JPH02135111A - High purity gas purification method and equipment - Google Patents

Abstract

PURPOSE:To surely prevent a very small amount of impurities which is not removed hitherto from being mixed into refined gas by purging a part of refined gas from the gas retaining parts existing in refined gas flow passages. CONSTITUTION:The impurities contained in gas is removed by causing the gas to flow through refining units A, B, and the refined gas is taken out from the refining units through the refined gas flow passages 6a, 6b, 7. A part of refined gas is purged from the gas retaining parts R1a, R1b, R2a, Rb, R3 existing in the refined gas flow passages through purge pipes L1a, L1b, L2a, L2b, L3. As a result, a very small amount of impurities which is not removed hitherto is surely prevented from being mixed into the refined gas. Consequently, such various high purity gases are obtained that are required in the production of highly integrated semiconductor of such as submicron class.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for purifying high-purity gas, and more particularly, to a method and apparatus for purifying high-purity gas, and more specifically, a method for preventing contamination of impure gas from a gas retention space existing in a piping system. The present invention relates to a method and apparatus for purifying high-purity gas.

BACKGROUND OF THE INVENTION With the development of the semiconductor manufacturing industry, the types and amounts of gases used in these fields are increasing, and the demand for higher purity gases is increasing.

[Conventional technology]

There are various methods for removing impurities contained in gas and obtaining purified gas, including membrane separation methods, reaction methods using catalysts and getters, adsorption methods using physical adsorption, chemical adsorption, etc., and combinations of these methods. is known9
For example, high-purity hydrogen purification equipment using a Pd alloy hydrogen permeable membrane, inert gas or hydrogen purification equipment that combines catalysts such as Ni and Cu and adsorbents such as synthetic zeolite, and conversion catalysts for impurities such as Pt and Pd. Oxygen purification equipment that combines zeolite and synthetic zeolite, rare gas purification equipment that uses metal getters, and hydrogen that uses cryogenic adsorption.
Relatively many inert gas and oxygen purification devices are used.

All of these devices basically consist of a permeate membrane, a reaction column containing a catalyst, a getter, and an adsorbent, a gas purification section such as a purification column, a raw material gas supply path, and a purified gas extraction path. Depending on the type of gas, piping is provided with various flow paths such as a supply path for regenerated gas and regenerated self-gas, a discharge path for regenerated exhaust gas or concentrated impure gas, and a gas circulation path. For this reason, piping systems have many branches or connections, as well as various valves, instruments, analyzers, and the like.

[Problem to be solved by the invention]

Using such a purification device, for example, the impurity concentration can be reduced to 1pp.
In order to obtain high-purity gas with a purity of less than B, it is not only necessary that the gas purification section has a corresponding impurity removal performance, but also the purified gas piping from the gas purification section to the outlet of the equipment. There must be no contamination of impurities in the piping system.The causes of contamination of impurities in the piping system are the intrusion of atmospheric components through diffusion and permeation at seals with the outside air such as fittings, valves, and instruments, and the intrusion of atmospheric components through various valves. Desorption gas may enter from the regeneration system side due to seat leaks, etc.

Furthermore, the influence of atmospheric components that are trapped during equipment assembly cannot be ignored, and although vacuum evacuation and replacement with gas to be purified are normally performed to remove these components, the metal surfaces of the inner surfaces of cylinders and piping Adsorbed atmospheric components are not easily removed, and their effects can last up to several hundred hours after the device is used.

To prevent the negative effects of contamination with such impurities, welded joints and high-quality joints, valves, and instruments with excellent airtightness are used, and piping is minimized to minimize the area where impurities can be absorbed. Attempts have been made to shorten the length and to smoothen the metal surface that comes into contact with the gas by abrasive treatment, but it has not yet been possible to completely prevent the incorporation of impurities.

[Means to solve the problem]

The inventors of the present invention continued to investigate the cause of purity deterioration in these devices over a long period of time, and as a result, we found that impure gas remaining in gas retention areas such as branch paths that intersect with purified gas flow paths affects the purity of purified gas. The present invention was completed by taking measures to prevent these residual gases from entering the purified gas flow path.

That is, the present invention provides (1) a method for purifying high-purity gas, in which impurities contained in the gas are removed by passing the gas through a purification section, and purified gas is extracted from the purification section via a purified gas flow path; A method for purifying a high-purity gas, characterized in that a part of the purified gas is purged from a gas retention section existing in the purified gas flow path, and (a gas having two source gas inlets and a purified gas outlet). A high-purity gas purification device having a purification section, a piping system on the raw material gas supply side connected to the inlet of the raw gas, and a piping system on the purified gas extraction side connected to the outlet of the purified gas, This is a high-purity gas purification apparatus characterized in that a purified gas purge mechanism is provided in a gas retention section in a purified gas flow path of a piping system on the purified gas extraction side.

The present invention is applied to a gas purification apparatus having a gas retention part, particularly a gas purification apparatus having many retention parts such as a branch part, such as an apparatus involving a regeneration process of a catalyst or an adsorbent.

The present invention will be specifically explained with reference to the drawings, taking an inert gas purification device as an example.

FIG. 1 is a flow sheet of a high-purity inert gas purification device.

In Fig. 1, a catalyst cylinder 1 filled with a catalyst such as Ni or Cu and an adsorption cylinder 2 filled with an adsorbent such as synthetic zeolite are connected in series, and a heater is provided in each cylinder. Catalyst cylinders 1 and 1 of two series gas purification sections A and B are connected to channels 3a and 3b, and the other ends of channels 3a and 3b are connected to valves Via and Vl.
The flow paths branched from the flow paths 3a and 3b are connected to the regeneration exhaust gas discharge path 5 via valves V2a and V2b, respectively. Further, the adsorption cylinders 2 and 2 of the gas purification sections A and B are connected to the flow paths 6a and 6b,
The channels 6a and 6b are connected via valves V3a and V3b to a purified gas extraction channel 7 equipped with a filter S, a flow meter F1, and a flow rate control valve CVt, and are branched from the channels 6a and 6b. 8a and 8b are connected to a regeneration gas supply path 9 via valves V4a and v4b, respectively. Furthermore, the regeneration gas supply path 9
The other end is branched, one of which is connected to a regeneration hydrogen gas supply path IO provided with a flow rate control valve CV2 and a flow meter F2 via a valve 5, and the other is branched from a purified gas extraction path 7. , and a pressure gauge P, a flow rate control valve CV3, and a flow meter F.
It is connected to a purified self-gas supply line 11 provided with a valve 3 through a valve 6.

Each flow path branching from the flow path of the purified gas extraction system, that is,
Between the branching part of flow paths 6a and 6b and valves V4a and V4b (Rla and Rlb), valves V3a and V3b
to the connection with the purified gas extraction path 7 (R2a
and R2b) and regeneration self-gas supply path 11
Each of the five locations (R3) serves as a retention portion.

Flow control valves CV4a and V7a and flow control valves CV are provided in the gas retention portions R1a and Rlb, respectively.
Purge pipes Lla and Llb with valve V7b and valve V7b are respectively connected. Also, the retention part R2a
, R2b and R3 each have a flow rate control valve CV5.
a, Tahaj tube L2a with CV5b and CV6
, L2b and L3 are connected to each other, the other end of each purge pipe is connected to one end of the purge main pipe equipped with a moisture meter W and valve v8, and the other end of the purge main pipe is connected to the discharge path 5 of the regenerated exhaust gas. has been done. Furthermore, purge pipe Ll
The other ends of a and Llb are also connected to the main purge pipe.

[For production]

Gas purification is carried out continuously by alternately using purification sections A and B. For example, when the refining section A is in the refining process, the valves Via and V3a are opened, so that raw material gas such as nitrogen gas enters the catalyst cylinder 1 from the supply path 4 through the flow path 3a, contacts the catalyst such as Ni, and enters the main gas. The oxygen contained in the gas is captured, and then enters the adsorption column 2, where it comes into contact with an adsorbent such as synthetic zeolite, where carbon dioxide, water, etc. are adsorbed and removed, and the gas is purified to a high degree of purity. The purified gas coming out of the purification section A flows through the flow path 6a and the valve V3a.
, the purified gas is extracted through the filter S and the purified gas extraction path 7 while adjusting the flow rate with the flow rate control valve CVI, and is supplied to semiconductor manufacturing equipment and the like. During this time, residual hydrogen gas during regeneration and impurity gas gradually released from the pipe wall, etc., remain in the gas retention parts R1a, R2b, and R3 of the flow path branched from the purified gas flow path, and these are diffused. In order to prevent this from entering the purified gas flow path, a portion of the purified gas is purged from the retention section. Purge pipe Lla valve V7
By opening valve v8 of purge main pipe a and purge main pipe, purified gas is extracted through purge pipe Lla from retention part R1a, purge pipe L2b from retention part R2b, and purge pipe L3 from retention part R3. In this case, gas also remains in the purge pipe L2a, so L2a
Purging is also performed at the same time, and the purge amounts are respectively regulated by flow control valves CV4a, CV5a, CV5b and CV6, which are discharged from the discharge passage 5 via the main purge pipes.

By performing purging in this manner, impure gas in each retention section is discharged to the outside of the system, and intrusion of impure gas into the purified gas flow path is reliably prevented.

While the gas is purified in the purification section A, the catalyst and adsorbent are regenerated in the purification section B.

A valve V2b communicates with the regenerated exhaust gas discharge path 5 while heating the catalyst cylinder 1 and adsorption cylinder 2 of the refining section B, a valve V4b of the flow path 8b, and a valve v of the regeneration hydrogen gas supply path 10.
5 and purified self-gas supply path 11 for regeneration is opened, and the flow rate is adjusted by flow rate adjustment valves CV2 and Cv3, whereby hydrogen gas and purified self-gas are supplied from the supply path 9 to the flow path 6b and purification section B. By flowing through the adsorption cylinder 2, catalyst cylinder 1, flow path 3b and valve 2b and discharging into the discharge path 5, impurity gases adsorbed or captured by the adsorbent and catalyst are desorbed and removed. is played.

Next, when purification is performed in the purification section B, the gas is transferred to the purification section B by opening the valves Vlb and V3b.
and is purified via the purified gas extraction passage 7,
In this case, the purified gas is purged from the same purge pipe as in the purification in the purification part A, except that purging is performed from the purge pipe Llb instead of purge from the purge pipe Lla during purification in the purification part A.

In the present invention, the method for purging the purified gas may be continuous purging or intermittent purging, but it is ensured that impurity gas from the retention section is not mixed into the purified gas due to diffusion etc. Continuous purging is preferable from the viewpoint of preventing impurity gas from accumulating.The amount of purge varies depending on the size and shape of the branch piping that serves as the retention section, and cannot be unconditionally determined, but it is important to keep in mind that the amount of purging depends on the diameter and shape of the branch pipe that serves as the retention section. For example, if the inner diameter of the piping serving as the retention section is 5 cm or less and continuous purging is performed, the purge amount is 0.5 to 200 in linear velocity.
cm/sec, preferably 5-80CIl/
It is about .see. Furthermore, in order to reduce the amount of purge gas, it is also effective to increase the linear velocity of the gas by narrowing the diameter of the branch pipe near the connection part of the purge pipe to the purified gas flow path.

In the present invention, the purge mechanism provided in a gas retention area such as a branch path from a purified gas flow path is usually a combination of a purge pipe and a purge valve or orifice. Various on-off valves, flow control valves, needle valves, etc. are commonly used. A purge mechanism may be provided for each retention section to discharge the purge gas to the outside individually, but if hydrogen gas or harmful gases are present, these purge pipes may be installed as shown in Figure 1, for example. It is preferable to use a configuration in which the gas is collected in the main purge pipe and discharged together with the regenerated exhaust gas, etc., as described above.

Further, depending on the type of gas, the purge gas may be recycled to the raw material gas supply system via a pump or the like in order to further reduce gas loss due to purge.

Furthermore, since the moisture contained in the gas that is continuously purged in a steady state is not substantially different from the purified gas, it can also be introduced to the moisture meter as a sample gas and used for monitoring the dew point.

〔Effect of the invention〕

The present invention purges a small amount of refined gas from the gas retention area, thereby eliminating f.
l! It is possible to reliably prevent trace amounts of impurities from being mixed into the purified gas. Therefore, it has become possible to obtain various high-purity gases required for manufacturing semiconductors with a high degree of integration such as submicron scale.

〔Example〕

The inert gas purification device has the same configuration as shown in Fig. 1, with a purification section filled with 600cc of Nu-based catalyst (filling length 410mm) and 600cc of molecular sieve 5A (filling length 410mm) as an adsorbent, and a stainless steel purification unit. Nitrogen gas was purified using an apparatus in which the purified gas flow path had an inner diameter of 6 mm, the regeneration gas supply path had an inner diameter of 4 mm, and the purge pipe had an inner diameter of 2 mm.

First, after replacing the inside of the system with purified nitrogen gas, regeneration treatment was performed once for each purification section of each series. In addition, as a raw material gas, liquefied nitrogen gas is evaporated to room temperature, and then oxygen is added using a mast controller.
- each impurity component of carbon oxide and carbon dioxide is added, oxygen 2.7 ppm, - carbon oxide 1. lppm, carbon dioxide 0.9 ppm, and a dew point of -71 to -73°C was used.

The raw material nitrogen gas is supplied to the purification section A at a pressure of 5 Kgf/ctd-G, and the purified gas is supplied from the purified gas outlet passage at 15 kgf/ctd-G.
Purge pipes Lla and L are removed at the same time as 0ONl/h.
13.5 NI/h each from 3, purge pipe L2a
Purification was performed while purging purified gas from L2b and L2b at a rate of 31.2 NI/h, and the impurities and dew point in the purified gas were measured. Regarding the dew point,
Measurement was carried out using a capacitive moisture analyzer (manufactured by Panametrics) set in the W part of the purge main pipe shown in the figure, and for impurities, a part of the gas discharged from the produced gas extraction path 7 was guided to the analyzer. For oxygen, a Hershe IR oxygen analyzer (manufactured by Osaka Sanso Kogyo ■) was used, and for other components, an FID gas chromatograph was used. - Carbon oxide and carbon dioxide gas were extracted with methane by contacting with a Ni catalyst at 600°C in the presence of hydrogen. The sample was introduced into an f&FID (Flame Ionization Detector), which had been converted to a hydrogen flame ionization detector.

Purification sections A and B were switched every 24 hours, and while purification and regeneration were repeated alternately, purification of nitrogen gas was continued for 80 hours, and the purified gas was analyzed. Results first
Shown in the table.

Table 1 [Comparative Example] Nitrogen gas was purified in the same manner as in the example except that no purge mechanism was provided, using the same equipment as in the example. In this case, since there was no purge pipe, the moisture meter was set in the sampling pipe newly installed in the purified gas extraction path, and the results obtained are shown in Table 2.

Table 2

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of the high purity gas purification apparatus of the present invention. The drawing numbers are as follows. 1. Catalyst tube 2. Adsorption cylinders 3a, 3b, 6a, 6b, 8a and 8b, channels 4.9.10 and 11. Supply route 5. Discharge path 7, extraction paths A and B, purification sections Lla, Llb, L2a, L2b and L
3. Purge control, Purge control patent applicant: Japan Bionics Co., Ltd. Representative Patent attorney: Sadafumi Kobori

Claims (2)

[Claims] (1) In a high-purity gas purification method, the impurities contained in the gas are removed by passing the gas through a purification section, and the purified gas is extracted from the purification section via a purified gas flow path,
A method for purifying high-purity gas, comprising purging a part of the purified gas from a gas retention section existing in the purified gas flow path. (2) A gas purification section having a source gas inlet and a purified gas outlet, a piping system on the source gas supply side connected to the source gas inlet, and a purified gas extraction connected to the purified gas outlet A high-purity gas purification apparatus having a side piping system, characterized in that a purified gas purge mechanism is provided in a gas retention section in a purified gas flow path of the purified gas extraction side piping system. Gas purification equipment.