JP7667538B2 - High-purity nitrogen supply system and gas chromatograph analysis system - Google Patents

Description

The present invention relates to a high purity nitrogen supply system and a gas chromatograph analysis system .

As a method for producing high-purity nitrogen, the purification of nitrogen gas by membrane separation of oxygen from compressed air by the PSA method is common. In nitrogen gas purified by PSA (referred to as "raw gas"), methane, which is a component lighter than nitrogen, cannot be removed due to the characteristics of membrane separation. Similarly, helium, hydrogen, etc. remain, but helium is always inactive in a gas chromatography detector and does not pose a problem. On the other hand, methane has an extremely low boiling point and cannot be captured even at liquid nitrogen temperature. In addition, since it has no polarity, it cannot be removed by adsorption. Therefore, at present, the most reasonable way to steadily remove methane is to convert it to _CO2 by combustion.

For example, Patent Document 1 (Patent No. 5852422) discloses a technique for combusting methane in an organic matter combustion catalyst tube in an ultra-high purity nitrogen purification method using compressed air. The specific principle is as follows. That is, since the raw gas is nitrogen gas from which oxygen has been removed to the maximum extent possible, the inside of the organic matter combustion catalyst tube is essentially in an oxygen-deficient state, and methane cannot be completely burned. By placing a platinum catalyst supported on alumina ( _aluminum oxide _Al2O3 ) in the combustion tube, the oxygen contained in the alumina reacts with methane, and the combustion reaction proceeds according to the following formula (1).
3CH ₄ +4Al ₂ O ₃ → 3CO ₂ +6H ₂ O+8AL...Formula (1)
In the above reaction, three moles of methane are oxidized by four moles of alumina (aluminum oxide) to carbon dioxide (CO ₂ ) and water (H ₂ O), and reduced aluminum is produced.
Furthermore, Patent Document 2 (Japanese Patent No. 3325805) discloses a technique in which impurity hydrocarbons are converted into carbon dioxide and water using a catalyst, and then removed by cooling.

Patent No. 5852422 Patent No. 3325805

In the technology disclosed in Patent Document 1, if the above combustion reaction process continues, eventually the alumina will be consumed and the catalytic function will be lost. Naturally, when the catalytic function is lost or combustion is insufficient, nitrogen gas will be discharged from which the methane has not been completely removed. In other words, there is a problem that the analysis by the gas chromatograph into which the nitrogen gas is discharged becomes inaccurate, and there has been a demand for technology that can continuously purify ultra-high purity nitrogen gas from which the methane has been removed.

The present invention aims to provide a technology that enables continuous and appropriate methane removal when producing high-purity nitrogen gas.

The methane removal device of the present invention comprises: a catalyst having a metal oxide support, which is adapted to pass nitrogen gas from which oxygen has been separated and combust and remove methane gas remaining in the nitrogen gas;
A catalyst function recovery means for restoring the function of the catalyst by passing oxygen through the catalyst;
Equipped with.

The high purity nitrogen supply system of the present invention comprises the above-mentioned methane removal device,
a nitrogen generator for supplying the nitrogen gas to the methane removal device;
a residual component removal device that obtains the nitrogen gas from which the methane gas has been removed by the methane removal device and removes at least water and carbon dioxide from the nitrogen gas;
Equipped with.

The gas chromatograph analysis system of the present invention comprises the above-mentioned high-purity nitrogen supply system,
a gas chromatograph that receives nitrogen gas from the high-purity nitrogen supply system;
A gas chromatographic analysis system comprising:

The catalyst function regeneration method of the present invention includes a nitrogen purification device that separates oxygen from air to purify nitrogen gas,
a residual methane removal device having a catalyst supported by a metal oxide, which combusts and removes methane remaining in the nitrogen gas purified by the nitrogen purification device, the method for regenerating the catalytic function of the catalyst being carried out in a high-purity nitrogen supply system,
When the nitrogen gas is not being passed through the catalyst, a gas containing oxygen is passed through the catalyst to regenerate the catalytic function of the catalyst.

The present invention makes it possible to realize a technology that enables continuous and appropriate methane removal when producing high-purity nitrogen gas.

1 is a block diagram showing a schematic configuration of a gas chromatograph analysis system according to an embodiment. 1 is a block diagram showing a schematic configuration of a high-purity nitrogen supply system according to an embodiment. FIG. 4 is a flowchart of a catalyst function recovery process performed by the high-purity nitrogen supply system according to the embodiment. 4 is a flowchart of a catalytic function regeneration process of a catalyst in a residual methane removal device according to an embodiment. FIG. 1 is a diagram showing a gas chromatograph (three-component simultaneous analysis device) according to an embodiment of the present invention.

<Overview of the embodiment>
The outline of the embodiment is as follows.
In this embodiment, the nitrogen gas obtained by separating oxygen from compressed air in a high-purity nitrogen supply system is purified to a high purity and supplied to a gas chromatograph. At this time, residual methane in the nitrogen gas is burned and removed by a catalyst having a metal oxide. This allows stable use of methane-free nitrogen as a carrier gas in the gas chromatograph.
The metal oxide may be aluminum oxide (alumina), copper oxide, or titanium oxide. Taking into consideration the balance between cost, availability on the market, and catalytic ability, the following describes an example of a catalyst using aluminum oxide as the metal oxide, i.e., a platinum catalyst supported on an alumina carrier.
For the platinum catalyst on the alumina carrier that has been consumed for methane combustion under conditions of oxygen deficiency due to oxygen separation, a flow path switching valve is controlled to pass a gas containing at least oxygen, such as compressed dry air, through the deteriorated catalyst during the time period when the catalyst is separated from the carrier gas flow for the gas chromatograph, thereby restoring the methane combustion function of the catalyst.
The specific details will be explained below.

<Gas chromatograph analysis system 100>
FIG. 1 is a block diagram showing a schematic configuration of a gas chromatograph analysis system 100 according to the present embodiment. The gas chromatograph analysis system 100 includes a high-purity nitrogen supply system 1 and a gas chromatograph 2. The high-purity nitrogen supply system 1 purifies nitrogen gas obtained by separating oxygen from compressed air to a high purity and supplies the purified nitrogen gas to the gas chromatograph 2. At this time, residual methane in the nitrogen gas is burned and removed. The gas chromatograph 2 obtains methane-free high-purity nitrogen gas (nitrogen carrier gas). When the gas chromatograph 2 is a three-component simultaneous analysis device described later in FIG. 5, it is preferable to supply methane-free high-purity nitrogen gas by the high-purity nitrogen supply system 1 according to the present embodiment.

<Overview of high purity nitrogen supply system 1>
The high purity nitrogen supply system 1 includes a nitrogen supply device 10, a catalyst function recovery device 20, and a control device 30 (control means). The control device 30 controls the operations of the nitrogen supply device 10 and the catalyst function recovery device 20.

The nitrogen supply device 10 separates and removes oxygen from atmospheric air, removes impurities through catalytic combustion and filtering, and purifies high-purity nitrogen gas, which it supplies to the gas chromatograph 2.

The catalyst function recovery device 20 recovers the catalytic combustion function (hereinafter referred to as "catalytic function") in the residual methane removal device 12 (described later in FIG. 2) provided in the nitrogen supply device 10. Specifically, the catalyst function recovery device 20 has a function of supplying compressed air to the residual methane removal device 12. The supply of compressed air to the residual methane removal device 12 is performed at a predetermined timing and for a predetermined period of time under the control of the control device 30. Details will be described later.

As a result, for the catalyst 121 (described later in FIG. 2 ) of the residual methane removal device 12, when the catalyst 121 is separated from the carrier gas flow for the gas chromatograph 2 by a flow path switching valve or the like under the control of the control device 30, a gas containing at least oxygen, such as compressed dry air, is ventilated through the deteriorated catalyst 121, thereby restoring the methane catalytic function of the catalyst 121.
The catalyst function recovery device 20 may be provided as a separate component from the residual methane removal device 12, or the residual methane removal device 12 may include the catalyst function recovery device 20.

<Specific Configuration of Nitrogen Supply Device 10>
Fig. 2 shows a specific configuration of the nitrogen supplying device 10. Fig. 3 shows a flow chart of the high purity nitrogen purification process in the nitrogen supplying device 10. Note that, for example, the technology described in the above Patent Document 1 (Patent No. 5852422) can be applied to the nitrogen supplying device 10. In addition, as explained in the background art, methane remains in nitrogen gas purified by the PSA method and there is a demand for removing it, so the present invention can also be applied to a nitrogen supplying device for the PSA method. The configuration to which the technology of Patent Document 1 is applied will be briefly explained below.

The nitrogen supply device 10 comprises, from upstream to downstream, a nitrogen generator 11, a residual methane remover 12, and a moisture/carbon dioxide remover 13 (residual component remover).

The nitrogen generator 11 performs an air compression process (S101), a moisture removal process (S102), an oil removal process (S103), a dry air purification process (S104), a trace organic matter removal process (S105), and an oxygen removal process (S106) as high-purity nitrogen purification processes. As a result, nitrogen and oxygen are separated, and high-purity nitrogen gas is discharged to the residual methane removal device 12.
The residual methane remover 12 removes methane contained in the high-purity nitrogen gas obtained from the nitrogen generator 11 by combustion in a methane removal step (S107).
The moisture and carbon dioxide removal device 13 removes moisture and carbon dioxide contained in the high-purity nitrogen gas obtained after the methane removal step (S107) in the residual methane removal device 12 through a moisture and carbon dioxide removal process (S108).
The configurations of the nitrogen generation device 11, the residual methane removal device 12, and the moisture and carbon dioxide removal device 13 and each of the steps (S101 to S108) therein will be specifically described below.

(Air compression process: S101)
In the nitrogen generator 11, a compressor is used as an air compression process to compress indoor air to 5 to 8 atmospheres. Any compressor can be used as long as it can compress air to 5 to 8 atmospheres, but an oil-free compressor is preferable to avoid the inclusion of oil mist.

The compressed air is subjected to the following processes, and due to the pressure of the compressed air, the air is automatically sent from one process to the next simply by connecting the vent pipe. As the vent pipe for the compressed air, it is preferable to use a stainless steel or polytetrafluoroethylene pipe with an outer diameter of 3 mm to 10 mm in order to prevent impurities from remaining and to cool the gas after the heating process in the catalyst 121, etc., and it is even more preferable to use 316 stainless steel.

(Moisture removal step: S102)
The nitrogen generator 11 removes moisture from the compressed air by using a moisture trap. The moisture trap is capable of removing dust particles up to 5 μm in size, and preferably has a polypropylene element with a filtration rating of 0.50 μm or less, and is particularly preferably the F3000 type manufactured by CKD Corporation. When using such a moisture trap, it is preferable to use two stages in series.

(Oil removal process: S103)
The nitrogen generator 11 uses an oil mist trap to remove oil from the compressed air from which moisture has been roughly removed in the moisture removal step (S102). The oil mist trap used in this process has the function of removing oil to 0.01 mg/ ^m3 or less, and is preferably equipped with a fiber filter with a filtration rating of 0.01 μm or less, and is particularly preferably the M3000 type manufactured by CKD Corporation. The moisture removal step (S102) and the oil removal step (S103) may be performed in different processing steps.

(Dry air purification step: S104)
The nitrogen generator 11 purifies the compressed air from which moisture and oil have been removed in the moisture removal step (S102) and the oil removal step (S103) by using a tube with a built-in water separation membrane to produce dry air. The water separation membrane used here is capable of further removing moisture from the compressed air to an outlet air dew point of −30° C. or less, and is preferably equipped with an aromatic polyimide hollow fiber membrane having a pore size of 450 to 550 μm, and among these, the product name UMS-B2V manufactured by Ube Industries is particularly preferred.

(Trace organic matter removal step: S105)
The nitrogen generator 11 uses a hydrocarbon removal tube to adsorb and remove trace amounts of remaining organic matter from the dry air having an outlet air dew point of −30° C. or less that has been purified in the dry air purification step (S104). The hydrocarbon removal tube used here is a hydrocarbon removal tube that is filled with granular activated carbon having a diameter of 2 to 6 mm and adsorbs and removes trace amounts of remaining organic matter, and among these, the product manufactured by Shimadzu Corporation under the product name 221-05619-01 is particularly preferred.

(Oxygen removal step: S106)
The nitrogen generator 11 removes oxygen from the dry air from which the trace amount of remaining organic matter has been adsorbed and removed in the trace amount of organic matter removal step (S105) by using a tube with an oxygen/nitrogen separation membrane built in. The tube with an oxygen/nitrogen separation membrane used here is equipped with a hollow fiber separation membrane made of polyimide with a pore size of 450 to 550 μm, and among these, the one manufactured by Ube Industries, Ltd. under the product name: UBE NM-B01A is particularly preferred.

(Iterative process)
The nitrogen generator 11 repeats at least the trace organic matter removal step (S105) and the oxygen removal step (S106) on the compressed air that has been treated in the oxygen removal step (S106). Through the above processes, the nitrogen generator 11 obtains air (raw gas) with a nitrogen purity of 99.999% and discharges the raw gas to the residual methane removal device 12.

It is preferable to attach an oxygen indicator capable of detecting 1 ppm of oxygen to the latter process of the trace organic matter removal process (S105) or the oxygen removal process (S106). If the filter of the oxygen indicator does not discolor, it can be recognized that the oxygen concentration in the refined nitrogen gas is 1 ppm or less.

By connecting the above-mentioned processes in series, it is possible to obtain high-purity purified nitrogen of 99.9999% or more. Furthermore, the air after completion of this process can be directly supplied to the gas chromatograph 2 or the like at 200 to 400 kPa. However, when methane removal is performed as in this embodiment, a methane removal step (S107) and a moisture/carbon dioxide removal process (S108) are also performed.
Of the major components in the atmosphere, argon is an element and therefore in principle cannot be removed by chemical reaction. However, in gas chromatography, this does not affect the detection sensitivity.

(Methane removal step: S107)
The methane removal step (S107) in the residual methane removal device 12 will be described.
The residual methane removal device 12 uses an organic matter combustion catalyst tube to burn and remove hydrocarbons (more specifically, methane) from the air discharged from the nitrogen generation device 11 after the oxygen removal step (S106), i.e., the raw gas with a nitrogen purity of 99.999%, and discharges the resulting gas to the moisture and carbon dioxide removal device 13.

The organic matter combustion catalyst tube used here is a combustion tube filled with an alumina-treated platinum catalyst (catalyst 121) with a particle size of 1 to 3 mm, and among them, GL Science's product name: AOE-2300 is particularly preferred. The air from which the hydrocarbons have been burned and removed by this process contains carbon dioxide and moisture generated by the combustion.
As mentioned above, the raw gas is nitrogen gas (purity 99.999%) from which oxygen has been removed to the maximum extent possible, so the organic matter combustion catalyst tube is essentially in an oxygen-deficient state and cannot completely burn methane. By equipping the organic matter combustion catalyst tube with a platinum catalyst supported on alumina ( _aluminum oxide _Al2O3 ) as catalyst 121 inside, the oxygen contained in the alumina reacts with methane, and the combustion reaction proceeds according to the following formula (1).
3CH ₄ +4Al ₂ O ₃ → 3CO ₂ +6H ₂ O+8AL...Formula (1)
In the above reaction, three moles of methane are oxidized by four moles of alumina (aluminum oxide) to carbon dioxide (CO ₂ ) and water (H ₂ O), and reduced aluminum is produced.

(Moisture and carbon dioxide removal process S108)
The moisture and carbon dioxide removal process (S108) in the moisture and carbon dioxide removal device 13 will be described.
The moisture and carbon dioxide removal device 13 removes water and carbon dioxide that are mainly generated in conjunction with the combustion of methane from the nitrogen gas from which methane has been completely combusted and removed in the residual methane removal device 12 (catalyst 121).

(Specific configuration example of moisture/carbon dioxide removal device 13)
Specifically, the moisture/carbon dioxide removal device 13 includes, in order from the upstream side, a moisture removal device 131, a large-capacity activated carbon (A) 132, a gas filter (moisture) 133, a gas filter (oxygen) 134, a carbon dioxide removal filter 135, and a large-capacity activated carbon (B) 136.

(Moisture removal device 131)
The moisture removal device 131 is, for example, a moisture absorbent tube, which obtains the nitrogen gas discharged from the residual methane removal device 12, adsorbs organic matter (CO2) and moisture in the nitrogen gas, and discharges it to the large-capacity activated carbon (A) 132. An example of the moisture removal device 131 is a Shimadzu Gas Filter (MS5A) manufactured by Shimadzu Corporation.

(Large capacity activated carbon (A) 132)
The large-capacity activated carbon (A) 132 removes hydrocarbons from the nitrogen gas discharged from the moisture remover 131, and discharges the gas to a moisture/oxygen remover 133 and a moisture/carbon dioxide remover (B) 133. For example, the large-capacity activated carbon (A) 132 is a large-scale hydrocarbon trap manufactured by GL Sciences.

(Gas filter (moisture) 133)
The gas filter (moisture) 133 removes moisture from the nitrogen gas discharged from the large-capacity activated carbon (A) 132, and discharges it to the gas filter (oxygen) 134. As the gas filter (moisture) 133, for example, there is a product manufactured by GL Sciences, Inc., under the trade name of Super Clean Gas Filter (moisture filter, with indicator).

(Gas filter (oxygen) 134)
The gas filter (oxygen) 134 removes oxygen from the nitrogen gas discharged from the gas filter (moisture) 133, and discharges the gas to a carbon dioxide removal device 135. An example of the gas filter (oxygen) 134 is a product manufactured by GL Sciences, Inc., under the trade name of Super Clean Gas Filter (oxygen filter, with indicator).

(Carbon Dioxide Removal Device 135)
The carbon dioxide remover 135 removes carbon dioxide from the nitrogen gas discharged from the gas filter (oxygen) 134, and discharges it to the large-capacity activated carbon (B) 136. As the carbon dioxide remover 135, for example, there is a purification tube with OMI display function (OMI-2 or OMI-4) manufactured by SUPELCO.

(Large capacity activated carbon (B) 136)
The large-capacity activated carbon (B) 136 alleviates the over-reduction state of the nitrogen gas and discharges it to the gas chromatograph 2. For example, the large-capacity activated carbon (B) 136 is manufactured by GL Sciences, Inc., and is available under the product name: Large Hydrocarbon Trap. If there is a large amount of carbon monoxide (CO) remaining in the gas discharged to the gas chromatograph 2, a negative peak due to carbon monoxide will occur in the FID (Flame Ionization Detector)/GC (Gas Chromatograph). This tends to be a retention time just before methane, which is an obstacle to methane analysis. By installing the large-capacity activated carbon (B) 136 (activated carbon filter) downstream of the carbon dioxide removal device 135 (i.e., upstream of the gas chromatograph 2), the generation of carbon monoxide can be effectively suppressed.

The order of the processing steps in the moisture and carbon dioxide removal device 13 may be reversed, but it is preferable to perform the processing in the above order. This is for the following reason. When the filter in the carbon dioxide removal device 135 deteriorates, carbon dioxide gets mixed into the carrier gas. This increases the background of the thermal conductivity detector (TCD), making it difficult to detect carbon dioxide. To prevent deterioration of the filter in the carbon dioxide removal device 135, it is necessary to sufficiently remove water and oxygen at the previous stage.

<Catalyst function recovery device 20>
Next, the function and configuration of the catalyst function recovery device 20 will be described.
As described above, if the reaction process of methane combustion continues in the residual methane removal device 12, eventually the alumina of the catalyst 121 will be consumed and the catalytic function will be lost. Naturally, when the catalytic function is lost or the combustion is insufficient, nitrogen gas from which methane has not been completely removed will be discharged. In other words, the analysis in the gas chromatograph 2, into which the nitrogen gas is discharged, will be inaccurate.

Therefore, in this embodiment, under the control of the control device 30, the catalyst function recovery device 20 supplies compressed air to the residual methane removal device 12 at a predetermined timing for a predetermined period of time, thereby regenerating the alumina of the catalyst 121 of the residual methane removal device 12.
That is, the re-oxidation process of converting metallic aluminum into alumina is carried out by the chemical reaction shown in the following formula (2), which is the reverse of the reaction shown in formula (1) above, and is automated.
4Al+ _3O2 → _{2Al2O3 Formula} (2)

This reaction takes place in the presence of a Pt catalyst at 400°C, and is achieved by feeding dry air (compressed air) to the catalyst 121 of the residual methane removal device 12. A typical compressor is used as a device for supplying dry air (compressed air) to the residual methane removal device 12. The compressor may be the same as that used in the nitrogen generation device 11.

It is generally known that aluminum becomes alumina when it comes into contact with oxygen. However, the inventors of this application have discovered that when the original compound alumina (i.e. aluminum oxide) loses oxygen and becomes aluminum, losing its catalytic activity, it can be restored to alumina to the extent that its catalytic activity is restored by contacting it with oxygen (for example, by contacting it with the amount of oxygen supplied by compressing indoor air). Normally, oxygen reactions of metals often occur only on the surface of the metal, so this finding goes beyond common technical knowledge.

It is assumed that the nitrogen supply device 10 supplies 1 L of nitrogen gas per minute as a carrier gas to the gas chromatograph 2. When a commercially available device (GL Sciences AOE-2300 mentioned above) was used as the residual methane removal device 12, the catalyst life was approximately 60 days (2 months).

Table 1 shows an example of calculation of the equivalent amount for deterioration and recovery of aluminum oxide (alumina) in the catalyst 121.

By comparing the equivalent amounts of the reactions in formula (1) and formula (2), it is estimated that two months' worth of alumina deterioration can be restored by flowing dry air at a flow rate of 1 L/min for about one minute. If alumina is used until the end of its catalyst life, the methane combustion removal capacity (catalytic function) will be insufficient before the catalytic function is completely lost, and nitrogen gas with methane not completely removed will be discharged into the gas chromatograph 2. Therefore, when the methane combustion removal capacity is sufficient, it is desirable to ventilate compressed air for recovery. For example, by performing catalytic function regeneration every day or once every few days at a time that does not affect the operation of the gas chromatograph 2, an appropriate supply of nitrogen gas can be constantly provided to the gas chromatograph 2.

For example, in actual operation, although the efficiency will be lower than the above calculation, by passing 1 L/min of dry air (compressed air) through the catalyst 121 of the residual methane removal device 12 for about 30 seconds to several minutes per day, the deterioration (reduction reaction) of the alumina support material is countered by an oxidation treatment (reverse reaction), thereby maintaining the catalytic function continuously, i.e., realizing an extended lifespan of the catalytic function.

FIG. 4 is a flow chart showing a specific example of the catalyst function regeneration step (S200) performed by the catalyst function recovery device 20.
The control device 30 judges whether or not it is a predetermined catalyst regeneration timing (S201). The predetermined catalyst regeneration timing is registered in advance by an administrator.
If it is not the timing for regeneration (N in S202), the catalyst regeneration timing is periodically determined in S201.

If it is time for regeneration (Y in S202), the control device 30 controls the flow path switching valve to disconnect the nitrogen gas flow path from the residual methane removal device 12 (S203) and connect the flow path supplying compressed air from the catalyst function recovery device 20 to the residual methane removal device 12 (S204). As a result, the catalyst function recovery device 20 supplies compressed air to the residual methane removal device 12 (S205).

When the supply of compressed air starts, the control device 30 judges whether the predetermined supply time (i.e., the supply amount) has ended (S206). If it has not ended (N in S206), the supply of compressed air continues (S205). If the supply time has ended (Y in S206), the control device 30 stops the supply of compressed air from the catalyst function recovery device 20 to the residual methane removal device 12 and disconnects the flow path (S207), and connects the nitrogen gas flow path from the nitrogen generation device 11 to the residual methane removal device 12 to supply nitrogen gas (S208).

In the above process, the catalyst regeneration process is performed at a predetermined time, but the present invention is not limited to this. For example, the control device 30 may determine whether the catalytic function of the catalyst 121 is equal to or greater than a predetermined capacity, and when it is determined that the catalytic function is less than the predetermined capacity, the control device 30 may control the catalyst function recovery device 20 to recover the catalytic function of the catalyst 121. As a specific example, a sensor for detecting methane, moisture, and carbon dioxide is provided to detect whether the residual methane removal device 12 (catalyst 121) is functioning properly. If it is estimated based on the detection result that the catalytic function of the catalyst 121 will be lower than a predetermined value after a predetermined time has elapsed, for example, a warning is output, or the catalyst function recovery device 20 performs the function recovery process of the catalyst 121 at a timing when the gas chromatograph 2 is not in operation. In addition, if the cumulative values of the amount of nitrogen gas supplied to the gas chromatograph 2, the supply time, the operation time, and the like exceed a threshold value that requires the catalyst function recovery process by the catalyst function recovery device 20, the process is performed.

(Gas chromatograph 2 (three-component simultaneous analysis device))
5 is a schematic diagram showing the configuration of a three-component simultaneous analyzer, which is an example of the gas chromatograph 2. First, the three-component simultaneous analyzer according to this embodiment (hereinafter also referred to as the present analyzer) is an apparatus for detecting three components consisting of methane gas, carbon dioxide, and dinitrogen monoxide contained in atmospheric gas, which is an analysis sample. As shown in FIG. 5, the present analyzer has a first gas flow path A, a second gas flow path B and a third gas flow path C located downstream of the first gas flow path A, and a switching valve 1400 located between the first gas flow path A and the second gas flow path B and between the first gas flow path A and the third gas flow path C for switching between a first state in which the first gas flow path A and the second gas flow path B communicate with each other and a second state in which the first gas flow path A and the third gas flow path C communicate with each other. Hereinafter, each configuration of the present analyzer will be described.

First, the first gas flow path A has a carrier gas introduction section 1010 for introducing a carrier gas, a sample introduction section 1030 (injection port) for introducing an analytical sample, and a first column 1060 located downstream of the carrier gas introduction section 1010 and the sample introduction section 1030 and arranged to cause a flow delay according to the type of components contained in the analytical sample and to obtain a first gas phase containing methane gas and a second gas phase containing carbon dioxide and nitrous oxide.

In the present analytical apparatus, the above-mentioned carrier gas introduction section 1010 preferably includes a carrier gas purification device 1020. In this way, it is possible to improve the purity of the carrier gas introduced into the present analytical apparatus. The above-mentioned high purity nitrogen supply system 1 includes the functions of the carrier gas introduction section 1010 and the carrier gas purification device 1020.
In addition, when the above-mentioned three components are detected using a carrier gas whose purity has been increased by the carrier gas purifying device 1020, it is possible to prevent the S/N ratio of the analysis result and the detection sensitivity from being reduced due to the influence of impurities contained in the carrier gas. Specifically, by using a carrier gas such as nitrogen gas or helium gas whose purity has been increased by the carrier gas purifying device 1020, it is possible to prevent the detection peaks of the impurities contained in the carrier gas from overlapping with the detection peaks of the above-mentioned three components to be analyzed, and to prevent the above-mentioned impurities remaining in the gas separation columns (first to third columns, etc.) described later from increasing detector noise or shortening the column life.

The above-mentioned carrier gas purification device 1020 is used to increase the purity of the carrier gas introduced into the present analytical device, and from the viewpoint of dramatically improving the purity of the carrier gas, it is preferable to have a multi-stage carrier gas purification mechanism. Specific examples of the above-mentioned carrier gas purification mechanism provided in the carrier gas purification device 1020 include gas purification filters such as charcoal filters, moisture traps, oil mist traps, hydrocarbon removal tubes filled with activated carbon, moisture absorbent tubes filled with molecular sieves, and trace oxygen/water removal tubes filled with resin (for example, OMI-4 manufactured by SUPELCO, etc.).

In this analytical device, the sample introduction section 1030 described above is provided with a septum (packing) to prevent the analytical sample from leaking outside the device and to prevent outside air from mixing in. There are no limitations on the septum, so long as it satisfies the following conditions: it is possible to maintain the carrier gas pressure in the sample introduction section 1030, and it has a sealing property sufficient to prevent the analytical sample from leaking outside the device even if multiple analyses are performed. However, it is preferable to replace the septum with a new one after a maximum of 100 sample introductions, in order to prevent the above-mentioned inconveniences caused by deterioration associated with multiple sample introductions.

The sample introduction section 1030 in this analytical device may also have an automatic gas injection device (autosampler) in order to reduce the effort and time required to obtain measurement results.

In the first gas flow path A of this analytical device, downstream of the carrier gas introduction section 1010 and the sample introduction section 1030, there is a first column 1060 arranged to cause a flow delay according to the type of components contained in the analytical sample, and to obtain a first gas phase containing methane gas and a second gas phase containing carbon dioxide and nitrous oxide. As described above, this first column 1060 causes a flow delay according to the type of components contained in the analytical sample, so when the analytical sample is passed through the first column 1060, differences occur in the retention times of the components contained in the analytical sample.

Here, the column packing material contained in the first column 1060 is preferably a styrene polymer fine powder or an effective activated carbon fine powder. Among them, effective activated carbon fine powder is preferable from the viewpoint of generating a clear difference in the retention time between methane gas contained in the analysis sample and carbon dioxide and dinitrogen monoxide. Here, specific examples of effective activated carbon fine powder include zeolite powder containing molecular sieves and activated carbon. In addition, when such effective activated carbon fine powder is used as a column packing material, commercially available packing materials such as Unibeads C (manufactured by GL Sciences), activated carbon (SHINCARBON ST: Shinwa Kako), Molecular Sieve 5A (manufactured by GL Sciences), and Molecular Sieve 13X (manufactured by GL Sciences) may be used. Next, specific examples of styrene polymer fine powders include commercially available porous polymer packing materials such as Porapak Q, Porapak N, Porasil D, and Porapak QS manufactured by Waters. Among them, a packing material called Unibeads C (manufactured by GL Sciences) is preferable because it can cause a slight difference in the retention times of carbon dioxide and dinitrogen monoxide.

In addition, in this analytical device, the first column 1060 is configured to separate methane gas, which has a molar mass of approximately 16 g/mol, and carbon dioxide and nitrous oxide, which have a molar mass of approximately 44 g/mol, so that they are contained in different gas phases. Therefore, it is preferable that the first column 1060 be a packed column, from the viewpoints of superior hydrocarbon separation and larger sample volume that can be processed, rather than the number of theoretical plates per unit length of the column.

The column temperature of the first column 1060 is preferably, for example, 70°C or higher and 170°C or lower, and more preferably 80°C or higher and 150°C or lower. In this way, it is possible to create a clear difference in retention time between the first gas phase containing methane gas and the second gas phase containing carbon dioxide and nitrous oxide.

In addition to the first column 1060, the first gas flow path A in this analytical device preferably further includes a column containing a styrene polymer fine powder as a packing material in order to prevent column bleeding when the column is heated under high temperature conditions. Examples of such styrene polymer fine powder include commercially available porous polymer packing materials such as Porapak Q, Porapak N, Porapak D, and Porapak QS manufactured by Waters.

In addition, the first gas flow path A preferably further includes, for example, a moisture removal trap or an oxygen removal trap downstream of the sample introduction section 1030 in the first gas flow path A and upstream of the first column 1060, in order to remove moisture, oxygen, etc. contained in the analytical sample, from the viewpoint of improving the S/N ratio of the analysis result.

Next, the second gas flow path B has a hydrogen flame ionization detector 1100 (hereinafter also referred to as FID1100) at the downstream end for detecting methane gas contained in the first gas phase described above. The FID1100 generally refers to a detector that measures the concentration of total hydrocarbons by measuring the ion current generated when the gas to be measured is burned in a hydrogen flame. Therefore, the detector FID1100 is suitable for detecting hydrocarbons such as methane gas. Note that, when detecting methane gas using the FID1100, for example, when a carrier gas is flowed at a flow rate of 20 mL/min to 40 mL/min, the temperature of the FID1100 is set to 200°C to 300°C, and 1 mL of the analysis sample is introduced from the sample introduction section 1030, detection can be performed with a retention time of about 2 minutes.

In order to prevent column bleeding when the column is heated under high temperature conditions, it is preferable to further include a column containing a styrene polymer fine powder as a packing material upstream of the FID 1100 in the second gas flow path B. Examples of such a styrene polymer fine powder include commercially available porous polymer packing materials such as Porapak Q, Porapak N, Porasil D, and Porapak QS manufactured by Waters.

Next, the third gas flow path C has a second column 1070 consisting of a packed column, a third column 1080 consisting of a capillary column or a stainless steel column, which is located downstream of the second column 1070 and is arranged to cause a flow delay according to the type of component contained in the second gas phase to obtain a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide, a thermal conductivity detector 1200 located downstream of the third column 1080 for detecting carbon dioxide contained in the third gas phase, and an electron capture detector 1300 located downstream of the thermal conductivity detector 1200 for detecting nitrous oxide contained in the fourth gas phase.

The second column 1070 in the third gas flow path C is arranged to adjust the balance between the outlet pressure of the second gas flow path B and the outlet pressure of the third gas flow path C. In this way, by having the second column 1070 in this analysis device, the effect of the valve shock that occurs when switching the flow path state using the switching valve 1400 on the baseline and the detection peak shape can be reduced. Specifically, it is possible to suppress inconveniences such as baseline fluctuations and fluctuations in the detection peak shape caused by the valve shock. In order to accurately detect trace components such as nitrous oxide contained in the analysis sample introduced into this analysis device, it is particularly important to reduce the inconveniences caused by the valve shock as much as possible. The outlet pressure of the second gas flow path B refers to the gas pressure upstream of the hydrogen flame ionization detector 1100 in the second gas flow path B, and the outlet pressure of the third gas flow path C refers to the outlet pressure of the third column 1080 in the third gas flow path C.

Here, when the outlet pressure of the second gas flow path B is R2 and the outlet pressure of the third gas flow path C is R3, the second column 1070 is preferably configured so that the value of R2/R3 is 1 to 40, and more preferably 2 to 30. In this way, the two components carbon dioxide and nitrous oxide can be detected with a high S/N ratio. The outlet pressure of the gas flow path is generally proportional to the diameter of the column.

The column packing material contained in the second column 1070 is preferably a styrene polymer fine powder or an effective activated carbon fine powder. Among them, effective activated carbon fine powder is preferable from the viewpoint of generating a clear difference in the retention time between methane gas contained in the analysis sample and carbon dioxide and dinitrogen monoxide. Here, specific examples of effective activated carbon fine powder include zeolite powder containing molecular sieves and activated carbon. In addition, when such effective activated carbon fine powder is used as a column packing material, commercially available packing materials such as Unibeads C (manufactured by GL Sciences), activated carbon, Molecular Sieve 5A (manufactured by GL Sciences), and Molecular Sieve 13X (manufactured by GL Sciences) may be used. Next, specific examples of styrene polymer fine powder include commercially available porous polymer packing materials such as Porapak Q, Porapak N, Porasil D, and Porapak QS manufactured by Waters. In particular, the packing material Unibeads C (manufactured by GL Sciences) is preferred because it can produce a slight difference in the retention times of carbon dioxide and nitrous oxide.

The column temperature of the second column 1070 is, for example, preferably 70°C or higher and 110°C or lower, more preferably 75°C or higher and 100°C or lower, and even more preferably 80°C or higher and 90°C or lower.

Next, the third column 1080 in the third gas flow path C is a capillary column or stainless steel column downstream of the second column 1070, as described above, and is arranged to generate a flow delay according to the type of components contained in the second gas phase containing carbon dioxide and nitrous oxide, and to obtain a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide. Generally, capillary columns and stainless steel columns have a smaller column inner diameter and a higher theoretical plate number than packed columns. Therefore, the third column 1080 can reduce the flow rate of the gas that has passed through the second column 1070. That is, the third column 1080 can control the outlet pressure of the third column 1080 to be smaller than the outlet pressure of the second column 1070. As a result, in this analysis device, it is possible to generate a clear difference in the retention time of carbon dioxide and nitrous oxide, which have been difficult to completely separate in conventional analysis devices because they have almost the same molecular weight. In other words, because this analytical device employs a configuration that includes the third column 1080, it is possible to detect both carbon dioxide and nitrous oxide with high accuracy.

Here, the inner diameters of the second column 1070 and the third column 1080 are preferably 1 mm or more and 5 mm or less for the second column 1070 and 0.1 mm or more and 1 mm or less for the third column 1080, and more preferably 2 mm or more and 4.5 mm or less for the second column 1070 and 0.2 mm or more and 0.8 mm or less for the third column 1080. In this way, both carbon dioxide and nitrous oxide components contained in the analytical sample introduced into this analytical device can be detected with a high S/N ratio.

In order to accurately detect nitrous oxide, which is present in extremely small amounts in atmospheric gases even in the ppb order, the outlet flow rate of the third column 1080 in this analytical device (the outlet flow rate of the third gas flow path C) is preferably configured to be 3 mL/min or more and 25 mL/min or less when 500 μL or more of analytical sample is introduced from the sample introduction section 1030, and more preferably 3 mL/min or more and 20 mL/min or less.

Column packing materials to be contained in the third column 1080 include methylpolysiloxane and the like. As the third column 1080, commercially available capillary columns such as HP-1 (manufactured by Agilent Technologies) and DB-1 (manufactured by Agilent Technologies) and stainless steel columns of about 2 to 5 m containing porous polymer packing materials such as Porapak Q (manufactured by GL Sciences), Porapak N (manufactured by GL Sciences) and Porasil D (manufactured by GL Sciences) of about 80 to 100 mesh size can be used. Among them, it is preferable to use PoraBOND Q from the viewpoint of improving the separation efficiency of carbon dioxide and dinitrogen monoxide.

The column temperature of the third column 1080 is preferably, for example, 70° C. or higher and 170° C. or lower, and more preferably 80° C. or higher and 160° C. or lower. This makes it possible to detect both carbon dioxide and nitrous oxide with a high signal-to-noise ratio.

The third gas flow path C has a thermal conductivity detector 1200 (hereinafter also referred to as TCD1200) for detecting carbon dioxide contained in the above-mentioned third gas phase downstream of the third column 1080. Such a TCD1200 generally refers to a detector that measures the concentration of the above-mentioned measurement target component by measuring the difference in thermal conductivity between the measurement target component and the carrier gas. Therefore, the detector called TCD1200 is suitable for detecting components other than those contained in the carrier gas. Note that carbon dioxide can be detected using the TCD1200 with a retention time of about 4 to 5 minutes from the start of the carrier gas flow when the carrier gas is flowed at a flow rate of 35 mL/min to 45 mL/min, for example.

The third gas flow path C has an electron capture detector 1300 (hereinafter also referred to as ECD1300) for detecting nitrous oxide contained in the above-mentioned fourth gas phase downstream of the TCD1200. The ECD1300 generally refers to a detector that measures the concentration of the electrophile by measuring the amount of reduction in the ion current flowing between electrodes in the ECD1300, which is caused by ionizing a carrier gas using β rays from ⁶³ Ni and binding the released electrons with the electrophile. Therefore, the detector ECD1300 is suitable for detecting components such as nitro compounds. Nitrous oxide can be detected using the ECD1300 with a retention time of about 4 to 5 minutes from the start of the flow of the carrier gas when the carrier gas is flowed at a flow rate of 35 mL/min to 45 mL/min.

In addition, the third gas flow path C preferably further has an additive gas inlet 1050 for introducing an additive gas downstream of the TCD 1200 and upstream of the ECD 1300. As described above, the ECD 1300 detector utilizes an ion current (more specifically, a negative ion current) that flows between electrodes by ionizing a carrier gas. Therefore, the carrier gas must contain a sufficient amount of easily ionized components. Therefore, by supplying easily ionized gas components such as nitrogen gas and methane gas from the additive gas inlet 1050 to the third gas flow path C, it is possible to accurately detect the amount of nitrous oxide, which is contained in extremely small amounts in atmospheric gas, on the order of ppb.

Next, we will explain a three-component simultaneous analysis method (hereinafter referred to as this analysis method) that uses the above-mentioned analytical device to detect three components, consisting of methane gas, carbon dioxide, and nitrous oxide, contained in the atmospheric gas, which is the analytical sample.

This analytical method includes a carrier gas introduction step of introducing a carrier gas into a gas flow path, a sample introduction step of introducing an analytical sample into the gas flow path filled with the carrier gas, a first gas separation step of obtaining a first gas phase containing methane gas and a second gas phase containing carbon dioxide and nitrous oxide from components contained in the analytical sample, and a second gas separation step of obtaining a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide from components contained in the second gas phase.

(Carrier gas introduction process)
In this analysis method, first, a carrier gas is introduced into the first gas flow path A from the carrier gas introduction part 1010 in the present analysis apparatus shown in Fig. 5. In this way, all gas components present in the gas flow path in the present analysis apparatus can be replaced with the above-mentioned carrier gas. The flow rate of the carrier gas may be appropriately set by a flow regulator mounted on the present analysis apparatus, taking into consideration the relationship between the specifications of the column used and the retention time of the component to be analyzed. However, from the viewpoint of generating a difference in the retention time of the three components consisting of methane gas, carbon dioxide, and nitrous oxide, it is preferable to set the flow rate of the carrier gas to 20 mL/min or more and 40 mL/min or less.

In this analysis method, it is preferable to increase the purity of the carrier gas using the carrier gas purification device 1020 before introducing it into the first gas flow path A. That is, it is preferable that the carrier gas introduction step further includes a step of improving the purity of the carrier gas. In this way, it is possible to prevent the S/N ratio and detection sensitivity of the analysis result from being affected by impurities contained in the carrier gas from decreasing. Specifically, by increasing the purity of the carrier gas in advance using the carrier gas purification device 1020, it is possible to prevent the detection peak of the impurities contained in the carrier gas from overlapping with the detection peaks of the above three components to be analyzed, and the above impurities remaining in the gas separation columns (first to third columns, etc.) described later from increasing detector noise or shortening the column life. In particular, the purity of the carrier gas is preferably 99.999% or more from the viewpoint of accurately detecting the amount of nitrous oxide, which is contained in very small amounts in atmospheric gas, on the order of ppb, more preferably 99.9999% or more, even more preferably 99.99999% or more, and most preferably 99.999999% or more. Note that if the upper limit of the purity of the carrier gas is about 99.9999999%, the inconvenience caused by the influence of the above-mentioned impurities can be prevented. In addition, the carrier gas is preferably helium gas or nitrogen gas with a purity of 99.999% or more. From the viewpoint of improving the purity of the carrier gas as much as possible, the above-mentioned carrier gas purification device 1020 is preferably equipped with a multi-stage carrier gas purification mechanism.

(Sample introduction step)
Next, in this analysis method, an analysis sample is introduced into the gas flow path filled with carrier gas from the sample introduction part 1030. Specifically, 1 to 2 mL of atmospheric gas collected in a container such as a vial is introduced into the sample introduction part 1030 using a gas-tight syringe.

In this analysis method, in order to reduce the effort and time required to obtain measurement results, atmospheric gas may be introduced into the gas flow path from the sample introduction section 1030 using, for example, an automatic gas injection device (autosampler).

(First gas separation step)
Next, in this analysis method, the analysis sample is passed through a first column 1060 for causing flow delay according to the type of component. In this way, each component contained in the analysis sample can be separated into a first gas phase containing methane gas and a second gas phase containing carbon dioxide and dinitrogen monoxide. In addition, the analysis sample may be passed through a column containing a commercially available porous polymer packing material such as Porapak Q, Porapak N, Porasil D, and Porapak QS manufactured by Waters before and/or after passing through the first column 1060, in order to suppress column bleeding when the column is heated under high temperature conditions. In this analysis method, each component contained in the first gas phase is retained in the first column 1060 for a shorter time than each component contained in the second gas phase.

Next, the first gas phase containing methane gas is introduced into the second gas flow path B having the FID 1100. After this methane gas introduction step, the flow path state is switched by the switching valve 1400, and the second gas phase containing carbon dioxide and nitrous oxide is introduced into the third gas flow path C having the thermal conductivity detector 1200 and the electron capture detector 1300. The flow path state is switched by the switching valve 1400 at an appropriate timing taking into account the flow rate of the carrier gas and the retention time of each component by the first column 1060.

Next, the methane gas contained in the first gas phase introduced into the second gas flow path B is detected by the FID 1100. In order to prevent column bleeding when the column is heated under high temperature conditions, it is preferable to pass the first gas phase introduced into the second gas flow path B through a column containing a commercially available porous polymer packing material such as Porapak Q, Porapak N, Porasil D, and Porapak QS manufactured by Waters before introducing it into the FID 1100.

(Second gas separation step)
Next, the second gas phase containing carbon dioxide and nitrous oxide introduced into the third gas flow path C is passed through a second column 1070 consisting of a packed column. Thereafter, the second gas phase is passed through a third column 1080 consisting of a capillary column or a stainless column for causing flow delay depending on the type of component. In this manner, each component contained in the second gas phase can be separated into a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide. In this analysis method, each component contained in the third gas phase is retained in the third column 1080 for a shorter time than each component contained in the fourth gas phase.

After that, the carbon dioxide contained in the third gas phase obtained by passing through the third gas phase is detected by the TCD1200, and then the nitrous oxide contained in the fourth gas phase that passed through the TCD1200 is detected by the ECD1300. Here, in this analysis method, from the viewpoint of accurately detecting the amount of nitrous oxide, which is contained in very small amounts in atmospheric gas, on the order of ppb, during the period from when carbon dioxide is detected by the TCD1200 to when the fourth gas phase is introduced into the ECD1300, that is, from when carbon dioxide is detected to when nitrous oxide is detected, it is preferable to introduce methane gas or nitrogen gas as an additive gas into the gas flow path. In addition, according to the knowledge obtained by the present inventor so far, even when nitrogen gas is used as a carrier gas, it is possible to improve the detection sensitivity (and S/N ratio) of nitrous oxide by the ECD1300 by up to 10 times by adding methane gas.

In this embodiment, the three components of methane gas, carbon dioxide, and nitrous oxide contained in atmospheric gas can be detected simultaneously with a high S/N ratio in a single analysis, even when the sample concentration is on the order of ppb. In addition, according to this embodiment, it is also possible to quantitatively determine the three components of methane gas, carbon dioxide, and nitrous oxide contained in atmospheric gas in a single analysis, for example.

In addition, the high-purity nitrogen supply system 1 can supply stable, methane-free, high-purity nitrogen gas (carrier gas) to the gas chromatograph 2 (three-component simultaneous analysis device) capable of performing high-precision analysis as described above, without relying on high-pressure cylinders, which require careful handling and can be costly.

Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above may also be adopted. In addition, in the flow charts used in the above explanations, multiple steps (processing) are described in order, but the order in which the steps are executed in each embodiment is not limited to the order described. In each embodiment, the order of the steps shown in the figures may be changed to the extent that does not cause any problems in terms of content. In addition, the above-mentioned embodiments may be combined to the extent that the content is not contradictory.

<Summary of features and effects of the embodiment>
The features and effects of the above-described embodiment are summarized as follows.
(1) The residual methane removal device 12 of this embodiment includes a catalyst 121 supported by a metal oxide, which passes nitrogen gas from which oxygen has been separated and burns and removes methane gas remaining in the nitrogen gas;
A catalyst function recovery device 20 that regenerates the function of the catalyst 121 by passing oxygen through the catalyst 121;
Equipped with.
Metal oxides include aluminum oxide (alumina), copper oxide, and titanium oxide.
By burning methane gas, which is a nitrogen gas from which oxygen has been separated, in an oxygen-deficient state, oxygen can be recombined with the consumed catalyst 121 (i.e., metal oxide). In other words, the catalytic function of the catalyst 121, whose catalytic function has deteriorated, can be regenerated.
As described above, Patent Document 1 has realized a technology for supplying high-purity nitrogen created using compressed air, which has previously relied on high-pressure gas cylinders for the supply of nitrogen. However, replacing the catalyst 121 of the residual methane removal device 12 is expensive, and in many cases the nitrogen cylinder is continued to be used, so the operation of nitrogen gas supply using the above purification technology has not become widespread. However, the technology for regenerating the catalyst 121 has made it possible to create a constantly healthy combustion catalyst environment, and it has become possible to build a gas chromatograph analysis system 100 using high-purity nitrogen gas without using a high-pressure gas cylinder throughout the year. This contributes to a significant reduction in the amount of high-pressure gas cylinders used, and also makes it possible to stably perform high-precision gas analysis even in remote areas where it is difficult to transport cylinders. It is possible to extend the life of the catalytic combustion device for impurity incineration, thereby reducing running costs. In addition, for nitrogen gas supplied by a nitrogen supply device using the PSA method or other technologies, by introducing technology to regenerate the catalyst 121 of the residual methane removal device 12 described above, it is possible to extend the life of the combustion catalyst environment and reduce the operational effort and costs of the methane removal process.

(2) The metal oxide is aluminum oxide.
Aluminum oxide (alumina) is suitable for the catalyst 121 from the standpoints of catalytic ability, cost, availability, and stability (lifespan).

(3) The catalyst function recovery device 20 supplies oxygen to the catalyst 121 by using dry air.
If the gas passed through for the purpose of restoring the catalyst 121 is pure oxygen or oxygen-rich gas, there is a risk that oxygen not used for regenerating the catalyst 121 will remain in the catalyst 121. Oxygen can generally be removed (filtered) relatively easily in downstream processes, but it is desirable to suppress the amount of oxygen to a level sufficient for catalyst regeneration if possible. In this case, the oxygen concentration may be controlled by synthetic air, but the catalyst 121 can also be regenerated with ordinary dry air in a practical manner.
For example, in a system that continuously supplies nitrogen gas to multiple gas chromatographs 2, it was confirmed that the desired catalyst recovery was achieved by supplying dry air to the catalyst at 1 L/min once a day to once a few days, and that there was no effect of residual oxygen in downstream processes.

(4) The high purity nitrogen supply system 1 comprises the residual methane removal device 12 described above,
a nitrogen generator 11 for supplying nitrogen gas to a residual methane remover 12;
The system further includes a moisture and carbon dioxide removal device 13 (residual component removal device) that obtains the nitrogen gas from which the methane gas has been removed by the methane removal device and removes at least water and carbon dioxide from the nitrogen gas.
High-purity nitrogen gas from which methane gas has been removed can be continuously obtained, and moisture and carbon dioxide generated when methane gas is burned and removed can be effectively removed. In other words, high-quality nitrogen gas can be supplied to the gas chromatograph 2.

(5) A control device 30 is provided to control the operation of the catalyst function recovery device 20.
The control device 30 controls the catalyst function recovery device 20 so as to supply the oxygen at a predetermined timing to recover the function of the catalyst 121 .
By scheduling the timing to coincide with the recovery treatment period for the catalyst 121, methane-free high-purity nitrogen gas can be continuously supplied without substantially affecting the operation of the gas chromatograph 2.

(6) A control device 30 is provided to control the operation of the catalyst function recovery device 20.
The control device 30 judges whether the function of the catalyst 121 is equal to or greater than a predetermined capacity, and when it judges that the function is less than the predetermined capacity, controls the catalyst function recovery device 20 so as to recover the function of the catalyst 121 .
For example, using a sensor that detects methane or a sensor that senses the combustion state by detecting moisture and carbon dioxide, it is determined whether the desired combustion has been achieved, and if it is determined that the combustion state is not appropriate, i.e., that methane removal is insufficient, recovery is performed for the catalyst 121. Note that it is also possible to recover the catalyst 121 in advance, before the methane removal function (catalytic ability) of the catalyst 121 becomes insufficient, at a timing that does not affect the operation of the gas chromatograph 2.

(7) When operating the catalyst function recovery device 20, the control device 30 disconnects the nitrogen gas supply path from the nitrogen generator 11 to the catalyst 121 and connects the oxygen supply path to the catalyst 121. For example, one such configuration is to provide a flow path switching valve or the like in the supply path to control the flow path. With this configuration, the catalyst function recovery device 20 can perform the catalytic ability recovery process of the catalyst 121 by automatic switching.

(8) The gas chromatograph analysis system 100 includes the high-purity nitrogen supply system 1 described above,
a gas chromatograph 2 receiving nitrogen gas from the high-purity nitrogen supply system 1;
Equipped with.
The gas chromatograph analysis system 100 can substantially always use the methane-free high-purity nitrogen gas as the carrier gas, which means that the operation of the gas chromatograph 2 can be prevented from being suspended due to replacement of the catalyst 121.

(9) A method for regenerating catalytic function of a catalyst 121 in a high-purity nitrogen supply system 10 including a nitrogen generator 11 that purifies nitrogen gas by separating oxygen from air, and a residual methane remover 12 that includes a catalyst 121 supported on a metal oxide and that combusts and removes methane remaining in the nitrogen gas purified by the nitrogen generator 11, comprising:
When the nitrogen gas is not being passed through the catalyst 121, a gas containing oxygen is passed through the catalyst 121 to regenerate the catalytic function of the catalyst 121.

(10) In the method for regenerating catalyst function, the metal oxide of the catalyst 121 is aluminum oxide.
Aluminum oxide (alumina) is suitable for the catalyst 121 from the standpoints of catalytic ability, cost, availability, and stability (lifespan).

(11) A method for producing high purity nitrogen includes a raw gas obtaining step of obtaining nitrogen gas from which oxygen has been separated;
a methane removal step (S107) in which nitrogen gas is passed through a catalyst 121 having a metal oxide as a carrier to combust and remove methane remaining in the nitrogen gas;
A catalyst function regeneration step (S200) of stopping the methane removal step and passing oxygen through the metal oxide of the catalyst to regenerate the catalyst function;
has.
By burning methane gas, which is a nitrogen gas from which oxygen has been separated, in an oxygen-deficient state, oxygen can be recombined with the consumed catalyst 121 (i.e., metal oxide). In other words, the catalytic ability of the catalyst 121, whose catalytic function has deteriorated, can be regenerated.

1 High purity nitrogen supply system 2 Gas chromatograph 10 Nitrogen supply device 11 Nitrogen generator 12 Residual methane removal device 13 Moisture/carbon dioxide removal device (residual component removal device)
20 Catalyst function recovery device 30 Control device (control means)
100 Gas chromatograph analysis system 121 Catalyst 131 Moisture removal device 132 Large-capacity activated carbon (A)
133 Gas filter (moisture)
134 Gas filter (oxygen)
135 Carbon dioxide removal device 136 Large capacity activated carbon (B)

Claims (8)

a catalyst having an aluminum oxide (alumina) support, which passes nitrogen gas from which oxygen has been separated and burns and removes methane gas remaining in the nitrogen gas, and a catalyst function recovery means for regenerating the function of the catalyst by passing oxygen through the catalyst;
a nitrogen generator for supplying the nitrogen gas to the methane removal device;
a residual component removal device that obtains the nitrogen gas from which the methane gas has been removed by the methane removal device and removes at least water and carbon dioxide from the nitrogen gas;
A high purity nitrogen supply system comprising:
The catalyst function recovery means has a control device that executes a regeneration process of the catalyst function at a preset time before the function of the catalyst is lost.
High purity nitrogen supply system. a catalyst having an aluminum oxide (alumina) support, which passes nitrogen gas from which oxygen has been separated and burns and removes methane gas remaining in the nitrogen gas, and a catalyst function recovery means for regenerating the function of the catalyst by passing oxygen through the catalyst;
a nitrogen generator for supplying the nitrogen gas to the methane removal device;
a residual component removal device that obtains the nitrogen gas from which the methane gas has been removed by the methane removal device and removes at least water and carbon dioxide from the nitrogen gas;
A high purity nitrogen supply system comprising:
The catalyst function recovery means comprises a control device that executes a regeneration process of the catalyst based on the operation history of the methane removal device at a stage before the function of the catalyst is lost. a catalyst having an aluminum oxide (alumina) support, which passes nitrogen gas from which oxygen has been separated and burns and removes methane gas remaining in the nitrogen gas, and a catalyst function recovery means for regenerating the function of the catalyst by passing oxygen through the catalyst;
a nitrogen generator for supplying the nitrogen gas to the methane removal device;
a residual component removal device that obtains the nitrogen gas from which the methane gas has been removed by the methane removal device and removes at least water and carbon dioxide from the nitrogen gas;
A high purity nitrogen supply system comprising:
The catalyst function recovery means has a sensor that estimates whether the combustion state of the methane gas by the methane removal device is appropriate, and has a control device that executes a regeneration process of the catalyst based on the detection result of the sensor at a stage before the function of the catalyst is lost. A high-purity nitrogen supply system. The high-purity nitrogen supply system according to any one of claims 1 to 3, wherein the control device disconnects the nitrogen gas supply path from the nitrogen generating device to the catalyst and connects the oxygen supply path to the catalyst when the catalyst function recovery means is operated. A high purity nitrogen supply system according to any one of claims 1 to 4;
a gas chromatograph that receives nitrogen gas from the high-purity nitrogen supply system;
A gas chromatographic analysis system comprising: A catalyst having an aluminum oxide (alumina) support that ventilates the nitrogen gas from which oxygen has been separated and burns and removes methane gas remaining in the nitrogen gas;
A catalyst function recovery means for regenerating the function of the catalyst by supplying oxygen to the catalyst using compressed air;
a compressor that supplies the compressed air to the catalyst function recovery means;
A methane removal device comprising:
a nitrogen generator for supplying the nitrogen gas to the methane removal device;
a residual component removal device that obtains the nitrogen gas from which the methane gas has been removed by the methane removal device and removes at least water and carbon dioxide from the nitrogen gas,
The nitrogen generator is a high purity nitrogen supply system that uses the compressor to supply the nitrogen gas to the methane removal device. A gas chromatograph analysis system comprising the high-purity nitrogen supply system according to claim 6 and a gas chromatograph that receives nitrogen gas from the high-purity nitrogen supply system. The gas chromatograph analysis system according to claim 7, wherein the high purity nitrogen supply system has a first process in which air compressed to 5 to 8 atmospheres by a compressor shared with the methane removal device passes through a moisture trap and an oil mist trap, a second process in which the air passes through a tube with a water separation membrane after the first process, and a third process in which the air passes through a hydrocarbon removal tube and a tube with an oxygen-nitrogen separation membrane after the second process repeatedly.

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