JP2910776B2 - High pressure gas production equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure gas producing apparatus, and more particularly to a high-pressure gas producing apparatus configured to increase the pressure of a product gas while maintaining a predetermined concentration.

2. Description of the Related Art There has been known a PSA (Pressure Swing Adsorption) type gas separation apparatus that separates air into nitrogen and oxygen by using an adsorbent made of molecular carbon and takes out one of them as a product gas.

As research on food preservation progresses, it has been confirmed that nitrogen gas is effective for long-term preservation of dry matter and maintenance of freshness of fresh food, and the demand for nitrogen generators is increasing. In particular, PSA-type nitrogen generators are widely used because they are easy to handle and safe, and have the advantage of preventing impurities from intervening in the manufacturing process.

In the above PSA type nitrogen generator, an adsorption step of introducing compressed air into an adsorption tank filled with an adsorbent and increasing the pressure,
The desorption step of releasing the inside of the adsorption tank to the atmosphere or depressurizing with a vacuum pump is repeated.In the adsorption step, oxygen molecules are adsorbed by the adsorbent in the adsorption tank to take out nitrogen, while in the desorption step, the adsorbed oxygen The molecules are desorbed and prepared for the next adsorption step. The nitrogen gas, which is a product gas, is taken out with the pressure inside the adsorption tank being increased, so that the generated nitrogen gas is intermittent and has a large pressure change. For this reason, when nitrogen gas is used continuously at a constant pressure (low pressure, for example, 4 kgf / cm ²⁾ , a product tank is provided on the take-out side, and nitrogen gas is stored in the product tank. In the gas separation device, a concentration meter for measuring the nitrogen concentration in the product tank was provided, and when the nitrogen concentration became equal to or higher than a predetermined value from the start of the device, the take-out valve was opened to supply the product gas.

Problems to be Solved by the Invention However, in a facility that consumes a large amount of nitrogen at a time, such as a large-scale food storage facility, a device that stores a large amount of nitrogen gas has been demanded. However, as before, about 4kgf
If it is attempted to store the product gas at about / cm ² , the product tank becomes large and a larger installation space is required. Therefore, increasing the pressure of the product gas (for example, 9 to 10 kgf / cm ² ) has been considered as a means for increasing the storage amount of the product gas without increasing the size of the product tank.

To increase the pressure in the product tank, the pressure supplied to the adsorption tank may be increased. However, when the supply pressure into the adsorption tank increases as described above, the pressure in the adsorption tank increases,
The pressure change due to the pressure lowering operation becomes severe, the crushing ratio of the adsorbent increases, and the nitrogen generation efficiency of the apparatus decreases.

Also, since the compressed raw material gas is compressed at a stretch from atmospheric pressure to high pressure, the compressed raw material gas becomes high temperature and expands, but when compressed air is supplied to the adsorption tank, the temperature gradually decreases, the pressure decreases, and the compression efficiency decreases. I will.

Therefore, it has been considered to further increase the pressure of the product gas stored in the product tank by using a conventional gas separation device to increase the pressure. However, if the product gas in the product tank is taken out and continuously pressurized, the pressure in the product tank will decrease rapidly, and furthermore, the concentration of the product gas will be significantly reduced, and it will take considerable time to return to the predetermined pressure. Such a problem arises.

Also, if pressurization to the high-pressure tank is continued without adjusting the extraction flow rate from the product tank, not only will energy be wasted, but the used gas flow rate will not be stable, and the used gas flow rate must be changed along with the pressure fluctuation. The problem that adjustment is troublesome arises.

Therefore, an object of the present invention is to provide a high-pressure gas producing apparatus that solves the above-mentioned problems.

Means for Solving the Problems The present invention provides a product gas generator for supplying a compressed gas to an adsorption tank filled with an adsorbent to generate a product gas, and removing the product gas generated by the product gas generator. A flow control valve for adjusting a flow rate, a pressurizing means for pressurizing a product gas discharged from the flow control valve, a high-pressure tank for storing a product gas pressurized by the pressurizing means, and the high-pressure tank Pressure monitoring control means for operating the pressurizing means when the pressure of the high-pressure tank falls below a predetermined pressure, and monitoring the concentration of the product gas, wherein the product gas has a predetermined concentration. And flow rate monitoring and control means for changing the valve opening of the flow rate regulating valve so as to keep it.

When the pressure of the high-pressure tank falls below a predetermined pressure, the pressurizing means operates to change the valve opening of the flow control valve so that the concentration of the product gas becomes the predetermined concentration. The product gas is stored in the high-pressure tank, and a predetermined concentration of the product gas can be stably supplied to the downstream side.

Embodiment FIG. 1 shows an embodiment of a high-pressure gas producing apparatus according to the present invention.

In the figure, reference numerals 1 and 2 denote first and second adsorption tanks, and the adsorption tanks 1 and 2 are filled with adsorbents 1A and 2A made of molecular sieve carbon, respectively.

Reference numeral 3 denotes a compressor serving as a compressed air supply source, which compresses air to about 6 to 7 kgf / cm ² and accumulates the pressure in the raw material tank 4. The compressed air from the tank 4 is dehumidified by the refrigeration dryer 5 and then supplied alternately to the adsorption tanks 1 and 2 via the pipes 6 and 7, respectively. Are provided with air supply valves 8 and 9 each comprising an electromagnetic valve.

Reference numerals 10 and 11 denote pipes for discharging gas from the adsorption tanks 1 and 2 at the time of desorption. The pipes are connected to the common discharge pipe 12 respectively.
Discharges exhaust gas. In the middle of the pipes 10, 11, there are provided gas discharge valves 13, 14, which are electromagnetic valves for alternately discharging the desorbed exhaust gas in the adsorption tanks 1, 2 every half cycle.

15 and 16 are extraction pipes connected to the outlet side of the adsorption tanks 1 and 2 for extracting nitrogen generated in the adsorption tanks 1 and 2, respectively, and 17 is a pipe 1 for each of the pipes.
In the take-out pipes connected to 5, 16 in the middle of each of the pipes 15, 16 take-out valves 18, 19 consisting of solenoid valves that open alternately under control described later only for a half cycle are provided. I have. Further, the take-out pipe 17 is connected to the product tank 20.

This product tank 20 is about 5 to 6
It is an auxiliary tank for temporarily storing about kgf / cm ² of product gas.

21 is a pipe connecting the outlet sides of the adsorption tanks 1 and 2, and 22 is a pipe 21
A pressure equalizing valve consisting of a solenoid valve provided in the middle of the tank.The pressure equalizing 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 1 and 2. To

Reference numeral 23 denotes a discharge pipe connected to the product tank 20, and a pressure reducing valve 23a and a product gas discharge valve 24 are provided on the way.

Reference numeral 25 denotes a concentration meter comprising an oxygen sensor, which detects the oxygen concentration of the gas stored in the product tank 20. Also oxygen sensor
The oxygen concentration detection signal from 25 is input to a control circuit 27 described later. The concentration meter 25 is a magnetic oxygen sensor using the paramagnetism of oxygen molecules, and an electromagnetic oxygen sensor using a current that causes an oxidation-reduction reaction at an electrode when oxygen enters the electromagnetic liquid through the permeable membrane. A zirconia oxygen sensor or the like is used in which electrodes are provided on the inner and outer surfaces of the zirconia porcelain and an electromotive force is generated by the oxygen concentration.

Reference numeral 26 denotes a concentration setting switch for setting the purity of nitrogen extracted from the extraction pipe 23, that is, the concentration of oxygen, which is set according to the concentration of nitrogen gas to be extracted from the product tank 20.

The control circuit 27 is a valve control means constituted by, for example, a microcomputer or the like.
5. Concentration setting switch 26 is connected, and responds to each step of pressurization (,), take-out (,), equalization (,) shown in FIGS. Then, the opening and closing of the air supply valves 8 and 9, the gas discharge valves 13 and 14, the discharge valves 18 and 19, the equalizing valve 22, the product gas discharge valve 24, and the like are controlled.

Each solenoid valve controlled to be opened and closed by the control circuit 27 is opened when excited by the supply of a valve opening signal, and closed by a spring force when not excited.

In FIG. 1, a portion surrounded by a dashed line constitutes a product gas generator 28 that generates product gas.

Reference numeral 29 denotes a flow control valve for controlling the flow rate of the product gas generated by the product gas generator 28. Also, product tank 20
The product gas stored in the inside is supplied through a pipe 30 to a flow control valve 29.
The flow rate is adjusted to a flow rate corresponding to the concentration of the product gas as described later, and is supplied to a booster (pressurizing means) 32 via a pipe 31. The booster 32 includes a high-pressure compressor, and is configured to operate using air pressure as a power source.
Since the details of the booster 32 are well known, they are omitted here.

High pressure by booster 32 (for example, about 9 to 10 kgf / cm ² )
The product gas compressed to the high pressure tank via pipe 33
Supplied to 34. The high-pressure tank 34 is provided with a pressure gauge 35 for monitoring the pressure of the product gas stored in the tank. Reference numeral 36 denotes an extraction pipe for extracting a high-pressure product gas from the high-pressure tank 34, and a high-pressure extraction valve 37 formed of a solenoid valve is provided.

The control circuit 27 monitors the pressure of the high-pressure tank 34, and when the pressure of the high-pressure tank 34 falls below a predetermined pressure (8 kgf / cm ² in this embodiment) based on an output signal from the pressure gauge 35. Pressure monitoring control means 27A for operating the booster 32,
The flow rate that monitors the concentration of the product gas and changes the valve opening of the flow control valve 29 based on the output signal from the concentration meter 25 so that the product gas in the product tank 20 maintains a predetermined concentration (for example, 99.9% nitrogen). Monitoring control means 27B.

Here, the operation of the nitrogen generation cycle of the high-pressure gas producing apparatus will be described.

First, the basic operation of nitrogen generation will be described with reference to FIG. 2 and FIG.

Now, when the high-pressure gas production apparatus is started, nitrogen is generated under the control of a microcomputer (not shown).

First, as shown in FIG. 3, the operation of, is performed. In FIG. 2, the air supply valve 9 and the gas discharge stool 13 are opened. The compressed gas stored in the raw material tank 4 is supplied to the second adsorption tank 2, and the second adsorption tank 2 is in a pressurized state. Therefore, oxygen is adsorbed by the adsorbent 2A. On the other hand, the first adsorption tank 1 is in a decompressed state, indicating a state in which the adsorbed oxygen is desorbed and discharged.

Next, FIG. 2 shows an air supply valve 9 and a gas discharge valve.
In addition to 13, the take-out valve 19 is newly opened, and the second adsorption tank 2 is opened.
2 shows a state in which nitrogen gas is taken out from the inside. At this time, the first adsorption tank 1 remains in a reduced pressure state.

Next, FIG. 2 shows a pressure equalizing operation.
9, the air supply valve 9 and the gas discharge valve 13 are opened, and the pressure equalizing valve 22 is opened. As a result, the nitrogen gas remaining in the second adsorption tank 2 is collected in the first adsorption tank 1,
Each of the adsorption tanks 1 and 2 has a uniform pressure. The equalizing operation is usually performed for 1 to 3 seconds.

As a result, the first half of one cycle is completed, and the air supply valve 8 and the gas discharge valve 14 are completed.
, The second half cycle shown in FIG. 2B is repeated as shown in FIG. 3 (B). Thus, nitrogen 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. After a while, the purity of the generated nitrogen gas is stabilized.

In this way, the product gas compressed to about 4 kgf / cm is stored in the product tank 20.

However, when the product gas is alternately supplied from the adsorption tanks 1 and 2 to the product tank 20 as described above, the pressure in the product tank 20 becomes the peak value (1) of the adsorption tanks 1 and 2 as shown in FIG. (Indicated by a dashed-dotted line and a two-dotted dashed line) vary as shown by the solid line. In order to stabilize the supply pressure of the product gas so that such pressure fluctuation does not affect the downstream side, the extraction pressure is reduced to about 4 kgf / cm ² by the pressure reducing valve 23a.

Then, the product gas extracted from the product gas generator 28 passes through the flow control valve 27, reaches the booster 32, and the booster 32.
Pressurized by 32. When the product gas pressurized by the booster 32 is supplied to the high-pressure tank 34, the relationship between the pressure of the high-pressure tank 34 and the flow rate of the product gas is as shown in FIG. If the flow rate of the product gas changes linearly in inverse proportion to the pressure of the high-pressure tank 34, the pressure in the high-pressure tank 34 always fluctuates when extracting product gas. The flow rate must be adjusted according to the pressure change, and a predetermined specified flow rate cannot be maintained. Therefore, if the flow rate is adjusted to Q ₂ and Q ₃ by changing the valve opening of the flow control valve 29, a predetermined specified flow rate can be maintained even if there is a pressure fluctuation as shown in the II and III diagrams in FIG. . But,
When the pressure in the high-pressure tank 34 drops sharply and the pressure in the high-pressure tank 34 becomes significantly lower than the lower limit of the specified pressure, it takes a long time to raise the pressure in the high-pressure tank 34 to the upper limit of the specified pressure. It takes time.

Therefore, in this embodiment, the limiting circuit 27 executes the processing shown in FIG. 6 by the action of the pressure monitoring control means 27A and the flow rate monitoring control means 27B. That is, the control circuit 27 controls the flow regulating valve 29 and the booster 32 while monitoring the pressure of the high-pressure tank 34 and the oxygen concentration in the product tank 20 to increase the pressure of the product gas in an optimal manner as described later. .

First, the control circuit 27 comes to Figure 6 in step S1 (hereinafter abbreviated to "step") in the oxygen concentration of the product tank 20 (which is set by the N ₂ 99.9% advance concentration setting switch 26) greater than or equal to a prescribed value Activate the booster 32 in S2. The booster 32 pressurizes the product gas in the product tank 20 and supplies the high-pressure product gas to the high-pressure tank 34. The activation of the booster 32 is continued until the pressure of the high-pressure tank 34 reaches the upper limit of the specified pressure (in this embodiment, 10 kgf / cm ² ). That is, S
When the pressure of the high-pressure tank 34 reaches the upper limit value of the limited pressure in 3, the process proceeds to S4, where the booster 32 is stopped, and then the high-pressure discharge valve 37 is opened to start discharging the high-pressure product gas.

Then, when the high-pressure product gas is taken out, the pressure in the high-pressure tank 34 starts to drop and the lower limit of the specified pressure (8 kgf in this embodiment)
/ cm ² ).

When the lower limit of the specified pressure is reached in S5, the process proceeds to S6, where the booster 32 is started again.

At S7, the oxygen concentration in the product tank 20 is monitored, and the oxygen concentration is the reference concentration (N ₂ 99% in this embodiment).
If so, the process proceeds to S8, where the pressure in the high-pressure tank 34 is monitored. This pressure is equal to the reference pressure (9 kgf / c in this embodiment).
m ²⁾ while falling below in the open further valve opening degree of the flow rate adjusting valve 29 moves to S9, adjust the flow rate Q _2. Also, reducing the flow restriction of the valve opening degree of the flow regulating valve 29 moves to S10 when the oxygen concentration in the product tank 20 has not reached the reference concentration Q ₃ at S7. Also in S8, when the pressure in the high-pressure tank 34 is equal to or higher than the reference pressure, the process proceeds to S10, and the flow control valve 29 is throttled.

In the next S11, when the pressure in the high-pressure tank 34 has not reached the upper limit value of the specified pressure, the process returns to S7, and the processes of S7 to S10 are repeated. When the pressure in the high-pressure tank 34 reaches the upper limit of the specified pressure in S11, the process proceeds to S12, where the booster 32 is stopped, and the process returns to S5. Then, when the high-pressure product gas is taken out from the high-pressure tank 34 and the pressure in the high-pressure tank 34 decreases, the processing of S5 to S12 is repeatedly executed again.

As described above, the booster 32 is operated by adjusting the valve opening of the flow control valve 29 while monitoring the oxygen concentration in the product tank 20 and the magnitude of the pressure in the high-pressure tank 34. When the oxygen concentration of the gas does not reach the reference concentration, the flow rate will increase and the product tank 20
Prevents a sudden decrease in product gas concentration in the tank, and a high pressure tank
Although the pressure in 34 has reached the upper limit of the specified pressure, the booster
Prevent 32 from operating more than necessary. Therefore, the booster 32 is efficiently driven according to the magnitude of the pressure in the high-pressure tank 34.

The reference concentration of the product tank 20 and the high pressure tank 34
Can be set to desired values.

In the above embodiment, the apparatus for increasing the pressure of nitrogen gas has been described as an example. However, it is needless to say that the present invention can be applied to the case of increasing the pressure of oxygen gas other than nitrogen, for example.

Effect of the Invention As described above, the high-pressure gas production apparatus according to the present invention adjusts the flow rate while monitoring the concentration of the product gas generated by the product gas generation apparatus to increase the pressure of the product gas. Can be boosted in a short time while maintaining
High pressure product gas can be supplied stably. Even if the product gas in the high-pressure tank is used suddenly, it is possible to efficiently pressurize the product gas while maintaining the specified concentration.
Furthermore, it has a feature that it functions effectively and can supply high-pressure product gas even when a large amount of high-pressure product gas is continuously used in a short time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a high-pressure gas producing apparatus according to the present invention,
2 and 3 are diagrams for explaining a product gas generation process, respectively. FIG. 4 is a diagram for explaining pressure fluctuations of an adsorption tank and a product tank. FIG. FIG. 6 is a flow chart for explaining the processing executed by the control circuit. 1,2 ... Adsorption tank, 3 ... Compressor, 4 ... Raw material tank, 20 ... Product tank, 24 ... Product gas outlet valve, 25 ...
Densitometer, 26: density setting switch, 27: control circuit, 27
A: Pressure monitoring control means, 27B ... Flow monitoring control means, 28
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Claims (1)

(57) [Claims] 1. A product gas generator for supplying a compressed gas to an adsorption tank filled with an adsorbent to generate a product gas, and a flow rate adjusting device for adjusting a removal flow rate of the product gas generated by the product gas generator. A valve, a pressurizing means for pressurizing the product gas discharged from the flow control valve, a high-pressure tank for storing the product gas pressurized by the pressurizing means, and monitoring the pressure of the high-pressure tank, Pressure monitoring control means for operating the pressurizing means when the pressure of the high-pressure tank falls below a predetermined pressure; anda flow regulating valve for monitoring the concentration of the product gas and maintaining the product gas at a predetermined concentration. And a flow rate monitoring control means for changing a valve opening degree of the high pressure gas producing apparatus.