U.S. patent application number 15/325817 was filed with the patent office on 2017-05-25 for electrolysis device.
The applicant listed for this patent is SHARP KABUSHIKI KAISHA. Invention is credited to Nobutoshi ARAI, Nobuhiro HAYASHI, Yasuhiro SAKAMOTO.
Application Number | 20170145571 15/325817 |
Document ID | / |
Family ID | 55162773 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170145571 |
Kind Code |
A1 |
ARAI; Nobutoshi ; et
al. |
May 25, 2017 |
ELECTROLYSIS DEVICE
Abstract
An electrolysis device of the present invention includes an
electrolysis unit. The electrolysis unit includes a channel for
fluid to be treated, at least one electrolysis electrode pair, a
flow inlet, and a flow outlet. The electrolysis electrode pair is
disposed so as to incline with respect to a vertical direction and
includes an upper electrode and a lower electrode disposed so as to
face each other. The channel for fluid to be treated is disposed so
that a fluid that has flowed in from the flow inlet flows through
an interelectrode channel between the upper electrode and the lower
electrode from a lower side to an upper side and flows out from the
flow outlet.
Inventors: |
ARAI; Nobutoshi; (Sakai
City, JP) ; SAKAMOTO; Yasuhiro; (Sakai City, JP)
; HAYASHI; Nobuhiro; (Sakai City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHARP KABUSHIKI KAISHA |
Sakai City, Osaka |
|
JP |
|
|
Family ID: |
55162773 |
Appl. No.: |
15/325817 |
Filed: |
January 28, 2015 |
PCT Filed: |
January 28, 2015 |
PCT NO: |
PCT/JP2015/052357 |
371 Date: |
January 12, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 2301/024 20130101;
C25B 9/06 20130101; C02F 1/46104 20130101; C02F 2001/46185
20130101; C02F 2201/4611 20130101; C02F 2001/46142 20130101; C02F
1/4674 20130101; C25B 9/00 20130101; C02F 2209/29 20130101; C25B
1/26 20130101; C02F 1/4618 20130101; C25B 15/08 20130101; C25B 1/34
20130101 |
International
Class: |
C25B 1/34 20060101
C25B001/34; C25B 15/08 20060101 C25B015/08; C25B 9/00 20060101
C25B009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2014 |
JP |
2014-151839 |
Claims
1. An electrolysis device comprising: an electrolysis unit, wherein
the electrolysis unit includes a channel for fluid to be treated,
at least one electrolysis electrode pair, a flow inlet, and a flow
outlet, the electrolysis electrode pair is disposed so as to
incline with respect to a vertical direction and includes an upper
electrode and a lower electrode disposed so as to face each other,
and the channel for fluid to be treated is disposed so that a fluid
that has flowed in from the flow inlet flows through an
interelectrode channel between the upper electrode and the lower
electrode from a lower side to an upper side and flows out from the
flow outlet.
2. The electrolysis device according to claim 1, wherein the
electrolysis electrode pair is disposed so as to have an
inclination angle of more than 0.degree. and less than 50.degree.
with respect to the vertical direction.
3. The electrolysis device according to claim 1 or 2, wherein the
channel for fluid to be treated includes an upstream-side bent
channel located close to an end of the interelectrode channel on an
upstream side or a downstream-side bent channel located close to an
end of the interelectrode channel on a downstream side.
4. The electrolysis device according to any one of claims 1 to 3,
further comprising means for supplying, by force, a fluid to the
channel for fluid to be treated, wherein the electrolysis electrode
pair is disposed so that an electrode reaction that generates gases
proceeds at the lower electrode and the upper electrode, and an
amount of a gas generated at the lower electrode and released
outside is substantially larger than that of a gas generated at the
upper electrode and released outside.
5. The electrolysis device according to any one of claims 1 to 4,
wherein the upper electrode serves as an anode, and the lower
electrode serves as a cathode.
6. The electrolysis device according to any one of claims 1 to 5,
wherein the lower electrode has an electrode surface area larger
than that of the upper electrode.
7. The electrolysis device according to any one of claims 1 to 6,
further comprising a dilution unit, wherein the fluid is an aqueous
solution, the electrolysis electrode pair is disposed so that a
hypochlorite ion is electrochemically produced from a
chlorine-containing compound contained in the aqueous solution, the
aqueous solution at the flow outlet contains 4000 ppm or more of a
hypochlorite ion on a weight basis, the dilution unit is disposed
so as to produce a diluted solution of the aqueous solution that
contains a hypochlorite ion and is discharged from the flow outlet,
and the diluted solution has a pH of 7.5 or less.
8. The electrolysis device according to any one of claims 1 to 3,
wherein the channel for fluid to be treated is disposed so that a
fluid is supplied to the channel for fluid to be treated by
convection, the electrolysis electrode pair is disposed so that an
electrode reaction that generates gases proceeds at the lower
electrode and the upper electrode, and an amount of a gas generated
at the upper electrode and released outside is substantially larger
than that of a gas generated at the lower electrode and released
outside.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrolysis device and
particularly to a diaphragmless electrolysis device.
BACKGROUND ART
[0002] Electrolysis is practically used for, for example,
production of chemical materials. Basic chemical raw materials such
as sodium hydroxide (caustic soda), chlorine gas, hydrogen gas, and
sodium carbonate (soda ash) are produced by, for example, an
electrolytic soda process. In addition to industrial uses, an
electrolysis technique is also used for home appliances such as an
alkaline ionized water filter.
[0003] The advantage of such an electrolysis technique is that an
active substance can be produced from a harmless material having
almost no activity. For example, hypochlorites such as sodium
hypochlorite is used as a bleaching agent and a germicide for
treating clean and sewage water, for treating a drain, and for
household kitchens and washing. Hypochlorites are produced by a
method in which an alkali hydroxide obtained by electrolysis of an
aqueous solution of an alkali metal chloride, such as a saline
solution, is caused to react with chlorine gas or a method in which
an aqueous solution of an alkali metal chloride is electrolyzed in
a diaphragmless electrolytic cell and an aqueous hypochlorite
solution is produced in the electrolytic cell.
[0004] By the method in which an alkali hydroxide is caused to
react with chlorine gas, a high-concentration aqueous hypochlorite
solution can be obtained. Therefore, when an aqueous hypochlorite
solution is produced for sale, this method is employed. However,
since electrolysis facilities for producing an alkali hydroxide and
chlorine gas are required, this method is performed at a
large-scale electrolysis plant for alkali chlorides such as a
common salt together with the production of an alkali hydroxide or
chlorine gas.
[0005] By the method in which an aqueous solution such as a saline
solution is electrolyzed in a diaphragmless electrolytic cell, an
aqueous hypochlorite solution having a concentration allowable for
direct use for clarification and sterilization of water can be
produced using simple electrolysis facilities. Therefore, this
method is employed at a site where an aqueous hypochlorite solution
is actually used. Furthermore, in the production of the aqueous
hypochlorite solution by electrolysis, the electric current applied
can be adjusted in accordance with the amount of an aqueous
hypochlorite solution required, and all the chlorine component
effective for sterilization or the like is dissolved in water.
Therefore, the method for producing an aqueous hypochlorous acid
solution by electrolysis has an advantage of not requiring storage
and transport of hypochlorites. Thus, the production of an aqueous
hypochlorite solution by electrolysis is performed even at a plant
where a facility for storing liquid chlorine is installed to use
chlorine gas or a plant where a high-concentration aqueous
hypochlorite solution is stored to use an aqueous hypochlorite
solution.
[0006] In the method for producing a hypochlorite by electrolysis
of an aqueous solution of an alkali metal chloride, an anodic
reaction represented by reaction formulae (1) to (3) and a cathodic
reaction represented by reaction formula (4) are believed to
proceed.
2Cl.sup.-.fwdarw.Cl.sub.2+2e.sup.- (1)
Cl.sub.2+H.sub.2O.fwdarw.HCl+HClO (2)
H.sub.2O.fwdarw.1/2O.sub.2+2H.sup.++2e.sup.- (3)
2H.sub.2O+2e.sup.-.fwdarw.H.sub.2+2OH.sup.- (4)
[0007] When the aqueous solution becomes strongly acidic (pH: 3 or
less), the rate of the reaction represented by the reaction formula
(2) decreases, which may result in production of chlorine gas due
to a reverse reaction.
[0008] However, when the concentration of an aqueous hypochlorite
solution produced by electrolysis is low, the concentration of an
organic material contained in water to be treated is sometimes
increased, or an object to be disinfected to which a relatively
large amount of an organic material adheres cannot be sometimes
sufficiently disinfected. A high-concentration aqueous hypochlorite
solution is believed to be produced by a method in which an
electrolysis solution is held between the anode and the cathode for
a long time or a method that uses a multistage electrolysis unit
including a plurality of electrolytic cells each including an anode
and a cathode and disposed with partitions therebetween. However, a
long hold time decreases the production amount per unit time, and
use of multistage electrodes degrades the productivity and
increases the cost. Furthermore, when these methods are employed, a
large amount of hydrogen gas is generated. Consequently, the
contact area between the electrolysis solution and the electrode
decreases as a result of adhesion of air bubbles. Furthermore, the
production efficiency of an electrolysis product decreases and the
concentration of the aqueous hypochlorite solution varies because
of shielding of an electric field or the like.
[0009] Since an acidic aqueous solution with a low hydrogen ion
exponent (pH) has disinfectant properties, the production of an
aqueous hypochlorite solution having a relatively low hypochlorite
concentration and a low pH may be adopted. Thus, an aqueous
hypochlorite solution having sufficient disinfectant properties can
be produced while the required power consumption is reduced.
However, use of such an acidic aqueous hypochlorite solution tends
to generate chlorine gas in addition to hydrogen gas.
[0010] A known production apparatus of an aqueous hypochlorite
solution by electrolysis will be described with reference to FIGS.
15 to 17.
[0011] FIG. 15 schematically illustrates a known electrolysis
device 100 generally used for products obtained with an
electrolysis technique. An electrode pair including a first
electrode 103 and a second electrode 104 is disposed inside a resin
casing 101. A wiring line 106 (pin) for applying a voltage is
connected to the first electrode 103, and a wiring line 107 (pin)
for applying a voltage is connected to the second electrode 104.
Typically, one end of the pin is welded to the electrode and the
other end of the pin is threaded so as to be connected to a wiring
line from a power supply. Although the shape of the casing 101 can
be suitably contrived using an O-ring or the like to prevent liquid
leakage, this contrivance is omitted because it is not directly
related to the present invention. The electrolysis device 100
includes a supply inlet 108 from which a liquid to be treated is
supplied between the electrodes and a discharge outlet 109 from
which a liquid subjected to electrolysis is discharged. Normally,
the electrode pair is disposed in the vertical direction, and the
liquid to be treated is supplied from the lower side.
[0012] In such a configuration, when gas is generated by an
electrolysis reaction and air bubbles are present on the electrode
surface, the air bubbles can be easily removed from the electrode
surface by buoyancy of the air bubbles and flow of the liquid to be
treated. Consequently, a decrease in the area of the electrode
surface on which an electrolysis reaction proceeds can be
suppressed. In such a configuration, however, the flow velocity of
an electrolysis solution around the center of an interelectrode
channel is high, and the flow velocity of an electrolysis solution
around the ends is low. Therefore, the time for which the
electrolysis solution is electrolyzed varies depending on the paths
through which the electrolysis solution flows, which decreases the
production efficiency of an electrolysis product.
[0013] An example of products for which the electrolysis device is
used is an electrolyzed water-producing device 120 in FIG. 16. The
electrolysis device is desirably made compact in size as much as
possible and installed to the electrolyzed water-producing device
120. A casing 111 includes a feed water inlet 112 that can be
connected to a pipe through which water is supplied from a water
supply or another water source under pressure and a discharge
outlet 113 from which the electrolyzed water is discharged. A pipe
through which the electrolyzed water is fed to a supply target can
be connected to the discharge outlet 113. An ON/OFF switch 114 for
the device is also disposed. In addition, an indicator that
displays an operation status and other switches used for various
operations may be suitably disposed, but they are omitted because
they are not directly related to the present invention.
[0014] FIG. 17 schematically illustrates an internal structure of
the electrolyzed water-producing device 120 in FIG. 16. The feed
water inlet 112 and the discharge outlet 113 are connected to each
other through a pipe 115, and a solenoid-controlled valve 116 used
for ON/OFF control may be optionally disposed therebetween. The
pipe 115 includes a portion spatially connected to an outlet of the
electrolysis device 100. An inlet of the electrolysis device 100 is
spatially connected to a raw solution tank 117 through a pipe such
as a tube. A pump 118 for feeding a raw solution by a predetermined
amount is disposed between the electrolysis device 100 and the raw
solution tank 117.
[0015] Next, a fundamental operation of the electrolyzed
water-producing device 120 will be described. When the switch 114
is turned ON, the solenoid-controlled valve 116 is opened and water
is supplied from the feed water inlet 112 to the production device
120 and discharged from the discharge outlet 113 through the pipe
115. The pump 118 is also operated to supply a raw solution stored
in the raw solution tank 117 to the electrolysis device 100. Power
is supplied to the electrolysis device 100 from a power supply (not
illustrated) to electrolyze the raw solution. A high-concentration
electrolyzed water produced by electrolysis is supplied to the pipe
115 and diluted with water flowing through the pipe 115 so as to
have an appropriate concentration. The diluted electrolyzed water
is fed to an electrolyzed water-supplying point through a pipe such
as a hose that is suitably connected to the discharge outlet 113.
When the switch 114 is turned OFF, the power supply to the
solenoid-controlled valve 116, the pump 118, and the electrolysis
device 100 is shut off and the operation is stopped.
[0016] There is also known an electrolytic cell for producing a
hypochlorite which includes a plurality of bipolar unit
electrolytic cells. In this electrolytic cell for producing a
hypochlorite, a cooling room is disposed at an inlet from which an
electrolysis solution flows in or an outlet from which an
electrolysis solution is discharged in each of the unit
electrolytic cells (refer to PTL 1). In this method, a decrease in
the effective electrode area can be prevented, the decrease being
caused by accumulation of generated air bubbles rising to an upper
portion of the electrolysis unit and thus by no immersion of an
upper portion of the electrode with an electrolysis solution. The
electrolysis device (referred to as an electrolytic cell in PTL 1)
in PTL 1 includes a plurality of electrode plates arranged in a
direction perpendicular to a horizontal plane, and a liquid to be
treated is supplied from the lower side to the upper side.
[0017] There is also known a fused-salt electrolytic cell in which
an anode and a cathode are disposed in an electrolytic cell in an
inclined manner, and chlorine gas produced is moved upward and zinc
produced is moved downward (refer to PTL 2).
CITATION LIST
Patent Literature
[0018] PTL 1: Japanese Unexamined Patent Application Publication
No. 6-200393
[0019] PTL 2: Japanese Unexamined Patent Application Publication
No. 2003-328173
SUMMARY OF INVENTION
Technical Problem
[0020] However, such a known electrolysis device poses a problem in
that the production efficiency of an electrolysis product is not
sufficiently high.
[0021] In view of the foregoing, the present invention provides an
electrolysis device capable of efficiently producing an
electrolysis product.
Solution to Problem
[0022] The present invention provides an electrolysis device
including an electrolysis unit. The electrolysis unit includes a
channel for fluid to be treated, at least one electrolysis
electrode pair, a flow inlet, and a flow outlet. The electrolysis
electrode pair is disposed so as to incline with respect to a
vertical direction and includes an upper electrode and a lower
electrode disposed so as to face each other. The channel for fluid
to be treated is disposed so that a fluid that has flowed in from
the flow inlet flows through an interelectrode channel between the
upper electrode and the lower electrode from a lower side to an
upper side and flows out from the flow outlet.
Advantageous Effects of Invention
[0023] According to the present invention, the electrolysis device
includes an electrolysis unit; the electrolysis unit includes a
channel for fluid to be treated, at least one electrolysis
electrode pair, a flow inlet, and a flow outlet; the electrolysis
electrode pair includes an upper electrode and a lower electrode
disposed so as to face each other; and the channel for fluid to be
treated is disposed so that a fluid that has flowed in from the
flow inlet flows through an interelectrode channel between the
upper electrode and the lower electrode and flows out from the flow
outlet. Therefore, when the fluid is caused to flow through the
channel for fluid to be treated and a voltage is applied to the
electrolysis electrode pair, the fluid is electrolyzed to produce
an electrolysis product, and such a fluid containing an
electrolysis product can be continuously produced.
[0024] According to the present invention, the electrolysis
electrode pair is disposed so as to incline with respect to a
vertical direction and the channel for fluid to be treated is
disposed so that a fluid flows through an interelectrode channel
from a lower side to an upper side. Therefore, an electrolysis
product can be efficiently produced. This has been demonstrated
from an experiment conducted by the present inventors and the
like.
[0025] The reason for which an electrolysis product can be
efficiently produced is believed to be as follows.
[0026] In the electrolysis device of the present invention, gas is
generated through an electrode reaction at the lower electrode and
thus air bubbles are generated on the lower electrode. The air
bubbles can be caused to float toward the upper electrode so as to
cross a fluid flowing in the flow direction. As a result of a flow
of the fluid caused by the floating of the air bubbles, a fluid
around the lower electrode and a fluid around the upper electrode
can be stirred and mixed, which facilitates the electrode reaction
at the upper electrode. Furthermore, the movement of a fluid
located upstream of the lower electrode in the direction toward the
upper electrode is facilitated with the movement of the air
bubbles. Therefore, a fluid located downstream of the lower
electrode contains a small fraction of a liquid component subjected
to electrolysis. Thus, the production efficiency of an electrolysis
product can be improved.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIGS. 1(a) and 1(b) are schematic sectional views of an
electrolysis device according to an embodiment of the present
invention. FIG. 1(c) is a diagram for describing an overlap of an
upper electrode and a lower electrode when the electrolysis device
is viewed in a vertical direction A. FIG. 1(d) is a diagram for
describing an overlap of an upper electrode and a lower electrode
when the electrolysis device is viewed in a direction B
perpendicular to a principal surface of the lower electrode.
[0028] FIGS. 2(a) and 2(b) are schematic sectional views of an
electrolysis device according to an embodiment of the present
invention. FIG. 2(c) is a diagram for describing an overlap of an
upper electrode and a lower electrode when the electrolysis device
is viewed in a vertical direction A. FIG. 2(d) is a diagram for
describing an overlap of an upper electrode and a lower electrode
when the electrolysis device is viewed in a direction B
perpendicular to a principal surface of the lower electrode.
[0029] FIG. 3(a) is a schematic sectional view of an electrolysis
device according to an embodiment of the present invention. FIG.
3(b) is a diagram for describing an overlap of an upper electrode
and a lower electrode when the electrolysis device is viewed in a
vertical direction A. FIG. 3(c) is a diagram for describing an
overlap of an upper electrode and a lower electrode when the
electrolysis device is viewed in a direction B perpendicular to a
principal surface of the lower electrode.
[0030] FIG. 4 is a schematic sectional view of an electrolysis
device according to an embodiment of the present invention.
[0031] FIG. 5 is a schematic sectional view of an electrolysis
device produced in an electrolysis experiment.
[0032] FIG. 6(a) is a schematic sectional view of an electrolysis
device according to an embodiment of the present invention. FIGS.
6(b) to 6(d) are schematic sectional views of constituent parts of
the electrolysis device.
[0033] FIGS. 7(a) and 7(b) are schematic sectional views of an
electrolysis device according to an embodiment of the present
invention.
[0034] FIG. 8 is a schematic sectional view of an electrolysis
device according to an embodiment of the present invention.
[0035] FIG. 9(a) is a schematic sectional view of an electrolysis
device according to an embodiment of the present invention. FIGS.
9(b) to 9(f) are schematic sectional views of constituent parts of
the electrolysis device.
[0036] FIGS. 10(a) and 10(b) are schematic views of electrolysis
devices according to an embodiment of the present invention.
[0037] FIG. 11 is a schematic view of an electrolysis device
according to an embodiment of the present invention.
[0038] FIG. 12 is a graph showing the measurement result of an
electrolysis experiment.
[0039] FIG. 13 is a diagram for describing flows of a fluid and air
bubbles in an interelectrode channel.
[0040] FIGS. 14(a) to 14(c) are schematic sectional views of
electrolysis devices produced in an electrolysis experiment.
[0041] FIGS. 15(a) and 15(b) are schematic sectional views of a
known electrolysis device.
[0042] FIG. 16 is a schematic perspective view of a known
electrolyzed water-producing device.
[0043] FIG. 17 schematically illustrates the internal structure of
the known electrolyzed water-producing device.
[0044] FIG. 18 is a graph showing the measurement result of an
electrolysis experiment.
[0045] FIG. 19 is a schematic view of an electrolysis device
produced in an electrolysis experiment.
[0046] FIGS. 20(a) to 20(c) are schematic sectional views of
electrolysis devices according to an embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0047] An electrolysis device of the present invention includes an
electrolysis unit. The electrolysis unit includes a channel for
fluid to be treated, at least one electrolysis electrode pair, a
flow inlet, and a flow outlet. The electrolysis electrode pair is
disposed so as to incline with respect to a vertical direction and
includes an upper electrode and a lower electrode disposed so as to
face each other. The channel for fluid to be treated is disposed so
that a fluid that has flowed in from the flow inlet flows through
an interelectrode channel between the upper electrode and the lower
electrode from a lower side to an upper side and flows out from the
flow outlet.
[0048] In the electrolysis device of the present invention, the
electrolysis electrode pair is preferably disposed so as to have an
inclination angle of more than 0.degree. and less than 50.degree.
with respect to the vertical direction.
[0049] In this configuration, the electrolysis efficiency of the
electrolysis unit can be improved. This has been demonstrated from
an electrolysis experiment conducted by the present inventors and
the like.
[0050] In the electrolysis device of the present invention, the
channel for fluid to be treated preferably includes an
upstream-side bent channel located close to an end of the
interelectrode channel on an upstream side or a downstream-side
bent channel located close to an end of the interelectrode channel
on a downstream side.
[0051] When the channel for fluid to be treated includes an
upstream-side bent channel or a downstream-side bent channel, gas
generated through an electrolysis reaction can be efficiently
discharged from the interelectrode channel, and therefore a
decrease in electrolysis efficiency due to holding of gas can be
suppressed.
[0052] Furthermore, when the channel for fluid to be treated
includes an upstream-side bent channel, a turbulent flow can be
caused on a liquid in the channel for fluid to be treated. By
disposing the bent channel near the electrode, the influence of the
turbulent flow generated in the bent channel is exerted on the
interelectrode channel. This sufficiently produces a stirring
effect from near the inlet of the interelectrode channel where air
bubbles are not so generated. Therefore, the diffusion of a
substance near the electrode surface can be facilitated, and the
electrolysis efficiency can be improved.
[0053] In the case where the channel for fluid to be treated
includes a downstream-side bent channel, even if there is a gas not
sufficiently dissolved at the interelectrode channel, stirring can
be performed again at the bent channel. For example, when an
aqueous solution of a substance containing a chlorine atom is
electrolyzed to produce hypochlorous acid, chlorine gas is not
sufficiently dissolved in the aqueous solution under some
conditions, which sometimes decreases the production efficiency of
hypochlorous acid. In this configuration, however, the dissolution
of chlorine gas in the aqueous solution and the conversion into
hypochlorous acid can be facilitated, and the electrolysis
efficiency can be substantially improved.
[0054] In the electrolysis device of the present invention, the
upper electrode preferably serves as an anode, and the lower
electrode preferably serves as a cathode.
[0055] In this configuration, air bubbles can be generated through
a cathodic reaction at the lower electrode, and the electrolysis
efficiency can be improved by a stirring and mixing effect produced
by the air bubbles.
[0056] In the electrolysis device of the present invention, the
lower electrode preferably has an electrode surface area larger
than that of the upper electrode.
[0057] In the case where an aqueous solution of a substance
containing a chlorine atom is electrolyzed to produce hypochlorous
acid using the lower electrode as a cathode and the upper electrode
as an anode, if the electrode surface of the upper electrode and
the electrode surface of the lower electrode have substantially the
same area, air bubbles of chlorine gas are dissolved and reduced
around the upper electrode by a stirring and mixing effect produced
by air bubbles and thus a decrease in the effective electrode area
due to the air bubbles is suppressed. However, such an effect is
not produced at the lower electrode, and the effective electrode
area is sometimes decreased by air bubbles of hydrogen gas. This
relatively decreases the effective electrode area of the lower
electrode, which is a rate-determining factor of the electrolysis
reaction. Consequently, the area of the upper electrode is
sometimes not effectively utilized.
[0058] By increasing the electrode surface area of the lower
electrode more than the upper electrode, the above phenomenon can
be relaxed. Consequently, the electrode surface area can be
effectively utilized, and the electrolysis efficiency per unit area
of the upper electrode can be improved.
[0059] In the above configuration, when air bubbles of hydrogen gas
generated on the upstream side of the lower electrode come close to
the upper electrode serving as an anode and located above the lower
electrode in the vertical direction, the air bubbles can be brought
into contact with an aqueous solution which has been electrolyzed
on the upstream side of the upper electrode and thus whose pH has
been decreased. Therefore, chlorine gas can be efficiently
converted into hypochlorous acid.
[0060] In the above configuration, even if hydrogen gas generated
at the lower electrode floats on the downstream side with respect
to the vertically upward direction by the velocity of flow of a
liquid, the hydrogen gas comes close to the upper electrode. This
increases the fraction of chlorine gas converted into hypochlorous
acid. In particular, even if an electric field on the downstream
side of the upper electrode is shielded by a large amount of air
bubbles of hydrogen gas generated, the fraction of chlorine gas
converted into hypochlorous acid can be expected to be increased to
some degree by a fringing field to the electrode that extends to
the downstream side or oxidation of air bubbles that have directly
contacted the electrode.
[0061] The electrolysis device of the present invention preferably
further includes a dilution unit. In the electrolysis device,
preferably, the fluid is an aqueous solution, the electrolysis
electrode pair is disposed so that a hypochlorite ion is
electrochemically produced from a chlorine-containing compound
contained in the aqueous solution, the aqueous solution at the flow
outlet contains 4000 ppm or more of a hypochlorite ion on a weight
basis, the dilution unit is disposed so as to produce a diluted
solution of the aqueous solution that contains a hypochlorite ion
and is discharged from the flow outlet, and the diluted solution
has a pH of 7.5 or less.
[0062] In this configuration, an electrolyzed water that contains a
hypochlorite ion and has a pH of 7.5 or less can be efficiently
produced by electrolysis while the release of chlorine gas is
suppressed.
[0063] In the electrolysis device of the present invention,
preferably, the electrolysis unit is disposed so that a
hypochlorite ion is electrochemically produced from the
chlorine-containing compound, the upper electrode serves as an
anode, and the lower electrode serves as a cathode.
[0064] In this configuration, air bubbles of hydrogen gas generated
through a cathodic reaction at the lower electrode move to near the
upper electrode so as to cross a fluid flowing in the flow velocity
direction. Therefore, stirring of a liquid near the anode and a
liquid near the cathode can be facilitated in the electrolysis
unit. Furthermore, alkaline water near the cathode is carried to
near the anode with the movement of air bubbles of hydrogen gas to
near the anode, and chlorine gas generated through an anodic
reaction is brought into contact with an alkalescent aqueous
solution. Thus, the conversation of chlorine gas into hypochlorous
acid or the like can be facilitated.
[0065] In the electrolysis device of the present invention, when
the cross section of the electrolysis unit in a direction in which
the cross-sectional area of the interelectrode channel is the
smallest includes a plane C that includes the upper electrode, but
does not include the lower electrode, a plane D that includes both
the upper electrode and the lower electrode, and a plane E that
includes the lower electrode, but does not include the upper
electrode, the upper electrode and the lower electrode are
preferably disposed so that the plane C is located at the top, the
plane E is located at the bottom, and the plane D is located
between the plane C and the plane E.
[0066] In this configuration, even if air bubbles generated at the
lower electrode are carried away toward the flow outlet with
respect to the vertically upward direction by the flow velocity,
the air bubbles can be brought close to the upper electrode. For
example, in the case where an aqueous solution of a substance
containing a chlorine atom is electrolyzed to produce hypochlorous
acid, even if hydrogen gas generated on the downstream side of the
lower electrode floats on the downstream side with respect to the
vertically upward direction by the velocity of flow of a liquid,
the hydrogen gas can be brought close to the upper electrode
serving as an anode. This increases the fraction of chlorine gas
converted into hypochlorous acid.
[0067] In the electrolysis device of the present invention, the
upper electrode is preferably curved so as to have a projected
shape facing the lower electrode and the lower electrode is
preferably curved so as to have a depressed shape facing the upper
electrode. The radius of curvature of the upper electrode is
preferably smaller than that of the lower electrode.
[0068] In this configuration, air bubbles of chlorine gas or the
like generated at the upper electrode serving as an anode can be
discharged from the center to the end of the electrode. This
suppresses a decrease in the effective electrode area due to the
air bubbles and also improves the electrolysis efficiency at the
center. Furthermore, air bubbles of hydrogen gas or the like
generated at the lower electrode serving as a cathode smoothly move
to near the upper electrode without being interrupted by air
bubbles of chlorine gas or the like. This increases a stirring and
mixing effect produced by air bubbles generated at the lower
electrode. When hypochlorous acid is produced by electrolysis, the
stirring and mixing effect produced by the air bubbles facilities
the conversion of chlorine gas into hypochlorous acid.
Consequently, the amount of air bubbles of chlorine gas can be
decreased, which further suppresses a decrease in the effective
electrode area and further improves the electrolysis
efficiency.
[0069] The movement of the air bubbles from the center to the end
of the upper electrode generates a flow velocity vector in the
direction from the center to the end. This increases the flow
velocity at the center and decreases the flow velocity at the end
compared with known electrode unit structures. Consequently, the
variation in the degree of electrolysis between an electrolysis
solution flowing at the center and an electrolysis solution flowing
at the end can be suppressed.
[0070] Furthermore, the amount of air bubbles at the center of the
upper electrode can be made smaller than that at the end of the
upper electrode. Therefore, the electrolysis efficiency is
increased at the center where the flow velocity tends to be
relatively high. Consequently, the variation in the degree of
electrolysis between an electrolysis solution flowing at the center
and an electrolysis solution flowing at the end can be further
suppressed.
[0071] In the electrolysis device of the present invention, at
least part of the upper electrode is preferably a mesh-like
electrode, and a space is preferably provided on the side
(hereafter, back side) of the upper electrode opposite to the lower
electrode. The electrolysis device of the present invention also
preferably includes an electrode electrically connected to the
upper electrode and disposed on at least part of a wall surface
that defines the space.
[0072] In this configuration, air bubbles on the upper electrode
can be discharged to the back side. This suppresses a decrease in
the effective electrode area caused by covering the surface of the
upper electrode facing the lower electrode with air bubbles and
thus improves the electrolysis efficiency. When hypochlorous acid
is produced by electrolysis, air bubbles of hydrogen gas that have
risen from the lower electrode are less likely to be interrupted by
air bubbles of chlorine gas and can be easily brought into contact
with an aqueous solution generated near the upper electrode and
having a relatively high pH. Therefore, the chlorine gas can be
efficiently converted into hypochlorous acid. In the above
configuration, electrolysis can also be performed at the electrode
disposed on the wall surface through openings of the mesh. This
further increases the effective electrode area.
[0073] In the electrolysis device of the present invention, the
lower electrode is preferably a mesh-like electrode.
[0074] In this configuration, some of air bubbles generated on the
surface of the lower electrode are believed to grow so as to cover
openings of the mesh when viewed from the upper electrode. This
decreases the ratio of an electrode surface area that is
ineffective because of coverage with air bubbles compared with the
case of an electrode having a smooth electrode surface.
[0075] When at least one of the upper electrode and the lower
electrode is a mesh-like electrode, the irregularities of the
electrode surface increase, which makes it difficult to form
laminar flows in the interelectrode channel. Consequently, vortex
flows and turbulent flows are easily formed in the interelectrode
channel, which facilitates the separation of air bubbles from the
electrode. When hypochlorous acid is produced by electrolysis,
minute air bubbles of chlorine gas having a large specific surface
area before the air bubbles grow to large air bubbles are separated
from the electrode and can be brought into contact with an aqueous
solution having a relatively low pH near the upper electrode.
Therefore, the chlorine gas is quickly dissolved and converted into
hypochlorous acid. The stirring of the electrolysis solution is
also facilitated, and thus the dissolution of chlorine gas and the
conversion into hypochlorous acid in the electrolysis unit are
efficiently performed.
[0076] In the electrolysis device of the present invention, an air
bubble guide is preferably disposed between the upper electrode and
the lower electrode. The air bubble guide is a plate-shaped member
disposed away from the upper electrode and the lower electrode. The
plate-shaped member is preferably disposed so as to incline with
respect to a direction parallel to the upper electrode and the
lower electrode. The plate-shaped member is preferably disposed so
as to be substantially perpendicular to the upper electrode and the
lower electrode.
[0077] In this configuration, some of air bubbles generated on the
surface of the lower electrode rise to about the middle, and then
the path of the air bubbles is directly changed by the air bubble
guide or is indirectly changed following a liquid flow changed by
the air bubble guide. This complicates the paths of the air bubbles
compared with the case of no air bubble guide. Furthermore, an
electrolysis solution is stirred by turbulent flows generated on
the rear side of the air bubble guide. The coalescence of air
bubbles can also be suppressed by the air bubble guide, which
increases the solubility of air bubbles. This increases the
probability that air bubbles generated at the lower electrode are
brought into contact with a liquid subjected to electrolysis near
the upper electrode compared with the case of no air bubble guide.
In addition to the air bubbles, an electrolyzed water near the
upper electrode or the lower electrode is also affected by
turbulent flows generated by the air bubble guide. Thus, the
electrolyzed water near the upper electrode or the lower electrode
is also stirred in addition to the air bubbles. This considerably
improves the diffusion controlling in the electrolysis reaction and
also facilities the dissolution of air bubbles because of mixing
and stirring of air bubbles. Consequently, the electrolysis
reaction is facilitated overall and thus the electrolysis
efficiency is improved.
[0078] In the electrolysis device of the present invention,
preferably, the air bubble guide is a columnar member disposed away
from the upper electrode and the lower electrode, and the axis of
the column of the member is substantially parallel to the upper
electrode and the lower electrode.
[0079] In this configuration, the movement of air bubbles and the
flow of a liquid can be prevented from being interrupted more than
necessary. Furthermore, a stirring effect can be produced on the
air bubbles and liquid while a decrease in the effective electrode
area is minimized.
[0080] In the electrolysis device of the present invention,
preferably, the electrolysis unit includes a first electrode holder
to which the lower electrode is fixed, a second electrode holder to
which the upper electrode is fixed, and a spacer disposed between
the first and second electrode holders, and the spacer is disposed
so that at least part of the spacer overlaps the upper electrode
and the lower electrode when viewed in a direction in which the
upper electrode and the lower electrode overlap each other. More
preferably, the first or second electrode holder at least has a
recess to which the electrode is to be fixed, and the distance (the
depth of the recess) between the surface to which the electrode is
fixed and the surface of the spacer is larger than the thickness of
the electrode to be fixed.
[0081] In this configuration, a stirring effect can be produced on
air bubbles and a liquid. Even if the electrode is warped or
loosened for some reason, the probability that both the electrodes
are brought into contact with each other can be decreased. This
improves both the efficiency and safety of the electrolysis device.
Furthermore, the distance between the electrodes can be easily
changed by changing the thickness of the spacer. Therefore, the
specifications can be easily changed in accordance with the
purposes of products, and thus commonality of parts such as an
electrode holder is easily achieved.
[0082] In the electrolysis device of the present invention,
preferably, a protrusion is disposed that protrudes from a surface
parallel to a part of the channel for fluid to be treated and the
surface of the upper electrode or lower electrode, and at least
part of the protrusion is disposed on a symmetry plane in a
structure that defines the channel for fluid to be treated.
[0083] In a known structure, the flow velocity is relatively high
around the center of the interelectrode channel, that is, around
the center of the electrode, and thus the time for which an
electrolysis solution flowing through the center is electrolyzed is
shortened. The flow velocity is relatively low at the end, and thus
the time for which an electrolysis solution flowing through the end
is electrolyzed is lengthened. Consequently, the electrolysis
solution is not uniformly electrolyzed, which causes concentration
unevenness.
[0084] When the electrolysis conditions are set to electrolysis
conditions suitable for an electrolysis solution flowing through
the center, an electrolysis solution flowing through the end is
electrolyzed more than necessary from a certain position or is not
electrolyzed at all, which makes the electrode area ineffective.
When the electrolysis conditions are set to electrolysis conditions
suitable for an electrolysis solution flowing through the end, the
electrolysis solution flowing through the center is not
sufficiently electrolyzed. Electrolysis is not efficiently
performed in either case, but the presence of the protrusion
decreases the flow velocity at the center and increases the flow
velocity at the end in a very simple structure. Therefore, the
occurrence of concentration unevenness can be suppressed and the
electrolysis efficiency can be improved.
[0085] In the electrolysis device of the present invention,
regarding the shape of the channel for fluid to be treated, when
the upper electrode, the lower electrode, the flow inlet, the flow
outlet, and the protrusion are projected in the direction of the
normal to a cross-section taken along a plane parallel to the
electrode surface of the upper electrode or lower electrode, the
widths of the upper electrode and the lower electrode are
preferably relatively large and the widths of the flow inlet, the
flow outlet, and the protrusion are preferably relatively
small.
[0086] In this configuration, the uniformity of the flow velocity
can be improved. This suppresses the concentration unevenness and
improves the electrolysis efficiency.
[0087] In the electrolysis device of the present invention, the
channel for fluid to be treated is preferably disposed so that the
cross-sectional area of a channel near the flow outlet is larger
than that of the interelectrode channel.
[0088] In this configuration, the variation in the flow velocity
near the flow outlet can be suppressed and also the air bubbles are
easily discharged. For example, even if unconverted chlorine gas is
generated in the production of hypochlorous acid, a stirring effect
and a holding effect can be expected in a portion where the
cross-sectional area of a channel is large. Thus, the conversation
of chlorine gas into hypochlorous acid can be expected to be
facilitated. Therefore, an improvement in the efficiency can be
expected.
[0089] In the electrolysis device of the present invention, the
protrusion is preferably disposed on each of the upstream side and
downstream side of the interelectrode channel.
[0090] In the case where the size of the upper electrode and lower
electrode is large particularly in the flow velocity direction, for
example, when the protrusion is present on the upstream side and is
not present on the downstream side, the flow velocity around the
center tends to increase again on the downstream side and the flow
velocity around the end tends to decrease. In such a case, the
variation in the flow velocity can be suppressed by disposing the
protrusion on both the upstream side and downstream side.
[0091] In the electrolysis device of the present invention,
preferably, the electrolysis unit includes the upper and lower
electrodes, electrode holders that define a channel other than the
interelectrode channel, and the protrusion; at least part of the
protrusion is connected to the upper electrode, the lower
electrode, a base of these electrodes, or a member physically
coupled with these electrodes; and the at least part of the
protrusion is also connected to the electrode holders.
[0092] In this configuration, the upper electrode or the lower
electrode can be fixed to the electrode holder by disposing the
protrusion, and there is no need to separately fix the electrode.
Therefore, the electrolysis device of the present invention can be
provided without complicating the configuration and structure.
[0093] In the electrolysis device of the present invention,
preferably, at least part of the protrusion or a member including
the protrusion is made of a conductive material, and at least part
of the member made of the conductive material is electrically
connected to the upper electrode or the lower electrode.
[0094] In this configuration, the member made of the conductive
material can be used for fixing the upper electrode or the lower
electrode to the electrode holder and applying a voltage to the
upper electrode or the lower electrode. Thus, a lead line for
applying a voltage to the electrode is not additionally required.
Therefore, the complication of the configuration and structure is
prevented. Furthermore, there is no need to attach electrode
terminal lead parts such as pins later unlike known electrolysis
electrode pairs, which reduces the number of parts (pins) and the
number of processes for attaching pins. Alternatively, the
electrode terminal may be led by attaching a lug for terminals to
the electrode in advance. However, when blanking is employed, some
material is wasted. When a lug is attached later, a process for
attaching a lug later needs to be performed. It is also difficult
to use a cheap O-ring for sealing to prevent leakage of an
electrolysis solution from a leading portion, but such a waste or
process is not required in the present invention. Alternatively,
there is a method for leading an electrode terminal to the back
surface of the electrode, and a rod is welded to the back surface
of the electrode in known electrodes. Although welding may also be
employed in the present invention, the electrode can be fixed and
the electrode terminal can be led without employing welding.
Therefore, failure of welding does not occur because there is no
welding process. Even if electrode terminal parts have defects, the
parts can be easily repaired. If welding is employed, the weld is
removed and a new rod is welded again or the electrode itself needs
to be exchanged.
[0095] In the electrolysis device of the present invention, at
least a portion of the surface of the protrusion closest to the
counter electrode is preferably nonconductive.
[0096] In this configuration, proceeding of an electrochemical
reaction on the surface of the protrusion can be suppressed.
[0097] In the electrolysis device of the present invention,
preferably, the member including the protrusion is disposed so as
to be parallel to the direction of the normal to main electrode
surfaces that define the interelectrode channel, and the member
connects the electrode holder and the electrode to each other.
[0098] Thus, the upper electrode or the lower electrode can be
fixed to the electrode holder and a voltage can be applied to the
upper electrode and the lower electrode by a very simple
method.
[0099] In the electrolysis device of the present invention,
preferably, the first electrode holder to which the lower electrode
is fixed and the second electrode holder to which the upper
electrode is fixed have substantially the same shape and are
disposed symmetrically about a point; a spacer is disposed between
the first and second electrode holders; and at least part of the
spacer overlaps the upper electrode and the lower electrode when
viewed in a direction in which the upper electrode and the lower
electrode overlap each other.
[0100] In this configuration, even if the electrode is warped or
loosened for some reason, the probability that both the electrodes
are brought into contact with each other can be decreased. This
improves the safety of the electrolysis device. Furthermore, the
distance between the electrodes can be easily changed by changing
the thickness of the spacer. Therefore, the specifications can be
easily changed in accordance with the purposes of products, and
thus commonality of parts such as an electrode holder is easily
achieved.
[0101] In the electrolysis device of the present invention, the
spacer preferably overlaps edges of the upper electrode and the
lower electrode when viewed in a direction in which the upper
electrode and the lower electrode overlap each other.
[0102] In this configuration, the electrolysis at electrode edges
where an electric field is easily concentrated and degradation is
easily caused can be suppressed. This stabilizes the electrolysis,
suppresses the electrode wear, and increases the life.
[0103] In the electrolysis device of the present invention, the
electrolysis unit is preferably disposed so that an aqueous
solution of a compound containing a chlorine atom is electrolyzed
to produce at least one of a hypochlorite ion and a chlorine
molecule having a concentration corresponding to 4000 ppm or more,
and the at least one of a hypochlorite ion and a chlorine molecule
is diluted to produce a hypochlorous acid water having a pH of 7 or
less.
[0104] In this case, the production efficiency of the hypochlorous
acid water can be improved by employing the above means.
[0105] Hereafter, embodiments of the present invention will be
described with reference to the attached drawings. The
configurations in the drawings and the following description are
merely examples, and the scope of the present invention is not
limited by the drawings and the following description.
First Embodiment
[0106] FIGS. 1(a) and 1(b) are schematic sectional views of an
electrolysis device according to the first embodiment. FIG. 1(c) is
a diagram for describing an overlap of an upper electrode and a
lower electrode when the electrolysis device in FIG. 1(a) is viewed
in a vertical direction A. FIG. 1(d) is a diagram for describing an
overlap of an upper electrode and a lower electrode when the
electrolysis device in FIG. 1(a) is viewed in a direction B
perpendicular to a principal surface of the lower electrode.
[0107] An electrolysis device 15 according to the first embodiment
includes an electrolysis unit 10. The electrolysis unit 10 includes
a channel 7 for fluid to be treated, at least one electrolysis
electrode pair 5, a flow inlet 8, and a flow outlet 9. The
electrolysis electrode pair 5 is disposed so as to incline with
respect to the vertical direction, includes an upper electrode 3
and a lower electrode 4 disposed so as to face each other, and is
disposed so that an electrode reaction that generates a gas
proceeds at the lower electrode 4. The channel 7 for fluid to be
treated is disposed so that a fluid that has flowed in from the
flow inlet 8 flows through an interelectrode channel 6 between the
upper electrode 3 and the lower electrode 4 from the lower side to
the upper side and flows out from the flow outlet 9.
[0108] In the electrolysis device 15 (electrolysis unit 10)
according to the first embodiment, the plate-shaped upper electrode
3 and the plate-shaped lower electrode 4 are fixed to a casing 1 so
as to face each other, and the interelectrode channel 6 is formed
between the upper electrode 3 and the lower electrode 4. When the
electrolysis electrode pair 5 is disposed so as to incline with
respect to the vertical direction, the upper electrode 3 is an
electrode located on the upper side and the lower electrode 4 is an
electrode located on the lower side.
[0109] The electrolysis unit 10 is a unit including the channel 7
for fluid to be treated and is a constituent unit of the
electrolysis device 15. The electrolysis device 15 is constituted
by a single electrolysis unit 10 in FIG. 1, but the electrolysis
device 15 may be constituted by a plurality of electrolysis units
10. The plurality of electrolysis units 10 may be combined with
each other so that the channels 7 for fluid to be treated are
arranged in parallel or in series.
[0110] The casing 1 is provided so that the channel 7 for fluid to
be treated can be formed by the casing 1, the upper electrode 3,
and the lower electrode 4. The casing 1 is made of a material
having resistance to a fluid that flows through the channel 7 for
fluid to be treated and a gas generated by electrolysis as a
by-product. Specific examples of the material for the casing 1
include fluorocarbon resins, vinyl chloride resins, polypropylene
resins, and acrylic resins in consideration of durability.
[0111] The casing 1 may have a tubular structure or may have a
structure in which the channel 7 for fluid to be treated is formed
by combining a plurality of members. When the casing 1 has a
tubular structure, the upper electrode 3 and the lower electrode 4
can be fixed onto the inner wall surface of the tubular structure.
When the casing 1 has a structure including a plurality of members
combined with each other, the channel 7 for fluid to be treated may
be formed by combining a first member to which the upper electrode
3 is fixed and a second member to which the lower electrode 4 is
fixed. In this case, a third member may be sandwiched between the
first member and the second member. The member for the casing 1 or
the casing 1 may be an electrode holder to which the upper
electrode 3 or the lower electrode 4 is fixed.
[0112] The channel 7 for fluid to be treated is disposed so that a
fluid that has flowed in from the flow inlet 8 flows through the
interelectrode channel 6 between the upper electrode 3 and the
lower electrode 4 from the lower side to the upper side and flows
out from the flow outlet 9. The flow inlet 8 can be connected to a
raw electrolysis solution tank via a pump. Thus, the raw
electrolysis solution in the tank can be caused to flow through the
channel 7 for fluid to be treated and electrolysis can be
performed. The flow outlet 9 can be connected to, for example, a
tank for storing a fluid subjected to electrolysis, a
liquid-feeding pipe through which a fluid subjected to electrolysis
is fed to a place where the fluid is used, or a dilution unit.
[0113] As a result of the flow of a fluid from the lower side to
the upper side of the interelectrode channel 6, gas generated at
the upper electrode 3 or the lower electrode 4 can be efficiently
discharged from the interelectrode channel 6, which suppresses a
decrease in electrolysis efficiency due to holding of the gas.
Furthermore, the flow inlet 8 can be disposed below a lower edge of
the interelectrode channel 6 and the flow outlet 9 can be disposed
above an upper edge of the interelectrode channel 6. Thus, gas
generated at the upper electrode 3 or the lower electrode 4 can be
efficiently discharged from the interelectrode channel 6, which
suppresses a decrease in electrolysis efficiency due to holding of
the gas.
[0114] The channel 7 for fluid to be treated is constituted by a
part of the casing 1 and the interelectrode channel 6. The inner
wall surface of the channel 7 for fluid to be treated is desirably
constituted by an electrolysis electrode pair 5 having as large a
surface as possible and a casing 1 having as small a surface as
possible. In this configuration, the electrode surface area which
is included in the inner wall surface of the channel 7 for fluid to
be treated and in which an electrolysis reaction proceeds can be
increased, and a surface area that does not contribute to
electrolysis can be decreased as much as possible. By increasing
the electrode surface area, an electrolysis reaction can be
sufficiently caused to proceed at a low current density. Therefore,
the life of the electrolysis electrode pair 5 can be extended and
the electrolysis efficiency can also be improved. By decreasing the
surface area that does not contribute to electrolysis, the internal
volume of the electrolysis unit 10 can be decreased while the same
electrolysis performance is maintained. Therefore, the startup
characteristics of the electrolysis device 15 can be improved. When
electrolyzed water is produced using the electrolysis device 15,
the rise of the concentration of the electrolyzed water can be
improved.
[0115] The electrolysis electrode pair 5 includes the upper
electrode 3 and the lower electrode 4. The electrolysis unit 10 in
FIG. 1 includes one electrolysis electrode pair 5, but may include
a plurality of electrolysis electrode pairs 5.
[0116] The upper electrode 3 and the lower electrode 4 are disposed
so that the principal surface (electrode surface) of the upper
electrode 3 and the principal surface (electrode surface) of the
lower electrode 4 face each other. The upper electrode 3 and the
lower electrode 4 are also disposed so that the interelectrode
channel 6 is formed between the principal surface of the upper
electrode 3 and the principal surface of the lower electrode 4.
Furthermore, the upper electrode 3 and the lower electrode 4 can be
disposed so that the principal surface of the upper electrode 3 and
the principal surface of the lower electrode 4 are substantially
parallel to each other. The interelectrode channel 6 is a part of
the channel 7 for fluid to be treated. In this configuration, a
fluid flowing through the interelectrode channel 6 can be
electrolyzed by applying a voltage between the upper electrode 3
and the lower electrode 4, and thus a fluid containing an
electrolysis product can be produced.
[0117] The upper electrode 3 may be curved so as to have a
projected shape facing the lower electrode 4 and the lower
electrode 4 may be curved so as to have a depressed shape facing
the upper electrode 3. The radius of curvature of the upper
electrode 3 may be smaller than that of the lower electrode 4.
[0118] The upper electrode 3 and the lower electrode 4 are each
connected to a wiring line for applying a potential difference
between the electrodes, and the wiring lines are connected to a
power supply. The wiring line may be a conductive member used for
fixing the upper electrode 3 or the lower electrode 4 to the casing
1.
[0119] The upper electrode 3 and the lower electrode 4 may be
disposed so that the upper electrode 3 serves as an anode and the
lower electrode 4 serves as a cathode or so that the upper
electrode 3 serves as a cathode and the lower electrode 4 serves as
an anode.
[0120] The upper electrode 3 and the lower electrode 4 are disposed
so that an electrode reaction that generates gas proceeds at the
lower electrode 4. This efficiently produces an electrolysis
product. If an electrode reaction that generates gas proceeds at
both the upper electrode 3 and the lower electrode 4, the upper
electrode 3 and the lower electrode 4 can be disposed so that the
amount of air bubbles generated is larger at the lower electrode 4
than at the upper electrode 3.
[0121] The upper electrode 3 and the lower electrode 4 can be fixed
to the casing 1. The upper electrode 3 or the lower electrode 4 may
be fixed to the casing 1 with a screw member or may be fixed to the
casing 1 with an adhesive. The upper electrode 3 or the lower
electrode 4 may be fixed to a flat surface or a curved surface of
the casing 1 or may be fixed to a groove of the casing 1. In the
electrolysis device 10 in FIG. 1, the upper electrode 3 and the
lower electrode 4 are disposed in grooves of the casing 1 to
prevent formation of steps in the channel 7 for fluid to be
treated.
[0122] The upper electrode 3 and the lower electrode 4 may have a
flat plate shape or a curved plate shape. The upper electrode 3 and
the lower electrode 4 may have a rectangular shape or a circular
shape. The upper electrode 3 and the lower electrode 4 may have
substantially the same shape or different shapes. The upper
electrode 3 and the lower electrode 4 included in the electrolysis
unit 10 in FIG. 1 have substantially the same rectangular plate
shape. The upper electrode 3 and the lower electrode 4 each have,
for example, 8-cm long sides and 3-cm short sides.
[0123] The upper electrode 3 and the lower electrode 4 may have a
mesh-like structure, a perforated structure, or a porous
structure.
[0124] When at least part of the upper electrode 3 has a mesh-like
structure or a perforated structure, a space may be provided on the
side (back side) of the upper electrode 3 opposite to the lower
electrode 4. Furthermore, a supporting electrode electrically
connected to the upper electrode 3 may be disposed on a wall
surface that defines the space. Thus, air bubbles on the electrode
surface of the upper electrode 3 can be discharged to the back
side, and therefore a decrease in the effective electrode area can
be suppressed. Moreover, an electrode reaction can be caused to
proceed on the supporting electrode, which increases the effective
electrode area.
[0125] The upper electrode 3 and the lower electrode 4 is formed of
a conductive material such as a metal material. The upper electrode
3 and the lower electrode 4 may be insoluble electrodes. The upper
electrode 3 and the lower electrode 4 may each have a surface on
which a catalyst such as Pt, Pd, Ir, or Ru is supported or coated.
Thus, an electrolysis reaction can be efficiently caused to
proceed.
[0126] For example, one of the upper electrode 3 and the lower
electrode 4 serving as a cathode may be an electrode containing Ti,
Pt, or another metal, and the other of the upper electrode 3 and
the lower electrode 4 serving as an anode may be an electrode
containing Ir or Ru or an insoluble electrode containing Pt or the
like.
[0127] The upper electrode 3 and the lower electrode 4 (the
electrolysis electrode pair 5) are disposed so as to incline with
respect to the vertical direction. The upper electrode 3 and the
lower electrode 4 are disposed so that at least part of the upper
electrode 3 is located above the lower electrode 4 in the vertical
direction.
[0128] The upper electrode 3 and the lower electrode 4 can be
disposed so as to have an inclination angle of more than 0.degree.
and less than 50.degree. with respect to the vertical direction.
The inclination angle may be 5.degree. or more and 45.degree. or
less and may also be 15.degree. or more and 32.degree. or less. The
inclination angle is an inclination angle of a surface (principal
surface or electrode surface) of the upper electrode 3 that faces
the lower electrode 4 or an inclination angle of a surface
(principal surface or electrode surface) of the lower electrode 4
that faces the upper electrode 3. The inclination angle of the
upper electrode 3 and the inclination angle of the lower electrode
4 are preferably substantially the same. Thus, the distance between
the electrodes can be substantially made constant, which suppresses
the concentration of electric current.
[0129] By disposing the electrolysis electrode pair 5 in such a
manner, the electrolysis efficiency can be improved.
[0130] In the electrolysis unit 10 in FIG. 1, the upper electrode 3
and the lower electrode 4 are disposed so as to have an inclination
angle .theta.. As illustrated in FIG. 1(d), when viewed in a
direction B perpendicular to the principal surface of the lower
electrode 4, the upper electrode 3 and the lower electrode 4 having
substantially the same size are disposed so that substantially the
entire surfaces of the upper electrode 3 and the lower electrode 4
overlap each other. As illustrated in FIG. 1(c), when viewed in the
vertical direction A, the upper electrode 3 and the lower electrode
4 are disposed so as to overlap each other in an overlap region 16.
The electrolysis unit 10 is disposed so that a fluid to be treated
flows from the lower side to the upper side of the interelectrode
channel 6 and an electrode reaction that generates gas (air bubbles
11) proceeds at the lower electrode 4.
[0131] In this electrolysis unit 10, as illustrated in FIG. 1(b),
air bubbles 11 are generated on the lower electrode 4 through the
electrode reaction at the lower electrode 4. The air bubbles 11 can
be caused to float toward the upper electrode 3 so as to cross a
fluid flowing in the flow direction. As a result of a flow of the
fluid caused by the floating of the air bubbles 11, a fluid around
the lower electrode 4 and a fluid around the upper electrode 3 can
be stirred and mixed, which facilitates the electrode reaction at
the upper electrode 3. Furthermore, the movement of a fluid located
upstream of the lower electrode 4 in the direction toward the upper
electrode 3 is facilitated with the movement of the air bubbles 11.
Therefore, a fluid located downstream of the lower electrode 4
contains a small fraction of a liquid component subjected to
electrolysis. Thus, the production efficiency of an electrolysis
product can be improved.
[0132] The electrolysis product produced by the electrolysis
electrode pair 5 is, for example, hypochlorous acid. In this case,
when an aqueous solution of an alkali metal chloride is supplied to
the channel 7 for fluid to be treated (interelectrode channel 6)
from the flow inlet 8 and a voltage is applied between the upper
electrode 3 and the lower electrode 4, an electrolysis reaction
represented by the above reaction formulae (1) to (4) can be caused
to proceed, and thus an aqueous hypochlorite solution (electrolyzed
water) can be produced.
[0133] Also in this case, a voltage can be applied so that the
upper electrode 3 serves as an anode and the lower electrode 4
serves as a cathode. Consequently, air bubbles of H.sub.2 gas can
be generated on the lower electrode 4, the aqueous solution can be
stirred and mixed by the floating of the air bubbles, and the
production efficiency of hypochlorous acid can be improved.
Furthermore, an aqueous solution near the anode can be prevented
from becoming a strongly acidic solution. This increases the rate
of reaction in the above reaction formula (2). Thus, the production
efficiency of hypochlorous acid can be improved.
Second Embodiment
[0134] FIGS. 2(a) and 2(b) are schematic sectional views of an
electrolysis device according to the second embodiment. FIG. 2(c)
is a diagram for describing an overlap of an upper electrode and a
lower electrode when the electrolysis device in FIG. 2(a) is viewed
in a vertical direction A. FIG. 2(d) is a diagram for describing an
overlap of an upper electrode and a lower electrode when the
electrolysis device in FIG. 2(a) is viewed in a direction B
perpendicular to a principal surface of the lower electrode.
[0135] In the electrolysis device in FIG. 1, the upper electrode 3
and the lower electrode 4 are disposed so that substantially the
entire surfaces of the upper electrode 3 and the lower electrode 4
overlap each other when viewed in the direction B. However, in the
electrolysis device 15 according to the second embodiment, the
upper electrode 3 is disposed so as to shift upward. Specifically,
as illustrated in FIG. 2(d), when viewed in the direction B
perpendicular to the principal surface of the lower electrode 4,
the upper electrode 3 and the lower electrode 4 overlap each other
in an overlap region 17. However, an upper region included in the
upper electrode 3 does not overlap the lower electrode 4, and a
lower region included in the lower electrode 4 does not overlap the
upper electrode 3.
[0136] In the electrolysis device 15 according to the second
embodiment, when the cross section of the electrolysis unit 10 in a
direction in which the cross-sectional area of the interelectrode
channel 6 is the smallest includes a plane C that includes the
upper electrode 3, but does not include the lower electrode 4, a
plane D that includes both the upper electrode 3 and the lower
electrode 4, and a plane E that includes the lower electrode, but
does not include the upper electrode 3, the upper electrode 3 and
the lower electrode 4 are disposed so that the plane C is located
at the top, the plane E is located at the bottom, and the plane D
is located between the plane C and the plane E.
[0137] In this configuration, as illustrated in FIG. 2(c), the
overlap region 16 where the upper electrode 3 and the lower
electrode 4 overlap each other when viewed in the vertical
direction A can be widened.
[0138] In this electrolysis unit 10, as illustrated in FIG. 2(b),
air bubbles 11 are generated through the electrode reaction at the
lower electrode 4, and the air bubbles 11 can be caused to float
toward the upper electrode 3 so as to cross a fluid flowing in the
flow direction. Furthermore, since the overlap region 16 is large
as illustrated in FIG. 2(c), the probability that the air bubbles
11 generated at the lower electrode 4 float and come close to the
upper electrode 3 can be increased. Furthermore, even if the air
bubbles 11 generated at the lower electrode 4 are carried away
downstream by the flow in the channel 7 for fluid to be treated,
the air bubbles 11 can be brought close to the upper electrode 3
with a high probability. Therefore, a stirring and mixing effect
produced by the air bubbles 11 can be increased, and the electrode
reaction at the upper electrode 3 can be more effectively
facilitated. Thus, the production efficiency of an electrolysis
product can be improved.
[0139] For example, in the case where an aqueous solution of a
substance containing a chlorine atom is electrolyzed to produce
hypochlorous acid with the electrolysis device 15 according to the
second embodiment using the lower electrode 4 as an anode and the
upper electrode 3 as a cathode, even if chlorine gas generated at
the lower electrode 4 floats on the downstream side with respect to
the vertically upward direction by the velocity of flow of a
liquid, the chlorine gas can be brought close to the upper
electrode 3 serving as a cathode. This increases the fraction of
chlorine gas converted into hypochlorous acid.
Third Embodiment
[0140] FIG. 3(a) is a schematic sectional view of an electrolysis
device according to the third embodiment. FIG. 3(b) is a diagram
for describing an overlap of an upper electrode and a lower
electrode when the electrolysis device in FIG. 3(a) is viewed in a
vertical direction A. FIG. 3(c) is a diagram for describing an
overlap of an upper electrode and a lower electrode when the
electrolysis device in FIG. 3(a) is viewed in a direction B
perpendicular to an electrode surface of the lower electrode.
[0141] In the electrolysis devices 15 illustrated in FIGS. 1 and 2,
the electrode surface of the upper electrode 3 and the electrode
surface of the lower electrode 4 have substantially the same size.
However, in the electrolysis device 15 according to the third
embodiment, the electrode surface of the lower electrode 4 is
larger than that of the upper electrode 3. Furthermore, as
illustrated in FIG. 3(c), ower electrode 4 can be disposed so that
when the electrolysis device 15 is viewed in the direction B
perpendicular to the electrode surface of the lower electrode 4,
D>U.gtoreq.S is satisfied, where D represents a protruding
length on the downstream side, U represents a protruding length on
the upstream side, and S represents a protruding length at the
side. As illustrated in FIG. 3(b), when the electrolysis device 15
is viewed in the vertical direction A, the upper electrode 3 and
the lower electrode 4 can be disposed so that the entire surface of
the upper electrode 3 overlaps the lower electrode 4.
[0142] For example, in the case where an aqueous solution of a
substance containing a chlorine atom is electrolyzed to produce
hypochlorous acid using the lower electrode 4 as a cathode and the
upper electrode 3 as an anode, if the electrode surface of the
upper electrode 3 and the electrode surface of the lower electrode
4 have substantially the same area, the air bubbles of chlorine gas
are dissolved and reduced around the upper electrode 3 because of a
stirring and mixing effect produced by air bubbles and thus a
decrease in the effective electrode area due to air bubbles is
suppressed. However, such an effect is not produced at the lower
electrode 4, and the effective electrode area is sometimes
decreased by air bubbles of hydrogen gas. This relatively decreases
the effective electrode area of the lower electrode 4, which is a
rate-determining factor of the electrolysis reaction. Consequently,
the area of the upper electrode 3 is sometimes not effectively
utilized.
[0143] By increasing the electrode surface area of the lower
electrode 4 more than the upper electrode 3, the above phenomenon
can be relaxed. Consequently, the electrode surface area can be
effectively utilized, and the electrolysis efficiency per unit area
of the upper electrode 3 can be improved.
[0144] In the above configuration, when air bubbles of hydrogen gas
generated on the upstream side of the lower electrode 4 come close
to the upper electrode 3 serving as an anode and located above the
lower electrode 4 in the vertical direction, the air bubbles can be
brought into contact with an aqueous solution which has been
electrolyzed on the upstream side of the upper electrode 3 and thus
whose pH has been decreased. Therefore, chlorine gas can be
efficiently converted into hypochlorous acid.
[0145] In the above configuration, even if hydrogen gas generated
at the lower electrode 4 floats on the downstream side with respect
to the vertically upward direction by the velocity of flow of a
liquid, the hydrogen gas comes close to the upper electrode 3. This
increases the fraction of chlorine gas converted into hypochlorous
acid. In particular, even if an electric field on the downstream
side of the upper electrode 3 is shielded by a large amount of air
bubbles of hydrogen gas generated, the fraction of chlorine gas
converted into hypochlorous acid can be expected to be increased to
some degree by a fringing field to the electrode that extends to
the downstream side or oxidation of air bubbles that have directly
contacted the electrode.
Fourth Embodiment
[0146] FIG. 4 is a schematic sectional view of an electrolysis
device according to the fourth embodiment.
[0147] The electrolysis devices 15 in FIGS. 1 to 3 include a linear
channel 7 for fluid to be treated. However, in the electrolysis
device 15 according to the fourth embodiment, the channel 7 for
fluid to be treated includes an upstream-side bent channel 25
located close to the end of the interelectrode channel 6 on the
upstream side or a downstream-side bent channel 26 located close to
the end of the interelectrode channel 6 on the downstream side. The
electrolysis device 15 may include both the upstream-side bent
channel 25 and the downstream-side bent channel 26 or either the
upstream-side bent channel 25 or the downstream-side bent channel
26.
[0148] For example, at least one of the flow inlet 8 and the flow
outlet 9 can be disposed so that the direction of a channel near
the flow inlet 8 or the flow outlet 9 is not parallel to the
direction of the interelectrode channel 6. Thus, the upstream-side
bent channel 25 or the downstream-side bent channel 26 can be
disposed. In this configuration, a turbulent flow can be caused on
a liquid in the channel 7 for fluid to be treated.
[0149] When the upstream-side bent channel 25 is disposed near the
electrolysis electrode 5, the influence of a turbulent flow
generated in the bent channel can be exerted on the interelectrode
channel 6. This sufficiently produces a stirring effect from near
the inlet where air bubbles are not so generated. Therefore, the
diffusion of a substance near the electrode surface can be
facilitated, and the electrolysis efficiency can be improved.
[0150] In the case where the downstream-side bent channel 26 is
disposed, even if there is a gas not sufficiently dissolved at the
interelectrode channel 6, stirring can be performed again at the
bent channel. For example, when an aqueous solution of a substance
containing a chlorine atom is electrolyzed to produce hypochlorous
acid, chlorine gas is not sufficiently dissolved under some
conditions, which sometimes decreases the production efficiency of
hypochlorous acid. In this configuration, however, dissolution of
chlorine gas and conversion into hypochlorous acid can be
facilitated, and the electrolysis efficiency can be substantially
improved.
[0151] The downstream-side bent channel 26 is preferably disposed
so that air bubbles generated at the electrolysis electrode pair 5
are capable of floating to the flow outlet 9 by their buoyancy.
Consequently, the air bubbles can be quickly discharged from the
channel 7 for fluid to be treated. Thus, a decrease in the
electrolysis efficiency due to holding of air bubbles can be
suppressed.
Fifth Embodiment
[0152] FIG. 6(a) is a schematic sectional view of an electrolysis
device according to the fifth embodiment. FIGS. 6(b) to 6(d) are
schematic sectional views of constituent parts of the electrolysis
device according to the fifth embodiment.
[0153] The electrolysis device 15 according to the fifth embodiment
includes an assembly-type electrolysis unit 10. In the fifth
embodiment, the electrolysis unit 10 is constituted by three parts.
Two of the three parts are a first electrode holder 31 in FIG. 6(b)
to which the lower electrode 4 is fixed and a second electrode
holder 32 in FIG. 6(d) to which the upper electrode 3 is fixed. The
remaining one is disposed as a spacer 33 between the first and
second electrode holders 31 and 32. When viewed in a direction in
which the electrolysis electrode pair 5 overlaps each other, at
least part of the spacer 33 overlaps the electrolysis electrode
pair 5. Furthermore, a protrusion 35 is disposed on each of the
upstream side and the downstream side of the interelectrode channel
6. The upstream-side bent channel 25 and the downstream-side bent
channel 26 are also disposed.
[0154] The spacer 33 is disposed so that the interelectrode channel
6 is formed between the upper electrode 3 and the lower electrode
4. The first electrode holder 31 at least has a recess to which the
upper electrode 3 is to be fixed, and the second electrode holder
32 at least has a recess to which the lower electrode 4 is to be
fixed. The distance (the depth of the recess) between the surface
to which the upper electrode 3 or the lower electrode 4 is fixed
and the surface in contact with the spacer 33 is preferably larger
than the thickness of the electrode to be fixed. This produces a
stirring effect on air bubbles and a liquid. Even if the electrode
is warped or loosened for some reason, the probability that the
upper electrode 3 and the lower electrode 4 are brought into
contact with each other can be decreased. This improves the
electrolysis efficiency and safety of the electrolysis device 15.
Furthermore, the distance between the upper electrode 3 and the
lower electrode 4 can be easily changed by changing the thickness
of the spacer 33. Therefore, the specifications can be easily
changed in accordance with the purposes of products, and thus
commonality of parts such as an electrode holder is easily
achieved. The metal holders 31 and 32 are made of a resin such as
acrylic resin or vinyl chloride resin.
[0155] In the electrolysis device 15 in FIG. 6(a), a bolt 41 for
fixing the upper electrode 3 and a bolt 41 for fixing the lower
electrode 4 are electrode terminals 45. The bolt 41 is made of a
metal material such as metal titanium.
[0156] FIGS. 7(a) and 7(b) are schematic sectional views for
describing the flow of a fluid in the electrolysis device 15 in
FIG. 6(a). FIG. 7(b) is a schematic sectional view of the
electrolysis device 15 taken along dot-and-dash line F-F of FIG.
7(a).
[0157] It is generally found that, regarding the flow velocity in a
channel, an average velocity V1 in a central portion is high and an
average velocity V2 in a portion near the end is low. The amount of
chemical change per unit volume by electrolysis, that is, the
concentration k of a desired component produced by electrolysis is
substantially proportional to the time t for which the electrolysis
is performed as long as other conditions are the same. In other
words, k.varies.t is given. When the electrode has a substantially
rectangular shape and the central portion and the end portion have
substantially the same length L in a direction of the average flow
velocity, t=L/V and thus k.varies.L/V. Therefore, the concentration
of a desired component generated in an aqueous solution flowing in
the central portion is k1.varies.L/V1, and the concentration in the
end portion is k2.varies.L/V2. When k1-k2 is used as an index of
concentration variation, k1-k2=L(1/V1-1/V2) is given.
[0158] When the protrusion 35 is disposed upstream of the
interelectrode channel 6 as illustrated in FIGS. 7(a) and 7(b), the
protrusion 35 guides an obstacle and a fluid from the central
portion to the end portion in the movement of liquid in the
channel. Consequently, the amount of a fluid flowing per unit
sectional area is small in the central portion and large in the end
portion. Therefore, in a simplified system, the flow velocity in
the central portion is V1-v on average and the flow velocity in the
end portion is V2-v on average (v>0). The concentration
variation herein is represented by k1-k2=L(1/(V1-v)-1/(V2-v)), and
the concentration variation is small as long as V1-V2>v is
satisfied.
Sixth Embodiment
[0159] FIG. 8 is a schematic sectional view of an electrolysis
device according to the sixth embodiment. The electrolysis unit 10
included in the electrolysis device 15 in FIG. 8 includes at least
the electrolysis electrode pair 5 and electrode holders 30 that
define a channel other than the interelectrode channel 6. At least
part of a member (an electrode terminal 45 in FIG. 8) including the
protrusion 35 is connected to the electrolysis electrode pair 5, a
base of the electrolysis electrode pair 5, or a member physically
coupled with the electrolysis electrode pair 5. The at least part
of the member is also connected to the electrode holders 30. By
employing this connecting structure, the electrolysis electrode
pair 5 can be fixed to the electrode holders 30. Therefore, the
complication of the configuration and structure is prevented. The
above connecting structure also reinforces the fixing of the
electrolysis electrode pair 5 to the electrode holders 30. Thus,
the reliability of the electrolysis unit 10 can be improved.
[0160] At least part of the protrusion 35 or the member coupled
with the protrusion 35 (electrode terminal 45 in FIG. 8) is made of
a conductive material, and at least part of the member may be
electrically connected to the electrolysis electrode pair 5.
[0161] The member including the protrusion 35 may be disposed in
the direction of the normal to a principal surface of the
electrolysis electrode pair 5 that defines the channel 7 for fluid
to be treated to connect the electrode holder and the electrode to
each other.
[0162] For example, the protrusion 35 and the electrode terminal 45
may form a single member. The electrode holder 30 and the
electrolysis electrode pair 5 have a hole with a size suitable for
the electrode terminal 45 at a predetermined position. A groove is
cut in at least a suitable portion of the electrode terminal 45 on
the side opposite to the protrusion 35. The electrolysis electrode
pair 5 can be fixed to the electrode holder 30 using a nut 42
suitable for the groove. At the same time, a voltage can be applied
to the electrolysis electrode pair 5 from the outside of the
electrode holder 30 through the electrode terminal 45. If
necessary, an O-ring 47, a washer 48, and a spring washer 49 may be
used to suppress liquid leakage.
[0163] Alternatively, for example, a female thread is cut in the
hole of the electrode holder 30 and a male thread is cut on the
electrode terminal 45, and the metal holder 30 and the electrode
terminal 45 may be joined to each other by combining the female
thread and the male thread. In this structure, the electrolysis
electrode pair 5 can be fixed to the electrode holder 30 without
using a nut.
[0164] Alternatively, for example, the electrode holder 30 and the
electrode terminal 45 may be molded in one piece.
[0165] Since the electrolysis electrode pair 5 can be fixed to the
electrode holder 30 and a voltage can be applied to the
electrolysis electrode pair 5 by employing such a structure, a lead
line for applying a voltage to the electrolysis electrode pair 5 is
not additionally required. Therefore, the complication of the
configuration and structure is prevented. Furthermore, the
electrolysis electrode pair 5 can be fixed to the electrode holder
30 and a voltage can be applied to the electrolysis electrode pair
5 by a very simple method.
[0166] At least a portion of the surface of the protrusion 35
closest to the counter electrode may be nonconductive. For example,
a nonconductive film can be formed by oxidizing the surface of the
protrusion 35. Alternatively, the surface of the protrusion 35 may
be coated with a resin or the like. This suppresses the progress of
an electrochemical reaction on the surface of the protrusion 35,
and also suppresses generation of undesired components and
considerable variation in the concentration of a component
generated.
Seventh Embodiment
[0167] FIG. 9(a) is a schematic sectional view of an electrolysis
device according to the seventh embodiment. FIGS. 9(b) to 9(f) are
schematic sectional views of constituent parts of the electrolysis
device according to the seventh embodiment. FIG. 9(d) is a
schematic sectional view of a spacer 33 taken along dot-and-dash
line G-G of FIG. 9(c). FIG. 9(e) is a schematic sectional view of a
spacer 33 taken along dot-and-dash line H-H of FIG. 9(c).
[0168] The electrolysis device 15 according to the seventh
embodiment includes an assembly-type electrolysis unit 10. In the
seventh embodiment, the electrolysis unit 10 is constituted by
three parts. Two of the three parts are a first electrode holder 31
in FIG. 9(b) to which the lower electrode 4 is fixed and a second
electrode holder 32 in FIG. 9(f) to which the upper electrode 3 is
fixed. The remaining one is a spacer 33 in FIGS. 9(c) to 9(e) and
is disposed between the first and second electrode holders 31 and
32. In the electrolysis device 15 in FIG. 9, an opening 36 of the
spacer between the electrodes is formed with a size smaller than
that of the electrolysis device 15 in FIG. 6. The spacer 33 is
disposed so that the spacer 33 and the edges of the upper electrode
3 and lower electrode 4 overlap each other when view in a direction
perpendicular to the electrode surface of the lower electrode 4.
This suppresses the progress of an electrolysis reaction at an
electrode edge where electric field concentration easily occurs and
degradation also easily occurs. Thus, stable electrolysis can be
performed, and electrode wear is suppressed, which increases the
life of the electrolysis electrode pair 5.
Eighth Embodiment
[0169] FIGS. 10(a) and 10(b) are schematic views of electrolysis
devices according to the eighth embodiment.
[0170] The electrolysis device 15 according to the eighth
embodiment includes the electrolysis unit 10 according to one of
the first to seventh embodiments, a raw solution tank 51, and a
dilution unit 53. A pipe 57 is indicated by an arrow that also
indicates a direction in which a fluid flows through the pipe. In
the electrolysis device 15 in FIG. 10(a), a diluted solution is
produced by injecting a solution subjected to electrolysis in the
electrolysis unit 10 into stored water 55 in a dilution tank 54
serving as the dilution unit 53. In the electrolysis device 15 in
FIG. 10(b), a diluted solution is produced by mixing a solution
subjected to electrolysis in the electrolysis unit 10 with flowing
water in a mixing unit 59 serving as the dilution unit 53. In FIGS.
10(a) and 10(b), wiring lines for supplying power to the
electrolysis electrode pair 5 in the electrolysis unit 10, an
optionally provided feeding pump, and the like are not
illustrated.
[0171] In this configuration, a diluted solution containing an
electrolysis product can be produced. When an aqueous solution of a
substance containing a chlorine atom is electrolyzed to produce
hypochlorous acid, a diluted solution can be produced while the
release of chlorine gas is suppressed.
Ninth Embodiment
[0172] FIG. 11 is a schematic view of an electrolysis device
according to the ninth embodiment. The electrolysis device 15
according to the ninth embodiment has the same configuration as the
known electrolyzed water-producing device 120 illustrated in FIGS.
16 and 17, except that the electrolysis unit 10 disposed so that
the electrolysis electrode pair 5 inclines with respect to the
vertical direction is used. The fundamental operation of the
electrolysis device 15 according to the ninth embodiment is also
the same as that of the known electrolyzed water-producing device
120.
[0173] In the electrolysis device 15, desirably, a
solenoid-controlled valve 66, the electrolysis unit 10, and a pump
68 are not operated upon turning a switch 64 ON, but the
solenoid-controlled valve 66 is opened at an appropriate timing and
water is supplied to the electrolysis device 15 from a feed water
inlet 62, flows through a pipe 65, and is discharged from a
discharge outlet 63. At an appropriate timing, the feeding pump 68
is operated and a raw electrolysis solution stored in a raw
solution tank 67 is supplied to the electrolysis unit 10. Power is
supplied to the electrolysis unit 10 from a power supply (not
illustrated) at an appropriate timing, and the raw solution is
electrolyzed. The high-concentration electrolyzed water produced by
electrolysis is supplied to the pipe 65 and diluted to an
appropriate concentration with water flowing through the pipe 65.
The diluted electrolyzed water is fed to an electrolyzed water
supply point through a pipe such as a hose suitably connected to
the discharge outlet 63.
[0174] When the switch 64 is turned OFF, power supply to the
solenoid-controlled valve 66, the feeding pump 68, and the
electrolysis unit 10 is shut off at an appropriate timing, and the
operation of the electrolysis device 15 is stopped.
[0175] In reality, an optimum sequence is set in accordance with
the purpose. For example, with an interlock being provided, a
solenoid-controlled valve is opened, a raw solution left in the
electrolysis unit 10 during the previous operation is electrolyzed
to a slight degree, and then a raw solution is started to be
supplied.
[0176] For example, when the probability of initially producing
high-concentration electrolyzed water needs to be decreased as much
as possible, the solenoid-controlled valve 66, the feeding pump 68,
and the electrolysis unit 10 are preferably turned ON in this
order.
[0177] When the concentration of the electrolyzed water needs to be
quickly increased, for example, the electrolysis unit 10, the
feeding pump 68, and the solenoid-controlled valve 66 may be turned
ON in this order.
[0178] In the case of stopping the operation, when rinsing with
water needs to be performed after the electrolyzed water is used,
the electrolysis unit 10 and the feeding pump 68 are turned OFF and
then the ON-state of the solenoid-controlled valve 66 is kept for a
predetermined time. Thus, rinsing can be performed for the
predetermined time.
[0179] When the high-concentration electrolyzed water is prevented
from remaining in the electrolysis unit 10, the electrolysis unit
10 is turned OFF and then the ON-state of the feeding pump 68 is
kept for a while. Thus, the high-concentration electrolyzed water
in the electrolysis unit 10 can be diluted with the raw
electrolysis solution or almost all the high-concentration
electrolyzed water can be replaced with the raw electrolysis
solution. In this case, the solenoid-controlled valve 66 is also
desirably turned ON. Obviously, additional amounts of raw solution
and water are required in this case. Therefore, if such a repeated
use is frequently performed, the electrolysis device is desirably
designed so that such an operation is unnecessary.
Experimental Example 1
[0180] The electrolysis device illustrated in FIG. 1 was produced
and an electrolysis experiment was performed with various
inclination angles with respect to the vertical direction of the
electrolysis electrode pair 5. The electrolysis electrode pair 5
included an electrode (referred to as a Ti electrode) formed of a
titanium plate and having 8-cm long sides, 3-cm short sides, and a
thickness of 1 mm and an electrode (referred to as an Ir-coated Ti
electrode) obtained by coating a titanium plate having 8-cm long
sides, 3-cm short sides, and a thickness of 1 mm with iridium oxide
by a sintering method. The electrolysis electrode pair 5 was fixed
to the casing 1 made of acrylic resin so that the Ti electrode and
the Ir-coated Ti electrode were substantially parallel to each
other and the interelectrode distance was in the range of 1 mm to 5
mm. Thus, an electrolysis device was produced. A power supply
device and the electrolysis electrode pair 5 were connected to each
other so that the Ti electrode served as a cathode and the
Ir-coated Ti electrode served as an anode.
[0181] Each of electrolysis devices produced with various
inclination angle of about -50.degree. to +50.degree. with respect
to the vertical direction of the electrolysis electrode pair 5 was
installed. A 3% to 4% aqueous sodium chloride solution was supplied
at a constant flow rate to the channel 7 for fluid to be treated
from the lower side. When the electrolysis electrode pair is
disposed in a vertical direction, the inclination angle is
0.degree.. When the electrolysis electrode pair is inclined so that
the Ir-coated Ti electrode (anode) is brought on the upper side,
the inclination angle is a positive angle. When the electrolysis
electrode pair is inclined so that the Ir-coated Ti electrode is
brought on the lower side, the inclination angle is a negative
angle.
[0182] A constant current of 5 A was supplied to the electrolysis
electrode pair 5 from the power supply device to electrolyze the
aqueous sodium chloride solution. The voltage applied was between
about 4 to 5 V. Furthermore, the effective chlorine concentration
(mg/L) of the aqueous solution subjected to electrolysis was
measured.
[0183] FIG. 12 shows the measurement result of the effective
chlorine concentration. This result shows that when the
electrolysis electrode pair 5 was inclined so that the Ir-coated Ti
electrode serving as an anode was brought on the upper side, the
effective chlorine concentration of the aqueous solution subjected
to electrolysis could be increased. Specifically, when the
electrolysis electrode pair 5 was inclined in the range of about
5.degree. to 45.degree., the effective chlorine concentration was
improved by about 5% compared with the case where the electrolysis
electrode pair 5 was disposed in the vertical direction. When the
electrolysis electrode pair 5 was inclined in the range of about
15.degree. to 32.degree., the effective chlorine concentration was
improved by about 10% compared with the case where the electrolysis
electrode pair 5 was disposed in the vertical direction. If the
electrolysis electrode pair 5 was excessively inclined, the
effective chlorine concentration decreased. At an inclination angle
of about 50.degree., the effective chlorine concentration was
substantially equal to that in the case where the electrolysis
electrode pair 5 was disposed in the vertical direction
(0.degree.).
[0184] Therefore, the electrolysis device is desirably disposed so
that the electrolysis electrode pair 5 has an inclination angle of
more than 0.degree. and less than 50.degree. with respect to the
vertical direction. The inclination angle of the electrolysis
electrode pair 5 is preferably 5.degree. to 45.degree. (improved by
about 5%) and more preferably 15.degree. to 32.degree.. It was also
found that when the electrolysis electrode pair 5 was disposed so
that a part of the Ir-coated Ti electrode serving as an anode was
located above the Ti electrode serving as a cathode in the vertical
direction, the effective chlorine concentration of the aqueous
solution subjected to electrolysis could be increased, and thus the
electrolysis efficiency could be improved.
[0185] The same experiment was conducted by using various electrode
materials for generating chlorine, using an aqueous solution
containing a chloride, such as an aqueous sodium chloride solution,
hydrochloric acid, or a mixture of the aqueous sodium chloride
solution and hydrochloric acid, changing the amount of the aqueous
solution fed, and changing the electrolysis conditions (voltage and
current). The same tendency was observed in all the experiments. In
some cases, the effective chlorine concentration in the vertical
direction (0.degree.) and the effective chlorine concentration at
an optimum angle (0.degree. to about 50.degree.) were substantially
equal to each other in the range of measurement errors. Even in
this case, however, the effective chlorine concentration was
clearly decreased when the electrolysis electrode pair was inclined
so that the cathode was brought on the upper side. The effective
chlorine concentration tended to decrease by about 10% at about
23.degree. and by about 20% at about 45.degree. as in FIG. 12.
Therefore, 0.degree. may be an optimum angle under some
electrolysis conditions, but the electrolysis electrode pair is
preferably inclined to some degree so that the anode is brought on
the upper side. This is because, in addition to the assembly
tolerance established when an electrolysis device is installed to
an apparatus, the apparatus is not necessarily used at a strictly
horizontal place in reality. Therefore, when the electrolysis
electrode pair is inclined to the anode side or the cathode side
with respect to the vertical direction (0.degree.) by the same
degree, the electrolysis device is preferably installed while the
electrolysis electrode pair is inclined in advance so that a
decrease in the effective chlorine concentration is suppressed or
the effective chlorine concentration increases. The optimum
inclination varies in accordance with the structure of the
electrolysis device, the composition of an aqueous solution to be
electrolyzed, the amount of a solution fed, the electrolysis
conditions, and the like. Furthermore, as described above, for
example, vibration, swinging, and inclination occur in a practical
environment. In view of the foregoing, for example, when a margin
of 5.degree. is given in an intended usage situation, the
electrolysis device is preferably installed at an optimum angle in
the range of 5.degree. to 45.degree.. Typically, the optimum angle
is expected to be in the range of 20.degree. to 30.degree..
However, the electrolysis electrode pair can be used at an
inclination angle of up to 45.degree. to decrease the height of an
apparatus to which the electrolysis device is installed.
[0186] In Experimental Example 1, an acrylic resin having high
transparency was used for the casing 1 to observe the state of
bubbles. However, it is obvious that the casing 1 may be made of
any material as long as the material has resistance to, for
example, the aqueous solution supplied to the electrolysis device,
various substances generated by electrolysis, and generated gas. If
desired reliability is achieved, polypropylene or the like can be
used. In the case where a chlorine-based aqueous solution or gas is
generated as in Experimental Example 1, the material for the casing
1 is most preferably a vinyl chloride resin in terms of high
resistance, workability, and low cost.
[0187] Although the reason for which the electrolysis efficiency is
improved by inclining the electrolysis electrode pair 5 so that a
part of the anode is located above the cathode in the vertical
direction is still unclear, the following hypothesis is
proposed.
[0188] In the cathode, it is believed that an electrode reaction
represented by the above reaction formula (4) proceeds and H.sub.2
is generated. The generated H.sub.2 is relatively not easily
dissolved and almost all the generated H.sub.2 is present in the
form of air bubbles. Since the cathode is located below the anode
in the vertical direction because of the inclination of the
electrolysis electrode pair 5, the air bubbles of H.sub.2 are
believed to leave from the cathode because of their buoyancy and
move to near the anode. Therefore, the air bubbles generated at the
cathode move so as to cross the aqueous solution flowing in the
flow velocity direction, and thus stirring of the aqueous solution
near the cathode and the aqueous solution near the anode is
facilitated. The air bubbles of H.sub.2 move to near the anode and
also an alkalescent aqueous solution near the cathode is moved to
near the anode. Therefore, the conversion of chlorine gas into
hypochlorous acid or the like represented by the above reaction
formula (2) is facilitated. Furthermore, the movement of the
aqueous solution near the cathode on the upstream side toward the
anode is facilitated with the movement of the air bubbles.
Consequently, the fraction of a liquid component subjected to
electrolysis is decreased in the aqueous solution near the cathode
on the downstream side, which effectively works for
electrolysis.
[0189] FIG. 13 is a schematic view of an interelectrode channel in
the case where the electrolysis electrode pair has an inclination
angle of 0.degree.. When the electrolysis electrode pair is
disposed at an inclination angle of 0.degree., the direction in
which the aqueous solution flows through the interelectrode channel
from the lower side to the upper side matches the direction in
which air bubbles generated on the electrode surface by an
electrolysis reaction float from the lower side to the upper side.
Therefore, as indicated by arrows in FIG. 13, the aqueous solution
and the air bubbles close to the cathode flow through the
interelectrode channel while they are not easily mixed with each
other. The aqueous solution and the air bubbles close to the anode
also flow through the interelectrode channel while they are not
easily mixed with each other.
[0190] In the case where the electrolysis electrode pair is
inclined with respect to the vertical direction so that the anode
serves as an upper electrode, if electrolysis is not performed and
air bubbles are not generated, an aqueous solution is believed to
flow as in FIG. 13. However, when electrolysis is performed, in
particular, when air bubbles are generated, the situation is
totally different.
[0191] In the case where air bubbles float from the cathode toward
the anode in the aqueous solution, the air bubbles and the aqueous
solution having different velocity vectors are resistant to each
other and their momentums are exchanged. For example, it is
well-known that air bubbles in still water move upward because of
their buoyancy and a stream of water is generated along with the
movement.
[0192] A force of upward movement due to buoyancy is exerted on the
air bubbles generated in the inclined interelectrode channel, that
is, in the aqueous solution having a diagonal flux. Therefore, the
direction in which the air bubbles move is not parallel with the
direction in which the aqueous solution flows. The air bubbles move
in a direction from the lower electrode (cathode) toward the upper
electrode (anode), and the direction in which the air bubbles move
is more upward than the direction in which the aqueous solution
flows. Herein, the aqueous solution also moves in a direction from
the lower electrode (cathode) toward the upper electrode (anode)
along with the movement of the air bubbles. This generates a flow
that causes the aqueous solution near the cathode to move to near
the anode. Consequently, products on the anode side and products on
the cathode side are mixed well.
[0193] Next, the case where the electrolysis electrode pair is
inclined so that the cathode serves as an upper electrode, that is,
the case of a negative inclination angle on a graph in FIG. 12 will
be discussed. Air bubbles generated at the anode serving as a lower
electrode are chlorine gas and oxygen gas as represented by the
above reaction formulae (1) and (3), and the chlorine gas readily
dissolves in water and hypochlorous acid is produced as represented
by the above reaction formula (2). Therefore, the amount of air
bubbles generated at the cathode serving as a lower electrode is
smaller than that of air bubbles of H.sub.2 gas generated at the
cathode serving as an upper electrode. Thus, the air bubbles
generated at the lower electrode do not produce a large stirring
effect. A relatively large amount of air bubbles generated at the
cathode serving as an upper electrode move along the surface of the
cathode. This increases the surface area of the cathode coated with
the air bubbles, inhibits the contact between the cathode and the
aqueous solution, and decreases the electrolysis efficiency. This
is believed to be disadvantageous for electrolysis.
[0194] In Experimental Example 1, a preferred result was obtained
by setting the anode as an upper electrode. However, it is found
from this hypothesis that the electrolysis efficiency can be
improved depending on a substance to be electrolyzed by setting, as
a lower electrode, an electrode at which a relatively large amount
of air bubbles is generated and setting, as an upper electrode, an
electrode at which a relatively small amount of air bubbles is
generated.
[0195] To confirm the hypothesis, there were produced an
electrolysis device in which the inclination angle of the
electrolysis electrode pair was set to 0.degree. and the upper end
of the Ir-coated Ti electrode serving as an anode 21 was 1 cm
higher than the upper end of the Ti electrode serving as a cathode
22 as illustrated in FIG. 14(b) and an electrolysis device in which
the inclination angle of the electrolysis electrode pair was set to
0.degree. and the upper end of the cathode 22 was 1 cm higher than
the upper end of the anode 21 as illustrated in FIG. 14(c). An
electrolysis experiment was conducted by supplying an aqueous
sodium chloride solution to the channel 7 for fluid to be treated
in each of the electrolysis devices from the lower side at a
constant flow rate and supplying a constant current of 5 A between
the cathode 22 and the anode 21. Other experimental conditions and
measurement methods were the same as those of the above
electrolysis experiment.
[0196] In the electrolysis experiment that used the electrolysis
device in which the anode 21 was brought on the upper side, the
effective chlorine concentration (mg/L) of the aqueous solution
subjected to electrolysis was about 65 mg/L. In the electrolysis
experiment that used the electrolysis device in which the cathode
22 was brought on the upper side, the effective chlorine
concentration (mg/L) of the aqueous solution subjected to
electrolysis was about 60 mg/L. As a result, an electrolysis
reaction product was obtained in the experiment that used the
electrolysis device in which the anode 21 was brought on the upper
side with an efficiency about 10% higher than the efficiency in the
experiment that used the electrolysis device in which the cathode
22 was brought on the upper side.
[0197] When air bubbles are not generated as illustrated in FIG.
14(a), a stirring and mixing effect produced by air bubbles cannot
be expected. When the amounts of air bubbles generated on both
sides are substantially the same, an effect produced by air bubbles
is believed to be substantially the same regardless of which
electrode is brought above.
[0198] However, the situation is different when the anode 21 and
the cathode 22 having different amounts of air bubbles generated as
in this experiment are used. In this experiment, since chlorine gas
mainly generated at the anode 21 dissolves in the aqueous solution
well and the amount of air bubbles is small, the amount of air
bubbles generated at the cathode 22 at which hydrogen gas is
generated is larger than that at the anode 21. This state is
schematically illustrated in FIG. 14(b) and FIG. 14(c). In the case
where the anode 21 is brought on the upper side as illustrated in
FIG. 14(b), if the amount of air bubbles generated at the cathode
22 is sufficiently large, it is expected that the air bubbles move
to near the anode, which produces a stirring and mixing effect on
the aqueous solution.
[0199] When the cathode 22 is brought on the upper side as
illustrated in FIG. 14(c), air bubbles generated at the cathode 22
cannot move to near the anode, a stirring and mixing effect of the
air bubbles on the aqueous solution is expected to be smaller than
that at least in the case of FIG. 14(b). When the stirring and
mixing effect is small, the aqueous solution subjected to
electrolysis on the lower side of the anode moves upward along the
electrode surface of the anode, and therefore the electrolysis
efficiency is expected to decrease on the upper side of the anode.
When the stirring and mixing effect is large, a fresh raw solution
is supplied to the surface of the anode, and therefore the
electrolysis efficiency is expected to increase. Accordingly, the
stirring and mixing effect of air bubbles on the aqueous solution
qualitatively matches the experimental results.
[0200] In this experiment, a preferred result was obtained by
bringing the anode 21 on the upper side. However, it is found from
this hypothesis that the electrolysis efficiency can be improved
depending on a substance to be electrolyzed by bringing, on the
lower side, an electrode at which a relatively large amount of air
bubbles is generated and bringing, on the upper side, an electrode
at which a relatively small amount of air bubbles is generated.
Experimental Example 2
[0201] A "vertically discharged" electrolysis unit 10 including the
flow inlet 8 and the flow outlet 9 in a channel direction of the
interelectrode channel 6 as illustrated in FIG. 1 was produced. A
"horizontally discharged (upward)" electrolysis unit 10 including
the upstream-side bent channel 25 and the downstream-side bent
channel 26 so that the flow outlet 9 faces upward as illustrated in
FIG. 4 was produced. A "horizontally discharged (downward)"
electrolysis unit 10 including the upstream-side bent channel 25
and the downstream-side bent channel 26 so that the flow outlet 9
faces downward as illustrated in FIG. 5 was produced. An
electrolysis experiment was conducted.
[0202] In the electrolysis experiment, electrolysis was performed
using the electrolysis electrode pair 5 by installing the
electrolysis device 15 so that the electrolysis electrode pair 5
had inclination angles of about 23.degree. and about 45.degree.
with respect to the vertical direction and supplying a 3% to 4%
aqueous sodium chloride solution to the channel 7 for fluid to be
treated from the lower side at a constant flow rate. The effective
chlorine concentration (ppm) of the aqueous solution subjected to
electrolysis was measured. Other conditions were the same as those
in Experimental Example 1. Table 1 shows the results of the
electrolysis experiment.
[0203] As is clear from Table 1, the electrolysis efficiency of the
"horizontally discharged (upward)" electrolysis device is high. The
reason for this is unclear, but may be as follows. When the
upstream-side channel close to the end of the interelectrode
channel on the upstream side is bent to some degree or the
downstream-side channel close to the end of the interelectrode
channel on the downstream side is bent to some degree, the flux or
the flow of air bubbles is randomized and thus the electrolysis
efficiency may be improved.
[0204] To smoothen the flow of air bubbles after a fluid is bent,
the channels on the inlet and outlet sides, in particular, the
channel on the outlet side may be caused to extend in the vertical
direction as illustrated in FIG. 20(a).
[0205] From the viewpoint of ease of mass production, as a
modification, the vertical direction may be made by using a pipe
unit 70 as illustrated in FIGS. 20(b) and 20(c).
TABLE-US-00001 TABLE 1 Horizontally Horizontally Vertically
discharged discharged Inclination discharged (upward) (downward)
angle electrolysis unit electrolysis unit electrolysis unit
23.degree. 73 ppm 77 ppm 70 ppm 45.degree. 66 ppm 73 ppm 59 ppm
Experimental Example 3
[0206] An electrolysis unit 10 illustrated in FIG. 6(a) was
produced and an electrolysis experiment was conducted. The produced
electrolysis unit 10 is constituted by three parts illustrated in
FIGS. 6(b) to 6(d). Two of the three parts are electrode holders 31
and 32 having the same shape and disposed symmetrically about a
point. The remaining one is a spacer 33 disposed between the two
electrode holders. When viewed in a direction in which the
electrolysis electrode pair 5 overlaps each other, at least part of
the spacer 33 overlaps the electrolysis electrode pair 5.
[0207] In the produced electrolysis unit 10, a titanium bolt 41
including a protrusion 35 was used. The electrode holders 31 and 32
and the spacer 33 were made of acrylic resin. The upper electrode 3
serving as an anode was an insoluble electrode (manufactured by
DAISO ENGINEERING Co., Ltd.) for producing sodium hypochlorite. The
lower electrode 4 serving as a cathode was a titanium plate
manufactured by The Nilaco Corporation. The three parts were
assembled so that the interelectrode distance was in the range of 1
mm to 5 mm by adjusting the thickness of the spacer 33. In
Experimental Example 2, since the electrode holders and the like
are made of acrylic resin, the inside of the electrolysis unit 10
can be observed. Herein, the acrylic resin does not transmit light
with a short wavelength, in particular, UV light. This is to reduce
the influence caused by light as much as possible. Therefore, a
material that does not transmit light at all is preferably used in
actual products.
[0208] The electrode holders 31 and 32 and the spacer 33 were fixed
using a bolt 41 and a nut 42 together with a washer, a spring
washer, and an O-ring (not illustrated). In Experimental Example 2,
the electrolysis unit 10 can be disassembled. From the viewpoint of
long-term reliability, a strong adhesive or the like is preferably
used for the adherend of the electrolysis unit 10 to prevent the
leakage of an electrolysis solution. By using an airtight gasket
with chemical resistance as the spacer 33, both thickness
adjustment and sealing can be performed. To reduce the cost by mass
production, the electrolysis unit 10 can also be produced at a time
by molding the parts in one piece.
[0209] For comparison, an electrolysis unit that did not include a
protrusion 35 was also produced and an electrolysis experiment was
conducted. Other configuration was the same as that of the
electrolysis unit 10.
[0210] Electrolysis was performed while a 3% to 4% aqueous NaCl
solution was supplied to the channel 7 for fluid to be treated of
the produced electrolysis unit 10 at 5 to 80 ml/min. The
electrolysis could be performed with a higher electrolysis
efficiency in the electrolysis unit 10 including the protrusion 35
than in the electrolysis unit that did not include the protrusion
35.
Experimental Example 4
[0211] An electrolysis unit 10 illustrated in FIG. 9(a) was
produced and an electrolysis experiment was conducted. The produced
electrolysis unit 10 is constituted by parts illustrated in FIGS.
9(b) to 9(f). The size of an opening in the spacer 33 is smaller
than that of the electrolysis unit 10 illustrated in FIG. 6. The
spacer 33 is disposed so that the spacer 33 and the edges of the
upper electrode 3 and lower electrode 4 overlap each other.
[0212] When a solution to be electrolyzed was an aqueous sodium
chloride solution, the electrolysis efficiency was substantially
the same as that in Experimental Example 3. However, when the
electrolysis solution was obtained by adding hydrochloric acid to
an aqueous sodium chloride solution to make the solution acidic,
the concentration of hypochlorous acid produced in the electrolysis
unit 10 in FIG. 9 was high and the variation in concentration was
small. Therefore, the electrolysis efficiency and the stability of
the concentration of a substance produced were considerably
improved by employing the configuration in FIG. 9.
[0213] This may be because, by employing the configuration in FIG.
9, an electrolysis reaction relatively evenly proceeds at the
electrolysis electrode pair 5 and stirring is also relatively
uniformly performed. Furthermore, when the channel 7 for fluid to
be treated has the configuration illustrated in FIG. 9, stirring
and homogeneity of a fluid to be treated are achieved at a place
other than the interelectrode channel 6. Thus, the substantial
efficiency and stability are believed to be improved.
Experimental Example 5
[0214] A diluted solution containing an electrolysis product was
produced using electrolysis devices 15 illustrated in FIGS. 10(a)
and 10(b). The raw electrolysis solution 52 was a 3% to 4% aqueous
NaCl solution, and electrolysis was performed using the
electrolysis unit 10 illustrated in FIG. 6(a) under conditions that
4000 ppm of hypochlorous acid was theoretically produced. The
treated aqueous solution was diluted with pure water in the
dilution unit 53 to produce a diluted solution. For comparison, a
known electrolysis unit including an electrolysis electrode pair
having an electrode surface parallel to the vertical direction was
installed to the electrolysis device in FIG. 10(a) to produce a
diluted solution.
[0215] In the electrolysis experiment using the known electrolysis
unit, chlorine gas did not sufficiently dissolve in the aqueous
solution in an acidic region of pH 7 or less. Even when air bubbles
were caused to pass through pure water for dilution in the dilution
tank, the chlorine gas concentration near the surface of the
diluted solution was more than 0.5 ppm and in some cases 2 ppm or
more. The production of hypochlorous acid with high concentration
and low pH by electrolysis was not put to practical use. This may
be because, in a known method, chlorine gas was generated at low
pH, which made difficult to efficiently produce a
high-concentration liquid by electrolysis.
[0216] In the electrolysis experiment using the electrolysis device
15 in FIG. 10(a) according to Experimental Example 5, the produced
diluted solution had a pH of 6 to 8, a hypochlorous acid
concentration of 1000 ppm or more, and a chlorine gas concentration
of 0.5 ppm or less near the surface of the diluted solution. In the
electrolysis device 15 of Experimental Example 5, therefore, the
release of chlorine gas was considerably suppressed compared with
comparative examples. In the electrolysis device 15 of Experimental
Example 5, chlorine gas generated by electrolysis efficiently
dissolves in the aqueous solution, and thus the time required until
the concentration of hypochlorous acid in the diluted solution
exceeds 1000 ppm was considerably shortened.
[0217] In the electrolysis experiment using the electrolysis device
15 in FIG. 10(b) according to Experimental Example 5, the chlorine
gas concentration measured near the end of the pipe 57 through
which the diluted solution was discharged was 0.5 ppm or less.
Experimental Example 6
[0218] An electrolysis device illustrated in FIG. 19 was produced.
An electrolysis experiment was performed with various inclination
angles with respect to the vertical direction of the electrolysis
electrode pair 5 as in Experimental Example 1. The electrolysis
electrode pair 5 included an electrode (referred to as a Ti
electrode) formed of a titanium plate and having 5-cm long sides,
1-cm short sides, and a thickness of 1 mm and an electrode
(referred to as an Ir-coated Ti electrode) obtained by coating a
titanium plate having 5-cm long sides, 1-cm short sides, and a
thickness of 1 mm with iridium oxide by a sintering method. The
electrolysis electrode pair 5 was fixed to the casing 1 made of
acrylic resin so that the Ti electrode and the Ir-coated Ti
electrode were substantially parallel to each other and the
interelectrode distance was in the range of 1 mm to 5 mm. Thus, an
electrolysis device was produced. A power supply device 72 and the
electrolysis electrode pair 5 were connected to each other so that
the Ti electrode served as a cathode and the Ir-coated Ti electrode
served as an anode.
[0219] In Experimental Example 6, the electrolysis electrode pair 5
was installed to a so-called batch-type electrolytic cell 74 with
various inclination angles of about -60.degree. to about
+60.degree. with respect to the vertical direction, unlike a closed
channel electrolysis unit in Experimental Example 1 in which
electrodes define a part of a channel and a fluid to be treated is
supplied in substantially the same direction. A 3% to 4% aqueous
sodium chloride solution was charged into the electrolytic cell 74.
When the electrolysis electrode pair 5 is disposed in a vertical
direction, the inclination angle is 0.degree.. When the
electrolysis electrode pair 5 is inclined so that the Ir-coated Ti
electrode (anode) is brought on the upper side, the inclination
angle is a positive angle. When the electrolysis electrode pair 5
is inclined so that the Ir-coated Ti electrode is brought on the
lower side, the inclination angle is a negative angle.
[0220] A constant current of 1 A was supplied to the electrolysis
electrode pair 5 from the power supply device 72 to electrolyze the
aqueous sodium chloride solution. The voltage applied was between
about 4 to 5 V. Furthermore, the effective chlorine concentration
(mg/L) of the aqueous solution subjected to electrolysis was
measured.
[0221] FIG. 18 illustrates the measurement result of the effective
chlorine concentration. This result shows that the effective
chlorine concentration of the aqueous solution subjected to
electrolysis could be improved by inclining the electrolysis
electrode pair 5 so that the Ir-coated Ti electrode serving as an
anode was brought on the lower side as opposed to Experimental
Example 1. Specifically, when the electrolysis electrode pair 5 was
inclined at least up to about -60.degree., the effective chlorine
concentration was improved compared with the case where the
electrolysis electrode pair 5 was disposed in the vertical
direction. When the electrolysis electrode pair 5 was inclined in
the range of about -20.degree. to about -45.degree., the effective
chlorine concentration was improved by about 5% compared with the
case where the electrolysis electrode pair 5 was disposed in the
vertical direction. If the electrolysis electrode pair 5 was
excessively inclined, the effective chlorine concentration tended
to decrease. The effective chlorine concentration at about
-60.degree. was substantially the same as that in the vertical
direction (0.degree.).
[0222] Therefore, the electrolysis electrode pair 5 is desirably
installed to the electrolytic cell 74 so as to have an inclination
angle of more than 0.degree. and less than 60.degree. and
preferably 20.degree. to 45.degree. (about 5% improvement) with
respect to the vertical direction. It was also found that the
effective chlorine concentration of the aqueous solution subjected
to electrolysis could be improved by disposing the electrolysis
electrode pair 5 so that a part of the Ir-coated Ti electrode
serving as an anode was located below the Ti electrode serving as a
cathode in the vertical direction, and thus the electrolysis
efficiency could be improved.
[0223] The direction of the electrolysis electrode pair 5 is either
a direction in which the short sides extend horizontally or a
direction in which the long sides extend horizontally. In both the
directions, the electrolysis efficiency was improved when the
electrolysis electrode pair 5 was inclined so that the cathode was
brought on the upper side.
[0224] In such a batch-type electrolytic cell 74, the electrolysis
efficiency is improved by inclining the electrolysis electrode pair
5 so that a part of the anode located below the cathode in the
vertical direction, unlike the closed channel electrolysis unit.
The reason for the difference is unclear, but the following
hypothesis is considered.
[0225] It is believed that at the cathode, an electrode reaction
proceeds and H.sub.2 is generated as in Experimental Example 1. The
generated H.sub.2 relatively does not easily dissolve and thus
almost all the H.sub.2 is present in the form of air bubbles.
[0226] The batch-type electrolytic cell 74 having a large open area
including the area of side surfaces produces only a small
confinement effect compared with the closed electrolysis unit.
Therefore, the average time for which air bubbles of H.sub.2 are
present between the electrodes is short, and a fresh substance to
be electrolyzed is spontaneously supplied to replace air bubbles of
H.sub.2. Consequently, the electrolysis efficiency is believed to
be improved.
[0227] The amount of the spontaneously supplied substance to be
electrolyzed is not particularly limited, the concentration after
electrolysis between the electrodes, that is, the concentration of
hypochlorous acid is kept relatively low. The chlorine gas
generated at the anode and left without being converted into
hypochlorous acid rises because of its buoyancy and moves toward
the cathode. Herein, an alkalescent aqueous solution near the
cathode moves more slowly than air bubbles of H.sub.2 and chlorine
gas. Therefore, a chance of contact between the alkalescent aqueous
solution and chlorine gas that has come from the anode increases,
which facilitates the conversation of the chlorine gas into
hypochlorous acid and the like.
[0228] When the cathode is brought on the lower side, air bubbles
of H.sub.2 generated move toward the anode because of their
buoyancy and a space between the electrodes is filled with the air
bubbles of H.sub.2. In some cases, the air bubbles adhere to and
remain on the anode, which considerably decreases the area of the
anode that contacts the substance to be electrolyzed. In the
experiment, at an angle of 80.degree. or more, almost all the
surface of the anode was covered with air bubbles of H.sub.2 and
the electrolysis efficiency was considerably decreased. The
electrolysis efficiency is believed to be decreased by, for
example, a decrease in the amount of the substance to be
electrolyzed between the electrodes, a decrease in the effective
electrode surface area due to air bubbles, and the inhibition of
flow-in of a fresh substance to be electrolyzed.
[0229] The aqueous solution near the anode and the chlorine gas
generated at the anode flow out so as to be forced out by the air
bubbles of H.sub.2 from the space between the electrodes to an open
surface such as a side surface. Therefore, the stirring of the
aqueous solution near the cathode and the aqueous solution near the
anode is not facilitated unlike the closed electrolysis unit, and
the conversation of chlorine gas into hypochlorous acid and the
like is also not facilitated. In some cases, the chlorine gas
itself is released from the substance to be electrolyzed to a
space, and thus the effective chlorine concentration is believed to
be decreased.
[0230] In the case of the closed electrolysis unit, the air bubbles
of H.sub.2 is held between the electrodes regardless of the manner
of inclination and the supply amount of a substance to be
electrolyzed is limited. In such a closed electrolysis unit, when
the cathode is brought on the upper side, the separation of H.sub.2
from the cathode is delayed. Consequently, the effective electrode
area of the cathode is decreased by an H.sub.2 covering effect and
the approach of the substance to be electrolyzed near the surface
of the cathode is prevented. Thus, the electrolysis efficiency is
believed to be decreased. When the cathode is brought on the lower
side, the separation of H.sub.2 is facilitated. Consequently, the
decrease in the effective electrode area of the cathode due to an
H.sub.2 covering effect is suppressed and a fresh substance to be
electrolyzed is supplied to the surface of the cathode.
Furthermore, the air bubbles of H.sub.2 move to near the anode and
the alkalescent aqueous solution near the cathode is also carried
to near the anode. Thus, the conversation of chlorine gas into
hypochlorous acid and the like is facilitated. Furthermore, the
movement of the aqueous solution located upstream of the cathode in
the direction toward the anode is facilitated with the movement of
the air bubbles. Therefore, the aqueous solution located downstream
of the cathode contains a small fraction of a liquid component
subjected to electrolysis. This effectively works for
electrolysis.
[0231] In the closed electrolysis unit, the amount of the substance
to be electrolyzed that is supplied to the electrolysis unit is
limited. Therefore, the concentration of the electrolyzed
substance, that is, the concentration of hypochlorous acid in this
Experimental Example tends to increase. An excessive increase in
the concentration of hypochlorous acid decreases the electrolysis
efficiency. To prevent this, at least part of chlorine gas
generated at the anode is released from the outlet without being
converted into hypochlorous acid in the electrolysis unit and
converted into hypochlorous acid through contact with water after
the dilution unit. Consequently, the increase in the concentration
of hypochlorous acid in the electrolysis unit is suppressed. Thus,
the electrolysis efficiency is believed to be improved.
[0232] As described above, the conditions that the electrolysis
efficiency is improved vary depending on the cases.
[0233] The case where the electrode pair is desirably inclined so
that the anode is located above the cathode is as follows: (i) a
closed electrolysis unit is employed in which the electrodes
substantially serve as an electrolytic cell or constitute a part of
wall surfaces of a channel, (ii) the electrolysis unit includes an
inlet for substances to be electrolyzed and an outlet for
substances produced by electrolysis and unelectrolyzed substances,
and (iii) the electrolysis unit includes at least one of means for
supplying the substances to be electrolyzed from the inlet by force
and means for drawing out the substances produced by electrolysis
and the unelectrolyzed substances from the outlet by force.
[0234] Examples of the means for supplying the substance by force
include feeding the substance to the inlet with a pump, suctioning
the substance from the outlet with a pump, employing a structure in
which a Venturi effect is produced by the dilution unit and the
periphery thereof and suctioning the substance from the outlet, and
disposing a tank on the upper side and feeding the substance by
gravity. A pump is preferably used because the most stable feeding
can be achieved. If variation is allowable to some degree, a
structure that uses a Venturi effect or gravity is preferably
employed without using a pump because energy for operating a pump
is unnecessary, which saves the energy and reduces the cost of the
pump. Obviously, some or all of the pump, the Venturi effect, and
the gravity may be combined with each other.
[0235] For example, Experimental Example 1 employs a structure in
which a tube pump is used to supply a substance at a constant rate
as much as possible.
[0236] When at least one of (a) the case where electrolysis is
performed in which air bubbles are generated at the cathode, (b)
the case where a substance generated at the anode or a substance
obtained by a chemical reaction of the substance is obtained, (c)
the case where the outlet of the electrolysis unit includes a
dilution unit, and (d) the case where the concentration of a
substance produced by electrolysis is relatively high in the
electrolysis unit is satisfied, the electrode pair is believed to
be desirably inclined so that the anode is located above the
cathode. When a plurality of (a) to (d) are satisfied or when all
of (a) to (d) are satisfied, the electrode pair is also believed to
be desirably inclined so that the anode is located above the
cathode.
[0237] If there is no means for supplying the substance to be
electrolyzed to a space between the electrodes by force or no means
for suctioning the substance by force in a structure in which the
electrolysis electrode pair is substantially disposed in the stored
substance to be electrolyzed, the electrode pair is believed to be
desirably inclined so that the anode is located below the
cathode.
[0238] In this structure, the substance to be electrolyzed is
supplied in a passive manner with the rise of air bubbles.
[0239] Chlorine gas unconverted into hypochlorous acid is easily
released to a gas phase within a short time compared with the case
where the closed electrolysis unit is employed.
[0240] The release to a gas phase is further suppressed in the
closed electrolysis unit because there are many factors of
facilitating conversation into hypochlorous acid. For example, the
supply amount of the substance to be electrolyzed is limited and
thus conversation into hypochlorous acid is easily caused by a
confinement effect in the electrolysis unit and a stirring effect
produced by air bubbles of H.sub.2. Furthermore, conversation of
chlorine gas into hypochlorous acid in the dilution unit is
facilitated. In addition, conversation of chlorine gas into
hypochlorous acid is also caused in a line through which dilution
water flows after the dilution unit.
REFERENCE SIGNS LIST
[0241] 1 casing [0242] 3 upper electrode [0243] 4 lower electrode
[0244] 5 electrolysis electrode pair [0245] 6 interelectrode
channel [0246] 7 channel for fluid to be treated [0247] 8 flow
inlet [0248] 9 flow outlet [0249] 10 electrolysis unit [0250] 11
air bubbles [0251] 15 electrolysis device [0252] 16 overlap region
when viewed in vertical direction [0253] 17 overlap region when
viewed in direction perpendicular to principal surface of lower
electrode [0254] 21 anode [0255] 22 cathode [0256] 25 upstream-side
bent channel [0257] 26 downstream-side bent channel [0258] 30
electrode holder [0259] 31 first electrode holder [0260] 32 second
electrode holder [0261] 33 spacer [0262] 35 protrusion [0263] 36
opening of spacer [0264] 37 groove of electrode holder [0265] 41
bolt [0266] 42 nut [0267] 43 clearance hole [0268] 45 electrode
terminal [0269] 47 O-ring [0270] 48 washer [0271] 49 spring washer
[0272] 51 raw electrolysis solution tank [0273] 52 raw electrolysis
solution [0274] 53 dilution unit [0275] 54 dilution tank [0276] 55
stored water [0277] 57 pipe [0278] 59 mixing unit [0279] 61 casing
[0280] 62 feed water inlet [0281] 63 discharge outlet [0282] 64
switch [0283] 65 pipe [0284] 66 solenoid-controlled valve [0285] 67
raw solution tank [0286] 68 pump [0287] 70 pipe unit [0288] 72
power supply device [0289] 74 electrolytic cell [0290] 75 fluid to
be treated [0291] 77 wiring line [0292] 100 electrolysis device
[0293] 101 casing [0294] 103 first electrode [0295] 104 second
electrode [0296] 106 first wiring line [0297] 107 second wiring
line [0298] 108 supply inlet [0299] 109 discharge outlet [0300] 111
casing [0301] 112 feed water inlet [0302] 113 discharge outlet
[0303] 114 switch [0304] 115 pipe [0305] 116 solenoid-controlled
valve [0306] 117 raw solution tank [0307] 118 pump [0308] 120
electrolyzed water-producing device
* * * * *