A method and apparatus for the production of ammonia

Abstract

The application relates to a method and device for preparing ammonia, belonging to the field of gas absorption and electrochemical reaction, characterized in that the method comprises the following steps: firstly, absorbing nitric oxide gas in a gas flow by using a ferrous sulfate solution to generate a ferrous nitrosyl sulfate compound; then, introducing the ferrous nitrosyl sulfate solution into an electrochemical reactor to reduce nitroso (NO) in the ferrous nitrosyl sulfate into NH4 + ion, obtaining a ferrous ammonium sulfate compound; then, heating the obtained ferrous ammonium sulfate solution to decompose the solution, obtaining an ammonia-containing gas flow and a ferrous sulfate solution; and recycling the obtained ferrous sulfate solution. The related device comprises a nitric oxide absorption tower, an electrochemical reactor, an ammonia desorption tower and pipeline components.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing ammonia, belonging to the field of gas absorption and electrochemical reaction. Background Technology

[0002] Ammonia is an important inorganic compound used as a refrigerant, reducing agent, and fuel, and is also widely used in the production of fertilizers, pharmaceuticals, and chemicals. Industrially, ammonia is synthesized via the Haber process, which involves the direct synthesis of nitrogen and hydrogen under high temperature, high pressure, and in the presence of a catalyst. While this method is mature, it requires high temperatures or pressures, resulting in high investment and operating costs.

[0003] Ammonia can be prepared by reducing nitric oxide (NO) through electrochemical reactions. A Chinese patent document (CN113789526A) discloses a method for recovering ammonia by combining NO complexation absorption with electrocatalytic reduction. The absorbent is ferrous ethylenediaminetetraacetate (Fe(II)EDTA) solution. However, these organic compounds are prone to decomposition during the electrochemical reaction. Another problem is that ferrous iron is easily oxidized during the denitrification process, which leads to a decrease in the denitrification rate of the absorbent or its failure. Therefore, it is difficult to apply in industrial practice.

[0004] This invention proposes a method and apparatus for preparing ammonia, which combines the denitrification process with the electrochemical reduction ammonia production process to overcome the above-mentioned shortcomings and achieve simultaneous and efficient denitrification and ammonia synthesis. Summary of the Invention

[0005] A method for preparing ammonia, characterized in that the method involves first absorbing nitric oxide gas from a gas stream with a ferrous sulfate solution to react and generate a ferrous nitrosyl sulfate compound, and then introducing the ferrous nitrosyl sulfate solution into an electrochemical reactor to reduce the nitrosyl (NO) in the ferrous nitrosyl sulfate to NH4. ＋ The ions are used to obtain ferrous ammonium sulfate compound. Then, the obtained ferrous ammonium sulfate solution is heated to decompose it, and an ammonia-containing gas stream and ferrous sulfate solution are obtained. The regenerated ferrous sulfate solution is recycled. The main reaction is shown in formula (1). The reaction yields a complex at low temperature and desorbs at high temperature.

[0006] FeSO4+NO ↔ Fe(NO)SO4 (1)

[0007] The apparatus for ammonia preparation according to the present invention mainly comprises a nitric oxide absorption tower 1, a gas circulation pipe 2, a nitric oxide gas replenishment port 3, a post-ammonia removal absorbent delivery pipe 4, a first heat exchanger 5, an ammonia desorption tower 6, an ammonia outlet 7, a post-reaction absorbent delivery pipe 8, a second heat exchanger 9, a power supply 10, a gas outlet 11, a replenishment liquid inlet 12, an electrochemical reactor 13, an anode chamber 14, a cathode chamber 15, an absorbent delivery pipe 16, and an absorbent replenishment port 17. The top and lower side of the nitric oxide absorption tower 1 are connected by the gas circulation pipe 2, which has a nitric oxide gas replenishment port 3. The bottom of the nitric oxide absorption tower 1 is connected to the cathode chamber 15 of the electrochemical reactor 13 via the absorbent delivery pipe 16. The anode chamber 14 of the electrochemical reactor 13 has a replenishment liquid inlet 12 and a gas outlet 11. The negative terminal of the power supply 10 is connected to the cathode electrode of the cathode chamber 15 of the electrochemical reactor 13, and the positive terminal is connected to the anode electrode inside the anode chamber 14. The cathode chamber 15 of the electrochemical reactor is connected to the upper side of the ammonia desorption tower 6 through the post-reaction absorbent delivery pipe 8. The bottom of the ammonia desorption tower 6 is connected to the upper side of the nitric oxide absorption tower 1 through the post-ammonia removal absorbent delivery pipe 4. The lower side of the ammonia desorption tower 6 is also provided with an absorbent replenishment port 17. The post-ammonia removal absorbent delivery pipe 4 and the post-reaction absorbent delivery pipe 8 are respectively equipped with a first heat exchanger 5 and a second heat exchanger 9.

[0008] The process flow is as follows: First, a predetermined amount and concentration of ferrous sulfate absorbent is added to the ammonia desorption tower 6 through absorbent replenishment port 17. Then, after being cooled by the first heat exchanger 5, the absorbent liquid after ammonia removal is transported to the nitric oxide absorption tower 1 through the absorbent liquid transport pipe 4. In the nitric oxide absorption tower 1, a gas-liquid contact reaction is carried out with the gas flow containing nitric oxide to obtain a ferrous sulfate nitrosyl sulfate solution. After the reaction, the gas is discharged through the top of the tower and recycled through the gas circulation pipe 2. Nitric oxide gas can be replenished through the nitric oxide gas replenishment port 3. After the reaction, the ferrous sulfate nitrosyl sulfate solution is transported to the cathode chamber 15 of the electrochemical reactor through the absorbent transport pipe 16. The ferrous sulfate nitrosyl sulfate is converted into ferrous ammonium sulfate through an electrochemical reaction. Then, after being heated by the second heat exchanger 9 through the absorbent liquid transport pipe 8, it is transported to the ammonia desorption tower 6. In the ammonia desorption tower 6, the desorbed ammonia gas is distilled and sent to the next process through the ammonia gas outlet 7. During the electrochemical reaction process, the oxygen generated in the anode chamber 14 of the electrochemical reactor 13 is discharged through the gas outlet 11. The electrolyte consumed in the anode chamber can be replenished through the replenishment inlet 12, such as water and hydrochloric acid solution.

[0009] The nitric oxide gas flow described in this invention uses an inert gas as the carrier gas, including nitrogen and argon, and may also contain reducing gases such as hydrogen (content is not specifically required, preferably 0.5-10%). The concentration of nitric oxide gas in the flow is not specifically required; considering both conversion rate and safety, 1-20% is preferred. The nitric oxide absorption tower and ammonia desorption tower can use common gas-liquid mass transfer equipment such as spray towers, packed towers, bubble towers, and plate towers; specific details can be found in relevant chemical equipment manuals. The mass content of ferrous sulfate in the nitric oxide absorption liquid is not specifically required, preferably 10%-30%, and can be higher at higher temperatures. The operating temperature of the nitric oxide absorption tower is generally below 90℃ under normal pressure, preferably 40-70℃, and can be higher under increased pressure; the operating temperature of the ammonia desorption tower is generally above 90℃, preferably 110-130℃, and can be lower under reduced pressure.

[0010] The electrochemical reactor consists of an anode chamber and a cathode chamber, separated by a proton exchange membrane to allow hydrogen ions to pass through. The anode material is typically an oxygen evolution electrode, which can be one or a combination of platinum, palladium, ruthenium, Pb, or graphite, with platinum showing the best performance. The cathode uses electrode materials with catalytic reduction properties, mainly including one or a combination of platinum, copper, iron (stainless steel), zinc, nickel, titanium, and silver, with platinum, copper, and silver showing the best performance. For details, refer to relevant electrochemical electrode material handbooks. The operating temperature of the electrochemical reactor is generally below 90℃, preferably 40–70℃, and can be higher under increased pressure. The pH value of the absorbent ferrous nitrosyl sulfate solution is generally below 7, preferably 0.5–2.5, to facilitate the cathode electrode reaction. The electrolyte in the anode chamber is a sulfuric acid or hydrochloric acid metal salt solution, preferably a sulfate solution, mainly including sodium sulfate, potassium sulfate, sodium chloride, and potassium chloride. Electrochemical reactors can use constant voltage or constant current power supply for electrolysis, so that nitrosyl groups are catalytically reduced to ammonium ions on the surface of the cathode electrode. Generally, the reduction potential of the cathode material is -0.5 to -1.5V (vs. RHE), which depends on the selected electrode material.

[0011] The ferrous sulfate described in this invention can also be replaced by a solution of sulfate or hydrochloride of copper (including cuprous), cobalt, or nickel, or a solution of ferrous chloride, which undergoes a complexation reaction with nitric oxide. The working principle is the same, and the working conditions and effects are roughly equivalent.

[0012] The desorbed ammonia gas is purified through processes such as drying, dehydration, purification, and compression to obtain pure ammonia product (gas or liquid). The ferrous sulfate solution obtained after desorption is recycled.

[0013] Compared with existing technologies, this invention utilizes the complexation reaction of inorganic salts such as ferrous sulfate with nitric oxide to synthesize ammonia under acidic conditions through an electrochemical reaction. The ammonia conversion rate is more than 30% higher than that under traditional alkaline conditions. The absorbent is recycled, the process is simple, green and clean, with no secondary pollution, high reaction conversion rate and energy utilization efficiency, and low operating costs. Attached Figure Description

[0014] Figure 1 A diagram of an apparatus for preparing ammonia.

[0015] In the diagram: 1. Nitric oxide absorption tower; 2. Gas circulation pipe; 3. Nitric oxide gas replenishment port; 4. Absorbent delivery pipe after ammonia removal; 5. First heat exchanger; 6. Ammonia desorption tower; 7. Ammonia outlet; 8. Absorbent delivery pipe after reaction; 9. Second heat exchanger; 10. Power supply; 11. Gas outlet; 12. Replenishment liquid inlet; 13. Electrochemical reactor; 14. Anode chamber; 15. Cathode chamber; 16. Absorbent delivery pipe; 17. Absorbent replenishment port. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0017] A nitrogen oxide preparation apparatus mainly consists of a nitric oxide absorption tower 1, a gas circulation pipe 2, a nitric oxide gas supply port 3, a deammoniation absorbent delivery pipe 4, a first heat exchanger 5, an ammonia desorption tower 6, an ammonia outlet 7, a reaction absorbent delivery pipe 8, a second heat exchanger 9, a power supply 10, a gas outlet 11, a replenishment liquid inlet 12, an electrochemical reactor 13, an anode chamber 14, a cathode chamber 15, an absorbent delivery pipe 16, and an absorbent supply port 17. The top and lower side of the nitric oxide absorption tower 1 are connected by the gas circulation pipe 2, which has a nitric oxide gas supply port 3. The bottom of the nitric oxide absorption tower 1 is connected to the cathode chamber 15 of the electrochemical reactor 13 via the absorbent delivery pipe 16. The anode chamber 14 of the electrochemical reactor 13 has a replenishment liquid inlet 12 and a gas outlet 11. The negative terminal of the power supply 10 is connected to the cathode electrode of the cathode chamber 15 of the electrochemical reactor 13, and the positive terminal is connected to the anode electrode in the anode chamber 14 of the electrochemical reactor. The cathode chamber 15 of the electrochemical reactor is connected to the upper side of the ammonia desorption tower 6 through the post-reaction absorbent delivery pipe 8. The bottom of the ammonia desorption tower 6 is connected to the upper side of the nitric oxide absorption tower 1 through the post-ammonia removal absorbent delivery pipe 4. The lower side of the ammonia desorption tower 6 is also provided with an absorbent replenishment port 17. The post-ammonia removal absorbent delivery pipe 4 and the post-reaction absorbent delivery pipe 8 are respectively equipped with a first heat exchanger 5 and a second heat exchanger 9.

[0018] The process flow is as follows: First, a predetermined amount and concentration of ferrous sulfate absorbent is added to the ammonia desorption tower 6 through absorbent replenishment port 17. Then, after being cooled by the first heat exchanger 5, the absorbent liquid after ammonia removal is transported to the nitric oxide absorption tower 1 through the absorbent liquid transport pipe 4. In the nitric oxide absorption tower 1, the absorbent reacts with the gas-liquid containing nitric oxide to obtain a ferrous sulfate nitrosyl sulfate solution. After the reaction, the gas is discharged through the top of the tower and recycled through the gas circulation pipe 2. Nitric oxide gas can be replenished through the nitric oxide gas replenishment port 3. The ferrous sulfate nitrosyl sulfate solution obtained after the reaction is transported to the cathode chamber 15 of the electrochemical reactor through the absorbent transport pipe 16. The ferrous sulfate nitrosyl sulfate is converted into ferrous ammonium sulfate through an electrochemical reaction. Then, after being heated by the second heat exchanger 9 through the absorbent liquid transport pipe 8, the solution is transported to the ammonia desorption tower 6. In the ammonia desorption tower 6, the ammonia gas is desorbed and distilled under reduced pressure and sent to the next process through the ammonia gas outlet 7. The oxygen or chlorine produced in the anode chamber 14 during the electrochemical reaction process is discharged through the gas outlet 11, and the electrolyte consumed in the anode chamber can be replenished through the replenishment inlet 12.

[0019] Example 1: An ammonia preparation apparatus, such as Figure 1 As shown. The electrochemical reactor is an H-type electrolytic cell made of quartz glass, with external dimensions of 100×160×250 mm (length×width×height). The anode and cathode chambers are separated by a Nafion-117 proton exchange membrane. The anode uses a ruthenium-titanium mesh electrode, and the cathode uses a sponge copper electrode. Constant potential electrolysis is performed, with a reduction potential voltage of -0.9V (vs. RHE) and a current density of approximately 40–60 mA / cm². 2 The cathode chamber liquid flow rate is approximately 100 ml / min, and the anolyte is a 0.5 mol / L sodium sulfate solution. The electrochemical reactor operates at approximately 50°C. The nitric oxide absorption tower is a 60 mm diameter quartz glass packed tower with ceramic packing. The packing layer height is approximately 40 mm. The initial gas flow concentration of nitric oxide is approximately 1–2%, with the remainder being nitrogen. It operates at atmospheric pressure, with a gas circulation flow rate of approximately 1–2 L / min and a liquid spray rate of approximately 100 ml / min. The absorption tower operates at approximately 40–50°C. The absorbent is a 30% ferrous sulfate solution, initially added at approximately 3 L, with the pH adjusted to 1 by adding dilute sulfuric acid. The ammonia desorption tower has essentially the same structural dimensions as the nitric oxide absorption tower, operates at approximately 110°C, and uses a slight negative pressure to extract the desorbed ammonia. After stable operation, the ammonia conversion rate of nitric oxide was measured to be 15–25%.

[0020] Example 2: An Ag plating layer (electrochemical method) with a thickness of approximately 1 micrometer was added to the surface of the cathode copper electrode described in Example 1. The pH of the ferrous sulfate absorbent was adjusted to 0.5 by adding dilute sulfuric acid. The initial gas flow contained approximately 5% nitric oxide and 1% hydrogen, with other conditions remaining the same as in Example 1. After stable operation, the ammonia conversion rate of nitric oxide was measured to be 20-35%.

[0021] Example 3: Cobalt sulfate absorbent was used instead of ferrous sulfate. The pH of the absorbent was adjusted to 2.5 by adding dilute sulfuric acid. The anolyte was a 0.2 mol / L sodium chloride solution. Other conditions were the same as in Example 1. After stable operation, the ammonia conversion rate of nitric oxide was measured to be 10-15%.

[0022] The above embodiments are only used to illustrate the technical solutions of the present invention. For those skilled in the art, any modifications to the technical solutions described in the embodiments, or any equivalent substitutions, modifications, changes and improvements to some of the technical features within the spirit and principles of the present invention, should be included within the protection scope of the present invention.

Claims

1. A method for the production of ammonia, characterized in that The method comprises the following steps: first, absorbing the nitric oxide gas in the gas stream by a ferrous sulfate solution to generate a ferrous nitrosyl sulfate compound; second, introducing the ferrous nitrosyl sulfate solution into an electrochemical reactor to reduce the nitroso group in the ferrous nitrosyl sulfate to ammonium ion to obtain a ferrous ammonium sulfate compound; and third, heating the obtained ferrous ammonium sulfate solution to decompose it to obtain an ammonia-containing gas stream and a ferrous sulfate solution, and recycling the obtained ferrous sulfate solution.

2. The method of claim 1, wherein The gas stream uses inert gas as carrier gas, including nitrogen and argon, or inert gas containing reducing gas hydrogen.

3. The process for the production of ammonia according to claim 1 or 2, characterized in that The concentration of the nitric oxide in the gas stream is 1-20%.

4. The process for the production of ammonia according to claim 1, characterized in that The pH value of the ferrous sulfate absorption solution is below 7.

5. The process for the production of ammonia according to claim 1 or 4, characterized in that The ferrous sulfate solution is replaced by a copper sulfate solution, a cobalt sulfate solution, a nickel sulfate solution or a ferrous chloride solution.

6. The apparatus for the production of ammonia according to claim 1, characterized in that The device comprises a nitric oxide absorption tower (1), a gas circulation pipe (2), a nitric oxide gas supplement port (3), a deamination absorption solution conveying pipe (4), a first heat exchanger (5), an ammonia desorption tower (6), an ammonia gas outlet (7), a post-reaction absorption solution conveying pipe (8), a second heat exchanger (9), a power supply (10), a gas discharge port (11), a supplement liquid inlet (12), an electrochemical reactor (13), an anode chamber (14), a cathode chamber (15), an absorption solution conveying pipe (16) and an absorbent supplement port (17). The top and the lower side of the nitric oxide absorption tower (1) are connected by the gas circulation pipe (2), and the gas circulation pipe (2) is provided with the nitric oxide gas supplement port (3). The bottom of the nitric oxide absorption tower (1) is connected with the cathode chamber (15) of the electrochemical reactor (13) through the absorption solution conveying pipe (16). The anode chamber (14) of the electrochemical reactor (13) is provided with the supplement liquid inlet (12) and the gas discharge port (11). The negative electrode of the power supply (10) is connected with the cathode electrode of the cathode chamber (15), and the positive electrode is connected with the anode electrode in the anode chamber (14). The cathode chamber (15) is connected with the upper side of the ammonia desorption tower (6) through the post-reaction absorption solution conveying pipe (8). The bottom of the ammonia desorption tower (6) is connected with the upper side of the nitric oxide absorption tower (1) through the deamination absorption solution conveying pipe (4). The lower side of the ammonia desorption tower (6) is further provided with the absorbent supplement port (17). The deamination absorption solution conveying pipe (4) and the post-reaction absorption solution conveying pipe (8) are respectively provided with the first heat exchanger (5) and the second heat exchanger (9).

7. A process or an apparatus for the production of ammonia according to claim 1 or 4, characterized in that The electrochemical reactor comprises an anode chamber and a cathode chamber, and the two chambers are separated by a proton exchange membrane. The anode material is one or more of platinum, palladium, ruthenium, Pb or graphite, and the cathode material is one or more of platinum, copper, iron (stainless steel), zinc, nickel, titanium and silver.

8. The apparatus for the production of ammonia according to claim 6, characterized in that The process of the device is that the predetermined amount and concentration of ferrous sulfate absorbent is added into ammonia desorption tower (6) through absorbent supplement port (17), then is transported to nitric oxide absorption tower (1) through deamination absorption liquid delivery pipe (4) after cooling by first heat exchanger (5), and is reacted with gas stream containing nitric oxide in nitric oxide absorption tower (1) to obtain ferrous sulfate nitrite solution, the reacted gas is discharged through the top of the tower and is recycled through gas circulation pipe (2), the nitric oxide gas can be supplemented through nitric oxide gas supplement port (3), the obtained solution containing ferrous sulfate nitrite after reaction is transported to cathode chamber (15) of electrochemical reactor (13) through absorption liquid delivery pipe (16), then ferrous sulfate nitrite is converted into ferrous ammonium sulfate through electrochemical reaction, and then is transported to ammonia desorption tower (6) through absorption liquid delivery pipe (8) after heating by second heat exchanger (9), and ammonia gas desorbed by pressure reduction distillation in ammonia desorption tower (6) is sent to the next process through ammonia gas outlet (7), oxygen generated in anode chamber (14) of electrochemical reactor (13) during electrochemical reaction is discharged through gas discharge port (11), and electrolyte consumed in anode chamber can be supplemented through supplement liquid inlet (12). The working temperature of the nitric oxide absorption tower is below 90℃ under normal pressure, and the working temperature of the ammonia desorption tower is generally above 90℃.

9. The apparatus for the production of ammonia according to claim 6, characterized in that The working temperature of the electrochemical reactor is below 90℃.

10. The apparatus for the production of ammonia according to claim 6, characterized in that The working temperature of the electrochemical reactor is below 90℃.

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