JP3750802B2 - Water electrolyzer and its operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water electrolysis apparatus using an electrolyte membrane such as a solid polymer and an operation method thereof.
[0002]
[Prior art]
An electrolyte membrane such as a solid polymer is separated into an anode (anode) side and a cathode (cathode) side using an electrolyte membrane, and electrolysis is performed while supplying pure water or water containing ions to the anode side, and oxygen is supplied from the anode side. In recent years, development of water electrolyzers configured to generate hydrogen gas from the cathode side has been advanced, and various proposals have been made regarding the system configuration, stack structure, operation method, and the like (for example, JP-A-2-512263, Japanese Patent Application Laid-Open No. 7-252682, Japanese Patent Application Laid-Open No. 8-31676, Japanese Patent Application Laid-Open No. 9-14379, Japanese Patent Application Laid-Open No. 2000-54175, and the like.
[0003]
The above Japanese Patent Laid-Open No. 2000-54175 describes a schematic system configuration, and the full texts of the above Japanese Patent Laid-Open No. 9-14379 and Japanese Utility Model Laid-Open No. 2-51263 include a feed water inlet. A system configuration is described in which, by providing an ion exchange resin tank, impurity ions contained in water to be electrolyzed are prevented from adhering and accumulating on the solid polymer electrolyte membrane to deteriorate electrolytic performance.
[0004]
FIG. 2 shows a system diagram of a water electrolysis apparatus using a conventional solid polymer electrolyte membrane schematically described with reference to the prior art. In FIG. 2, the water electrolysis cell 1 is divided into a cathode chamber and an anode chamber by a solid polymer electrolyte membrane. Each of the cathode chamber and the anode chamber includes a catalyst electrode and a porous power feeder (not shown).
[0005]
The solid polymer electrolyte membrane is widely used for industrial purposes, and a typical example is a perfluorocarbon sulfonic acid membrane. A highly conductive material such as a titanium fiber or a stainless fiber sintered plate is used as the power feeder. The water supplied to the anode side is decomposed by the reaction of 2H ₂ 0 → 0 ₂ + 4H ⁺ + 4e ⁻ to generate oxygen. H ⁺ undergoes a reaction of 4H ⁺ + 4e ⁻ → 2H ₂ on the cathode side via the sulfone group of the electrolyte membrane, and hydrogen gas is generated.
[0006]
In FIG. 2, on the anode side of a water electrolysis cell (hereinafter also simply referred to as an electrolysis cell) 1, pure water that has passed through a pure water device 2 is supplied from the outside via a supply pipe 4 by a supply pump 3. Supplied. Pure water in each electrode of the electrolysis cell is circulated by the anode side circulation pump 5 and the cathode side circulation pump 6 via the electrolysis cell inlet pipes 7 and 8, the electrolysis cell outlet pipes 11 and 12, and the return pipes 9 and 10. Is done. The outlet pipes 11 and 12 of the electrolysis cell are connected to gas-liquid separators 13 and 14.
[0007]
From the gas-liquid separators 13 and 14, pipes 15 and 16 for taking out the separated generated gas (hydrogen / oxygen) are installed in addition to the return pipes 9 and 10 to the electrolysis cell inlet, and the gas coolers 17 and 18 are connected to the gas coolers 17 and 18. Connected. Connected to the gas coolers 17 and 18 are pipes 19 and 20 for returning condensed water to the gas-liquid separators 13 and 14 and pipes 21 and 22 for extracting gas from the water electrolysis apparatus. In order to avoid the concentration of impurities in pure water, a blow-down pipe 23 for discharging a part of pure water out of the system is connected to the inlet pipe 7 on the anode side. Although not shown, the electrolysis cell 1 is connected to a wiring lead for supplying electrolysis power.
[0008]
Next, the operation of the above apparatus will be described below. In the apparatus configured as shown in FIG. 2, when electric power is supplied from a wiring lead (not shown), water is electrolyzed in the electrolytic cell 1, and a mixed flow of pure water and generated gas is gasified via the pipes 11 and 12. It flows into the liquid separators 13 and 14. In the gas-liquid separators 13 and 14, the pure water and the generated gas are separated, and the pure water is returned again to the electrolysis cell 1 via the pipes 9 and 10 by the circulation pumps 5 and 6. The gas generated by electrolysis is separated by the gas-liquid separators 13 and 14 and then cooled by the coolers 17 and 18 to be separated into condensed water and gas. The condensed water is returned to the gas-liquid separators 13 and 14 via the pipes 19 and 20. The cooled gas is sent to the outside of the water electrolysis apparatus via the pipes 21 and 22.
[0009]
The pure water required for the electrolysis reaction is contaminated with electrolyte membranes and the like, and ion exchange resin cylinders, etc. are used to remove impurities in the water that cause the characteristics of the electrolysis cell to deteriorate (raise the electrolysis voltage). Is supplied to the anode side via the pure water device 2. In the electrolysis cell, in order to keep the electrolysis temperature constant (for example, 80 ° C.) and to quickly discharge the generated gas to the outside of the electrolysis cell, the amount of water is several tens of times the supply amount of pure water for electrolysis at both electrodes. It is circulating.
[0010]
Furthermore, with the operation, the amount of water several times the supply amount of pure water for electrolysis moves from the anode side to the cathode side through the electrolyte membrane. The reason is that water is entrained when ions pass through the electrolyte membrane. According to an example of the experimental results, about 7 to 9 times as much water moves from the anode side to the cathode side through the electrolyte membrane. To do. As a result, the amount of pure water on the cathode side increases, so that the amount of water on the cathode side is constant by discharging the amount of moving water out of the system or returning it to the anode side. It is necessary to adjust to. This adjustment of the amount of water is usually performed by monitoring a liquid level gauge installed in a gas-liquid separator or the like.
[0011]
In addition, the impurities cannot be completely removed from the pure water even through the pure water apparatus, and trace components remain. This impurity is captured by the electrolyte membrane when pure water passes through the electrode membrane, causing the electrolyte membrane to be contaminated and causing deterioration of the characteristics of the electrolytic cell. On the other hand, the pure water on the cathode side that has passed through the electrolyte membrane is cleaner than the pure water on the anode side, and the electrical resistivity is improved. This increasing ratio becomes remarkable when the quality of the pure water in the apparatus is lowered, and the electrical resistivity of the cathode-side pure water may be twice or more the anode-side electrical resistivity.
[0012]
[Problems to be solved by the invention]
By the way, the pure water for electrolysis supplied to the apparatus is discharged as generated gas or water vapor in the generated gas by electrolysis, but a small amount of impurities (alkali metal ions, etc.) are not accompanied by gas or water vapor. The water in the device is concentrated as the operation continues. When this concentration progresses, the characteristics of the electrolysis cell are deteriorated. Therefore, in the water electrolysis apparatus, an appropriate amount of water is discharged from the blow-down pipe 23 to suppress excessive concentration of impurities. However, it is impossible to make the impurity concentration completely zero, the water quality is lowered, and the electrical characteristics of the water electrolysis cell gradually decline, for example, the cell voltage rises during long-term operation. . .
[0013]
The present invention has been made in view of the above problems, and an object of the present invention is to improve the water electrolysis cell so that the water electrolysis cell can maintain predetermined electrical characteristics in a long-term continuous operation. It is to provide a water electrolysis apparatus capable of managing water quality and an operation method thereof.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, a water electrolysis cell whose interior is divided into an anode chamber and a cathode chamber by an electrolyte membrane such as a solid polymer, and the anode chamber and the cathode chamber are individually connected to each other. Each of the anode side (anode side) and cathode side (cathode side) pure water circulation circuit including the gas-liquid separator and an external pure water supply line for supplying pure water to the water electrolysis cell from the outside In the operation method of the water electrolysis apparatus, when the specific resistance value of the blowdown water from the gas-liquid separator on the anode side decreases , the discharge amount of the blowdown water is increased. Pure water is supplied to the gas-liquid separator to adjust the water quality on the anode side (invention of claim 1).
[0016]
As a method for measuring the water quality of blowdown water, in addition to the measurement of specific resistance, for example, there is a method of measuring the pH value and grasping the water quality of the blowdown water based on the correlation obtained in advance between the pH value and the cation concentration. However, the specific resistance value is more direct and simple.
[0017]
Further, as an apparatus for carrying out the operation method, the inventions of the following claims 2 to 3 are suitable. That is, a water electrolysis cell whose interior is divided into an anode chamber and a cathode chamber by an electrolyte membrane such as a solid polymer, and an anode side (anode) including a gas-liquid separator individually connected to the anode chamber and the cathode chamber. Side) and cathode side (cathode side), respectively, and a water electrolysis apparatus comprising an external pure water supply line for supplying pure water to the water electrolysis cell from the outside. Blow-down water from the gas-liquid separator on the anode side is introduced through a water level regulator for supplying pure water to the separator and a blow-down pipe connected to the gas-liquid separator on the anode side. A water storage tank, a pure water supply line that purifies the water in the water storage tank with a pure water device such as an ion exchange resin cylinder and introduces pure water to the water level regulator, and water provided on the blowdown pipe Specific resistance measuring instrument and this specific resistance measurement When the specific resistance value measured by the vessel decreases and reaches a predetermined value, the amount of discharged water of the blowdown water is increased, and along with this, pure water is supplied to the gas-liquid separator on the anode side. And a control device (invention of claim 2 ).
[0018]
According to the water electrolysis apparatus of the second aspect of the invention, water is discharged little by little from the gas-liquid separator on the anode side, the quality of the discharged water is managed, and the discharged water is purified and reused. be able to.
[0019]
3. The water electrolysis apparatus according to claim 2 , wherein the water level regulator for replenishing the anode-side gas-liquid separator with pure water includes a connection pipe communicating with the water in the cathode-side gas-liquid separator. (Invention of claim 3 ) According to this configuration, as described above, when about 7 to 9 times the amount of water moves from the anode side to the cathode side through the electrolyte membrane, the pure water increased on the cathode side is returned to the water level regulator. The amount of water on the cathode side can be adjusted to be constant. Since the returned water is purified in the electrolyte membrane, the entire system has a rational configuration.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIG. In the water electrolysis apparatus shown in FIG. 1, members having the same functions as those shown in FIG.
[0021]
1 is different from FIG. 2 in that it is connected to a water level regulator 30 for supplying pure water to the anode-side gas-liquid separator 13 and the anode-side gas-liquid separator 13. A water storage tank 32 for introducing blowdown water from the anode-side gas-liquid separator 13 through a provided blowdown pipe 38 and water in the water storage tank by a pure water device such as an ion exchange resin cylinder 34. The pure water supply line 37 for purifying and introducing pure water into the water level adjuster 30, the specific resistance measuring device 40 for water provided on the blowdown pipe 38, and the specific resistance measuring device 40 When the specific resistance value decreases and reaches a predetermined value, the controller 41 increases the discharge amount of the blow-down water and, along with this, supplies pure water to the gas-liquid separator on the anode side. It is a point to prepare.
[0022]
In FIG. 1, 41a and 41b indicate drainage control valves and pure water supply control valves, and 36 indicates a pure water supply pump. Reference numeral 39 denotes a connection pipe according to the invention of claim 4.
[0023]
According to the apparatus shown in FIG. 1, water is discharged little by little from the anode-side gas-liquid separator 13 through the blowdown pipe 38, and the quality of the discharged water is determined by the specific resistance measuring device 40 and the control device 41. The discharged water can be purified by the ion exchange resin cylinder 34 and returned to the water level adjuster 30 for reuse.
[0024]
【Example】
With the apparatus shown in FIG. 1, 10 m1 / min of water is discharged from the gas-liquid separator 13 on the anode side, and the specific resistance of the water is maintained at 1.5 MΩ · cm or more at 80 ° C. When the water level was lower than, the amount of water was increased to 45 m1 / min, and the water quality in the system was adjusted so that more water was supplied from the water level adjuster 30 to the cell and the gas-liquid separator.
[0025]
With this adjustment, the electrolysis characteristics of the water electrolysis cell 1 showed an initial cell voltage of 1.533 V at a current density of 1 A / cm ² at 80 ° C., normal pressure and an electrode area of 50 cm ² , and 1.68 V after 50 h. However, 1.65 V ± 0.02 V was maintained even after 500 hours from the start of the test.
[0026]
In the above apparatus, when water quality control is not performed, the electrolysis characteristics of the water electrolysis cell 1 are the initial cell voltage when the current density is 1 A / cm ² at 80 ° C., normal pressure, and electrode area 50 cm ² . 1.535V, increased to 1.69V after 50h, continued to increase gradually thereafter, and reached 1.770V 150h after the start of the test. From these results, it was possible to control the quality of the water discharged from the anode side and maintain the quality of the water in the system, thereby suppressing the cell voltage rise and obtaining stable performance for a long period of time.
[0027]
【The invention's effect】
As described above, according to the present invention, a water electrolysis cell whose interior is divided into an anode chamber and a cathode chamber by an electrolyte membrane such as a solid polymer, and a gas connected individually to the anode chamber and the cathode chamber, respectively. Water electrolysis comprising an individual pure water circulation circuit on the anode side (anode side) and the cathode side (cathode side) including a liquid separator, and an external pure water supply line for supplying pure water to the water electrolysis cell from the outside In the apparatus, the anode-side gas-liquid separation is performed via a water level regulator that supplies pure water to the anode-side gas-liquid separator and a blow-down pipe connected to the anode-side gas-liquid separator. A water storage tank for introducing blowdown water from the vessel, a pure water supply line for purifying the water in the water storage tank with a pure water device such as an ion exchange resin cylinder and introducing pure water to the water level regulator; Ratio of water provided on blowdown piping When the specific resistance value measured by the anti-measurement device and the specific resistance measurement device decreases and reaches a predetermined value, the discharge amount of the blow-down water is increased. It is assumed that the liquid separator is equipped with a control device that supplies pure water, and water is discharged little by little from the gas-liquid separator on the anode side, and the quality of the discharged water is managed by a specific resistance measuring device and a control device. Thus, while maintaining the electrical characteristics of the water electrolysis cell at a predetermined value, the discharged water can be purified by the ion exchange resin cylinder and returned to the water level regulator for reuse.
[Brief description of the drawings]
FIG. 1 is a system diagram of an embodiment of a water electrolysis apparatus according to the present invention. FIG. 2 is a system diagram showing an example of a conventional water electrolysis apparatus.
1: Electrolytic cell, 5: Anode-side circulation pump, 6: Cathode-side circulation pump, 7, 8: Electrolytic cell-containing piping, 11, 12: Electrolytic cell outlet piping, 13, 14: Gas-liquid separator, 17, 18 : Gas cooler, 30: Water level adjuster, 32: Water tank, 34: Ion exchange resin cylinder, 37: Pure water supply line, 38: Pipe for blowdown, 39: Connection pipe, 40: Resistivity measuring instrument, 41 :Control device.

Claims (3)

A water electrolysis cell whose interior is divided into an anode chamber and a cathode chamber by an electrolyte membrane such as a solid polymer, and an anode side (anode side) including a gas-liquid separator individually connected to the anode chamber and the cathode chamber And a method for operating a water electrolysis apparatus comprising an individual pure water circulation circuit on each of the cathode side (cathode side) and an external pure water supply line for supplying pure water to the water electrolysis cell from the outside.
When the specific resistance value of the blowdown water from the gas-liquid separator on the anode side decreases , the discharge amount of the blow-down water is increased, and accordingly, pure water is supplied to the gas-liquid separator on the anode side. A method for operating a water electrolysis apparatus, comprising replenishing and adjusting water quality on the anode side. A water electrolysis cell whose interior is divided into an anode chamber and a cathode chamber by an electrolyte membrane such as a solid polymer, and an anode side (anode side) including a gas-liquid separator individually connected to the anode chamber and the cathode chamber And a water electrolysis apparatus provided with an individual pure water circulation circuit on each of the cathode side (cathode side) and an external pure water supply line for supplying pure water to the water electrolysis cell from the outside,
A water level controller for supplying pure water to the anode-side gas-liquid separator, and a blow-down pipe connected to the anode-side gas-liquid separator from the anode-side gas-liquid separator. A water storage tank for introducing blowdown water, a pure water supply line for purifying water in the water storage tank by a pure water device such as an ion exchange resin cylinder and introducing pure water to the water level regulator, and for the blowdown When the specific resistance measuring device for water provided on the pipe and the specific resistance value measured by the specific resistance measuring device decrease and reach a predetermined value, the discharge amount of the blowdown water is increased. In addition, a water electrolysis apparatus comprising: a control device that supplies pure water to the gas-liquid separator on the anode side. 3. The water electrolysis apparatus according to claim 2 , wherein the water level regulator for replenishing the anode-side gas-liquid separator with pure water includes a connection pipe communicating with water in the cathode-side gas-liquid separator. .

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