JP2003129265A - Water electrolyzer and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water electrolyzer made proof against the adhesion and buildup of impurity ions on a solid polyelectrolyte membrane to keep its electrolytic performances stable and satisfactory and being capable of a long- term continuous operation in spite of no using an inexpensive heat-resistant ion exchange resin and to provide a method for operating the same. SOLUTION: The water electrolyzer is the one provided with a cation exchange resin tank 40 for removing cations; an acid storage tank 50 and an acid feed sluice valve 52 for adding an acid; a pH meter that measures the pH value of the water discharged from an anode-side gas/liquid separator 25; a discharge pipe 44 and a discharge control valve 46 for discharging water from an anode chamber; a flow control valve 48 for feed water for electrolysis; and a controller 45a that when the pH value measured with the pH meter 54 reached a specified value, controls the valve 46 to discharge water from the anode chamber, shuts the sluice valve 52, and controls the valve 48 to control the flow rate of the feed water for electrolysis, wherein acidic water containing a large quantity of anions is fed into the anode chamber, and the feed water for electrolysis is set in a specified pH range in consideration for corrosion prevention.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a water electrolysis apparatus using a solid polymer electrolyte membrane and a method of operating the same.

[0002]

2. Description of the Related Art A solid polymer electrolyte membrane is used as a diaphragm to separate an anode side and a cathode side, and electrolysis is performed while supplying pure water or water containing ions to the anode side to generate oxygen gas from the anode side. In recent years, development of a water electrolysis device configured to generate hydrogen gas from the cathode side has been advanced, and various proposals have been made regarding its system configuration, stack structure, operating method, etc. 2-51263
Full text specification, Japanese Utility Model Publication No. 3-74670 full text specification, JP-A-7-252682, JP-A-8-311.
676, JP 2000-54175, etc.).

The above-mentioned Japanese Patent Laid-Open No. 2000-54175 describes a schematic system configuration, and the full-text specification of the above-mentioned Japanese Utility Model Application Laid-Open No. 2-51263 discloses an ion exchange resin tank at the feed water inlet. A system configuration is described which, when provided, prevents impurity ions contained in electrolyzed water from adhering and accumulating on the solid polymer electrolyte membrane and deteriorating electrolytic performance. Furthermore, the full-text specification of Jitsukaihei 3-74670 describes that a cation exchange resin tank is used as the ion exchange resin tank.

FIG. 3 shows a system diagram of a water electrolysis apparatus using a conventional solid polymer electrolyte membrane, which is schematically described with reference to the prior art. In FIG. 3, the water electrolysis tank 1 is divided into a cathode chamber 1a and an anode chamber 1b by a solid polymer electrolyte membrane 3. The cathode chamber 1a and the anode chamber 1b
Are each provided with a catalyst electrode and a porous power feeder which are not shown.

Pure water flowing into the water electrolysis cell 1 through the inlet line 7 by the pump 5 is electrolyzed, and hydrogen is generated in the cathode chamber 1a. On the other hand, oxygen is generated in the anode chamber 1b. When hydrogen ions move from the anode chamber 1b to the cathode chamber 1a, water is also simultaneously caused by the electroosmosis phenomenon in the cathode chamber 1a.
Move to a. There is a type of water electrolysis tank in which pure water introduced into the water electrolysis tank 1 is introduced into the cathode chamber 1a instead of the anode chamber 1b.

The hydrogen / water two-phase flow from the cathode chamber 1a enters the cathode side gas-liquid separator 11 through the outlet line 9 and is separated into gaseous hydrogen and water. The water separated in the cathode-side gas-liquid separator 11 reaches the suction side of the pump 5 through the cathode water return line 13, and is supplied to the water electrolysis tank 1 through the inlet line 7 by the pump 5 again. Usually line 13
Although a sluice valve is provided on the top, illustration is omitted.

On the other hand, the separated hydrogen (gas) passes through the outlet line 15 and the pressure control valve 17 in sequence and the hydrogen line 1
It flows to 9 and goes to an appropriate recovery device. A pressure relief valve 21 is provided in the outlet line 15 to prevent an excessive pressure rise.

On the other hand, the oxygen / water two-phase flow from the anode chamber 1b enters the anode side gas-liquid separator 25 through the outlet line 23,
It is divided into gaseous oxygen and water. The water separated in the separator 25 reaches the suction side of the pump 5 through the return line 27, and is again supplied to the water electrolysis tank 1 through the inlet line 7 by the pump 5.

On the other hand, the separated oxygen (gas) passes through the outlet line 29 and the pressure control valve 31 in sequence and the oxygen line 3
It flows to 3 and goes to an appropriate recovery device. The outlet line 29 is also provided with a pressure relief valve 35 to prevent an excessive increase in pressure. Further, a differential pressure converter 37 for measuring the differential pressure between the outlet lines 15 and 29 is provided, and the pressure control valve 31 is operated by using the differential pressure signal, and the cathode chamber 1a and the anode chamber 1 in the water electrolysis tank 1 are operated. 1b and a small differential pressure.

In FIG. 3, reference numeral 20 denotes a pure water supply device, and 14
Is a pure water supply pump, and 30 is an ion exchange resin tank (or a cation exchange resin tank). This ion exchange resin tank 30
The significance of the provision will be described below.

In the structure shown in FIG. 3, the pure water supplied from the pure water supply device 20 into the anode-side gas-liquid separator 25 by using the pure water supply pump 14 is decomposed by electrolysis into oxygen and hydrogen. In this process, a trace amount of impurities contained in the water remains in the anode chamber 1b, but the water in the anode chamber 1b is removed from the anode chamber 1b, and passes through the line 23 and the anode-side gas-liquid separator 25. Then, it passes through the ion exchange resin tank 30 and is returned to the anode chamber 1b again. As a result, the impurity ions from the water consumed by the electrolysis are removed by the ion exchange resin tank 30. That is, the ion exchange resin tank 30
By providing, the concentration of impurity ions in the electrolysis water supplied into the anode chamber 1b can be prevented from increasing. Since the impurity ions are mainly cations, 3
0 is preferably a cation exchange resin tank.

When the concentration of the impurity ions is increased, the electrolysis voltage is increased and the electrolysis performance is deteriorated. However, as described above, the water in the electrolysis tank is placed in the ion exchange resin tank 30 in the circulation path of pure water. It is possible to prevent impurity ions from being removed by returning them to the electrolytic cell through the electrolytic cell, and to prevent deterioration of electrolytic performance due to accumulation of impurity ions in the solid polymer electrolyte membrane.

As described above, when hydrogen ions move from the anode chamber 1b to the cathode chamber 1a, water also moves to the cathode chamber 1a at the same time due to the electroosmosis phenomenon. However, there are impurity ions in the water. However, it is attached to the solid polymer electrolyte membrane and removed. Therefore, the water stored in the cathode-side gas-liquid separator 11 does not contain impurity ions. Therefore, as shown in FIG. 3, the water in the cathode-side gas-liquid separator 11 is
It is possible to directly flow back to the anode chamber 1b without passing through the ion-exchange resin container 30.

[0014]

By the way, the structure of the water electrolysis apparatus shown in FIG. 3 has the following problems. That is, since the operating temperature of the water electrolysis device is usually about 80 ° C., the ion exchange resin or cation exchange resin used in the conventional water electrolysis device needs to use a heat resistant exchange resin, and is expensive. . In addition, if you continue to use for a certain period of time, the impurity ion removal performance will decrease, so
There is a problem that a continuous water electrolysis operation cannot be performed because a regeneration treatment of removing from the water electrolysis device, washing with acid, and then washing with pure water is required. The problem of this regeneration treatment can be covered by preparing two ion-exchange resins and using them in alternation, but the cost is further increased when the heat-resistant exchange resin is used.

The present invention has been made to solve the above problems, and an object of the present invention is to prevent the adhesion and accumulation of impurity ions on the solid polymer electrolyte membrane so that the electrolytic performance is improved. It is intended to provide a water electrolysis apparatus that can be stably and satisfactorily maintained and that can be continuously operated for a long period of time without using an expensive heat-resistant ion exchange resin, and an operating method thereof.

[0016]

In order to solve the above-mentioned problems, the present invention provides a water electrolysis tank whose interior is divided into an anode chamber and a cathode chamber by a solid polymer electrolyte membrane, and an anode-side gas-liquid separator. In a method of operating a water electrolysis apparatus including a cathode-side gas-liquid separator, tap water as feed water is brought into contact with a cation exchange resin to remove cations, and water supplied to the anode chamber as electrolysis water. Water electrolysis is performed, and when the cation concentration of the water discharged from the anode chamber rises and reaches a predetermined value, the water in the anode chamber is discharged and the water for electrolysis is replenished with this discharge. (The invention of claim 1).

As an embodiment of the invention of claim 1, the invention of claim 2 below is preferable. That is, in the method for operating a water electrolysis apparatus according to claim 1, the predetermined value of the cation concentration is set by a pH value previously obtained by correlation with the cation concentration, and the pH value is lowered to set a lower limit. When the value reaches a certain value, the water in the anode chamber is discharged, and when the pH value rises by reaching the upper limit set value by replenishing water for electrolysis, the discharge of the water in the anode chamber is stopped.

When acidic water containing a large amount of anions is supplied into the anode chamber, the concentration of hydrogen ions in the electrolyzed water becomes 100 to 1000 times that of pure water.
Trace amounts of Na ions, K ions, Ca ions, Mg ions, and metal ions are easily desorbed from the membrane electrode assembly, and it is possible to prevent impurity ions from adhering and accumulating on the electrolyte membrane. Further, by supplying acidic water containing a large amount of anions into the anode chamber, cations already attached to the surface of the electrode on the anode side and the ion exchange membrane are desorbed into the supplied water.

Although water is consumed by electrolysis to lower the pH value, the pH value is kept at 2 to 3 by discharging the water to remove cations and supplying acidified water to prevent corrosion of the wetted part. , Cations are discharged, and electrolysis can be continuously performed at a low voltage. In addition, in order to appropriately adjust the pH value, it is preferable to adjust by adding an acid as in the invention described later.

According to the invention of claim 1 or 2, it is possible to prevent the adhesion and accumulation of impurity ions from adhering to the solid polymer electrolyte membrane, and to maintain stable electrolysis performance. Further, long-term continuous operation becomes possible without using expensive heat-resistant ion exchange resin. Incidentally, even if the above invention is applied to a system in which electrolysis water is supplied to the cathode chamber instead of the anode chamber and electrolyzed, the electrolysis water is transferred to the anode chamber through the electrolyte membrane, so that the same effect as above is obtained. can get.

Further, in the method for operating a water electrolysis apparatus according to claim 1 or 2, water in the cathode side gas-liquid separator is returned to the anode chamber (invention of claim 3).

According to the third aspect of the invention, the cathode water from which the impurity ions have been removed is returned to the anode chamber, so that the concentration of the impurity ions in the water in the anode chamber should be kept below a predetermined value for a longer time. It is possible to reduce the amount of electrolytic water to be supplied.
Although the electrolyzing water to be replenished is at room temperature, it is produced by the cation exchange resin, so the maintenance interval of the cation exchange resin can be extended by saving the replenishment water.

Further, as an apparatus for carrying out the operating method, the invention of claim 4 below is preferable. That is, a water electrolysis apparatus for carrying out the method of operating a water electrolysis apparatus according to claim 2, wherein a cation exchange resin tank for removing cations by contacting tap water as feed water, and the anode A pH meter for measuring the pH value of the water discharged from the chamber,
A discharge pipe and a discharge control valve for discharging water in the anode chamber, a water flow control valve for electrolysis, and when the pH measured value of the pH meter reaches a predetermined value, the discharge control valve is operated to operate in the anode chamber. A controller for discharging water and operating the electrolysis water flow rate control valve to adjust the flow rate of electrolysis water.

Further, as the invention relating to the addition of the acid, the inventions of claims 5 to 10 below are preferable. That is,
In a method of operating a water electrolysis apparatus including a water electrolysis tank in which the interior is divided into an anode chamber and a cathode chamber by a solid polymer electrolyte membrane, and an anode-side gas-liquid separator and a cathode-side gas-liquid separator,
After tap water as feed water is contacted with a cation exchange resin to remove cations, acid is added to the anode chamber as water for electrolysis, which is acidified to such an extent that the wetted material does not corrode. Water electrolysis is performed, and when the pH value of the water mixed with the water discharged from the anode chamber and supplied to the anode chamber decreases to a predetermined value, the addition of acid is stopped and the water in the anode chamber is stopped. Is discharged and the water for electrolysis is replenished with this discharge (the invention of claim 5).

Further, in the method for operating a water electrolysis apparatus according to claim 5, the addition of acid is stopped and the water in the anode chamber is discharged when the pH value reaches a lower limit set value. Then, when the pH value rises and reaches the upper limit set value by replenishing the electrolyzing water, the discharge of water in the anode chamber is stopped and the addition of the acid is restarted (claim 6). invention).

The functions and effects of the inventions according to claims 5 to 6 are the same as those described above, and a description thereof will be omitted. As the acid, sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, acetic acid or the like can be used, and it is preferable that Na, K, Ca, Mg, metal and the like are not contained as impurities.

Further, in the method for operating a water electrolysis apparatus according to claim 5 or 6, instead of the step of contacting the tap water with a cation exchange resin to remove cations, cation exchange and anion exchange. This is a pure water purification step of contacting with an ion exchange resin having both the above functions (the invention of claim 7).
When an acid is added to adjust the water for electrolysis, the cation exchange resin can be replaced with a normal ion exchange resin as described above.

Further, in the method for operating a water electrolysis apparatus according to claim 2 or 6, the lower limit set value of the pH value is 1.5 and the upper limit set value is 2.0 (the invention of claim 8). ).

As the acid addition type apparatus, the inventions of claims 9 to 10 below are preferable. That is, a water electrolysis apparatus for carrying out the method for operating a water electrolysis apparatus according to claim 5, wherein a cation exchange resin tank for removing cations by contacting with tap water as feed water, and an acid Acid storage tank for addition and acid supply sluice valve, pH meter for measuring pH value of water discharged from the anode-side gas-liquid separator, discharge pipe and discharge control valve for discharging water in the anode chamber, and electrolysis When the pH measured value of the water flow rate control valve and the pH meter reaches a predetermined value, the discharge control valve is operated to discharge water in the anode chamber, and the acid supply partition valve is closed to set the flow rate of electrolysis water. A control device for operating a control valve to adjust the flow rate of electrolyzing water is provided (the invention of claim 9).

Further, in the water electrolysis apparatus according to claim 9, instead of a cation exchange resin tank for contacting the tap water to remove cations, both functions of cation exchange and anion exchange are provided. An ion exchange resin tank having the above (claim 10).

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. In the water electrolysis apparatus shown in FIGS. 1 and 2, members having the same functions as the members shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. 1 and 2, the hydrogen gas and oxygen gas systems in FIG. 3 are partially omitted.

First, the embodiment of FIG. 1 will be described.
1 is different from the system of the water electrolysis apparatus of FIG.
A cation exchange resin tank 40 for removing cations, and a pH meter 5 for measuring the pH value of water discharged from the anode chamber 1b.
4, the discharge pipe 44 and the discharge control valve 46 for discharging the water in the anode chamber, the electrolysis water flow rate control valve 48, and the discharge control valve 46 when the pH measurement value of the pH meter 54 reaches a predetermined value. The control unit 45 is operated to discharge water in the anode chamber and to operate the electrolysis water flow rate control valve 48 to adjust the flow rate of electrolysis water. 42 is a water supply tank for electrolysis water, and 18 is a tap water supply port. In addition, in FIG. 1, the position of the pH meter 54 may be provided on the outlet line 23 from the anode chamber.

In the above structure, tap water flows into the cation exchange resin tank 40 from the water supply port 18, and acidic water containing a large amount of anions from which cations have been removed is stored in the water supply tank 42. This water is supplied to the anode gas-liquid separator 25 by the supply pump 14 and flows into the anode chamber 1b of the water electrolysis tank 1 by the circulation pump 5 to be electrolyzed. As a result, hydrogen is generated in the cathode chamber 1a. On the other hand, oxygen is generated in the anode chamber 1b.

When hydrogen ions move from the anode chamber to the cathode chamber, water also moves to the cathode chamber due to the electroosmosis phenomenon. Although a small amount of cations remain on the anode side in this process, the water supplied from the water supply tank 42 contains a large amount of anions from which the cations have been removed, for example, is acidic at pH 2 to 3, and thus the remaining cations Remains dissolved in water without accumulating and accumulating on the cation exchange membrane as the electrolyte membrane 3.
The water having a high concentration of cations is discharged by a discharge pipe 44 attached to the anode chamber 1b, and acidic water containing a large amount of anions from which the cations have been removed is supplied from the water supply tank 42 to reduce the concentration of cations. It is possible to prevent cations from adhering to lower the electrolytic performance and prevent the liquid contact material from being corroded by keeping the pH value of water in a suitable range. .

Next, the embodiment of FIG. 2 will be described.
The main points of the system of FIG. 2 different from those of FIG. 3 are a cation exchange resin tank 40 for removing cations, an acid storage tank 50 for adding an acid and an acid supply sluice valve 52, and an anode-side gas-liquid separator 25. PH meter 54 for measuring the pH value of water discharged from the discharge chamber, discharge pipe 44 and discharge control valve 46 for discharging water in the anode chamber, electrolysis water flow rate control valve 48, and pH measured value of pH meter 54 are predetermined. When the value is reached, the discharge control valve 46 is operated to discharge the water in the anode chamber, the acid supply partition valve 52 is closed, and the electrolysis water flow control valve 48 is operated to adjust the flow rate of electrolysis water. 1 is different from that of FIG. 1 in that an acid addition system is added and the configuration of the control device is different. Since the operation and action of FIG. 2 are the same as those described above, the description thereof will be omitted.

[0036]

As described above, according to the present invention, an acid is added to water for electrolysis and / or an acid water containing anions is removed by contacting with a cation exchange resin to remove cations. In addition to supplying to the anode chamber, in consideration of anticorrosion, in order to bring the electrolyzing water into a predetermined pH value range, the water in the anode chamber was discharged, and it was decided to control to supply the discharged water. It is possible to prevent cations contained in electrolyzed water from adhering to and accumulating on the solid polymer electrolyte membrane.

Therefore, it is possible to electrolyze in a good state without increasing the electrolysis voltage and decreasing the electrolysis performance. In addition, since a cation exchange resin tank was installed outside the anode water recirculation system of the water electrolysis tank, a water electrolysis device that can be operated continuously for a long time without using expensive heat-resistant ion exchange resin and its operation A method can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of a water electrolysis device of the present invention.

FIG. 2 is a system diagram of a different embodiment of the water electrolysis apparatus of the present invention.

FIG. 3 is a system diagram showing an example of a conventional water electrolysis device.

[Explanation of symbols]

1: Water electrolysis tank, 1a: Cathode chamber, 1b: Anode chamber, 3: Solid polymer electrolyte membrane, 11: Cathode side gas-liquid separator, 13: Cathode water return line, 25: Anode side gas-liquid separator, 40 : Cation exchange resin tank, 44: discharge pipe, 45, 45a: control device, 46: discharge control valve, 48: electrolysis water flow control valve, 5
0: Acid storage tank, 52: Acid supply sluice valve, 54: pH meter.

Claims (10)

[Claims] 1. An operation of a water electrolysis apparatus comprising a water electrolysis tank whose interior is divided into an anode chamber and a cathode chamber by a solid polymer electrolyte membrane, and an anode-side gas-liquid separator and a cathode-side gas-liquid separator. In the method, tap water as feed water is brought into contact with a cation exchange resin to remove cations, and water is supplied to the anode chamber as electrolysis water to perform water electrolysis, and the water discharged from the anode chamber is treated with cations. A method of operating a water electrolysis device, characterized in that, when the ion concentration rises to reach a predetermined value, the water in the anode chamber is discharged, and the water for electrolysis is replenished with this discharge. 2. The method for operating a water electrolysis apparatus according to claim 1, wherein the predetermined value of the cation concentration is set by a pH value previously obtained by correlation with the cation concentration,
When the pH value decreases and reaches the lower limit set value, the water in the anode chamber is discharged and the pH is adjusted by replenishing the electrolysis water.
A method of operating a water electrolysis device, characterized in that the discharge of water in the anode chamber is stopped when the value increases and reaches the upper limit set value. 3. The method of operating a water electrolysis device according to claim 1, wherein the water in the cathode-side gas-liquid separator is returned to the anode chamber. 4. A water electrolysis apparatus for carrying out the method of operating a water electrolysis apparatus according to claim 2, wherein a cation-exchange resin tank for contacting tap water as supply water to remove cations is provided. A pH meter for measuring a pH value of water discharged from the anode chamber, a discharge pipe and a discharge control valve for discharging water in the anode chamber, a water flow control valve for electrolysis, and a pH measured value of the pH meter. When the predetermined value is reached, the discharge control valve is operated to discharge the water in the anode chamber,
And a controller for operating the electrolysis water flow rate control valve to adjust the flow rate of electrolysis water. 5. An operation of a water electrolysis apparatus comprising a water electrolysis tank whose interior is divided into an anode chamber and a cathode chamber by a solid polymer electrolyte membrane, and an anode-side gas-liquid separator and a cathode-side gas-liquid separator. In the method, tap water as feed water is brought into contact with a cation exchange resin to remove cations, and then acid is added to the anode chamber as water for electrolysis, which is acidified to such an extent that the wetted material does not corrode. When the pH value of the water supplied to perform the water electrolysis and mixed with the water discharged from the anode chamber and supplied to the anode chamber decreases to a predetermined value, the addition of the acid is stopped, and A method for operating a water electrolysis device, characterized in that water in a room is discharged and the water for electrolysis is replenished with the discharge. 6. The method for operating a water electrolysis apparatus according to claim 5, wherein the addition of acid is stopped and the water in the anode chamber is discharged when the pH value reaches a lower limit set value. When the pH value rises by replenishing water for electrolysis and reaches the upper limit set value, the discharge of water in the anode chamber is stopped, and the addition of acid is restarted. how to drive. 7. The method of operating a water electrolysis apparatus according to claim 5, wherein instead of the step of contacting the tap water with a cation exchange resin to remove cations, cation exchange and anion exchange. A method of operating a water electrolysis device, which comprises performing a deionization step of contacting an ion exchange resin having both of the above functions. 8. The method for operating a water electrolysis apparatus according to claim 2 or 6, wherein the lower limit set value of the pH value is 1.5 and the upper limit set value is 2.0. How to operate the device. 9. A water electrolysis apparatus for carrying out the method of operating a water electrolysis apparatus according to claim 5, wherein the cation exchange resin tank is contacted with tap water as feed water to remove cations. An acid storage tank for adding an acid and an acid supply sluice valve, a pH meter for measuring the pH value of water discharged from the anode-side gas-liquid separator, and a discharge pipe and discharge control valve for discharging water in the anode chamber A water flow control valve for electrolysis, when the pH measurement value of the pH meter reaches a predetermined value, the discharge control valve is operated to discharge water in the anode chamber, and the acid supply sluice valve is closed, A water electrolysis apparatus comprising: a control device that operates a water flow control valve for electrolysis to adjust the flow rate of electrolysis water. 10. The water electrolysis apparatus according to claim 9, wherein the cation exchange resin tank for contacting the tap water to remove cations is replaced with both cation exchange and anion exchange functions. A water electrolysis device comprising an ion-exchange resin tank having the same.