JPS5815548B2 - Device for separating oxygen from a mixed gas containing oxygen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for separating only oxygen from a mixed gas containing oxygen, such as air, and its purpose is to improve the concentration of an electrolyte in an electrolytic cell constituting the device. The purpose is to prevent the electrolytic cell from being excessively diluted, and to simplify the supply of water to the water replenishment tank for replenishing the electrolytic cell.

A so-called gas diffusion electrode known in the field of fuel cells is used as a cathode, and an oxygen generating electrode made of a nickel plate or the like is used as an anode.
When a DC voltage is applied between the negative and positive electrodes while supplying air to the gas diffusion electrode of an electrolytic cell using an aqueous solution of caustic potash as an electrolyte, a cathode reaction occurs: 02+ 2 H2O+4 e
-)40H-” (1) Anodic reaction; 40H=02
By the reaction ↑+2 H2O+4 e -(2),
Only oxygen in the air is selectively consumed at the cathode, and oxygen is generated at the anode.

In other words, only oxygen is separated from the air and transferred from the cathode side to the anode side.

Such a device thus functions as a device for electrochemically separating oxygen from air.

When the target object is oxygen generated from the anode, the power generator becomes an oxygen generator.

In addition, a certain chamber or container and the gas chamber of the gas diffusion electrode of the electrolytic cell mentioned above are connected with a pipe in an airtight manner to circulate air and release oxygen generated from the anode of the electrolytic cell to the outside of the system. For example, the oxygen in the chamber or container is removed, so that the device functions as an oxygen scavenger.

Such an apparatus for electrochemically separating oxygen from air has already been described in detail in Japanese Patent Publication No. 43-25001 or Japanese Patent Application Laid-open No. 44-259-1983.

When operating a power-reducing device, that is, when a DC voltage is applied between the negative and positive electrodes, Joule heat is generated due to overvoltage of each electrode and resistance loss of the electrolyte, and the temperature of the electrolyte generally rises considerably above room temperature. , moisture in the electrolyte dissipates through the outlet of oxygen generated at the anode or through the pores of the porous gas diffusion electrode, causing the electrolyte level to drop.

Therefore, generally a refill tank for replenishing water is prepared separately, and the electrolytic cell and the refill tank are connected with a pipe.
It is necessary to take measures to automatically replenish water from the replenishment tank to the electrolytic cell side as the liquid level in the electrolytic cell drops.

Generally, in order to suppress resistance loss in the electrolyte portion of the electrolytic cell, the distance between the negative and positive electrodes is very short, about 5 mm.

Therefore, since the bottom area of the electrolytic cell is small, evaporation of a small amount of water causes a significant drop in the electrolyte level.

On the other hand, when a water replenishment tank is prepared separately, the bottom area of the water replenishment tank is not subject to the same restrictions as the electrolytic cell, and therefore can be made 10 times or more the bottom area of the electrolytic cell.

Therefore, even if water is replenished from the refilling tank to account for the drop in the electrolyte level in the electrolytic cell, the drop in the water level in the refilling tank will be less than 1/10, and water will not be replenished into the refilling tank for a very long time. You don't have to.

Such an automatic water replenishment system consists of installing a pipe in the refill tank that communicates with the atmosphere, and defining the liquid level in the electrolytic cell at the tip of the pipe, so that when the liquid level drops, the water in the refill tank will drain. There are those in which air flows into the electrolytic cell side and at the same time air flows in from the end of the pipe to fill the space created to reduce the amount of water, and there are also so-called six chicken water cups in which the water container is turned upside down. However, in either case, the refill tank or container must be sufficiently airtight.

Although conventional airtight tanks were airtight, they had the following drawbacks.

One of these is that when attempting to supply water to the refill tank, it is necessary to close the pipe connecting the refill tank and the electrolytic cell with a cock or valve, and then remove the lid of the refill tank.

In other words, if you remove the lid without closing the pipe, the airtightness will be broken and the water in the refill tank will flow into the electrolytic cell all at once.

Second, the air filling the space above the refill tank expands or contracts as the environmental temperature changes, so when it expands, water is pushed out of the refill tank toward the electrolytic cell.
On the other hand, when it contracts, the electrolytic solution is sucked into the water replenishment tank, so the electrolytic solution in the electrolytic cell is gradually diluted, and eventually the electrolytic cell can no longer exhibit its desired performance.

The present invention seeks to eliminate the curling disadvantage.

That is, the present invention aims to overcome the drawbacks that conventional water replenishment tanks inevitably have because they are airtight by making them open-type.

Of course, in order to make it an open type, 1. A certain amount of ingenuity is required, which will be explained in detail below with reference to the drawings.

FIG. 1 shows a schematic cross-sectional structure of an electrochemical deoxidizer according to an embodiment of the present invention.

In Figure 1, the electrochemical deoxidizer is mainly used in electrolytic cell 1.
and a water refilling device 2.

The electrolytic cell 1 includes an anode 31 consisting of a gas diffusion electrode, an anode 41 consisting of an oxygen generating electrode made of porous nickel. It is composed of an electrolytic solution 5 made of a caustic potash aqueous solution, a battery case 6 made of ABS resin, a gas chamber 7, and an oxygen outlet 8.

The chamber to be deoxidized (not shown) is connected to the air supply 9 and the air outlet 110, and the air in the chamber to be deoxidized is supplied from the air inlet to the waste chamber 7 by the circulation pump 11, and from the air outlet to the waste chamber 7. 10, it is returned to the chamber to be deoxidized.

When a DC voltage is applied between the cathode 3 and the anode 4 while air is being circulated in this manner, only oxygen is consumed at the cathode 3 and oxygen is generated at the anode 4.

Oxygen generated at the anode 4 passes through the electrolytic solution 5 and is discharged out of the system from the oxygen outlet 8.

Oxygen in the chamber to be deoxidized is thus selectively removed.

On the other hand, the water refilling device 2 includes a water supply tank 12 made of acrylic resin and a pipe 1 connecting the water supply tank 12 and the electrolytic cell 1.
6 and water 17, and the water replenishment tank 12 is open to the atmosphere as shown by the air flow port 14.

Therefore, it goes without saying that the water 17 will flow into the electrolytic cell 1 all at once if no measures are taken on the water replenishment tank side.

If you take some measures to prevent this water from flowing in more than necessary, the refill tank 12 is open to the atmosphere, so when the water 17 decreases and water is supplied, the pipe 16
There is no need to close it, just remove the cap 15,
In addition to being able to supply water, the space 18 is always maintained at atmospheric pressure, so it will not expand or contract due to changes in environmental temperature, and the electrolyte 5 will not be excessively diluted.

The key point of the present invention is how to prevent the water 17 under atmospheric pressure from flowing into the electrolytic cell 1 more than necessary.

The invention consists of two elements.

The first is to prevent the electrolyte and water from mixing, and the second is to allow the concentration of the electrolyte within a certain range.

Let's start with the first element.

The refill tank 1 is arranged so that the liquid pressure of the electrolyte 5 in the electrolytic cell 1 and the water pressure of water 1γ in the refill tank 12 are always balanced through the pipe 16.
In other words, if the water surface height is set at position 2, that is, water 1γ, water 17 will not flow excessively into electrolytic solution 1.

1, the liquid level height of the electrolyte 5 is h, the specific gravity of the electrolyte is ρ,
If the water surface height of water 17 is 1, then the specific gravity of water is 1, so ρh=h・・・・・・・・・・・・・・・・・・・・・
・・・・・・(3) The position of the refilling tank is determined so that the following relationship is always satisfied. 3. If you do this,
When the liquid level decreases due to the dissipation of water in the electrolytic solution, that is, h decreases (at this time, the specific gravity ρ increases slightly), the balance between the liquid pressure and the water pressure is maintained (until the two are balanced from the water replenishment tank 12). Water 11 is transferred to the electrolytic cell side and a water replenishment operation is performed.

Next, the second element will be explained.

FIG. 2 shows the current-voltage characteristics of the electrolytic cell 1 in the atmosphere when the concentration of the caustic potash electrolyte was changed from 2N to 12N.

A is 2N-KOH, B is 4N-KOH, C is 5.7N-
KOH, D is the characteristic in 10N-KOH, and E is the characteristic in 12N-KOH.

From FIG. 2, it can be seen that there is almost no difference in the characteristics when the electrolyte concentration is in the range of 4N to 10N, preferably 5N to 7N.In other words, the concentration of the electrolyte 5 is within a certain range. It turns out that it can vary.

As described above, the present invention combines the above two elements.

That is, if the specific gravity of the electrolytic solution 5 at the upper limit concentration is ρa, and the liquid level height is ρa, then in order to balance these, the water surface height la of the water 17 is as follows.

1a=ρaha・・・・・・・・・・・・・・・・・・
・・・・・・・・・(4) On the other hand, if the specific gravity at the lower limit concentration of the electrolyte is ρb and the liquid level height is hb, the water surface height 1b of the water 17 to balance this is as follows. become.

lb-ρbhb・・・・・・・・・・・・・・・
・・・・・・・・・(5) Therefore, the water surface height 1 of the refilling tank is aha≦1≦ρb hb・・・・・・・・・・・・・・・
...If the size and position of the water replenishment tank are determined in advance to satisfy (6), water will be refilled immediately even if the liquid level drops, and changes in the electrolyte concentration will be kept within the allowable range. It turns out.

Next, in order to confirm the effect of the present invention, the electrode action area was
dm'' electrolytic cells were manufactured, and one was deoxidizer A equipped with the water refilling device according to the present invention as shown in Fig. 1, and the other was equipped with a conventional water replenishing device that was airtight and had a liquid level regulating pipe. Assemble the oxygen device B and set each electrolytic cell to 7N (specific gravity 1).
．． 100 cc of caustic potash aqueous solution (28420°C) and 300 m9 of water were added to each water replenishment tank, and heat-cooling cycle tests were repeated at environmental temperatures of 35°C for 3 hours and 5°C for 3 hours.

In addition, in device A, when 300 cc of water is added to the refill tank, some of the water moves to the electrolytic tank side, and the electrolyte becomes 5N (specific gravity 1).
．． 25420°C).

After 50 cycles, the electrolytes in the two electrolytic cells were examined and found to be 51N in device A according to the present invention, but diluted to 3.2N in device B.

This difference is clearly due to the difference in the water replenishment device, and it means that the water replenishment tank of the device according to the present invention is of an open type and is therefore not affected by changes in environmental temperature.

Furthermore, the device according to the present invention has an open water replenishment tank as described above, and therefore has a great advantage in that water can be freely supplied.

As detailed above, the present invention provides a device that has excellent operability and prevents excessive dilution of the electrolyte.
Its industrial value is people.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional diagram of an electrochemical deoxidizer according to the present invention. FIG. 2 is a current-voltage characteristic diagram of the electrolytic cell in the atmosphere. 1... Electrolytic cell, 2... Water refilling device, 3.
...Cathode, 4...Anode, 5...
Caustic potash electrolyte, 12... Water replenishment tank, 14
...Air vent, 17...Water.

Claims (1)

[Claims] 1. A cathode consisting of a gas diffusion electrode capable of electrolytically reducing oxygen;
Equipped with an electrolytic cell consisting of an anode consisting of an oxygen-generating electrode and an electrolytic solution consisting of an aqueous solution such as caustic potash, and an open water tank for replenishing water to the electrolytic cell, the specific gravity of the electrolyte (ρ) and The relationship ρh=i should always hold between the liquid level height h) and the water level height 1) of the refilling tank, and the electrolyte concentration and liquid level height in the electrolytic cell should be kept within a certain range. An apparatus for separating oxygen from a mixed gas containing oxygen, characterized in that: