JPH01115801A - Purification of hydrogen gas and device therefor - Google Patents

Abstract

PURPOSE:To obtain a purified hydrogen gas having high purity continuously and stably, by passing a hydrogen gas containing oxygen as an impurity through a reaction column and recleaning a purifying column standing by ready with a purified self gas at a specific stage of adsorption purification. CONSTITUTION:At a point of time when purification of hydrogen containing oxygen as an impurity is advanced in an adsorbing column A and the progress ratio of adsorption purification process based on the flow rate integrated value of a raw material gas reaches a given value to carry out recleaning, a signal to reclean an adsorbing column B is sent from a control part. An on-off valve part Vb of a four-way change valve V1 and an on-off valve part Vd of a four-way change valve V2 are opened so that recleaning by a purified self gas in the adsorbing column B is continued for a given time. Then the interior of the adsorbing column B is made into a uniform pressure state by the purified self gas and the adsorbing column is standing by ready to change to the adsorbing purification process. By using both the four-way change valves V1 and V2, there is no dead space such as branched tube apt to retain a gas and an impurity which is estimated to remain in fine cracks in column walls to be diffused and admixed in space in the adsorbing column standing by ready after regeneration of an adsorbent is completely removed by the recleaning.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for purifying hydrogen gas, and more particularly to a method for removing impurities such as oxygen, water, and carbon dioxide contained in hydrogen gas. The present invention relates to a hydrogen gas purification method and apparatus for obtaining highly purified hydrogen gas.

Hydrogen gas is used in large quantities in semiconductor manufacturing processes, and in recent years, with the rapid progress in the high degree of integration of semiconductors, there has been a strong demand for extremely high purity hydrogen gas.

[Conventional technology]

A method for removing small amounts of oxygen, water, carbon dioxide, etc. contained as impurities in hydrogen gas and obtaining purified hydrogen gas involves a reaction process in which oxygen is converted to water using a catalyst such as Ni5Cu, and an adsorbent such as zeolite. A method is known that combines an adsorption purification process in which water and carbon dioxide are removed by adsorption. In this case, the adsorbent will need to be regenerated as the amount of impurities adsorbed increases, so in order to continuously purify the gas, at least two series of adsorption cylinders should be installed and these should be switched sequentially. For example, an apparatus as shown in the flow sheet of FIG. 4 is used.

In Figure 4, a catalyst such as Ni5Cu is filled.
.

The inlet 32 and outlet 33 of the reactor cylinder 31 are connected to a source gas supply path 34 and a reaction gas flow path 35, respectively. On the other hand, it is filled with an adsorbent layer such as zeolite,
In addition, the inlets of adsorption cylinders A and B to which heaters 36 are attached are connected to channels 38a # and 38b, respectively,
The other ends of the flow paths 38a and 38b are branched, and one of them is connected to a flow path 35 for the reaction gas through on-off valves Via and Vlb, respectively, and the other end is connected to a discharge path 37 for regenerated exhaust gas through on-off valves V2a and V2b, respectively. is connected to.

Furthermore, the outlets of adsorption cylinders A and B are connected to flow paths 41a and 41.
b, and the other ends of the flow paths 41a and 41b are branched, one of which is connected to the purified gas extraction path 39 via on-off valves v3a and V3b, respectively, and the other is regenerated via on-off valves V4a and V4b, respectively. It is connected to a supply line 40 for purified self-gas. From the supply path 34 to the reaction tube 31
When the raw material hydrogen gas that has entered comes into contact with the catalyst, the oxygen gas contained in the hydrogen gas reacts with the hydrogen gas and is converted to water, and after the contact, the hydrogen gas flows from the outlet 33 to the reaction gas flow path 35. Get out. Adsorption purification of the reaction gas is carried out continuously by alternately using the adsorption cylinders A and B. For example, when the inlet is in the purification process, the on-off valves Via and V3a are opened and the gas exiting the reaction column 31 enters the adsorption column from the flow path 35 via Via and the flow path 38a, and comes into contact with the adsorbent, thereby reducing moisture. and other impurities are adsorbed and purified, and the purified hydrogen gas flows through the channel 41a,
It is extracted through the on-off valve V3a and the extraction passage 39. During this time, the adsorbent is regenerated in the adsorption cylinder B. First, the adsorbent is heated by the heater 36, and then the on-off valve V2b is heated.
Then, V4b is opened, and the purified self-gas for regeneration (part of the purified hydrogen gas) enters the adsorption cylinder B via V4b and the flow path 41b. Impurities such as moisture and carbon dioxide gas adsorbed by the adsorbent are separated by heating and are discharged from the discharge passage 37 together with the purified self-gas through the passage 38b and the on-off valve V2b as regenerated exhaust gas.

FIG. 5 is a diagram showing the purification process and regeneration process in adsorption cylinders A and B in chronological order. In Figure 5, while adsorption and purification continues in the entry section, the adsorbent is heated and regenerated using purified self-gas in cylinder B, but since the regeneration is completed in a relatively short time, it is then in a standby state and cannot be used for the entry section. When the adsorption purification is completed, the process is switched to the adsorption purification process, and the input part enters the regeneration process instead.

In such equipment, switching from the adsorption purification process to the regeneration process, heating in the regeneration process, and distribution of purified self-gas for regeneration are performed by operating the heater and each on-off valve based on preset times using a sequencer, etc. It is common for this to be done automatically.

The time required for each process in gas adsorption purification and adsorbent regeneration varies depending on the concentration of impurities contained in the gas, the gas flow rate, the size of the adsorption cylinder, etc., and cannot be specified in part.
Since the adsorbent regeneration step is usually shorter than the adsorption purification step, the regenerated adsorption column remains in a standby state for a relatively long time until switching to the next adsorption purification step.

For example, while the adsorption purification process takes 50 to 100 hours, the regeneration process using purified self-gas takes 5 to 10 hours, and the standby time is 4 hours.
It is said to take about 5 to 90 hours.

[Problem that the invention seeks to solve]

As semiconductors become more highly integrated, submicron-level ultra-LSI
In order to obtain purified gas of ultra-high purity by dealing with the manufacturing process of Measures are being taken to prevent the contamination of other gases, such as refining the inner walls and shortening the branch sections of piping to reduce the number of areas where other gases accumulate. However, even with such measures, the contamination of impurities is still not completely prevented, and the concentration of impurities tends to increase, especially at the beginning of switching the adsorption column, making it difficult to continuously and stably obtain high-purity gas. There was a problem.

[Means for solving problems]

The inventors of the present invention have worked hard to solve these problems and to develop a purification method and apparatus that can continuously and stably obtain purified gas of extremely high purity without contamination with impurities, and that have excellent operational efficiency. As a result of repeated efforts, we discovered that these objectives could be achieved by using a four-way switching valve in the equipment and by re-sweeping the regenerated adsorption column with purified self-gas before switching to the refining process. , arrived at the present invention.

That is, the present invention comprises: (1) a reaction step of passing hydrogen gas through a reaction cylinder filled with a catalyst and converting oxygen gas contained as an impurity in the hydrogen gas into water; and at least two reaction cylinders filled with an adsorbent. Hydrogen gas is continuously purified by sequentially switching between series of adsorption cylinders and repeating the adsorption purification process of the gas emitted from the reaction cylinder using an adsorbent and the heating regeneration process of the adsorbent using purified self-gas. In the purification method, when the progress rate of the adsorption purification process in the adsorption cylinder during adsorption purification exceeds at least 70% and before the adsorption purification process is completed, the regeneration of the adsorbent is completed and it is possible to switch to the purification process. A hydrogen gas purification method characterized by re-scavenging the inside of a purification cylinder on standby with purified own gas, and (2) a catalyst for converting oxygen gas contained as an impurity in hydrogen gas into water. A hydrogen gas purification apparatus having a reaction column 1 filled with hydrogen gas and two series of adsorption columns A and B filled with an adsorbent for removing impurities in the hydrogen gas led from the reaction column 1, The block-shaped main body has four on-off valve parts built into an integrated structure, and one of the gas inlets and outlets of each of the on-off valve parts is shared with one of the gas inlets and outlets of the adjacent on-off valve part. Four-way switching valves v1 and v with four entrances and exits
2, flow paths 10a J6 and 10b connecting the inlets 6a and 6b of the purification 57jA and B and the gas inlet/outlet Na and Nb of the four-way switching valve v1, respectively, the gas inlet/outlet Nc and the outlet 3 of the reaction tube 1; a regenerated exhaust gas discharge path 11 connected to the gas inlet/outlet Nd, outlets 8a and 8h of the adsorption cylinders A and B, and the gas inlet/outlet Na and Nb of the four-way switching valve v2, respectively. Connecting channels 12a and 12b, a purified gas extraction path 13 connected to the inlet/outlet Nd, and a regenerating purified self-gas supply path 14 branched from the extraction path 13 and connected to the inlet/outlet Nc.
A hydrogen gas purification apparatus is characterized by comprising:

The present invention will be specifically illustrated and explained with reference to the drawings. FIG. 1 is a flow sheet showing an example of the device of the present invention, FIG. It is a diagram shown in series.

In FIG. 1, an inlet 2 and an outlet 3 of a reaction tube 1 filled with catalysts such as Ni and Cu are connected to a raw material gas supply path 4'# and a reaction gas flow path 5 to which a flow rate detection end F1 is attached, respectively. It is connected. On the other hand, the two-line purification cylinder has an inlet 6 for raw gas at the head and an outlet 8 for purified gas connected to a conduit 7 that penetrates the adsorbent layer and reaches the bottom, and is equipped with a heater 9. The inlets 6a and 6b of A and B are connected to the four-way switching valve v by flow paths 10a and 10b.
1 and connected to the entrances Na and Nb, respectively.

Further, a reaction gas flow path 5 and a regeneration exhaust gas discharge path 11 are connected to the inlet/outlet ports Nc and Nd of the four-way switching valve v1, respectively. In addition, the outlets 8a and 8b of the adsorption cylinders A and B are connected to the four-way switching valve v2 by the flow paths 12a and 12b.
are connected to entrances Na and Nb, respectively. Further, at the inlets and outlets Nd and Nc of the four-way switching valve v2, a purified gas extraction passage 13 is branched from the extraction passage 13, and a pressure gauge P1, a needle valve v3, and a flow meter F2 are provided. supply paths 14 are connected to each other.

The four-way switching valves v1 and v2 used in the present invention have an integrated structure with four on-off valve parts built into a block-shaped main body, and have four gas inlets and outlets, and each on-off valve part has an integrated structure. One of the gas inlets and outlets is common to one of the gas inlets and outlets of the adjacent on-off valve sections. FIG. 2 specifically illustrates these, and the opening and opening are cross-sectional views showing the principle of four-way switching valves having different structures.

In FIG.
, an inner valve 22, and a valve shaft 23, and are connected to an actuator 24 outside the main body 20. Four opening/closing valve parts Va, VbSVc, and Vd are provided in mutually symmetrical positions, respectively. Each actuator 24 has a cylinder 26 provided with a compressed air inlet 25, a piston 27 connected to the valve shaft 23, and a spring 28, and opens and closes when the piston 27 is pressed toward the valve seat 21 by the spring 28. All valve parts are normally closed.

Inside the main body 20, the opening/closing valve parts Va and vb have openings Nc, the openings and closing valves Va and Vc have openings Na;
For Va and Vd, an inlet/outlet Nb5; for Vc and Vd, an inlet/outlet Nd is provided as a common inlet/outlet for adjacent on-off valve sections. Each on-off valve section supplies compressed air to the actuator 24 from an inlet 25,
The open state can be achieved by moving the piston 27 against the spring 28. When the on-off valve Va opens, the inlets and outlets Na and Nc open, and when Vb opens, the inlets and outlets Nb and Nc open.

When Vc opens, Na and Nd communicate with each other, and when Vd opens, Nb and Nd communicate with each other, allowing gas to be switched to a predetermined flow path and allowed to flow.

The opening in Figure 2 has a structure that combines two sets of two valves with an inner valve shaft and an outer valve shaft that can slide against each other, instead of providing four opening/closing valve parts of the same type as in Figure 2 A. It is what was done.

Divided into two chambers, upper and lower, each chamber has two inlets for compressed air.
5. The piston 27X of the lower cylinder 26X of the double actuator 24, which is a cylinder 26 having a piston 27 and a spring 28, is connected to the outer valve shaft 23X having an inner valve 22X, and the piston 27Y of the upper cylinder 26Y is connected to the inner valve. 22Y and an inner valve shaft 23Y, respectively.

The piston 27X is pushed upward by a spring 28X, and the piston 27Y is pushed downward by a spring 28Y, so that the respective opening/closing valve portions are normally closed. By supplying compressed air to the cylinder 26X, the piston 27X is connected to the spring 28.
It is pushed down against X to open the on-off valve section Va or vb. Furthermore, by supplying compressed air to the cylinder 26Y, the piston 27Y is pushed up against the spring 28Y, and the on-off valve portion Vc or Vd is opened. Regarding the entrance and exit through which each opening/closing valve is opened and communicated, there is a second
This is the same as explained in Figure A.

By using such a four-way switching valve, in the four-way switching valve v1 in FIG. 1, when the on-off valve part Va opens, the flow path 1
0a and the flow path 5, when the on-off valve section vb opens, the flow path 10b and the flow path 5, when the on-off valve section Vc opens, the flow path 10a and the discharge path 11, and when the on-off valve section Vd opens, the flow path 10b and the discharge path 11. are in communication with each other, and in the four-way switching valve v2, when the on-off valve part Va opens, the flow path 12a, the supply path 14, and the on-off valve part vb open (and the flow path 1
2b and the supply path 14, when the on-off valve section Vc is opened, the flow path 12a and the extraction path 13, and when the on-off valve section Vd is opened, the flow path m12b and the extraction path 13 are communicated with each other.

The flow rate detection end F1 of the raw material gas supply path 4, the power source of the heater 9, and each on-off valve section are each connected by a signal line to a control section having flow rate integration and sequence timer functions (For the signal line and control section, (not shown).

[Effect]

As shown in FIG. 3, while hydrogen gas is adsorbed and purified in the adsorption column A, the adsorbent is heated and regenerated using purified self-gas in the adsorption column B.

In this example, the switching of the adsorption cylinder and the start of resweeping of the regenerated adsorption cylinder that is on standby are operated based on the progress rate of the adsorption purification process corresponding to the integrated flow rate of the raw hydrogen gas, and each opening/closing in the other processes is performed. The valve operation and heating operation are each performed based on preset times.

- Purification of hydrogen gas is started by opening the on-off valve section Va of the four-way switching valve v1 and the on-off valve section Vc of the four-way switching valve v2. The raw material gas enters the reaction tube l from the supply path 4 and comes into contact with the catalyst, whereby the oxygen gas in the hydrogen gas reacts with the hydrogen gas and is converted to water. The gas enters the adsorption cylinder A from the inlet 6a via the flow path 5, the on-off valve part Va of the four-way switching valve v1, and the flow path 10a, contacts the adsorbent, and water and carbon dioxide are adsorbed and removed to the bottom of the cylinder. There, it is reversed and passes through the conduit 7 to reach the outlet 8a, and further passes through the flow path 12a and the four-way switching valve v.
The refined gas is extracted from the extraction passage 13 via the on-off valve section Vc of No. 2. Gas continues to be purified while flowing through a flow path with no dead spaces such as branch pipes.

On the other hand, in the control section, the flow rate detection end I? The flow rate of the raw material gas continues to be integrated based on the signal transmitted from 1, and when the progress rate of adsorption purification based on the integrated flow rate up to the switching of the adsorption cylinder reaches a predetermined value (for example, 95%), the control unit controls the regeneration in the adsorption cylinder B. An operation signal for starting scavenging is transmitted. Adsorption tube A
The adsorption and purification of the gas continues further, and when the cumulative flow rate reaches a predetermined value (progress rate of 100%), a signal for switching the number of adsorption cylinders from 8 to B is transmitted from the control unit.

Here, the on-off valve part Va of the four-way switching valve v1 and the on-off valve part Vc of the four-way switching valve v2 are closed, and at the same time, the on-off valve part vb of vl and the on-off valve part vb of v2 are opened, and the adsorption cylinder B
The adsorption purification of the gas is started, and the adsorption column A enters the regeneration process.

On the other hand, while adsorption and purification of gas is being performed in the adsorption column A, heating regeneration of the adsorbent using purified own gas is performed in the adsorption column B.

The adsorption cylinder B is heated by the heater 9 in response to a signal from the control unit for which the time has been set, and then the on-off valve part V of the four-way switching valve v1 is heated.
d and the on-off valve section vb of the four-way switching valve v2 are opened. The purified self-gas for regeneration enters the adsorption cylinder B from the outlet 8b via the on-off valve part vb of the four-way switching valve v2 and the flow path 12b, while the flow rate is adjusted by the needle valve v3, and passes through the conduit 7 before being preheated. It reaches the bottom of the cylinder. Here, the purified self-gas for regeneration reverses and rises, entraining impurities such as water and carbon dioxide that have been separated from the adsorbent, and while scavenging the inside of the adsorption column B, reaches the inlet 6b and flows as exhaust gas for regeneration. Via the on-off valve part Vd of the four-way switching valve v1 of the path 10b1,
It is released from the regeneration exhaust gas release path 11. In this state, heating regeneration of the adsorbent is continued for a predetermined period of time. After the regeneration of the adsorbent is completed, the heating is stopped, and the scavenging and cooling of the adsorption column B using the purified self-gas is continued for a predetermined period of time. The pressure inside the cylinder B is equalized by purified self-gas. Next, the on-off valve section vb of the four-way switching valve v2 is closed and the system enters a standby state. On the other hand, when the purification in the adsorption cylinder progresses and the progress rate of the adsorption purification process based on the integrated flow rate of the raw material gas reaches a predetermined value for re-scavenging, the control unit re-scavenges the inside of the adsorption cylinder B. A signal is transmitted. By opening the on-off valve section Vd of the four-way switching valve v1 and the on-off valve section vb of the four-way switching valve v2, rescavenging with the purified self-gas in the adsorption cylinder B continues for a predetermined period of time.

Next, the pressure inside the adsorption cylinder B is brought to an equal pressure state again by the purified self-gas, and preparation is made for switching to the adsorption purification process. By using the four-way switching valves V1 and V2, there are no dead spaces such as branch pipes where gas can easily accumulate, and this re-sweeping air can cause fine cracks on the cylinder wall that cannot be completely removed even by Kenreki, remaining on racks, etc., and regenerating the adsorbent. Impurities that are estimated to have diffused and mixed into the space inside the adsorption cylinder, which is currently on standby, are completely removed.

In the present invention, the progress rate of adsorption purification in the adsorption purification process exceeds at least 70%, and the adsorbent has been regenerated and the purification column is on standby in preparation for switching to the adsorption purification process by the time the adsorption purification process is completed. Rescavenging is performed using purified self-gas inside the tank.

Here, the progress rate of the adsorption purification process is the ratio (%) of the cumulative flow rate up to each point in time to the cumulative flow rate of gas from the start to the end of the adsorption purification process in one purification column, or after the start of the adsorption purification process. Defined as the ratio (%) of the time required to reach each point to the time required to complete.

The time required for re-scavenging and pressure equalization varies depending on the shape and size of the adsorption cylinder, the flow rate of purified self-gas for regeneration, etc.
- It cannot be specified generally, but in practice, it is usually about 30 to 120 minutes. It is preferable that the start timing of re-scavenging is set so as to take these times into consideration and end immediately before switching of the adsorption cylinders.

Re-scavenging air and adsorption column switching may be performed four times at a preset time or at the cumulative flow rate, but the integrated method is effective in that the total throughput can always be kept constant even if there are fluctuations in the gas flow rate during the purification process. Methods based on flow rate are preferred.

The four-way switching valve used in the present invention has four on-off valve sections built into a block-shaped main body, and one of the gas inlets and outlets of each on-off valve section is one of the gas inlets and outlets of the adjacent on-off valve section. It has four common gas inlets and outlets, and has an integrated structure as a whole.

Such a four-way switching valve can be relatively easily obtained by conventionally known processing techniques based on the structural principle illustrated in FIG.

There are no particular restrictions on the structure of the adsorption column used in the present invention, but in consideration of shortening the piping distance and preheating the purified self-gas during regeneration, we designed a structure that penetrates the adsorbent layer as shown in Figure 1. However, by providing a conduit leading to the bottom of the cylinder, it is preferable that both the inlet and the outlet of the gas be adsorbed and arranged together at one end of the cylinder.

〔Effect of the invention〕

According to the method of the present invention, by performing re-scavenging before switching to the adsorption purification process, it is possible to remove even minute amounts of impurities that are estimated to have diffused into the cylinder wall during standby, and the apparatus of the present invention According to the authors, by using a four-way switching valve, there are no dead spaces where gas accumulates at piping branches, etc., and scavenging within the system is performed reliably, so that purified hydrogen gas of extremely high purity can be stabilized from the time the adsorption cylinder is switched. You can get it.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of the device of the present invention, FIG. FIG. 4 is a flow sheet of a conventional device, and FIG. 5 is a diagram showing a conventional method in chronological order. Each symbol in the drawing is as follows. A and B - "Adsorption cylinder, 1..., reaction cylinder, 10a, 1
0b, 12a, 12b and 5...-flow path, 4 and 14-Pa supply path, 11--Pa discharge path, 13...-° extraction path v1 and v2...Four-way switching valve Patent applicant Nippon Bionics Co., Ltd. Company Representative: Ryo Yamazaki - Agent: Patent Attorney: Sadafumi Kobori et al.

Claims (2)

[Claims] (1) A reaction step in which hydrogen gas is passed through a reaction cylinder filled with a catalyst to convert oxygen gas contained as an impurity in the hydrogen gas into water, and at least two series of adsorption cylinders filled with an adsorbent. In a hydrogen gas purification method that continuously purifies hydrogen gas by repeating the adsorption purification process using an adsorbent for the gas emitted from the reaction column and the heating regeneration process of the adsorbent using purified self-gas, the adsorption When the progress rate of the adsorption purification process in the adsorption column being purified exceeds at least 70% and before the adsorption purification process is completed, the regeneration of the adsorbent has been completed and the adsorbent is on standby in preparation for switching to the purification process. A hydrogen gas purification method characterized by re-scavenging the inside of a purification cylinder with purified self-gas. (2) A reaction tube 1 filled with a catalyst for converting oxygen gas contained as an impurity in hydrogen gas into water, and an adsorption device for removing impurities in the hydrogen gas led from the reaction tube 1. In a hydrogen gas purification device that has two series of adsorption cylinders A and B filled with an agent, the block-shaped main body has four on-off valve parts built into an integrated structure, and each of the on-off valve parts Four-way switching valves V1 and V having four inlets and outlets, one of which is common to one of the gas inlets and outlets of the adjacent on-off valve section.
2, flow paths 10a and 10b connecting the inlets 6a and 6b of the purification cylinders A and B and the gas inlets and outlets Na and Nb of the four-way switching valve V1, respectively, and the gas inlet and outlet Nc and the outlet 3 of the reaction tube 1. and the gas inlet/outlet N.
d, and a flow path 1 that connects the outlets 8a and 8b of the adsorption cylinders A and B with the gas inlets and outlets Na and Nb of the four-way switching valve V2, respectively.
2a and 12b, a purified gas extraction path 13 connected to the inlet/outlet Nd, and an inlet/outlet Nc branched from the extraction path 13.
A hydrogen gas purification apparatus characterized by comprising: a regenerating purified self-gas supply line 14 connected to