JPS595673B2 - electrochemical oxygen pump device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochemical oxygen pump device, which has a function of removing only oxygen gas from the atmosphere.

Therefore, the device of the present invention, when the atmosphere is air,
It is used as an air oxygen removal device or a nitrogen-based gas supply device. One of the purposes of an electrochemical oxygen pump device that functions as an oxygen removal device is to maintain food quality.

For example, devices for removing oxygen from the air are useful in preventing the growth of oxygen-loving bacteria that cause discoloration and odor of rice in rice cookers. Furthermore, in refrigerators and freezers, it is necessary to remove oxygen from the atmosphere in order to prevent oxidation reactions and maintain the freshness of vegetables, etc., and this requires an electrochemical device that functions as an oxygen removal device or a nitrogen-based gas supply device. Oxygen pump equipment is utilized. An electrochemical oxygen pump device that functions as a nitrogen-based gas supply device is used as a gas supply source to an atmospheric furnace or the like that requires a neutral gas atmosphere.

Conventionally, as an electrochemical oxygen pump device, CaO and Y
A device is being considered in which porous platinum electrodes are provided on both sides of an oxygen ion conductive solid electrolyte made of ZrO2 stabilized with 2O3, and a DC electric field is applied to pump oxygen from the cathode side to the anode side. .

However, the operating temperature of these oxygen ion conductors is 500°C.
The temperature is as high as ~1000°C, and thermal energy is required to constantly maintain this temperature, which is undesirable from the viewpoint of energy saving. In this regard, the electrochemical oxygen pump device of the present invention is characterized in that it uses a solution electrolyte that has oxygen ion conductivity or ion group conductivity containing oxygen atoms at a temperature near room temperature, so it can be used at room temperature. , it is becoming more energy efficient. On the other hand, to maintain the quality of food, oxygen scavengers such as iron carbide, iron oxide, and metals have been commercially available.

However, all of these oxygen scavengers remove oxygen through a chemical reaction with oxygen in the air, and have the disadvantage that they cannot be easily recycled and are disposable. Therefore, it is necessary to constantly replenish and replace new oxygen scavengers, which is extremely inconvenient for the user. Furthermore, the need for food quality preservation technology is increasing as the direct addition of antioxidants to food (food additives) is being reconsidered due to its effects on the human body. The electrochemical oxygen pump device that functions as the oxygen removal device of the present invention is not disposable and can withstand long-term use. Furthermore, as a method for separating oxygen and nitrogen from air, there has been an air cryogenic separation method for a long time, and these are commercially available as oxygen cylinders and nitrogen cylinders.

However, these systems are inconvenient due to the ordering and delivery distribution system, and have the disadvantage of lacking urgency. The electrochemical oxygen pump device that functions as the nitrogen supply device of the present invention has the advantage that it can be easily miniaturized and both manufacturing cost and running cost can be reduced. The basic structure of the electrochemical oxygen pump device of the present invention is as shown in FIG.
and positive electrodes 4 are arranged facing each other, and the negative electrodes 3 are installed so that there is a part in contact with the solution electrolyte 2 and also in contact with the gas 6, so that both electrodes 3 and 4 do not have a negative potential component. It is connected to an external power source 5 that supplies current, for example, direct current, and is provided with a gas reservoir 7 that stores gas 6 as a means for isolating the gas 6 in contact with the negative electrode 3 and the oxygen 8 generated on the positive electrode 4 side. It is characterized by

An electrochemical oxygen pump device can only function as an oxygen removal device or a nitrogen supply device if it is equipped with this gas reservoir 7. Note that, for convenience of the experiment, the gas reservoir 7 is equipped with at least one gas plug 8.

Furthermore, for the convenience of the experiment, a sheath 9 is provided to electrically insulate the lead wire connecting the negative electrode 3 and the external power source 5, but this lead wire does not necessarily need to pass through the solution electrolyte 2, and the gas reservoir The electrically insulating coating 9 is not necessarily required since the electrically insulating coating 9 may be penetrated through the wall of the electrically insulating coating 9 (however, sealing treatment is required to maintain airtightness). The material of container 1 is plastic.
Any electrically poor conductor such as glass or ceramic may be used.

A plastic container was used in the example. (1) Open the gas valve 8 and introduce 1 atmosphere of air 6 into the gas reservoir 7, and then close the gas valve 8.

(2) Using a 1V constant voltage DC power supply as the external power supply 5,
The positive terminal is connected to the positive electrode 4 (nickel conductive plate), and the negative terminal is connected to the negative electrode 3 (carbon electrode).

(3) At this time, on the cathode side, 3 of oxygen, water, and carbon
02+2H20+4e→40 at the phase boundary where the phases meet
A reaction called H- occurs, and only oxygen among the components of the air 6 is consumed, and hydroxyl ions 0H- are generated.

(4) The generated hydroxide ions 0H7 migrate and diffuse in the direction of the positive electrode according to the potential gradient in the electrolytic solution 2.

(5) The hydroxyl ion 0H- that arrived at the positive electrode surface is 40H
The reaction -→02+2H20+4e generates oxygen and water while giving electrons to the positive electrode.

(6) Oxygen generated on the surface of the positive electrode becomes bubbles, moves upward in the electrolytic solution 2, and is released into the atmosphere.

(7) The water generated in the process of (5) above diffuses in the electrolyte 2 due to the concentration gradient, returns to the negative electrode side, and returns to the above ((5)).
It is used in the cathode reaction of 02+2H20+4e→40H- shown in step 3). (8) When a certain period of time passes, that is, when the oxygen that is a component of the air 6 in the gas reservoir 7 is consumed and completely disappears, the current supplied from the external power supply 5 automatically stops flowing, and the Oxygen bubbles stop forming on the electrode surface.

This is because the oxygen necessary for the cathode reaction shown in the process (3) above was consumed and completely disappeared, so that the cathode reaction stopped completely. (9) Despite applying 1V DC, almost no current flows and after the generation of oxygen bubbles on the surface of the positive electrode has stopped,
Gas analysis of the gas 6 remaining in the gas reservoir 7 revealed that the main component of the gas 6 was N2 gas, and the presence of H2 gas was not recognized within the detection sensitivity range.

As a result of the above processes (1) to (9), all the oxygen gas components present in the gas reservoir 7 on the negative electrode side moved to the positive electrode side and were released into the atmosphere.

All that is required for the movement of this oxygen gas component, ie, the oxygen pump, is electrical energy supplied by an external power source.
Faraday's law, published in 1883, basically holds true between the amount of oxygen transferred and the electrical energy supplied. That is, 1 mole of oxygen (22.4
The theoretical amount of electricity required to move 1) is 4XF (Faraday), or 107.2 Ah. In reality, there is leakage current (used for resistance heating of the electrolyte, etc.), and a larger amount of electricity is required than this theoretical amount of electricity. (
Theoretical amount of electricity) x 100/(actual amount of electricity) as current efficiency (%
), but in the example with the above basic configuration, it was 90% or more. In order to increase the oxygen pumping capacity per unit time, that is, the amount of movement per unit time, the current capacity per unit time may be increased.

As already mentioned, there are measures to increase this current capacity, such as making the electrode itself porous. Further, in order to increase the electrode area, it is necessary to provide a plurality of negative electrodes or positive electrodes. For example, in the basic configuration of the oxygen pump device described above, an electrode arrangement as shown in FIG. 2 is useful. It is also useful to make the structure of the electrode itself not only plate-like but also columnar or cylindrical. In particular, in the case of a negative electrode, a structure in which the central part of a cylinder is hollowed out as shown in 33 in Figure 3, that is, a container-like structure in which the upper part of the electrode is open, increases the oxygen adsorption capacity and, in turn, increases the current capacity per unit time. It has the effect of increasing the amount of oxygen, and is useful as a cathode for the electrochemical oxygen pump device of the present invention. Next, as a device for improving the current efficiency of the electrochemical oxygen pump device of the present invention, a method of arranging a plurality of negative electrodes and a plurality of positive electrodes alternately facing each other as shown in FIG. There is.

In this alternating arrangement of electric kettles, it is possible to shorten the distance between a pair of opposing negative and positive electrodes, which means that the electrical resistance between both electrodes can be reduced, thereby increasing the current efficiency of this device. can do. In order to improve current efficiency, it is extremely useful to shorten the distance that oxygen ions or anion groups containing oxygen atoms migrate and diffuse through the solution electrolyte. Oxygen gas or oxygen bubbles generated on the surface also reach the negative electrode side. Again, cathode reaction 02+2H20+
It is important to devise ways to avoid participation in 4e→40H-. In order to prevent oxygen bubbles generated on the surface of the positive electrode from returning to the surface of the negative electrode, a solution electrolyte component and oxygen ions and ion groups containing oxygen atoms must pass between the opposing negative and positive electrodes. It is useful to install a partition wall that makes it difficult for oxygen bubbles generated on the positive electrode side to pass through. Examples of partition walls having such properties include cloth-like partition walls made of asbestos, glass wool, or the like. Next, FIG. 5 shows the configuration of an electrochemical oxygen pump device that functions as an oxygen removal device or a nitrogen-based gas supply device. In this device, a negative electrode 103 and a positive electrode 104 are arranged facing each other in a solution electrolyte 102 housed in a container 101, and there is a portion where the negative electrode 103 contacts the solution electrolyte 102 and also contacts a gas 106. An external power source 105 that supplies current without a negative potential component is connected to both electrodes 103 and 104, and a gas reservoir 107 that stores gas 106 in contact with the negative electrode 3 is provided. Note that in this example, the gas stopper 108 of the gas reservoir 106
, an inlet/outlet 110 and an oxygen bubble-impermeable isolation, for example a cloth-like partition 111 made of glass wool. Here, in the configuration of the gas reservoir on the cathode side of this device, a part of the wall of the gas reservoir has an open structure, and the open end is connected to the surface of the cathode 103 as shown at 112 in FIG. The close contact part 112 is the solution electrolyte 10.
It is characterized by being installed so that it is immersed in water.
Alternatively, a portion of the wall of the gas reservoir has an open structure at multiple locations, and the open ends at the multiple locations are brought into close contact with the surfaces of multiple cathodes 3 as shown in FIG. It may be installed so that the close contact portion of the electrolyte 2 is immersed in the solution electrolyte 2. Alternatively, a part of the wall of the gas reservoir has an open structure, and the open structure is immersed in the solution electrolyte 2 so as to enclose the negative electrodes 3, respectively, as shown in FIG. 1 or 3, for example. It may be installed so that The materials of the container 101, solution electrolyte 102, negative electrode 103, and positive electrode 104 used in the embodiment shown in FIG. 5 are all the same as those used in the embodiment shown in FIG. Further, as the external power supply 105 in FIG. 5, a 1V constant voltage DC power supply was used. Next, the operating principle and effects will be described based on the electrochemical oxygen pump device shown in FIG.

(1) Open the gas valve 108 and let air 10 in the gas reservoir 107.
After introducing 1 atm of gas 6, the gas valve 108 is closed.

(2) Connect the positive terminal of the external power supply 105 to the positive electrode 104,
The negative terminals are connected to the negative electrodes 103, respectively.

(3) At this time, the negative electrode 103 consumes only oxygen in the air 106 and is transported toward the positive electrode 104 in the form of OH- ions generated by the negative electrode reaction.

(4) Oxygen is precipitated on the surface of the positive electrode 104 by a positive electrode reaction.

This oxygen becomes bubbles and moves upward in the solution electrolyte 102 and is released into the atmosphere. (5) After a certain period of time has passed, the oxygen in the gas reservoir 107 is completely consumed, and the current supplied from the external power supply automatically stops flowing, and the generation of oxygen bubbles on the surface of the positive electrode stops.

(6) At this time, the inside of the gas reservoir 107 is in a reduced pressure state of approximately 4/5 atmosphere, so open the gas valve 108 again, introduce new air by approximately 1/5 atmosphere, and then open the gas valve 108 again.
Close again.

(7) When the oxygen gas component mixes into the gas reservoir 107 in this way, the current supplied from the external power source automatically starts flowing again.

(8) Furthermore, after a certain period of time has passed, the gas reservoir 107
Once the oxygen inside is completely consumed, the current will automatically stop again.

(9) At this time, nitrogen-based gas having a pressure of approximately 1 atmosphere is stored in the gas reservoir 107.

As a result of gas analysis, the main component of gas 106 is N2, and H
2 gas and 02 gas are not recognized within the detection sensitivity range. All of the oxygen gas components introduced into the gas reservoir 107 on the cathode side as described above are released into the atmosphere.

The current efficiency at this time was 95% or more. This gas reservoir 1
The nitrogen-based gas obtained in step 07 can be used as a nitrogen-based gas supply source.

In order to take out the nitrogen-based gas in the gas reservoir 107 to the outside through the inlet/outlet 112, it is useful that the gas reservoir that stores the gas in contact with the cathode is equipped with a gas pressure regulator. For example, a gas pressure regulator attached to a certain part of the wall of the gas reservoir 107 can control the inside of the gas reservoir from 1.1 to
While maintaining the pressure at 1.5 atmospheres, the nitrogen main component gas is introduced into the inlet/outlet port 112.
sent to the outside through On the other hand, after connecting the inlet/outlet 110 of the gas reservoir 107 to the inside of a food storage, such as a rice cooker container or a refrigerator, and opening the gas valve 108,
When the operation of the above embodiment is carried out, the oxygen gas component in the food storage can be completely removed.

That is, it can be used as an oxygen gas removal device. Next, the structure of the gas reservoir on the cathode side of an electrochemical oxygen pump device that can continuously remove oxygen from the air or continuously supply nitrogen-based gas will be described. As shown in FIG. 6, the gas reservoir 107 has at least two gas plugs: a gas plug 116 on the air inlet 115 side and a gas plug 118 on the nitrogen-based gas outlet 117 side. It is characterized by having a gas-impermeable partition wall 120 that separates the air 106 provided in the gas reservoir from the nitrogen-based gas 119.

Further, the close contact portion 112 between the open end of the wall of the gas reservoir and the negative electrode 103 is installed so as to be immersed in the electrolyte solution, as in the embodiment shown in FIG. When functioning as an oxygen removal device, one end of the gas-impermeable partition wall 120 does not necessarily have to be brought into close contact with the negative electrode 103 as shown in FIG. 6.

The air inlet 115 and the nitrogen-based gas outlet 117 are connected to the inside of a food storage, for example, and the gas valves 116, 118 are connected to each other.
With the door open, use a fan to blow the atmosphere inside the refrigerator, and create air reservoir 1.
Gas is continuously circulated from 07 to the nitrogen main component gas reservoir 119 and further into the refrigerator. During this circulation process, only oxygen components in the air are adsorbed by the cathode and released into the atmosphere by the oxygen pump action. Therefore, the concentration of oxygen gas components in the food storage will gradually decrease and eventually disappear completely. Next, in order to function as a nitrogen-based gas supply device, it is preferable that one end of the gas-impermeable partition wall 120 is brought into close contact with the cathode 103.

In this case, atmospheric air is sent into the air reservoir 107 through the inlet 115 using a fan or a normal pump.
While the air 106 thus sent passes through the interior or surface of the cathode, only the oxygen component therein is adsorbed by the cathode and released into the atmosphere. On the other hand, components such as nitrogen in the air 106 pass through the inside of the negative electrode and exit into the nitrogen-based gas reservoir. This Q nitrogen main component gas 119 is at the gas outlet 1.
18, and serves as a nitrogen-based gas supply source. In this case, air is transferred from the air reservoir 106 to the nitrogen-based gas reservoir 119.
It is important to devise a way to completely adsorb and remove oxygen components while the air moves to the negative electrode, that is, while the air passes through the inside of the cathode. This technique is also useful in improving the operating efficiency of the oxygen removal device. For example, as already described in the basic structure of the present invention, the cathode is made into a porous structure and a catalyst or the like is added to increase the oxygen adsorption capacity. The structure of an electrochemical oxygen pump device which functions as a device for removing oxygen from air is the basic structure of the device of the present invention shown in FIGS. 1 to 4 described above. That is, it is a device equipped with a gas reservoir that stores gas in contact with the negative electrode.
A gas reservoir for storing gas in contact with the cathode is provided with at least one gas plug or at least one gas plug and a pressure regulator. Here, if the gas reservoir on the cathode side shown in FIG. 6 is used, oxygen gas can be continuously removed from the air according to the operating principle already described.

The device of the present invention, which functions as an oxygen removal device, can be designed to be portable and can be used to remove oxygen from the air in food storage or polyethylene food storage bags.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the basic configuration of the electrochemical oxygen pump device of the present invention, FIGS. 2, 3, and 4 are longitudinal sectional views showing modifications thereof, and FIG. 5 is an oxygen removal device. Alternatively, a vertical cross-sectional view showing the configuration of an electrochemical oxygen pump device functioning as a nitrogen-based gas supply device, and FIG. 6 is a vertical cross-sectional view showing a modification of the cathode side thereof. 1,101... Container, 2,102...
Solution electrolyte, 3, 33, 103... cathode, 4
, 104... positive electrode, 5, 105...
External power supply, 7,107... Gas reservoir, 8,108
, 116, 118... gas valve, 120...
...Gas-impermeable bulkhead.

Claims (1)

[Claims] 1. A negative electrode and a positive electrode are arranged facing each other in a solution electrolyte housed in a container, so that there is a portion where the negative electrode contacts the solution electrolyte and also contacts gas. and is connected to an external power source that supplies a current having no negative potential component to both electrodes, and includes gas isolation means for separating the gas in contact with the negative electrode from the oxygen generated on the positive electrode side. An electrochemical oxygen pump device, wherein the gas isolation means is a gas reservoir that stores gas in contact with the cathode. 2. The electrochemical oxygen pump device according to claim 1, wherein the solution electrolyte has conductivity of oxygen ions or ion groups containing oxygen atoms at a temperature near room temperature. 3. The electrochemical oxygen pump device according to claim 2, wherein the solution electrolyte is an aqueous solution of alkali hydroxide. 4. The electrochemical oxygen pump device according to claim 1, wherein at least one of the negative electrode and the positive electrode is composed of a plurality of electrodes. 5. The electrochemical oxygen pump device according to claim 4, wherein a plurality of negative electrodes and a plurality of positive electrodes are alternately arranged to face each other. 6 A partition wall is installed between the opposing negative electrode and positive electrode, which allows solution electrolyte components and oxygen ions or ion groups containing oxygen atoms to pass through, but makes it difficult for oxygen bubbles generated on the positive electrode side to pass through. An electrochemical oxygen pump device according to claim 1 or 4. 7. The electrochemical oxygen pump device according to claim 1, wherein the positive electrode and the negative electrode are made of a material that does not generate hydrogen when dissolved in a solution electrolyte. 8. The electrochemical oxygen pump device according to claim 1 or 7, wherein the negative electrode has a water-repellent film on its surface. 9. The electrochemical oxygen pump device according to claim 1, wherein the external power source is a power source that supplies any one of direct current, half-wave rectification, or pulsating current that does not have a negative potential component. 10. The electrochemical oxygen pump device according to claim 1 or 9, wherein the external power source is a power source that supplies a voltage lower than the minimum voltage required to cause electrolysis of water. 11 A gas reservoir that stores gas in contact with the cathode is equipped with at least one gas plug, and a portion of the wall of the gas reservoir has an open structure, and the open end is connected to the surface of the cathode. 2. The electrochemical oxygen pump device according to claim 1, wherein the electrochemical oxygen pump device is installed in such a way that the close contact portion is immersed in a solution electrolyte. 12 A gas reservoir for storing gas in contact with the negative electrode is equipped with at least one gas plug and a gas pressure regulator, and a portion of the wall of the gas reservoir has an open structure, and the open end thereof is 2. The electrochemical oxygen pump device according to claim 1, wherein the electrochemical oxygen pump device is installed so as to enclose a negative electrode and be immersed in a solution electrolyte. 13. The electrochemical oxygen pump device according to claim 1, wherein the cathode has a container-like structure with an open top. 14 A gas reservoir for storing gas in contact with the cathode is equipped with a gas plug for introducing gas and a gas plug for supplying nitrogen-based gas, and the introduced gas provided in the gas reservoir and the nitrogen-based gas can be connected to each other. 7. The electrochemical oxygen pump device according to claim 6, further comprising a gas-impermeable partition separating the oxygen from the oxygen.