Nitrogen oxide pressurized absorption system and process

Abstract

The invention discloses a nitrogen oxide pressurized absorption system and process, and belongs to the technical field of nitrogen oxide tail gas treatment. The method comprises the following steps: mixing nitrogen oxide-containing gas with air or pure oxygen to form mixed gas, pressurizing the mixed gas to 0.6-1 MPa, and then feeding the mixed gas into a reaction device for oxidation reaction; absorbing nitrogen oxides in the mixed gas after the oxidation reaction by adopting a dilute nitric acid absorption method, further absorbing residual nitrogen oxides in the mixed gas after the absorption by adopting the dilute nitric acid absorption method by adopting a water absorption method, and discharging the mixed gas after the absorption by virtue of a tail gas discharging device with the NOx concentration of 1t; and the concentration is 200 ppm. The problems that in an existing normal-pressure dilute nitric acid absorption method, the NOx absorption efficiency is low, tail gas cannot reach the standard for emission, and standard emission can be achieved only by serial alkali absorption or SCR further treatment are solved.

Description

Technical Field

[0001] This invention relates to the field of nitrogen oxide exhaust gas treatment technology, specifically to a nitrogen oxide pressurized absorption system and process. Background Technology

[0002] Nitrogen oxides, primarily nitric oxide and nitrogen dioxide, are a major contributor to acid rain and photochemical smog. Currently, most treatments for nitrogen oxide emissions utilize alkaline absorption, acid absorption, or selective catalytic reduction (SCR) technologies. Alkaline absorption typically employs traditional multi-stage alkaline scrubbing methods, which are costly and generate large amounts of secondary saline wastewater. Selective catalytic reduction uses ammonia or urea as a reducing agent to treat lower concentrations of industrial nitrogen oxides (NOx). x The technology for treating NO2 exhaust gases is very mature and widely used. However, selective catalytic reduction (SCR) technology has limitations in treating NO2 concentrations over a wide range or at high concentrations. x NO is present in the exhaust gas. x Problems include excessive emissions, severe ammonia escape, and high treatment costs due to the consumption of large amounts of reducing agents.

[0003] Acid absorption methods can be divided into dilute nitric acid absorption and concentrated sulfuric acid absorption. Concentrated sulfuric acid absorption introduces a new medium, and sulfuric acid has strong oxidizing and corrosive properties. Because NO... x The solubility of nitric acid in nitric acid concentrations above 12% is much greater than in water, and no secondary pollutants are introduced. The absorbed liquid can also be further concentrated to recover nitric acid. The main disadvantage of the common atmospheric pressure dilute nitric acid absorption method is the presence of NO. x The absorption efficiency is low, and the exhaust gas cannot meet the emission standards. Further treatment, such as series alkaline absorption or SCR, is required to achieve NO emission reduction. x Concentration <200ppm, exhaust gas meets emission standards. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the prior art and provide a new process and system for catalytic oxidation coupled with pressure absorption of nitrogen oxides. This process and system offers high absorption efficiency, eliminates the need for tandem alkaline absorption or SCR further treatment, and allows for NO control over a wide pressure range of 0.6 MPa to 1 MPa depending on operating conditions. x Highly efficient absorption can eliminate NO in exhaust gases. x Concentration <200ppm and emissions meet standards.

[0005] The present invention provides a pressure absorption process for nitrogen oxides, comprising the following steps: Nitrogen oxide gas is mixed with air or pure oxygen to form a mixed gas. The mixed gas is pressurized to 0.6 MPa to 1 MPa and then enters the reaction device for oxidation reaction. When the pressure of the pressurized mixed gas is lower than 0.8 MPa, a catalyst is required to be added to the reaction device to promote the oxidation reaction. The nitrogen oxides in the mixed gas after the oxidation reaction are absorbed by dilute nitric acid. The remaining nitrogen oxides are then further absorbed by water. The resulting NO mixture... x Concentration <200ppm.

[0006] Preferably, when using dilute nitric acid to absorb nitrogen oxides in a mixed gas, the liquid flow rate is controlled throughout the absorption process: the gas flow rate is 1:1 to 50:1, and the temperature of the absorbent is 0℃ to 60℃.

[0007] Preferably, when using water absorption to absorb nitrogen oxides in a mixed gas, the liquid flow rate is controlled throughout the absorption process: the gas flow rate is 1:1 to 50:1, and the temperature of the absorption liquid is 0℃ to 60℃.

[0008] Preferably, when using dilute nitric acid absorption to absorb nitrogen oxides in a mixed gas, after adsorption, when the concentration of nitric acid in the absorbent is 40% to 50%, the absorbent is collected or concentrated and purified into a nitric acid product.

[0009] The present invention also provides a system for the above-described pressurized absorption process of nitrogen oxides, comprising: A gas compression device, with its inlet end connected to a nitrogen oxide exhaust gas delivery pipeline and an air or oxygen delivery pipeline, is used to pressurize the mixture of nitrogen oxide exhaust gas and air or oxygen. The reaction apparatus is connected to the output pipeline of the gas compression device and is used to carry out an oxidation reaction of the mixed gas. An acid absorption tower is connected to the output pipeline of the reaction device. The top of the acid absorption tower is equipped with a first spray head, which is connected to a dilute nitric acid supply pipeline. The bottom is connected to a mixed gas input pipeline. The mixed gas and the dilute nitric acid absorption liquid are in counter-current contact. The top of the acid absorption tower is equipped with a first gas output pipeline. The water absorption tower is connected at its bottom to the first gas output pipeline of the acid absorption tower. The top of the water absorption tower is equipped with a second spray head, which is connected to a water supply pipeline. The top of the water absorption tower is also equipped with a second gas output pipeline.

[0010] Preferably, the bottom of the acid absorption tower is provided with a first adsorbent collection device, which is connected to the first spray head through a first circulation pipeline.

[0011] Preferably, a second adsorbent collection device is connected to the bottom of the water absorption tower. The second adsorbent collection device is connected to the second spray head through a second circulation pipeline. The second adsorbent collection device is also connected to the first circulation pipeline through an acid delivery pipeline.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The nitrogen oxide pressurized absorption process of the present invention mixes nitrogen oxide-containing gas with air or pure oxygen to form a mixed gas, pressurizes the mixed gas and performs a catalytic oxidation reaction, and then uses dilute nitric acid absorption and water absorption methods to absorb the nitrogen oxides in the mixed gas, thereby achieving the standard emission of exhaust gas and avoiding the NO present in the existing atmospheric pressure dilute nitric acid absorption method. x The absorption efficiency is low, and the exhaust gas cannot meet emission standards. Further treatment, such as series alkaline absorption or SCR, is required to achieve compliance. Furthermore, compared to conventional high-pressure acid absorption methods, it significantly reduces the amount of non-NOx compressed gas that can be emitted. x Energy consumption of gases.

[0013] This invention uses NO x The catalytic oxidation and pressurized nitric acid absorption methods improved NO x This improves oxidation efficiency, reduces the compression ratio of existing pressurized dilute nitric acid absorption methods, and enables NO to be absorbed within a wide pressure range of 0.6 MPa to 1 MPa. x Recycling nitric acid reduces the impact of large-volume NO production. x The cost of pressurizing and absorbing the intake air is reduced, thereby lowering equipment and operating costs, achieving compliant emissions of exhaust gas, and producing dilute nitric acid as a byproduct, thus improving the overall economic efficiency of the process.

[0014] Currently, the commonly used SCR catalytic method in industry mainly catalyzes the direct conversion of NO into harmless nitrogen and water. However, this invention focuses on catalyzing the oxidation of NO into more easily absorbed NO2, which is then rapidly absorbed by nitric acid. Compared with the SCR catalytic method and the general pressurized nitric acid absorption method, the catalytically coupled pressurized nitric acid absorption method of this invention not only reduces the cost of gas compression, but also recovers harmful nitrogen oxide tail gas into economically valuable crude nitric acid product, achieving the transformation of waste into treasure and the resource utilization of waste, and responding to the national concepts of green chemistry and circular economy. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the nitrogen oxide pressure absorption process according to an embodiment of the present invention.

[0016] Figure 2 The absorption rates are for each embodiment and comparative example of the present invention.

[0017] Figure 3 The values ​​represent the exhaust gas concentrations at different pressures for products with and without catalyst.

[0018] Figure 4 The values ​​represent the exhaust gas concentrations at different temperatures with and without catalyst.

[0019] Explanation of reference numerals in the attached figures: 1. Gas compression device; 2. Nitrogen oxide tail gas delivery pipeline; 3. Air or oxygen delivery pipeline; 4. Reaction device; 5. Acid absorption tower; 51. First spray head; 52. Dilute nitric acid supply pipeline; 53. Mixed gas input pipe; 54. First gas output pipeline; 55. First circulation pipeline; 6. Water absorption tower; 61. Second spray head; 62. Second gas output pipeline; 63. Second circulation pipeline; 64. Acid delivery pipeline; 7. Gas detection unit; 8. First adsorbent collection; 9. Second adsorbent collection device; 10. Acid source; 11. Water source. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0021] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described objects changes, the relative positional relationship may also change accordingly.

[0022] This embodiment discloses a pressurized absorption process for nitrogen oxides, including the following steps: Nitrogen oxide-containing gas is mixed with air or pure oxygen to form a mixed gas. Air or pure oxygen oxidizes the nitrogen oxide-containing gas. In this embodiment, the nitrogen oxide-containing gas generally has a nitrogen oxide content of 5% to 30%. Optionally, a gas detection system can be used to detect the initial nitrogen oxide concentration in the mixed gas to determine its concentration. In this embodiment, the mixed gas is pressurized to 0.6 MPa to 1 MPa before entering reaction device 4. A catalytic oxidation reaction occurs under the action of a catalyst, ensuring complete oxidation of the nitrogen oxides in the mixed gas. The catalyst in this embodiment can be a manganese-supported activated carbon catalyst, a platinum-supported titanium dioxide catalyst, or a cobalt-cerium bimetallic catalyst. The pressure of the mixed gas after the oxidation reaction is not lower than 0.6 MPa. In this embodiment, the pressure of reaction device 4 is equal to the pressure of the acid absorption tower, i.e., the pressure of acid absorption tower 5 is 0.6 MPa to 1 MPa. Preferably, when the pressure of reaction device 4 or acid absorption tower 5 is lower than 0.8 MPa, a catalyst is added to reaction device 4 to improve the absorption efficiency of the absorption tower by increasing the nitrogen oxide oxidation efficiency.

[0023] In this embodiment, the nitrogen oxides in the mixed gas after the oxidation reaction are absorbed using dilute nitric acid. The mixed gas after absorption by dilute nitric acid is then pressurized and further absorbed using water absorption. The resulting NO2 mixture... x If the concentration is less than 200 ppm, it meets the emission standards and can be discharged through the exhaust gas emission device.

[0024] This embodiment uses NO x Catalytic oxidation and pressurized nitric acid absorption enable NO removal over a wide pressure range. x Recovering and producing nitric acid. This method not only increases NO content... x The oxidation efficiency was improved, and the oxidation of large flow rates of NO was also reduced. x Reduce the cost of intake compression, thereby lowering equipment operating costs and achieving compliant exhaust emissions.

[0025] As a preferred embodiment of this invention, when using dilute nitric acid absorption to absorb nitrogen oxides in a mixed gas, the gas flow rate is controlled at 1 L / m³ throughout the absorption process. 3 ~50L / m 3 The temperature of the acid absorption solution is 0℃~60℃. This embodiment, by controlling the gas flow rate and temperature during the absorption process, not only ensures absorption efficiency but also maintains the gas-liquid ratio, avoiding the problem of excessive resource consumption due to both high gas and high liquid flow rates.

[0026] As another preferred embodiment, when using water absorption to absorb nitrogen oxides in a mixed gas, the gas flow rate is controlled at 1 L / m³ throughout the absorption process.3 ~50L / m 3 This also ensures absorption efficiency and maintains the gas-liquid ratio, avoiding the problem of excessive resource consumption caused by excessive gas flow and liquid flow.

[0027] As another preferred embodiment, the dilute acid liquid obtained when absorbing nitrogen oxides in the mixed gas using the water absorption method is used as the absorbent to achieve dilute acid circulation absorption. When the concentration of nitric acid in the absorbent reaches 10% to 20% after circulation absorption, the nitric acid absorbent with a concentration of 10% to 20% is used to replenish the acid source 10 of the dilute nitric acid absorption method.

[0028] As another preferred embodiment, when using dilute nitric acid absorption to absorb nitrogen oxides in a mixed gas, if the nitric acid concentration in the absorbent is 40% to 50% after adsorption, the absorbent is collected or concentrated and purified into nitric acid product. The byproduct nitric acid product can improve the overall economic efficiency of the process.

[0029] like Figure 1 As shown, this embodiment also provides a system for the above-mentioned nitrogen oxide pressurization absorption process. The system includes a gas compression device 1, the inlet of which is connected to a nitrogen oxide tail gas conveying pipeline 2 and an air or oxygen conveying pipeline 3, for pressurizing the mixture of nitrogen oxide tail gas and air or oxygen. The reaction device 4 is connected to the output pipeline of the gas compression device 1 and is used to carry out an oxidation reaction of the mixed gas. The acid absorption tower 5 is connected to the output pipeline of the reaction device 4. The top of the acid absorption tower 5 is provided with a first spray head 51. The first spray head 51 is connected to a dilute nitric acid supply pipeline 52, and the bottom is connected to a mixed gas input pipeline 53. The mixed gas and the absorption liquid are in counter-current contact. The top of the acid absorption tower 5 is provided with a first gas output pipeline 54. The water absorption tower 6 is connected at its bottom to the first gas output pipe 54 of the acid absorption tower 5. The top of the water absorption tower 6 is equipped with a second spray head 61, which is connected to a water supply pipe. The top of the water absorption tower 6 is also equipped with a second gas output pipe 62. Preferably, the second gas output pipe 62 is connected to a gas detection unit 7. When the gas detection unit 7 detects that the gas in the second gas output pipe 62 meets the standard, it is discharged. It should be noted that the gas in the second gas output pipe 62 after being treated according to the method of this embodiment meets the standard. If the gas does not meet the standard, it is returned to the mixed gas before pressurization.

[0030] As a preferred embodiment of this embodiment, the bottom of the acid absorption tower 5 is provided with a first adsorption liquid collection device 8, which is connected to the first spray head 51 through a first circulation pipeline 55.

[0031] In a preferred embodiment of this embodiment, the bottom of the water absorption tower 6 is connected to a second adsorbent collection device 9, which is connected to the second spray head 61 through a second circulation pipeline 63. The second adsorbent collection device 9 is also connected to the first circulation pipeline 55 through an acid delivery pipeline 64.

[0032] When using the nitrogen oxide pressurized absorption system of this embodiment to carry out the nitrogen oxide pressurized absorption process, the nitrogen oxide-containing gas is mixed with air or pure oxygen and then introduced into the gas compression device 1. As a preferred method, when the pressure of the reaction device 4 or the acid absorption tower 5 is lower than 0.8 MPa, a catalyst needs to be added.

[0033] The mixed gas after the oxidation reaction is fed into acid absorption tower 5. The acid pump is turned on, and dilute nitric acid with a mass fraction of 10%~30% is introduced into acid absorption tower 5. Acid absorption tower 5 is a first spray tower. The top of the first spray tower is equipped with a first spray head 51, and the middle of the spray tower is equipped with a porous tower plate. The porous tower plate is packed with packing. The packing on the porous tower plate is wetted by the first spray head 51, so that the countercurrent mixed gas can fully contact and react with the dilute nitric acid for absorption. As a preferred method, the liquid flow rate (L / min) and gas flow rate (m³ / min) are controlled throughout the absorption process. 3 The ratio of absorbent to nitric acid is 1:1 to 50:1, and the temperature of the absorbent is 0℃ to 60℃. For example, when controlling the temperature of the absorbent, 0℃ low-temperature water is used as the refrigerant. After absorption, the dilute nitric acid is collected through the pipeline below the acid absorption tower 5 and stored in the recovery tank 1.

[0034] The mixed gas after absorption by acid absorption tower 5 can be pressurized by gas compression device 1 and then fed into water absorption tower 6. Since the water absorption and acid absorption devices are connected, the pressure of the absorption tower and water absorption tower 6 should be consistent. The purpose of pressurization here is to ensure the initial gas flow rate of water absorption.

[0035] In this embodiment, the water absorption tower 6 and the acid absorption tower 5 have the same internal structure. The water pump is turned on, and liquid water is introduced into the water absorption tower 6. The packing material on the porous tower plate is wetted through the second spray head 61, allowing the counter-current mixed gas to fully contact and react with the water for absorption. Preferably, the liquid flow rate (L / min) and gas flow rate (m³ / min) are controlled throughout the absorption process. 3 The ratio of water to water absorption tower 6 is 1:1 to 50:1. The absorbed water is collected through the pipeline below the water absorption tower 6 and stored in the recovery tank 2.

[0036] After a period of time, when a low concentration of dilute nitric acid is introduced into the acid absorption tower 5 through the acid addition system, the acid pump is turned off, the supply of external acid source 10 is stopped, the circulation pump of acid absorption tower 5 is turned on, and the absorbed acid stored in recovery tank 1 is introduced into acid absorption tower 5. The packing on the porous tower plate is wetted through the first spray head 51, so that the nitrogen oxide mixture flowing upward in countercurrent comes into full contact with the absorbed acid and reacts. At this time, the acid in the system is circulated and absorbed, thereby increasing the acid concentration and obtaining a higher concentration of nitric acid by-product. During the circulation absorption process, the liquid flow rate remains the same as before. After a period of circulation absorption, when the nitric acid concentration is detected to be between 40% and 50%, the nitric acid collected in recovery tank 1 is collected, stored, or concentrated and purified into a product. Then the acid addition pump is turned on again to resume the supply of external acid source 10, and the above process is repeated.

[0037] Similarly, after the water supply system has been supplied by external water source 11 for a period of time, the external water source 11 is stopped, the circulation pump of water absorption tower 6 is turned on, and the dilute acid liquid that has been absorbed from water in recovery tank 2 and turned into dilute acid is passed into water absorption tower 6 to realize dilute acid circulation absorption. During this process, the liquid flow rate remains the same as before. After circulating for a period of time, a low concentration of dilute nitric acid can be obtained. When the concentration of nitric acid in recovery tank 2 is detected to be 10%~20%, the dilute nitric acid in recovery tank 2 is passed into acid absorption tower 5 as a supplement to the acid source 10 of acid absorption tower 5. Then the external water source 11 is supplied again, and the above process is repeated.

[0038] Example 1 (High pressure, no catalyst added) Air and nitrogen oxides are introduced, and after mixing, the oxygen content is about 20%. The initial nitrogen oxide concentration is detected to be 26,500 ppm. The mixed gas is pressurized to 1 MPa by an air compressor and then mixed and reacted in reaction device 4 (in this embodiment, because the pressure is greater than 0.8 MPa, no catalyst is added. In order to reduce the difference from adding a catalyst, an equal volume of non-catalytic powder is added in this embodiment). After the reaction, it is introduced into the subsequent pipeline.

[0039] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of acid absorption tower 5 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of water absorption tower 6 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed absorbent flows into recovery tank two.

[0040] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulating pump of the acid absorption tower 5. The absorbed acid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this point, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0041] After 10 minutes of water flow, turn off the water pump and turn on the circulation pump of water absorption tower 6. The absorbed liquid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeds 10%. The nitric acid stored at the bottom of water absorption tower 6 is then piped into acid absorption tower 5 as an external acid source 10. At this point, turn off the circulation pump of water absorption tower 6 and turn on the water pump. Repeat the above process until the experiment ends after 100 minutes.

[0042] After the mixed gas is absorbed by the water absorption tower 6, the concentration of nitrogen oxides in the mixed gas is detected to be between 3ppm and 190ppm, all below 200ppm, which meets the emission standards of the country (such as GB13271-2014, GB4915-2013, and GB26131-2010).

[0043] Example 2 (High Pressure with Catalyst) Air and nitrogen oxides were introduced, resulting in an oxygen content of approximately 20%. The initial nitrogen oxide concentration was measured at 26,500 ppm. The mixed gas was pressurized to 1 MPa by an air compressor and then reacted in reaction apparatus 4 (with catalyst added). The resulting mixture was then introduced into subsequent pipelines. It should be noted that the catalysts used in all embodiments and comparative examples are one of manganese-supported activated carbon catalysts, platinum-supported titanium dioxide catalysts, or cobalt-cerium bimetallic catalysts. Furthermore, to minimize variables, the same type of catalyst can be selected for each embodiment and comparative example.

[0044] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of acid absorption tower 5 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of water absorption tower 6 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed absorbent flows into recovery tank two.

[0045] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulating pump of the acid absorption tower 5. The absorbed acid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this point, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0046] After 10 minutes of water flow, the water pump was turned off, and the circulation pump of water absorption tower 6 was turned on. The absorbed liquid was then circulated back into the spray nozzles for further absorption, maintaining the same flow rate as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeded 10%. The nitric acid stored at the bottom of water absorption tower 6 was then piped into acid absorption tower 5 as an external acid source 10. At this point, the circulation pump of water absorption tower 6 was turned off, and the water pump was turned on again. This process was repeated until the experiment ended after 100 minutes. After the mixed gas was absorbed by water absorption tower 6, the nitrogen oxide concentration of the mixed gas was measured to be between 3 ppm and 130 ppm, all below 200 ppm, meeting the national emission standards.

[0047] Example 3 (Medium pressure with catalyst) Air and nitrogen oxides are introduced, and after mixing, the oxygen content is about 20%. The initial nitrogen oxide concentration is detected to be 26,500 ppm. The mixed gas is pressurized to 0.6 MPa by an air compressor and then mixed and reacted in reaction device 4 (with catalyst). The mixed gas after reaction is introduced into the subsequent pipeline.

[0048] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of acid absorption tower 5 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of water absorption tower 6 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed absorbent flows into recovery tank two.

[0049] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulating pump of the acid absorption tower 5. The absorbed acid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this point, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0050] After 10 minutes of water flow, turn off the water pump and turn on the circulation pump of water absorption tower 6. The absorbed liquid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeds 10%. The nitric acid stored at the bottom of water absorption tower 6 is then piped into acid absorption tower 5 as an external acid source 10. At this point, turn off the circulation pump of water absorption tower 6 and turn on the water pump. Repeat the above process until the experiment ends after 100 minutes.

[0051] After the mixed gas is absorbed by the water absorption tower 6, the concentration of nitrogen oxides in the mixed gas is detected to be between 3 ppm and 180 ppm, all of which are below 200 ppm and meet the national emission standards.

[0052] Comparative Example 1 (medium pressure, no catalyst added) Air and nitrogen oxides are introduced, and the oxygen content after mixing is about 20%. The initial nitrogen oxide concentration is detected to be 26,500 ppm. The mixed gas is pressurized to 0.7 MPa by an air compressor and then mixed and reacted in reaction device 4 (with an equal volume of non-catalytic powder added). The mixed gas after reaction is introduced into the subsequent pipeline.

[0053] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of acid absorption tower 5 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of water absorption tower 6 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed absorbent flows into recovery tank two.

[0054] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulation pump of acid absorption tower 5. The absorbed acid is then introduced back into the spray head for circulation absorption. At this time, the liquid flow rate remains the same as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this time, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0055] After 10 minutes of water flow, turn off the water pump and turn on the circulation pump of water absorption tower 6. The absorbed liquid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeds 10%. The nitric acid stored at the bottom of water absorption tower 6 is then piped into acid absorption tower 5 as a supplement to the external acid source 10. At this point, turn off the circulation pump of water absorption tower 6 and turn on the water pump. Repeat the above process until the experiment ends after 100 minutes.

[0056] After the mixed gas is absorbed by the water absorption tower 6, the concentration of nitrogen oxides in the mixed gas is detected to be between 1000ppm and 2900ppm, which does not meet the national emission standards.

[0057] Comparative Example 2 (at ambient pressure, no catalyst added) Air and nitrogen oxides are introduced, and after mixing, the oxygen content is about 20%. The initial nitrogen oxide concentration is measured to be 26,500 ppm. The mixed gas is introduced directly into the gas pipeline without pressure and then mixed and reacted in reaction device 4 (with an equal volume of non-catalytic powder added). The mixed gas after reaction is introduced into the subsequent pipeline.

[0058] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of acid absorption tower 5 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of water absorption tower 6 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed absorbent flows into recovery tank two.

[0059] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulating pump of the acid absorption tower 5. The absorbed acid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this point, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0060] After 10 minutes of water flow, turn off the water pump and turn on the circulation pump of water absorption tower 6. The absorbed liquid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeds 10%. The nitric acid stored at the bottom of water absorption tower 6 is then piped into acid absorption tower 5 as a supplement to the external acid source 10. At this point, turn off the circulation pump of water absorption tower 6 and turn on the water pump. Repeat the above process until the experiment ends after 100 minutes.

[0061] After the mixed gas is absorbed by the water absorption tower 6, the concentration of nitrogen oxides in the mixed gas is detected to be between 3000ppm and 5900ppm, which does not meet the national emission standards.

[0062] Comparative Example 3 (Catalyst added at atmospheric pressure) Air and nitrogen oxides are introduced, and after mixing, the oxygen content is about 20%. The initial nitrogen oxide concentration is measured to be 26,500 ppm. The mixed gas is introduced directly into the gas pipeline without pressurization and then mixed and reacted in reaction device 4 (with catalyst). The mixed gas after reaction is introduced into the subsequent pipeline.

[0063] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to 0.6 L / h. Maintain the reaction temperature of acid absorption tower 5 at 10°C. Use 0°C low-temperature water as the refrigerant during reaction temperature control. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to 0.6 L / h. Maintain the reaction temperature of water absorption tower 6 at 10°C. Use 0°C low-temperature water as the refrigerant during reaction temperature control. The absorbed absorbent flows into recovery tank two.

[0064] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulating pump of the acid absorption tower 5. The absorbed acid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this point, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0065] After 10 minutes of water flow, turn off the water pump and turn on the circulation pump of water absorption tower 6. The absorbed liquid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 10%. The nitric acid stored at the bottom of water absorption tower 6 is then piped into acid absorption tower 5 as a supplement to the external acid source 10. At this point, turn off the circulation pump of water absorption tower 6 and turn on the water pump. Repeat the above process until the experiment ends after 100 minutes.

[0066] After the mixed gas is absorbed by the water absorption tower 6, the concentration of nitrogen oxides in the mixed gas is detected to be between 2400ppm and 3900ppm, which does not meet the national emission standards.

[0067] Comparative Example 4 (Ambient Pressure Catalysis plus Medium Pressure Absorption) Air and nitrogen oxides are introduced, and the oxygen content after mixing is about 20%. The initial nitrogen oxide concentration is 26,500 ppm. The mixed gas is directly mixed and reacted in reaction device 4 (with catalyst) without pressurization. The mixed gas after reaction is pressurized to 0.7 MPa and then introduced into the subsequent pipeline.

[0068] Turn on the acid pump and introduce 30% dilute nitric acid. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of acid absorption tower 5 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed acid absorbent flows into recovery tank one. The absorbed mixed gas is introduced into water absorption tower 6. Turn on the water supply system pump and introduce water. Control the spray flow rate to make the liquid flow rate 0.6 L / h. Control the reaction temperature of water absorption tower 6 at 10℃. The refrigerant used for controlling the reaction temperature is 0℃ low-temperature water. The absorbed absorbent flows into recovery tank two.

[0069] After introducing 30% dilute nitric acid for 10 minutes, turn off the acid pump and turn on the circulating pump of the acid absorption tower 5. The absorbed acid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of absorption, the nitric acid concentration exceeds 40%. The more concentrated nitric acid is then introduced into the acid storage tank. At this point, the acid circulation system pump is turned off and the acid pump is turned on. The above process is repeated until the experiment ends after 100 minutes.

[0070] After 10 minutes of water flow, turn off the water pump and turn on the circulation pump of water absorption tower 6. The absorbed liquid is then circulated back into the spray head for absorption. The liquid flow rate remains the same as before. After 30 minutes of circulation absorption, the nitric acid concentration exceeds 10%. The nitric acid stored at the bottom of water absorption tower 6 is then piped into acid absorption tower 5 as a supplement to the external acid source 10. At this point, turn off the circulation pump of water absorption tower 6 and turn on the water pump. Repeat the above process until the experiment ends after 100 minutes.

[0071] After the mixed gas is absorbed by the water absorption tower 6, the concentration of nitrogen oxides in the mixed gas is detected to be between 380ppm and 450ppm, which does not meet the national emission standards.

[0072] The nitrogen oxide absorption rates and NO in the final exhaust gas corresponding to the above embodiments and comparative examples are as follows. x Average concentration / ppm is shown in Table 1 and Figure 2 .

[0073] Table 1 Please refer to Table 1, which lists the NO values ​​for each embodiment and comparative example. x Table 1 compares the oxidation rate with the average concentration of nitrogen oxides in the exhaust gas. It shows the differences in NO concentration under medium-pressure and high-pressure conditions with and without a catalyst. x The high oxidation rate and low nitrogen oxide concentration in the treated mixed gas demonstrate that this embodiment achieves efficient absorption of nitrogen oxides over a wide pressure range of 0.6 MPa to 1 MPa.

[0074] Figure 3To determine the corresponding exhaust gas concentrations under different pressures for catalyst-added and catalyst-free conditions, from... Figure 3 It can be seen that the exhaust gas concentration decreases significantly with increasing pressure. Under the same pressure, the exhaust gas concentration is even lower with the addition of a catalyst, indicating that increasing pressure and adding a catalyst are beneficial for reducing exhaust gas concentration. In particular, when the pressure is 0.6 MPa, the exhaust gas concentration with the addition of a catalyst is <200 ppm, which meets the emission standards, while the exhaust gas concentration without the addition of a catalyst is far >200 ppm, failing to meet the emission standards.

[0075] Figure 4 To determine the corresponding exhaust gas concentrations at different temperatures for products with and without catalyst, from... Figure 4 It can be seen that the exhaust gas concentration decreases significantly as the temperature decreases. At the same temperature, the exhaust gas concentration is even lower when a catalyst is added, indicating that the decrease in temperature and the addition of a catalyst are beneficial to reducing the exhaust gas concentration.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the pressurized absorption of nitrogen oxides, characterized in that, Includes the following steps: Nitrogen oxide gas is mixed with air or pure oxygen to form a mixed gas. The mixed gas is pressurized to 0.6 MPa to 1 MPa and then enters the reaction device for oxidation reaction. When the pressure of the pressurized mixed gas is lower than 0.8 MPa, a catalyst is required to be added to the reaction device to promote the oxidation reaction. The mixed gas after the oxidation reaction is absorbed by a dilute nitric acid absorption method to absorb nitrogen oxides in the mixed gas, and the mixed gas after the dilute nitric acid absorption method is further absorbed by a water absorption method to further absorb residual nitrogen oxides in the mixed gas, and the mixed gas after the absorption is NO x concentration < 200 ppm.

2. The pressurized absorption of nitrogen oxides process according to claim 1, characterized in that, When using dilute nitric acid to absorb nitrogen oxides in a mixed gas, the liquid flow rate is controlled throughout the absorption process: the gas flow rate is 1:1 to 50:1, and the temperature of the absorption liquid is 0℃ to 60℃.

3. The pressurized absorption of nitrogen oxides process according to claim 1, wherein, When using water absorption to absorb nitrogen oxides in a mixed gas, the liquid flow rate is controlled throughout the absorption process: the gas flow rate is 1:1 to 50:1, and the temperature of the absorption liquid is 0℃ to 60℃.

4. The nitrogen oxide pressure absorption process as described in claim 1, characterized in that, When nitrogen oxides in a mixed gas are absorbed using dilute nitric acid, the absorbent is collected or concentrated and purified into nitric acid product when the concentration of nitric acid in the absorbent is 40% to 50% after adsorption.

5. The system for the pressurized absorption process of nitrogen oxides as described in claim 1, characterized in that, include: A gas compression device, with its inlet end connected to a nitrogen oxide exhaust gas delivery pipeline and an air or oxygen delivery pipeline, is used to pressurize the mixture of nitrogen oxide exhaust gas and air or oxygen. The reaction apparatus is connected to the output pipeline of the gas compression device and is used to carry out an oxidation reaction of the mixed gas. An acid absorption tower is connected to the output pipeline of the reaction device. The top of the acid absorption tower is equipped with a first spray head, which is connected to a dilute nitric acid supply pipeline. The bottom is connected to a mixed gas input pipeline. The mixed gas and the dilute nitric acid absorption liquid are in countercurrent contact. The top of the acid absorption tower is equipped with a first gas output pipeline. The water absorption tower is connected at its bottom to the first gas output pipeline of the acid absorption tower. The top of the water absorption tower is equipped with a second spray head, which is connected to a water supply pipeline. The top of the water absorption tower is also equipped with a second gas output pipeline.

6. The system for the pressurized absorption process of nitrogen oxides as described in claim 5, characterized in that, The bottom of the acid absorption tower is provided with a first adsorption liquid collection device, which is connected to the first spray head through a first circulation pipeline.

7. The system for the pressurized absorption process of nitrogen oxides as described in claim 5, characterized in that, The bottom of the water absorption tower is connected to a second adsorbent collection device, which is connected to the second spray head through a second circulation pipeline. The second adsorbent collection device is also connected to the first circulation pipeline through an acid delivery pipeline.

Images