JP5518503B2 - High pressure and high purity nitrogen gas supply device and supply method - Google Patents

Description

  The present invention relates to a high-pressure and high-purity nitrogen gas supply device and supply method.

  Conventionally, in the laser processing machine field, high-pressure and high-purity nitrogen gas has been required as an assist gas for non-oxidative cutting of a stainless steel plate or an optical path purge gas.

High-purity nitrogen gas is relatively reduced by a pressure fluctuation adsorption gas separation apparatus (hereinafter abbreviated as PSA apparatus) that separates a raw material mixed gas by a pressure swing adsorption (hereinafter abbreviated as PSA) method. It can be supplied easily.
The PSA apparatus has two or more adsorption cylinders filled with an adsorbent, and generates high-purity nitrogen gas as a product gas while alternately performing an adsorption process and a regeneration process. Here, when the adsorption cylinder is switched, the pressure, flow rate and purity of the generated nitrogen gas vary. For this reason, in order to continuously supply nitrogen gas while alleviating these fluctuations, it is common to provide a buffer tank inside the PSA apparatus.

  By the way, in general, it is difficult to produce high-purity nitrogen gas of 99.999% (residual oxygen concentration of 10 ppm or less) by the PSA method alone, and it is necessary to remove oxygen components. Therefore, conventionally, high-purity nitrogen gas has been produced using a purifier that combines residual oxygen with hydrogen to reduce the residual oxygen concentration.

  In addition, when water is produced by reacting remaining oxygen with hydrogen, as a removal device for removing water present in nitrogen gas, for example, a membrane-type dehumidifying device described in Patent Document 1 or Patent Document 2 is known.

  However, the system of a high-purity nitrogen gas generator is complicated by using a refining device filled with a nickel reactant, a palladium catalyst, etc., and a membrane dehumidifying device and a PSA dehumidifying device described in Patent Documents 1 and 2. As a result, it becomes a large-scale facility and consumes power. In addition, there is a problem that the gas production cost with a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) becomes expensive.

  Moreover, when using the film | membrane type dehumidification apparatus and PSA type dehumidification apparatus of patent document 1 and 2, it is necessary to discharge | emit a part of nitrogen gas to air | atmosphere when removing a water | moisture content functionally. Therefore, only about 70 to 80% of the nitrogen gas produced with respect to the supplied air can be recovered, and there is a problem that the amount of nitrogen purity 99.999% (residual oxygen concentration of 10 ppm or less) that can be produced is small. .

  By the way, when supplying high purity nitrogen gas to the laser processing machine, the required pressure is 2.0 to 3.5 MPa. However, since the pressure of the raw material air introduced into the PSA type nitrogen gas generator is in the range of 0.7 to 1.0 MPa in gauge pressure, the discharge pressure of the PSA type nitrogen gas generator is 1.0 MPa or less. Therefore, there is a problem that the specification of the supply pressure to the laser beam machine described above is not satisfied only by the discharge pressure of a general PSA type nitrogen gas generator. Moreover, in order to produce a high pressure, it is possible to cope with the high pressure of the raw material air with a booster, but it is necessary to make all the equipment used high-pressure specifications, leading to high equipment costs. Therefore, it is not preferable.

  Therefore, in order to supply high-pressure and high-purity nitrogen gas at low cost, a method of boosting the high-purity nitrogen gas supplied from the PSA-type nitrogen gas generator to the required pressure using a booster is considered. It is done.

JP 2007-277028 A JP 2005-320221 A

  However, in the method of boosting nitrogen gas using a booster with high-purity nitrogen gas supplied from the PSA type nitrogen gas generator, when the flow rate of nitrogen gas discharged from the booster increases, the inlet side of the booster There was a risk that the pressure on the (intake side) would drop, and the booster would stop due to the safety mechanism, making it impossible to continuously supply nitrogen gas. Further, if the supply amount of nitrogen gas from the PSA nitrogen gas generator is increased in order to prevent a pressure drop on the inlet side of the booster, the purity of the nitrogen gas supplied from the PSA nitrogen gas generator is disturbed and required. There was a possibility that the nitrogen gas of the purity which was made could not be supplied.

  Therefore, in the nitrogen gas supply apparatus 101 shown in FIG. 5, a method of enlarging the buffer tank 108 provided in the PSA type nitrogen gas generation apparatus 102 in order to prevent a pressure drop on the inlet side 103 a of the booster 103, This shows a method of newly installing a tank 140 for storing nitrogen gas between the gas generator 102 and the booster 103. However, the method shown in the nitrogen gas supply apparatus 101 shown in FIG. 5 has a problem that the apparatus becomes large and the initial cost becomes expensive.

  The present invention has been made in view of the above circumstances, and provides a high-pressure and high-purity nitrogen gas supply device and supply method with a simple configuration and method without incurring an increase in size and cost of the device. The purpose is to provide.

  As a result of intensive studies by the present inventors, from the outlet side (discharge side) of the booster to the gas supply path provided with the booster that boosts the high purity nitrogen gas generated by the PSA type nitrogen gas generator. A return path that can send nitrogen gas to the inlet side (suction side) is provided, and when the pressure on the inlet side of the booster decreases, nitrogen gas is supplied from the outlet side of the booster to the inlet side using the return path. The present invention was completed by finding that the pressure on the inlet side of the booster can be recovered by supplying.

Therefore, the invention of the present application has the following configuration.
The invention according to claim 1 is a pressure fluctuation adsorption type nitrogen gas generator that generates high-purity nitrogen gas from raw material air in the gas supply path, and the nitrogen gas produced by the pressure fluctuation adsorption type nitrogen gas generator. A booster that boosts the pressure, a storage tank that stores the nitrogen gas boosted by the booster, and a means for decompressing and supplying the gas in the storage tank,
The high-pressure and high-purity nitrogen gas supply device is characterized in that a return path for returning the nitrogen gas from the outlet side to the inlet side of the booster is provided in the gas supply path.

  The invention according to claim 2 is the high-pressure and high-purity nitrogen gas supply device according to claim 1, wherein a decompression means is provided in the return path.

In the invention according to claim 3, the pressure fluctuation adsorption type nitrogen gas generator includes two or more adsorption cylinders filled with molecular sieve carbon as an adsorbent,
The pressure of the raw material air to be introduced is in the range of 0.9 to 1.0 MPa in gauge pressure,
The ratio of the raw material air amount introduced per unit time and the adsorbent filling amount is in the range of 420 to 510 hr ⁻¹ ;
The production amount of the high purity nitrogen gas per ton of the adsorbent filled in the pressure fluctuation adsorption type nitrogen gas generator is 68 Nm ³ / hr · ton or less. The high-pressure and high-purity nitrogen gas supply device described in 1.

In the invention according to claim 4, the molecular sieve carbon has an oxygen adsorption rate constant of 6.5 × 10 ⁻² S ⁻¹ or more, an oxygen adsorption rate constant K (O ₂ ), and a nitrogen adsorption rate constant. The ratio α to K (N ₂ ) is 35 or more,
The adsorption rate characteristic has a relationship of the following formula (1) between the time t ₉₅ required to adsorb the oxygen equilibrium adsorption amount 95% and the time t ₅₀ required to adsorb the oxygen equilibrium adsorption amount 50%. The high-pressure and high-purity nitrogen gas supply device according to claim 3.
(T ₉₅ / t ₅₀ ) <0.4 (α-24) (1)

  The invention according to claim 5 is characterized in that the pressure fluctuation adsorption type nitrogen gas generator has a primary storage tank for storing the generated high purity nitrogen gas. The high-pressure and high-purity nitrogen gas supply device described in 1.

According to a sixth aspect of the present invention, there is provided the adsorption tower according to the pressure fluctuation adsorption type gas separation method in which the raw material air is supplied to two or more adsorption towers, the adsorption step of pressurizing the adsorption tower, and the regeneration step of depressurizing the adsorption tower are sequentially performed. Separating the oxygen component and the nitrogen component with an adsorbent filled therein to produce high-purity nitrogen gas;
Boosting the generated nitrogen gas with a booster;
Storing the pressurized nitrogen gas;
A step of reducing the pressure of the stored nitrogen gas and supplying the nitrogen gas,
When the pressure of the nitrogen gas at the inlet side of the booster decreases, the nitrogen gas is returned from the outlet side of the booster to the inlet side. is there.

  In the invention according to claim 7, when the pressure of the nitrogen gas on the inlet side of the booster is reduced, the pressure is increased when returning the nitrogen gas from the outlet side of the booster to the inlet side. 7. The high-pressure and high-purity nitrogen gas supply method according to claim 6, wherein nitrogen gas is supplied under reduced pressure.

According to the high-pressure and high-purity nitrogen gas supply device and supply method of the present invention, a general pressure fluctuation is provided because a pressure booster that boosts the nitrogen gas generated by the pressure fluctuation adsorption-type nitrogen gas generator is provided. It becomes possible to supply high-pressure nitrogen gas using an adsorption-type nitrogen gas generator.
Also, a return path for returning the nitrogen gas from the outlet side to the inlet side of the booster to a gas supply path provided with a booster that boosts the high purity nitrogen gas generated by the pressure fluctuation adsorption type nitrogen gas generator When the pressure on the inlet side of the booster decreases, nitrogen gas can be returned from the outlet side of the booster to the inlet side. Thereby, the pressure on the inlet side of the booster can be recovered without excessively supplying nitrogen gas from the pressure fluctuation adsorption type nitrogen gas generator to the booster. Therefore, it is possible to supply high-purity nitrogen gas while exhibiting the performance of the pressure fluctuation adsorption type nitrogen gas generator.
In this way, even when the pressure on the inlet side of the booster is reduced, the pressure on the inlet side can be recovered using the return path, so that it is provided inside the pressure fluctuation adsorption type nitrogen gas generator. It is not necessary to enlarge the storage tank, or to install a separate tank for storing nitrogen gas between the pressure fluctuation adsorption type nitrogen gas generator and the booster. Thereby, a general pressure fluctuation adsorption type nitrogen gas generator can be used as it is. Therefore, it is possible to provide a high-pressure and high-purity nitrogen gas supply apparatus and supply method with a simple configuration and method without causing an increase in size and cost of the apparatus.

  In addition, according to the high pressure and high purity nitrogen gas supply device and supply method of the present invention, since the storage tank for storing the pressurized nitrogen gas and the valve for decompressing the nitrogen gas are provided, the nitrogen gas is transferred from the storage tank to the use device. The pressure of the supply gas can be controlled when supplying the gas, and a large amount of high-pressure and high-purity nitrogen gas can be temporarily supplied.

FIG. 1 is a system diagram showing a high-pressure and high-purity nitrogen gas supply apparatus according to an embodiment to which the present invention is applied. 2A to 2F are schematic views for explaining each process of the PSA type nitrogen gas generator constituting the present invention. FIG. 3 is a graph for explaining an embodiment of the present invention. FIG. 4 is a graph for explaining an embodiment of the present invention. FIG. 5 is a system diagram showing a conventional high-pressure and high-purity nitrogen gas supply apparatus.

Hereinafter, a high-pressure and high-purity nitrogen gas supply apparatus according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings together with a high-pressure and high-purity nitrogen gas supply method using the apparatus.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

  FIG. 1 is a system diagram showing a high-pressure and high-purity nitrogen gas supply apparatus according to an embodiment to which the present invention is applied. As shown in FIG. 1, a high-pressure and high-purity nitrogen gas supply device (hereinafter simply referred to as “supply device”) 1 supplies high-purity nitrogen gas from raw material air to a nitrogen gas supply path (gas supply path) L1. PSA type nitrogen gas generator (pressure fluctuation adsorption type nitrogen gas generator) 2 to be generated, a booster 3 that boosts the nitrogen gas generated by the PSA nitrogen gas generator 2, and nitrogen that has been boosted by the booster 3 A storage tank 4 for storing gas and a valve 26 for reducing the pressure of nitrogen gas stored in the storage tank 4 are schematically configured. The gas supply path L1 is provided with a return path L2 for returning nitrogen gas from the outlet side 3b of the booster 3 to the inlet side 3a.

  As shown in FIG. 1, the PSA type nitrogen gas generator 2 includes an air compressor 5 for compressing raw material air, an air storage tank 6 for storing raw material air, and two adsorption cylinders 7A and 7B filled with an adsorbent. And a buffer tank (primary storage tank) 8 that stores the generated high-purity nitrogen gas. More specifically, the PSA-type nitrogen gas generator 2 includes a first inlet valve 9a, a second inlet valve 9b, a first exhaust valve 10a, a second exhaust valve that are automatically opened and closed by a switching program for each process of the adsorption towers 7A and 7B. An exhaust valve 10b, a purge valve 11, an upper pressure equalizing valve 12, a lower pressure equalizing valve 13, a first check valve 14a and a second check valve 14b, and a first mass flow controller 15 for adjusting the flow rate of raw material air to a predetermined flow rate; A second mass flow controller 16 for adjusting the supply amount of the high purity nitrogen gas to a predetermined flow rate, a flow rate adjusting valve 17 for adjusting the flow rate of the purge gas to a predetermined flow rate, an inlet side pressure adjusting valve 18a and an outlet side pressure adjusting valve 18b, , Pressure gauges 19, 20, and 21 and an oxygen concentration meter 22.

  This PSA-type nitrogen gas generator 2 introduces raw air pressurized to an appropriate pressure into two adsorption cylinders 7A and 7B each filled with an adsorbent, and pressurizes the inside of the cylinder to a predetermined pressure. Process, an adsorption process that preferentially adsorbs adsorbed oxygen to the adsorbent, collects nitrogen gas that is difficult to adsorb and sends it to the buffer tank 8 (product extraction process), and removes the nitrogen remaining in one adsorption cylinder. Depressurization and pressure equalization process to send to the other adsorption cylinder, Regeneration process to desorb the oxygen adsorbed by the adsorbent that lowers the pressure by releasing the adsorption cylinder to the atmosphere, and nitrogen from the other adsorption cylinder Each step of the pressurization and pressure equalization step for accepting the minute is alternately repeated by the two adsorption cylinders 7A and 7B, thereby separating oxygen and nitrogen in the air and continuously supplying high-purity nitrogen gas. To supply.

  As the air compressor 5, it is preferable to use an air compressor in which the maximum discharge pressure of the raw material air introduced into the adsorption cylinders 7A and 7B is 0.9 to 1.0 MPa. This is because, generally, in the PSA method, nitrogen gas having a low oxygen concentration can be obtained when the pressurization pressure is high. In addition, the air compressor 5 is selected because the discharge air amount and the motor output value are important factors, and a suitable air compressor that satisfies the required raw material air amount and considers reduction of power consumption is selected. It is preferable.

The adsorbent of the present embodiment has an oxygen adsorption rate constant of 6.5 × 10 ⁻² S ⁻¹ or more, and a separation ratio α between oxygen and nitrogen (oxygen adsorption rate constant K (O ₂ )) The ratio of nitrogen adsorption rate constant K (N ₂ )) K (O ₂ ) / K (N ₂ ) is 35 or more, and the adsorption rate characteristic takes the time required to adsorb an oxygen equilibrium adsorption amount of 95% the t ₉₅ and 50% oxygen equilibrium adsorption amount in relation to the time t ₅₀ required for adsorption using molecular sieves carbon that satisfies the following relationship. Accordingly, high-purity nitrogen gas having a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) can be supplied on condition that various other conditions are satisfied.
(T ₉₅ / t ₅₀ ) <0.4 (α-24), where α> 35

  The buffer tank 8 is provided to temporarily store nitrogen gas obtained from the adsorption cylinders 7A and 7B. By storing the nitrogen gas generated by the PSA-type nitrogen gas generator 2 in the buffer tank 8 and supplying the nitrogen gas to the booster 3 from the buffer tank 8, the purity of the nitrogen gas sent to the booster 3 can be stabilized. . Thus, high-purity nitrogen gas having a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) can be stably supplied on condition that various other conditions are satisfied. The capacity of the buffer tank 8 is not particularly limited, but preferably has a capacity that does not cause excessive suction of the booster 3 frequently.

Further, on-off valves may be used in place of the first and second check valves 14a and 14b. Furthermore, an orifice may be used in place of the purge valve 11 and the flow rate adjusting valve 17.
In the present embodiment, a configuration in which two adsorption cylinders are provided is illustrated, but a multi-cylinder PSA apparatus having three or more cylinders may be used. Thereby, it is possible to reduce the size of the adsorption cylinder, in particular, to reduce the cylinder height and to stabilize the purity of the generated nitrogen gas and the pressure in the buffer tank 8.

  As shown in FIG. 1, the booster 3 is provided for boosting high-purity nitrogen gas supplied from the PSA-type nitrogen gas generator 2. The booster 3 is not particularly limited, but the gas discharge pressure from the PSA-type nitrogen gas generator 2 is often 1.0 MPa or less and around 0.5 to 0.6 MPa. Those capable of increasing the pressure to ˜5.0 MPa are preferred.

  As shown in FIG. 1, the storage tank 4 is provided on the downstream side of the booster to store the nitrogen gas boosted by the booster 3. The storage tank 4 is provided with a pressure gauge 23 for measuring the pressure in the tank. Furthermore, a filter 24 for filtering impurities such as oil and dust is provided in the gas supply path L1 upstream of the storage tank 4. Furthermore, an oxygen concentration meter 25 for measuring the oxygen concentration in the storage tank 4 and 5 high-pressure high-purity nitrogen gas stored in the storage tank 4 are provided in the gas supply path L1 on the downstream side of the storage tank 4. A pressure reducing valve 26 capable of reducing the pressure to 0.0 MPa or less is provided. Thereby, it becomes possible to supply a large amount of gas temporarily while controlling the pressure of the high purity nitrogen gas in the storage tank 4. In addition, when the amount of gas supplied is small and can be covered by the stored gas in the storage tank 4, the power consumption can be reduced by stopping the air compressor 5, the PSA type nitrogen gas generator 2, and the booster 3 manually or with an interlocking system. Can be reduced.

  In the gas supply path L1 in the supply device 1 of the present embodiment, high-purity nitrogen gas of the booster 3 due to a decrease in gas discharge pressure from the PSA type nitrogen gas generator 2 (pressure on the inlet side 3a of the booster 3) is supplied. In order to prevent excessive suction, a return path L2 through which nitrogen gas can be returned from the outlet side 3b of the booster 3 to the inlet side 3a is provided. The return path L2 is provided with a pressure reducing valve 27 as pressure reducing means. As a result, the pressure of the nitrogen on the outlet side 3b boosted by the booster 3 can be reduced and returned to the inlet side 3a.

Next, a high-pressure and high-purity nitrogen gas supply method of the present embodiment using the supply device 1 will be described.
The high-pressure high-purity nitrogen gas supply method of the present embodiment (hereinafter simply referred to as “supply method”) includes a step of generating high-purity nitrogen gas (a step of generating high-purity nitrogen gas) and a step-up of the nitrogen gas. It is roughly configured to include a process (nitrogen gas boosting process), a nitrogen gas storing process (nitrogen gas storing process), and a nitrogen gas decompressing process (nitrogen gas supplying process). Yes. Hereinafter, each step will be described in detail.

(Production process of high purity nitrogen gas)
In the high-purity nitrogen gas production process, the adsorption air is supplied to two or more adsorption towers, the adsorption process for pressurizing the adsorption towers, and the regeneration process for depressurizing the adsorption towers in order, and the adsorption is performed by the pressure fluctuation adsorption gas separation method. The adsorbent packed in the tower separates the oxygen component and the nitrogen component to produce high purity nitrogen gas.
Specifically, the PSA type nitrogen gas generator 2 of this embodiment separates nitrogen in the air by repeating the steps shown in FIGS. 2A to 2F and collects nitrogen gas. FIG. 2 is a schematic diagram for explaining the flow of gas, and shows only the path through which the gas flows in the valve-open state in each step. Below, each process is demonstrated in order of a process, respectively.

  FIG. 2A shows a state in which the adsorption cylinder 7A is in the pressurizing process and the adsorption cylinder 7B is in the first half of the regeneration process, and the first inlet valve 9a of the adsorption cylinder 7A is opened, and a predetermined pressure is set in the adsorption cylinder 7A. The raw material air is introduced and the inside of the cylinder is pressurized. At this time, the purge valve 11 and the second exhaust valve 10b of the adsorption cylinder 7B are opened, and the flow rate of the nitrogen derived from the outlet of the adsorption cylinder 7A is adjusted by the flow rate adjustment valve 17, passes through the purge valve 11 and the adsorption cylinder 7B. The gas in the adsorption cylinder 7B is discharged from the outlet and purged in the cylinder.

  FIG. 2B shows a state in which the adsorption cylinder 7A performs the adsorption (product take-out) process and the adsorption cylinder 7B performs the latter half of the regeneration process. In this state, when the pressure in the adsorption cylinder 7A rises above the pressure in the buffer tank 8, the outlet gas of the adsorption cylinder 7A passes through the first check valve 14a and flows into the buffer tank 8. The outlet gas of the adsorption cylinder 7A is nitrogen concentrated to a predetermined oxygen content because oxygen is adsorbed by the adsorbent (molecular sieve carbon) filled in the cylinder. On the other hand, in the adsorption cylinder 7B, the in-cylinder gas is continuously released and purged.

  FIG. 2C shows a state in which the adsorption cylinder 7A is switched from the adsorption process to the pressure-reducing and equalizing process, and the adsorption cylinder 7B is switched from the regeneration process to the pressure-equalizing and equalizing process. In this state, the first inlet valve 9a of the adsorption cylinder 7A, the second exhaust valve 10b and the purge valve 11 of the adsorption cylinder 7B are closed, and the upper pressure equalization valve 12 and the lower pressure equalization valve 13 are opened. In this pressure equalization process, the nitrogen-rich gas in the adsorption cylinder 7A having a relatively high in-cylinder pressure after completion of the adsorption process is recovered in the adsorption cylinder 7B having the relatively low in-cylinder pressure after the regeneration process is completed. As a result, the suction cylinder 7A is depressurized and the suction cylinder 7B is pressurized.

  FIG. 2D shows a state in which the adsorption cylinder 7A is switched to the regeneration process and the adsorption cylinder 7B is switched to the pressurization process. In this state, the first exhaust valve 10a of the adsorption cylinder 7A is opened and the in-cylinder gas is released into the atmosphere, so that the oxygen adsorbed on the adsorbent is desorbed and released outside the cylinder. Further, the purge valve 11 is opened, and purge gas (nitrogen gas) from the adsorption cylinder 7B is introduced into the outlet of the adsorption cylinder 7A to further wash out oxygen. Further, in the adsorption cylinder 7B, the second inlet valve 9b is opened and the raw material air is introduced into the cylinder to be pressurized.

  FIG. 2E shows a state where the adsorption cylinder 7A continues the regeneration process and the adsorption cylinder 7B is switched from the pressurization process to the adsorption process. In this state, in the adsorption cylinder 7A, the introduction of the purge gas from the adsorption cylinder 7B and the gas discharge from the first exhaust valve 10a are continued. Further, when the in-cylinder pressure of the adsorption cylinder 7B is increased, the product nitrogen gas is collected from the adsorption cylinder 7B to the buffer tank 8 through the second check valve 14b.

  FIG. 2F shows a state in which the adsorption cylinder 7A is switched from the regeneration process to the pressure equalization process, and the adsorption cylinder 7B is switched from the adsorption process to the pressure reduction and pressure equalization process. In this state, the second inlet valve 9b of the adsorption cylinder 7B, the first exhaust valve 10a and the purge valve 11 of the adsorption cylinder 7A are closed, and both the pressure equalizing valves 12 and 13 are opened. In this pressure equalization process, the nitrogen-rich gas in the adsorption cylinder 7B that has completed the adsorption process is collected in the adsorption cylinder 7A that has completed the regeneration process.

  As described above, by repeating the steps of pressurization, product removal, decompression pressure equalization, regeneration, and pressure equalization as shown in FIGS. Nitrogen gas as a gas is obtained. In the regeneration process, the inside of the cylinder may be evacuated by a vacuum pump as necessary.

  In the PSA operation that repeats the process shown in FIGS. 2A to 2F as described above, it is necessary to appropriately set the switching time of each process. That is, when the flow rate of raw material air and the flow rate of product nitrogen gas are fixed, if the pressurization time (sometimes expressed as adsorption time) is too short, the in-cylinder pressure does not reach the raw material air supply pressure and is adsorbed. The performance of the agent cannot be fully demonstrated. On the other hand, if the pressurization time is too long, the amount of raw material air introduced increases, so the oxygen adsorption amount of the adsorbent is saturated, oxygen breaks through, and the purity of the product nitrogen gas decreases. It is also important to select an appropriate pressurization time depending on the oxygen adsorption rate and nitrogen adsorption rate of the adsorbent used. That is, when an adsorbent having a high oxygen adsorption rate is used, it is necessary to set an early switching time (short pressurization time). Therefore, by setting the optimal pressurization time according to the supply amount of nitrogen gas that is the product gas, the amount of raw material air, and the performance of the adsorbent, nitrogen gas with a predetermined flow rate and a predetermined purity can be generated efficiently. It becomes possible.

In order to efficiently generate high-purity nitrogen gas with a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) using the molecular sieve carbon described above as the adsorbent of the present embodiment, it is necessary to manage each condition. is there. Specifically, the pressurization time is preferably 60 to 70 seconds, and is preferably closer to 65 to 68 seconds. Moreover, the space velocity (SV value: ratio of the amount of air introduced per unit time to the amount of adsorbent charged) in the adsorption cylinder in the pressurization process and the product take-out process is set in the range of 420 to 530 hr ⁻¹ . In addition, the amount of nitrogen gas extracted from the apparatus (product gas generation amount per ton of adsorbent filled in the nitrogen PSA apparatus) is set to a range of 68 Nm ³ / hr · ton or less. Thereby, high purity nitrogen gas with a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) can be generated using the PSA nitrogen gas generator 2 of the present embodiment.

(Nitrogen gas pressurization process)
Next, in the step of boosting nitrogen gas, the booster 3 boosts the nitrogen gas generated by the PSA type nitrogen gas generator 2. Generally, the gas discharge pressure from the PSA type nitrogen gas apparatus 2 is 1.0 MPa or less, and specifically, it is often around 0.5 to 0.6 MPa. For this reason, the high-pressure nitrogen gas is boosted to 2.0 to 5.0 MPa using the booster 3.

(Nitrogen gas storage process)
Next, in the step of boosting nitrogen gas, the high-pressure and high-purity nitrogen gas boosted by the booster 3 is stored in the storage tank 4. Specifically, in the nitrogen gas storage step, impurities such as oil and dust contained in the high-pressure and high-purity nitrogen gas after the nitrogen gas pressure-up step are filtered by the filter 24 and then stored in the storage tank 4. The pressure in the storage tank 4 can be measured with the pressure gauge 23, and the oxygen concentration in the storage tank 4 can be measured with the oxygen concentration meter 33.

(Nitrogen gas supply process)
Next, in the nitrogen gas supply step, the nitrogen gas is depressurized and supplied to a laser processing machine or the like (not shown) arranged in the subsequent stage. Specifically, the high-pressure and high-purity nitrogen gas stored in the storage tank 4 can be adjusted to 5.0 MPa or less by the pressure reducing valve 26, and has a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less). In addition, a large amount of gas can be temporarily supplied while controlling the pressure of the high purity nitrogen gas.

  By the way, the pressure, flow rate, and concentration of the nitrogen gas that is generated by the two-cylinder switching type PSA-type nitrogen gas generator 2 change as the product gas when the adsorption cylinder is switched. The PSA nitrogen gas generator 2 is provided with a buffer tank 8 in order to reduce this fluctuation. Thereby, nitrogen gas can be stably supplied from the PSA type nitrogen gas generator 2 to the booster 3. However, there is a possibility that a pressure drop on the inlet side 3a may occur during operation of the booster 3. When the pressure drop on the inlet side 3a of the booster 3 occurs, the discharge performance such as the pressure and flow rate from the booster 3 is lowered. In addition, the booster 3 itself may stop.

  Therefore, as shown in FIG. 5, according to the conventional supply device 101, the size of the buffer tank 108 in the PSA-type nitrogen gas generator 102 is increased in order to prevent a decrease in pressure on the inlet side 103a of the booster 103. The method and the method of newly providing the storage tank 140 between the PSA type nitrogen gas generator 102 and the pressure | voltage riser 103 respond | corresponded. Thereby, although the fall of the pressure of the inlet side 103a of the pressure | voltage riser 103 was able to be suppressed, the malfunctions, such as the enlargement of an apparatus and the increase in installation cost, have arisen.

  On the other hand, according to the supply device 1 of the present embodiment shown in FIG. 1, the return path L2 is provided in the gas supply path L1, and the pressure of the nitrogen gas on the inlet side 3a of the booster 3 is reduced. In some cases, nitrogen gas can be returned from the outlet side 3b to the inlet side 3a. As a result, the pressure of the nitrogen gas discharged from the PSA-type nitrogen gas generator 2 (that is, the pressure on the inlet side 3a of the booster 3) can be reduced, and excessive suction of the booster 3 can be prevented. Of nitrogen gas can be supplied. Further, the buffer tank 8 can be reduced in size, and it is not necessary to newly provide a storage tank between the PSA type nitrogen gas generator 2 and the booster 3, so that the supply device 1 can be reduced in size and the apparatus price can be reduced. .

  As described above, according to the high-pressure and high-purity nitrogen gas supply device and supply method of the present embodiment, the booster 3 that boosts the nitrogen gas generated by the PSA-type nitrogen gas generator 2 is provided. Therefore, it becomes possible to supply high-pressure nitrogen gas using a general PSA-type nitrogen gas generator.

  Further, the nitrogen gas is returned from the outlet side 3b of the booster 3 to the inlet side 3a to the gas supply path L1 provided with the booster 3 for boosting the high-purity nitrogen gas generated by the PSA type nitrogen gas generator 2. When the pressure on the inlet side 3a of the booster 3 decreases, nitrogen gas can be returned from the outlet side 3b of the booster 3 to the inlet side 3a. Thereby, the pressure on the inlet side 3a of the booster 3 can be recovered without excessively supplying nitrogen gas from the PSA type nitrogen gas generator 2 to the booster 3. Therefore, the performance of the PSA type nitrogen gas generator 2 can be exhibited and high purity nitrogen gas can be supplied.

  Thus, even when the pressure on the inlet side 3a of the booster 3 is reduced, the pressure on the inlet side 3a can be recovered using the return path L2, so that the inside of the PSA-type nitrogen gas generator 2 can be recovered. There is no need to increase the size of the buffer tank 8 provided in the apparatus, and it is not necessary to separately install a tank for storing nitrogen gas between the PSA type nitrogen gas generator 2 and the booster 3. Thereby, a general PSA type nitrogen gas generator can be used as it is. Therefore, the high-pressure and high-purity nitrogen gas supply device 1 and the supply method can be provided by a simple configuration and method without causing an increase in size and cost of the device.

  In addition, according to the high pressure and high purity nitrogen gas supply device and supply method of the present embodiment, since the storage tank 4 for storing the pressurized nitrogen gas is provided, the nitrogen gas is supplied from the storage tank 4 to the use device. In addition, the pressure of the supply gas can be controlled, and a large amount of high-pressure and high-purity nitrogen gas can be temporarily supplied.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the high-pressure and high-purity nitrogen gas supply device 1 of the above embodiment, the case where high-pressure and high-purity nitrogen gas having a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) is supplied has been described, but it is particularly limited. It is not something. For example, nitrogen gas having a nitrogen purity of 99.99% (residual oxygen concentration of 100 ppm or less) may be supplied. In this case, the buffer tank 8 provided inside the PSA type nitrogen gas generator 2 can be further downsized or omitted.

  In the above embodiment, according to the high-pressure and high-purity nitrogen gas supply apparatus and supply method, the case where nitrogen gas is supplied as the product gas has been described. However, a large amount of high-pressure and high-purity product gas is temporarily supplied. If it is a form to supply, it will not specifically limit. In this case, it is necessary to appropriately adjust the type of adsorbent and the operating conditions of the PSA apparatus.

Specific examples are shown below.
Example 1
Supply of high-pressure and high-purity nitrogen gas using the PSA-type nitrogen gas generator (adsorbent filling amount 390 kg / cylinder) filled with the molecular sieve carbon of the above embodiment as an adsorbent and an air compressor of Atlas Copco GA37FF Configured the device. The pressure of the raw material air is 0.95 MPa, the space velocity SV value of the raw material air in the adsorption cylinder (ratio of the amount of air introduced per unit time and the filling amount of the adsorbent) is 420 hr ⁻¹ , and the pressurization time is 68 seconds. Set each. The residual oxygen concentration in the nitrogen gas was measured with a trace oxygen analyzer manufactured by Teledyne. The results are shown in FIG. FIG. 3 illustrates the amount of nitrogen gas extracted from the PSA type nitrogen gas supply device (product gas generation amount per ton of adsorbent filled in the nitrogen PSA device), that is, the relationship between the capacity and the residual oxygen concentration in the nitrogen gas. FIG.

As shown in FIG. 3, the space velocity SV value of the raw material air in the adsorption cylinder is set to 420 hr ⁻¹ , and the amount of nitrogen gas extracted from the PSA nitrogen gas generator, that is, the capacity is set to 70 Nm ³ / hr · By setting it to be less than ton, high purity nitrogen gas having a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) could be generated.

Here, the air flow rate required for introduction is calculated as 2.74 m ³ / min from the space velocity SV value 420 hr ⁻¹ of the raw material air in the adsorption cylinder. Moreover, the upper limit of the space velocity SV value of the raw material air in the adsorption cylinder is 530 hr ⁻¹ calculated from the discharge air amount of the air compressor 22 kW specification.

Next, FIG. 4 shows the result of setting the raw material air pressure to 0.95 MPa, the raw material air space velocity SV in the adsorption cylinder to be 510 hr ⁻¹ close to the upper limit, and the pressurization time to 65 seconds. Here, FIG. 4 is also a diagram illustrating the relationship between the capacity and the residual oxygen concentration in the nitrogen gas, as in FIG.

As shown in FIG. 4, the space velocity SV value of the raw material air in the adsorption cylinder is set to 510 hr ⁻¹ , and the amount of nitrogen gas taken out from the PSA type nitrogen gas generator, that is, the capacity is set to 68 Nm ³ / hr · If it was less than ton, high-purity nitrogen gas having a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) could be generated.

From the results of FIGS. 3 and 4, the pressurization time is set in the range of 65 to 68 seconds, the space velocity SV value of the raw material air in the adsorption cylinder is set in the range of 420 to 510 hr ⁻¹ , and the capacity is set to 68 Nm. If it was ³ / hr · ton or less, high-purity nitrogen gas having a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) could be generated efficiently.

(Example 2)
Using the 2BSN8 nitrogen gas booster manufactured by Sanwa Iron Works Co., Ltd., high purity nitrogen gas with a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) and a discharge pressure of 0.6 MPa produced in Example 1 was used. After raising the pressure to 4.5 MPa, the pressure was stored in a 1200 L tank manufactured by Kanazawa Seiko Co., Ltd. Here, in Example 1 having a return path, as shown in Table 1, the booster suction pressure is 0.6 MPa, the booster discharge nitrogen gas flow rate is 25 Nm ³ / hr, and as a result, the upper limit high-purity nitrogen gas that can be supplied The flow rate was 25 Nm ³ / hr, and a stable nitrogen gas supply was achieved. The residual oxygen concentration in the nitrogen gas in the tank was 99.999% (residual oxygen concentration of 10 ppm or less) as a result of measurement with a teledyne trace oxygen analyzer.

(Comparative Example 1)
Using the 2BSN8 nitrogen gas booster manufactured by Sanwa Iron Works Co., Ltd., high purity nitrogen gas with a nitrogen purity of 99.999% (residual oxygen concentration of 10 ppm or less) and a discharge pressure of 0.6 MPa produced in Example 1 was used. After raising the pressure to 4.5 MPa, the pressure was stored in a 1200 L tank manufactured by Kanazawa Seiko Co., Ltd. Here, in Comparative Example 1 having no return path, as shown in Table 1, the booster suction pressure is 0.5 to 0.6 MPa, and the booster discharge nitrogen gas flow rate is 20 to 25 Nm ³ / hr. The upper limit high-purity nitrogen gas flow rate that can be supplied was 20 to 25 Nm ³ / hr, and unstable nitrogen gas supply was achieved. The residual oxygen concentration in the nitrogen gas in the tank was 99.999% (residual oxygen concentration of 10 ppm or less) as a result of measurement with a teledyne trace oxygen analyzer.

  The apparatus and method for supplying high-pressure, high-purity nitrogen gas of the present invention have applicability in the field of laser processing machines such as non-oxidative cutting assist gas for stainless steel plates and optical path purge gas, and in the semiconductor field.

1 ... High pressure and high purity nitrogen gas supply device 2 ... PSA type nitrogen gas generator (pressure fluctuation adsorption type nitrogen gas generator)
DESCRIPTION OF SYMBOLS 3 ... Booster 3a ... Inlet side 3b ... Outlet side 4 ... Storage tank 5 ... Air compressor 6 ... Air storage tank 7A, 7B ... Adsorption cylinder 8 ... Buffer tank (primary storage tank)
9a ... 1st inlet valve 9a
9b ... second inlet valve 9b
10a ... first exhaust valve 10b ... second exhaust valve 11 ... purge valve 12 ... upper pressure equalizing valve 13 ... lower pressure equalizing valve 14a ... first check valve 14b ... first 2 check valve 15 ... first mass flow controller 16 ... second mass flow controller 17 ... flow rate adjustment valve 18a ... inlet side pressure adjustment valve 18b ... outlet side pressure adjustment valve 19, 20, 21 , 23 ... Pressure gauges 22, 25 ... Oxygen concentration meter 24 ... Filters 26, 27 ... Pressure reducing valve L1 ... Nitrogen gas supply path (gas supply path)
L2 ... Return route

Claims (7)

A pressure fluctuation adsorption-type nitrogen gas generator that generates high-purity nitrogen gas from raw air in a gas supply path; a pressure booster that boosts the nitrogen gas generated by the pressure fluctuation adsorption-type nitrogen gas generator; and A storage tank for storing the nitrogen gas boosted by a booster; and means for supplying the storage tank with a reduced pressure.
A high-pressure and high-purity nitrogen gas supply device, wherein a return path for returning the nitrogen gas from the outlet side to the inlet side of the booster is provided in the gas supply path.   2. The high-pressure and high-purity nitrogen gas supply device according to claim 1, wherein decompression means is provided in the return path. The pressure fluctuation adsorption type nitrogen gas generator comprises two or more adsorption cylinders filled with molecular sieve carbon as an adsorbent,
The pressure of the raw material air to be introduced is in the range of 0.9 to 1.0 MPa in gauge pressure,
The ratio of the raw material air amount introduced per unit time and the adsorbent filling amount is in the range of 420 to 510 hr ⁻¹ ;
The production amount of the high purity nitrogen gas per ton of the adsorbent filled in the pressure fluctuation adsorption type nitrogen gas generator is 68 Nm ³ / hr · ton or less. A high-pressure and high-purity nitrogen gas supply device described in 1. The molecular sieve carbon has an oxygen adsorption rate constant of 6.5 × 10 ⁻² S ⁻¹ or more, and a ratio between the oxygen adsorption rate constant K (O ₂ ) and the nitrogen adsorption rate constant K (N ₂ ). α is 35 or more,
The adsorption rate characteristic has a relationship of the following formula (1) between the time t ₉₅ required to adsorb the oxygen equilibrium adsorption amount 95% and the time t ₅₀ required to adsorb the oxygen equilibrium adsorption amount 50%. The high-pressure and high-purity nitrogen gas supply device according to claim 3.
(T ₉₅ / t ₅₀ ) <0.4 (α-24) (1)   5. The high-pressure and high-purity according to claim 1, wherein the pressure fluctuation adsorption-type nitrogen gas generator includes a primary storage tank that stores the generated high-purity nitrogen gas. Nitrogen gas supply device. Oxygen is absorbed by the adsorbent packed in the adsorption tower according to a pressure fluctuation adsorption gas separation method in which raw material air is supplied to two or more adsorption towers, and an adsorption process for pressurizing the adsorption tower and a regeneration process for depressurizing the adsorption tower are sequentially performed. Separating the component and the nitrogen component to produce high purity nitrogen gas;
Boosting the generated nitrogen gas with a booster;
Storing the pressurized nitrogen gas;
A step of reducing the pressure of the stored nitrogen gas and supplying the nitrogen gas,
A high-pressure and high-purity nitrogen gas supply method, wherein when the pressure of the nitrogen gas on the inlet side of the booster decreases, the nitrogen gas is returned from the outlet side of the booster to the inlet side.   When the pressure of the nitrogen gas on the inlet side of the booster decreases, when the nitrogen gas is returned from the outlet side of the booster to the inlet side, the pressurized nitrogen gas is supplied under reduced pressure The high-pressure and high-purity nitrogen gas supply method according to claim 6.

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