WO2018119836A1

WO2018119836A1 - Method of reducing argon content in hydrogen

Info

Publication number: WO2018119836A1
Application number: PCT/CN2016/112927
Authority: WO
Inventors: Kefeng SU; Stefan Brandes; Xingmin JIAO
Original assignee: Linde Ag
Priority date: 2016-12-29
Filing date: 2016-12-29
Publication date: 2018-07-05
Also published as: TW201840466A

Abstract

The present invention provides a method of reducing argon content in hydrogen. In particular, the method of reducing argon content in hydrogen which is obtained through methanol cracker and PSA, wherein an improvement of the method comprises: subjecting a feed stream comprising methanol to a stripper process using a stripper gas comprising nitrogen, a stripper gas comprising hydrogen, or a stripper gas comprising a mixture of hydrogen and nitrogen before the feed stream is introduced into the methanol cracker. In the present invention, the introduction of a stripper for the methanol feed may drastically reduce the argon to low enough levels such that in the downstream PSA unit, H2 can be produced which will meet the very high purity requirements with regard to argon, i. e., in a range of less than 70ppb by volume.

Description

METHOD OF REDUCING ARGON CONTENT IN HYDROGEN

TECHNICAL FIELD

The present invention relates to argon removal via stripped methanol cracker feed, particularly to a method of reducing argon content in hydrogen.

TECHNICAL BACKGROUND

Currently, the devices for the process of producing hydrogen generally comprises methanol and water tanks, mixing equipment (pumps and vessel) , feed pre-heater and vaporizer, (catalyst filled) reactor, synthesis gas cooling and condensate separation/recycle and final H₂ purification in a PSA (pressure swing adsorption) . The final H₂ product may be further compressed and filled into H₂ trailers or distributed via pipeline to the customer (s) . In methanol cracker plants (also referred to as methanol reformers) for H₂ (hydrogen) production, the methanol and water feed streams may get contaminated with argon, during production, handling/transportation and storage from argon contained in air or Ar impurities in the nitrogen used for purging and blanketing tanks, equipment etc.

With these argon traces brought into the methanol or water feed to the methanol cracking process, the argon will end up in the synthesis gas to the PSA. But the PSA process is known to be very inefficient (not capable) of removing Ar from the final hydrogen product down to the required low levels. A typical H₂ specification (in REA) is 99.999-99.9999 ％vol H₂ purity with CO, CO₂, CH₄ and moisture required <1ppmv. The balance is typically N₂ and argon.

In most recent years, electronic gas customers have expressed the requirement for very low argon levels (<70ppbv or <0.07ppmv) to cope with challenges in their production of semiconductors with EPI layers (Epitaxy layers) going from 16nm via 10nm (to 7nm) wafer technology.

However, the present technology does not remove (enough) argon from the H₂ product below the required levels for latest semiconductor production needs, or result in much higher product cost like for example modified water electrolysis or cryogenic adsorption, which are more costly to be competitive for industry scale applications.

A PSA may be operated in an extremely inefficient way (with low H₂ recovery) to mitigate the argon impurity. The adsorption technology has inherent limits tied to the adsorption isotherms, such that Argon can not be removed to extremely low levels. And the feed supply and handling system (s) can never fully avoid the ingress of argon into the methanol cracking (reforming) process.

Accordingly, there is a need to provide a novel process of producing hydrogen that can remove the argon reliably and effectively from the feed streams before sending them to the reactor and synthesis gas generation and finally reduce Ar content to less than 70ppb with less incremental cost.

SUMMARY

An objective of an exemplary embodiment of the present invention is to overcome the above and/or other deficiencies in the prior art. The inventors unexpectedly find a solution which may remove the argon reliably and effectively from the feed streams before sending them to the reactor and synthesis gas generation.

Thus, an exemplary embodiment of the present invention provides a method of reducing argon content in hydrogen which is obtained through methanol cracker and PSA, wherein an improvement of the method comprises:

subjecting a feed stream comprising methanol to a stripper process using a stripper gas comprising nitrogen, a stripper gas comprising hydrogen, or a stripper gas comprising a mixture of hydrogen and nitrogen before the feed stream is introduced into the methanol cracker.

In an exemplary embodiment of the present invention, the feed stream comprises a mixed feed of methanol and water.

In an exemplary embodiment of the present invention, the method further comprises:

subjecting a feed stream comprising water to a stripper process using a stripper gas comprising nitrogen before the feed stream is introduced into the methanol cracker.

In an exemplary embodiment of the present invention, the feed stream comprising methanol is blanketed by nitrogen before it is contacted with the stripper gas comprising nitrogen.

In an exemplary embodiment of the present invention, the stripper process is conducted at a temperature from 5℃ to 35℃, or at a temperature from 5℃ to ambient temperature.

In an exemplary embodiment of the present invention, the feed stream comprising water and the feed stream comprising methanol are fed into a stripper at same location.

In an exemplary embodiment of the present invention, the feed stream comprising water and the feed stream comprising methanol are fed into a stripper separately.

In an exemplary embodiment of the present invention, the method further comprises: using a stripper gas comprising hydrogen instead of the nitrogen stream or any mixture of both hydrogen and nitrogen stream for stripping can be used.

In an exemplary embodiment of the present invention, the nitrogen stream comprises argon content of less than 70ppm mol, or in a range of 1ppm mol to 50ppm mol.

In an exemplary embodiment of the present invention, the content of argon in hydrogen is in a range of less than 70ppb.

In an exemplary embodiment of the present invention, the content of argon in hydrogen is in a range of less than 70ppb； and the content of O₂ in hydrogen is in a range of less than 70ppb.

Other features and aspects will become apparent from the following Detailed Description, the Drawings and the Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be understood better in light of the description of exemplary embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram showing a method of hydrogen production which is obtained through methanol cracker and PSA in prior art；

FIG. 2 is a schematic diagram showing an exemplary embodiment of the stripper process using a stripper gas comprising nitrogen before the feed stream is introduced into the methanol cracker (as shown in FIG. 1) in present invention；

FIG. 3 is a schematic diagram showing another exemplary embodiment of the stripper process using a stripper gas comprising hydrogen before the feed stream is introduced into the methanol cracker (as shown in FIG. 1) in present invention；

DETAILED DESCRIPTION

Hereafter, a detailed description will be given for preferred embodiments of the present disclosure. It should be pointed out that in the detailed description of the embodiments, for simplicity and conciseness, it is impossible for the Description to describe all the features of the practical embodiments in details. It should be understood that in the process of a practical implementation of any embodiment, just as in the process of an engineering project or a designing project, in order to achieve a specific goal of the developer and in order to satisfy some system-related or business-related constraints, a variety of decisions will usually be made, which will also be varied from one embodiment to another. In addition, it can also be understood that although the effort made in such developing process may be complex and time-consuming, some variations such as design, manufacture and production on the basis of the technical contents disclosed in the disclosure are just customary technical means in the art for those of ordinary skilled in the art associated with the contents disclosed in the present disclosure, which should not be regarded as insufficient disclosure of the present disclosure.

Unless defined otherwise, all the technical or scientific terms used in the Claims and the Description should have the same meanings as commonly understood by one of ordinary skilled in the art to which the present disclosure belongs. The terms “a” , “an” and the like do not denote a limitation of quantity, but denote the existence of at least one. The terms “comprises” , “comprising” , “includes” , “including” and the like mean that the element or object in front of the “comprises” , “comprising” , “includes” and “including” covers the elements or objects and their equivalents illustrated following the “comprises” , “comprising” , “includes” and “including” , but do not exclude other elements or objects.

In the present invention, the inventors find that Ar solubility in methanol is more than that in water. Thus, the reduction of argon content in methanol is critical to reduce argon content in final hydrogen product which is obtained through methanol cracker and PSA. On the other hand, the inventors find that, Ar content in nitrogen is much less than in Air. For nitrogen gas typically generated from cryogenic air separation process, Ar content is less than 70 ppm (mol) while Ar content in Air is 0.934％ (mol) . Therefore in a certain temperature and a certain pressure, Ar partial pressure in nitrogen gas is less than 0.75％of that in Air, consequently Ar solubility in methanol and water can drop significantly via contacting with nitrogen gas..

Therefore, the inventors surprisingly find that the introduction of a stripper using a stripper nitrogen for the methanol/water mixed feed may drastically reduce the argon in the methanol/water mixed feed to low enough levels such that in the downstream PSA unit, H₂ can be produced which will meet the very high purity requirements with regard to argon.

In one embodiment of the present invention, the method of reducing argon content in hydrogen which is obtained through methanol cracker and PSA, wherein an improvement of the method comprises: subjecting a feed stream comprising methanol to a stripper process using a stripper gas comprising nitrogen before the feed stream is introduced into the methanol cracker. In order to reduce both Ar content and O₂ content in hydrogen product, the feed stream which is subjected to a stripper process may comprise a mixed feed of methanol and water.

In the present invention, the feed stream comprising methanol may be commercially available from Linde AG or external venders and stored in a methanol tank for use. In preferred embodiment, the feed stream comprising methanol is blanketed by nitrogen before use. As above described, Ar content in process gas (PSA inlet) varies remarkably mainly due to variation in methanol feed, and contamination resource is from upstream storage and transportation, thus fresh methanol feed contains highest Ar content. After some days storage with the methanol feed being blanketed by nitrogen with low Ar content, Ar content in the methanol feed for MC and PSA inlet gas is much lower, since Ar in methanol would approach equilibrium with 70ppm Ar in nitrogen gas at 0.3 bar and ambient temperature. Ar content in process gas can drop near 70ppb.

In one embodiment of the present invention, the stripper process of the present invention may be conducted at ambient temperature. In particular, the stripper process of the present invention may be conducted in a temperature from 0℃ to 50℃, a temperature from 5℃ to 45℃, a temperature from 5℃ to 35℃, a temperature from 10℃ to 45℃, a temperature from 10℃ to 35℃, a temperature from 15℃ to 25℃, a temperature from 5℃ to ambient temperature or all ranges and sub-ranges therebetween.

In one embodiment of the present invention, the feed stream comprising water and the feed stream comprising methanol are fed into a stripper at same location. In a certain embodiment, the feed stream comprising water may be introduced into a pipe for introducing the feed stream comprising methanol, then the feed stream comprising water and the feed stream comprising methanol are fed into a stripper together.

In one embodiment of the present invention, the feed stream comprising water and the feed stream comprising methanol may be fed into a stripper separately. In a preferred embodiment, the feed stream comprising water may be fed into the stripper from top of the stripper. Alternatively, the feed stream comprising water may be fed into the stripper at a location which is above where the feed stream comprising methanol is fed into a stripper.

In one embodiment of the present invention, the method of reducing argon content in hydrogen which is obtained through methanol cracker and PSA may comprises: subjecting a feed stream comprising methanol to a stripper process using a stripper gas comprising hydrogen, instead of nitrogen, before the feed stream is introduced into the methanol cracker. In a preferred embodiment, the method of reducing argon content in hydrogen may further comprises: subjecting a feed stream comprising methanol to a stripper process using a stripper gas comprising hydrogen before the feed stream is introduced into the methanol cracker. In a more preferred embodiment, the method of reducing argon content in hydrogen may further comprise: recycling at least a portion of hydrogen exiting from the PSA into the nitrogen stream.

In one embodiment of the present invention, the nitrogen stream may comprise low argon content, such as argon content of less than 70ppm mol, in a range of 1ppm mol to 50ppm mol, in a range of 5ppm mol to 50ppm mol, in a range of 10ppm mol to 40ppm mol, in a range of 20ppm mol to 35ppm mol, or all ranges and sub-ranges therebetween.

In comparison with the prior art, the inventors surprisingly find that in the present invention, the introduction of a stripper for the methanol/water mixed feed may drastically reduce the argon in the methanol/water mixed feed to low enough levels such that in the downstream PSA unit, H₂ can be produced which will meet the very high purity requirements with regard to argon (the content of argon in hydrogen is in a range of less than 70ppb by volume) .

Further, the incremental cost as brought by the stripper process in the present invention is much lower than the existing technologies which use methanol cracker technology as basis and can reduce Ar to below 70 ppb, for example, the addition of cryo-TSA downstream MC (methanol cracker and PSA) or modified water electrolyzer instead of MC..

The method in the present invention is significantly more economic (cost effective) compared to alternatives where cryogenic purifiers, palladium membranes and etc are used for H₂ purification. The use of modified water electrolysers results also in significantly higher H₂ cost, caused by the relatively high price for electric power compared to fuels such as methanol (or natural gas) .

NG (natural gas) based steam reformers (SMR) have also experienced tremendous problems (high operating losses ＝ high cost) especially in Taiwan and China, where the natural gas feed is also contaminated with argon traces (in the ppm range, typically 30-60 ppmv in NG) . The PSA process after the SMR does also not meet the H₂ specification with respect to argon, unless the process is operated very inefficient (i.e. 30-40％loss of product) . Since it is very difficult (economically not competitive with any known technology) to separate argon from NG, a hydrogen production for electronic gas customers from argon contaminated NG using SMR technology is not an alternative for new installations. Existing SMR plants may continue to operate with very low recovery and high losses.

Furthermore, if in the (near) future –with even thinner semiconductor layers -the argon specification in H₂ becomes more stringent (i.e. <10ppbv) , then NG-SMR (Natrual Gas-Steam Methane Reformer followed by PSA) based hydrogen is no longer an option and will not work at all in case argon traces are contained in NG. The problem of Ar in NG may also be a result of increasing number of LNG plants/terminal around the world. NG distributors may use nitrogen to adjust the heating value of the (evaporated) LNG in order to meet the NG pipeline specification. But the N₂ used for heating value adjustment is often no high purity N₂ but contains also argon. However, by using the method described in the present invention, the content of argon in hydrogen may even be reduced to a range of less than 70ppb, less than 60ppb, less than 50ppb, less than 40ppb, less than 30ppb, less than 20ppb, less than 10ppb, less than 5ppb, or less than 1ppb.

In one embodiment of the present invention, the content of argon in hydrogen is in a range from 1ppb to 70ppb, from 5ppb to 70ppb, from 10ppb to 70ppb, from 20ppb to 70ppb, from 30ppb to 70ppb, from 40ppb to 70ppb, from 50ppb to 70ppb, from 60ppb to 70ppb, from 1ppb to 60ppb, from 1ppb to 50ppb, from 1ppb to 40ppb, from 1ppb to 30ppb, from 5ppb to 60ppb, from 5ppb to 50ppb, from 5ppb to 40ppb, from 5ppb to 30ppb, from 10ppb to 60ppb, from 10ppb to 50ppb, from 10ppb to 40ppb, from 10ppb to 30ppb, and all ranges and sub-ranges therebetween.

In one embodiment of the present invention, the content of O₂ in hydrogen is in a range from 1ppb to 70ppb, from 5ppb to 70ppb, from 10ppb to 70ppb, from 20ppb to 70ppb, from 30ppb to 70ppb, from 40ppb to 70ppb, from 50ppb to 70ppb, from 60ppb to 70ppb, from 1ppb to 60ppb, from 1ppb to 50ppb, from 1ppb to 40ppb, from 1ppb to 30ppb, from 5ppb to 60ppb, from 5ppb to 50ppb, from 5ppb to 40ppb, from 5ppb to 30ppb, from 10ppb to 60ppb, from 10ppb to 50ppb, from 10ppb to 40ppb, from 10ppb to 30ppb, and all ranges and sub-ranges therebetween.

Generally, a process of producing hydrogen via methanol cracker and PSA may comprise: (1) introducing a feed comprising methanol into a methanol cracker to form a mixed gas mainly comprising hydrogen, CO, CH₄, and some heavy components including side product such as dimethyl ether； and (2) introducing the mixed gas into PSA unit to provide hydrogen product. In some embodiments (as shown in Fig. 1) , a water (a demineralized water or deionized water) feed from a demineralized water tank is mixed with a methanol feed from a methanol tank to provide a mixed feed of methanol and water, then the mixed feed of methanol and water is introduced into a tank or degasser, e.g., a recycle drum. The methanol feed may be provided by external vender and Linde itself. The mixed feed as degassed or not is then introduced into a methanol cracker, to provide a mixed gas comprising hydrogen. After passing through a water cooler, a condensator (e.g., condensate drum) , the mixed gas is introduced into PAS unit, so as to provide H₂ product. The details regarding common preparation of H₂ product via methanol cracker and PSA are known in the prior art, which may be incorporated herein by reference.

In one embodiment of the present invention, a method of removing/reducing content of argon in hydrogen which is obtained through methanol cracker and PSA is provided. In the inventive method, it comprises an improvement, in which before a feed stream comprising methanol is introduced into the methanol cracker, the feed stream is firstly subjected to a stripper process using a stripper gas comprising nitrogen. In some embodiments, the stripper gas may also comprise hydrogen.

In some embodiments, the feed stream may comprise a mixed feed of methanol and water. In some embodiments, the methanol and water may be mixed and fed into a stripper at same location. In other embodiments, the methanol and water may be fed separately into a stripper, where the water is fed into a stripper separately from top of the stripper, or the water is fed at a location which is above the location where the methanol is fed into the stripper (as shown in Fig. 3) .

As shown in Fig. 2, a water (a demineralized water or deionized water) feed is mixed with a methanol feed to provide a mixed feed of methanol and water. Then, the mixed feed of methanol and water is introduced into a stripper. In some embodiments, the stripper may also comprise a recycle drum as commonly used, with the stripper column being located above the recycle drum and in fluid comunication with the recycle drum. In stripper, a stripper gas, e.g., nitrogen, is introduced at a location below the trays of stripper, and the mixed feed of methanol and water is introduced at a location upper the trays of stripper. After exiting from the stripper, the mixed feed of methanol and water is then introduced into a methanol cracker, to provide a mixed gas comprising hydrogen as shown in Fig. 1, so as to provide H₂ product with high purity. In some embodiments, the content of argon in hydrogen product is in a range of less than 70ppb by volume. In some preferred embodiments, the content of argon in hydrogen is in a range of less than 70ppb by volume； and the content of O₂ in hydrogen is in a range of less than 70ppb by volume.

In some embodiments, the method of the present invention may further comprise: recycling at least a portion of hydrogen exiting from the PSA unit into the stripper, preferably into the nitrogen stream. In Particular, the at least a portion of hydrogen and the nitrogen stream are introduced at a location below the trays of stripper, or introduced into a recycle drum which is located below the stripper. In some furhter embodiments, the feed stream may comprise a mixed feed of methanol and water. In some furhter embodiments, the methanol and water may be mixed and fed into a stripper at same location. In other embodiments, the methanol and water may be fed separately into a stripper, where the water is fed into a stripper separately from top of the stripper, or the water is fed at a location which is above the location where the methanol is fed into the stripper (as shown in Fig. 3) .

As shown in Fig. 3, a methanol feed is introduced into the stripper at a location above the trays of stripper, and a water (a demineralized water or deionized water) feed is introduced into a stripper at a location above the trays of stripper and a location where a methanol feed is introduced into the stripper. In some embodiments, the stripper may also comprise a recycle drum as commonly used, with the stripper column being located above the recycle drum and in fluid comunication with the recycle drum. In stripper, a nitrogen stripper gas is introduced at a location below the trays of stripper. After exiting from the stripper, the mixed feed of methanol and water is then introduced into a methanol cracker, to provide a mixed gas comprising hydrogenas shown in Fig. 1, so as to provide H₂ product with high purity. In Fig. 3, at least a portion of hydrogen is provided to the stripper at a location below the trays of stripper, or to the recycle drum which is located below the stripper.

In some embodiments, the content of argon in hydrogen product is in a range of less than 70ppb by volume. In some preferred embodiments, the content of argon in hydrogen is in a range of less than 70ppb by volume； and the content of O₂ in hydrogen is in a range of less than 70ppb by volume.

In the present invention, the nitrogen (N₂) stream used for stripper must meet a certain purity (low argon content) , such that argon will be effectively stripped from the stripper column located above the recycle drum. In the present invention, the Nitrogen stream is commercially available from LINDE AG or other qualified vendors, which is easy to ensure the required utility (nitrogen) specifications. In some embodiments, the nitrogen stream comprises low argon content, such as argon content of less than 70ppm mol, in a range of 1ppm mol to 50ppm mol, in a range of 5ppm mol to 50ppm mol, in a range of 10ppm mol to 40ppm mol, in a range of 20ppm mol to 35ppm mol, or all ranges and sub-ranges therebetween.

In some embodiments, the stripper process of the present invention may be conducted at ambient temperature. In particular, the stripper process of the present invention may be conducted in a temperature from 0℃ to 50℃, a temperature from 5℃ to 45℃, a temperature from 5℃ to 35℃, a temperature from 10℃ to 45℃, a temperature from 10℃ to 35℃, a temperature from 15℃ to 25℃, a temperature from 5℃ to ambient temperature or all ranges and sub-ranges therebetween.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about, ” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.

Example 1

A methanol feed from external vender is released from a truck to a methanol tank, wherein the methanol feed from truck has a flow of 25500 kmol/hr with Ar content of 101.0 mol/hr. In this methanol feed, Ar content is 3.9 ppm (mol) at 15℃ and 1.01bar. Also, Ar content in Air is 0.85％by volume. In methanol tank, the methanol feed has Ar content of 1.07 mol/hr. In this methanol feed, Ar content is 0.04 ppm (mol) at 15℃ and 1.31bar. In the methanol tank, the methanol feed is blanketed by nitrogen with low Ar content, whereby Ar content in nitrogen is 70ppm by volume.

A water feed is introduced from a plant to a water tank. The water from a plant has a flow of 23400 kmol/hr with Ar content of 7.60 mol/hr. In this methanol feed, Ar content is 0.32 ppm (mol) at 15℃ and 1.01bar. Also, Ar content in Air is 0.92％by volume. In water tank, the water feed has Ar content of 7.60 mol/hr. In this water feed, Ar content is 0.32 ppm (mol) . As stated in the present invention, the methanol feed and water feed are introduced into a nitrogen stripper at a temperature of 15℃ and a pressure of 1.31 bar. From an outlet of the stripper, a mixed feed is introduced into a methanol cracker, with Ar content of 0.64 mol/hr. Finally, a PSA feed gas in a flow of 100000kmol/hr has extremely low Ar content, i.e., 0.006 ppm (mol) .

In this Example, it is found that the final hydrogen product will have an extremely low Ar content, which meets the requirements of tighter Ar impurity in hydrogen of less than 70ppb. In this example, the hydrogen product will have Ar content of less than 0.006 ppm (mol) or 6ppb (mol) .

The above descriptions are merely embodiments of the invention and are not intended to restrict the scope of the invention. All kinds of variations and modifications could be made to the present invention to those skilled in the art. Any modifications, alternatives and improvements made within the spirit and principles of the present invention shall fall within the scope of the appended claims.

Claims

A method of reducing argon content in hydrogen which is obtained through methanol cracker and PSA, wherein an improvement of the method comprises:

subjecting a feed stream comprising methanol to a stripper process using a stripper gas comprising nitrogen, a stripper gas comprising hydrogen, or a stripper gas comprising a mixture of hydrogen and nitrogen before the feed stream is introduced into the methanol cracker.
The method according to claim 1, wherein the feed stream comprises a mixed feed of methanol and water.
The method according to claim 1, wherein the method further comprises:

subjecting a feed stream comprising water to a stripper process using a stripper gas comprising nitrogen before the feed stream is introduced into the methanol cracker.
The method according to claim 1, wherein the feed stream comprising methanol is blanketed by nitrogen before it is contacted with the stripper gas comprising nitrogen.
The method according to anyone of claims 1-4, wherein the stripper process is conducted at a temperature from 5℃ to 35℃, or at a temperature from 5℃ to ambient temperature.
The method according to claim 3, wherein the feed stream comprising water and the feed stream comprising methanol are fed into a stripper at same location.
The method according to claim 3, wherein the feed stream comprising water and the feed stream comprising methanol are fed into a stripper separately.
The method according to anyone of claims 1-4, wherein the nitrogen stream comprises argon content of less than 70ppm mol, or in a range of 1ppm mol to 50ppm mol.
The method according to claim 1, wherein the content of argon in hydrogen is in a range of less than 70ppb.
The method according to claim 2, wherein the content of argon in hydrogen is in a range of less than 70ppb； and the content of O₂ in hydrogen is in a range of less than 70ppb.