JPH0731825A - Gas separator - Google Patents

Abstract

PURPOSE:To provide a gas separator constituted so as to hold the concn. and pressure of a product gas to prescribed values even when the gas molecule adsorbing capacity of an adsorbent is lowered. CONSTITUTION:In a gas separator, when the air compressed by a compressor 3 is supplied to adsorbing tanks 1, 2, adsorbents 1A, 2A adsorb a nitrogen atom and oxygen gas is supplied to a product tank 20. A control device 28 controlling the opening and closing of respective solenoid valves has an air supply time altering means 28A shortening the compressed air supply time to the adsorbing tanks 1, 2 when the concn. of product gas due to an oxygen concn. sensor 27 becomes a predetermined value or less and a replacing time information means 28B allowing an alarm device 30 to emit an alarm when the compressed air supply time is shortened to inform that adsorbents 1A, 2A reach a replacing time.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a PSA type (Pressure Swi
ng Adsorption) gas separator, and more particularly to a gas separator configured so that the product gas concentration does not decrease even if the gas molecule adsorption capacity of the adsorbent decreases.

[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 or zeolite, and extracts either one as a product gas for use. .

Therefore, for example, a PS for taking out oxygen gas
In the A-type gas separation device, an adsorption step of introducing compressed air from a compressor into an adsorption tank filled with an adsorbent to adsorb a part of nitrogen molecules and oxygen molecules on the adsorbent,
An extraction process for extracting oxygen generated separately by the adsorbent,
The regeneration step of regenerating the adsorbent by releasing the atmosphere in the adsorption tank to the atmosphere or reducing the pressure with a vacuum pump is repeated. That is, in the extraction step, oxygen in the adsorption tank is taken out to the outside, while in the regeneration step, adsorbed nitrogen and some oxygen are desorbed to prepare for the next adsorption step.

Further, in an apparatus having a pair of adsorption tanks, the pressure equalization step is carried out after the extraction step is completed in one adsorption tank and the regeneration step is completed in the other adsorption tank. In this pressure equalization process, both adsorption tanks are communicated with each other and the gas remaining in the adsorption tank after the extraction process is supplied to the adsorption tank in the regeneration process to equalize pressure and continuously produce a product gas of higher concentration. I am trying to generate it.

[0005]

However, in the above gas separation apparatus, the above steps (1) to (4) are repeated to separate and generate nitrogen. However, the compressed air supplied from the air tank of the compressor causes gas molecules in the adsorption tank to be generated. Is adsorbed and the pressure is increased to the optimum pressure for obtaining a high concentration product gas. Then, in the gas separation device, the optimum adsorption process time for increasing the pressure to this optimum pressure is set, and one cycle time of each of the above processes is determined in accordance with the adsorption process time.

However, when a higher concentration product gas and a higher pressure are required, one cycle time is changed to be longer than a preset optimum time in order to increase the product gas pressure. There is a need to.

However, when one cycle time is lengthened, the life of the adsorbent becomes shorter than when the adsorbent is operated at the optimum time, which causes a problem that the adsorbent replacement time is shortened.

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

[0009]

The invention according to claim 1 is
In a gas separation device configured to supply compressed air to an adsorption tank filled with an adsorbent to increase the pressure inside the adsorption tank and to take out a product gas generated by the adsorbent in the adsorption tank from the adsorption tank. And an air supply time changing means for shortening the compressed air supply time to the adsorption tank when the concentration of the product gas taken out from the adsorption tank becomes equal to or lower than a predetermined value.

Further, the invention of claim 2 supplies compressed air to an adsorption tank filled with an adsorbent to increase the pressure in the adsorption tank,
In a gas separation device configured to take out the product gas generated by the adsorbent in the adsorption tank from the adsorption tank,
When the concentration of the product gas taken out from the adsorption tank becomes equal to or lower than a predetermined value, the air supply time changing means for shortening the compressed air supply time to the adsorption tank, and the compressed air supply time by the air supply time changing means. When it is shortened, a replacement time notification means for notifying that it is time to replace the adsorbent,
It is characterized by comprising.

[0011]

According to the invention of claim 1, even when the concentration of the product gas taken out from the adsorption tank by the air supply time changing means becomes less than a predetermined value, the compressed air supply time to the adsorption tank is shortened and the product gas is reduced. The concentration of is returned to the predetermined value or more.

Further, according to the invention of claim 2, the compressed air supply time to the adsorption tank is shortened by the air supply time changing means to return the concentration of the product gas to a predetermined value or more, and the replacement time informing means adsorbs the gas. Notify when it is time to replace the adsorbent and replace the adsorbent before it becomes unusable.

[0013]

1 to 3 show an embodiment of a gas separation device according to the present invention. In this example, a case where the gas separation device is used as an oxygen generator will be described.

In the drawings, reference numerals 1 and 2 denote first and second adsorption tanks, respectively.
Each of the adsorption tanks 1 and 2 is filled with adsorbents 1A and 2A made of zeolite that adsorb nitrogen molecules in the air.

Reference numeral 3 denotes a compressor serving as a compressed air supply source, and the compressed air from the compressor 3 is dehumidified by an air dryer 4. This is because the zeolite has a property of adsorbing moisture together with nitrogen molecules in the air.

The air dried by the air dryer 4 is alternately supplied to the adsorption tanks 1 and 2 via the pipes 6 and 7, respectively. Therefore, air supply valves 8 and 9 each formed of a solenoid valve are provided in the middle of the pipes 6 and 7.

Numerals 10 and 11 are pipes for discharging the residual gas in the adsorption tanks 1 and 2 during the regeneration process for desorption, and are connected to a common exhaust pipe 12, and the exhaust pipe 12 supplies the desorbed exhaust gas (nitrogen gas). It is designed to be discharged. And
In the middle of the pipes 10 and 11, exhaust valves 13 and 14 each of which is an electromagnetic valve for alternately discharging the desorbed exhaust gas in the adsorption tanks 1 and 2 every half cycle are provided.

Denoted by 15 and 16 are extraction pipes connected to the outlet sides of the adsorption tanks 1 and 2 to take out oxygen separated and produced in the adsorption tanks 1 and 2, and 17 is an extraction pipe connected to the respective pipes 15 and 16. In the middle of the pipes 15 and 16, there are provided extraction valves 18 and 19 each of which is an electromagnetic valve which is alternately opened under the control described later for half a cycle. The take-out pipe 17 is connected to the product tank 20. In addition, a check valve 21 for preventing the product gas (oxygen gas) stored in the product tank 20 from flowing backward through the take-out pipe 17.
Is provided.

Reference numeral 22 is a pressure equalizing pipe that connects the outlet sides of the adsorption tanks 1 and 2. Reference numeral 23 is a pressure equalizing valve provided in the middle of the pipe 22. The pressure equalizing valve 23 is opened by the adsorption tanks 1 and 2 for a predetermined time at the end of the half cycle to equalize the pressure between the adsorption tanks 1 and 2.

A product gas supply pipe 24 for supplying a product gas to the downstream side is connected to the product tank 20. The product gas supply pipe 24 is provided with an opening / closing valve 25 which is an electromagnetic valve.

A pressure sensor 26 measures the pressure in the product tank 20 and outputs a detection signal corresponding to the pressure value.

27 is an oxygen concentration sensor, which is a product tank 20.
The oxygen concentration of the product gas stored therein is measured, and a detection signal corresponding to the measured oxygen concentration value is output.

Reference numeral 28 denotes a control device, which outputs a control signal to the sequencer 29 in accordance with a program input in advance, for example, adsorption, regeneration (,), extraction, regeneration (,), pressure equalization (, ), Air supply valves 8 and 9, exhaust valves 13 and 14, and extraction valves 18 and 1.
9. The opening / closing control of the pressure equalizing valve 23 is performed. In addition, the control device 27
The air supply time changing means 28A for shortening the compressed air supply time to the adsorption tanks 1 and 2 and the compressed air supply time are shortened when the oxygen concentration sensor 27 reduces the concentration of the product gas to a predetermined value or less. At this time, there is provided a replacement timing informing means 28B for issuing an alarm from the alarm device 30 and notifying that the adsorbents 1A and 2A have reached the replacement timing.

Now, the operation of a general oxygen generation cycle of the above oxygen generator will be described.

When the oxygen generator is started, oxygen is generated under the control of the controller 27.

First, as shown in FIG. 2, the operations of and are executed in numerical order. 2 is an air supply valve 9
And the gas discharge valve 13 are opened, compressed air as a raw material gas is supplied to the second adsorption tank 2, the second adsorption tank 2 is in a pressurized state, and the adsorbent 2A contains nitrogen and oxygen. This is an adsorption process in which parts are adsorbed. On the other hand, the first adsorption tank 1 is in a decompressed state, which is a regeneration process in which adsorbed nitrogen and some oxygen are desorbed and discharged.

Next, in addition to the air supply valve 9 and the gas discharge valve 13 shown in FIG. 2, a take-out valve 19 is newly opened to take out oxygen gas from the second adsorption tank 2. The removal process is shown. At this time, the first adsorption tank 1 remains in a depressurized state (regeneration step).

Next, in the pressure equalization step in FIG. 2, the extraction valve 19, the air supply valve 9, and the exhaust valve 13 are closed and the pressure equalization valve 23 is opened. As a result, the oxygen-nitrogen mixed gas remaining in the pressurized second adsorption tank 2 is supplied to the first adsorption tank 1 depressurized to the atmospheric pressure, and the adsorption tanks 1 and 2 are almost equalized in pressure. Become.

As a result, the first half of one cycle is completed, and the air supply valve 8 and the exhaust valve 14 are opened, as shown in FIG. 3 (B). Repeat the latter half cycle shown in the middle of.
Thus, oxygen gas can be extracted from the adsorption tanks 1 and 2 in the latter half of each half cycle and supplied to the product tank 20. Then, after a while after starting, the concentration of the oxygen gas generated from the adsorption tanks 1 and 2 becomes stable.

FIG. 4 shows that the air supply valves 8 and 9, the exhaust valves 13 and 14, the take-out valves 18 and 19, and the pressure equalizing valve 23 are normally opened and closed to adsorb, take out, and equalize the pressure. It is a diagram which shows the pressure change in a regeneration process. In the figure, the one-dot chain line shows the pressure change in the adsorption tank 1, the two-dot chain line shows the pressure change in the adsorption tank 2, and the solid line shows the pressure change in the product tank 20.

From the diagram of FIG. 4, the pressure in the adsorption tanks 1 and 2 is
Pressure P in the extraction process₁Up to the pressure P in the regeneration process₂Well
Depressurize with (P₁> P₂). The product tank 20 pressure is
Power P ₃And pressure P_FourFluctuates between (P₃> P_Four).

The characteristics of the adsorbents 1A and 2A filled in the adsorption tanks 1 and 2 will be described.

FIG. 5 is a diagram showing the relationship between the take-out time and the change in pressure of the product tank 20. In the figure, it can be seen that the pressure of the product tank 20 also increases as the take-out time (the time during which the take-out valve 18 or 19 is open) increases. Therefore, when a product gas having a high pressure is required, the take-out time may be lengthened.

FIG. 6 is a diagram showing the relationship between the take-out time and the oxygen concentration. In the figure, in order to obtain a product gas having a predetermined concentration, it is necessary to set the extraction time to the optimum time Ta. However, as can be seen from FIG. 6, when the take-out time is close to the optimum time Ta, the oxygen concentration is almost constant, but the times Tb, T outside the optimum time Ta are exceeded.
It can be seen that the oxygen concentration sharply decreases before and after c.

In the present embodiment, when high pressure and high concentration are required by utilizing the above two characteristics, by setting the take-out time to be longer, for example, oxygen gas having a pressure of 5 kgf / cm ² and a concentration of 90% is used. Can be obtained.

Now, the zeolite used for the adsorbents 1A and 2A will be described.

Zeolite has a property of adsorbing moisture together with nitrogen molecules in the air. Moreover, due to the nature of zeolite, it is difficult to desorb the water once adsorbed to the zeolite from the zeolite.

Therefore, when the operation is continued for a long time, the amount of water adsorbed on the surface of the zeolite increases, and nitrogen molecules cannot be adsorbed by that amount. As a result, non-adsorbed nitrogen molecules are mixed in the product gas, and the concentration of the product gas is significantly reduced.

The control device 28 performs control for solving such a problem.

That is, when the oxygen concentration decreases to a prescribed concentration (for example, 90% oxygen concentration) or less, by shortening the take-out time, the time period during which the raw material air is supplied to the adsorption tanks 1 and 2 is also reduced. It gets shorter. Therefore, adsorption tanks 1, 2
The absolute amount of the raw material air therein decreases, and the total amount of nitrogen molecules that the adsorbents 1A and 2A must adsorb also decreases. Therefore, it is possible to sufficiently cope with zeolite whose adsorption capacity has deteriorated, and the oxygen concentration of the product gas taken out from the adsorption tanks 1 and 2 is restored to the specified concentration.

On the other hand, in the case of the zeolite whose adsorption capacity is deteriorated, the total amount of adsorbable gas molecules, that is, a part of nitrogen molecules and oxygen molecules is reduced. Therefore, the number of oxygen molecules existing in the adsorption tanks 1 and 2 in a gas state without being adsorbed by the zeolite increases, and as a result, the pressure in the adsorption tanks 1 and 2 increases. Therefore, the product gas pressure can be maintained at a high pressure even if the take-out time is shortened.

Here, the processing executed by the control device 28 will be described with reference to FIG.

In FIG. 7, the control device 28 controls the step S1.
In (hereinafter, “step” is omitted), the warm-up mode is set, and the compressor 3 and the air dryer 4 are started. Then, when the normal operation mode is set, each solenoid valve is controlled to open and close so as to perform the above-described oxygen generation cycle (see FIGS. 2 and 3).

At the next S3, the detection signal from the oxygen concentration sensor 27 provided in the product tank 20 is read, and the oxygen concentration of the product gas stored in the product tank 20 is 90%.
Check if above. If the oxygen concentration is 90% or more, the adsorbing ability of the adsorbents 1A and 2A has not deteriorated, so the process returns to S2 and the normal operation mode is continued.

However, in S3, when the oxygen concentration of the product gas falls below 90%, the take-out time is changed so that the take-out time of the product gas is shortened by 1 second.

Subsequently, the alarm lamp 30 is turned on to inform the operator that the adsorbing ability of the adsorbents 1A and 2A has decreased. This is because, as described above, zeolite cannot adsorb nitrogen molecules when the amount of water adsorbed on the surface increases.

As a result, unadsorbed nitrogen molecules are mixed in the product gas, and the product gas concentration is significantly reduced.
Therefore, when the alarm lamp 30 is turned on, the adsorbent 1A,
It became clear that it was time to replace 2A, and adsorbents 1A and 2
A can be replaced before it becomes unusable, and sudden interruption of operation is prevented during operation.

Then, after waiting for 60 minutes in S6,
Proceed to 7 and the product tank 2 measured by the pressure sensor 26
0 pressure is read and the product tank 20 pressure is 5 kgf /
Check if it is less than cm ² . If the pressure of the product tank 20 drops to 5 kgf / cm ² or less after waiting for 60 minutes, the process proceeds to S8 and it is determined that the device is abnormal, and the device is stopped.

However, the pressure of the product tank 20 is 5 kgf /
When it is not less than cm ^2, the process returns to S2 again, and the oxygen generation operation is performed in the operation cycle in which the extraction time of the normal product gas is shortened by 1 second. When the oxygen concentration of the product gas is 90% or less, the taking-out time of the product gas is shortened again by 1 second in S4, and the shortening of the taking-out time is repeated until the oxygen concentration becomes 90% or more.

By changing the take-out time, the take-out time becomes shorter than usual, and the time period for which the raw material air is supplied to the adsorption tanks 1 and 2 is shortened accordingly. Therefore, the absolute amount of the raw material air in the adsorption tanks 1 and 2 is Decrease. Therefore, the adsorbents 1A and 2A whose adsorbing ability is deteriorated can generate oxygen gas of a specified concentration.

In addition, the adsorbents 1A and 2A whose adsorption ability is deteriorated
Since the total amount of gas molecules that can be adsorbed, that is, a part of nitrogen molecules and oxygen molecules, is reduced even if the extraction time is shortened, the adsorption tank 1 is not adsorbed by the adsorbents 1A and 2A and is in a gas state. , 2 increases the number of oxygen molecules present, and the product gas pressure can be maintained at 5 kgf / cm ² or more even if the take-out time is shortened.

In the above embodiment, a pair of adsorption tanks 1 and 2 are used.
However, it is needless to say that the invention can be applied to an apparatus having two or more adsorption tanks.

Further, in the above embodiment, each adsorption tank is configured to adsorb nitrogen molecules, but it is needless to say that it can be applied to a configuration in which each adsorption tank adsorbs other gas molecules (for example, a nitrogen generator, etc.). Is.

[0054]

As described above, according to the invention of claim 1,
Even if the concentration of the product gas taken out of the adsorption tank by the air supply time changing means falls below a predetermined value, the compressed air supply time to the adsorption tank can be shortened to return the product gas concentration to a predetermined value or higher. Since the product gas having the specified concentration can be generated without exchanging the agent, the usable time of the adsorbent can be extended and the adsorbent can be effectively used.

Further, according to the invention of claim 2, in addition to the above effects, it is possible to replace the adsorbent before it becomes unusable by notifying that the replacement time of the adsorbent is reached by the replacement time notification means. Therefore, it is possible to prevent the supply of the product gas from being suddenly stopped during operation and to continue the stable supply of the product gas to the downstream side.

[Brief description of 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 process drawing for explaining each process of oxygen generation.

FIG. 3 is a process drawing showing one cycle of each process.

FIG. 4 is a diagram showing a pressure change in each step of an adsorption tank and a product tank.

5 is a diagram showing the relationship between the take-out time and the change in pressure of the product tank 20. FIG.

FIG. 6 is a diagram showing the relationship between the take-out time and the oxygen concentration.

FIG. 7 is a flowchart showing processing executed by the control device.

[Explanation of symbols]

 1, 2 Adsorption tank 1A, 2A Adsorbent 3 Compressor 8, 9 Air supply valve 13, 14 Exhaust valve 18, 19 Extraction valve 20 Product tank 23 Pressure equalizing valve 26 Pressure sensor 27 Oxygen concentration sensor 28 Control device 28A Air Supply time changing means 28B Replacement time informing means

Claims (2)

[Claims] 1. A structure for supplying compressed air to an adsorption tank filled with an adsorbent to increase the pressure inside the adsorption tank, and taking out a product gas generated by the adsorbent in the adsorption tank from the adsorption tank. In the gas separation device, when the concentration of the product gas taken out from the adsorption tank becomes equal to or lower than a predetermined value, air supply time changing means for shortening the compressed air supply time to the adsorption tank is provided. Characteristic gas separation device. 2. A structure is provided in which compressed air is supplied to an adsorption tank filled with an adsorbent to increase the pressure inside the adsorption tank, and a product gas generated by the adsorbent in the adsorption tank is taken out from the adsorption tank. In the gas separation device, the air supply time changing means for shortening the compressed air supply time to the adsorption tank when the concentration of the product gas taken out from the adsorption tank is below a predetermined value, and the air supply time changing means. When the compressed air supply time is shortened by the above, a gas separation device comprising: a replacement timing notification means for reporting that it is time to replace the adsorbent.