KR102729734B1 - Method for producing nitrogen monoxide and nitrogen monoxide produced by the method - Google Patents

Abstract

The present invention provides a method for producing nitrogen monoxide, including the steps of: 1) performing a gas-liquid separation process under conditions of a pressure of 1 to 20 bar and a temperature of -20 to 30°C on a mixed gas generated in a process of producing nitric acid by reacting ammonia and oxygen; 2) supplying the mixed gas separated by the gas-liquid separation to an adsorption tower filled with an adsorbent to separate impurities; 3) distilling the mixed gas obtained in the adsorption step in a high-boiler distillation tower under pressure and temperature conditions at which NO can be vaporized to remove high-boiler substances existing in a liquid phase; 4) supplying the mixed gas from which the liquid high-boiler substances have been removed to a low-boiler distillation tower, and distilling it under pressure and temperature conditions at which NO does not vaporize to remove low-boiler substances in a gas phase; and 5) recovering the NO from which the low-boiler substances have been removed;

Description

Method for producing nitrogen monoxide and nitrogen monoxide produced by the method

The present invention relates to a method for safely and efficiently producing nitrogen monoxide and high-purity nitrogen monoxide produced by the method.

High purity nitrogen monoxide is used in various places such as semiconductor gas and medical gas. In particular, when nitrogen monoxide is used as a semiconductor gas, a high purity of 99.95% or higher is required.

Nitrogen monoxide is generally produced by ammonia oxidation, reaction of sodium nitrite with sulfuric acid, and reaction of sodium nitrite with ferric chloride. In the ammonia oxidation method, ammonia oxidation and the chemical reactions occurring simultaneously are as follows.

NH ₃ + 2O ₂ → HNO ₃ + H ₂ O (preferred overall reaction)

4NH ₃ + 7O ₂ → 4NO ₂ + 6H ₂ O (preferred reaction equation when using excess O ₂ )

3NO ₂ + 3O ₂ → 2HNO ₃ + NO (preferred reaction equation in the NO ₂ absorption process)

4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O (unfavorable reaction)

4NH ₃ + 4O ₂ → 2N ₂ O + 6H ₂ O (unfavorable reaction)

2NH ₃ + 8NO → 5N ₂ O + 3H ₂ O (unfavorable reaction)

When producing nitrogen monoxide by the ammonia oxidation method, various reactions as mentioned above occur, so the production efficiency is low. In addition, since high-purity ammonia must be used, the production cost is high, and since KMnO ₄ aqueous solution, etc. is used to remove unreacted ammonia, there are disadvantages in that the wastewater treatment cost is high.

On the other hand, nitrogen monoxide is a thermodynamically unstable substance and exists as nitrogen oxide (NOx) by reacting as follows. Therefore, the purity of nitrogen monoxide is reduced, making it difficult to purify high-purity nitrogen monoxide.

2NO + O ₂ → 2NO ₂

NO ₂ + NO ↔ N ₂ O ₃

2NO ₂ ↔ N ₂ O ₄

Conventional technology mostly cools to ultra-low temperatures to remove NxOy and NOx series substances, and then purifies and stores nitrogen monoxide with high purity. That is, when cooled to ultra-low temperatures, nitrogen monoxide in a gaseous state becomes a solid state, and substances with lower boiling points than nitrogen monoxide exist in a gaseous state. Therefore, impurity gases are removed, and solid nitrogen monoxide is obtained. However, solid nitrogen monoxide obtained by this method must be phase-transformed to a gaseous state when used, and at this time, there is a high possibility of explosion due to rapid volume expansion, etc., and there have actually been cases of explosions in the United States.

In addition, conventional nitrogen monoxide manufacturing methods cannot be mass-produced due to environmental problems such as NOx gas emissions.

Therefore, improvements to these problems are required.

Republic of Korea Patent No. 10-1257794

The present invention has been devised to solve the above problems of the prior art.

The purpose is to provide a method for producing high-purity nitrogen monoxide with excellent safety and efficiency, which prevents the risk of explosion due to phase transformation of nitrogen monoxide, minimizes the generation of NOx gas, and enables recycling and use of by-products such as wastewater and waste gas, and high-purity nitrogen monoxide produced by the method.

The present invention

1) A step of performing a gas-liquid separation process on a mixed gas generated in a process of producing nitric acid by reacting ammonia and oxygen under conditions of a pressure of 1 to 20 bar and a temperature of -20 to 30°C;

2) A step of supplying the mixed gas separated by the above gas-liquid separation to an adsorption tower filled with an adsorbent to separate impurities;

3) A step of removing the high-temperature substance present in the liquid phase by distilling the mixed gas obtained in the above adsorption step in a high-temperature distillation tower under the pressure and temperature conditions where NO can be vaporized; and

4) A step of supplying the mixed gas from which the liquid high-boiling substances have been removed to a low-boiling substance distillation tower and removing the gaseous low-boiling substances by distillation under pressure and temperature conditions at which NO is not vaporized; and

5) A method for producing nitrogen monoxide is provided, including a step of recovering NO from which the above low-cost substances have been removed.

In addition, the present invention

After step 4) of the above manufacturing method

The present invention provides a method for producing nitrogen monoxide, which further includes a step of supplying the liquid NO obtained above to an adsorption tower filled with an adsorbent to purify impurities.

In addition, the present invention

Nitrogen monoxide manufactured by the above method is provided.

According to the method for producing nitrogen monoxide of the present invention, the risk of explosion due to phase change of nitrogen monoxide is prevented, NOx gas generation is minimized, and by-products such as wastewater and waste gas can be recycled and used, so the safety and efficiency of nitrogen monoxide production are greatly increased. In addition, high-purity nitrogen monoxide production is possible.

In addition, since the nitrogen monoxide of the present invention manufactured by the above method has very high purity, it can be efficiently used in fields requiring high-purity nitrogen monoxide.

Figure 1 illustrates one embodiment of a plant used for producing nitrogen monoxide of the present invention.

The present invention is described in detail below.

The method for producing nitrogen monoxide of the present invention has the characteristics of including the following steps.

1) A step of performing a gas-liquid separation process on a mixed gas generated in a process of producing nitric acid by reacting ammonia and oxygen under conditions of a pressure of 1 to 20 bar and a temperature of -20 to 30°C;

2) A step of supplying the mixed gas separated by the above gas-liquid separation to an adsorption tower filled with an adsorbent to separate impurities;

3) A step of removing the high-temperature substances present in a liquid phase by distilling the mixed gas obtained in the above adsorption step in a high-temperature distillation tower under pressure and temperature conditions where NO can be vaporized;

4) A step of supplying the mixed gas from which the liquid high-boiling substances have been removed to a low-boiling substance distillation tower and removing the gaseous low-boiling substances by distillation under pressure and temperature conditions at which NO is not vaporized; and

5) Step of recovering NO from which the above low-cost substances have been removed.

The mixed gas generated in the process of producing nitric acid by reacting ammonia and oxygen in step 1) above may contain six or more of N _2, O _2, NO, N ₂ O, NO _2, N ₂ O _3, N ₂ O _4, HNO _3, and H ₂ O, and may also contain all of them.

In the above step 1), the gas-liquid separation can be performed under conditions of a pressure of 1 to 20 bar and a temperature of -20 to 20°C using a gas-liquid separator, and preferably under conditions of a pressure of 10 to 20 bar and a temperature of -20 to 20°C. Water, NO ₂ , nitric acid, etc. can be separated and removed by the gas-liquid separator. At this time, component separation by gas-liquid separation under the above pressure and temperature conditions can be efficiently performed advantageously for NO production.

In addition, the above-mentioned gas-liquid separation can be performed under the conditions of a gas-liquid separator at a pressure of 4 to 10 bar and a temperature of 0 to 20° C. Under these conditions, since the nitric acid process is usually operated at 5 to 10 bar, it can be economically advantageous to perform the process at the same or lower pressure.

In the above step 2), the adsorption process is performed by supplying the mixed gas separated in the gas-liquid separator through an adsorbent filled in the adsorption tower, and removing impurities such as trace amounts of water, nitric acid, and NO ₂ through the adsorbent. At this time, the operating conditions of the adsorption tower may be set such that the temperature at the top of the adsorption tower is 22 to 32°C and the temperature at the bottom is 24 to 34°C under a pressure of 5 to 40 bar.

The above adsorbent may be a zeolite, for example, at least one selected from the group consisting of 3A, 4A, 5A, 13X, and Zeolite-Y.

In the above step 3), the pressure and temperature conditions at which NO can be vaporized may be 5 to 20 bar and -130 to -30°C, and more preferably 10 to 20 bar and -110 to -30°C.

The above-mentioned substances may be substances with a boiling point higher than NO, such as _N2O and _CO2 .

The pressure and temperature conditions at which NO is not vaporized in step 4) above may be 5 to 20 bar and -198 to -120°C, more preferably 10 to 20 bar and -160 to -120°C.

The above low-cost substances may be N ₂ , O _{2 ,} etc.

In one embodiment of the present invention, all impurities separated at each step can be sent to the nitric acid manufacturing process and recycled in the nitric acid manufacturing.

In addition, the method for producing nitrogen monoxide of the present invention can be performed including the following steps.

1) A step of performing a gas-liquid separation process on a mixed gas generated in a process of producing nitric acid by reacting ammonia and oxygen under conditions of a pressure of 1 to 20 bar and a temperature of -20 to 20°C;

2) A step of supplying the mixed gas separated by the above gas-liquid separation to an adsorption tower filled with an adsorbent to separate impurities;

3) A step of removing the high-temperature substances present in a liquid phase by distilling the mixed gas obtained in the above adsorption step in a high-temperature distillation tower under pressure and temperature conditions where NO can be vaporized;

4) A step of supplying the mixed gas from which the liquid high-boiling substances have been removed to a low-boiling substance distillation tower, and distilling it under pressure and temperature conditions at which NO is not vaporized to remove the gaseous low-boiling substances;

5) A step of supplying the liquid NO obtained above to an adsorption tower filled with an adsorbent to purify impurities; and

6) Step of recovering purified NO.

Since steps 1) to 4) above can be performed in the same manner as described above, a detailed description is omitted.

In the above step 5), the adsorption process is a process for removing trace impurities contained in the high-purity liquid NO from which low-content substances have been removed in the low-content distillation tower.

Specifically, high-purity liquid NO from which low-content substances have been removed in a low-content distillation tower is supplied to pass through an adsorbent packed in the adsorption tower, and trace amounts of impurities such as N ₂ O and CO ₂ are removed through the adsorbent. At this time, the operating conditions of the adsorption tower may be set such that the temperature at the top of the adsorption tower is -45 to 10°C and the temperature at the bottom is -50 to 10°C under a pressure of 1 to 20 bar.

The above adsorbent may be a zeolite, for example, at least one selected from the group consisting of types 3A, 4A, 5A, 13X and zeolite-Y.

In one embodiment of the present invention, all impurities separated at each step can be sent to the nitric acid manufacturing process and recycled in the nitric acid manufacturing.

Hereinafter, the manufacturing method of the present invention will be specifically explained by way of example through the carbon monoxide manufacturing plant illustrated in Fig. 1.

Crude NO ₂ is supplied (10) from a nitric acid manufacturing reactor (100) where a nitric acid manufacturing process takes place at 1 to 20 bar and a temperature of 20 to 500°C. At this time, the composition of the crude NO supplied at each stage of the nitric acid process is different, but N ₂ is 1 to 99%, and the remaining composition is composed of O ₂ , NO, NO ₂ , N ₂ O, etc. The crude NO supplied in this manner is supplied (10) to a gas-liquid separator (200), and water, NO ₂ , nitric acid, etc. are separated in the gas-liquid separator (200) and the heat exchanger (210). At this time, the pressure is 1 to 20 bar, and the temperature is maintained at -20 to 20°C. The crude NO (20) from which water, nitric acid, and NO ₂ are removed in this manner has a trace amount of water, nitric acid, and NO ₂ removed in an adsorption tower (300) before being supplied to a distillation tower. At this time, trace amounts of moisture and nitric acid are completely removed, and a trace amount of N ₂ O is also adsorbed. The dried crude NO (30) is supplied to a high-volume distillation tower (500), and the remaining N ₂ O and CO ₂ , etc., which are higher in volume than NO, are removed. The crude NO (50) from which the high-volume substances have been removed is supplied to a low-volume distillation tower (600), and N ₂ , O _{2 ,} etc., which are lower in volume than NO, are removed. Thereafter, the high-purity NO (60) is supplied to an adsorption tower (700), and trace amounts of N ₂ O and CO ₂ , etc. are removed (7) by the adsorption process. Thereafter, it passes through a buffer (800) (80) and is charged (1000) into a charging tank through a compressor (900).

The above process can be performed under the following conditions.

　 Press. Temp. (℃ Top Bottom Gas-liquid separator (200,210) 20 -10 -8 Adsorption tower (300) 20 27 29 High-quality distillation tower (500) 20 -104 -30.5 Low-carbon distillation tower (600) 18 -158 -116 Adsorption tower (700) 15 -45 -50 Buffer (800) 15 -20 -20

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited by the following examples. The following examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

Example 1: Nitric acid process gas analysis

In the nitric acid manufacturing process, a mixed gas containing _NO2 and NO was supplied and a mixed gas analysis was performed. The analysis was performed using FT-IR, GC, wet analysis, etc., and the analysis results were as follows.

Press. (Bar) 20 20 10 10 5 5 1 1 Temp. (℃) 450 200 200 50 50 30 150 20 Components
(%) O ₂ 4.8 2.72 2.72 0.427 0.563 0.754 3.58 0.523 N ₂ 68.45 86.44 90.73 92.08 90.79 89.66 80.57 91.22 H ₂ O 16.77 0.63 0.63 0.52 0.914 1.022 10.55 0.777 NO 5.78 7.024 3.025 1.58 2.153 2.758 4.12 2.12 NO ₂ 3.26 2.36 2.016 5.09 5.366 4.985 1.08 5.06 N ₂ O 0.8 0.667 0.8631 0.153 0.187 0.646 0.02 0.288 HNO ₃ 0.14 0.159 0.0159 0.15 0.027 0.175 0.08 0.012

Example 2: NO gas-liquid separation

The mixed gas analyzed in Example 1 was supplied, and moisture, nitric acid, _NO2 , etc. were removed through a gas-liquid separator. At this time, the gas-liquid separator was maintained at 1 to 20 bar and -20 to 20℃ conditions, and a heat exchanger was installed on the top of the gas-liquid separator to maintain the temperature. After the gas-liquid separation, the components were analyzed through GC, FT-IR, and wet analysis, and the analysis results were as shown in Tables 3 to 5 below.

Press. (Bar) Temp. (℃) Components (%) O ₂ N ₂ H ₂ O NO NO ₂ N ₂ O HNO ₃ 20 200 Feed (Gas) 2.72 86.44 0.63 7.024 2.36 0.667 0.159 20 -20 Gas-liquid separation Gas 3.132 87.13 0.001 7.542 0.641 1.553 - Liq. 0.003 0.037 9.463 1.022 79.50 0.744 9.228 20 -10 Gas-liquid separation Gas 3.114 86.62 0.002 7.519 1.185 1.555 0.001 Liq. 0.002 0.028 10.943 0.601 77.07 0.547 10.80 20 0 Gas-liquid separation Gas 3.084 85.81 0.005 7.461 2.083 1.551 0.001 Liq. 0.001 0.020 14.57 0.326 69.64 0.366 15.08 20 20 Gas-liquid separation Gas 3.038 84.51 0.029 7.355 3.525 1.535 0.003 Liq. 0.001 0.009 32.69 0.071 26.95 0.135 40.14 10 -20 Gas-liquid separation Gas 3.124 86.91 0.001 7.537 0.867 1.559 0.000 Liq. 0.002 0.026 10.02 0.723 78.81 0.529 9.884 10 0 Gas-liquid separation Gas 3.063 85.21 0.008 7.413 2.758 1.545 0.001 Liq. 0.001 0.012 19.51 0.200 58.61 0.209 21.46 10 20 Gas-liquid separation Gas 3.034 84.42 0.041 7.347 3.618 1.534 0.005 Liq. - 0.006 35.40 0.049 19.29 0.093 45.16

Press. (Bar) Temp. (℃) Components (%) O ₂ N ₂ H ₂ O NO NO ₂ N ₂ O HNO ₃ 5 50 Feed (Gas) 0.563 90.79 0.914 2.153 5.366 0.187 0.027 5 -20 Gas-liquid separation Gas 0.664 93.73 0.002 2.370 1.639 1.593 - Liq. - 0.016 7.401 0.134 91.32 0.361 0.767 5 -10 Gas-liquid separation Gas 0.655 92.43 0.005 2.342 2.987 1.582 0.001 Liq. - 0.013 8.897 0.081 89.82 0.267 0.922 5 0 Gas-liquid separation Gas 0.642 90.57 0.015 2.298 4.916 1.559 0.001 Liq. - 0.010 12.65 0.049 85.79 0.184 1.319 5 10 Gas-liquid separation Gas 0.629 88.73 0.044 2.253 6.808 1.533 0.002 Liq. - 0.009 22.07 0.031 75.33 0.104 2.458 3 -20 Gas-liquid separation Gas 0.661 93.26 0.003 2.361 2.117 1.593 0.000 Liq. - 0.012 7.874 0.102 90.93 0.270 0.816 3 0 Gas-liquid separation Gas 0.635 89.63 0.024 2.275 5.892 1.547 0.002 Liq. - 0.008 16.21 0.039 81.90 0.120 1.722 3 20 Gas-liquid separation Gas 0.618 87.28 0.178 2.217 8.196 1.510 0.000 Liq. - 0.005 52.10 0.012 38.25 0.024 9.615

Press. (Bar) Temp. (℃) Components (%) O ₂ N ₂ H ₂ O NO NO ₂ N ₂ O HNO ₃ 1 150 Feed (Gas) 3.58 80.57 10.55 4.12 1.08 0.02 0.08 1 -20 Gas-liquid separation Gas 4.453 87.74 0.039 4.803 1.252 1.711 - Liq. - 0.002 25.21 0.031 8.263 0.005 2.948 1 -10 Gas-liquid separation Gas 4.457 87.81 0.093 4.806 1.122 1.712 - Liq. - 0.003 57.686 0.047 9.761 0.005 3.021 1 0 Gas-liquid separation Gas 4.449 87.65 0.199 4.797 1.196 1.709 - Liq. - 0.004 87.82 0.043 9.033 0.005 3.099 1 10 Gas-liquid separation Gas 4.429 87.26 0.394 4.777 1.443 1.701 - Liq. - 0.003 90.42 0.025 6.264 0.004 3.282

Example 3: Drying and removal of impurities using an adsorbent

In Example 2, the mixed gas produced after gas-liquid separation was dried and impurities were removed using an adsorbent.

Specifically, the mixed gas produced after gas-liquid separation was supplied to an adsorption tower filled with MS-13X, MS-5A, or Zeolite-Y, and passed through to remove impurities such as trace amounts of water, nitric acid, _NO2 , etc.

The above results were analyzed using G.C, FT-IR, and wet analysis, and the analysis results were as shown in Table 6 below.

　 Feed MS-13X MS-5A Zeolite-Y Press. (bar) 20 20 30 50 Temp. (℃) -10 35 27 40 Components (%) O ₂ 3.114 4.342 3.539 4.713 N ₂ 86.62 88.823 87.394 89.409 H ₂ O 0.002 - - - NO 7.519 5.375 7.076 4.778 NO ₂ 1.19 0.80 1.02 0.52 N ₂ O 1.555 0.652 0.965 0.579 HNO ₃ 0.001 - - - Etc 0.0040 0.0080 0.0030 0.0010

Example 4: Removal of high and low-density substances

In Example 3, the dried mixed gas was purified by removing high and low boiling points through a distillation tower.

<Process for removing waste>

The above mixed gas was distilled in a high-temperature distillation tower at 15 bar, -124°C at the top, and -20°C at the bottom to remove high-temperature substances existing in a liquid phase.

<Low-cost removal process>

The mixed gas from which the liquid high-boiling substances were removed was distilled in a low-boiling substance distillation tower at 14 bar, -172°C at the top, and -120°C at the bottom to remove the low-boiling substances in the gaseous phase.

After the above purification, the component ratio was analyzed by G.C and FT-IR, and the results were as shown in Table 7 below.

　 Feed High-quality distillation tower
(Removing the sediment) low-carbon distillation tower
(Remove low-cost items) gas Liquid gas Liquid Components (%) O ₂ 3.539 3.618 1.24 3.8594 0.0002 N ₂ 87.397 90.139 1.55 96.14 0.0005 H ₂ O - - - - - NO 7.076 6.242 0.295 0.0000065 99.9993 NO ₂ 1.02 　 0.00998 - - N ₂ O 0.965 0.001 47.114 - - N ₂ O ₃ - - 49.789 - - N ₂ O ₄ - - - - - HNO ₃ - - - - - Etc 0.0030 - 0.01 - -

Example 5: Adsorption purification

An adsorbent was used to remove trace impurities contained in the high-purity NO from Example 4.

Specifically, the NO liquid phase was supplied to an adsorption tower equipped with MS-13X, MS-5A, or Zeolite-Y adsorbent to remove trace amounts of N ₂ O and CO ₂ .

The above results were analyzed using G.C, FT-IR, and wet analysis, and the analysis results were as shown in Table 8 below.

　 Feed MS-3A MS-5A Zeolite-Y Components (%) O ₂ 0.0002 0.0001 0.0001 0.0003 N ₂ 0.0005 0.0006 0.0005 0.0008 H ₂ O - - - - NO 99.9993 99.9993 99.994 99.9989 NO ₂ - - - - N ₂ O - - - - HNO ₃ - - - - Etc - - - -

100: Nitric acid production reactor
200: Gas-liquid separator
210: Heat exchanger
300, 700: Adsorption tower (PSA adsorption tower)
400, 900: Compressor
500: High-altitude distillation tower
600: Low-carbon distillation tower
800: buffer
1000: Charging container

Claims (15)

1) A step of performing a gas-liquid separation process on a mixed gas generated in a process of producing nitric acid by reacting ammonia and oxygen under conditions of a pressure of 10 to 20 bar and a temperature of -20 to 20°C;
2) A step of supplying the mixed gas separated by the above gas-liquid separation to an adsorption tower filled with one or more adsorbents selected from the group consisting of zeolite 3A, 4A, 5A, and Zeolite-Y, and separating impurities by setting the temperature at the top of the adsorption tower to 22 to 32°C and the temperature at the bottom to 24 to 34°C under a pressure of 5 to 40 bar;
3) A step of distilling the mixed gas obtained in the above adsorption step in a high-volume distillation tower under the conditions of a pressure of 5 to 20 bar and a temperature of -130 to -30°C where NO can be vaporized, thereby removing high-volume substances existing in a liquid phase;
4) A step of supplying the mixed gas from which the liquid high-boiling substances have been removed to a low-boiling substance distillation tower and distilling it under the conditions of a pressure of 10 to 20 bar and a temperature of -160 to -120°C at which NO is not vaporized to remove the gaseous low-boiling substances; and
5) A method for producing nitrogen monoxide, comprising: a step of recovering NO from which the above low-carbon substances have been removed. delete delete delete delete delete In the first paragraph,
A method for producing nitrogen monoxide, characterized in that the pressure and temperature conditions at which NO can be vaporized in step 3) above are 10 to 20 bar and -110 to -30°C. delete delete In the first paragraph,
A method for producing nitrogen monoxide, characterized in that the impurities separated in steps 1) to 4) above are recovered by a nitric acid manufacturing process. 1) A step of performing a gas-liquid separation process on a mixed gas generated in a process of producing nitric acid by reacting ammonia and oxygen under conditions of a pressure of 10 to 20 bar and a temperature of -20 to 20°C;
2) A step of supplying the mixed gas separated by the above gas-liquid separation to an adsorption tower filled with one or more adsorbents selected from the group consisting of zeolite 3A, 4A, 5A, and Zeolite-Y, and separating impurities by setting the temperature at the top of the adsorption tower to 22 to 32°C and the temperature at the bottom to 24 to 34°C under a pressure of 5 to 40 bar;
3) A step of distilling the mixed gas obtained in the above adsorption step in a high-volume distillation tower under the conditions of a pressure of 5 to 20 bar and a temperature of -130 to -30°C where NO can be vaporized, thereby removing high-volume substances existing in a liquid phase;
4) A step of supplying the mixed gas from which the liquid high-boiling substances have been removed to a low-boiling substance distillation tower, and distilling it under the conditions of a pressure of 10 to 20 bar and a temperature of -160 to -120°C at which NO is not vaporized, thereby removing the gaseous low-boiling substances;
5) A step of supplying the liquid NO obtained above to an adsorption tower filled with an adsorbent to purify impurities; and
6) A method for producing nitrogen monoxide, comprising: a step of recovering purified NO. delete In Article 11,
A method for producing nitrogen monoxide, characterized in that the impurities separated in steps 1) to 5) above are recovered in a nitric acid manufacturing process. delete delete