus or arranged upstream of the latter. Such a
separation apparatus is not a separation stage in the sense of the
present invention. The water separation device is typically of a
two- or more than two-stage design, the first stage being a thermal
separation stage, in which water is removed from the hydrogen
stream by cooling.
[0009] A hydrogen removal port in the sense of the present
invention is defined not only as a port in the actual sense of the
word but also as a line within or outside the apparatus, which
sends the dried hydrogen to a user or to a storage means. Thus,
such a hydrogen removal port in the apparatus can send hydrogen to
a metal hydride storage means likewise provided in the apparatus
via a line.
[0010] The solution according to the present invention is
especially advantageous because the electrolyzer can be operated at
comparatively high temperature and hence with high efficiency. The
gas losses occurring during pressure swing adsorption are
completely avoided.
[0011] Since the temperature should be as high as possible for
effective operation of the electrolyzer, but, on the other hand,
the proton exchange membrane must always be kept wet, favorable
operating conditions are obtained in terms of efficiency if the
electrolyzer is operated in ranges of 70.degree. C. to 80.degree.
C. or higher. The operating temperature is limited upwardly by the
boiling point of water, which must not be reached under any
circumstances. However, the water load being entrained doubles with
every 11.degree. C. or so. Consequently, if the operating
temperature is increased from 60.degree. C. to 70.degree. C., the
quantity of water to be removed approximately doubles. Such a
quantity of water is unproblematic with the solution according to
the present invention, namely, with a first thermal separation
stage, especially entirely without loss of hydrogen. The
electrolyzer of the apparatus according to the present invention
can thus be operated substantially more effectively, because it is
operated at a higher temperature, without having to accept the
losses known from pressure swing adsorption. By contrast, the
energy to be used for cooling is markedly lower.
[0012] The water is advantageously separated in two stages, but
more than two stages may be provided as well. The second separation
stage is advantageously likewise a thermal separation stage. As an
alternative, the second separation stage may also be formed by a
pressure swing adsorption apparatus. A pressure swing adsorption
apparatus is considered for use as the second stage because only a
small quantity of water is to be removed from the hydrogen here,
but it is important to remove the water as completely as possible.
Since the hydrogen is loaded with small quantities of water only,
the molecular sieve beds can be used for a comparatively long time
before backwash is necessary.
[0013] According to a variant of the present invention, a
water-carrying outlet of at least the first separation stage is
advantageously connected to the inlet of the electrolyzer by means
of a line for returning the water. The connection by means of a
line is brought about at least from time to time, i.e.,
corresponding valves, which can be actuated correspondingly as
needed in order to return the water collected in the first thermal
separation stage to the inlet of the electrolyzer, are provided in
the line. The line pressure occurring in the system within the
apparatus, i.e., the hydrogen pressure, can be used to transport
this water. A bypass line with valve is advantageously to be
provided for this, namely, between the first outlet of the
electrolyzer, i.e., the hydrogen-carrying outlet, and the separator
to be emptied, bypassing the separator or separators located in
between.
[0014] An inlet of the electrolyzer is defined in the sense of the
present invention as any water-carrying line leading thereto, which
is fed, for example, from a reservoir within or outside the
apparatus. This water can consequently be returned either into this
line or advantageously into the reservoir.
[0015] A mechanical preseparator, for example, a gravitational
water separator or a cyclone type water separator, is
advantageously arranged between the electrolyzer and the first
thermal separation stage. Part of the water load being entrained
can be separated nearly without loss in such a preseparator. It is
especially advantageous in this connection to integrate the
preseparator in terms of the lines such that it can also be used at
the same time to receive the water returned from the separation
stages. The preseparator can be advantageously shut off for this
both on the inlet side and the outlet side of its gas-carrying
lines by means of valves and can be bypassed via a bypass line,
which can likewise be shut off by means of a valve. When the return
lines of the separation stages, which can likewise be shut off by
means of valves, open again into the preseparator, the water to be
returned can be pressed by means of the pressure present anyway in
the hydrogen line into the preseparator by shutting off the
gas-carrying lines of the preseparator and opening the bypass line
when the valves in the return lines are opened. It is unproblematic
here if the gas enters the preseparator in the form of hydrogen
through the return lines, because this gas can again be fed later
into the separation stages.
[0016] The preseparator likewise has a return line, which can be
shut off by means of a valve and via which the water collected in
the preseparator can be fed to the inlet of the electrolyzer or to
the water tank arranged upstream of it. By using a float valve at
the bottom of the preseparator, the return of the water can take
place quasi automatically insofar as the shut-off valve in the
return line leading to the water tank is opened.
[0017] The thermal separation stage or thermal separation stages
is/are advantageously provided with an electrically operated,
common cooling apparatus. Such cooling apparatuses are available
relatively cost-effectively and in a compact form. A compressor
type cooling apparatus is advantageously used in case of larger
apparatuses. An absorber cooling device or a cooling device
operating with Peltier elements may also be used as an alternative,
especially in case of smaller apparatuses. It is especially
advantageous if the first thermally operating separation stage is
designed such that the hydrogen arriving from the electrolyzer that
is enriched with water and/or water vapor is cooled to a
temperature just slightly above the freezing point, i.e.,
preferably between 0.degree. C. and 5.degree. C. A majority of the
water being entrained in the hydrogen stream condenses in this
temperature range. The residual water load in the hydrogen is
comparatively small. Since cooling takes place above the freezing
point, no special precautionary measures are to be taken in respect
to ice formation concerning the removal of the condensed water.
[0018] Cooling to below 0.degree. C. and preferably to below
-35.degree. C. advantageously takes place only in the second
separation stage of the hydrogen stream. The water being entrained
in the hydrogen is crystallized in the form of ice, typically on
the heat exchanger walls, in this temperature range. These walls
must therefore be deiced from time to time, which can be guaranteed
by intermittent operation. Since such apparatuses are never
operated typically for longer than 12 hours at a stretch, it is not
usually necessary to interrupt the operation in case of suitable
design of the cooling surfaces for the purpose of deicing, and it
is sufficient, instead, for the apparatus to thaw by itself after
being switched off during the pause between operations, for
example, during the night. If, by contrast, the apparatus is to be
designed for a quasi continuous, 24-hour operation, it is either
necessary to provide for a thawing cycle for the second thermal
separation stage, which may optionally be supported by an electric
heater, or to provide two thermal separation stages in parallel
operation, which are operated alternatingly.
[0019] The apparatus according to the present invention operates
especially effectively if the electrolyzer, the water separation
device as well as any auxiliary units, connection lines, valves and
the like that may be present are designed such that the hydrogen is
generated and maintained under a pressure of 20 bar or higher,
preferably about 30 bar. Operation of the apparatus with this
pressure is especially advantageous because no special pressure
increase is necessary in this case for storing the hydrogen in
metal hydride storage means. The apparatus releases the dry
hydrogen with the necessary pressure.
[0020] The present invention will be explained in more detail below
on the basis of the exemplary embodiment shown in the drawings. The
various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming
a part of this disclosure. For a better understanding of the
invention, its operating advantages and specific objects attained
by its uses, reference is made to the accompanying drawings and
descriptive matter in which preferred embodiments of the invention
are illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The only FIGURE shows a diagram of an embodiment variant of
the apparatus according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Referring to the drawings in particular, the apparatus shown
in the FIGURE is arranged in an essentially closed housing, not
shown, but it does not necessarily have to be so designed, but,
especially if it is integrated in an instillation, its components
may be integrated in the instillation.
[0023] The apparatus has an electrolyzer 1 of the PEM type, which
is usually designed as a stack, but it may be designed in any other
suitable form as well. The electrolyzer has an inlet 2 for the
introduction of water. A first outlet 3 of the electrolyzer 1 is
provided for removing the hydrogen produced in electrolyzer 1,
which typically contains water and water vapor. Furthermore,
electrolyzer 1 has a second outlet 4, which is provided for
removing the oxygen formed in electrolyzer 1.
[0024] In the embodiment shown, the apparatus has a reservoir 5 in
the form of a water tank, which is connected to the inlet 2 of the
electrolyzer via a pump 6 by means of a water line. The second
outlet 4 opens via a line in the upper area of the water tank 5.
The first outlet 3, i.e., the water-carrying outlet 3, of
electrolyzer 1 is connected by means of a line to a water
separation device 7.
[0025] The water separation device 7 has a gravitational water
separator 8, whose gas-carrying line 9 with connected to a first
thermal separation stage 10 by means of a line. In this first
thermal separation stage 10, which is formed from a closed
container 11 with a coolant line 12 integrated therein, the
water-containing hydrogen stream arriving from the gravitational
water separator 8 is cooled to a temperature of about 4.degree. C.
The coolant line 12 is designed as an evaporator in the area of
container 11. A condenser is provided outside the container. These
components are connected to form a cooling circuit in the manner
known per se via a throttling site and a compressor. The water
condensed at the evaporator 12 collects at the bottom of container
11.
[0026] The gas leaving the first thermal separation stage 10 enters
via a line 13 a second thermal separation stage 14 via a line 13.
The second thermal separation stage 14 is provided with two
containers 15 with provided as evaporators 16 in the form of
coolant lines arranged in the two containers 15. The coolant lines
of the evaporators 16 have the same design as described for the
first thermal separation stage 10 and are connected to a condenser.
The cooling circuits have a compressor and a condenser each for all
evaporators 16 together and a throttling site and are intended for
alternating operation. The separation stages 10 and 14 may be
advantageously fed via a common cooling circuit, so that only one
compressor is necessary, and the different temperatures are set
each by means of the associated throttling sites.
[0027] The hydrogen with the residual water still being entrained
with it is cooled to -36.degree. C. in this second thermal
separation stage 14. The remaining residual water resublimes or
solidifies now on the evaporator 16. The hydrogen leaving the
second thermal separation stage 14 is available at the hydrogen
removal port 17 and is dry, i.e., practically water-free. The
containers 15 can be operating alternatingly via outlet-side valves
18, i.e., one of the containers is used for cooling while the other
container is thawed and the water collecting at the bottom of the
container is sent into the gravitational water separator 8 via a
line 20, which can likewise be shut off by means of a valve 19.
Valve 19 in a return line 20 is opened only briefly each time, and
valve 18 belonging to the container 15 on the outlet side is
actuated for shutting off until the thawed water is returned from
container 15 into the gravitational water separator 8.
[0028] A corresponding means is provided for container 11, and the
water can be transferred from container 11 into the gravitational
water separator 8 via the line 21 connected there on the bottom
side and the downstream shut-off valve 22. The gravitational water
separator 8 is to be bypassed for this via a bypass line 23 and to
be shut off by means of the valves 24 and 25, so that after opening
a valve 26 in bypass line 23, pressure is admitted to container 11
and the water present on the bottom is pressed via line 21 into the
gravitational water separator 8. As an alternative, this return
line may also open directly into water tank 5.
[0029] A water return line 27, which can be connected to water tank
5 via a valve 28, adjoins the bottom of the gravitational water
separator 8 in this exemplary embodiment. The water separated in
the water separation device 7 is consequently returned completely
into the water tank 5. The apparatus is typically operated such
that the hydrogen is available with a pressure of 20-30 bar on the
outlet side of the electrolyzer. The electrolyzer is operated now
at a temperature between 70.degree. C. and 80.degree. C.
[0030] While specific embodiments of the invention have been shown
and described in detail to illustrate the application of the
principles of the invention, it will be understood that the
invention may be embodied otherwise without departing from such
principles.
* * * * *