JP3138067B2 - Gas separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a PSA type (Pressure Swi
In particular, the present invention relates to a gas separation device configured to reduce the pressure rise time in an adsorption tank during an adsorption step.

[0002]

2. Description of the Related Art Generally, a PSA-type gas separation apparatus separates air into nitrogen and oxygen using an adsorbent composed of molecular sieve carbon, zeolite, or the like, and takes out one of them as a product gas for use. .

For this reason, for example, PS for extracting nitrogen gas
In the type A gas separation device, an adsorption step of introducing compressed air from a compressor into an adsorption tank filled with an adsorbent to adsorb oxygen molecules on the adsorbent, and extracting nitrogen separated and generated by the adsorbent The removal step and the regeneration step of releasing the interior of the adsorption tank to the atmosphere or reducing the pressure with a vacuum pump to regenerate the adsorbent are repeated. That is, in the removal step, nitrogen in the adsorption tank is removed to the outside, and in the regeneration step, the adsorbed oxygen is desorbed to prepare for the next adsorption step.

[0004] In an apparatus having a pair of adsorption tanks, the pressure equalization step is performed after the removal step is completed in one adsorption tank and the regeneration step is completed in the other adsorption tank. In the pressure equalization step, the two adsorption tanks are communicated with each other, and the gas remaining in the adsorption tank after the removal step is supplied to the adsorption tank in the regeneration step to equalize the pressure and produce a higher purity product gas. Like that.

[0005]

However, in the gas separation apparatus, nitrogen gas is separated and generated by repeating each of the above steps. Compressed air in the air tank is supplied to the adsorption tank during the adsorption step.
Note that the compressor switches to the unload operation when the pressure of the air tank reaches the upper limit pressure, but the rotation speed of the motor for driving the compressor does not change and remains constant.

In the conventional gas separation device, the adsorption step is performed until the pressure inside the adsorption tank becomes necessary to adsorb oxygen molecules by the compressed air supplied from the air tank.
One cycle time of each of the above steps to is determined in accordance with the adsorption step time. However, in the past, the limit of one cycle time was determined by the capacity of the compressor, so that the adsorption process time could not be reduced without increasing the size of the compressor. Therefore, it was difficult to shorten the adsorption process time.

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

[0008]

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided an adsorbent,
The compressed air from the compressor
The pressure in the adsorption tank is increased and generated by the adsorbent in the adsorption tank
Configured to take out the product gas from the adsorption tank.
In the gas separation device, a motor for driving the compressor
The number of rotations according to the adsorption and removal operations of the adsorption tank
In which a motor rotation control means for driving said motor <br/> motor rotation control means, said by accelerated rotation speed of the set time the motor during the adsorption step of supplying compressed air to the adsorption vessel It is characterized in that the amount of compressed air supplied to the compressor is increased, and the rotation speed of the motor is controlled to a normal rotation speed except during the adsorption step.

[0010]

[0011]

According to the present invention, the speed of the motor driving the compressor can be increased for a set time in the adsorption step to increase the amount of compressed air supplied to the compressor, thereby improving the adsorption efficiency while reducing the load on the compressor. As a result, the adsorption process time can be shortened and the supply capacity of the product gas can be increased.

[0012]

1 to 3 show one embodiment of a gas separation apparatus according to the present invention.

In each of the figures, a gas separator 1 is a PSA type nitrogen generator that generates nitrogen from compressed air as a product gas, and starts operation when a start signal is received. The control device 2 controls the valves V _{1 to} V ₁₁ of the air supply unit 6 having the refrigeration dryer 3 and the compressor 5, the adsorption unit 7 and the storage unit 8.

The compressed air from the compressor 5 is dehumidified by the refrigeration dryer 3 and supplied to the adsorption unit 7 as dry and clean compressed air. The air supply unit 6 and the adsorption unit 7 are connected via a pipe 9. Therefore, the compressed air dried by the dryer 3 passes through the pipe 9 and is branched into the adsorbing unit 7 through the pipes 10 and 11 on the supply side. It is supplied to the adsorption tanks 7A and 7B. Piping 1
Exhaust pipes 12 and 13 are branched and connected to 0 and 11, respectively.

As shown in FIG. 2, the compressor 5 is an air compressor called a package type compressor. A compressor body 28, a motor 29 and an air tank 30 are three-dimensionally and compactly housed in a steel housing 27. Do it.

A vibration isolating rubber 32 is provided on a base 31 of the housing 27.
The gantry 33 is fixed via. The motor 29 is fixed on the gantry 33 via the spacer 34 and the air tank 3
0 is fixed on the gantry 33 via a bracket 35.

The compressor body 28 has piston / cylinder mechanisms 28A, 28B, 28C at the top of a crankcase 36.

A driving pulley 38 provided at a rear portion of the compressor body 28 is driven to rotate via a belt 40 wound around a pulley 39 of a motor 29 during an air compression operation, and each of the piston / cylinder mechanisms 28A, 28B, The piston of 28C is reciprocated. As a result, the air sucked by the piston / cylinder mechanisms 28A, 28B, 28C is compressed.

As shown in FIG. 3, a start switch button 42, a stop switch button 43, an operation hour meter 44, a discharge pressure display section 4
5 and so on are provided.

The piston / cylinder mechanisms 28A, 28B, 28C of the compressor body 28 are connected to air lines 46B, 46C.
And the air tank 30 through the air line 46A.
The compressed air generated by the compression operation of the compressor body 28 is stored in the air tank 30 through the air line 46A.

Reference numeral 47 denotes an inverter circuit (motor rotation control means) for controlling the number of rotations of the motor 29 for driving the compressor 5. The inverter circuit 47 once converts a sine wave alternating current into a direct current by a converter (not shown), and reversely converts it into a variable frequency alternating current by turning on and off a transistor (not shown). 29 can be arbitrarily changed. Therefore, the output shaft of the motor 29 is connected to the inverter circuit 47.
Is driven to rotate at a rotational speed corresponding to the variable frequency of the alternating current output from. Therefore, the inverter circuit 47 controls the motor 29 for driving the compressor 5 only at the time of the adsorption step to increase the amount of compressed air generated by the compressor 5 as described later.

As a result, the gas separation apparatus 1 improves the adsorption efficiency in the adsorption tanks 7A and 7B without increasing the size of the compressor 5, shortens the adsorption step time, and increases the product gas supply capacity.

Returning to FIG. 1, the description will be continued.

Outlet pipes 14 and 15 are connected to the upper portions of the adsorption tanks 7A and 7B, and a pressure equalizing pipe 16 for connecting the adsorption tanks 7A and 7B is provided between the pipes 14 and 15 in a horizontal manner. Have been. Further, the pipes 14 and 15 are connected to the suction unit 7.
And a storage unit 8. Further, a silencer 22 is provided in the exhaust pipes 12 and 13 connecting between the supply pipes 10 and 11.

The storage unit 8 contains N as product gas._TwoMoth
Tank 23 in which pressure is accumulated and the oxygen concentration in nitrogen tank 23
And an oxygen sensor 24 for measuring. Under the nitrogen tank 23
The piping 17 is connected to the suction tanks 7A and 7A.
High purity N separated in B_TwoThe gas is
It is supplied to the elementary tank 23. In addition, N _Two
An extraction pipe 25 for extracting gas is connected. This
The outlet pipe 25 is connected to the downstream N_TwoEquipment using gas (shown
)).

The oxygen sensor 24 is connected to the nitrogen tank 23 via a pipe 26.

Normally closed solenoid valves V _{1 to} V ₁₁ are provided in the pipes 10 to 16, 25, and 26, respectively.
₁ ~V ₈ reflux by a signal from the control unit 2 as will be described later, adsorption, regeneration, extraction, selectively opened in response to each step of pressure equalization.

In the gas separation device 1, the motor 2 of the compressor 5 is operated by operating the start switch button 42.
9 is activated and the piston / cylinder mechanism 28A, 28B,
28C is driven. Each piston / cylinder mechanism 28
The compressed air generated by A, 28B, 28C is stored in the air tank 30. The compressed air in the air tank 30 is supplied to the air dryer 3 to be dehumidified, and then supplied to the adsorption unit 3.

In the suction unit 7, first and second suction tanks 7 are provided.
Compressed air dried by the air dryer 3 is supplied into A and 7B, and nitrogen and oxygen are separated from the raw air while repeatedly increasing and decreasing pressure. In addition, in the adsorption unit 7, in order to stably supply nitrogen as a product gas, the pressure of the first adsorption tank 7A is increased and the second adsorption tank 7B during the adsorption step.
Then, the regeneration step is performed under reduced pressure, and when the first adsorption tank 7A is in the regeneration step, the second adsorption tank 7B is in the adsorption step.

Therefore, the control device 2 controls the opening and closing of each of the valves V _{1 to} V ₁₁ of the adsorption unit 7 based on a program inputted in advance so that the adsorption tanks 7A and 7B alternately generate nitrogen gas.

FIG. 4 shows the processing executed by the inverter circuit 47.

In the figure, the inverter circuit 47 operates in step S
In step 1 (hereinafter, steps are omitted), when the first adsorption tank 7A or the second adsorption tank 7B of the adsorption unit 7 is in the adsorption step, the process proceeds to S2, and the speed of the motor 29 of the compressor 5 is increased.

As the speed of the motor 29 increases, the amount of compressed air supplied to the compressor 5 increases, and the amount of compressed air supplied to the first adsorption tank 7A or the second adsorption tank 7B increases. Therefore, a predetermined pressure (for example, 5 kg) in the adsorption tank 7A or the adsorption tank 7B is used.
/ Cm ² ), the pressure-up time until reaching the pressure / cm ² ) is shorter than before, and the adsorption step time is shorter.

In the next step S3, when the elapsed time from the start of the suction step reaches a preset time, the suction step is finished and at the same time, the rotation of the motor 29 is reduced to a steady speed. This is because the operation of the compressor 5 becomes higher than the capacity by increasing the speed of the motor 29, so that the number of revolutions is reduced in steps other than the adsorption step to reduce the load on the compressor 5, and the life of the compressor 5 is extended.

The set time may be the same as the entire time of the adsorption step, but may be a predetermined time until the pressure in the adsorption tanks 7A and 7B reaches a predetermined pressure.

In S4, when the suction unit 7 enters the pressure equalizing step, the process returns to S1 to prepare for the next suction step. Therefore, the speed of the motor 29 increases the compressed air supply amount of the compressor 5 and the adsorption process time is shortened. Therefore, one cycle time of a series of adsorption, regeneration, extraction and pressure equalization processes is shortened, and the compressor 5 is enlarged. The nitrogen generation efficiency is improved without any conversion.

Here, the operation of the valves V _{1 to} V ₉ of the adsorption unit 7 that opens and closes in each step in the gas separation apparatus 1 having the above configuration will be described.

FIG. 3 shows the operation for each step. In the figure,
Each valve V ₁ ~V ₉ is a "white" is the open state,
“Black” indicates that the valve is closed. First Step (Adsorption Tank A = Reflux / Adsorption, Adsorption Tank B = Regeneration) In FIG. 3, the valves V ₁ , V ₃ and V ₆ are opened. Therefore, the compressed air from the dryer 3 is supplied to the adsorption tank 7A from below, and the nitrogen gas from the nitrogen tank 23 is returned from above. At the same time, the supply amount of compressed air from the compressor 5 is increased by the inverter circuit 47 as described above, the pressure in the adsorption tank 7A is increased in a short time, and the adsorbent filled therein adsorbs oxygen molecules.

The adsorbent composed of porous molecular sieve carbon is supplied to the adsorber tank 7 by the relationship between the pressure and the amount of adsorption shown in FIG.
Oxygen molecules are adsorbed according to the pressure change in A, and when the pressure is reduced, the oxygen molecules are desorbed by the pressure difference.

As can be seen from the compressor supply pressure diagram in FIG. 3, even if compressed air is supplied from the air tank 30 of the compressor 5 to the adsorption tank 7A during the adsorption step, the motor 2
The pressure supplied to the adsorption tank 7A by the speed increasing operation of 9 does not decrease rapidly, and the compressed air is supplied stably. In addition, adsorption tank 7
The adsorption performance at A is a predetermined pressure (for example, 5 kg / cm ² )
Above this is not a significant improvement, so in practice the adsorption tank 7
Operation state of the compressor 5 so as to keep the pressure substantially about 5Kg / cm ² of pressure in the A constant, the motor 2 in other words
The number of rotations 9 is controlled to increase or decrease.

[0041] Other residual gas by opening the adsorption vessel 7B in valve V ₆ is reduced is exhausted to the atmosphere. Therefore, the filler filled in the adsorption tank 7B is regenerated by desorbing the oxygen molecules adsorbed in the previous adsorption step.

[0042] Then, the suction tank 18 provided in the pressure equalizing pipe 16 is the valve V ₉ of the pipe 19 for exhaust is open, the adsorbent is regenerated inside is depressurized to atmospheric pressure. Second step (adsorption tank A = take-out, adsorption tank B = regeneration) In FIG. 3, as in the first step, the valves V ₁ , V ₃ ,
V ₆ is open.

[0043] because it is continued to be supplied with compressed air by the valve opening adsorption vessel 7A in valve V _1, a short time is increased to near the supply pressure of the compressor 5. Then, the nitrogen gas generated separated by the adsorbent is taken out into a nitrogen tank 23 through a valve V _3.

[0044] Incidentally, the other adsorption tank 7B is a regeneration step by opening the valve V _6. Further, as described above, the compressor 5 returns to the operation at the steady speed upon completion of the adsorption step of the adsorption tank 7A. Third Step (Adsorption Tank A, Adsorption Tank B = Equalization) In FIG. 3, after the valves V ₁ , V ₃ , V ₆ are closed, the valves V ₄ , V _{8 of the} equalization pipe 16 are opened. .

Since the removal process has been completed in one of the adsorption tanks 7A, the pressure has been increased to approximately the supply pressure from the compressor 5, whereas the regeneration process has been completed in the other adsorption tank 7B and the pressure has been reduced to approximately atmospheric pressure. Have been. The pressure in the adsorption tank 18 provided in the pressure equalizing pipe 16 is also reduced after the regeneration step is completed.

Therefore, N ₂ gas having a high nitrogen concentration remains in the adsorption tank 7A in a pressurized state.

When the valves V ₄ and V _{8 provided} on both sides of the equalizing adsorption tank 18 are opened, N ₂ in the adsorption tank 7A is opened.
Gas via a valve V ₄ as a pressure equalizing gas adsorption tank 18
Supplied to Then, when the pressure in the adsorption tank 18 is increased, oxygen molecules contained in the equalizing gas are adsorbed by the adsorbent.

[0048] Furthermore, is sent to the adsorption vessel 7B become high purity N ₂ gas than when a pressure equalizing gas separated generated by adsorption tank 18 is taken out from the adsorption tank 7A. Therefore,
The adsorption tank 7B is a high-purity N supplied through the adsorption tank 18.
It becomes pressurized by the _two gases and prepares for the next adsorption step.

As described above, in the equalizing step, the valve V
_4, since one of the adsorption tank 7A which has been boosted by the opening of the V ₈ is rapidly reduced pressure, the oxygen molecules adsorbed on the adsorbent in the previous adsorption step would be desorbed. As a result, the nitrogen concentration of the equalizing gas decreases, but oxygen molecules in the equalizing gas are adsorbed by the adsorbent filled in the adsorption tank 18 provided in the equalizing pipe 16, so that high purity by the equalizing step is achieved. N
₂ Gas generation efficiency is improved. Therefore, the amount of high-purity N ₂ gas generated increases, and the restart time can be further reduced.

In the pressure equalization step, the compressor 5 is periodically stopped, so that the compressor 5 is in the unload operation or the stopped state. However, when the pressure equalizing time is short when the amount of N ₂ gas used is large, the normal operation is performed without the unload operation or the stop state.

When the first to third steps shown in FIG. 2 are completed, the first to third steps are executed so that the adsorption tanks 7A and 7B are exchanged.

Next, a modified example of the present invention will be described.

In the above embodiment, the time of the adsorption step is set in advance, and the compressor 5 is operated by the inverter circuit 47.
The supply amount of compressed air from the tank increases, and the pressure in the adsorption tanks 7A and 7B is increased in a short time.
A pressure sensor for detecting the pressure in A, 7B may be provided, and the speed of the compressor 5 may be increased until the pressure in the adsorption tanks 7A, 7B reaches a predetermined pressure required for adsorption.

In the nitrogen tank 23 in which nitrogen as product gas is stored, the pressure varies according to the amount of product gas used on the downstream side. Therefore, a pressure sensor is provided in the nitrogen tank 23 to reduce the amount of product gas used. The speed of the compressor 5 may be increased accordingly. In this case, for example, when the pressure of the nitrogen tank 23 falls below a preset reference pressure, the compressor 5 is operated at an increased speed, and when the pressure of the nitrogen tank 23 reaches the reference pressure, the compressor 5 is operated normally.

In the above embodiment, the inverter circuit 47
Was given as an example, but the invention is not limited to this.
The number of rotations may be controlled by varying the supply voltage to the motor 9.

In the above embodiment, the pair of adsorption tanks 7A,
Although 7B is provided, it is needless to say that the present invention can be applied to an apparatus having two or more adsorption tanks.

In the above embodiment, each adsorption tank adsorbs oxygen molecules. However, it is needless to say that each adsorption tank adsorbs other gas molecules (for example, an oxygen generator). It is.

[0058]

[0059]

As described above, the gas separation apparatus according to the present invention
It is by accelerated the motor for driving the set time the compressor during the adsorption step it is possible to increase the compressed air supply of the compressor, while reducing the burden of the compressor to improve the adsorption efficiency, thereby the adsorption vessel This has the advantage that the adsorption efficiency can be improved, the time required for the adsorption step can be shortened, and the ability to supply product gas can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a gas separation device according to the present invention.

FIG. 2 is a configuration diagram of a compressor.

FIG. 3 is a process chart showing a valve operation in each process and a pressure change in each adsorption tank.

FIG. 4 is a flowchart showing a process executed by the inverter circuit.

FIG. 5 is a diagram showing the relationship between the amount of adsorbed oxygen molecules and the pressure of the adsorption tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas separation device 2 Control device 3 Refrigeration dryer 5 Compressor 6 Air supply unit 7 Adsorption unit 7A, 7B Adsorption tank 8 Storage unit 28 Compressor main body 29 Motor 30 Air tank 47 Inverter circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/04

Claims (1)

(57) [Claims] 1. A compressor filled in an adsorption tank filled with an adsorbent.
The pressure in the adsorption tank is increased by supplying compressed air from the
The product gas generated by the adsorbent in the adsorption tank is
A gas driving device for driving the compressor, wherein the motor drives the compressor.
Motor rotation driven by the number of rotations according to the loading and unloading operations
With control meansYes, The motor rotation control means supplies compressed air to the adsorption tank.
Set time in the suction process to supply the number of rotations of the motor
To increase the compressed air supply of the compressor
Then, except during the suction step, the rotation speed of the motor is set to a normal value.
Control at rotation speed A gas separation device characterized by the above-mentioned.