JPH0459014A - Gas separator - Google Patents

Abstract

PURPOSE:To gradually purge a remaining gas in a adsorption vessel and to efficiently desorb the gas adsorbed in the vessel by evacuating the vessel and returning the gaseous product compressed in a product tank to the adsorption vessel little by little in plural steps. CONSTITUTION:Gas discharge valves 13 and 14 are opened to discharge the remaining gas in adsorption vessels 1 and 2 into the atmosphere from a discharge pipeline 12, and the vessels 1 and 2 are controlled almost to atmospheric pressure. The pressure in a product tank 20 is read by the detection signal from a pressure sensor 30, the total returning time of the gaseous nitrogen at a specified flow rate, namely the total opening time of discharge valves 18 and 19, is calculated from the reading, and then the frequency of openings of the discharge valves 18 and 19 is calculated. The discharge valves 18 and 19 are intermittently opened based on the calculated frequency, and the gaseous nitrogen is intermittently returned to the upper parts of the vessels 1 and 2 little by little. The gaseous nitrogen is gradually moved downward in the vessels 1 and 2, and the vessel 1 and 2 are purged. Consequently, the precision in desorbing the adsorbent is enhanced, and the adsorbent is surely regenerated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas separation device, and particularly relates to a PSA type % type % type, in particular a structure configured to improve the accuracy of adsorbent desorption and reliably regenerate the adsorbent. The present invention relates to a gas separation device.

Conventional technology In general, a PSA gas separation device separates air into nitrogen and oxygen using an adsorbent made of molecular sieve carbon.
Fi L, either one is taken out and used as a product.

For this reason, for example, in a PSA nitrogen generator, there is an adsorption process in which an adsorption tank filled with an adsorbent is pressurized with compressed air, and a desorption process in which the inside of the adsorption tank is opened to the atmosphere or the pressure is reduced using a vacuum pump. The process is repeated, and in the adsorption process, oxygen molecules are adsorbed to the adsorbent in the adsorption tank and nitrogen is taken out as a product gas, while in the desorption process, the adsorbed oxygen is desorbed and transferred to the next adsorption process. Be prepared.

Problems to be Solved by the Invention With conventional equipment, for example, there is a problem in that it takes up to two hours from supplying compressed air to the adsorption tank at start-up until a product gas of the desired purity can be taken out. . Therefore, it has been considered to return the product gas stored in the product tank to a reduced pressure adsorption tank and purge the gas remaining in the adsorption tank into the atmosphere from the exhaust pipe of the adsorption tank.

However, in a nitrogen generator, when purging the adsorption tank with product gas, the take-out valve installed between the product tank and the adsorption tank is opened to remove the pressure accumulated in the product tank. The product gas compressed to a pressure of about 'gf/ci is refluxed for a short time.

In that case, since the purge time is short, it is not possible to efficiently purge the residual gas in the adsorption tank, and the oxygen adsorbed by the adsorbent cannot be sufficiently desorbed, resulting in problems such as low desorption accuracy.

Therefore, if the compressed product gas is directly returned to the adsorption tank as described above, it is not possible to completely purge the oxygen remaining in the adsorption tank, and even if the raw material gas is supplied to the adsorption tank, it will not be possible to completely purge the oxygen remaining in the adsorption tank. Another problem arises that it takes a long time to obtain nitrogen gas, making it impossible to shorten the rise time.

Also, if you lengthen the purge time to increase the attachment/desorption accuracy,
The amount of product gas consumed will increase, and the product gas that has been manufactured will be wasted.

In addition to the above purging method, in order to lengthen the purge time, the product gas stored in the startup special product tank is reduced to a low pressure and returned to the adsorption tank little by little, and the residual gas in the adsorption tank is gradually removed from the parts. There are ways to do this. However,
This method requires a dedicated purge pipe equipped with a pressure reducing valve to reduce the pressure of the product waste to a low pressure, which poses problems such as not only complicating the configuration of the gas separation device but also increasing manufacturing costs. Incidentally, the problem mentioned above occurs not only during startup, but also during the desorption process during normal product gas generation.

Therefore, an object of the present invention is to provide a gas separation device that solves the above problems.

Means for Solving the Problems The present invention supplies compressed gas to an adsorption tank filled with an adsorbent that adsorbs one gas, and opens a valve provided between the adsorption tank and a product tank. an adsorption step in which the pressure of the product gas generated by removing the first gas with the adsorbent is accumulated in the product tank; and the remaining gas in the adsorption tank is discharged to the outside to reduce the pressure in the adsorption tank. In a gas separation device that repeats a desorption step, the valve is intermittently opened while the adsorption tank is under reduced pressure, and the product gas in the product tank is divided into multiple portions and returned to the adsorption tank. It is equipped with a reflux means.

Operation: While the pressure inside the adsorption tank is reduced, the valve installed between the adsorption tank and the product tank is opened intermittently, and the pressurized product gas in the product tank is divided into small portions multiple times. By refluxing, residual gas in the adsorption tank is gradually purged,
By repeating the reflux operation, the inside of the adsorption tank is efficiently purged (desorbed).

Example FIG. 1 shows an embodiment of a gas separation device according to the present invention.

In the figure, 1 and 2 are the first. The second adsorption tank, each adsorption tank 1,
2 is filled with molecular sieves 1A and 2A, respectively.

A compressor 3 serves as a compressed air supply source, and the compressed air from the compressor 3 is alternately supplied to the adsorption tanks 1 and 2 via an air dryer 4 and piping 6 and 7, respectively. Air supply valves 8 and 9 each consisting of a solenoid valve are provided in the middle of the pipes 6 and 7.

As the air dryer, a refrigeration type dryer is used, and in the case of a refrigeration type, a preparatory operation time of about 5 minutes is required for pre-cooling the air dryer after startup.

10.11 is a pipe for discharging gas from the intake tanks 1 and 2 during desorption, and is connected to the common discharge pipe 12, and at the end of the discharge pipe 12 is a silencer 12 for discharging the gas during desorption.
A is provided. In the middle of each of the pipes 1.0.11, there is a gas discharge valve 1, which is a solenoid valve that alternately discharges the desorbed exhaust gas in the adsorption tank 1.2 every half cycle.
3.14 is provided.

15 and 16 are connected to the outlet sides of intake tanks 1 and 2, and adsorption tank 1
, take-out piping for taking out the nitrogen generated in 2, 1
7 is a take-out pipe connected to each pipe 15 and 16, and pipe 1
5.16 are provided with take-out valves 18 and 19, each consisting of an electromagnetic valve that opens alternately during a half cycle under control to be described later. Further, the extraction pipe 17 is connected to the lower end of the product tank 20.

As will be described later, these take-out valves 18 and 19 function as reflux valves that are opened when nitrogen gas (product gas) of the desired purity in the product tank 20 is refluxed to the adsorption tank 1.2 during startup. also works.

21 is a pipe that communicates the outlet sides of the adsorption tanks 1 and 2; 22 is a pressure equalization valve consisting of a solenoid valve provided in the middle of the pipe 21;
The pressure equalization valve 22 is opened for a predetermined short time at the end of a half cycle by the adsorption tanks 1 and 2 to equalize the pressure between the adsorption tanks 12.

Reference numeral 24 denotes a take-out pipe connected to the product tank 20, and a take-out valve 25 made of a solenoid valve is provided in the middle of the take-out pipe.

An oxygen sensor 27 detects the oxygen concentration (composition value) of the gas stored in the product tank 20. Also, oxygen sensor 27
The oxygen concentration detection signal is input to a control circuit 29, which will be described later.

The oxygen sensor 27 may be a magnetic oxygen sensor that utilizes the paramagnetism of oxygen molecules, or an electromagnetic oxygen sensor that utilizes the fact that when oxygen enters the electrolyte through a permeable membrane, an oxygen reduction reaction occurs at the electrodes and a current flows. A zirconia oxygen sensor is used, which uses electrodes provided on the inner and outer surfaces of zirconia porcelain to generate an electromotive force depending on the oxygen concentration.

Reference numeral 28 denotes a concentration setting switch for setting the nitrogen concentration, that is, the oxygen concentration taken out from the takeout pipe 24, and is set appropriately according to the nitrogen gas concentration to be taken out from the product tank 20.

A pressure sensor 30 detects the pressure of nitrogen gas accumulated in the product tank 20.

The control circuit 29 is a valve control means constituted by, for example, a microcomputer, and has an oxygen sensor 27. A concentration setting switch 28 is also connected. The control circuit 29 also includes a reflux control means 29A that executes the processing shown in FIG.

The control circuit 29 controls the air supply according to a program input in advance, for example, according to each process of pressurization (■, ■), extraction (■, ■), and pressure equalization (■, ■) shown in FIG. Valve 8, 9. Gas discharge valve 13, 14° extraction valve 18, 19. Pressure equalization valve 22. Controls the opening and closing of the take-out valve 25.

Here, as shown in Figure 4, the pressurization, extraction, pressure equalization, depressurization, and pressure equalization processes can be roughly divided into the adsorption process to generate product gas, and the residual gas in the adsorption tank 1.2 to be discharged to the outside. It is classified as a desorption process.

Each electromagnetic valve, which is controlled to open and close by the control circuit 29, opens when it is energized by the supply of a valve opening signal, and closes by spring force when it is not energized.

Here, the operation of the nitrogen generation cycle of the nitrogen generator will be explained.

First, the reflux operation at startup as a nitrogen generator will be explained with reference to FIG. 2, and then the basic operation of nitrogen generation will be explained with reference to FIGS. 3 and 4.

Now, when the nitrogen generator is started, the control circuit 29
Execute the process shown in the figure.

First, in step S1 (hereinafter the step will be omitted), the refrigerating air dryer 4 is energized and preparatory operation for pre-cooling is performed. Next, the gas discharge valve 13.14
The valve is opened (S2).

By opening the gas discharge valves 13 and 14, residual gas in the adsorption tank 12 is discharged from the discharge pipe 12. It is discharged into the atmosphere from the silencer 12a, and when 11 seconds have elapsed (S3), the pressure inside the adsorption tanks 1 and 2 is reduced to approximately atmospheric pressure.

In the next step 84, the pressure of the nitrogen gas accumulated in the product tank 20 is read from the detection signal from the pressure sensor 30. Next, based on the pressure in the product tank 20 detected by the pressure sensor 30, the total reflux time for refluxing a predetermined flow rate of nitrogen gas, that is, the take-out valve 18.19
The total valve opening time is calculated (S5). Next, the number of times the nitrogen gas is refluxed, that is, the take-out valve 18, is determined based on the pre-stored valve opening time per time and the total valve opening time of the reflux operation determined in step 85.
．． The number of valve openings n of 1.9 is calculated (S6).

In the next step 87, the time interval 12 (interval) from when the take-out valve 18 and 19 is closed until the next valve is opened is calculated based on the total time T of the air dryer 4 and the number of valve openings n obtained in 86. Calculate.

When the calculation in S7 is completed, the take-out valve 18°I9 is opened to start the recirculation operation (S8).

Since the pressure inside the adsorption tanks 1 and 2 is reduced to atmospheric pressure by opening the gas discharge valves 13.14, the nitrogen gas in the product tank 20 is released from the extraction pipe 17 at the same time as the extraction valves 18.19 are opened.
and 15 and 16 are reversed and supplied to the upper portions of adsorption tanks 1 and 2.

When the pre-stored opening time has elapsed after the take-out valves 18 and 19 are opened, the take-out valves 18 and 19 are temporarily closed (S9
). Then, the number of openings of the take-out valves 18 and 19 is counted, and it is confirmed whether the number of openings n determined in S6 has been reached (S10).

If the number of openings of the take-out valve 18 and 19 has not reached n times, proceed to S1.1 and calculate the time interval t2 calculated in S7.
Check whether the period has passed. Therefore, the take-off valve 18.1
When time t2 has elapsed since the valves 18 and 19 were closed, the process returns to 88 and the take-out valves 18 and 19 are opened again.

The processing from 88 to Sll is the number of valve openings (
n times) is repeated. As a result, the take-off valves 18, 19 are opened intermittently during the time interval t2. Therefore,
The high-purity nitrogen gas accumulated in the product tank 20 is intermittently returned to the upper part of the adsorption tank 1.2 little by little by repeating the opening and closing operations of the take-out valves 18, 19 as described above.

Therefore, nitrogen gas of the desired purity is intermittently supplied into the adsorption tank 1.2 from the upper part multiple times, and the nitrogen gas gradually moves to the bottom of the adsorption tank 1, 2. Purge inside. In addition, adsorption tank 1. The remaining gas in the exhaust pipe 12 is gradually discharged into the atmosphere through the exhaust pipe 12 each time nitrogen gas is intermittently supplied.

In S12, the time T(
In this embodiment, it is checked whether approximately 5 minutes have elapsed.

In this way, molecular sieve carbon IA is produced by intermittently refluxing nitrogen gas into the adsorption tanks 1 and 2 in small quantities over a long period of time.

The oxygen adsorbed by 2A is efficiently desorbed with a relatively small flow rate of nitrogen gas. Therefore, the accuracy of attachment and detachment can be improved.

Moreover, since the nitrogen gas is refluxed in small amounts in multiple batches, the amount of nitrogen gas consumed can be saved, and even if the purge time is long, the amount of nitrogen gas consumed is surprisingly small and will not be wasted.

After the above-mentioned time T has passed, the preparation operation of the air dryer 4 is completed, and the raw material gas can be dehumidified, and the adsorption tank 1
The purging (desorption) of the internal memory 2 is also completed (S13).

Subsequently, the gas discharge valves 13 and 14 are closed (S14).
. Compressor 3 is then started (step 515).
), the preparatory stage for nitrogen generation ends.

After this, normal nitrogen generation operation is performed. At this time, since the adsorption tanks 1 and 2 are filled with nitrogen gas as a product gas, nitrogen gas starts to be generated quickly and nitrogen gas of the desired purity can be generated in a short time.

Here, the normal nitrogen generation operation will be explained.

First, as shown in FIG. 4, operations ①, ②, ② are executed. ■ in Figure 3 indicates air supply valve 9 and gas discharge valve 1.
3 is opened, compressed air as a raw material gas is supplied to the second adsorption tank 2, and the second adsorption tank 2 is in a pressurized state (adsorption process).
Oxygen is adsorbed on the bimolecular sieve carbon 2A.

On the other hand, the adsorption tank 1 of Measure 1 is in a reduced pressure state (desorption process), and the adsorbed oxygen is desorbed and discharged.

Next, ■ in Fig. 3 indicates the air supply valve 9 and the gas discharge valve 1.
3, a state in which the extraction valve 19 is newly opened and the nitrogen gas in the second adsorption tank 2 is being taken out is shown. At this time, the first adsorption tank 1 remains in a reduced pressure state.

Next, ■ in Figure 3 indicates pressure equalization operation, and each take-out valve 18.1
9. and air supply valve9. Gas discharge valve 3 is closed, and pressure equalization valve 22 is opened.

As a result, the nitrogen-enriched gas remaining in the second adsorption tank 2 is recovered to the first adsorption tank 1, and each adsorption tank 12 becomes equal in pressure. Note that the pressure equalization operation usually takes 1 to 3 seconds.

This means that the first half of one cycle has been completed, and the air supply valve 8. Gas discharge valve 14
By opening the valve, as shown in FIG. 4(B), the latter half cycle shown by ■ to ■ in FIG. 3 is repeated. Thus, nitrogen scum can be removed from the adsorption tank 1.2 in the latter half of each half cycle and supplied to the product tank 20.

Since the adsorption tanks 1 and 2 are filled with nitrogen gas of the desired purity by the reflux operation, the nitrogen gas generated from the adsorption tanks 1 and 2 after startup is stable at the desired purity. do.

Although the above embodiments have been described using a nitrogen generator as an example, the present invention is not limited to this, and can also be applied to an oxygen generator.

In addition, in the "-2 embodiment, the take-out valves 1, 8, and 19 connected to both adsorption tanks 1 and 2 are opened simultaneously, or each take-out valve 18 and 19 is opened independently. Of course, the valve opening operation may be delayed in time.

Further, in the above embodiment, the product gas in the product tank 20 is intermittently refluxed to the adsorption tanks 1 and 2 at the time of startup, but this is not limited to the normal nitrogen generation cycle, that is, as shown in FIG. It goes without saying that after the desorption step shown, the product gas may be intermittently refluxed to the adsorption tank 1.2 as in the above embodiment.

Effects of the Invention As described above, the gas separation device according to the present invention is designed to divide the product gas accumulated in the product tank into a plurality of times and intermittently return it to the adsorption tank in small amounts while the adsorption tank is under reduced pressure. By gradually purging the gas remaining in the adsorption tank and repeating the reflux operation, the gas adsorbed by the adsorbent can be reliably desorbed, and the desorption accuracy can be improved. Moreover, the product gas that is refluxed can save the consumption of product gas, which is consumed in large quantities in a short period of time, so that even if the purge time is extended, the product gas in the product tank will not be wasted. Therefore, when producing the product gas, the product gas of the desired purity remains in the adsorption tank, and the product gas of the desired purity can be produced in a short time. In addition, it has the advantage of not providing separate pipes and valves for reflux, and by using an extraction valve for taking product gas from the adsorption tank for reflux, it is possible to prevent the device configuration from becoming complicated. .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the gas separation device according to the present invention, FIG. 2 is a flowchart for explaining the process executed by the control circuit when refluxing product gas, and FIGS. The figures are process diagrams for explaining the steps in producing the respective product gases. 1.2... Adsorption tank, 3... Compressor, 4...
Air dryer, 13.14... Gas discharge valve, 18° 19.25... Take-out valve, 20... Product tank, 2
9... Control circuit, 29A... Reflux control means, 30.
...Pressure sensor. Patent applicant 1. Kiko Co., Ltd.

Claims (1)

[Claims] Compressed gas is supplied to an adsorption tank filled with an adsorbent that adsorbs one gas, and a valve provided between the adsorption tank and a product tank is opened to absorb the adsorbent. The adsorption step of accumulating the pressure of the product gas generated by the removal of the first gas in the product tank, and the desorption step of exhausting the remaining gas in the adsorption tank to the outside and reducing the pressure inside the adsorption tank are repeated. The gas separation device includes a product gas reflux means that opens the valve intermittently while the pressure inside the adsorption tank is reduced, and returns the product gas in the product tank to the adsorption tank in multiple batches. A gas separation device characterized by: