JPH0691926B2 - Pressure fluctuation adsorption separation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure fluctuation adsorption separation method, and particularly to a pressure fluctuation suitable for a small-sized oxygen generator used as a source oxygen source for medical or small-sized ozonizers. The present invention relates to a method of operating an adsorption separation device.

[Conventional technology]

It is known that oxygen can be separated from air by using zeolite as an adsorbent and repeating adsorption under pressure and regeneration (desorption) under reduced pressure alternately.
This method is widely used in the industrial field as a so-called pressure swing adsorption separation method (PSA method).

The initial PSA method is a simple one in which the pressure adsorption process and the decompression regeneration process are alternately repeated using two adsorption cylinders, and the product recovery rate is about 10 to 20%. there were. Therefore, Japanese Patent Publication No. 51-40549 discloses a process of gradually extracting the product grade gas existing at the product outlet end of the adsorption cylinder after the adsorption process with the supply of the raw material air being cut off (pressure equalization). , Parallel flow decompression) is used to obtain higher product purity and higher recovery rate than the conventional two-cylinder PSA method.

[Problems to be Solved by the Invention]

However, the PSA method described in the above-mentioned publication is developed for the purpose of industrial production of a large amount of oxygen of, for example, several m ³ / h or more, and the recovery rate is maximized in order to improve the economical efficiency. Consideration is given to increase. That is, in order to take out the product without disturbing the gas concentration distribution in the cylinder, a relatively slow cycle time is adopted, and repressurization takes a long time and slowly pressurizes the cylinder. Consideration is given to forming a sharp density distribution.

Therefore, a large amount of adsorbent is required in the above method due to the relationship between the amount of treated gas by the general PSA method, the amount of adsorbent, and the cycle time.

That is, the following formula, (In the above formula, W is the amount of adsorbent [kg], Q is the adsorption capacity [m ³ / k
g] and θ indicate the cycle time [h]. ), When the processing gas amount is constant, if the cycle time is doubled, for example, the adsorbent amount is required to be approximately doubled. Although improved, it requires a large adsorption cylinder, considerably increases the size of the entire apparatus, requires various flow meters and control valves, and complicates piping.

On the other hand, since the PSA method has an advantage that oxygen of high concentration can be continuously obtained at low cost, it has recently attracted attention as an oxygen source for medical use or a raw material for a small ozonizer. However, as described above, the PSA method that has been conventionally performed is mainly a large industrial device, and such a device cannot be brought into a hospital or home as it is, and compared with an ozonizer. However, the oxygen generator was much larger. Also such PS
It was difficult to obtain the desired performance even if the method A was directly applied to a small PSA device.

Therefore, an object of the present invention is to provide a pressure fluctuation adsorption / separation method capable of efficiently operating a small-sized PSA device suitable for medical use with a simple configuration.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the pressure fluctuation adsorption separation method of the present invention is a pressure-equalizing method in which the adsorption column that has completed the adsorption step and the adsorption column that has completed the regeneration step are connected at the raw material supply ends of both adsorption columns. The present invention is characterized in that the step is performed, and in particular, the time of the pressure equalizing step is set to 1/30 to 1/4 of the cycle time.

[Action]

As described above, by connecting both adsorption cylinders at the raw material supply end and performing pressure equalizing operation in an extremely short time, the cycle time can be shortened and the apparatus can be downsized.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an embodiment of a pressure fluctuation adsorption separation device to which the present invention is applied, and FIG. 2 shows an example of the time schedule.

This pressure fluctuation adsorption / separation device 1 includes two adsorption columns A, which are filled with an adsorbent that adsorbs nitrogen in the air, for example, zeolite.
B, an air compressor 2 for supplying raw material air (Air) to the adsorption cylinders A and B, and a product tank 3 for storing the generated oxygen gas (O ₂ ).
And the orifice 4 that connects the product outlet ends of both adsorption cylinders A and B, and the raw material supply provided to each adsorption cylinder A and B to switch both adsorption cylinders A and B between the adsorption process and the regeneration process. Valve 5
a, 5b, product outlet valves 6a, 6b, and exhaust valves 7a, 7b.

The operation method of the pressure fluctuation adsorption / separation device 1 will be described below with reference to the time schedule shown in FIG. 2 in which one cycle time is 72 seconds.

First, in the initial 30 seconds (process), one adsorption cylinder A (hereinafter referred to as A cylinder) is the adsorption process, and the other adsorption cylinder B (hereinafter referred to as B cylinder) is a part of the regeneration process. There is a vacuum purge step. During this time, the raw material air compressed to a predetermined pressure by the air compressor 2 is introduced into the A cylinder via the raw material supply valve 5a, and the nitrogen in the air is adsorbed by the adsorbent, and oxygen which is a weakly adsorbed component is oxygen. Is derived from the product derivation end.

Part of the oxygen derived from the A cylinder is introduced into the B cylinder from the product discharge end of the B cylinder via the orifice 4, and the rest becomes product oxygen and is stored in the product tank 3 via the product discharge valve 6a. It On the other hand, in the B cylinder, the gas in the cylinder is released to the atmosphere through the exhaust valve 7b to reduce the pressure, and the cylinder interior is purged by the oxygen introduced through the orifice 4. At this time, the raw material supply valve 5b and the product discharge valve 6b of the B cylinder and A
The exhaust valve 7a of the cylinder is closed.

The next 6 seconds (step) is a pressure equalization step in which the raw material supply ends of both cylinders are communicated. That is, the exhaust valve 7b of the B cylinder is closed and both raw material supply valves 5a and 5b are opened, so that the gas charged in the A cylinder at a predetermined pressure flows backward through the raw material supply valve 5a of the A cylinder to compress air. The raw material air supplied from the machine 2 is introduced into the B cylinder from the B cylinder raw material supply valve 5b. At this time, the product discharge valve 6a of the A cylinder may be open or closed.

After completing the pressure equalizing process for 6 seconds, the B cylinder enters the adsorption process for 30 seconds, and the A cylinder enters the depressurization purging process (process). That is, the raw material supply valve 5b and the product discharge valve 6b of the B cylinder and the exhaust valve 7a of the A cylinder are opened, and the other valves are closed. After 30 seconds, a pressure equalizing step (step) for 6 seconds similar to the above is started. Thereafter, this step is sequentially repeated to separate oxygen in the air to obtain product oxygen.

The product oxygen (O ₂ ) is obtained when a certain amount of oxygen in the product tank 3 is continuously discharged as a product in a predetermined amount, and one of the adsorption cylinders A and B is in the adsorption process (process,). When the product tank 3 is charged with the pressure, and in the pressure equalizing step (process,), the oxygen charged in the product tank 3 is released. Therefore, the product tank 3 is necessary for stabilizing the product pressure and purity to the product oxygen supply destination, and it is sufficient if it has a volume capable of maintaining the product flow rate only during the pressure equalizing step. Since the pressure equalizing step is short, a small one can be used. It may be omitted if the supply destination is provided with an appropriate buffer tank.

As described above, by performing the pressure equalization process by communicating the adsorption cylinder that has completed the adsorption process and the adsorption cylinder that has completed the regeneration process at the raw material supply ends of both adsorption cylinders, it is possible to slowly increase the time from the outlet end side of the conventional product. It is possible to perform the pressure equalization process that has been performed over an extremely short time. In addition, by finishing the pressure equalization process in a short time, it is possible to take the time of the next pressure reduction purge process sufficiently longer than the cycle time. As a result, the degree of regeneration of the adsorbent in the cylinder can be increased,
The product purity can be increased, and the purity stability and recovery rate can be improved.

The time of this pressure equalizing step varies depending on the volume of the adsorption cylinder, the operating pressure, the cycle time, etc., that is, the desired product amount, but it is usually sufficient to perform it for 2 to 6 seconds even considering the resistance of the pipes and valves. And it is preferable to set the cycle time to 1/30 to 1/4. Further, the cycle time is appropriately 10 to 60 seconds, preferably 30 to 40 seconds in consideration of the regeneration time of the adsorbent, and can be appropriately selected depending on the product amount and the desired size of the apparatus.

Also, when entering the adsorption process, the conventional simple PSA method switches at atmospheric pressure, and the adsorption pressure fluctuates greatly, so the product pressure can be supplied at a constant value of 0.3 kg / cm.
^Although it was about ² G, the pressure in the cylinder at the start of the adsorption process can be increased by carrying out the pressure equalization process as in the present invention, so that the product pressure can be increased to about 0.8 kg / cm ² G.

Furthermore, in the state pressure equalizing step, by performing the pressure equalization while continuing the supply of the raw material air, the cylinder pressure can be increased by the amount of the raw material air supplied. Since the process is short in time, the same effect can be obtained.

Here, the results of an experiment comparing the conventional simple PSA method and the PSA method of the present invention will be described. The operating conditions of the pressure fluctuation adsorption separation device are as follows: MS-5A adsorbent 2.5 kg, adsorption pressure 1.5 k
The g / cm ² G and the cycle time were set to 30 seconds, and only in the method of the present invention, the raw material supply pressure equalizing step was performed for 3 seconds in each cycle time. The results are shown in the table below.

[Advantages of the Invention] As described above, the pressure fluctuation adsorption separation method of the present invention allows the adsorption cylinder after the adsorption process and the adsorption cylinder after the regeneration process to communicate with each other at the raw material supply ends of both adsorption cylinders. Since the pressure equalizing step is performed for a short time, it is possible to take a sufficient time to regenerate the adsorbent even if the cycle time is shortened. That is, by shortening the cycle time, it is possible to obtain a product amount equal to or more than the conventional amount with a small amount of adsorbent, and to downsize the adsorption cylinder, air compressor, etc., and greatly downsize the entire device. You can

Further, since the pressure equalizing step can be performed by opening the valves on the raw material supply end side of both adsorption cylinders so as to communicate with each other, it is possible to simplify the apparatus without requiring fine flow rate adjustment or the like for pressure equalization. . Further, since the pressure inside the adsorption cylinder entering the adsorption step is increased by the pressure equalizing step before the adsorption step, the product pressure can be increased.

Therefore, by applying the method of the present invention, it is possible to significantly reduce the size of the pressure fluctuation adsorption / separation device, and it is suitable as a small oxygen generator used as a source oxygen source for medical or small ozonizers. A pressure fluctuation adsorption separation device can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a pressure fluctuation adsorption separation device to which the present invention is applied, and FIG. 2 is its time schedule. 1 ... Pressure fluctuation adsorption separation device, 2 ... Air compressor, 3 ... Product tank, 4 ... Orifice, 5a, 5b ... Raw material supply valve, 6a, 6b ... Product discharge valve, 7a, 7b ... Exhaust valve, A, B ... Adsorption cylinder

Claims (2)

[Claims] 1. A pressure fluctuation adsorption separation method in which at least two adsorption cylinders filled with an adsorbent are sequentially switched between an adsorption step and a regeneration step to separate oxygen, and an adsorption cylinder that has completed the adsorption step, and A pressure fluctuation adsorption separation method, characterized in that a pressure equalization step is performed by communicating the adsorption column after the regeneration step with the raw material supply ends of both adsorption columns. 2. The time of the pressure equalizing step is set to the cycle time.
The pressure fluctuation adsorption separation method according to claim 1, wherein the pressure fluctuation adsorption separation is 1/30 to 1/4.