U.S. patent application number 15/591113 was filed with the patent office on 2017-11-23 for starting method of high-pressure water electrolysis system and starting method of water electrolysis system.
This patent application is currently assigned to HONDA MOTOR CO., LTD.. The applicant listed for this patent is HONDA MOTOR CO., LTD.. Invention is credited to Hayato DAIMON, Hiroyuki ISHIKAWA.
Application Number | 20170335469 15/591113 |
Document ID | / |
Family ID | 60330453 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170335469 |
Kind Code |
A1 |
ISHIKAWA; Hiroyuki ; et
al. |
November 23, 2017 |
STARTING METHOD OF HIGH-PRESSURE WATER ELECTROLYSIS SYSTEM AND
STARTING METHOD OF WATER ELECTROLYSIS SYSTEM
Abstract
A starting method includes determining whether a depressurizing
current was supplied to a water electrolyzer while at least a
cathode side of the water electrolyzer was depressurized in an
immediately previous stop of a water electrolysis system after
electrolyzing water. A first current is supplied to the water
electrolyzer at a first supply rate to start the water electrolysis
system in a case where it is determined that the depressurizing
current was supplied to the water electrolyzer in the immediately
previous stop. A second current is supplied to the water
electrolyzer at a second supply rate lower than the first supply
rate to start the water electrolysis system in a case where it is
determined that the depressurizing current was not supplied to the
water electrolyzer in the immediately previous stop.
Inventors: |
ISHIKAWA; Hiroyuki; (Wako,
JP) ; DAIMON; Hayato; (Wako, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA MOTOR CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
HONDA MOTOR CO., LTD.
Tokyo
JP
|
Family ID: |
60330453 |
Appl. No.: |
15/591113 |
Filed: |
May 10, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 60/366 20130101;
C25B 15/02 20130101; C25B 1/12 20130101; Y02E 60/36 20130101 |
International
Class: |
C25B 1/12 20060101
C25B001/12; C25B 15/02 20060101 C25B015/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2016 |
JP |
2016-098866 |
Claims
1. A starting method of a high-pressure water electrolysis system
that includes a high-pressure water electrolysis device which
electrolyzes supplied water, produces oxygen on an anode side, and
produces hydrogen at a higher pressure than the oxygen on a cathode
side, the starting method comprising: a step of determining whether
or not depressurization on at least the cathode side is performed
while a depressurizing current is applied in a previous stop of the
high-pressure water electrolysis system; a step of performing
starting by applying a starting current to the high-pressure water
electrolysis device at a normal current application rate in a case
where a determination is made that an electrolysis depressurization
process, in which depressurization is performed while the
depressurizing current is applied, is performed in the previous
stop; and a step of performing the starting by applying the
starting current to the high-pressure water electrolysis device at
a current application rate that is lower than the normal current
application rate in a case where a determination is made that an
electroless depressurization process, in which depressurization is
performed while the depressurizing current is not applied, is
performed in the previous stop.
2. The starting method according to claim 1, wherein before
starting applying the starting current to the high-pressure water
electrolysis device, water is caused to circulate only in a
prescribed time in which an inside of the high-pressure water
electrolysis device is filled with the water.
3. The starting method according to claim 1, further comprising: a
step of detecting a hydrogen concentration in a fluid that is
discharged from the anode side of the high-pressure water
electrolysis device while the starting current is applied to the
high-pressure water electrolysis device at the current application
rate; and a step of raising a starting current value of a current
that is applied to the high-pressure water electrolysis device to a
rated current value in a case where the detected hydrogen
concentration becomes a prescribed value or lower.
4. The starting method according to claim 1, wherein as a start
pressure of the electroless depressurization process is higher, the
current application rate is set lower.
5. A starting method of a water electrolysis system including a
water electrolyzer, the starting method comprising: determining
whether a depressurizing current was supplied to the water
electrolyzer while at least a cathode side of the water
electrolyzer was depressurized in an immediately previous stop of
the water electrolysis system after electrolyzing water to produce
oxygen with a first pressure on an anode side and hydrogen with a
second pressure higher than the first pressure on the cathode side;
supplying a first current to the water electrolyzer at a first
supply rate to start the water electrolysis system in a case where
it is determined that the depressurizing current was supplied to
the water electrolyzer in the immediately previous stop; and
supplying a second current to the water electrolyzer at a second
supply rate lower than the first supply rate to start the water
electrolysis system in a case where it is determined that the
depressurizing current was not supplied to the water electrolyzer
in the immediately previous stop.
6. The starting method according to claim 5, wherein before
starting supplying the first or second current to the electrolyzer,
water is caused to circulate only in a prescribed time in which an
inside of the electrolyzer is filled with the water.
7. The starting method according to claim 5, further comprising:
detecting a hydrogen concentration in a fluid that is discharged
from the anode side while the first or second current is supplied
to the electrolyzer; and raising a starting current value of a
current that is applied to the electrolyzer to a rated current
value in a case where the detected hydrogen concentration becomes a
prescribed value or lower.
8. The starting method according to claim 5, wherein as a start
pressure of an electroless depressurization process is higher, the
first supply rate or the second supply rate is set lower.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to Japanese Patent Application No. 2016-098866, filed May
17, 2016, entitled "Starting Method of High-pressure Water
Electrolysis System." The contents of this application are
incorporated herein by reference in their entirety.
BACKGROUND
1. Field
[0002] The present disclosure relates to a starting method of a
high-pressure water electrolysis system and a starting method of a
water electrolysis system.
2. Description of the Related Art
[0003] In general, hydrogen is used as fuel gas for power
generation in a fuel cell. Hydrogen is produced by a water
electrolysis system that incorporates a water electrolysis device,
for example. The water electrolysis device produces hydrogen (and
oxygen) by electrolyzing water and thus uses a solid polymer
electrolyte membrane (ion exchange membrane).
[0004] Electrode catalyst layers are provided on both sides of an
electrolyte membrane, and an electrolyte-membrane-electrode
structure is thereby configured. Further, power feeders are
disposed on both sides of the electrolyte-membrane-electrode
structure, and a water electrolysis cell is thereby configured.
[0005] Here, in the water electrolysis device in which plural water
electrolysis cells are laminated, a voltage is applied to both ends
in a laminating direction, and water is supplied to an anode power
feeder. Thus, on an anode side of the
electrolyte-membrane-electrode structure, water is decomposed, and
hydrogen ions (protons) are generated. The hydrogen ions permeate
the solid polymer electrolyte membrane and move to a cathode side
and are bonded to electrons to produce hydrogen in a cathode power
feeder.
[0006] The hydrogen led out from the water electrolysis device is
delivered to a gas-liquid separation device, and liquid water is
removed. Subsequently, the hydrogen is supplied to a hydrogen
purification unit (water adsorption unit), and product hydrogen
(dry hydrogen) is obtained. Meanwhile, on the anode side, oxygen
generated together with the hydrogen is discharged from the water
electrolysis device while accompanying excess water.
[0007] As the water electrolysis device, a high-pressure water
electrolysis device (differential pressure type water electrolysis
device) may be employed which generates hydrogen at a high pressure
(in general, 1 MPa or higher) on the cathode side. In the
high-pressure water electrolysis device, while high-pressure
hydrogen is filled in a fluid path of a cathode separator across
the electrolyte membrane, water and oxygen at a normal pressure are
present in a fluid path of an anode separator. Accordingly, in a
case of an operation stop (an end of supply of generated hydrogen),
the pressure difference between both sides of the electrolyte
membrane has to be removed in order to protect the electrolyte
membrane.
[0008] Accordingly, in related art, Japanese Unexamined Patent
Application Publication No. 2010-236089 discloses an operation stop
method of a water electrolysis device, for example. This operation
stop method includes a step of applying a voltage after supply of
hydrogen from a cathode-side electrolysis chamber is stopped and a
step of performing depressurization of at least the cathode-side
electrolysis chamber in a state where the voltage is applied.
Japanese Unexamined Patent Application Publication No. 2010-236089
discusses that because this electrolysis depressurization process
causes hydrogen that leaks from the cathode side to an anode side
to return to the cathode side by a hydrogen membrane pump effect,
and stagnation of leaked high-pressure hydrogen may be restrained,
and degradation of a catalyst electrode due to hydrogen may be
inhibited.
SUMMARY
[0009] According to one aspect of the present invention, a starting
method of a high-pressure water electrolysis system that includes a
high-pressure water electrolysis device which electrolyzes supplied
water, produces oxygen on an anode side, and produces hydrogen at a
higher pressure than the oxygen on a cathode side, the starting
method includes a step of determining whether or not
depressurization on at least the cathode side is performed while a
depressurizing current is applied in a previous stop of the
high-pressure water electrolysis system. The starting method
includes a step of performing starting by applying a starting
current to the high-pressure water electrolysis device at a normal
current application rate in a case where a determination is made
that an electrolysis depressurization process, in which
depressurization is performed while the depressurizing current is
applied, is performed in the previous stop. The starting method
includes a step of performing the starting by applying the starting
current to the high-pressure water electrolysis device at a current
application rate that is lower than the normal current application
rate in a case where a determination is made that an electroless
depressurization process, in which depressurization is performed
while the depressurizing current is not applied, is performed in
the previous stop.
[0010] According to another aspect of the present invention, a
starting method of a water electrolysis system including a water
electrolyzer, the starting method includes determining whether a
depressurizing current was supplied to the water electrolyzer while
at least a cathode side of the water electrolyzer was depressurized
in an immediately previous stop of the water electrolysis system
after electrolyzing water to produce oxygen with a first pressure
on an anode side and hydrogen with a second pressure higher than
the first pressure on the cathode side. A first current is supplied
to the water electrolyzer at a first supply rate to start the water
electrolysis system in a case where it is determined that the
depressurizing current was supplied to the water electrolyzer in
the immediately previous stop. A second current is supplied to the
water electrolyzer at a second supply rate lower than the first
supply rate to start the water electrolysis system in a case where
it is determined that the depressurizing current was not supplied
to the water electrolyzer in the immediately previous stop.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings.
[0012] FIG. 1 is a schematic configuration explanatory diagram of a
high-pressure water electrolysis system that employs a starting
method according to this embodiment of the present disclosure.
[0013] FIG. 2 is a flowchart for explaining the starting
method.
[0014] FIG. 3 is a timing diagram for explaining the starting
method.
[0015] FIG. 4 is a timing diagram of a case where a normal current
application rate is employed in the starting method.
DESCRIPTION OF THE EMBODIMENTS
[0016] The embodiments will now be described with reference to the
accompanying drawings, wherein like reference numerals designate
corresponding or identical elements throughout the various
drawings.
[0017] As illustrated in FIG. 1, a high-pressure water electrolysis
system 10 according to an embodiment of the present disclosure
includes a high-pressure water electrolysis device 12. The
high-pressure water electrolysis device 12 electrolyzes water (pure
water) and thereby produces oxygen and high-pressure hydrogen (at a
higher pressure than an oxygen pressure that is a normal pressure,
for example, hydrogen at 1 to 80 MPa).
[0018] In the high-pressure water electrolysis device 12, plural
water electrolysis cells 14 are laminated, and end plates 16a and
16b are disposed at both ends in a laminating direction of the
water electrolysis cell 14. An electrolysis power source 18 that is
a direct current power source is connected with the high-pressure
water electrolysis device 12. A water supply line 20 that
communicates with an anode inlet side (water supply inlet side),
which is not illustrated, is connected with the end plate 16a.
[0019] A water discharge line 22 that communicates with an anode
outlet side (water and generated oxygen discharge side) and a
hydrogen lead-out line 24 that communicates with a cathode side
(high-pressure hydrogen generating side) are connected with the end
plate 16b. Oxygen that is generated by a reaction (and permeating
hydrogen) and unreacted water are discharged to the water discharge
line 22.
[0020] The water supply line 20, on which a circulating water pump
26 and a cooling apparatus 27 are arranged, is connected with a
bottom portion of an oxygen gas-liquid separation apparatus 28. An
air blower 30 and the water discharge line 22 communicate with an
upper portion of the oxygen gas-liquid separation apparatus 28. A
pure water supply line 34 that is connected with a pure water
producing device 32 and a gas discharge line 36 for discharging
oxygen and hydrogen that are separated from the pure water by the
oxygen gas-liquid separation apparatus 28 is coupled with the
oxygen gas-liquid separation apparatus 28.
[0021] The hydrogen lead-out line 24 connects the high-pressure
water electrolysis device 12 with a high-pressure hydrogen
gas-liquid separation apparatus 38. High-pressure hydrogen from
which water is removed by the high-pressure hydrogen gas-liquid
separation apparatus 38 is led out to a high-pressure hydrogen
supply line 40. The high-pressure hydrogen supply line 40 is
provided with a back pressure valve 42 that is set to a
predetermined pressure value (for example, 70 MPa).
[0022] A water draining line 46 that discharges liquid water
separated by the high-pressure hydrogen gas-liquid separation
apparatus 38 is connected with a lower portion of the high-pressure
hydrogen gas-liquid separation apparatus 38. On the water draining
line 46, a first solenoid valve 48 and a drained water
depressurization mechanism that applies pressure loss and thereby
causes the liquid water of a set water amount to flow through, for
example, an orifice 50 are disposed along a flow direction of the
liquid water. Instead of the orifice 50, a reducing valve may be
used, for example.
[0023] The water draining line 46 is connected with a low-pressure
gas-liquid separation apparatus 52, which performs gas-liquid
separation of the liquid water at a lowered pressure, in a
downstream portion of the orifice 50. The low-pressure gas-liquid
separation apparatus 52 and the oxygen gas-liquid separation
apparatus 28 are connected together by a water returning line 56. A
second solenoid valve 58 is disposed on the water returning line
56.
[0024] An upper side of the high-pressure hydrogen gas-liquid
separation apparatus 38 and an upper side of the low-pressure
gas-liquid separation apparatus 52 are connected together by a
pressure releasing line 60 that discharges gas (hydrogen) separated
in the low-pressure gas-liquid separation apparatus 52. On the
pressure releasing line 60, a depressurization mechanism, for
example, a reducing valve 62 and a third solenoid valve 64 are
disposed along a high-pressure hydrogen flow direction.
[0025] On the water discharge line 22, a hydrogen sensor 66 that
detects the hydrogen concentration in discharged fluids (oxygen,
hydrogen, and water vapor) is disposed. Detection results that are
obtained by the hydrogen sensor 66 are transmitted to a controller
68, and the controller 68 performs operation control of the whole
high-pressure water electrolysis system 10.
[0026] An action of the high-pressure water electrolysis system 10
configured as described above will be described below.
[0027] First, in a case of a starting operation of the
high-pressure water electrolysis system 10, pure water that is
generated from city water via the pure water producing device 32 is
supplied to the oxygen gas-liquid separation apparatus 28. Then, by
work of the circulating water pump 26, the pure water in the oxygen
gas-liquid separation apparatus 28 is supplied to the anode inlet
side of the high-pressure water electrolysis device 12 via the
water supply line 20. Meanwhile, a voltage is applied to the
high-pressure water electrolysis device 12 via the electrolysis
power source 18 that is electrically connected therewith, and the
electrolytic current is applied to the high-pressure water
electrolysis device 12.
[0028] Thus, in each of the water electrolysis cells 14, pure water
is decomposed by electricity on the anode side, and hydrogen ions,
electrons, and oxygen are generated. Accordingly, on the cathode
side, hydrogen is obtained by bonding of hydrogen ions to
electrons, and the hydrogen is taken out to the hydrogen lead-out
line 24.
[0029] Meanwhile, on the anode outlet side, the oxygen generated by
the reaction, the unreacted water, and the permeated hydrogen
dynamically flow, and those mixed fluids are discharged to the
water discharge line 22. The unreacted water, oxygen, and hydrogen
are introduced to the oxygen gas-liquid separation apparatus 28 and
separated. Subsequently, the water is introduced to the water
supply line 20 via the circulating water pump 26. The oxygen and
hydrogen that are separated from the water are discharged from the
gas discharge line 36 to the outside.
[0030] Hydrogen generated in the high-pressure water electrolysis
device 12 is delivered to the high-pressure hydrogen gas-liquid
separation apparatus 38 via the hydrogen lead-out line 24. In the
high-pressure hydrogen gas-liquid separation apparatus 38, the
liquid water contained in hydrogen is separated from the hydrogen
and stored. Meanwhile, the hydrogen is led out to the high-pressure
hydrogen supply line 40. The pressure of the hydrogen is raised to
a set pressure (for example, 70 MPa) of the back pressure valve 42.
Subsequently, the hydrogen is dehumidified by a dehumidifying
device or the like, which is not illustrated, becomes dry hydrogen
(product hydrogen), and is supplied to a fuel cell electric vehicle
or the like.
[0031] Next, in a case where an electrolysis operation of the
high-pressure water electrolysis system 10 is stopped, the
controller 68 starts a pressure releasing process of the
high-pressure water electrolysis device 12. Specifically, because
the third solenoid valve 64 is opened, the high-pressure hydrogen
that is filled on the cathode side is depressurized while passing
from the hydrogen lead-out line 24 through the pressure releasing
line 60 and is subsequently discharged to the low-pressure
gas-liquid separation apparatus 52.
[0032] In this case, an electrolytic current that is lower than the
above electrolytic current (hereinafter also referred to as
depressurizing current) is applied by the electrolysis power source
18 (electrolysis depressurization process). The depressurizing
current is set to a minimum current value by which a membrane pump
effect is obtained, for example.
[0033] Then, in a case where the hydrogen pressure on the cathode
side becomes the same pressure as the pressure (normal pressure) on
the anode side, voltage application by the electrolysis power
source 18 is stopped. Accordingly, the operation of the
high-pressure water electrolysis system 10 is stopped.
[0034] Next, a starting method of the high-pressure water
electrolysis system 10 according to the embodiment of the present
disclosure will be described along a flowchart illustrated in FIG.
2.
[0035] The controller 68 determines whether the above electrolysis
depressurization process is preformed or the electroless
depressurization process is performed in the previous operation
stop of the high-pressure water electrolysis system 10 (step S1).
The electroless depressurization process is a process for
depressurization without performing application of the electrolytic
current in a case where abnormality occurs in an operation of the
high-pressure water electrolysis system 10 and an emergency stop of
the high-pressure water electrolysis system 10 is performed.
[0036] In a case where the controller 68 determines that the
electroless depressurization process is performed in the previous
operation stop of the high-pressure water electrolysis system 10
(YES in step S1), the process moves to step S2. In step S2, water
is caused to circulate for only a prescribed time (for example, 5
seconds) after the circulating water pump 26 is driven (ON). That
is, before starting applying a starting current (electrolytic
current) to the high-pressure water electrolysis device 12, an
inside of the high-pressure water electrolysis device 12 is filled
with water.
[0037] Further, moving to step S3, the application of the starting
current to the high-pressure water electrolysis device 12 is
started at a prescribed current application rate (for example, 0.5
A/second) (hereinafter also referred to as corrected current
application rate). The corrected current application rate is set to
a lower rate than the current application rate (hereinafter also
referred to as normal current application rate) in a case where the
electrolysis depressurization process is performed in the previous
operation stop (NO in step S1). Here, the current application rate
represents a current raising rate (change rate) in a case where the
staring current is raised to a rated current value.
[0038] As illustrated in FIG. 3, in a case where the emergency stop
of the high-pressure water electrolysis system 10 is performed,
because depressurization by membrane permeation is performed
without water circulation, hydrogen is likely to stagnate on the
anode side. Accordingly, the starting current is applied to the
high-pressure water electrolysis device 12 at the corrected current
application rate when the high-pressure water electrolysis system
10 is started, and the hydrogen concentration of the fluid that is
discharged to the water discharge line 22 of the high-pressure
water electrolysis device 12 may thereby be suppressed to a certain
concentration or lower. Here, the certain concentration is a
concentration of 1%, for example.
[0039] That is, the oxygen amount that is generated from the
high-pressure water electrolysis device 12 in the starting at a
time after the electroless depressurization process is reduced
compared to the oxygen amount that is produced in the normal
starting at a time after the electrolysis depressurization process.
Thus, the hydrogen that stagnates on the anode side due to the
electroless depressurization process is not discharged from the
high-pressure water electrolysis device 12 at one time.
Accordingly, in this embodiment, effects of enabling the hydrogen
concentration in the discharged fluid to be suppressed to the
certain value or lower and enabling an efficient high-pressure
water electrolysis process to be certainly achieved are
obtained.
[0040] Meanwhile, FIG. 4 illustrates a starting method of applying
the starting current to the high-pressure water electrolysis device
12 at the normal current application rate in the starting in a case
where the electroless depressurization process is performed in the
previous operation stop. Accordingly, because oxygen that is
produced from the high-pressure water electrolysis device 12 in the
starting is much, the hydrogen concentration in the fluid that is
discharged from the anode side temporarily rises and becomes a
concentration exceeding 1%, for example, and the stop of starting
may be caused.
[0041] As illustrated in FIG. 3, in a case where the starting
current is applied to the high-pressure water electrolysis device
12 at the corrected current application rate, the hydrogen
concentration of the hydrogen discharged from the high-pressure
water electrolysis device 12 temporarily rises and subsequently
drops. In a case where the hydrogen concentration becomes lower
than a predetermined concentration (for example, 0.2%) after a
prescribed time elapses or the hydrogen concentration temporarily
rises (YES in step S4), the process moves to step S5. In step S5,
the starting current value is raised to the rated current value at
the normal current application rate for the high-pressure water
electrolysis device 12. Thus, a high-pressure water electrolysis
operation by the high-pressure water electrolysis system 10 is
started.
[0042] Further, in this embodiment, before starting applying the
starting current (electrolytic current) to the high-pressure water
electrolysis device 12, the water is caused to circulate only in
the prescribed time (for example, 5 seconds) in which the inside of
the high-pressure water electrolysis device 12 is filled with the
water. Accordingly, a case where the hydrogen concentration rises
may properly be handled.
[0043] In addition, while the starting current is applied to the
high-pressure water electrolysis device 12 at the corrected current
application rate that is lower than the normal current application
rate, the hydrogen concentration in the fluid discharged from the
anode side of the high-pressure water electrolysis device 12 is
detected. Further, in a case where the detected hydrogen
concentration becomes a prescribed value or lower, the starting
current value of the current that is applied to the high-pressure
water electrolysis device 12 is raised to the rated current value.
Accordingly, it is possible to quickly raise the pressure of
hydrogen generated by the high-pressure water electrolysis device
12.
[0044] Furthermore, as a start pressure of the electroless
depressurization process is higher in the previous emergency stop,
the current application rate is set lower. The amount of hydrogen
that stagnates on the anode side changes depending on the start
pressure of the electroless depressurization process. Thus, in
accordance with the estimated hydrogen amount that stagnates on the
anode side, the current application value is changed, and it is
thereby possible to certainly suppress the rise of the hydrogen
concentration of the discharged hydrogen and to inhibit an
unnecessary time for the starting from being provided.
[0045] The present disclosure relates to a starting method of a
high-pressure water electrolysis system that includes a
high-pressure water electrolysis device which electrolyzes supplied
water, produces oxygen on an anode side, and produces hydrogen at a
higher pressure than the oxygen on a cathode side.
[0046] This starting method includes a step of determining whether
or not depressurization on at least a cathode side is performed
while a depressurizing current is applied in a previous stop of a
high-pressure water electrolysis system. The starting method
includes a step of performing starting by applying a starting
current to the high-pressure water electrolysis device at a normal
current application rate in a case where a determination is made
that an electrolysis depressurization process, in which
depressurization is performed while the depressurizing current is
applied, is performed in the previous stop.
[0047] The starting method includes a step of performing the
starting by applying the starting current to the high-pressure
water electrolysis device at a current application rate that is
lower than the normal current application rate in a case where a
determination is made that an electroless depressurization process,
in which depressurization is performed while the depressurizing
current is not applied, is performed in the previous stop.
[0048] Further, in the starting method, before starting applying
the starting current to the high-pressure water electrolysis
device, water is preferably caused to circulate only in a
prescribed time in which an inside of the high-pressure water
electrolysis device is filled with the water.
[0049] In addition, the starting method preferably further includes
a step of detecting a hydrogen concentration in a fluid that is
discharged from an anode side of the high-pressure water
electrolysis device while the starting current is applied to the
high-pressure water electrolysis device at the current application
rate. Further, the starting method preferably further includes a
step of raising a starting current value of a current that is
applied to the high-pressure water electrolysis device to a rated
current value in a case where the detected hydrogen concentration
becomes a prescribed value or lower.
[0050] Furthermore, in the starting method, as a start pressure of
the electroless depressurization process is higher, the current
application rate is preferably set lower.
[0051] In the techniques of the present disclosure, in a case where
the electroless depressurization process is performed, the starting
is performed in a state where the current application rate of a
current applied to the high-pressure water electrolysis device is
set lower than the normal current application rate in a case where
a determination is made that depressurization is performed while
the depressurizing current is applied.
[0052] Accordingly, the oxygen amount that is generated in the
starting at a time after the electroless depressurization process
is reduced compared to the oxygen amount that is produced in normal
starting at a time after the electrolysis depressurization process.
Thus, the hydrogen that stagnates on the anode side due to the
electroless depressurization process is not discharged from the
high-pressure water electrolysis device at one time. Accordingly,
the hydrogen concentration in the discharged fluid may be
suppressed to the certain value or lower, and an efficient
differential pressure type water electrolysis process may be
achieved.
[0053] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *