A method for removing nitrogen from nitric oxide

Abstract

The present invention discloses a method for removing nitrogen from nitric oxide. Under vacuum conditions, a NO product containing N2 undergoes at least one stage of liquefaction, two stages of liquefaction, one stage of solidification, and two stages of solidification. During this process, NO undergoes at least two stages of liquefaction → gasification, solidification → gasification → solidification at low temperatures, thereby enriching the NO. The N2 remains in a gaseous state and is continuously pumped away by a vacuum pump, thereby achieving the purpose of removing the N2. The present invention removes the N2 by vacuuming during the slow liquefaction and solidification of NO, preventing N2 from being trapped between solid NO molecules and affecting NO purity. It also prevents the liquid NO from flowing or boiling, thereby greatly improving safety.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic special gases, and particularly relates to a method for removing nitrogen from nitric oxide. Background Art

[0002] Nitric oxide is widely used in the chemical industry, electronics industry, aerospace industry, metering standard gas, life sciences and medicine.

[0003] 1) Chemical Industry: In the chemical industry, it can be used to manufacture nitric acid, silicone oxide film and carbonyl nitrosyl. It can also be used as a bleaching agent for rayon, a stabilizer for propylene and dimethyl ether, and an emergency terminator in PVC production.

[0004] 2) Electronics industry: Nitric oxide is mainly used in silicon film formation, oxidation, and chemical vapor deposition.

[0005] 3) Aerospace industry: Nitric oxide can be used as propellant for space rockets and satellites.

[0006] 4) Measurement standard gas: standard gas, calibration gas, atmospheric testing standard mixed gas, environmental protection testing.

[0007] 5) Life science and medical treatment: one is to directly input gaseous nitric oxide for treatment, and the other is to use it as an intermediate for various medicines.

[0008] With the rise and rapid development of the semiconductor industry, the demand for NO is increasing, and the purity requirements are becoming increasingly stringent. In actual production, N₂ accounts for a large proportion of the impurities in NO products. Therefore, providing an efficient method for removing N₂ from NO is of great significance. Existing methods for removing N₂ from NO mainly include distillation (CN115178222A), cryogenic separation (KR20080067701), and freeze-solidification vacuumization (CN111547690A).

[0009] Defects and shortcomings of existing technical solutions:

[0010] The NO distillation process is highly dangerous because liquid NO is very likely to explode when flowing or boiling;

[0011] The freeze-solidification vacuum method is not very effective in removing N2. During the freezing process, N2 is easily trapped between NO solid molecules, and vacuuming cannot completely remove N2. Summary of the Invention

[0012] To overcome the shortcomings of the prior art, the present invention discloses a method for removing nitrogen from nitric oxide. During the process of slow liquefaction and slow solidification of NO, N2 is removed by vacuuming, thereby preventing N2 from being mixed between solid NO molecules and affecting NO purity. It also avoids the liquid NO from flowing or boiling, thereby greatly improving safety.

[0013] To achieve the above technical objectives, the technical solution of the present invention is a method for removing nitrogen from nitric oxide. Under vacuum conditions, a NO product containing N2 undergoes at least one stage of liquefaction, two stages of liquefaction, one stage of solidification, and two stages of solidification. NO undergoes at least two stages of liquefaction → gasification under low temperature, and then solidification → gasification → solidification to be enriched. N2 is always in a gaseous state, and a vacuum pump is used to continuously pump out N2, thereby removing N2 from NO.

[0014] The control temperatures of the first-stage liquefaction, second-stage liquefaction, first-stage solidification and second-stage solidification are respectively: -152 to -162°C, -152 to -162°C, -165 to -175°C and -175 to -185°C.

[0015] The liquefaction temperature is controlled between the melting point (-162° C.) and boiling point (-152° C.) of NO.

[0016] Among them, the first-level liquefaction, second-level liquefaction, first-level solidification and second-level solidification devices use a first-level liquefier, a second-level liquefier, a first-level solidifier, a second-level solidifier and a vacuum pump. The first-level liquefier, the second-level liquefier, the first-level solidifier and the second-level solidifier are all provided with coils, and refrigerant can flow through the coils.

[0017] Before purifying the NO product, the device is first dried and vacuumed.

[0018] After purification is complete, the primary and secondary liquefiers, primary and secondary solidifiers are heated to vaporize the NOx, which is then collected and filled. For safety reasons, the heating of these three processes must be performed slowly to allow the NOx to vaporize. This is because rapidly increasing the temperature can cause excessive local pressure, potentially leading to safety issues.

[0019] Among them, the two-time liquefaction and gasification is that under vacuum conditions, the NO product containing N2 undergoes primary liquefaction, secondary liquefaction, primary solidification, and secondary solidification. NO is enriched through liquefaction → gasification → liquefaction → gasification → solidification → gasification → solidification under the action of low temperature. N2 is always in a gaseous state. A vacuum pump is used to continuously extract N2, thereby removing N2 from NO.

[0020] It is also possible to have more than two liquefaction and vaporization cycles. At low temperatures, NO undergoes two or more cycles of liquefaction, vaporization, solidification, vaporization, and solidification, resulting in enrichment. N2 remains in a gaseous state and is continuously pumped away using a vacuum pump, thereby removing the N2 from the NO. The optimal number of liquefaction and vaporization cycles and conditions can be selected based on a comprehensive consideration of factors such as energy consumption, yield, and cost.

[0021] The principle of the present invention is that at a certain temperature, both liquid and solid NO have a certain saturated vapor pressure. Therefore, under vacuum conditions, liquid and solid NO will continuously vaporize, while N2 remains in a gaseous state within the aforementioned controlled temperature range and does not liquefy or solidify. During the primary and secondary liquefaction processes, the NO vaporization rate is relatively fast because the saturated vapor pressure of NO is 0.36 to 0.9 bar within this temperature range. However, during the primary and secondary solidification processes, the NO vaporization rate is lower. As a result, the loss of NO during the entire N2 removal process is low, and the recovery rate is high.

[0022] This method can be used to purify NO containing N2 to a higher purity.

[0023] The method has simple equipment, low operation difficulty and high yield; the method is safe, efficient and low cost.

[0024] The present invention removes N2 in the NO by vacuuming during the process of slow liquefaction and slow solidification, thereby preventing N2 from being mixed between solid NO molecules and affecting NO purity, and also avoiding the state of liquid NO flowing or boiling, thereby greatly improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow diagram of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present application is further described below in conjunction with specific embodiments, but the present application is not limited to these embodiments.

[0027] The device involved in the present invention includes a primary liquefier, a secondary liquefier, a primary solidifier, a secondary solidifier and a vacuum pump. The primary liquefier, the secondary liquefier, the primary solidifier and the secondary solidifier are all provided with coils, and refrigerant can flow through the coils.

[0028] Before purifying the NO product, the equipment is dried and evacuated. The primary, secondary, and solidifiers are then cooled to a controlled temperature range: -152°C to -162°C, -152°C to -162°C, -165°C to -175°C, and -175°C to -185°C, respectively. Then, under vacuum, NO containing N₂ is introduced, undergoing a process of primary liquefaction, secondary liquefaction, primary solidification, and secondary solidification. During this process, NO is enriched by the low-temperature process of liquefaction, vaporization, liquefaction, vaporization, solidification, vaporization, and solidification. N₂ remains in a gaseous state and is continuously pumped away by the vacuum pump, being removed and purified. After purification, the primary, secondary, solidifiers, and solidifiers are slowly heated to vaporize the NO, which is then collected and filled.

[0029] Example 1

[0030] First, dry the primary liquefier, secondary liquefier, primary solidifier, secondary solidifier and connecting pipelines, turn on the vacuum pump until the system pressure is lower than 1Pa, and then control the temperatures of the primary liquefier, secondary liquefier, primary solidifier and secondary solidifier within the following ranges: -152~-162℃, -152~-162℃, -165~-175℃, -175~-185℃, respectively. Under vacuum conditions, introduce crude nitric oxide product containing N2 (N2 content is about 3000ppm), continuously remove N2 from NO, and after purification, slowly gasify NO in the primary liquefier, secondary liquefier, primary solidifier and secondary solidifier for collection and filling.

[0031] The NO purified product was obtained, and the N2 content was tested to be 38.9 ppm.

[0032] The process of removing nitrogen from nitric oxide is as follows Figure 1 shown.

[0033] Example 2

[0034] Other conditions were the same as those in Example 1. The sample to be purified was a NO sample with an N2 content of about 10,000 ppm. After purification, the N2 content was tested to be 40.2 ppm.

[0035] Comparative Example 1

[0036] First, dry the first-level curing tank, evacuate it, close the vacuum valve, and then control it at -165 ~ -196 ° C, and then pass NO containing N2 (content is about 3000ppm) into it for curing. After stopping the NO product, wait until the NO is completely cured, continue to evacuate for 1 hour, then stop evacuating, slowly vaporize and collect the solid NO, and then test the N2 content, which is 487.4ppm.

[0037] Comparative Example 2

[0038] Other conditions were the same as those in Comparative Example 1, the vacuuming time was 2 h, and the N2 content in the gasified NO was finally measured to be 473.2 ppm.

[0039] Comparative Example 3

[0040] Other conditions were the same as those in Comparative Example 2, the vacuuming time was 4 h, and the N2 content in the gasified NO was finally measured to be 465.1 ppm.

[0041] After purification, the three comparative examples still had at least 400 ppm of N2 content, while the examples of the present invention had a N2 content of only about 40 ppm after purification. This is because the comparative examples all had only one-stage solidification, i.e., direct solidification and vacuum denitrification, and extending the vacuuming time did not significantly reduce the nitrogen content therein, indicating that nitrogen was mixed with the solid nitric oxide. In contrast, the examples of the present invention, through a multi-stage condensation (liquefaction, solidification) → gasification process, released the nitrogen mixed with the condensed nitric oxide and removed it by vacuuming, greatly improving the yield of nitrogen and making the nitric oxide purer.

[0042] The present invention removes nitrogen dioxide (N2) from NO by vacuuming during its slow liquefaction and solidification process, preventing N2 from being trapped between solid NO molecules and affecting NO purity. It also prevents liquid NO from flowing or boiling, significantly improving safety. This method also features simple equipment, low operational complexity, and high yield. It is safe, efficient, and low-cost.

[0043] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the creative concept of the present application, and these all fall within the scope of protection of the present application.

Claims

1. A method for removing nitrogen from nitric oxide, characterized in that: Under vacuum conditions, the NO product containing N2 undergoes at least one-stage liquefaction, two-stage liquefaction, one-stage solidification, and two-stage solidification. NO undergoes at least two stages of liquefaction → gasification, and then solidification → gasification → solidification to be enriched under low temperature. N2 is always in a gaseous state. A vacuum pump is used to continuously extract N2, thereby removing N2 from NO.

2. The method for removing nitrogen from nitric oxide according to claim 1, wherein Under vacuum conditions, the NO product containing N2 undergoes primary liquefaction, secondary liquefaction, primary solidification, and secondary solidification. NO undergoes two liquefaction → gasification under low temperature, and then solidification → gasification and solidification to be enriched. N2 is always in a gaseous state, and the vacuum pump continuously extracts N2, thereby removing N2 from NO.

3. The method for removing nitrogen from nitric oxide according to claim 1 or 2, wherein: The controlled temperatures of the primary liquefaction, secondary liquefaction, primary solidification and secondary solidification are respectively: -152 to -162°C, -152 to -162°C, -165 to -175°C and -175 to -185°C.

4. The method for removing nitrogen from nitric oxide according to claim 1 or 2, wherein: The first-stage liquefaction, second-stage liquefaction, first-stage solidification and second-stage solidification devices adopt a first-stage liquefier, a second-stage liquefier, a first-stage solidifier, a second-stage solidifier and a vacuum pump. The first-stage liquefier, the second-stage liquefier, the first-stage solidifier and the second-stage solidifier are all provided with coils, and refrigerant can flow through the coils.

5. The method for removing nitrogen from nitric oxide according to claim 4, wherein: Before purifying the NO product, the device is dried and vacuumed.

6. The method for removing nitrogen from nitric oxide according to claim 1, wherein: After the purification is completed, the first-stage liquefier, the second-stage liquefier, the first-stage solidifier, and the second-stage solidifier are heated to gasify NO, which is then collected and filled.

Images