Flue gas wet denitration reaction system and method

Abstract

The invention relates to the technical field of flue gas denitration, and discloses a flue gas wet-process denitration reaction system and method.The flue gas wet-process denitration reaction method comprises the steps that flue gas and air are mixed to form mixed gas, and then the mixed gas is fed into a denitration reactor containing absorption liquid to be subjected to denitration reaction. The concentration of NOx in the flue gas is directly reduced, and the problem that the NOx in the flue gas fluctuates to a relatively high concentration, so that sufficient denitration cannot be realized is effectively avoided; besides, oxygen contained in the air can react with NO in the flue gas and partially generate NO2, the problem that the denitration efficiency is low due to the fact that NO is insoluble in water is solved, the flue gas diluted by the air can be rapidly subjected to denitration reaction in the denitration reactor 200, and the denitration efficiency is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitration, and particularly to a wet flue gas denitration reaction system and method. Background Art

[0002] Nitrogen oxides (NO x ) are one of the main pollutants in the atmosphere. Their excessive emissions can cause various environmental problems, including acid rain, photochemical smog, etc. Controlling the emission of NO x is an inevitable requirement for achieving sustainable development. The NO x polluting the atmosphere mainly includes NO and NO 2 , among which NO accounts for more than 90% of the total content of NO x in industrial flue gas. China has formulated strict emission standards for the content of NO x in industrial flue gas, and various flue gas denitration technologies have also been vigorously developed.

[0003] In production practice, due to factors such as production process changes, load fluctuations, and fuel characteristics, the content of NO x in industrial flue gas usually fluctuates, and the fluctuation range can be as high as dozens to tens of thousands of ppm. When using wet denitration technology to treat NO x in industrial flue gas, the existing technology adjusts the dosage of the denitration agent in the denitration system in real time by monitoring the concentration of NO x in industrial flue gas to adapt to the fluctuation of the NO x content. However, it takes a certain amount of time for the newly added denitration agent to be evenly distributed throughout the denitration system, resulting in a certain lag in this operation strategy. There is still a problem that high-concentration NO x overflows the denitration system before it can be processed during the actual operation process. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that the existing wet denitration technology cannot adapt to the fluctuation of NO x in industrial flue gas to a higher concentration, and to provide a wet flue gas denitration reaction system and method. This wet flue gas denitration reaction method can not only effectively cope with the problem of the fluctuation of NO x in industrial flue gas to a higher concentration, but also effectively improve the denitration efficiency.

[0005] To achieve the above purpose, in the first aspect of the present invention, a wet flue gas denitration reaction method is provided. This wet flue gas denitration reaction method includes mixing the flue gas with air to form a mixed gas, and then sending it into a denitration reactor filled with an absorbent solution for denitration reaction.

[0006] Preferably, the wet flue gas denitration reaction method further includes mixing the mixed gas with the absorbent liquid to form a mixed liquid containing micro-nano bubbles, and then introducing the mixed liquid containing micro-nano bubbles into the denitration reactor for denitration reaction;

[0007] Preferably, the gas-liquid volume ratio of the mixed liquid containing micro-nano bubbles is (1-3):10.

[0008] Preferably, the absorbent liquid is a urea solution, hydrogen peroxide or a combination thereof;

[0009] Wherein, when the absorbent liquid contains hydrogen peroxide, the denitration reactor is filled with a supported catalyst, and the active component of the supported catalyst is monodispersed Fe 3 O 4 spinel nanoparticles;

[0010] Preferably, the average particle size of the Fe 3 O 4 spinel nanoparticles is 10-20 nm, preferably 12 nm;

[0011] Preferably, the loading amount of Fe in the supported catalyst is 10-30 wt.%, preferably 20 wt.%;

[0012] Preferably, the size of the supported catalyst is 80-120 mesh;

[0013] Preferably, the carrier of the supported catalyst is activated carbon, carbon black, P25-type titanium dioxide or α-Al 2 O 3 .

[0014] The second aspect of the present invention provides a wet flue gas denitration reaction system for denitrating flue gas. The wet flue gas denitration reaction system includes a gas mixing unit and a denitration reactor. The gas mixing unit is used to mix air with the flue gas to form a mixed gas, and the denitration reactor is used for the mixed gas and an absorbent liquid capable of participating in the denitration reaction to carry out the denitration reaction.

[0015] Preferably, the gas mixing unit includes a gas mixing tank. The upper end of the gas mixing tank is provided with a tank opening. A baffle is arranged in the gas mixing tank. The upper end of the baffle extends to the tank opening and can divide the tank opening into an air inlet and an air outlet located on both sides of the baffle. The lower end of the baffle is adjacent to and spaced from the bottom of the gas mixing tank to divide the interior of the gas mixing tank into chambers located on both sides of the baffle and communicating at the bottom.

[0016] Preferably, the wet flue gas denitration reaction system further includes a gas dryer, which is connected to the gas outlet of the denitration reactor through an outlet pipe, and the gas dryer is configured to dry the gas generated by the denitration reaction.

[0017] Preferably, a stirring mechanism is provided in the denitration reactor for stirring and mixing the mixed gas and the absorbent liquid participating in the denitration reaction; and / or

[0018] A jacket is provided on the outer wall of the denitration reactor, and the jacket is configured to allow a heat exchange medium to circulate for controlling the temperature inside the denitration reactor.

[0019] Preferably, the wet flue gas denitration reaction system further includes a micro-nano bubble generator disposed between the gas mixing unit and the denitration reactor, and the micro-nano bubble generator is configured to mix the mixed gas and the absorbent liquid to form a mixed liquid containing micro-nano bubbles and feed it into the denitration reactor.

[0020] Preferably, the micro-nano bubble generator includes a high-pressure pump, a high-pressure gas dissolving tank, and a throttling gas releasing head connected in sequence. The high-pressure pump is used to pressurize and transport the mixed gas and the absorbent liquid into the high-pressure gas dissolving tank. The high-pressure gas dissolving tank allows the mixed gas to dissolve in the absorbent liquid, and the throttling gas releasing head is configured to release the mixed gas dissolved in the absorbent liquid to form a mixed liquid containing the micro-nano bubbles;

[0021] Preferably, the aperture of the throttling orifice of the throttling gas releasing head is 2 mm - 15 mm.

[0022] Preferably, the wet flue gas denitration reaction system further includes a liquid storage tank for storing the absorbent liquid that can participate in the denitration reaction. A feeding pipe is provided between the liquid storage tank and the micro-nano bubble generator for feeding the absorbent liquid into the micro-nano bubble generator;

[0023] Preferably, a return pipe is provided between the denitration reactor and the liquid storage tank, and a circulation pump is provided on the return pipe for transporting the absorbent liquid in the denitration reactor back to the liquid storage tank.

[0024] In the wet flue gas denitration reaction method provided by the present invention, by mixing the flue gas with air, the concentration of NO in the flue gas is directly reduced, effectively avoiding the problem that the concentration of NO in the flue gas fluctuates to a high level and causes insufficient denitration; in addition, the oxygen contained in the air can also react with NO in the flue gas and partially generate NO x in the flue gas, x and the problem that it is impossible to fully denitrate due to the fluctuation of NO to a high concentration is effectively avoided; in addition, the oxygen contained in the air can also react with NO in the flue gas and partially generate NO 2, it overcomes the problem of low denitration efficiency caused by the insolubility of NO in water. The flue gas diluted by air can quickly carry out the denitration reaction in the denitration reactor and has excellent denitration efficiency. Description of the Drawings

[0025] Figure 1 is a schematic diagram of a wet flue gas denitration reaction system provided by the present invention;

[0026] Figure 2 is a schematic structural diagram of a micro-nano bubble generator provided by the present invention;

[0027] Figure 3 is a schematic diagram of a test system of a wet flue gas denitration reaction system provided by the present invention.

[0028] Description of the Reference Numerals

[0029] 1. Air source; 2. Flue gas source; 3. Flue gas analysis system; 4. First stop valve; 5. Second stop valve; 100. Gas mixing unit; 110. Gas mixing tank; 111. Tank opening; 1111. Inlet; 1112. Outlet; 120. Baffle; 200. Denitration reactor; 210. Stirring mechanism; 220. Jacket; 300. Gas dryer; 310. Outlet pipe; 400. Micro-nano bubble generator; 410. High-pressure pump; 420. High-pressure gas dissolving tank; 430. Throttling gas release head; 500. Liquid storage tank; 510. Feeding pipe; 520. Return pipe; 521. Circulation pump. Detailed Embodiments

[0030] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and understanding the present invention, and are not used to limit the present invention.

[0031] The first aspect of the present invention provides a wet flue gas denitration reaction method, which includes mixing flue gas with air to form a mixed gas, and then sending it into a denitration reactor 200 filled with an absorption liquid for denitration reaction.

[0032] In the wet flue gas denitration reaction method provided by the present invention, by mixing flue gas with air, the concentration of NO in the flue gas is directly reduced, effectively avoiding the problem that the denitration cannot be fully carried out due to the fluctuation of NO in the flue gas to a high concentration; in addition, the oxygen contained in the air can also react with NO in the flue gas and partially generate NO x to overcome the problem of low denitration efficiency caused by the insolubility of NO in water. The flue gas diluted by air can quickly carry out the denitration reaction in the denitration reactor 200 and has excellent denitration efficiency. x 2 ​​

[0033] In some embodiments, the wet flue gas denitration reaction method further includes mixing the mixed gas with the absorbent liquid to form a mixed liquid containing micro-nano bubbles, and then introducing the mixed liquid containing micro-nano bubbles into the denitration reactor 200 for denitration reaction.

[0034] In the present invention, in order to obtain better denitration efficiency, the gas-liquid volume ratio of the mixed liquid containing micro-nano bubbles is (1-3):10.

[0035] It should be noted that in the present invention, the absorbent liquid can react with NO in the flue gas x to generate harmless gas or dilute nitric acid. In some embodiments, the absorbent liquid is a urea solution, hydrogen peroxide, or a combination thereof. When the absorbent liquid contains hydrogen peroxide, the denitration reactor 200 is filled with a supported catalyst, and the active component of the supported catalyst is monodispersed Fe 3 O 4 spinel nanoparticles.

[0036] When the absorbent liquid is a urea solution, the principle of the denitration reaction in the present invention is as follows:

[0037] 1) NO reacts with O in the air 2 to generate NO 2 , and there is also a reversible conversion of NO x to N 2 O 2 O 4 , and the reaction of NO with NO 2 to convert to N 2 O 3 .

[0038] 2NO + O 2 → 2NO 2

[0039] 2NO 2 → N 2 O 4

[0040] NO + NO 2 → N 2 O 3

[0041] 2) NO x reacts with H 2 O.

[0042] N 2 O 3 + H 2 O → 2HNO 2

[0043] 2NO 2 +H 2 O→HNO 2 +HNO 3

[0044] N 2 O 4 +H 2 O→HNO 2 +HNO 3

[0045] 3)HNO 2 The chemical equation for the reaction with urea:

[0046] 2HNO 2 +(NH 2 ) 2 CO→2N 2 +CO 2 +3H 2 O

[0047] The overall chemical equation is: NO + NO 2 +CO(NH 2 ) 2 →2N 2 +2H 2 O + CO 2 .

[0048] When the absorbent is hydrogen peroxide, the principle of the denitrification reaction in the present invention is:

[0049] H 2 O 2 →2·OH (under the catalysis of Fe 3 O 4 nano - particles)

[0050] ·OH + NO → ·HONO

[0051] ·OH + ·HONO → ·NO 2 +H 2 O

[0052] •OH + NO 2 →•HNO 3

[0053] The inventors of the present application found that by mixing urea solution with hydrogen peroxide to form an absorbent, the hydrogen peroxide therein can generate hydroxyl radicals (•OH) under the action of the supported catalyst. Due to the strong oxidizing property of hydroxyl radicals, NO in the flue gas x is efficiently removed.

[0054] In the present invention, in the urea solution, the content of urea is 5 wt.% - 20 wt.%; in the hydrogen peroxide solution, the content of hydrogen peroxide is 0.25 wt.% - 1.0 wt.%.

[0055] Further, the average particle size of the Fe 3 O 4 spinel nanoparticles is 10 - 20 nm, preferably 12 nm; the loading amount of Fe in the supported catalyst is 10 - 30 wt.%, preferably 20 wt.%; the size of the supported catalyst is 80 - 120 mesh; the carrier of the supported catalyst is activated carbon, carbon black, P25-type titanium dioxide or α-Al 2 O 3 .

[0056] Generally speaking, the wet flue gas denitrification reaction method provided by the present invention uses inexpensive urea solution and / or hydrogen peroxide solution as the absorbent for wet flue gas denitrification, overcoming the problems of strong absorbent corrosivity, difficult storage and transportation, and high cost existing in other wet denitrification technologies, such as alkali solution absorption method, acid absorption method, and complexation absorption method. Compared with NH 3 -SCR, the wet flue gas denitrification reaction method provided by the present invention also avoids the escape problem of the reducing agent NH 3 . In addition, the inventors of the present application also found that through the synergistic effect of urea solution and hydrogen peroxide solution, the disadvantage of insufficient denitrification efficiency of a single-component absorbent is overcome. Combining the role of the supported catalyst in promoting the conversion of H 2 O 2 into hydroxyl radicals (•OH), the removal rate of NO x in flue gas reaches 99.9%, exceeding most of the existing technologies.

[0057] In the wet flue gas denitrification reaction method provided by the present invention, the denitrification products are N 2 , CO 2 , H 2 O and dilute nitric acid, without generating secondary pollutants, having the advantages of greenness and environmental protection.

[0058] In the wet flue gas denitrification reaction method provided by the present invention, by dispersing NO x in the form of micro-nano bubbles in the absorbent, the residence time of NO x in the absorbent is increased, and the gas-liquid contact area is improved, thus significantly improving the denitrification efficiency.

[0059] In a second aspect of the present invention, a wet flue gas denitration reaction system is provided for denitrating flue gas. The wet flue gas denitration reaction system includes a gas mixing unit 100 and a denitration reactor 200. The gas mixing unit 100 is configured to mix air with the flue gas to form a mixed gas, and the denitration reactor 200 is for the mixed gas to react with an absorbent liquid capable of participating in the denitration reaction.

[0060] In the wet flue gas denitration reaction system provided by the present invention, by setting the gas mixing unit 100 to mix the flue gas with air, the concentration of NO in the flue gas is directly reduced. x The problem that the concentration of NO in the flue gas fluctuates to a high concentration, resulting in insufficient denitration, is effectively avoided. In addition, the oxygen contained in the air can react with NO in the flue gas and partially generate NO. x Thereby, the problem that NO is insoluble in water and leads to low denitration efficiency is overcome. The flue gas treated by the gas mixing unit 100 can rapidly carry out the denitration reaction in the denitration reactor 200 and has excellent denitration efficiency. 2

[0061] It can be understood that as the amount of air incorporated into the flue gas gradually increases, the concentration of NO in the flue gas gradually decreases, enabling it to rapidly complete the denitration reaction after being introduced into the denitration reactor 200. However, too much mixed gas formed by air and flue gas will result in a long time required to complete the introduction into the denitration reactor 200, and reduce the flue gas treatment capacity per unit time, thereby leading to low overall denitration efficiency. It can be seen from this that the degree of diluting the flue gas with air depends on the denitration capacity of the denitration reactor 200, and it is appropriate that the concentration of NO in the diluted flue gas does not exceed the denitration capacity of the denitration reactor 200. Or rather, even if the concentration of NO in the flue gas fluctuates to a very high concentration due to various factors, through the dilution effect of the gas mixing unit 100 provided by the present invention, the concentration of NO in the flue gas can be diluted to not exceed the denitration capacity of the denitration reactor 200. In some embodiments of the present invention, the flue gas is diluted by the air to a content of NO in the mixed gas of 300 - 1000 ppm. x x x x x

[0062] It should be noted that the present invention does not make special limitations on the specific structure of the gas mixing unit 100, as long as it can fully mix the flue gas and air. In a specific embodiment of the present invention, the gas mixing unit 100 includes a gas mixing tank 110. The upper end of the gas mixing tank 110 is provided with a tank opening 111. A baffle 120 is arranged inside the gas mixing tank 110. The upper end of the baffle 120 extends to the tank opening 111 and can divide the tank opening 111 to form an air inlet 1111 and an air outlet 1112 on both sides of the baffle 120. The lower end of the baffle 120 is adjacent to and spaced from the bottom of the gas mixing tank 110 to divide the interior of the gas mixing tank 110 into chambers on both sides of the baffle 120 and communicate at the bottom. When the gas mixing tank 110 is specifically used, the flue gas and air enter the gas mixing tank 110 through the air inlet 1111, and are fully mixed during the process of flowing from one chamber on one side of the baffle 120 to the other chamber, and flow out from the air outlet 1112. The gas mixing tank 110 provided by the present invention has the advantages of simple structure and convenient use, and can effectively realize the full mixing of the flue gas and air.

[0063] In some embodiments, the wet flue gas denitration reaction system further includes a gas dryer 300. The gas dryer 300 is connected to the gas outlet of the denitration reactor 200 through an outlet pipe 310. The gas dryer 300 is configured to dry the gas generated by the denitration reaction.

[0064] The present invention does not make special limitations on the structure of the gas dryer 300, as long as it can fully dry the gas generated by the denitration reaction. In a specific embodiment of the present invention, the gas dryer 300 is a gas drying tank with an inlet end and an outlet end. A desiccant is filled in the gas drying tank. The gas generated by the denitration reaction enters the gas drying tank from the inlet end and flows out from the outlet end after being dried by the desiccant. The desiccant can be a common gas desiccant in the art, such as silica gel, molecular sieve or CaCl 2 。

[0065] In the present invention, the denitration reactor 200 is for the NO in the flue gas x to carry out a denitration reaction with the absorbent solution. The present invention does not make special limitations on the specific structural form of the denitration reactor 200, as long as it can make the flue gas and the absorbent solution fully contact. Combining Figure 1As shown, the denitration reactor 200 is in the form of a reaction kettle. In some embodiments, a stirring mechanism 210 is provided in the denitration reactor 200 to stir and mix the mixed gas and the absorbent participating in the denitration reaction. Through the stirring and mixing of the stirring mechanism 210, the contact and mixing of the mixed gas and the absorbent are promoted, and the denitration reaction is promoted to proceed more efficiently; in addition, the dissolution of the tail gas after the denitration reaction can also be accelerated through the stirring action of the stirring mechanism 210. The present invention does not make special limitations on the stirring speed of the stirring mechanism 210. In some embodiments, the rotation speed of the stirring mechanism 210 is set to 20-200 rpm.

[0066] In some embodiments, a jacket 220 is provided on the outer wall of the denitration reactor 200, and the jacket 220 is arranged to allow a heat exchange medium to circulate for controlling the temperature inside the denitration reactor 200. Specifically, an inlet is provided at the bottom of the jacket 220, and an outlet is provided at the top. The heat exchange medium enters the jacket 220 from the inlet at the bottom, and after the heat exchange medium fills the entire jacket 220, it flows out from the outlet at the top. During this process, the heat exchange medium exchanges heat with the denitration reactor 200, thereby controlling the temperature inside the denitration reactor 200.

[0067] It can be understood that in the present invention, in order to increase the heat exchange capacity between the heat exchange medium and the denitration reactor 200, a plurality of baffle plates are also provided in the jacket 220, and the plurality of baffle plates are sequentially and staggeredly arranged on the inner walls on both sides of the jacket 220. By providing a plurality of baffle plates, the flow path of the heat exchange medium in the jacket 220 is increased, thereby increasing the heat exchange capacity between the heat exchange medium and the denitration reactor 200.

[0068] It should be noted that an important factor affecting the efficiency of wet denitration is the mixing degree and mass transfer rate between the flue gas and the absorbent. To achieve a high denitration efficiency, it is crucial to increase the gas-liquid contact area and residence time. Taking urea wet denitration as an example, currently, industrial urea wet denitration is usually carried out in a high-gravity rotating packed bed or an absorption tower. By setting a liquid distributor, adding packing, or cutting the liquid and gas through the high-speed rotation of the rotor, the contact area between the gas-liquid two phases is increased, and the gas-liquid mass transfer is strengthened. However, the above methods have problems such as complex structure, high energy consumption, and large equipment investment; in addition, high-gravity rotating packed beds and absorption towers usually require a relatively high temperature to have a sufficiently high denitration efficiency, and the denitration efficiency at room temperature is not ideal enough.

[0069] Based on this, in some embodiments of the present invention, the wet flue gas denitration reaction system further includes a micro-nano bubble generator 400 disposed between the gas mixing unit 100 and the denitration reactor 200. The micro-nano bubble generator 400 is configured to mix the mixed gas with the absorbent liquid to form a mixed liquid containing micro-nano bubbles and feed it into the denitration reactor 200.

[0070] Micro-nano bubbles generally refer to bubbles with a diameter less than 50 μm, which have characteristics such as a large specific surface area, high mass transfer efficiency, and self-pressurizing dissolution. By mixing the mixed gas with the absorbent liquid to form micro-nano bubbles, the contact interface between NO in the mixed gas and the absorbent liquid is increased, the denitration reaction rate is accelerated, and the wet denitration efficiency is improved. x Between the absorbent liquid, the denitration reaction rate is accelerated, and the wet denitration efficiency is improved.

[0071] In the present invention, no special limitation is imposed on the specific structure of the micro-nano bubble generator 400, as long as it can mix the mixed gas formed by flue gas and air into the absorbent liquid to form a mixed liquid containing micro-nano bubbles. In a specific embodiment of the present invention, as shown in Figure 2 Shown, the micro-nano bubble generator 400 includes a high-pressure pump 410, a high-pressure gas dissolving tank 420, and a throttling gas release head 430 connected in sequence. The high-pressure pump 410 is used to pressurize and transport the mixed gas and the absorbent liquid to the high-pressure gas dissolving tank 420. The high-pressure gas dissolving tank 420 allows the mixed gas to dissolve in the absorbent liquid. The throttling gas release head 430 is configured to release the mixed gas dissolved in the absorbent liquid to form a mixed liquid containing the micro-nano bubbles.

[0072] In the present invention, in order to further improve the efficiency of the denitration reaction, the aperture of the throttling hole of the throttling gas release head 430 is 2 mm - 15 mm.

[0073] In the present invention, the high-pressure pump 410 may specifically adopt a self-priming diaphragm pump to transport and pressurize the mixed gas and the absorbent liquid through the self-priming diaphragm pump. In the high-pressure gas dissolving tank 420, due to the formation of a high back pressure of 0.3 - 0.5 MPa in the high-pressure gas dissolving tank 420, a large amount of the mixed gas dissolves in the absorbent liquid. Further, the liquid flow rate is increased through the throttling hole of the throttling gas release head 430, causing the liquid pressure to drop suddenly, and a large amount of the mixed gas dissolved in the liquid is released to form micro-nano bubbles.

[0074] In some embodiments, as shown in Figure 1 Shown, the wet flue gas denitration reaction system further includes a liquid storage tank 500 for storing the absorbent liquid capable of participating in the denitration reaction. A feed pipe 510 is provided between the liquid storage tank 500 and the micro-nano bubble generator 400 to feed the absorbent liquid into the micro-nano bubble generator 400;

[0075] Furthermore, a return pipe 520 is provided between the denitration reactor 200 and the liquid storage tank 500, and a circulation pump 521 is provided on the return pipe 520 for conveying the absorption liquid in the denitration reactor 200 back to the liquid storage tank 500. When the flue gas wet denitration reaction system is specifically used, the absorption liquid from the liquid storage tank 500 and the mixed gas from the gas mixing unit 100 are conveyed to the micro-nano bubble generator 400 in a certain proportion. The micro-nano bubble generator 400 forms a mixed liquid containing micro-nano bubbles, and then the mixed liquid containing micro-nano bubbles is conveyed to the denitration reactor 200 for denitration reaction. The tail gas generated after the reaction is gradually released from the absorption liquid in the denitration reactor 200 and enters the gas dryer 300 for drying. The absorption liquid in the denitration reactor 200 can also be conveyed back to the liquid storage tank 500 through the circulation pump 521 for supplying liquid to the micro-nano bubble generator 400. During the circulation process of the absorption liquid, the concentration of the absorption liquid is determined by sampling from the liquid storage tank 500, and when the concentration of the absorption liquid is lower than the required value, the absorption liquid is replenished into the liquid storage tank 500 in time.

[0076] It can be understood that in combination with Figure 1 as shown, when an absorption liquid is formed by compounding urea solution and hydrogen peroxide and a supported catalyst is added to the denitration reactor 200, a filter head is provided at the end of the return pipe 520 located inside the denitration reactor 200, and the filtration pore diameter of the filter head is less than 200 meshes to prevent the supported catalyst in the absorption liquid from being sucked into the circulation pump 521.

[0077] It can be understood that in order to accurately and conveniently control the amounts of the absorption liquid and the mixed gas entering the micro-nano bubble generator 400, a liquid flowmeter and a first control valve for controlling the flow rate of the liquid pipeline are provided on the liquid pipeline between the liquid storage tank 500 and the micro-nano bubble generator 400, and a gas flowmeter and a second control valve for controlling the flow rate of the gas pipeline are provided on the gas pipeline between the gas mixing unit 100 and the micro-nano bubble generator 400.

[0078] The following further illustrates the flue gas wet denitration reaction method provided by the present invention through specific embodiments.

[0079] Example 1

[0080] As Figure 1As shown in the figure, this embodiment provides a wet flue gas denitration reaction system, including a gas mixing unit 100, a micro-nano bubble generator 400, a denitration reactor 200, a gas dryer 300 and a liquid storage tank 500; the gas mixing unit 100 is used to mix air and flue gas to form a mixed gas. The gas mixing unit 100 includes a gas mixing tank 110. The upper end of the gas mixing tank 110 is provided with a tank opening 111. A baffle 120 is arranged inside the gas mixing tank 110. The upper end of the baffle 120 extends to the tank opening 111 and can divide the tank opening 111 into an air inlet 1111 and an air outlet 1112 located on both sides of the baffle 120. The lower end of the baffle 120 is adjacent to and spaced from the bottom of the gas mixing tank 110 to divide the interior of the gas mixing tank 110 into chambers located on both sides of the baffle 120 and communicating at the bottom; the micro-nano bubble generator 400 is arranged between the gas mixing unit 100 and the denitration reactor 200, and the micro-nano bubble generator 400 is configured to mix the mixed gas with the absorbent liquid to form a mixed liquid containing micro-nano bubbles and feed it into the denitration reactor 200.

[0081] The micro-nano bubble generator 400 includes a high-pressure pump 410, a high-pressure gas dissolving tank 420 and a throttling gas release head 430 connected in sequence. The high-pressure pump 410 is used to pressurize and transport the mixed gas and the absorbent liquid to the high-pressure gas dissolving tank 420. The high-pressure gas dissolving tank 420 is for the mixed gas to dissolve in the absorbent liquid. The throttling gas release head 430 is configured to release the mixed gas dissolved in the absorbent liquid to form a mixed liquid containing the micro-nano bubbles; the aperture of the throttling hole of the throttling gas release head 430 is 5 mm.

[0082] The denitration reactor 200 is for the mixed gas and the absorbent liquid capable of participating in the denitration reaction to carry out the denitration reaction.

[0083] A stirring mechanism 210 is arranged in the denitration reactor 200 to stir and mix the mixed gas and the absorbent liquid participating in the denitration reaction; a jacket 220 is arranged on the outer wall of the denitration reactor 200, and the jacket 220 is configured to allow a heat exchange medium to circulate to control the temperature inside the denitration reactor 200.

[0084] The gas dryer 300 is connected to the denitration reactor 200 through an outlet pipe 310 and is configured to be able to dry the gas generated by the denitration reaction. The liquid storage tank 500 is used to store the absorbent liquid that can participate in the denitration reaction. A feed pipe 510 is provided between the liquid storage tank 500 and the micro-nano bubble generator 400 to feed the absorbent liquid into the micro-nano bubble generator 400. A return pipe 520 is provided between the denitration reactor 200 and the liquid storage tank 500, and a circulation pump 521 is provided on the return pipe 520 to transport the absorbent liquid in the denitration reactor 200 back to the liquid storage tank 500.

[0085] To facilitate the study of the wet flue gas denitration reaction system provided by the present invention, several units are added to the Figure 1 wet flue gas denitration reaction system provided to facilitate research, such as Figure 3 shown, an air source 1 and a flue gas source 2 are provided on the feed side of the gas mixing tank 110, and a flue gas analysis system 3 is added at the outlet end of the gas dryer 300 to analyze the components of the dried tail gas.

[0086] Parallel pipelines are provided at the outlet end of the gas mixing tank 110, and in cooperation with the first stop valve 4 and the second stop valve 5 respectively provided on the parallel pipelines, the mixed gas can be selectively introduced into the micro-nano bubble generator 400 or the denitration reactor 200.

[0087] In this embodiment, by adjusting the ratio of the air source 1 to the flue gas source 2, the content of NO x in the mixed gas is 500 ppm.

[0088] The absorbent liquid stored in the liquid storage tank 500 is a urea solution, and the content of urea is 15 wt.%; by using the jacket 220 provided on the outer wall of the denitration reactor 200, the temperature of the absorbent liquid in the denitration reactor 200 is controlled at 30 °C.

[0089] An Antaris IGS online gas-phase Fourier transform infrared (FT-IR) spectrometer is used to measure the volume concentration of NO x in the flue gas before and after treatment respectively, and the denitration efficiency is calculated according to the following formula:

[0090] η=(c 处理前 -c 处理后 ) / c 原 ×100%

[0091] where η represents the denitration efficiency, c 处理前 represents the volume concentration of NO x in the flue gas before treatment, with the unit of ppm; c 处理后 represents the volume concentration of NO x in the flue gas after treatment, with the unit of ppm.

[0092] Example 2

[0093] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that the content of urea in the absorption liquid is 5 wt.%, and the rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0094] Example 3

[0095] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that the content of urea in the absorption liquid is 10 wt.%, and the rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0096] Example 4

[0097] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that the content of urea in the absorption liquid is 20 wt.%, and the rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0098] Example 5

[0099] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that by using the jacket 220 provided on the outer wall of the denitration reactor 200, the temperature of the absorption liquid in the denitration reactor 200 is controlled at 20 °C, and the rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0100] Example 6

[0101] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that by using the jacket 220 provided on the outer wall of the denitration reactor 200, the temperature of the absorption liquid in the denitration reactor 200 is controlled at 50 °C, and the rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0102] Example 7

[0103] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that by using the jacket 220 provided on the outer wall of the denitration reactor 200, the temperature of the absorption liquid in the denitration reactor 200 is controlled at 70 °C, and the rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0104] Example 8

[0105] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that by adjusting the ratio of the air source 1 to the flue gas source 2, the content of NO x in the mixed gas is 300 ppm. The rest remains unchanged. After testing, the denitration efficiency is calculated as shown in Table 1.

[0106] Example 9

[0107] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that by adjusting the ratio of the air source 1 to the flue gas source 2, the content of NO in the mixed gas x is 800 ppm. The rest remains unchanged. After testing, the denitration efficiency is shown in Table 1.

[0108] Example 10

[0109] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that by adjusting the ratio of the air source 1 to the flue gas source 2, the content of NO in the mixed gas x is 1000 ppm. The rest remains unchanged. After testing, the denitration efficiency is shown in Table 1.

[0110] Example 11

[0111] This example is basically the same as the wet flue gas denitration reaction system of Example 1. The difference is that the absorbent liquid in the liquid storage tank 500 is a mixture of urea solution and hydrogen peroxide, wherein the urea content is 15 wt.%, and the hydrogen peroxide content is 0.25 wt.%. The rest remains unchanged. After testing, the denitration efficiency is shown in Table 1.

[0112] Example 12

[0113] This example is basically the same as the wet flue gas denitration reaction system of Example 11. The difference is that the absorbent liquid in the liquid storage tank 500 is a mixture of urea solution and hydrogen peroxide, wherein the urea content is 15 wt.%, and the hydrogen peroxide content is 0.5 wt.%. The rest remains unchanged. After testing, the denitration efficiency is shown in Table 1.

[0114] Example 13

[0115] This example is basically the same as the wet flue gas denitration reaction system of Example 11. The difference is that the absorbent liquid in the liquid storage tank 500 is a mixture of urea solution and hydrogen peroxide, wherein the urea content is 15 wt.%, and the hydrogen peroxide content is 1.0 wt.%. The rest remains unchanged. After testing, the denitration efficiency is shown in Table 1.

[0116] Example 14

[0117] This example is basically the same as the wet flue gas denitration reaction system of Example 12. The difference is that in the denitration reactor 200, 1 g / L of supported catalyst is also loaded (1 g of supported catalyst is added to every 1 L of absorbent liquid), and the carrier of the supported catalyst is α-Al 2 O 3 , and the active component is monodispersed Fe3 O 4 Spinel nanoparticles, Fe 3 O 4 The average particle size of the spinel nanoparticles is 12 nm, the loading amount of Fe in the supported catalyst is 20 wt.%, and the size of the supported catalyst is 100 mesh.

[0118] The rest remains unchanged. After testing, the denitrification efficiency is calculated as shown in Table 1.

[0119] Example 15

[0120] This example is basically the same as the flue gas wet denitrification reaction system of Example 12. The difference is that in the denitrification reactor 200, the loading amount of the supported catalyst is 3 g / L (3 g of the supported catalyst is added to every 1 L of the absorbent). The rest remains unchanged. After testing, the denitrification efficiency is calculated as shown in Table 1.

[0121] Example 16

[0122] This example is basically the same as the flue gas wet denitrification reaction system of Example 12. The difference is that in the denitrification reactor 200, the loading amount of the supported catalyst is 5 g / L (5 g of the supported catalyst is added to every 1 L of the absorbent). The rest remains unchanged. After testing, the denitrification efficiency is calculated as shown in Table 1.

[0123] Comparative Example 1

[0124] This comparative example is basically the same as the flue gas wet denitrification reaction system of Example 1. The difference is that

[0125] the absorbent in the liquid storage tank 500 is pure water. The rest remains unchanged. After testing, the denitrification efficiency is calculated as shown in Table 1.

[0126] Comparative Example 2

[0127] This comparative example is basically the same as the flue gas wet denitrification reaction system of Example 1. The difference is that after the flue gas and air are mixed in the gas mixing tank 110, they are directly introduced into the denitrification reactor 200 without passing through the micro-nano bubble generator 400. The rest remains unchanged. After testing, the denitrification efficiency is calculated as shown in Table 1.

[0128] Comparative Example 3

[0129] This comparative example is basically the same as the flue gas wet denitrification reaction system of Example 1. The difference is that the absorbent in the liquid storage tank 500 is hydrogen peroxide, and the content of hydrogen peroxide in the hydrogen peroxide is 0.5 wt.%. The rest remains unchanged. After testing, the denitrification efficiency is calculated as shown in Table 1.

[0130] Table 1:

[0131]

[0132]

[0133] As can be seen from the results in Table 1, compared with using pure water as the absorbent in Comparative Example 1, under the same operating conditions, when using a urea solution as the absorbent and within the concentration range defined in the present invention, the denitration efficiency of Examples 1-4 is significantly improved, and the highest denitration efficiency can be increased to 96.5%.

[0134] By comparing Example 1 with Comparative Example 2, it can be seen that by using the micro-nano bubble generator 400 to carry out gas-liquid mixing of the mixed gas and the uric acid solution to form a mixed liquid containing micro-nano bubbles, the denitration efficiency can be greatly improved, from 25.2% to 94.6%.

[0135] In addition, by comparing Examples 1-7, it can be seen that by adjusting parameters such as the concentration of urea in the absorbent and the temperature of the absorbent in the denitration reactor, the denitration efficiency can be significantly improved; in addition, by comparing Example 1 with Examples 8-10, it can be seen that even if the x volume concentration of NO in the mixed gas changes greatly, the present invention can still maintain a high denitration efficiency.

[0136] As can be seen from Examples 1-10, when using a urea solution as the absorbent and combining with the micro-nano bubble technology, the denitration efficiency of the present invention has been greatly improved. On this basis, in Examples 11-13 of the present invention, different mass fractions of hydrogen peroxide are added to the absorbent to form a double absorbent with urea to exert their synergistic effect; in addition, in order to enhance the reaction rate between hydrogen peroxide and NO, different amounts of supported catalysts are added in Examples 14-16 to promote the rate of hydrogen peroxide generating hydroxyl radicals, thereby enhancing the oxidation of NO.

[0137] It can be known from the data in Table 1 that compared with the single-component absorbents used in Example 1 and Comparative Example 3, after using the urea + hydrogen peroxide double-component absorbent in Examples 11-13, the denitration efficiency has been greatly improved. In Example 11, 15 wt.% urea + 0.25 wt.% H 2 O 2 , the denitration efficiency is 95.6%; in Example 12, 15 wt.% urea + 0.5 wt.% H 2 O 2 , the denitration efficiency is 96.5%; in Example 13, 15 wt.% urea + 1 wt.% H 2 O 2 , the denitration efficiency is 97.2%.

[0138] Compared with Example 12, after adding the catalyst in Examples 14-16, NO xThe removal rate is further improved. Among them, after adding 1 g / L of catalyst in Example 14, the denitration efficiency is increased to 98.5%; after adding 3 g / L of catalyst in Example 15, the denitration efficiency is increased to 99.4%; after adding 5 g / L of catalyst in Example 16, the denitration efficiency is further increased to 99.9%.

[0139] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. To avoid unnecessary repetition, the present invention will not separately describe various possible combinations. However, these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A wet flue gas denitrification reaction method, characterized in that, the wet flue gas denitrification reaction method includes mixing the flue gas with air to form a mixed gas, and then feeding it into a denitrification reactor (200) filled with an absorbent solution for denitrification reaction.

2. The wet flue gas denitrification reaction method according to claim 1, characterized in that, the wet flue gas denitrification reaction method further includes mixing the mixed gas with the absorbent solution to form a mixed solution containing micro-nano bubbles, and then feeding the mixed solution containing micro-nano bubbles into the denitrification reactor (200) for denitrification reaction; preferably, the gas-liquid volume ratio of the mixed solution containing micro-nano bubbles is (1-3):

10.

3. The wet flue gas denitrification reaction method according to claim 1, characterized in that, the absorbent solution is a urea solution, hydrogen peroxide or a combination thereof; Wherein, when the absorption liquid contains hydrogen peroxide, a supported catalyst is loaded in the denitration reactor (200), and the active component of the supported catalyst is monodispersed Fe 3 O 4 spinel nanoparticles; Preferably, the average particle size of the Fe 3 O 4 spinel nanoparticles is 10-20 nm, preferably 12 nm; preferably, the loading amount of Fe in the supported catalyst is 10-30 wt.%, preferably 20 wt.%; preferably, the size of the supported catalyst is 80-120 mesh; Preferably, the support of the supported catalyst is activated carbon, carbon black, P25 titanium dioxide or α-Al 2 O 3 .

4. A wet flue gas denitrification reaction system for denitrifying flue gas, characterized in that, the wet flue gas denitrification reaction system includes a gas mixing unit (100) and a denitrification reactor (200), the gas mixing unit (100) is used for mixing air with the flue gas to form a mixed gas, and the denitrification reactor (200) is for the mixed gas to react with an absorbent solution capable of participating in the denitrification reaction.

5. The wet flue gas denitrification reaction system according to claim 4, characterized in that, the gas mixing unit (100) includes a gas mixing tank (110), the upper end of the gas mixing tank (110) is provided with a tank opening (111), a baffle (120) is arranged inside the gas mixing tank (110), the upper end of the baffle (120) extends to the tank opening (111) and can divide the tank opening (111) to form an air inlet (1111) and an air outlet (1112) on both sides of the baffle (120), and the lower end of the baffle (120) is adjacent to and spaced from the bottom of the gas mixing tank (110) to be used for dividing the interior of the gas mixing tank (110) into chambers on both sides of the baffle (120) and communicating at the bottom.

6. The wet flue gas denitrification reaction system according to claim 4, characterized in that, the wet flue gas denitrification reaction system further includes a gas dryer (300), the gas dryer (300) is connected to the gas outlet of the denitrification reactor (200) through an air outlet pipe (310), and the gas dryer (300) is arranged to be able to dry the gas generated by the denitrification reaction.

7. The wet flue gas denitrification reaction system according to claim 4, characterized in that, a stirring mechanism (210) is arranged in the denitrification reactor (200) to stir and mix the mixed gas and the absorbent solution participating in the denitrification reaction; and / or A jacket (220) is provided on the outer wall of the denitration reactor (200), and the jacket (220) is arranged to allow a heat exchange medium to circulate for controlling the temperature inside the denitration reactor (200).

8. The wet flue gas denitration reaction system according to any one of claims 4-7, characterized in that the wet flue gas denitration reaction system further includes a micro-nano bubble generator (400) disposed between the gas mixing unit (100) and the denitration reactor (200), and the micro-nano bubble generator (400) is arranged to mix the mixed gas with the absorbent liquid to form a mixed liquid containing micro-nano bubbles and feed it into the denitration reactor (200).

9. The wet flue gas denitration reaction system according to claim 8, characterized in that the micro-nano bubble generator (400) includes a high-pressure pump (410), a high-pressure gas dissolving tank (420) and a throttling gas release head (430) connected in sequence. The high-pressure pump (410) is used to pressurize and transport the mixed gas and the absorbent liquid into the high-pressure gas dissolving tank (420). The high-pressure gas dissolving tank (420) allows the mixed gas to dissolve in the absorbent liquid, and the throttling gas release head (430) is arranged to release the mixed gas dissolved in the absorbent liquid to form a mixed liquid containing the micro-nano bubbles; Preferably, the aperture of the throttling orifice of the throttling gas release head (430) is 2 mm - 15 mm.

10. The wet flue gas denitration reaction system according to claim 8, characterized in that the wet flue gas denitration reaction system further includes a liquid storage tank (500) for storing the absorbent liquid capable of participating in the denitration reaction, and a feed pipe (510) is provided between the liquid storage tank (500) and the micro-nano bubble generator (400) for feeding the absorbent liquid into the micro-nano bubble generator (400); Preferably, a return pipe (520) is provided between the denitration reactor (200) and the liquid storage tank (500), and a circulation pump (521) is provided on the return pipe (520) for transporting the absorbent liquid in the denitration reactor (200) back to the liquid storage tank (500).

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