A nitrogen oxide waste gas treatment device

Abstract

The invention discloses a nitrogen oxide waste gas treatment device, comprising a pickling tank, a circulation pump, a venturi gas-liquid reactor and an oxygen tank, wherein the circulation pump comprises a pump inlet and a pump outlet, the pump inlet is connected to the pickling tank, the pump outlet is connected to the reactor inlet, the pickling tank comprises a pickling chamber and a waste gas chamber, the waste gas chamber is located in the upper space of the pickling tank, the venturi gas-liquid reactor comprises a reactor injection port and a reactor low-pressure air inlet, the reactor low-pressure air inlet is connected with a reactor air inlet pipeline, the reactor injection port is connected with an acid liquid circulation pipe connected to the pickling tank, the waste gas circulation pipe is connected to the waste gas chamber, an oxygen pipeline is connected between the oxygen tank and a two-way pipe, the waste gas chamber at the upper part of the pickling tank is in a slightly negative pressure state, the problem of nitrogen oxide waste gas treatment is solved, and HNO3 is generated for resource utilization, the design is simple and efficient, the investment in waste gas resource utilization equipment is small, the operating cost is low, energy conservation and emission reduction are achieved, and no waste gas and wastewater are generated in the resource utilization process.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen oxide waste gas treatment, and in particular to a nitrogen oxide waste gas treatment device. Background Art

[0002] Nitrogen oxides cause pollution to the atmosphere, among which NOx (N2O, NO, NO2, N2O3, N2O4 and N2O5) is one of the main air pollutants. It reacts with O2 and H2O in the air to produce acid rain, and produces photochemical smog under photochemical reaction conditions, affecting visibility. NOx is an important factor in the formation of acid rain and the destruction of the atmospheric ozone layer. When the concentration of NOx is too high, it has a strong irritating effect on the respiratory system of humans or animals; the main components of NOx in industrial waste gas are NO and NO2. NO2 is an irritating and highly toxic brown-yellow gas that is seriously harmful to human health, plant growth, and material corrosion.

[0003] Common nitric acid production and use fields, such as the metal surface treatment industry, require a large amount of nitric acid, especially the stainless steel pickling process mostly uses nitric acid and hydrofluoric acid mixed acid pickling. The conventional closed pickling process solves the problem of waste gas leakage from the pickling tank, but does not solve the problem of waste gas emission compliance or resource utilization. Due to the lack of oxygen in the closed system, NO will not be oxidized, and NO is insoluble in water, colorless, and has poor absorption effect in alkaline washing. There is also a method of adding hydrogen peroxide to the spray water to oxidize NO into NO2 to achieve the purpose of denitrification, but the effect is not good and the cost is high. The chemical equation for waste gas treatment is as follows:

[0004] 2NO+O2== 2NO2 or NO+H2O2==NO2+H2O

[0005] 3NO2+H2O== 2HNO3+NO

[0006] Or 3NO2+2NaOH== 2NaNO3+NO+H2O

[0007] When NO2 is absorbed by water to generate nitric acid, a disproportionation reaction occurs, with two-thirds of NO2 generating nitric acid or sodium nitrate and one-third of NO2 generating NO. This makes it difficult to achieve NOx emission standards through simple water washing or alkaline washing of the exhaust gas. At the same time, due to the consumption of oxygen in the confined space, the oxygen partial pressure is reduced, which slows down the oxidation reaction and reduces the NOx removal efficiency. Summary of the invention

[0008] The purpose of the present invention is to provide a method and a treatment device for resource utilization of nitrogen oxide waste gas, which can not only effectively treat nitrogen oxide waste gas to achieve ultra-low emissions, but also convert NOx into nitric acid, turning waste into treasure and realizing resource recycling.

[0009] The above technical objectives of the present invention are achieved through the following technical solutions:

[0010] A nitrogen oxide waste gas treatment device comprises a pickling tank, a circulation pump, a venturi gas-liquid reactor and an oxygen tank, wherein the circulation pump comprises a liquid inlet and a pump liquid outlet, wherein the pump liquid inlet is connected to the pickling tank, wherein the pump liquid outlet is connected to the reactor liquid inlet, wherein the pickling tank comprises a pickling chamber and a waste gas chamber, wherein the waste gas chamber is located in the upper space of the pickling tank, wherein the venturi gas-liquid reactor comprises a reactor liquid inlet, a reactor injection port and a reactor low-pressure air inlet, wherein the reactor low-pressure air inlet is connected to a reactor air inlet pipeline, wherein the reactor air inlet pipeline is connected to a tee pipe 1, wherein the tee pipe 1 is connected to a tee pipe 2, wherein the third end of the tee pipe 1 is connected to an exhaust gas circulation pipe, wherein the reactor injection port is connected to an acid liquid circulation pipe connected to the pickling tank, wherein the exhaust gas circulation pipe is connected to the exhaust gas chamber, and an oxygen pipeline is connected between the oxygen tank and the tee pipe 2. The oxygen tank is equipped with a pressure reducing valve and a flow control valve.

[0011] By adopting the above technical scheme, the metal in the pickling tank reacts with the acid solution to carry out pickling, and NOx waste gas is generated and enters the waste gas chamber. The circulating pump, the Venturi gas-liquid reactor and the pickling tank form an acid solution circulation, and the waste gas and oxygen are circulated and sucked into the Venturi reactor, and mixed in the pickling tank to generate nitric acid and NO. In the upper space of the pickling tank, NO reacts with excess O2 and is sucked into the Venturi reactor at the same time, and the cycle is repeated. By adopting this method, NO is completely oxidized and absorbed into nitric acid, thereby realizing the treatment and resource utilization of NOx waste gas.

[0012] Preferably, the third end of the three-way pipe is connected to an exhaust gas treatment system.

[0013] By adopting the above technical scheme, the low-pressure air inlet of the reactor is used to control the direction of gas movement, the exhaust gas circulation pipe is used to transport the gas, and the exhaust gas treatment system is used to treat the exhaust gas when the cover is opened to discharge the material and when the material is finally taken out after the pickling is completed.

[0014] Preferably, an exhaust gas pipeline valve is fixedly connected between the three-way pipe 2 and the exhaust gas treatment system, and a pressure reducing valve and a switch valve are installed between the three-way pipe 2 and the oxygen tank, and the pressure reducing valve is closer to the oxygen tank than the switch valve.

[0015] With the above technical solution, the exhaust gas pipeline valve is used to control whether the gas enters the exhaust gas treatment system, the switch valve controls whether the oxygen enters the Venturi gas-liquid reactor, and the pressure reducing valve is used to control the pressure in front of the oxygen tank to prevent excessive pressure.

[0016] Preferably, the exhaust gas pipeline valve is opened only when the pickling tank is fed into or discharged from the pickling tank.

[0017] The above technical solution is adopted to prevent waste gas from entering the waste gas treatment system during the pickling process, thereby wasting resources.

[0018] Preferably, a pressure sensor and a low-pressure valve are provided in the exhaust chamber.

[0019] By adopting the above technical solution, the exhaust chamber is in a slightly negative pressure state during the pickling process, the pressure sensor monitors the pressure in the exhaust chamber in real time to prevent the pressure in the exhaust chamber from being too high, and the low-pressure valve is used to control the pressure in the exhaust chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A perspective view of an embodiment of the invention.

[0021] Figure numerals: 1, pickling tank; 2, circulating pump; 3, venturi gas-liquid reactor; 4, oxygen tank; 5, pump liquid inlet; 6, pump liquid outlet; 7, pickling chamber; 8, waste gas chamber; 9, reactor injection port; 10, reactor low-pressure air inlet; 11, tee pipe one; 12, acid liquid circulation pipe; 13, waste gas circulation pipe; 14, waste gas treatment system; 15, waste gas pipeline valve; 16, pressure reducing valve; 17, flow control valve; 18, pressure sensor; 19 oxygen pipeline; 20, low-pressure valve; 21, tee pipe two; 22, reactor air inlet pipeline; 23, reactor liquid inlet. DETAILED DESCRIPTION

[0022] The following is only a preferred embodiment of the present invention, and the protection scope is not limited to this embodiment. All technical solutions under the concept of the present invention should belong to the protection scope of the present invention. At the same time, it should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

[0023] As shown in the figure, a nitrogen oxide waste gas treatment device includes a pickling tank 1, a circulating pump 2, a venturi gas-liquid reactor 3 and an oxygen tank 4. The circulating pump 2 includes a pump inlet 5 and a pump outlet 6. The pump inlet 5 is connected to the pickling tank 1, and the pump outlet 6 is connected to the reactor inlet 23 of the venturi gas-liquid reactor 3. The pickling tank 1 includes a pickling chamber 7 and a waste gas chamber 8. The waste gas chamber 8 is located in the upper space of the pickling tank 1. In order to facilitate opening the cover and taking out the workpiece, the opening of the waste gas circulation pipe is fixed on the side of the waste gas chamber. The pressure sensor is fixedly installed in the waste gas chamber away from the far end of the waste gas outlet and installed on the side of the waste gas chamber. The closed sealing cover of the pickling tank is independent and is not connected to other equipment or instruments. The venturi gas-liquid reactor 3 includes a reactor liquid inlet 23, a reactor injection port 9 and a reactor low-pressure air inlet 10. The reactor low-pressure air inlet 10 is connected to a reactor air inlet pipe 22. The reactor air inlet pipe 22 is connected to a three-way pipe 11, which is respectively connected to an exhaust gas circulation pipe 13. The three-way pipe 21 is connected to an oxygen pipe 19 and an exhaust gas treatment system 14. During the exhaust gas circulation inhalation treatment process, the exhaust gas treatment system is closed through the exhaust gas pipe valve 15, and the exhaust gas does not enter the exhaust gas treatment system. At this time, the exhaust gas treatment system is in a temporary state. In the stopped state, the waste gas is circulated and sucked into the Venturi gas-liquid reactor, NOx is converted into NO2 many times, and is absorbed by the water in the acid solution and converted into nitric acid. The acid solution circulation pipe 12 connected to the reactor injection port 9 is connected to the pickling tank 1 and is below the pickling liquid level. The waste gas chamber 8 is connected to the waste gas circulation pipe 13, and the other end of the waste gas circulation pipe 13 is connected to the three-way pipe 11 and the two-way pipe 21. The reactor air intake pipe 22 is connected to the three-way pipe 11, the oxygen tank 4 is connected to the two-way pipe 21, and the waste gas main pipe 13 forms a waste gas circulation absorption system. The metal in the pickling tank 1 reacts with the acid solution for pickling, and the NOx waste gas generated enters the waste gas chamber 8. The pickling chamber 7, the circulating pump 2, the Venturi gas-liquid reactor 3 and the pickling tank 1 form an acid liquid circulation system; the waste gas in the waste gas chamber 8, the oxygen in the oxygen tank 4, the circulating pump 2, the Venturi gas-liquid reactor 3 and the pickling tank 1 form a waste gas circulation absorption system, and are mixed in the pickling tank 1 to generate nitric acid and NO. In the waste gas chamber 8 in the upper space of the pickling tank 1, NO reacts with excess O2 to generate NO2, which is sucked into the Venturi reactor at the same time, and the cycle is repeated. In this way, NO is completely oxidized and absorbed into nitric acid, and the NOx concentration is continuously reduced. Through the signal flow monitoring of the oxygen flow control valve 17, the NOx content in the waste gas chamber 8 can be inferred, and the NOx waste gas is controlled and recycled. At the same time, the impact load of NOx on the waste gas treatment system 14 is reduced. When the workpiece is taken out and the cover is opened, the waste gas pipeline valve 15 is opened, and the waste gas treatment system 14 is started, which not only reduces the waste gas treatment agent, but also makes it easy for the treated waste gas to meet the emission standards, greatly saving the waste gas treatment cost.

[0024] An exhaust gas pipeline valve 15 is fixedly connected between the exhaust gas circulation pipe 13 and the exhaust gas treatment system 14. The exhaust gas circulation pipe 13 is connected to the low-pressure air inlet 10 of the reactor through a three-way pipe 11 and a pipe 22. The oxygen tank 4 is connected through a three-way pipe 21. A flow control valve 17 and a pressure reducing valve 16 are installed in between. The pressure reducing valve 16 is closer to the oxygen tank 4 than the flow control valve 17. The exhaust gas pipeline valve 15 is opened only when the pickling tank 1 is fed or discharged. The exhaust gas pipeline valve 15 is used to control whether the exhaust gas enters the exhaust gas treatment system 14. The flow control valve 17 controls whether the oxygen enters the Venturi gas-liquid reactor 3. The pressure reducing valve 16 is used to adjust the pressure of the oxygen tank 4 when entering the exhaust gas circulation pipe 13 to prevent the exhaust gas from escaping due to excessive pressure or causing the oxygen content in the exhaust chamber 8 to be too low. A pressure sensor 18 and a low-pressure valve 20 are provided on the side of the exhaust chamber 8. The pressure sensor 18 monitors the micro-negative pressure condition in the exhaust chamber 8 in real time to prevent the pressure in the exhaust chamber 8 from being too high, causing exhaust gas to escape and pollute the environment. The low-pressure valve is used to create a micro-negative pressure environment in the exhaust chamber.

[0025] The NOx waste gas generated during the production process is controlled in a limited closed space, NO is oxidized to NO2 by supplementing oxygen, and nitric acid is recovered by multiple absorption using circulating water or dilute acid. The method can be used in fields where nitric acid is used, not limited to the metal surface treatment industry. The method can also be used for the recycling absorption treatment of hydrochloric acid or sulfuric acid pickling waste gas without the need to access oxygen. A method and treatment device for resource utilization of nitrogen oxide waste gas of the present invention, taking stainless steel pickling as an example, the pickling liquid is a mixed acid of nitric acid and hydrofluoric acid. During the pickling process, after removing the surface oxide layer, nitric acid reacts with metallic iron to generate ferrous nitrate and NOx waste gas, the main component of which is NO, and the chemical formula is as follows: 3Fe+8HNO3==3Fe(NO3)2+2NO+4H2O. In a closed system, NO is not easily oxidized to NO2 in an oxygen-deficient state, and it is difficult to clean NOx by water washing or alkali washing. Often, yellow smoke is seen as soon as the waste gas leaves the exhaust pipe, which is the color of NO2 oxidized by air.

[0026] The pickling tank 1 is a closed pickling equipment, and there is a smaller waste gas storage space on the top of the tank. The pump inlet 5 is connected to the bottom of the pickling tank 1, the pump outlet 6 is connected to the reactor inlet 23, and the pump outlet 6 of the venturi gas-water reactor is connected to the pickling tank 1 through an acid circulation pipe 12 to form an acid circulation. The outlet of the acid circulation pipe 12 is below the liquid level of the pickling liquid. The low-pressure suction port 10 of the venturi gas-water reactor is connected to the waste gas chamber 8 in the upper space of the pickling tank 1. At the same time, oxygen is connected to the waste gas pipeline. The waste gas and oxygen are circulated and sucked into the venturi reactor together, and mixed in the pickling tank 1 to generate nitric acid and NO. The unabsorbed NO and the unreacted O2 are returned to the waste gas chamber 8 in the upper space of the pickling tank 1, and NO reacts with excess O2 and is sucked into the venturi reactor at the same time. The cycle is repeated. This method is used to completely oxidize and absorb NO into nitric acid, thereby realizing the treatment and resource utilization of NOx waste gas.

[0027] Select a gas-water reactor with a large venturi gas-liquid ratio, and the power of the circulating pump 2 should match the amount of waste gas to be inhaled. Using the above technical solution, the reaction oxidant can be oxygen or hydrogen peroxide, and its chemical equation is as follows:

[0028] When the reaction oxidant is oxygen, 2NO+O2====2NO2;

[0029] When the oxidant is hydrogen peroxide, NO + H2O2 ==== NO2 + H2O

[0030] The absorption process is: 3NO2+H20====2HNO3+NO

[0031] The overall reaction equation is: 4NO + 3O2 + 2H20 ==== 4HNO3

[0032] During the reaction, the volume shrinks. As long as the amount of oxygen is not excessive, the system can maintain a slight negative pressure. Appropriate excess oxygen is conducive to the chemical reaction to the right.

[0033] When H2O2 is used to oxidize NO, the ferrous ions in the acid solution are easily oxidized at the same time and a large amount of heat is released. The amount of H2O2 used is large and the processing cost is high. When O2 is used to oxidize NO, the process is more reasonable and the processing cost is low. Therefore, the present invention prefers O2 as an oxidant. On the side of the waste gas chamber 8 at the upper part of the pickling tank 1, one or more outlets can be opened at intervals, and a distributed air distribution branch pipe is used, which is connected through the main pipeline to facilitate the rapid and uniform suction of the waste gas into the Venturi reactor.

[0034] Working principle of the invention: metal is pickled in the pickling tank 1 to generate NOx waste gas which enters the waste gas chamber 8, the circulating pump 2 extracts the acid from the pickling tank 1 through the pump inlet 5 and enters the venturi gas-liquid reactor 3 through the pump outlet 6, and then the acid circulation pipe 12 transports the acid from the venturi gas-liquid reactor 3 through the reactor injection port 9 to the pickling chamber 7 to form an acid circulation. The waste gas circulation pipe 13, the waste gas chamber 8, the reactor air inlet pipe 22, the reactor low-pressure air inlet 10, the tee pipe 1 11, the tee pipe 2 21, the venturi gas-liquid reactor 3 and the circulating pump 2 form a waste gas circulation. Oxygen is discharged from the oxygen tank 4 through the oxygen pipe 19, and the exhaust gas and oxygen are circulated and sucked into the Venturi gas-liquid reactor 3, and mixed in the pickling tank 1 to generate nitric acid and NO. In the upper space of the pickling tank 1, the unabsorbed NO reacts with the excess O2 to generate NO2, which is sucked into the Venturi reactor again. The cycle is repeated, and the NOx concentration in the exhaust chamber becomes lower and lower, which is beneficial to reducing the load of the exhaust gas treatment system. Alkaline solution washing can achieve standard emissions.

Claims

1. A nitrogen oxide waste gas treatment device, comprising a pickling tank (1), a circulation pump (2), a venturi gas-liquid reactor (3) and an oxygen tank (4), characterized in that: The circulating pump (2) comprises a pump liquid inlet (5) and a pump liquid outlet (6), wherein the pump liquid inlet (5) is connected to the pickling tank (1), the venturi gas-liquid reactor (3) comprises a reactor liquid inlet (23), a reactor injection port (9) and a reactor low-pressure air inlet (10), wherein the pump liquid outlet (6) is connected to the reactor liquid inlet (23), the pickling tank (1) comprises a pickling chamber (7) and a waste gas chamber (8), wherein the waste gas chamber (8) is located in the upper space of the pickling tank (1), and the reactor low-pressure air inlet (10) is connected to the reactor low-pressure air inlet (11). 0) is connected to a reactor air inlet pipeline (22), the reactor air inlet pipeline (22) is connected to a tee pipe one (11), the tee pipe one (11) is connected to a tee pipe two (21), the third end of the tee pipe one (11) is connected to an exhaust gas circulation pipe (13), the reactor injection port (9) is connected to an acid liquid circulation pipe (12) and is connected to the pickling tank (1), the exhaust gas circulation pipe (13) is connected to an exhaust gas chamber (8), and an oxygen pipeline (19) is connected between the oxygen tank (4) and the tee pipe two (21).

2. A nitrogen oxide waste gas treatment device according to claim 1, characterized in that: The third end of the three-way pipe 2 (21) is connected to the exhaust gas treatment system (14).

3. A nitrogen oxide waste gas treatment device according to claim 2, characterized in that: An exhaust gas pipeline valve (15) is fixedly connected between the three-way pipe (21) and the exhaust gas treatment system (14), and a pressure reducing valve (16) and a switch valve (17) are installed between the three-way pipe (21) and the oxygen tank (4), wherein the pressure reducing valve (16) is closer to the oxygen tank (4) than the switch valve (17).

4. A nitrogen oxide waste gas treatment device according to claim 3, characterized in that: The exhaust gas pipeline valve (15) is opened only when the pickling tank (1) is filled with or discharged with materials.

5. The nitrogen oxide waste gas treatment device according to claim 4, characterized in that: A pressure sensor (18) and a low-pressure valve (20) are provided in the exhaust gas chamber (8).

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