A hydrogen peroxide ultrasonic atomization oxidation system and method for NO in flue gas

Abstract

This invention discloses a hydrogen peroxide ultrasonic atomization oxidation system and method for NO in flue gas. The system includes a hydrogen peroxide ultrasonic atomizer, a hydrogen peroxide pH adjustment system, and a spray grille installed in the flue. The hydrogen peroxide ultrasonic atomizer has an atomization outlet at the top, a hydrogen peroxide inlet pipe on the top side wall, and a compressed air pipe on the bottom side wall. The hydrogen peroxide pH adjustment system includes a mixing tank, an alkali storage tank, and a hydrogen peroxide storage tank. A pH meter is installed in the mixing tank, with its inlet connected to both the alkali storage tank and the hydrogen peroxide storage tank, and its outlet connected to the hydrogen peroxide inlet pipe. The inlet of the spray grille is connected to the atomization outlet. This invention adjusts the pH value of the hydrogen peroxide during delivery, promoting more efficient and targeted decomposition of hydroxyl radicals at high temperatures, thus improving hydrogen peroxide utilization. The smaller droplet size of the ultrasonically atomized hydrogen peroxide increases the gas-liquid contact area, shortens the heating process, and allows the hydrogen peroxide droplets to be rapidly heated and decomposed by the high-temperature flue gas, solving the problems of low efficiency and severe ineffective decomposition of NO in flue gas by hydrogen peroxide oxidation.

Description

Technical Field

[0001] This invention belongs to the field of air pollutant purification and is applicable to the oxidation of NO in flue gas from coal combustion, coking, steel, biomass and other fields. It relates to a hydrogen peroxide ultrasonic atomization oxidation system and method for NO in flue gas. Background Technology

[0002] Flue gas denitrification technologies mainly include selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR) technologies. Among them, SCR denitrification technology is the most widely used, with denitrification temperatures between 320℃ and 400℃. However, it suffers from problems such as system complexity, large catalyst consumption, and susceptibility to poisoning, making it difficult to apply SCR denitrification technology under conditions of limited temperature window and complex flue gas composition. Meanwhile, SNCR denitrification efficiency is only 30% to 40%, which is insufficient to meet emission standards.

[0003] Currently, denitrification technology is the main challenge in flue gas pollutant treatment, especially low-temperature denitrification technology, which is a key factor restricting compliance with emission standards. For denitrification of small and medium-sized boilers, the most common method is oxidation denitrification, which uses O3 as an oxidant. Typically, the molar ratio of O3 / NO is greater than 2, oxidizing NO in the flue gas into N2O5, which is then absorbed by a subsequent wet system. This technology is simple, has low investment costs, high pollutant removal efficiency, and flexible adjustment. However, the cost of O3 generation is high, the O3 injection volume is relatively large, and there is a certain amount of O3 escape problem, resulting in high operating costs and easy secondary pollution.

[0004] Pre-treatment primary oxidation combined with desulfurization and denitrification technology is an integrated pollutant removal technology that has emerged in recent years. This technology uses pre-treatment oxidant O3 or NaClO / NaClO2 solution to oxidize NO in flue gas to NO2, which is then absorbed by subsequent wet or semi-dry processes. However, the production cost of O3 is relatively high (approximately 10,500 yuan / ton), resulting in high investment and operating costs for this technology. Furthermore, NaClO / NaClO2 solution suffers from low oxidation efficiency, poor selectivity, and severe pipeline corrosion.

[0005] Hydrogen peroxide oxidation denitrification technology has always been a research hotspot. H2O2 is a green oxidant with a unit cost that is only one-tenth that of O3. However, when hydrogen peroxide is atomized and oxidized through a gas-liquid two-phase flow nozzle, the oxidation efficiency of NO can only reach 50%, and the self-decomposition phenomenon is serious, resulting in low utilization rate and severely restricting its application. For example, Chinese patent document CN106853328A discloses a method and apparatus for efficient utilization of hydrogen peroxide in low-temperature flue gas desulfurization and denitrification. This method involves heating hydrogen peroxide to a gaseous state, which is then carried into the flue gas duct by a hot carrier gas, achieving a gas-gas mixing reaction. The selected mixing temperature is 80℃~150℃. However, this method easily causes ineffective decomposition of hydrogen peroxide during the heating and gasification process, and the low mixing temperature with the flue gas makes it difficult for hydrogen peroxide to decompose in large quantities to generate hydroxyl radicals, resulting in low NO oxidation efficiency. Chinese patent document CN102500206A discloses a system and method for simultaneous desulfurization and denitrification of flue gas based on the action of hydrogen peroxide. In this method, hydrogen peroxide is gasified by an ultrasonic gasification device and enters the gas distribution device directly without being carried by compressed air. The flow rate of hydrogen peroxide is slow when passing through the pipeline in the flue gas duct, and the temperature of the hydrogen peroxide gas increases before contacting NO. The self-decomposition of hydrogen peroxide is severe, resulting in low efficiency in oxidizing NO. Chinese patent document CN111420544A discloses a low-temperature hydrogen peroxide denitrification device and process. This method utilizes ultrasonic waves to excite the hydrogen peroxide solution, forming ·OH radicals in the solution. The solution is then atomized through an atomizing nozzle to react with the flue gas. Essentially, this is a gas-liquid contact reaction, where the ·OH free radicals in the droplets have a low probability of contacting NO in the flue gas, resulting in insufficient mixing and low removal efficiency. Chinese patent document CN202010872814X discloses a combined pre-oxidation and wet catalytic desulfurization and denitrification system and method. In this method, the hydrogen peroxide solution directly enters the ultrasonic atomizer for atomization, leading to a continuous increase in temperature. This results in significant ineffective self-decomposition of the hydrogen peroxide, causing substantial waste. Furthermore, the acidic hydrogen peroxide droplets have low efficiency in the directional decomposition of strong oxidizing free radicals at high temperatures, and also cause severe corrosion to the ultrasonic atomizer and high-temperature spray components. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a hydrogen peroxide ultrasonic atomization oxidation system and method for NO in flue gas, solving the problems of low efficiency and serious ineffective decomposition of NO in hydrogen peroxide oxidation flue gas.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A hydrogen peroxide ultrasonic atomization oxidation system for NO in flue gas includes a hydrogen peroxide ultrasonic atomizer, a hydrogen peroxide pH adjustment system, and a spray grille installed in the flue.

[0009] The hydrogen peroxide ultrasonic atomizer is provided with an atomization outlet at the top, a hydrogen peroxide inlet pipe on the top side wall, and a compressed air pipe on the bottom side wall.

[0010] The hydrogen peroxide pH adjustment system includes a mixing tank, an alkali storage tank, and a hydrogen peroxide storage tank; the mixing tank is equipped with a pH meter, whose inlet is connected to both the alkali storage tank and the hydrogen peroxide storage tank, and whose outlet is connected to the hydrogen peroxide inlet pipe.

[0011] The inlet of the spray grille is connected to the atomization outlet.

[0012] Furthermore, the hydrogen peroxide ultrasonic atomizer is tank-shaped, with multiple layers of hydrogen peroxide atomizing pools arranged sequentially from bottom to top inside; each hydrogen peroxide atomizing pool above the bottom layer has a coaxial opening in the center, and a gas channel baffle is provided at each opening; each hydrogen peroxide atomizing pool above the bottom layer has a bypass channel; each hydrogen peroxide atomizing pool has an ultrasonic atomizing plate, and the bottom hydrogen peroxide atomizing pool also has a level gauge; the compressed air pipe is located above the bottom hydrogen peroxide atomizing pool, and its outlet is coaxial with the opening and vertically upward.

[0013] Furthermore, the height from the bypass channel entrance to the bottom of the hydrogen peroxide atomization pool on the same level is 2cm to 4cm.

[0014] Furthermore, the height of the gas channel partition is at least 3 cm greater than the height of the bottom of the hydrogen peroxide atomizing pool on the same level.

[0015] Furthermore, the ultrasonic atomizing plate uses a ceramic glaze atomizing sheet, and the outer shells of the ultrasonic atomizing plates set in the same layer of hydrogen peroxide atomizing pool are interconnected by wires; the ultrasonic atomizing plates in each layer of hydrogen peroxide atomizing pool have separate start and stop control circuits.

[0016] Furthermore, an alkali metering pump is installed on the connecting pipeline between the mixing tank and the alkali storage tank; and a hydrogen peroxide delivery pump is installed on the connecting pipeline between the mixing tank and the hydrogen peroxide storage tank.

[0017] Furthermore, the spray grille is arranged in the flue gas temperature range of 200℃ to 500℃.

[0018] A method for oxidizing NO in flue gas using ultrasonic atomization of hydrogen peroxide includes:

[0019] After adjusting the pH value of the hydrogen peroxide solution to an alkaline solution, ultrasonic atomization is performed. The atomized hydrogen peroxide droplets are carried by compressed air and injected into the flue gas with a temperature of 200℃~500℃. At high temperature, the hydrogen peroxide decomposes to produce oxidizing free radicals, which oxidize NO in the flue gas to NO2.

[0020] Furthermore, the molar ratio of hydrogen peroxide to NO in the flue gas is 1 to 2.

[0021] Furthermore, the pH value of the mixed solution after adding alkali solution to the hydrogen peroxide solution is 5-8.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention's system, by incorporating a hydrogen peroxide pH adjustment system, can adjust the pH of the hydrogen peroxide solution to be more alkaline before ultrasonic vaporization, effectively avoiding the problem of insufficient targeted decomposition of strong oxidizing free radicals due to unadjusted pH. Simultaneously, the pH-adjusted hydrogen peroxide solution, after ultrasonic atomization by the hydrogen peroxide ultrasonic atomizer, produces droplets with a size of 1µm to 5µm, smaller than the 20µm to 50µm droplets from compressed air atomization. This makes it easier for the droplets to rapidly decompose into hydroxyl groups in high-temperature flue gas, resulting in higher NO oxidation efficiency. Furthermore, the compressed air, flowing upwards through a compressed air pipe located at the bottom of the hydrogen peroxide ultrasonic atomizer, carries the atomized hydrogen peroxide droplets into the spray grille for ejection, effectively improving the efficiency of NO oxidation to NO2 in the flue gas.

[0024] Furthermore, the system of the present invention employs a layered arrangement of hydrogen peroxide liquid surface in the hydrogen peroxide ultrasonic atomizer. The overflow of hydrogen peroxide between each layer of hydrogen peroxide atomization pool ensures a constant liquid level. The amount of hydrogen peroxide atomized is approximately equal to the amount entering the hydrogen peroxide ultrasonic atomizer, and the hydrogen peroxide is in a continuous flow state. This prevents the hydrogen peroxide solution from decomposing due to the temperature rise caused by ultrasonic action, while also improving the ultrasonic atomization effect and increasing the atomization efficiency.

[0025] Furthermore, the system of the present invention sets the height range from the bypass channel inlet to the bottom of the hydrogen peroxide atomization pool on the same layer to 2cm to 4cm, so that the hydrogen peroxide liquid level can be maintained at the optimal height, ensuring that the atomized particle size of hydrogen peroxide is 1um to 5um, and exerting the best effect and atomization efficiency of ultrasonic atomization.

[0026] Furthermore, the system of the present invention sets the height of the gas channel partition to be at least 3 cm greater than the height range from the inlet of the bypass channel to the bottom of the hydrogen peroxide atomization pool on the same layer, in order to prevent the hydrogen peroxide solution from overflowing from the gas channel.

[0027] Furthermore, the system of the present invention prevents the ultrasonic atomizing plate from being corroded during the ultrasonic atomization process of hydrogen peroxide by using an atomizing sheet with a ceramic glaze.

[0028] Furthermore, the system of the present invention adopts a method of interconnecting the outer shells of ultrasonic atomizing plates in the same hydrogen peroxide atomizing pool through wires, which effectively prevents electrolytic corrosion.

[0029] Furthermore, the system of the present invention effectively ensures oxidation efficiency by arranging the injection grilles within the range of flue gas temperature of 200℃ to 500℃.

[0030] The method of this invention adjusts the pH value of hydrogen peroxide during the delivery process, which promotes the more directional decomposition of hydroxyl radicals by hydrogen peroxide at high temperature, significantly improving the utilization rate of hydrogen peroxide. The hydrogen peroxide droplets after ultrasonic atomization have a smaller particle size and are simultaneously carried into the flue by compressed air, which significantly increases the gas-liquid contact area and shortens the heating process. This allows the hydrogen peroxide droplets to be rapidly heated and decomposed by the high-temperature flue gas, generating strong oxidizing hydroxyl radicals, which can efficiently oxidize NO in the flue gas into NO2. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the system process structure in an example of the present invention.

[0032] Figure 2 This is a schematic diagram of the structure of the hydrogen peroxide ultrasonic atomizer in an example of the present invention.

[0033] Figure 3 This is a schematic diagram illustrating the characteristics of H2O2 compression atomization oxidation of NO.

[0034] Figure 4 This is a schematic diagram of the characteristics of H2O2 ultrasonic atomization oxidation of NO.

[0035] Among them, 1 is an alkali storage tank, 2 is a hydrogen peroxide storage tank, 3 is an alkali metering pump, 4 is a hydrogen peroxide delivery pump, 5 is a pH meter, 6 is a mixing tank, 7 is a hydrogen peroxide ultrasonic atomizer, 8 is a spray grille, 9 is a flue, 10 is a hydrogen peroxide inlet pipe, 11 is a bypass channel, 12 is an ultrasonic atomizing plate, 13 is an atomization outlet, 14 is a gas channel baffle, 15 is a hydrogen peroxide atomization pool, 16 is a level gauge, and 17 is a compressed air pipe. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0037] Example 1:

[0038] This invention discloses a hydrogen peroxide ultrasonic atomization oxidation system for NO in flue gas, such as... Figure 1As shown, the system includes an alkali storage tank 1, a hydrogen peroxide storage tank 2, an alkali metering pump 3, a hydrogen peroxide delivery pump 4, a pH meter 5, a mixing tank 6, a hydrogen peroxide ultrasonic atomizer 7, a spray grille 8, and a flue 9. The outlet of the alkali storage tank 1 is connected to the inlet of the alkali metering pump 3, and the outlet of the alkali metering pump 3 is connected to the mixing tank 6. The pH meter 5 is installed on the mixing tank 6. The outlet of the hydrogen peroxide storage tank 2 is connected to the inlet of the hydrogen peroxide delivery pump 4, and the outlet of the hydrogen peroxide delivery pump 4 is connected to the mixing tank 6. The outlet of the mixing tank 6 is connected to the inlet of the hydrogen peroxide ultrasonic atomizer 7, and the top outlet of the hydrogen peroxide ultrasonic atomizer 7 is connected to the spray grille 8. The spray grille 8 is located within the flue 9. Hydrogen peroxide from the hydrogen peroxide storage tank 2 is pumped into the mixing tank 6 by the hydrogen peroxide delivery pump 4. Simultaneously, the alkali solution from the alkali storage tank 1 is also delivered to the mixing tank 6 by the alkali metering pump 3. The hydrogen peroxide mixture then enters the hydrogen peroxide ultrasonic atomizer 7, where it is ultrasonically atomized into small droplets. These droplets are carried by compressed air into the spray grille 8, where NO is oxidized to NO2 in the flue 9.

[0039] like Figure 2 As shown, the hydrogen peroxide ultrasonic atomizer 7 includes a hydrogen peroxide inlet pipe 10, a bypass channel 11, an ultrasonic atomizing plate 12, an atomization outlet 13, a gas channel partition 14, a hydrogen peroxide atomization pool 15, a level gauge 16, and a compressed air pipe 17. The hydrogen peroxide inlet pipe 10 is located at the top of the hydrogen peroxide ultrasonic atomizer 7. The hydrogen peroxide atomization pool 15 is arranged in multiple layers on the inner wall of the hydrogen peroxide ultrasonic atomizer 7. The solution in the upper atomization pool can overflow to the lower atomization pool through the bypass channel 11. The bottom hydrogen peroxide atomization pool 15 is equipped with a level gauge 16. Each hydrogen peroxide atomization pool 15 has a central opening for the gas channel partition 14. The compressed air... Pipe 17 is arranged above the bottom hydrogen peroxide atomizing pool 15, and the outlet pipe of compressed air pipe 17 is arranged in the center and vertically upward. Hydrogen peroxide gradually overflows into the bottom hydrogen peroxide atomizing pool 15 through the bypass channel 11 of the hydrogen peroxide atomizing pool 15 above. The level is controlled by the liquid level gauge 16 located at the bottom of the hydrogen peroxide ultrasonic atomizer 7, so that the hydrogen peroxide in the hydrogen peroxide atomizing pool 15 is always at a stable liquid level, which is conducive to achieving the best atomization effect and atomization efficiency. At the same time, the compressed air arranged at the bottom of the hydrogen peroxide ultrasonic atomizer 7 flows from bottom to top through the compressed air pipe 17, carrying the ultrasonically atomized hydrogen peroxide droplets out from the atomization outlet 13.

[0040] The height from the inlet of the bypass channel 11 to the bottom of the hydrogen peroxide atomization pool 15 on the same floor is 4cm. The hydrogen peroxide liquid level can be maintained at the optimal height of 4cm, ensuring that the atomized particle size of the hydrogen peroxide is between 1um and 5um, so as to achieve the best effect and atomization efficiency of ultrasonic atomization.

[0041] The height of the gas channel partition 14 is 3cm greater than the height from the inlet of the bypass channel 11 to the bottom of the hydrogen peroxide atomizing pool 15 on the same floor, to prevent the hydrogen peroxide solution from overflowing from the gas channel.

[0042] Among them, the ultrasonic atomizing plate 12 uses a glass glaze atomizing sheet to prevent hydrogen peroxide from corroding the atomizing plate during ultrasonic atomization.

[0043] In this process, the outer shells of the ultrasonic atomizing plates 12 in the same hydrogen peroxide atomizing pool 15 are interconnected by wires to prevent electro-corrosion.

[0044] Among them, the injection grille 8 is arranged in the range of flue gas temperature of 200℃~500℃ to ensure oxidation efficiency.

[0045] In practical applications, a hydrogen peroxide ultrasonic atomization oxidation system for NO in flue gas, such as... Figure 1 As shown, the hydrogen peroxide solution in hydrogen peroxide storage tank 2 is transported to mixing tank 6 by hydrogen peroxide transfer pump 4. Simultaneously, the alkali solution in alkali solution tank 1 is quantitatively transported to mixing tank 6 by alkali metering pump 3. After the transported hydrogen peroxide solution and alkali solution are mixed and adjusted to a certain pH value, they are then pumped into hydrogen peroxide ultrasonic atomizer 7. Figure 2 As shown, the hydrogen peroxide atomizing pools 15 in the ultrasonic hydrogen peroxide atomizer 7 are arranged in layers. Hydrogen peroxide gradually overflows from the upper layer of hydrogen peroxide atomizing pool 15 through the bypass channel 11 to the bottom layer of hydrogen peroxide atomizing pool 15. By controlling the liquid level gauge 16 in the bottom layer of hydrogen peroxide atomizing pool 15, the hydrogen peroxide in the hydrogen peroxide atomizing pool 15 is kept at a stable liquid level, which is conducive to achieving the best atomization effect and atomization efficiency. At the same time, the compressed air pipe 17 arranged at the bottom of the ultrasonic hydrogen peroxide atomizer 7 causes compressed air to flow from bottom to top, carrying the atomized hydrogen peroxide droplets into the spray grille 8 and being sprayed out. The hydrogen peroxide droplets entering the high-temperature flue gas rapidly decompose into hydroxyl radicals, which efficiently oxidize NO in the flue gas into NO2.

[0046] After adjusting the pH value of the hydrogen peroxide solution to an alkaline solution, ultrasonic atomization is performed. The atomized hydrogen peroxide droplets are carried by compressed air and injected into flue 9, where the flue gas temperature is 200℃~500℃. At high temperature, the hydrogen peroxide decomposes to produce oxidizing free radicals, which oxidize NO in the flue gas to NO2.

[0047] The molar ratio of hydrogen peroxide to NO in the flue gas is 1 to 2.

[0048] The pH value of the mixed solution after adding alkali to hydrogen peroxide solution is 5-8.

[0049] Based on the above system, the method of the present invention, by setting a mixing tank 6 before ultrasonic atomization, allows the use of mixed alkaline solution to adjust the pH value of hydrogen peroxide during the delivery process, thereby making it easier for hydrogen peroxide to directionally decompose strong oxidizing free radicals at high temperatures; simultaneously, the hydrogen peroxide atomization pool 15 in the ultrasonic hydrogen peroxide atomizer 7 is arranged in layers, with hydrogen peroxide gradually overflowing from the upper layer hydrogen peroxide atomization pool 15 to the bottom layer hydrogen peroxide atomization pool 15 through bypass channel 11, and the amount of atomized hydrogen peroxide entering the ultrasonic hydrogen peroxide atomizer... The amounts of 7 are basically equal, and the hydrogen peroxide is in a continuous flow state to prevent the hydrogen peroxide solution from decomposing due to the temperature rise caused by ultrasonic action. At the same time, the stable liquid level ensures the best atomization effect and atomization efficiency. The atomized hydrogen peroxide is carried into the spray grid 8 by compressed air. The droplet size of the ultrasonically atomized hydrogen peroxide is small, which significantly increases the gas-liquid contact area and shortens the heating process. This allows the hydrogen peroxide droplets to be rapidly heated and decomposed by the high-temperature hot flue gas, generating strong oxidizing hydroxyl radicals, which efficiently oxidize NO in the flue gas into NO2.

[0050] Specifically, when the liquid level gauge 16 at the bottom of the hydrogen peroxide ultrasonic atomizer 7 indicates a liquid level greater than 7cm, the alkali metering pump 3 and the hydrogen peroxide delivery pump 4 stop operating; when the liquid level gauge 16 indicates a liquid level less than 3cm, the alkali metering pump 3 and the hydrogen peroxide delivery pump 4 start operating, thereby ensuring the safe and efficient operation of the hydrogen peroxide ultrasonic atomizer 7.

[0051] In this process, the ultrasonic atomizing plate 12 in each layer of hydrogen peroxide atomizing pool 15 is individually controlled by the start and stop circuit, so that the atomization amount of the hydrogen peroxide atomizer 7 can be adjusted.

[0052] The research results on the oxidation of NO by H2O2 using a gas-liquid two-phase flow nozzle are as follows: Figure 3 As shown, the hydrogen peroxide particles atomized by compressed air have a large size, and the oxidation efficiency of NO by this process is only 50%; the research results of oxidizing NO by ultrasonic atomization of H2O2 using the present invention are as follows: Figure 4 As shown, the oxidation efficiency of NO is over 95%.

[0053] In this preferred embodiment, the concentration of NO in the flue gas is 300 mg / m³. 3 (mg / m 3 m 3(Under standard conditions, the same below) The alkali tank 1 contains 5% ammonia water. The pH value of the mixing tank 6 is adjusted to about 5 by the alkali metering pump 3. The hydrogen peroxide atomizing pool 15 in the hydrogen peroxide ultrasonic atomizer 7 is arranged in 4 layers. The ultrasonic atomizing plate 12 is made of ceramic glaze atomizing sheet. Each layer of ultrasonic atomizing plate 12 is connected to the outer shell by wires. The height from the inlet of the bypass channel 11 to the bottom of the hydrogen peroxide atomizing pool 15 on the same layer is 4cm. The height of the gas channel partition 14 is 7cm. The hydrogen peroxide concentration in the hydrogen peroxide storage tank 2 is 27.5%. The molar ratio of hydrogen peroxide atomization amount to NO in the flue gas is 1. Compressed air carries the ultrasonically atomized hydrogen peroxide droplets into the 400℃ flue gas through the spray grille 8, achieving an NO oxidation efficiency of 97.3%.

[0054] Example 2

[0055] In this preferred embodiment, the concentration of NO in the flue gas is 150 mg / m³. 3 The alkali tank 1 contains 1% sodium hydroxide. The pH value of the mixing tank 6 is adjusted to about 8 by the alkali metering pump 3. The hydrogen peroxide atomizing pool 15 in the hydrogen peroxide ultrasonic atomizer 7 is arranged in 5 layers. The ultrasonic atomizing plate 12 is made of ceramic glaze atomizing sheet. Each layer of ultrasonic atomizing plate 12 is connected to the outer shell by wires. The height from the inlet of the bypass channel 11 to the bottom of the hydrogen peroxide atomizing pool 15 in the same layer is 2cm. The height of the gas channel partition 14 is 8cm. The hydrogen peroxide concentration in the hydrogen peroxide storage tank 2 is 20%. The molar ratio of hydrogen peroxide atomization amount to NO in the flue gas is 2. Compressed air carries the ultrasonically atomized hydrogen peroxide droplets into the 200°C flue gas through the spray grille 8, achieving an NO oxidation efficiency of 96%.

[0056] Example 3

[0057] In this preferred embodiment, the concentration of NO in the flue gas is 200 mg / m³. 3 The alkali tank 1 contains 1% ammonia solution. The pH value of the mixing tank 6 is adjusted to about 6 by the alkali metering pump 3. The hydrogen peroxide atomizing pool 15 in the hydrogen peroxide ultrasonic atomizer 7 is arranged in 4 layers. The ultrasonic atomizing plate 12 is made of ceramic glaze atomizing sheet. Each layer of ultrasonic atomizing plate 12 is connected to the outer shell by wires. The height from the inlet of the bypass channel 11 to the bottom of the hydrogen peroxide atomizing pool 15 on the same layer is 3cm. The height of the gas channel partition 14 is 7cm. The hydrogen peroxide concentration in the hydrogen peroxide storage tank 2 is 10%. The molar ratio of hydrogen peroxide atomization amount to NO in the flue gas is 1.4. Compressed air carries the ultrasonically atomized hydrogen peroxide droplets through the spray grille 8 into the flue gas at 350°C, achieving an NO oxidation efficiency of 98.5%.

[0058] Example 4

[0059] In this preferred embodiment, the concentration of NO in the flue gas is 500 mg / m³. 3The alkali tank 1 contains 0.5% calcium hydroxide. The pH value of the mixing tank 6 is adjusted to about 7 by the alkali metering pump 3. The hydrogen peroxide atomizing pool 15 in the hydrogen peroxide ultrasonic atomizer 7 is arranged in 4 layers. The ultrasonic atomizing plate 12 is made of ceramic glaze atomizing sheet. Each layer of ultrasonic atomizing plate 12 is connected to the outer shell by wires. The height from the inlet of the bypass channel 11 to the bottom of the hydrogen peroxide atomizing pool 15 in the same layer is 4cm. The height of the gas channel partition 14 is 7cm. The hydrogen peroxide concentration in the hydrogen peroxide storage tank 2 is 50%. The molar ratio of hydrogen peroxide atomization amount to NO in the flue gas is 1.1. Compressed air carries the ultrasonically atomized hydrogen peroxide droplets into the 420℃ flue gas through the spray grille 8, achieving an NO oxidation efficiency of 99.5%.

Claims

1. A hydrogen peroxide ultrasonic atomization oxidation flue gas NO system, characterized in that, The system comprises a hydrogen peroxide ultrasonic atomizer (7), a hydrogen peroxide pH value adjusting system, and a spray grid (8) arranged in a flue (9). The hydrogen peroxide ultrasonic atomizer (7) is provided with an atomizing outlet (13) at the top, a hydrogen peroxide inlet pipe (10) at the side wall of the top, and a compressed air pipe (17) at the side wall of the bottom; the liquid droplets atomized by the hydrogen peroxide ultrasonic atomizer (7) have a size of 1um-5um, and are carried into the spray grid (8) by compressed air in the compressed air pipe (17). The hydrogen peroxide pH value adjusting system comprises a mixing tank (6), an alkali storage tank (1), and a hydrogen peroxide storage tank (2); the mixing tank (6) is provided with a pH meter (5) therein, and the inlet of the mixing tank (6) is connected with the alkali storage tank (1) and the hydrogen peroxide storage tank (2) respectively, and the outlet of the mixing tank (6) is connected with the hydrogen peroxide inlet pipe (10); the system is used for adjusting the hydrogen peroxide solution added into the alkali solution to a set pH value of 5-8. The inlet of the spray grid (8) is connected with the atomizing outlet (13), and the spray grid (8) is arranged in the flue (9) with a flue gas temperature in a range of 200℃-500℃. The hydrogen peroxide ultrasonic atomizer (7) is in a tank shape, and is provided with multiple layers of hydrogen peroxide atomizing pools (15) arranged in sequence and at intervals from the bottom to the top inside; each hydrogen peroxide atomizing pool (15) above the bottom layer is coaxially provided with an opening in the center, and is provided with a gas passage partition plate (14) upward at each opening; each hydrogen peroxide atomizing pool (15) above the bottom layer is provided with a bypass passage (11); each hydrogen peroxide atomizing pool (15) is provided with an ultrasonic atomizing plate (12) therein, and the hydrogen peroxide atomizing pool (15) of the bottom layer is further provided with a liquid level meter (16); the compressed air pipe (17) is located above the hydrogen peroxide atomizing pool (15) of the bottom layer, and the outlet of the compressed air pipe (17) is coaxial with the opening and is arranged vertically upward. The height of the inlet of the bypass passage (11) to the bottom of the same layer of hydrogen peroxide atomizing pool (15) is 2cm-4cm. The height of the gas passage partition plate (14) is greater than the height of the bottom of the same layer of hydrogen peroxide atomizing pool (15) by at least 3cm. The ultrasonic atomizing plate (12) adopts an atomizing sheet with a ceramic glaze surface, the housings of the ultrasonic atomizing plates (12) arranged in the same layer of hydrogen peroxide atomizing pool (15) are interconnected by wires; the ultrasonic atomizing plates (12) in each layer of hydrogen peroxide atomizing pool (15) are controlled by separate start-stop circuits.

2. The hydrogen peroxide ultrasonic atomization oxidation flue gas NO system according to claim 1, characterized in that, An alkali metering pump (3) is arranged on the connecting pipeline between the mixing tank (6) and the alkali storage tank (1); a hydrogen peroxide delivery pump (4) is arranged on the connecting pipeline between the mixing tank (6) and the hydrogen peroxide storage tank (2).

3. A method of ultrasonic atomization of hydrogen peroxide for oxidation of flue gas NO, characterized in that, The system according to any one of claims 1-2, comprising, After the hydrogen peroxide solution is added into the alkali solution and adjusted to a set pH value, ultrasonic atomization is performed, and the hydrogen peroxide small droplets with a size of 1um-5um after atomization are carried into the flue (9) with a flue gas temperature of 200℃-500℃ by compressed air, and are decomposed at high temperature to generate oxidizing free radicals, so as to oxidize NO in the flue gas into NO2; The pH value of the mixed solution after the hydrogen peroxide solution is added into the alkali solution is 5-8. The molar ratio of the hydrogen peroxide to the NO in the flue gas is 1-2.

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