TW201420495A - Refining method for nitrogen monoxide - Google Patents

Abstract

The present invention provides a nitrogen monoxide refining method in which the production of by-products can be suppressed and high purity nitrogen monoxide gas can be obtained, and also provides a refining system. The nitrogen monoxide refining method according to the present invention includes an adsorption step which circulates a mixed gas containing at least one of nitrogen monoxide and water into an inorganic adsorbent to make the adsorbent absorb water, wherein said inorganic adsorbent is a pre-treated adsorbent which is pre-treated for producing an inorganic salt. The present invention also provides a system to carry out the nitrogen monoxide refining method.

Description

Method for refining nitric oxide

The present invention relates to a method and system for purifying nitric oxide.

Nitric oxide, for example, in a semiconductor process, can be used to form a material gas for an oxynitride film or a SiON film. Nitric oxide can be obtained by various methods such as ammoxidation, a reaction between sodium nitrite and ferrous chloride, and a reaction between nitric acid and sulfurous acid gas, but generally contains moisture in the crude nitric oxide gas. Acidic gases such as nitrogen dioxide, sulfur dioxide and other impurities and by-products. In particular, in the method of producing nitric oxide by reducing nitric acid with sulfur dioxide, the crude nitric oxide contains sulfur dioxide impurities. However, in the semiconductor process, on the formation of an oxynitride film, it is desirable to use high purity nitric oxide as a material gas.

In the method of purifying and purifying nitric oxide, a relatively simple method is known, in which a crude nitric oxide (mixed gas) is introduced into an inorganic adsorbent such as active aluminum, zeolite or tannin under specific conditions. The method is already known. By this means, most of the moisture in the mixed gas can be adsorbed and removed by the inorganic adsorbent. A method using an inorganic adsorbent is as described in Patent Document 1 and Patent Document 2. In Patent Document 1, niobium, aluminum, zeolites, and mixtures thereof containing no metal cations are used as an adsorbent to purify nitrogen monoxide containing water, nitrogen dioxide, and sulfur dioxide. In Patent Document 2, in order to remove moisture and nitrogen oxides in the gas stream, The hydrazine is dehydrated and the nitrogen oxides are removed with zeolite Y containing 8-30% metal cations.

However, the above-described nitric oxide refining method using an inorganic adsorbent cannot effectively adsorb and remove moisture in the mixed gas because it is known that the impurity side reaction of nitric oxide (for example, 3NO→N ₂ O+NO ₂ ) A large increase in nitrogen dioxide or nitrous oxide in the mixed gas. Therefore, in the prior art, high purity nitric oxide cannot be obtained even with a special adsorbent.

Further, other relatively simple ones of the nitric oxide refining method are conventionally known methods of bringing a mixed gas into contact with an alkaline solution. Using this method, the main nitrogen dioxide or sulfur dioxide in the mixed gas can be removed by adsorption in an alkaline solution.

However, for example, conventional nitric oxide purification is carried out using an aqueous sodium hydroxide solution as an alkaline solution. Although nitrogen dioxide or sulfur dioxide in the mixed gas can be removed, moisture remains in the refined gas, and moisture must be removed.

Further, Patent Document 3 discloses another method for purifying nitric oxide, which uses a liquid nitrogen to carry out a -164 ° C low temperature separation method. However, this method is not suitable for industrialization because of the complicated equipment and expensive components required for the liquid nitrogen cooling operation, and may cause the explosion of liquid nitrogen monoxide.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Publication No. 8-319104

Patent Document 2: JP-A-51-141784

Patent Document 3: Korean Patent No. 20100007188 (A)

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method and system for suppressing the formation of by-products and obtaining a high-purity nitrogen monoxide gas by refining nitrogen oxide.

In a first aspect of the present invention, the present invention provides a method for purifying nitric oxide, comprising the step of adsorbing a mixed gas containing at least one of nitrogen monoxide and water to an inorganic adsorbent to adsorb moisture by the adsorbent. The inorganic adsorbent is characterized in that the adsorbent is treated before the pretreatment is performed in order to form an inorganic salt. The inorganic salts described in the present invention are represented by nitrates, and others may be sulfates, phosphates, hydrochlorides and the like.

The present inventors have found that when a crude nitrous oxide gas (hereinafter referred to as a mixed gas) is passed through an adsorbent to remove impurities in the mixed gas, a specific pretreatment is applied to the inorganic adsorbent in advance to suppress oxidation. Side reaction of nitrogen impurities. Specifically, for example, when a contact aqueous mineral acid solution having a polarity higher than that of the inorganic adsorbent is used as a pretreatment, a part of the inorganic acid is chemically adsorbed with the inorganic adsorbent to form a mineral acid salt, thereby causing inorganic adsorption. One of the agents is a state in which the catalytic activity of the side reaction of the nitrogen oxide impurity is blocked. Therefore, in one of the nitrogen oxide refining methods of the present invention, the adsorption step can reduce the amount of by-products formed by the side reaction of the nitric oxide impurities. Thus, the process of the invention achieves higher purity nitric oxide.

The above pretreatment preferably includes an operation of bringing an aqueous mineral acid solution into contact with the above inorganic adsorbent. In this case, the aqueous inorganic acid solution is preferably an aqueous solution of nitric acid.

The pretreatment described above preferably includes the acid gas and the above inorganic absorption Attachment contact operation.

In an embodiment of the present invention, the mixed gas comprises at least one of nitrogen dioxide and sulfur dioxide impurities, and the mixed gas further comprises contacting the mixed gas with an alkaline solution to absorb and remove the impurities (the oxidation) before performing the adsorption step. An alkaline cleaning step of nitrogen or sulfur dioxide.

In the method of the present invention, even if the mixed gas contains nitrogen dioxide or sulfur dioxide impurities, the alkaline aqueous solution can be effectively used to remove nitrogen dioxide or sulfur dioxide after the alkaline washing step. Therefore, the method of the present invention can obtain high purity nitric oxide.

In a second aspect of the present invention, the present invention provides a nitric oxide purification system comprising: an adsorption tube filled with an inorganic adsorbent for adsorbing and removing moisture in a mixed gas containing at least one of nitrogen monoxide and water; The inorganic adsorbent is pretreated in advance to form an inorganic salt.

The above inorganic salts are preferably nitrates.

In one embodiment of the second aspect of the present invention, the mixed gas contains at least one of nitrogen dioxide and sulfur dioxide impurities, and an upstream side of the adsorption tube is provided with an alkaline aqueous solution for removing and removing the impurities in the mixed gas. Absorbent contact device.

X1‧‧‧ refining system

Y1‧‧‧NO cylinder

1‧‧‧Absorption contact device

2‧‧‧Adsorption tube

3‧‧‧Pressure adjustment valve

4A-4E‧‧‧ switch valve

5‧‧‧ Finished NO export

6‧‧‧ cleaning gas inlet

7‧‧‧ gas discharge

8‧‧‧vacuum pump

Fig. 1 is a simplified schematic view of a refining system in which the nitric oxide refining method of the present invention can be carried out.

Next, a preferred embodiment of the present invention will be described based on the drawings. Of course However, the embodiments described below are merely examples and are not intended to limit the scope of the invention.

Fig. 1 is a schematic view showing a purification system X1 used for carrying out a nitric oxide (NO) purification method. The refining system X1 includes a raw NO gas supplied from the NO cylinder Y1 for refining (purification), and an absorption liquid contact device for removing nitrogen dioxide (NO ₂ ) and sulfur dioxide (SO ₂ ), and removing moisture (H _{2 )} O) adsorption tube 2, pressure regulating valve 3, on-off valves 4A to 4E, finished NO outlet 5, cleaning gas introduction port 6, gas discharge port 7, vacuum pump 8, and a line connecting the above devices.

The NO cylinder Y1 is a device for supplying a crude NO gas of the purification system X1 as a raw material gas (mixed gas), and the crude NO gas is injected by high pressure. The injected NO gas contains NO as a main component, and NO ₂ , SO ₂ , and H ₂ O impurities.

The absorption liquid contact device 1 is a device for bringing the raw material gas into contact with the alkaline aqueous solution as the absorption liquid, and includes the absorption liquid tank 1A, the gas introduction pipe 1a, the gas outlet port 1b, the absorption liquid supply port 1c, and the liquid discharge port 1d. The absorption liquid tank 1A has a container shape, and the inside thereof is filled with an alkaline aqueous solution capable of absorbing NO ₂ and SO ₂ . The gas introduction pipe 1a is located inside the absorption liquid tank 1A and extends downward, and its lower end portion is opened in an alkaline aqueous solution. The absorption liquid supply port 1c is a pipe for supplying a new alkaline aqueous solution to the absorption liquid tank 1A. The liquid discharge port 1d is a pipe for discharging the alkaline aqueous solution in the absorption liquid tank 1A to the absorption liquid tank 1A.

The aqueous alkaline solution may be, for example, an aqueous solution of sodium hydroxide, potassium hydroxide or magnesium hydroxide. Among them, sodium hydroxide is preferred from the viewpoint of availability.

In the absorption liquid contact device 1, it is preferable that the raw material gas is released into the alkaline aqueous solution in the form of microbubbles from the viewpoint of allowing the raw material gas to be effectively contacted with the alkaline aqueous solution. Since the structure in which the material gas is discharged in the form of microbubbles is a conventional technique, it is not shown in Fig. 1.

The adsorption tube 2 exhibits a form in which gas can pass, and is cylindrical in this embodiment. The inside of the adsorption tube 2 is filled with an inorganic adsorbent having an adsorption property of H ₂ O, an adsorption capacity of NO _{2 , and an} adsorption capacity of SO ₂ . The inorganic adsorbent may be activated aluminum, zeolite, tannin or the like. Among them, preferred are activated aluminum or zeolite A which is generally used for dehydration. These adsorbents are pre-treated prior to NO purification as will be described later. Further, the adsorption tube 2 may have a temperature adjustment device (not shown) for adjusting the internal temperature.

The pressure regulating valve 3 can depressurize the material gas supplied from the NO cylinder Y1 to a specific pressure. Each of the on-off valves 4A to 4E can select an open state in which the gas passes and a closed state in which the passage is blocked.

As described above, in the NO purification method, the inorganic adsorbent charged in the adsorption tube 2 is subjected to a pretreatment for producing an inorganic salt before the purification of the NO by the purification system X1.

The pretreatment is to contact an aqueous inorganic acid solution with an inorganic adsorbent. The contact of the aqueous solution of the inorganic acid with the inorganic adsorbent can, for example, be performed by immersing the inorganic adsorbent in an aqueous solution of a mineral acid. The inorganic acid may be, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or the like. Among them, since the by-product of NO purification is nitric acid, nitric acid is preferably used to prevent foreign matter from entering. The aqueous solution of nitric acid as an aqueous solution of a mineral acid is contacted with an inorganic adsorbent to form a nitrate, and a pretreated adsorbent can be obtained. In the present invention, the concentration of the aqueous solution of the inorganic acid is not particularly limited, but it is usually An inorganic acid aqueous solution specified in 0.01 to 1. The impregnation of the inorganic adsorbent with the inorganic acid aqueous solution is, for example, preferably carried out for 1 to 20 hours in addition to the purification system X1. If the inorganic acid aqueous solution and the adsorbent are not stirred, and left at room temperature, it must be immersed for 10 hours or more. If it is stirred at 40 to 50 ° C, it takes only 2 hours to complete. Thereafter, the adsorbent is filtered and dried. Although the drying method is preferably dried under reduced pressure or hot air, a drying method such as a static drying or a vacuum dryer can also be used. The dried, impregnated adsorbent can be stored in a storage container, but in order to not absorb moisture during storage, the air in the storage container can be replaced with nitrogen for storage. However, the above pretreated adsorbent may also be stored without being stored, and directly filled into the adsorption tube 2 after pretreatment.

Further, the prior treatment of the present invention is not limited to the wet method described above, and dry contact with an acid gas and an inorganic adsorbent may be utilized. For example, an inorganic adsorbent and an acid gas-containing gas such as NO ₂ or SO _{2 are} added to a pressurizable container such as an autoclave, and are kept at 0.1 to 1.5 MPa before being held at 30 to 60 ° C for several hours. deal with. In the present invention, an acid gas such as nitrogen, argon (Ar) or helium (He) may be added, or a gas such as NO which is mixed with the product gas and which is not problematic may be added to dilute the acid gas. The pretreated adsorbent thus obtained may be directly filled into the adsorption tube 2 after the pretreatment is completed, or may be stored in the storage container and then filled into the adsorption tube 2.

After the pretreatment described above, the adsorbent tube 2 is filled with the pretreated adsorbent, and the purification system X1 is used to purify the NO. First, the on-off valves 4A, 4C are opened, and the on-off valves 4B, 4D, 4E are closed. Next, the raw material gas (crude NO gas) is continuously supplied from the NO cylinder Y1 to the absorbing liquid contact liquid device 1 via the pressure regulating valve 3, and an alkaline washing step is performed in the absorbing liquid contact device 1. As described above, the material gas contains NO as a main component, and NO ₂ , SO ₂ and H ₂ O impurities. NO ₂ concentration in the material gas by the NO cylinder Y1 provided, the concentration of SO _2, and H ₂ O concentrations were as 0.1 ~ 1000ppm. The pressure set by the pressure regulating valve 3 is, for example, 0.05 to 20 MPa, preferably 0.1 to 2 MPa.

In the alkaline cleaning step, the raw material gas is discharged from the lower end portion of the gas introduction pipe 1a, the raw material gas is brought into contact with the alkaline aqueous solution, and the NO ₂ and SO ₂ impurities are absorbed in the alkaline aqueous solution, and the unabsorbed gas is guided by the gas. The outlet 1b is led out of the absorbent contact device 1. Further, in the alkaline washing step, the new alkaline aqueous solution can be replenished at a certain flow rate by the absorption liquid supply port 1c, and the alkaline aqueous solution in the absorption liquid tank 1A is discharged from the liquid discharge port 1d at a certain flow rate. The liquid contacts the device 1 outside. The temperature of the alkaline aqueous solution in the absorption liquid tank 1A is, for example, 10 to 50 ° C, preferably 20 to 40 ° C.

The raw material gas (non-absorbed gas) which has passed through the alkaline cleaning step in the absorption liquid contact device 1 is then passed through the on-off valve 4A to the adsorption tube 2 to start the adsorption step. The adsorption step is such that the pretreated adsorbent in the adsorption tube 2 contacts the non-absorbed gas, and the residual H ₂ O, NO ₂ , SO ₂ impurities in the non-absorbed gas (since most of the NO ₂ has been removed in the previous alkaline cleaning step ₎ And SO ₂ , therefore, in the adsorption step, the main impurity is H ₂ O), and the adsorbed gas is discharged to the adsorption tube 2 by previously treating the adsorbent or the state of being maintained. The internal temperature of the adsorption tube 2 is, for example, -40 to 50 ° C, preferably 0 to 40 ° C. In the present embodiment, since the pretreated adsorbent can form a nitrate, the catalytic activity point of the inorganic adsorbent is blocked. Therefore, the adsorption step can suppress side reactions of NO impurities to reduce the amount of N ₂ O or NO ₂ produced by the side reactions of impurities. In the adsorption step, in order to sufficiently absorb H ₂ O, it is possible to proceed to the point of time (breaking point) at which the breakthrough starts, or to terminate before the break point. The raw material gas is continuously supplied from the NO cylinder Y1 to the refining system X1, the on-off valve 4C is turned off, and the on-off valve 4D is turned on to complete the adsorption step. At the end of the adsorption step, the gas (purified NO gas) passing through the adsorption tube 2 can be taken out from the NO outlet 5 .

Therefore, the crude NO gas (raw material gas) containing impurities of NO ₂ , SO ₂ and H ₂ O can be purified to obtain a NO gas of high purity.

In order to allow the NO gas purification method of the present invention to be repeated in the purification system X1, the adsorbent 2 or the adsorbent inside thereof may be regenerated or washed after the completion of the purification process.

When the regeneration and cleaning of the adsorbent are performed before the adsorption tube 2 or the inside is performed, the on-off valves 4A, 4C, and 4E are in a closed state, and the on-off valves 4B and 4D are in an open state. Therefore, the inert gas can be continuously introduced into the refining system X1 by the cleaning gas introduction port 6. The inert gas introduced from the purge gas introduction port 6 can be heated to a specific temperature by a heater (not shown) in advance, and discharged from the outside of the line through the gas discharge port 7 via the on-off valve 4B, the adsorption tube 2, and the on-off valve 4D. The inert gas may be, for example, N ₂ or argon (Ar) or helium (He). The temperature of the inert gas heated by the heater is, for example, 100 to 300 ° C, preferably 150 to 250 ° C. Therefore, a specific amount and an inert gas of a specific pressure are circulated to the adsorbent tube 2 or the pretreated adsorbent inside thereof to regenerate or clean the adsorbent tube 2 or even the pretreated adsorbent.

According to the NO purification method described above, in the alkaline cleaning step of the absorption liquid contacting device 1, the alkaline aqueous solution can absorb and remove NO ₂ or SO ₂ in the raw material gas. Further, in the adsorption step of the adsorption tube 2, the pretreated adsorbent is used to suppress the NO impurity side reaction, and the amount of by-product N ₂ O or NO ₂ is reduced. Therefore, when the raw material gas contains NO ₂ , SO ₂ , and H ₂ O impurities, the alkaline washing step and the adsorption step can effectively remove NO ₂ , SO _{2 ,} and H ₂ O, and reduce the amount of by-product formation in each step. Obtain high purity NO.

If the raw material gas supplied from the NO cylinder Y1 does not substantially contain NO ₂ and SO ₂ , or the content of NO ₂ and SO ₂ is small, the alkaline washing step can be omitted. At this time, the purification system that performs the NO purification method does not have the absorption liquid contact device 1.

Hereinafter, the present invention will be described in detail by way of Examples 1 to 4 and Comparative Examples.

[Examples] [Example 1]

In the first embodiment, the absorbing liquid contact device 1 in the above embodiment (Fig. 1) is omitted, and the crude NO supplied from the NO cylinder Y1 is subjected to an adsorption step in the adsorption tube 2. Active aluminum (trade name: KHD-12, manufactured by Sumitomo Chemical Co., Ltd.) was used as the inorganic adsorbent filled in the adsorption tube 2. The pretreatment of the adsorbent was carried out by adding 18.6 g of active aluminum to 0.3 of an aqueous solution of nitric acid specified at 0.3. The mixture was stirred at ° C for 2 hours and then dried under vacuum at 60 ° C for 6 hours. The previously obtained adsorbent obtained was filled in a adsorption tube 2 (a stainless steel cylindrical adsorption tube having an inner diameter of 7.5 mm and a length of 500 mm). Thereafter, the adsorption tube 2 is heated to 150 ° C, and the on-off valves 4A to 4D are closed, and the on-off valve 4E is opened, and the vacuum pump 8 is turned on, so that the pressure in the adsorption tube 2 becomes 270 Pa (abs) for about 2 hours. Vacuuming. Next, the crude NO gas (H ₂ O content = 100 ppm, NO ₂ content = 500 ppm, N ₂ O content = 50 ppm) as a material gas was flowed to the adsorption tube 2 at 25 ° C under a pressure of 0.15 MPaG. The flow rate of the material gas flowing to the adsorption tube 2 was 60 ml/min. The adsorption step is carried out under such conditions. One hour after the start of the flow, the unadsorbed gas was taken out from the adsorption tube 2, and analyzed by dew point and FT-IR. As a result, H ₂ O content = 1 ppm, NO ₂ content = 30 ppm, and N ₂ O content = 65 ppm. The N ₂ O content was increased by 15 ppm.

[Example 2]

In Example 2, the active aluminum of Example 1 was replaced with molecular sieve 4A (trade name: zeolite A-4, manufactured by TOHOH Co., Ltd.) as an inorganic adsorbent. The purification of NO (pretreatment and adsorption step) was carried out under the same conditions as in Example 1 except for the change of the inorganic adsorbent. One hour after the flow of the material gas to the adsorption tube 2, the unadsorbed gas was taken out from the adsorption tube 2 and analyzed, and as a result, H ₂ O content = 1 ppm, NO ₂ content = 25 ppm, N ₂ O content = 60 ppm, and N ₂ before and after circulation. The O content was increased by 10 ppm.

[Example 3]

In Example 3, the pretreatment of the adsorbent was carried out by adding 150 ml of activated aluminum (trade name: KHD-12, manufactured by Sumitomo Chemical Co., Ltd.) to a 3 Mpa pressure-resistant stainless steel autoclave having a content of 300 ml, and adding A mixed gas of NO/NO ₂ = 1:1 until the pressure is 1.5 MPaG. After maintaining at 40 ° C for 4 hours, the gas was purged, and a mixed gas of NO / NO ₂ = 1:1 was again added until the pressure was 1.5 MPa, and it was kept at 30 ° C for 5 hours. In the same manner as in Example 1, the previously treated adsorbent was charged into the adsorption tube 2, and purified under the same material gas supply conditions as in Example 1. One hour after the start of the flow, the unadsorbed gas was taken out from the adsorption tube 2 for analysis, and as a result, the H ₂ O content = 1 ppm, the NO ₂ content = 30 ppm, and the N ₂ O content = 63 ppm, and the N ₂ O content before and after the circulation increased. 13ppm.

[Embodiment 4]

In the fourth embodiment, the absorbent contact device 1 and the adsorption tube 2 of the above embodiment (Fig. 1) were used to carry out an alkaline washing step and an adsorption step. In the present embodiment, 500 ml of a 1% by weight aqueous sodium hydroxide solution as an alkaline aqueous solution was filled into the absorbent liquid contact device 1 having a volume of 1000 ml. The active aluminum previously treated in the same manner as in Example 1 was filled in the adsorption tube 2, and heated and evacuated. Next, the raw NO gas (H ₂ O content = 100 ppm, NO ₂ content = 500 ppm, SO ₂ content = 500 ppm, N ₂ O content = 50 ppm) as a raw material flows to the absorption liquid contact device at 25 ° C at a pressure of 0.15 MPaG. With the adsorption tube 2. One hour after the start of the raw material gas flowing to the absorption liquid contact device 1 and the adsorption tube 2, the unadsorbed gas was taken out from the adsorption tube 2 for analysis, and as a result, the H ₂ O content = 1 ppm, the NO ₂ content = 10 ppm, and the SO ₂ content = low. At 1 ppm and N ₂ O content = 63 ppm, the N ₂ O content before and after the circulation was increased by 13 ppm.

[Comparative example]

In the comparative example, in the same manner as in the first embodiment, the adsorption tube 2 and the inorganic adsorbent (the absorption liquid contact device 1 are omitted) are used, and the pretreatment is not performed to purify the NO. 18.6 g of activated aluminum (trade name: KHD-12, manufactured by Sumitomo Chemical Co., Ltd.) was charged into the adsorption tube 2, the adsorption tube 2 was heated to 150 ° C, and the on-off valves 4A to 4D were closed, and the on-off valve 4E was opened. The vacuum pump 8 was turned on so that the pressure in the adsorption tube 2 became 270 Pa (abs) to perform vacuuming for about 2 hours. Next, crude NO gas (H ₂ O content = 100 ppm, NO ₂ content = 500 ppm, N ₂ O content = 50 ppm) as a material gas was flowed to the adsorption tube 2 at 25 ° C at a pressure of 1.5 MPaG. The flow rate of the material gas flowing to the adsorption tube 2 was 60 ml/min. The adsorption step is carried out under such conditions. That is, in the comparative example, the purification of NO was carried out in the same manner as in Example 1 except that the pretreatment was not carried out. One hour after the start of the flow of the raw material gas to the adsorption tube 2, the unadsorbed gas was taken out from the adsorption tube 2 and analyzed, and as a result, the H ₂ O content = 1 ppm, the NO ₂ content = 30 ppm, the N ₂ O content = 250 ppm, and the N before and after the flow. _{The 2} O content was increased by 200 ppm.

【Evaluation】

N ₂ O Comparative Examples 1 to 4, increasing the amount of N ₂ O with increasing amounts of the comparative example can be appreciated, compared with the Comparative Example, the adsorption step in one embodiment, can significantly reduce the amount of N ₂ O is increased. The reason for this is considered to be that the inorganic adsorbent is subjected to a specific pretreatment to suppress side reactions of NO impurities to reduce the amount of N ₂ O produced. In addition, suppression of impurity side reactions can also reduce the amount of NO ₂ produced. Therefore, the effect of reducing the amount of increase in NO ₂ can be expected as compared with the case where pretreatment is not performed. Therefore, in the examples, by using the adsorption step of the pretreated adsorbent, the amount of by-product (N ₂ O or NO ₂ ) produced can be reduced to obtain higher purity NO.

X1‧‧‧ refining system

Y1‧‧‧NO cylinder

1‧‧‧Absorption contact device

2‧‧‧Adsorption tube

3‧‧‧Pressure adjustment valve

4A-4E‧‧‧ switch valve

5‧‧‧ Finished NO export

6‧‧‧ cleaning gas inlet

7‧‧‧ gas discharge

8‧‧‧vacuum pump

1a‧‧‧ gas introduction tube

1b‧‧‧ gas outlet

1c‧‧‧ Absorbent supply port

1d‧‧‧Liquid discharge

1A‧‧‧ absorption tank

Claims (8)

A method for purifying nitric oxide, comprising: a step of adsorbing a mixed gas containing at least one of nitrogen monoxide and water to an inorganic adsorbent to adsorb moisture by the adsorbent, characterized in that: the inorganic adsorbent The adsorbent is treated before the pretreatment is given in advance in order to produce an inorganic salt. A method for refining nitrogen oxide according to claim 1, wherein the pretreatment comprises an operation of contacting an aqueous inorganic acid solution with the inorganic adsorbent. A method for purifying nitrogen oxide according to the second aspect of the invention, wherein the aqueous solution of the inorganic acid is an aqueous solution of nitric acid. A method for refining nitrogen oxide according to claim 1, wherein the pretreatment comprises an operation of contacting an acid gas with the inorganic adsorbent. The method for refining nitrogen oxide according to any one of claims 1 to 4, wherein the mixed gas further comprises at least one impurity of nitrogen dioxide and sulfur dioxide, and the mixed gas is further subjected to the adsorption step. An alkaline cleaning step of contacting the mixed gas with an aqueous alkaline solution to absorb the impurities is included. A nitric oxide refining system comprising an adsorption tube filled with an inorganic adsorbent for adsorbing and removing moisture contained in a mixed gas containing at least one of nitrogen monoxide and water, wherein the inorganic adsorbent is for generating an inorganic salt Pre-treatment is given in advance. A refining system for nitrogen oxides according to claim 6, wherein the inorganic salt is a nitrate. A refining system for nitric oxide according to claim 6 or 7, wherein the mixed gas contains at least one impurity of nitrogen dioxide and sulfur dioxide, and on the upstream side of the adsorption tube, is disposed to be accommodated for contact to remove the mixture. The absorption liquid of the alkaline aqueous solution of the impurity in the gas contacts the device.