JPH04371592A - Production of concentrated oxygen-containing gas - Google Patents

Abstract

PURPOSE:To stably and continuously obtain an optional concd. oxygen-contg. gas to be used in medical treatment or for accelerating combustion. CONSTITUTION:The almost 100% oxygen gas generated in the anode chamber of a water electrolytic cell is mixed with air and diluted to a specified concn. In this case, the mist in the electrolytic oxygen is removed by a filter. An air electrode is used as the anode and/or cathode to suppress the fruitless generation of oxygen, hence the cell voltage is lowered, and the cost is further reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a highly concentrated oxygen-containing gas used for medical purposes, combustion promotion, etc., using oxygen gas produced by water electrolysis.

0002

[Prior art and its problems] Oxygen in air is about 20%, and the rest is mostly nitrogen. It is sufficient to use air with this oxygen concentration as it is in ordinary combustion equipment, etc., but in combustion equipment such as medical use, discharge method ozone production, and combustion equipment that requires particularly high temperatures, air containing oxygen gas with a higher concentration than usual is used. It may be necessary to use a contained gas. For this purpose, we extract oxygen gas from an oxygen cylinder and oxygen gas obtained by vaporizing liquid oxygen and mix them with air to condense the air (or dilute the oxygen gas). Methods such as obtaining a concentrated oxygen-containing gas and increasing the oxygen concentration in the air using a gas separation membrane are known. ■The method of using oxygen cylinders has been used for a long time, especially in the medical field, but because the amount of gas in the cylinder is finite, it cannot be used completely continuously, and the cylinder must be replaced periodically. Furthermore, when oxygen-enriched air is required, the operation of mixing oxygen and air is relatively complicated, making it difficult to supply oxygen-containing gas at a constant concentration. Also■
The method of using liquid air is a special method that is only used in a few places, and there is a problem in that it is extremely difficult to store liquid oxygen.

Furthermore, the method (2) using a gas separation membrane is a recently developed method in which oxygen is concentrated by using a special separation membrane (filtration membrane), and air is passed through the separation membrane in several stages. This method gradually increases the oxygen concentration by contacting with
An oxygen-containing gas with a high oxygen concentration of 20% nitrogen or more can be supplied. Since this method filters gas by applying pressure, its development is progressing rapidly because it requires very little energy for separation. However, this method
It requires a large amount of expensive modular separation membranes, the module itself has to be a high-pressure container, and since multi-stage concentration is required, the equipment tends to be complicated and expensive, and as mentioned above, there is an upper limit on oxygen concentration. There is a drawback that there is. Therefore, although the above-mentioned device is preferably used for large-scale equipment in view of energy cost, there is a problem in that the device is too expensive and difficult to use for small-scale equipment such as medical equipment.

0004

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for producing a highly concentrated oxygen-containing gas containing a predetermined concentration of oxygen gas at a low cost using relatively simple operations. It can be applied to both commercial and small equipment.

[0005]

[Means for Solving the Problems] The method of the present invention is characterized in that an oxygen-containing gas of a predetermined concentration is produced by mixing and diluting oxygen gas generated in the anode chamber of a water electrolyzer with air. This is a method for producing a highly concentrated oxygen-containing gas.

The present invention will be explained in detail below. When water is electrolyzed, oxygen gas is generated in the anode chamber and hydrogen gas is generated in the cathode chamber. In the method of the present invention, an oxygen-containing gas having a desired oxygen concentration can be obtained by taking out the oxygen gas from the anode chamber and mixing it with air. A conventional electrolytic cell can be used as the water electrolytic cell. For example, for the cathode of the electrolytic cell, a thin nickel mesh is used as the core material or base material for current supply, and a mixture of fluororesin, graphite powder as a catalyst material, and platinum or silver powder is coated on this and sintered. Air electrodes can preferably be used. In order to clearly distinguish and form the hydrophobic layer and the catalyst-containing layer of the air electrode, a porous thin layer of fluororesin is formed on one side of the nickel mesh, and the above-mentioned catalyst is formed on the opposite side of the nickel mesh. A layer may be formed. In addition to this air electrode, ordinary cathode materials such as platinum electrodes and carbon electrodes may be used as the cathode, but by using an air cathode for depolarization, the cell voltage is lowered and energy consumption is reduced. This makes it possible to generate oxygen gas at a lower cost.

[0007] As the anode, an insoluble metal electrode such as platinum-plated titanium or titanium coated with iridium oxide or the like is used, and the cathode and anode are set in an electrolytic cell to perform water electrolysis. When using an air electrode as the cathode, there is no need to install a diaphragm because almost no hydrogen gas is generated from the cathode side, but when using an electrode other than the air electrode as the cathode, In particular, when obtaining a highly concentrated oxygen-containing gas, it is preferable to use a diaphragm to prevent nitrogen from being mixed in from the cathode side. The diaphragm is not particularly limited, but a filter cloth, a fluororesin membrane, or the like with low voltage loss may be selected. A solid electrolyte, which is an ion exchange membrane, may be used as the diaphragm. In this case, an electrode (anode and cathode) catalyst material may be directly formed on the surface of the ion exchange membrane, or a solid electrolyte containing platinum or iridium oxide may be formed on the surface of the ion exchange membrane. Electrodes (anode and cathode) A solid electrolyte electrode device is constructed by bringing a fine titanium or tantalum mesh formed with a catalyst material into contact with the ion exchange membrane.

When an air electrode is used as the cathode, it is desirable that the air supplied to the air electrode be filtered and carbon dioxide removed through lime milk before being supplied to the cathode chamber. The electrolytic solution may be prepared by dissolving an electrolyte that has high conductivity and does not self-decompose, and an alkaline electrolytic solution such as caustic soda, a neutral electrolytic solution such as Glauber's salt, and an acidic electrolytic solution such as sulfuric acid can be used. Since the electrolyte may come out of the system as a mist, which may be dangerous, the ion exchange membrane may be used as a solid electrolyte and the electrolysis may proceed while supplying deionized water. As the solid electrolyte, for example, a perfluorocarbon sulfonic acid type cation exchange membrane such as Nafion (trade name) can be used. The ion exchange membrane may be attached directly to the air electrode, but in order to suppress the cathode reaction and remove migrated water from the anode and trace amounts of nitrogen gas originating from the air electrode, the ion exchange membrane may be attached directly to the air electrode. It is also possible to provide a porous conductor layer with openings between the exchange membrane and the cathode, for example the air electrode. In order to form the conductive layer, an ion exchange material in which an elutable substance is kneaded is applied to the cathode side surface of the ion exchange membrane, sintered, and then the elutable substance is removed. good. The kneaded material includes calcium carbonate powder, and the calcium content in this kneaded material can be removed by treatment with sulfuric acid.

When water is electrolyzed using such a water electrolyzer, oxygen gas is generated from the anode side. Since the oxygen gas contains saturated water vapor and some mist, it is desirable to remove the mist with a filter and then mix it with air to produce a highly concentrated oxygen-containing gas. It is preferable to use a nonwoven fabric made of fluororesin fiber, etc., which can be almost completely removed. A normal mixer may be used to mix the oxygen gas and air; for example, if a very precise concentration is not required, a valve may be installed and the above-mentioned oxygen may be mixed from the valve into the mixer filled with air. Gas can be blown to achieve the concentration. If it is necessary to precisely set the concentration, the oxygen-containing gas may be produced by introducing weighed air and the oxygen gas into a mixer and mixing them.

[0010] In this method, electrolyzed oxygen gas, which is obtained with almost 100% purity excluding mist and saturated water vapor, is diluted with air (or air is concentrated with the electrolyzed oxygen gas) to obtain an oxygen-containing gas of a predetermined concentration. There is no upper limit to the oxygen concentration of the oxygen-containing gas obtained, and 1
Any concentration of oxygen-containing gas from less than 0.00% to about 20% or more can be obtained. Since the amount of oxygen obtained by the electrolytic reaction is approximately proportional to the amount of current applied, the amount of oxygen generated can be easily controlled by adjusting the amount of current applied, and the required amount of oxygen can be produced at any time as needed. It can be converted into an oxygen-containing gas by the method of the invention. In other words, a continuous and stable supply of oxygen can be achieved through a relatively simple operation called electrolytic treatment, so regardless of the size of the required amount, the required amount of oxygen-containing gas at the required concentration can be obtained easily and at low cost. It becomes possible to supply

[0011]

EXAMPLES Next, examples of producing oxygen-containing gas by the method of the present invention will be described, but these examples are not intended to limit the present invention. Example 1 An ion exchange membrane with length 10 cm, width 10 cm, and thickness 0.
Using Nafion (trade name) 117 with a diameter of 18 mm and an ion exchange capacity of 0.9 meq/g, one side of the ion exchange membrane was plated with platinum, and a catalyst containing iridium oxide and ruthenium oxide was bonded by hot pressing. It was used as an anode. In addition, an air electrode was used as a cathode by coating a fluororesin on one side of a nickel mesh that also served as a cathode power supply element, and coating a mixture of graphite powder with a particle size of 1 to 5 μm and platinum powder with a particle size of 2 to 10 μm on the other side and sintering it. A solid electrolyte electrode device is configured in contact with the other surface of the ion exchange membrane, and electrolytic cells are partitioned by the solid electrolyte, each having a volume of 10
It was divided into an anode chamber and a cathode chamber of 0 cm3 and 200 cm3. An anode power supply element, which was a meshed titanium fine fiber sintered body, was connected to the anode material. While supplying deionized water to this electrolytic cell from the anode chamber side,
When current A was applied, a mixed gas of 95% by weight of oxygen gas, 4% by weight of water vapor, and mist was released from the anode chamber at 30g/
Obtained at the rate of time. This mixed gas is used as it is, with a fiber diameter of 0.
．． When the mixed gas (oxygen-containing gas) was passed through a filter made of a nonwoven fabric of fluororesin fibers of 1 to 1 μm, the composition was 98% by weight of oxygen gas and 2% by weight of water vapor.
And the mist changed to 0% by weight. When this oxygen-containing gas that had passed through the filter was blown into a container with a capacity of 200 liters filled with air (30 g/hour, the same as the generation rate of the mixed gas), the filled air was replaced with the oxygen-containing gas. An oxygen-containing gas having a concentration of 50% by weight was obtained.

Example 2 Water electrolysis was carried out using the apparatus of Example 1 under the same conditions as Example 1 except that the current value was changed to 50A. A mixed gas of 4% by weight and 1% by weight of mist was obtained at a rate of 15 g/h. When this mixed gas was directly passed through the same filter as in Example 1, the composition of the mixed gas (oxygen-containing gas) was 98% by weight of oxygen gas, 2% by weight of water vapor, and 0 mist.
% by weight. When this oxygen-containing gas that had passed through the filter was blown into the same container as in Example 1 (at the same rate of generation of the mixed gas, 15 g/hour), the filled air was replaced with the oxygen-containing gas, resulting in a concentration of 35 wt. % oxygen-containing gas was obtained.

Example 3 When the mixed gas generated by electrolysis was directly blown into the container of Example 1 at the same speed as in Example 1 without passing through a filter, the composition of the oxygen-containing gas obtained was 33.
% by weight, 1.5% by weight of water vapor and 0.5% by weight of mist. Example 4 The solid electrolyte was constructed in the same manner as in Example 1 except that the solid electrolyte was constructed by attaching platinum powder as a cathode material to an ion exchange membrane instead of the air electrode of Example 1 as a cathode. When the containing gas was produced, the composition of the obtained gas was 97% by weight of oxygen gas and 3% by weight of water vapor.
Met. The cell voltage during electrolysis increased from 1.6 V in Example 1 to 2.4 V.

[0014]

Effects of the Invention The present invention provides a highly concentrated oxygen-containing gas characterized by producing an oxygen-containing gas of a predetermined concentration by mixing and diluting oxygen gas generated in the anode chamber of a water electrolyzer with air. This is a manufacturing method. According to the method of the present invention, the electrolyzed oxygen gas obtained with almost 100% purity (or concentration) is diluted with air to produce an oxygen-containing gas.
Any concentration of oxygen-containing gas below 0.00% can be obtained. Since the amount of oxygen gas generated by water electrolysis is proportional to the amount of current applied and is generated continuously, it is possible to ensure a stable supply of oxygen and, therefore, stable generation of oxygen-containing gas.

The cost of oxygen gas obtained by electrolytic reaction is lower than that of other oxygen gases such as oxygen gas filled in oxygen cylinders, and therefore oxygen at the required concentration can be obtained through a relatively simple operation called electrolytic treatment. It becomes possible to supply the required amount of contained gas at low cost. By removing the mist contained in the oxygen gas generated by electrolysis with a filter, it is also possible to reduce the amount of mist in the resulting oxygen-containing gas and further improve the purity. Furthermore, if an air electrode is used as at least one of the anode and cathode of the electrolytic cell, the cell voltage can be lowered, and further cost reductions can be achieved.

Claims (4)

[Claims] 1. A method for producing a highly concentrated oxygen-containing gas, which comprises producing an oxygen-containing gas at a predetermined concentration by mixing and diluting oxygen gas generated in an anode chamber of a water electrolyzer with air. 2. The method according to claim 1, wherein after the mist in the oxygen gas generated in the anode chamber is removed by a filter, the oxygen gas is mixed with air. 3. The method according to claim 1, wherein a solid electrolyte electrode device having electrodes on both sides of an ion exchange membrane is used as the water electrolyzer. 4. The method according to claim 1, wherein an air electrode is used as anode and/or cathode.