JPH10118439A - Gas separating device based on psa process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the purity of a finished product gas and thereby improve its yield by describing and regenerating an adsorbent in each of adsorption cylinders in a required and optimal manner. SOLUTION: A feedstock gas is supplied under pressure into adsorption cylinders 3, 4 so that a stirringly absorptive gas is adsorbed by an absorbent, In addition, after an absorption step to extract a weakly absorptive gas as a finished product gas, the concentration of a detected exhaust gas is detected with a gas densitometer 11 and a purging gas control means 18 is controlled in accordance with the detached value at the time of a desorption step top reduce the internal pressure of the absorption cylinders 3, 4 to exhaust the strongly adsorptive gas by desorption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for improving the yield of a product gas and the purity of the product gas of a gas separation device by a pressure fluctuation adsorption method (hereinafter, also referred to as PSA method).

[0002]

2. Description of the Related Art A gas separation apparatus based on the PSA method absorbs a strongly adsorbent gas onto an adsorbent and removes a weakly adsorbent gas from the other end of the adsorption cylinder and uses it as a product gas. In some cases, the adsorptive gas is desorbed and used, and most of them are used to separate the source gas.

[0003] The adsorption column of the gas separation device separates gas by repeating the adsorption step and the desorption step. In this gas separation apparatus, it is required industrially that the purity of the product gas be high and the yield from the raw material gas be high.

In the adsorption step of the gas separation apparatus of the PSA method, a pressurized gas having a pressure sufficiently higher than the atmospheric pressure is used, and in the desorption step, the pressure is reduced to the atmospheric pressure. There is a vacuum regeneration method in which an adsorption step is performed using a pressurized gas, and a desorption / regeneration step uses a vacuum (at a pressure lower than the atmospheric pressure, usually 100 to 150 Torr). In the case of the former normal pressure regeneration system, a method of promoting regeneration by using a product gas as a purge gas in an adsorption column in a desorption step is also performed.

On the other hand, the vacuum regeneration method is to desorb a strongly adsorptive gas by lowering the pressure mainly by a vacuum pump, and a purge gas hardly flows into an adsorption column in a desorption step, or even a small amount of gas flows. good. In the case of the normal pressure regeneration method, the yield of obtaining the product gas from the raw material gas is lower than that of the vacuum regeneration method because of the use of a larger amount of the purge gas. In the case of the normal pressure regeneration method using a plurality of adsorption cylinders, when each adsorption cylinder is operating in a well-balanced manner, the yield and the purity are good, but the balance of each adsorption cylinder is lost and a large amount of purge gas flows into one cylinder. If the purge gas flows more than necessary for regeneration, it is wastefully released into the desorbed exhaust gas and discarded. Therefore, the amount of gas to be obtained as a product gas is reduced. Then, since more product gas is taken out than necessary to the adsorption cylinder in the adsorption step in which the product gas is being generated, the purity of the product gas is reduced.

On the other hand, when the purge gas is small, the regeneration of the adsorption column is not sufficient, the adsorption capacity cannot be recovered sufficiently, the gas generation capacity of the adsorption column is not sufficient, and the product gas concentration decreases. Becomes

As described above, it is best in the method that the adsorption step and the desorption step of each adsorption column are performed in a well-balanced and uniform manner in terms of purity and yield of the product gas. However, in the past, both the desorption process using the normal pressure regeneration method and the desorption process using the vacuum regeneration method were conventionally controlled by the time value of each process in most cases. It is assumed that However, depending on various conditions, desorption / regeneration of each adsorption cylinder may be necessary and may not be performed sufficiently, or the balance between the cylinders may not be maintained well.

For example, when the amount of the raw material gas sent to the adsorption cylinders is large in only one adsorption cylinder due to gas piping, the balance is lost if a uniform purge gas is supplied to all the adsorption cylinders. In addition, even if the supply amount of the pressurized gas is the same for all the adsorption cylinders, if the amount of the purge gas flows only to one cylinder, the balance will be lost again, and the PSA cycle of a certain adsorption cylinder will be lost. When the time becomes longer, too much air enters the adsorption column in the adsorption step, and at that time too much purge gas flows into the adsorption column in the simultaneous desorption step, and the regeneration balance of each adsorption column is disrupted. It will be.

Further, the amount of gas consumed by the gas separation device used and consumed may fluctuate depending on the reason of consumption. In this case as well, the cause of the imbalance between the adsorption cylinders is included. Further, when the consumption decreases over a long period of time, since the supply amount of the raw material gas may be small, the operation of the air compressor or the like is usually reduced to reduce the consumption of electric power or the like, thereby performing a reduction operation. Large-sized equipment consumes a large amount of power, so when the amount of product gas used decreases, the amount of power reduced by the reduced-volume operation of the equipment is also large. Is required. In response to this requirement, a method is employed in which the capacity and the number of operating vacuum pumps (when a plurality of pumps are used) and the capacity of an air compressor for feeding raw material gas and a vacuum pump for desorbing and exhausting gas are linked to the consumption gas amount.

The product gas generated in the gas separation device is extracted and consumed as a product gas, or is consumed inside the device as a purge gas for desorption regeneration of another adsorption column. Since the raw material gas is required to produce these, if the amount taken out as the product gas decreases, the raw material gas can be reduced accordingly, so that the capacity of the air compressor that feeds the raw material gas is reduced and the weight reduction operation can be performed. However, since the amount of raw material gas entering the adsorption column decreases and the amount of gas adsorbed by the adsorbent also decreases,
This means that the amount of the purge gas may be small. For this reason, the source gas for purging can be further reduced.

[0011] However, in the conventional reduction operation, there is no appropriate means for detecting the completion of the desorption regeneration, and therefore, an appropriate purge amount cannot be determined. In particular, even when the amount of product gas to be taken out is changed during the PSA process, the amount of purge gas is the same as the full load, and the amount of operation is simply reduced in relation to the amount of product gas taken out. Also when performing the weight reduction operation, the balance between the adsorption cylinders may be temporarily lost at the start of the operation. (This is also caused by fluctuations in heats of adsorption and desorption between the adsorption cylinders.) It is necessary and important to detect this imbalance immediately and to perform the corrective control.

[0012]

SUMMARY OF THE INVENTION In a gas separation apparatus based on the PSA method, desorption and regeneration of an adsorbent in each adsorption column are required and sufficiently performed to improve the purity of a product gas and improve the yield. A new technology is provided for the purpose of reducing power consumption.

[0013]

Means for Solving the Problems During the regeneration of the adsorption column, the strongly adsorbable gas is desorbed, and the concentration of the strongly adsorbable gas in the desorbed exhaust gas is increased and discharged. Thereafter, the product gas, which is a weakly adsorbable gas, flows in countercurrently from the product gas outlet as a purge gas, so that the mass transfer zone of the strongly adsorbable gas and the weakly adsorbable gas in the adsorption cylinder is closer to the inlet end than the outlet end. It was found that the concentration of the product gas (weakly adsorptive gas) in the desorbed exhaust gas gradually increased as it was pushed back and approached the vicinity of the inlet after a certain period of time, indicating that the regeneration of the adsorbent could be known. .

[0014] In the case of the vacuum regeneration method, although it is small,
Since the purge gas is supplied, the concentration of the desorbed exhaust gas in the desorbed exhaust gas is such that the strongly adsorbable gas is desorbed, the concentration of the strongly adsorbable gas in the desorbed exhaust gas increases, the concentration changes with time, and then the purge gas is purged. Since the concentration of the product gas becomes higher, the regeneration process of the adsorbent can be grasped. By changing the purge gas amount while monitoring the gas concentration in the desorbed exhaust gas or by changing the time of the desorption step, the state of regeneration of the adsorption column is managed to perform gas separation by the PSA method.

Therefore, the present invention takes the following measures. (Part 1) At least one adsorption column filled with an adsorbent is supplied with a pressurized gas, and the strongly adsorbent is adsorbed by the adsorbent to extract a weakly adsorbable gas as a product gas. A gas separation apparatus by a PSA method in which gas is separated by repeating an adsorption step and a desorption step in which the strongly adsorbent gas adsorbed on the adsorbent is decompressed and depressurized by depressurizing and exhausting the adsorption column to desorb and regenerate the adsorbent. In the desorption step, a purge gas introducing means for flowing the product gas in a countercurrent direction to the adsorption cylinder is provided, and a purge gas control means for controlling the purge gas is provided, and the gas concentration of the desorption exhaust gas of the adsorption cylinder in the desorption step is adjusted. The PSA method is characterized in that the gas concentration is measured by a gas concentration meter and the amount of the purge gas is controlled by the purge gas control means based on the gas concentration value of the desorbed exhaust gas obtained based on the measurement. That is a gas separation apparatus.

The present invention also employs the following means. (Part 2) In the gas separation apparatus, the gas concentration of the desorbed exhaust gas of the adsorption column in the desorption step is measured by a gas concentration meter, and the gas concentration value of the desorbed exhaust gas obtained based on this measurement reaches a predetermined value. A gas separation apparatus based on the PSA method, wherein the desorption step of the adsorption column is completed at the time when the gas separation is performed.

The present invention also employs the following means. (Part 3) In the gas separation device, the gas concentration of the desorbed exhaust gas of the adsorption cylinder in the desorption step is measured, and the change in the gas concentration value of the desorbed exhaust gas obtained based on the measurement results in
It is configured to detect that the regeneration process of the adsorbent of the adsorption column in the desorption step is completed, and to terminate the regeneration process of the adsorbent, such as stopping the inflow of the purge gas or terminating the evacuation operation, based on the detection result. PSA characterized by the following:
It is a gas separation device by the method. This method controls each adsorption cylinder, so that unnecessary purge gas does not flow, and the regeneration balance of a plurality of adsorption cylinders is adjusted, so that the product gas concentration generated in each adsorption cylinder is constant, high efficiency and high concentration products Gas is obtained.

Further, the present invention more specifically includes the following means. (4) The gas separation apparatus according to the PSA method, wherein the adsorbent is zeolite, the product gas is an oxygen-enriched gas, and the desorbed exhaust gas is a nitrogen-enriched gas. (Part 5) The gas separation apparatus according to the PSA method, wherein the adsorbent is a molecular sieve coal, the product gas is a nitrogen-enriched gas, and the desorbed exhaust gas is an oxygen-enriched gas. However, when molecular sieve is used, it is a speed separation type PSA that uses the difference in the adsorption speed of the adsorbent. Here, oxygen adsorbed quickly and nitrogen adsorbed slowly are referred to as strongly adsorbed gas and weakly adsorbed gas. It is regarded as the same as the non-adsorbent gas, and is generally referred to as a strongly adsorbent gas and a weak adsorbent gas.

In the present invention, the following measures are taken to reduce the purge amount to an appropriate value at the time of the reduction operation and to make the reduction operation more effective. (Part 6) having at least two adsorption cylinders filled with an adsorbent, having an air compressor for supplying a pressurized raw material gas to the adsorption cylinder, and a pressure sensor for measuring the pressure of the pressurized raw material gas;
The air compressor has a capacity adjusting means for adjusting the supply capacity of the raw material gas, and supplies a pressurized gas to the adsorption column and causes the adsorbent to adsorb the strongly adsorbent gas to thereby form the weak adsorbent gas. By a PSA method in which a gas separation is carried out by repeating an adsorption step of extracting gas as a product gas and a desorption step of depressurizing and exhausting the adsorption cylinder to desorb a strongly adsorbent gas adsorbed on the adsorbent and regenerate the adsorbent. In the gas separation device, a purge gas introducing means for flowing a product gas in a countercurrent direction in the adsorption cylinder in the desorption step is provided, and a purge gas control means for controlling a flow rate of the purge gas is provided. The control unit controls the amount of purge gas by the purge gas control means so that the exhaust gas concentration becomes a target value, and determines the purge gas flow rate based on the measured value. In addition, while detecting the supply pressure of the raw material gas to be supplied to the other adsorption column in the adsorption step in this state with the pressure sensor, the detected pressure signal is input to the control unit, and the control unit controls the air compressor. Is adjusted so as to be the source gas pressure to be set by the capacity adjusting means, thereby performing a more efficient reduction operation and reducing power consumption.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a flow sheet of the first embodiment, but the present invention is not limited to this. This is an example in which the present invention is applied to a two-cylinder normal-pressure regeneration type oxygen concentrator. The raw material gas pressurized into the adsorption cylinders 3 and 4 filled with zeolite, which is a strongly adsorbing gas of nitrogen, is introduced into the raw material gas inlet 1 and connected to the piping via the automatic valves 12 and 14 to introduce the raw material gas. I do.

An automatic valve 1 is provided at each inlet end of the adsorption cylinder.
The pipe is connected to a silencer 10 for releasing the desorbed exhaust gas to the atmosphere via pipes 3 and 15. Further, the desorbed exhaust gas is branched upstream of the silencer and connected to a gas concentration meter 11. The outlet end of each adsorption column is an automatic valve 16
And 17 are connected to the buffer tank 5 by piping, and a purge gas control means 18 for flowing a product gas in a counter-current manner to the adsorption cylinder is connected to an outlet end of each adsorption cylinder.

In addition, the inlet end and the outlet end of each adsorption column have a pressure equalization step between the adsorption step and the desorption step, and connect both adsorption columns during this step to equalize the pressure of both adsorption columns. For this purpose, piping is connected via automatic valves 7 and 6.

The purge gas control means 18 controls the flow rate of the purge gas flowing to the adsorption column during the desorption process by opening and closing the automatic valves by orifices 22, 23, and 24 directly connected to the plurality of automatic valves 19, 20, 21, respectively. It has a configuration that can be used. The control is performed by detecting the oxygen concentration of the desorbed exhaust gas with the gas concentration meter 11, transmitting the measured value to the control unit 2, converting the electric signal from the gas concentration meter 11 into a digital signal in the control unit, and converting the signal into a digital signal in the control unit. Then, the control unit 2 transmits the appropriate gas amount to the purge gas control unit 18 to control the flow rate of the purge gas. The control unit has a PSA operation control function in addition to the above functions, but the description of the signal line and power supply to each automatic valve by dotted lines is omitted because it is complicated and difficult to see. In this embodiment, the purge gas control means 18 comprises an automatic valve and an orifice.
The control was also performed stepwise by a combination that opened the automatic valve. However, the present invention is not limited to this example. For example, the control may be continuously performed using a mass flow controller, or an automatic valve connected in series with one orifice may be used. Alternatively, the flow rate of the purge gas may be controlled by changing the time during which the automatic valve is opened.

The source gas added to the source gas inlet 1 is sent to the adsorption column during the adsorption step by the automatic valve 12 or 14. If it is assumed that the automatic valve 12 is opened and air is supplied to the adsorption column 3, nitrogen gas, which is a strongly adsorbing gas, is adsorbed on the zeolite in the adsorption column 3 and oxygen gas ( Product gas) comes out, the product gas is the automatic valve 1
6 is opened and stored in the buffer tank 5.

In the meantime, the other adsorption cylinder 4 is connected to the automatic valve 1
4 and 17 are closed, 15 is open and silencer 1
The desorbed exhaust gas is released to the atmosphere via the air outlet 0 and the pressure is reduced, so that the adsorbed nitrogen gas is desorbed and discharged. Meanwhile, the concentrated oxygen gas (product gas) is supplied to the purge gas control means 1.
8, the gas flows into the adsorption column 4 being desorbed countercurrently from the outlet end. Although the oxygen concentration in the desorbed exhaust gas discharged to the silencer 10 is reduced by the desorbed nitrogen gas and is about 10% lower than the source gas, the desorption proceeds, the desorbed nitrogen gas decreases, and the purge gas ( Oxygen) indicates that as the mass transfer zone (MTZ) of the adsorbent moves from the outlet end to the inlet end, if the oxygen concentration in the desorbed exhaust gas becomes higher, the end of desorption is near.

Upon detecting that the concentration has increased, the controller 2 instructs the purge gas control means 18 to control the flow rate of the purge gas. That is, when the oxygen concentration of the desorbed exhaust gas increases, the purge gas amount is reduced. Eventually it can be zero. When the oxygen concentration in the desorbed exhaust gas is reached, how to change the purge flow rate depends on the time until the concentration of the desorbed exhaust gas is detected, that is, the time delay due to the gas flow from the inlet end of the adsorption column to the gas concentration meter and the gas concentration meter. The response (delay) is a problem, and it is necessary to instruct the purge gas control means 18 of a control amount assuming this delay.
In the case of the normal pressure regeneration method, since the purge gas flows at a large flow rate, the oxygen concentration in the desorbed exhaust gas increases, and it is necessary to reduce the purge gas inflow at a rapid response after the desorption is completed.

Therefore, a short pipe and a highly responsive gas concentration meter are required so as not to delay the gas concentration meter. And even if the oxygen concentration in the exhaust gas rises a little (1%
), Reduce the amount of purge gas. In some cases, it is controlled to be zero. If the total time delay is large depending on the system, and the control in the same cycle is too late, the control unit performs control in the next regeneration cycle of the adsorption cylinder. The capacity of the purge gas to be controlled depends on the capacity of the gas separation device. Also, it depends on whether the product gas production capacity is operating at 100%, 80%, or 50%. In addition, since the width and sharpness of the mass transfer zone change depending on the shape of the apparatus and the shape and type of zeolite used, it is necessary to adjust the amount of purge gas corresponding to these.

When the operation rate is 50% of the full load, the oxygen concentration of the desorbed exhaust gas increases from an early stage of the desorption process. However, when the amount of the introduced raw material gas is not reduced, the control is not necessary because the product gas is excessive, but during the reduction operation, it is necessary to control the amount of the purge gas appropriately while monitoring the exhaust gas concentration. Control is performed incorporating a delay until the gas concentration meter detects a change in the oxygen concentration in the desorbed exhaust gas. FIG. 3 shows an example of a change in the oxygen concentration in the desorbed exhaust gas. When the operation rate is low, the shape is indicated by B in the figure. At 100% operation rate, the desorption gas of each adsorption cylinder is A, one is B, and the other is C or D among a plurality of adsorption cylinders. If the concentration is different, the balance is lost and the concentration of the product gas becomes lower. Therefore, the control unit 2 sets the oxygen concentration of the desorbed exhaust gas to PS
The concentration value is monitored in relation to the switching cycle time of A, and the purge gas amount is controlled by the purge gas control means 18.
For example, in the case of D, the concentration of desorbed exhaust gas is reduced as shown by the dotted line in the case of D to improve the balance with C, so that a high concentration of the product gas and a high yield can be obtained. The yield in this embodiment is determined by the ratio of the amount of oxygen gas that can be taken out as a product gas to the total amount of oxygen contained in the raw material gas. The higher the yield, the better.

FIG. 2 shows a flow sheet of the second embodiment. This is a flow sheet diagram of a single cylinder type apparatus for concentrating nitrogen gas using air as a source gas. In this figure,
The air pump 25 is a pump that generates a function as an air compressor and a function as a vacuum pump by switching the automatic valves 12 and 13, and is connected to the inlet end of the adsorption cylinder by a pipe. The adsorption column 3 is a molecular sieve (CMS = Carbon morec) that adsorbs more oxygen than nitrogen in a shorter time.
(ultra Sieves), which is a PSA using the above-mentioned difference in adsorption speed. Here, a gas having a high adsorption speed is called a strongly adsorbing gas, and a gas having a low adsorption speed is called a weakly adsorbing gas. The outlet end of the adsorption cylinder is connected to the buffer tank 5 by a pipe via an automatic valve 16. The buffer tank 5 is connected to a product gas outlet 9 via a pressure reducing valve 8 by piping.

The air pump 25 switches the automatic valve 12 as shown by the solid line arrow to take in the outside air through the suction filter 26, compresses and pressurizes it, switches the automatic valve 13 as shown by the solid line arrow, and sends compressed air (source gas) to the adsorption cylinder 3. ). This is called an adsorption step. Then, the oxygen gas is adsorbed and removed by the molecular sieve charcoal filled in the adsorption column, and the concentrated nitrogen gas is taken out from the other outlet end. Therefore, the automatic valve 16 is opened and stored in the buffer tank 7. The stored nitrogen gas is supplied to the pressure reducing valve 8
, And is taken out from the product gas outlet 9 and consumed.

Before the adsorbent in the adsorption column 3 adsorbs oxygen gas and becomes saturated, the automatic valve 16 is closed, the automatic valves 12 and 13 are switched as indicated by the dotted arrows, and the air pump 25 is operated as a vacuum pump. The gas in the adsorption cylinder 3 is pumped out (evacuated), and the desorbed exhaust gas is sent to the outside air via the silencer 10 connected to the automatic valve 13. At this time, the desorbed exhaust gas is branched from the upstream of the silencer 10, the oxygen gas concentration in the desorbed exhaust gas is detected by the gas concentration meter 11, and the value is transmitted to the control unit 2. The control unit 2 also controls the PSA operation of the present apparatus entirely, but the illustration of the open / close signal line of the PSA control automatic valve related to the PSA operation is omitted because it becomes complicated.

The control unit 2 is entirely controlled by the CPU, and the density data is also A / D-converted from an analog value to a digital value in the board and processed by the CPU. The oxygen concentration in the desorbed exhaust gas of the nitrogen concentrator of this example is as shown in FIGS. That is, immediately after the automatic valve is switched to the desorption regeneration step, the adsorbed oxygen gas is desorbed and exhausted, so that the oxygen concentration in the desorbed exhaust gas becomes about 60% or more, and thereafter gradually decreases. In order to obtain a high concentration of nitrogen gas, the lower the oxygen concentration in the desorbed exhaust gas immediately before switching to the pressurization step, the higher the product gas concentration of nitrogen gas. In order to obtain a nitrogen gas concentration of 99.9% or more, it is necessary that the oxygen concentration in the desorbed exhaust gas be 10% or less. It may be. When the oxygen gas concentration in the desorbed exhaust gas reaches this value, it is considered that the desorption regeneration process has been completed, the desorption process is terminated, and the process proceeds to the adsorption process.

However, the specific relationship between the oxygen concentration in the desorbed exhaust gas and the product gas concentration depends on the delay time until the gas concentration is detected as described above. Here, a single-tube vacuum type is shown, but the same applies when applied to two or more, or three or four, multi-tube types, and the same applies to the gas concentration in the desorbed exhaust gas in the desorption process of each adsorption column. In this case, the degree of desorption is controlled. In addition to the desorption step and the adsorption step, each cylinder cycle can include a pressure equalization step or a pressure equalization step divided into a plurality of steps. In the case of a single-tube type, the process can be immediately advanced to the next step. However, in a system using a plurality of adsorption columns, there is a mutual relationship between the adsorption columns. Even if the adsorption / desorption regeneration process of the adsorption cylinder is completed, it is not possible to proceed to the next step due to other factors. In such a case, after the regeneration of the adsorbent has been completed and the desorption step has been completed, a plurality of adsorption steps are performed in a state where the length of time in the operation step is shifted to a step not related to the gas enrichment step. Synchronize with the process time of the other adsorption cylinders.

Although the embodiment of the normal pressure regeneration system for oxygen and the embodiment of the vacuum regeneration system for nitrogen gas have been described above, the gas in the desorbed exhaust gas is the same for the vacuum regeneration system for oxygen or the normal pressure regeneration system for nitrogen. The desorption / regeneration step for performing necessary and optimal desorption / regeneration can be performed while monitoring the excess / deficiency of the desorption state of the adsorbent in the regeneration step by detecting the concentration.

Next, another embodiment will be described. FIG. 5 shows a flow sheet of another embodiment. This is an example of a case where a vacuum regeneration method is combined with an air compressor and its capacity adjusting means 32 to perform a reduction operation. This is an oxygen PSA that uses air as the source gas, and the adsorption column has zeolite 13X or 5A.
Use type.

The air as the source gas is supplied to the source gas inlet 1
The compressed gas is compressed into a pressurized gas by an intake air compressor 30 and connected to the inlet ends of the adsorption tubes 3 and 4 filled with the zeolite via automatic valves 12 and 14.
A vacuum pump 31 is connected to the vacuum pump 31 via the vacuum pump 15 so as to be able to perform decompression and desorption of the adsorption cylinders, and to equalize the pressures of the two adsorption cylinders when the inlet ends of the two adsorption cylinders 3 and 4 are equalized. It is connected by a pipe via the automatic valve 7.

The product gases produced by connecting the automatic valves 16 and 17 to the outlet ends of the adsorption cylinders 3 and 4 are connected to the buffer tank 5 by piping, and the product gas is supplied from the buffer tank 5 through the pressure reducing valve 8. The product gas is taken out to the outside by connecting to the outlet 9 with piping.

The outlets of the adsorption tubes 3 and 4 are connected to each other by piping via an automatic valve 6 to connect the purge gas control means 18 and the outlets of both adsorption tubes at the time of pressure equalization. The purge gas control means 18 is a combination of an orifice and an automatic valve, controls the purge flow rate by the diameter of the orifice 22, and controls the time when the automatic valve 21 is opened by the control unit 2, thereby controlling the total amount of the purge gas. . This is an example, and a plurality of orifices and a plurality of automatic valves may be combined, or a method of performing linear control using a mass flow controller or the like may be employed.

A pressure sensor 28 is provided downstream of the air compressor 30 and upstream of the automatic valves 12 and 14 that enter the adsorption cylinders 3 and 4 to measure the pressure of the compressed gas. Similarly, a pressure sensor 27 is provided downstream of the automatic valves 13 and 15 for desorption and exhaust and upstream of the vacuum pump 31 to measure the degree of vacuum during desorption and regeneration of the adsorption tubes 3 and 4. The gas concentration meter 11 for measuring the gas concentration of the desorbed exhaust gas is provided downstream of the vacuum pump 31. Signals from the respective pressure sensors are transmitted to the control unit 2 through signal lines 29, 37, and 38. The control unit converts analog signals into digital signals, performs arithmetic processing by the CPU, and sends the signal to the purge gas control unit 18 based on the concentration of the desorbed exhaust gas through the signal line 40. The opening and closing timing of the automatic transmission valve 21 is controlled to control the total amount of the purge gas. The air compressor 30 is a pressure sensor 2
8, the supply pressure is measured, and the pressure is equal to the target pressure (2.
The signal is processed by the control unit 2 so as to be close to 5 kgf / cm ² G), transmitted to the capacity adjusting means 32 by a signal line 42, and the rotation speed of the motor of the air compressor 30 is controlled by a signal line 39.

Similarly, the degree of vacuum at the time of desorption and regeneration of the adsorption cylinder is measured by the pressure sensor 27, and this value is transmitted to the control unit 2 via the signal line 37, and the CPU of the control unit sets the target value to 150 Torr as an example. The arithmetic processing is performed, and the signal is transmitted to the capacity adjusting means 32 through a signal line 42, and the number of rotations of the motor of the vacuum pump 31 is controlled by a signal line 36 so as to reach a target value. Here, the capacity control means 32 controls the frequency of AC power supplied to each motor by an inverter to control the number of rotations of the motor. However, when the PSA device is large and a plurality of air compressors or blowers are used, or when a plurality of vacuum pumps for desorbing and evacuating are used, the capacity adjusting means needs to be provided. This includes adjusting the capability, including controlling the number of units on and off.

This reduces the amount of oxygen gas taken out,
In addition to reducing the amount of purge gas, it has become possible to perform a reduction operation of the air compressor that supplies the raw material gas. Specific numerical values of the first and second embodiments are shown below.

[0042]

Table 1 In the case of Example 1 (FIG. 1) (oxygen PSA) Adsorption cylinder capacity (2 L) 2 adsorbents Zeolite 1.2 kg (per cylinder) Air flow 33 L / min Operating pressure 2.5 kgf / cm ² G Extracted oxygen amount 3.3 L / min Oxygen concentration 91.8% Cycle time 26 seconds

[0043]

In the case of Example 2 (FIG. 2) (nitrogen PSA) Adsorption cylinder capacity (2 L) 1 adsorbent Molecular sieve coal 1.3 kg Air volume 22 L / min Operating pressure 6.0 kgf / cm ² G Removal nitrogen volume 3 0.0L / min Nitrogen concentration 99.9% Cycle time 180 seconds

A PSA having a plurality of adsorption cylinders as described above
Even in the case of the gas separation device, since the regeneration of the adsorbent is advanced while monitoring the desorption state of each of the adsorption cylinders in the desorption step, the regeneration is uniformly performed in any case.

[0045]

[Effects of the Invention] By performing each step of PSA while monitoring the state of desorption and regeneration of the adsorbent, a product gas can be obtained most efficiently and a gas with a high concentration can be obtained. Since it is possible to prevent the imbalance between the respective adsorption cylinders of the apparatus having a plurality of adsorption cylinders, the product gas concentration does not decrease. In addition, even when the amount of gas to be taken out is reduced, the amount of purge operation can be reduced (including an air compressor and a vacuum pump) efficiently by reducing the amount of purge.

[Brief description of the drawings]

FIG. 1 is a flow sheet according to a first embodiment of the present invention.

FIG. 2 is a flow sheet according to a second embodiment of the present invention.

FIG. 3A, FIG. 3B, FIG. 3C, and FIG.
FIG. 7 is a graph showing a change in oxygen concentration in desorbed exhaust gas in Example of FIG.

FIGS. 4A and 4B are graphs showing changes in the oxygen concentration in the desorbed exhaust gas in the second embodiment, respectively.

FIG. 5 is a flow sheet of another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Raw material gas inlet 2 Control part 3, 4 Adsorption cylinder 5 Buffer tank 8 Pressure reducing valve 9 Product gas outlet 10 Silencer 11 Gas concentration meter 6, 7, 12, 13, 14, 15, 16, 17, 19,
20, 21 Automatic valve 18 Purge gas control means 22, 23, 24 Orifice 25 Air pump 26 Suction filter 27, 28 Pressure sensor 29, 36, 37, 38, 39, 40, 42 Signal line 30 Air compressor 31 Vacuum pump 32 Capacity Adjusting means 34 Power plug

Claims (6)

[Claims] 1. A pressurized gas is supplied to at least one adsorption column filled with an adsorbent, and the strongly adsorbent gas is adsorbed by the adsorbent to convert the weakly adsorbable gas into a product gas. A pressure fluctuation adsorption method for performing gas separation by repeating a removal step of removing the adsorption column and a desorption step of decompressing and depressurizing the strongly adsorbent gas adsorbed on the adsorbent and desorbing and regenerating the adsorbent by depressurizing and exhausting the adsorption column. In the gas separation apparatus based on the PSA method), a purge gas introducing means for causing a product gas to flow in a countercurrent direction to an adsorption column in a desorption step is provided, and a purge gas control means (18) for controlling the purge gas is provided.
The gas concentration of the desorbed exhaust gas of the adsorption column in the desorption step is measured by a gas concentration meter (11), and the amount of the purge gas is controlled by the purge gas control means based on the gas concentration value of the desorbed exhaust gas obtained based on this measurement. A gas separation apparatus based on the PSA method, wherein the gas separation apparatus is configured as described above. 2. In the above gas separation apparatus, the gas concentration of the exhaust gas desorbed from the adsorption cylinder in the desorption step is measured by a gas concentration meter (1).
2. The method according to claim 1, wherein the measurement is performed in 1), and the desorption process of the adsorption column is terminated when a gas concentration value of the desorption exhaust gas obtained based on the measurement reaches a predetermined value. Gas separation apparatus by the PSA method. 3. The gas separation apparatus according to claim 1, wherein the gas concentration of the desorbed exhaust gas of the adsorption column in the desorption step is measured with a gas concentration meter (1).
1), a change in the gas concentration value of the desorbed exhaust gas obtained based on this measurement is used to detect the completion of the regeneration process of the adsorbent of the adsorption column in the desorption step. 2. The gas separation apparatus according to claim 1, wherein the regeneration process of the adsorbent is terminated. 4. The method according to claim 1, wherein the adsorbent is zeolite, the product gas is an oxygen-enriched gas, and the desorbed exhaust gas is a nitrogen-enriched gas. Gas separation device by PSA method. 5. The method according to claim 1, wherein the adsorbent is a molecular sieve, the product gas is a nitrogen-enriched gas, and the desorbed exhaust gas is an oxygen-enriched gas. Gas separation apparatus by the PSA method. 6. An air compressor having at least two adsorption tubes filled with an adsorbent and supplying a pressurized source gas as a source gas to the adsorption tubes, and a pressure for measuring the pressure of the pressurized source gas. The air compressor has a capacity adjusting means for adjusting the supply capacity of the raw material gas, supplies a pressurized gas to the adsorption column, and causes the adsorbent to adsorb the strongly adsorbent gas. The gas separation is performed by repeating an adsorption step of extracting a weakly adsorbent gas as a product gas and a desorption step of depressurizing and exhausting the adsorption column to desorb the strongly adsorbent gas adsorbed on the adsorbent and regenerate the adsorbent. In the gas separation apparatus by the PSA method for performing the above, a purge gas introducing means for flowing the product gas in a countercurrent direction to the adsorption cylinder in the desorption step is provided, and a purge gas control means (18) for controlling the flow rate of the purge gas is provided.
The gas concentration of the exhaust gas desorbed from the adsorption cylinder in the desorption step is measured by a gas concentration meter (11), and based on the measured value, the control unit uses the purge gas control means to adjust the amount of the purge gas to the target value of the exhaust gas concentration. And the flow rate of the purge gas is determined, and in this state, while the supply pressure of the raw material gas supplied to the other adsorption column in the adsorption step is detected by the pressure sensor, the detected pressure signal is sent to the control unit. And a controller for controlling the capacity of the air compressor so that the capacity of the air compressor is adjusted to the amount of the raw material gas to be set by the capacity adjusting means.