Flue gas denitrification device and method

Abstract

This invention discloses a flue gas denitrification device and method. The device is suitable for SCR flue gas denitrification process of ultra-low temperature flue gas, and includes: multiple catalyst modules arranged in rows and columns on the cross-section of the flue, used to adsorb NO in the ultra-low temperature flue gas in a non-heated state. x The NH3 in the ammonia-air mixture, and the NO when heated to the flue gas denitrification window temperature. x The catalyst undergoes a denitrification reaction with NH3. A microwave assembly is positioned above the catalyst modules within the flue gas duct. This assembly includes a horizontally moving microwave generator for heating each catalyst module in a row or column, zone by zone. Once the heated zone has completed the denitrification reaction and the catalyst has been regenerated, the microwave generator moves to the next zone for heating. This invention, through the modular design of the catalyst and the built-in, movable microwave source, enables the catalyst modules to be heated zone by zone in a step-by-step manner, achieving rapid temperature rise of the catalyst module to the flue gas denitrification window temperature and quickly completing the catalyst regeneration process.

Description

Technical Field

[0001] This invention relates to the field of flue gas denitrification technology, and in particular to a device and method for ultra-low temperature flue gas denitrification. Background Technology

[0002] Nitrogen oxides (NOx) are among the major gaseous pollutants in the atmosphere. NOx not only harms human health but is also a significant contributor to environmental damage, acid rain, and photochemical smog. The primary sources of NOx are the combustion of fossil fuels, including coal-fired power plants, industrial boilers, and vehicle exhaust. NOx emission standards are constantly being tightened. Commonly used flue gas denitrification technologies include selective non-catalytic reduction (SNCR), selective catalytic reduction (SCR), and ozone oxidation absorption. Among these, SCR is the most widely used. The principle of SCR is as follows: an ammonia-based reducing agent is injected into the NOx-containing flue gas. Under the action of a catalyst, NH3 reacts with NOx in a catalytic reduction reaction, producing N2 and H2O as reaction products. The traditional SCR process operates at a reaction temperature of 300–450℃; within this temperature range, the catalyst activity is highest and its lifespan is longest.

[0003] Since flue gas typically contains SO2, SO3, O2, and water vapor, when there is excess ammonia in the reaction zone (ammonia escape), it reacts with SO3 to form ammonium salts. These ammonium salts (NH4HSO4) are liquid and viscous at temperatures between 180 and 240°C. They adsorb onto the catalyst surface, reducing catalyst activity. Simultaneously, they adhere to the heat exchange tubes of the economizer downstream of the SCR denitrification reactor, attracting dust from the flue gas and causing scaling, blockage, and corrosion of the heat exchange tubes, thus affecting the unit's operating cycle. NH4HSO4 deposition is a significant bottleneck restricting the application of SCR denitrification under low-temperature conditions.

[0004] Most existing technologies use heating the flue gas to raise its temperature to the denitrification reaction temperature window, thus requiring a heat exchanger. However, for ultra-low temperature flue gas, heating the flue gas to raise its temperature for conventional SCR reactions would result in very large equipment and excessive energy consumption during the heating process.

[0005] Existing technologies also include methods that use microwave sources to heat catalysts to achieve flue gas denitrification. For example, Chinese patent application CN105727745A discloses a microwave reaction system for SCR denitrification, comprising a reactor body, a gas distributor, a device insulation layer, a microwave generator, a temperature measuring unit, a catalyst module, and an ammonia injection system. The temperature of the catalyst itself can be adjusted by regulating the input power of the microwave generator. This reaction system and device have advantages such as wide applicability, energy saving and environmental protection, and simple operation, and possess good economic benefits and potential industrial application value. However, the microwave source in this type of solution is arranged on the outer wall of the reactor body and is statically set, resulting in poor denitrification effect for ultra-low temperature flue gas. Even if the number of microwave sources is increased to cover the microwave radiation range within the reactor, meeting the required flue gas denitrification window temperature in the flue, microwave energy consumption will increase significantly.

[0006] Therefore, there is an urgent need for a flue gas denitrification device and method that can rapidly heat the catalyst module in sections, enabling it to quickly reach the window temperature for flue gas denitrification even when facing ultra-low temperature flue gas, while significantly reducing energy consumption.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a flue gas denitrification device and method, which is particularly suitable for SCR denitrification process of ultra-low temperature flue gas. Through the modular design of the catalyst and the built-in and movable microwave source, the catalyst module can be heated in sections and gradually, so as to achieve rapid temperature rise of the catalyst module to the flue gas denitrification window temperature and quickly complete the catalyst regeneration process.

[0009] To achieve the above objectives, according to a first aspect of the present invention, a flue gas denitrification device is provided, suitable for SCR flue gas denitrification process of ultra-low temperature flue gas, comprising: multiple catalyst modules arranged in rows and columns fixedly disposed on the cross-section of the flue, for adsorbing NO in the ultra-low temperature flue gas in a non-heated state. x The NH3 in the ammonia-air mixture, and the NO when heated to the flue gas denitrification window temperature. x The catalyst undergoes a denitrification reaction with NH3; a microwave assembly is positioned above the catalyst modules within the flue; the microwave assembly includes a horizontally moving microwave generator for heating each catalyst module in a row or column by section, and after the heated area has completed the denitrification reaction and the catalyst has been regenerated, the microwave generator moves to the next area for heating.

[0010] Furthermore, in the above technical solution, the microwave component may also include: a metal enclosed cavity, which is a hollow cavity and is located directly below the microwave generator, for limiting the microwave radiation range to the area within the metal enclosed cavity; and a wave-transparent material plate, which is located at the bottom of the metal enclosed cavity, for supporting the microwave window constructed by the wave-transparent material.

[0011] Furthermore, in the above technical solution, rollers are provided on the side wall of the metal enclosed cavity. The rollers roll along the slide rail fixed in the flue, causing the microwave assembly to move horizontally as a whole.

[0012] Furthermore, in the above technical solution, the width of the metal enclosed cavity can be adapted to the width of the catalyst module.

[0013] Furthermore, in the above technical solution, the microwave component may be provided with a driving rod for connecting to a controller outside the flue and driving the microwave component to move as a whole. The driving rod may be fixed to the outer wall of the metal enclosed cavity.

[0014] Furthermore, in the above technical solution, the microwave windows constructed by the microwave-transparent material can be multiple and can be evenly spaced on the microwave-transparent material plate.

[0015] Furthermore, in the above technical solution, there can be multiple microwave generators, which can be evenly spaced on the top of the metal enclosed cavity.

[0016] Furthermore, in the above technical solution, the catalyst module may include: a metal wire mesh, which is a cubic structure formed by the sidewalls and bottom, with pillars at the four edges of the cube; the metal wire mesh is made of a non-transparent material. The catalyst is honeycomb-shaped or granular and fills the cubic structure.

[0017] Furthermore, in the above technical solution, the catalyst matrix can be made of a microwave absorbing material with adsorption function; the active component of the catalyst is immersed into the matrix pores.

[0018] Furthermore, in the above technical solution, the horizontal movement of the microwave component is preferably a reciprocating motion on the cross-section of the flue.

[0019] According to a second aspect of the present invention, a flue gas denitrification method is provided, using the apparatus of any one of the foregoing claims, comprising the following steps: A. mixing ultra-low temperature flue gas with an ammonia-air mixture in a flue; B. when the mixture flows through a catalyst module, NO in the mixture... x C. NH3 is adsorbed onto the catalyst matrix; D. The driving microwave component moves horizontally back and forth within the flue, causing microwave radiation to cover each row or column of catalyst modules step by step, and remains above each catalyst module for the same preset time, during which the heating of the catalyst module and NO are completed. x The denitrification reaction with NH3 and catalyst regeneration.

[0020] Furthermore, in the above technical solution, the ultra-low temperature flue gas of the present invention refers to flue gas with a temperature of 50 to 120°C, and the method is particularly suitable for flue gas with a temperature of 50 to 60°C.

[0021] Furthermore, in the above technical solution, the catalyst matrix filled in the catalyst module can be activated carbon; the active components of the catalyst can be oxides of V, Ti, W, and Mo, and the mass ratio of the active components, based on oxides, is as follows: V is 0.01 wt%, Ti is 99 wt%, W is 0.1 wt%, and Mo is 0.02 wt%.

[0022] Furthermore, in the above technical solution, the maximum power of each microwave generator in the microwave assembly can be 6×10⁻⁶. 5 W / m 3 The preset time in step C is preferably 2s to 3s; the heating temperature of the catalyst module is preferably controlled at 200 to 450℃.

[0023] Furthermore, in the above technical solution, the catalyst module can be arranged in multiple layers in the height direction, and the multi-layer catalyst module can construct a catalyst bed, while multiple catalyst beds can be arranged in the flue.

[0024] Furthermore, in the above technical solution, the catalyst bed temperature can be adjusted according to the flue gas composition: when the SO2 content in the flue gas is low, the catalyst bed temperature can be controlled below 300℃; when the SO2 content in the flue gas is high, the catalyst bed temperature can be controlled between 320℃ and 450℃.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) This invention modularizes the filling of the denitrification catalyst and heats the catalyst module until the denitrification reaction temperature window is reached. Because microwave heating is used and each catalyst module is heated in sections, the regional heating speed is fast and the time is short. It has the advantages of simple process, low energy consumption and wide applicability.

[0027] 2) This invention is particularly applicable to the SCR flue gas denitrification process for ultra-low temperature flue gas, where ultra-low temperature flue gas refers to flue gas with a temperature of 50-120℃. Tests have shown that the device has a better denitrification effect on flue gas with a temperature of 50-60℃. The device and method of this invention can also be applied to flue gas with higher temperatures, and can be applied to flue gas with a temperature of 50℃-450℃ to achieve the desired denitrification effect.

[0028] 3) This invention only requires heating the catalyst, significantly reducing energy consumption compared to heating flue gas. Through the modular design of the catalyst and the movable microwave components, heating of modules row by row or column by column can be achieved. A smaller number of microwave sources are needed to centrally heat each module, resulting in a more concentrated microwave radiation range that effectively shortens the regional heating time. The heated module can instantly reach the denitrification window temperature, allowing NO adsorbed on the catalyst matrix to dissolve within a very short time. x It undergoes a denitrification reaction with NH3, and the gas after the reaction is rapidly released and moved downwards, thereby simultaneously completing the catalyst regeneration of this module;

[0029] 4) In this invention, other catalyst modules besides the heated catalyst module can simultaneously process NO in the flue gas. x The adsorption of NH3 is followed by a heating-denitration reaction-catalyst regeneration process when the microwave component moves to the region; the horizontal reciprocating movement of the microwave component enables each catalyst module to periodically perform the complete process of adsorption-heating-reaction-regeneration.

[0030] 5) The catalyst matrix of the present invention is made of microwave absorbing material, and the microwave source has high heating efficiency for it, so that the energy required to heat the flue gas is very small to reach the required denitrification window temperature, thereby achieving the effect of energy saving.

[0031] 6) The present invention, through the structural arrangement of the microwave component, can form a closed space when it moves above a certain catalyst module, preventing flue gas from flowing through it. After the denitrification reaction is completed, the catalyst module can be regenerated. The microwave component continues to move above adjacent catalyst modules, which can regenerate the catalyst one by one, resulting in a more complete denitrification reaction and higher catalyst regeneration efficiency.

[0032] 7) This invention can control the movement of the microwave component in real time by measuring the temperature of the catalyst module area. That is, the residence time of the microwave component on each module can be controlled according to the heating temperature requirements and the composition of the flue gas. The catalyst bed temperature can be adjusted according to the composition of the flue gas: when the SO2 content in the flue gas is low, the catalyst bed temperature is controlled below 300°C; when the SO2 content in the flue gas is high, the catalyst bed temperature is controlled between 320°C and 450°C (at this temperature, the ammonium salt generated can decompose, and the catalyst activity is guaranteed). Therefore, this invention has no restrictions on the composition of the flue gas.

[0033] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the arrangement of the flue gas denitrification device of the present invention in the flue.

[0035] Figure 2 This is a top view of the first embodiment of the flue gas denitrification device of the present invention in the flue.

[0036] Figure 3 This is a side view of the flue gas denitrification device of the present invention in the flue.

[0037] Figure 4 is a schematic diagram of the microwave component structure in the flue gas denitrification device of the present invention (wherein) Figure 4-A This is a cross-sectional view of the internal structure. Figure 4-B for Figure 4-A Side view; Figure 4-C for Figure 4-A Top view; Figure 4-D for Figure 4-A (Schematic diagram of AA-direction section).

[0038] Figure 5 This is a top view of the second embodiment of the flue gas denitrification device of the present invention in the flue.

[0039] Figure 6 This is a side view of the flue gas denitrification device of the present invention in a flue.

[0040] Figure 7 This is a top view schematic diagram of the catalyst module in the flue gas denitrification device of the present invention.

[0041] Explanation of key figure labels:

[0042] 1-Catalyst module, 11-Metal wire mesh, 12-Solid catalyst, 13-Column, 2-Microwave assembly, 21-Microwave generator, 22-Metal enclosed cavity, 23-Roller, 24-Wave-transparent material plate, 241-Microwave window, 25-Drive rod, 3-Ammonia injection element, 4-Mixed ammonia element, 100-Flue, 101-Slide rail. Detailed Implementation

[0043] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0044] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0045] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0046] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0047] The technical concept of this invention is to modularize the filling of the denitrification catalyst and heat the catalyst modules until the denitrification reaction temperature window is reached. Because microwave heating is used and each catalyst module is heated in sections, the regional heating speed is fast and the time is short, which has the advantages of simple process, low energy consumption and wide applicability.

[0048] like Figures 1 to 3 As shown, this invention provides a flue gas denitrification device, particularly suitable for SCR flue gas denitrification processes using ultra-low temperature flue gas. The ultra-low temperature flue gas of this invention refers to flue gas with a temperature of 50–120°C. This device is more effective at denitrifying flue gas with a temperature of 50–60°C. The device is installed within a flue duct 100. An ammonia injection element 3 and an ammonia mixing element 4 are located upstream of the device. An ammonia-air mixture enters the ammonia injection element 3 radially from the flue duct 100 and is ejected in the same direction as the flue gas. The ejected ammonia-air mixture mixes with the flue gas in the ammonia mixing element 4, and the mixture enters the flue gas denitrification device of this invention. The device includes at least a catalyst module 1 and a microwave component 2. Multiple catalyst modules 1 are arranged in rows and columns fixedly on the cross-section of the flue duct 100 (fully covering the cross-section of the flue duct), used to adsorb NO from the ultra-low temperature flue gas in a non-heated state. x The NH3 in the ammonia-air mixture, and the NO when heated to the flue gas denitrification window temperature. x A denitrification reaction occurs with NH3. Microwave assembly 2 is located within flue 100 and above catalyst module 1. Microwave assembly 2 includes a horizontally movable microwave generator 21 (reference). Figures 2 to 6The microwave generator is used to heat each catalyst module 1 in a row or column by a section. After the heated area has completed the denitrification reaction and the catalyst has been regenerated, the microwave generator moves to the next area for heating.

[0049] The device of this invention adopts the above-described technical solution. Through the modular design of the catalyst and the use of movable microwave components to heat the modules row by row or column by column, a smaller number of microwave sources can be used to heat each module centrally. The microwave radiation range is more concentrated, which can effectively shorten the regional heating time. The heated module can reach the denitrification window temperature instantly. Therefore, this module can remove NO adsorbed on the catalyst matrix in a very short time. x The catalyst undergoes a denitrification reaction with NH3, and the resulting gases (N2 and H2O) rapidly escape and descend, thus simultaneously regenerating the catalyst in this module. In areas outside the heated catalyst module (i.e., other catalyst modules), the denitrification of NO in the flue gas also occurs simultaneously. x The adsorption of NH3 is followed by a heating-denitrification reaction-catalyst regeneration process while the microwave component moves to the designated area. The horizontal movement of the microwave component is preferably a reciprocating motion across the flue gas duct cross-section, enabling each catalyst module to periodically complete the entire process of adsorption-heating-reaction-regeneration.

[0050] Further as Figures 4-A to 4-D As shown, preferably but not limitingly, the microwave assembly 2 of the present invention may include, in addition to the microwave generator 21, a metal enclosed cavity 22, a roller 23, a wave-transparent material plate 24, and a drive rod 25, etc. The metal enclosed cavity 22 is a hollow cavity and is located directly below the microwave generator 21, used to confine the microwave radiation range within the area of ​​the metal enclosed cavity. The wave-transparent material plate 24 is located at the bottom of the metal enclosed cavity 22, used to support the microwave window 241 constructed of the wave-transparent material (see reference). Figure 4-D The number of microwave generators 21 can be selected according to the diameter of the flue 100, the size of the catalyst module, and the temperature of the flue gas to be denitrified. Multiple microwave generators 21 can be evenly spaced on the top of the metal enclosed cavity 22. Four microwave generators 21 are arranged in Figure 4. In order to realize the horizontal reciprocating movement of the microwave component 2, the present invention adopts a combination of rollers and slide rails. That is, rollers 23 are provided on the side wall of the metal enclosed cavity 22. The rollers 23 can move along the slide rail 101 fixed in the flue (see reference). Figure 2 The rolling motion causes the microwave assembly 2 to move horizontally as a whole. To ensure better microwave radiation coverage of each catalyst module 1, the width of the metal enclosure 22 can be adapted to the width of the catalyst module (preferably both are the same, forming row-by-row or column-by-column full coverage of the modules). Figure 2 In the first embodiment shown, two microwave components 2 are provided, each covering four rows of catalyst modules. Figure 5In the second embodiment shown, four microwave components 2 are provided, each covering two rows of catalyst modules. The present invention can select the appropriate components as needed. Further, as... Figure 4-D As shown, the microwave windows 241 constructed from the microwave-transparent material are multiple and evenly spaced on the microwave-transparent material plate 24, ensuring that microwave radiation can effectively cover the catalyst module 1 below. With the above structural arrangement, when the microwave component 2 moves above a certain catalyst module 1, it can form a closed space, preventing flue gas from flowing through. After the denitrification reaction is completed, the catalyst module can be regenerated. The microwave component 2 can then move above adjacent catalyst modules 1 to regenerate the catalysts one by one.

[0051] Furthermore, the microwave assembly 2 is equipped with a drive rod 25 for connecting to a controller (not shown in the figure) outside the flue 100 and driving the microwave assembly 2 to move as a whole. The drive rod 25 can be fixed to the outer wall of the metal enclosed cavity 22. A temperature sensor (not shown in the figure) can be installed in the bed where the catalyst module is located. By measuring the temperature of the catalyst module area in real time, the drive rod 25 can be controlled in real time, thereby driving the microwave assembly 2 to control the residence time on each module according to the heating temperature requirements and the composition of the flue gas.

[0052] Further as Figure 7 As shown, preferably but not limitingly, the catalyst module 1 may include a metal mesh 11 and a solid catalyst 12. The metal mesh 11 is a cubic structure formed by sidewalls and a bottom (without mesh at the top), with posts 13 at the four edges of the cube. The metal mesh 11 is made of a non-transparent material. The catalyst 12 may be honeycomb-shaped or granular and filled within the cubic structure. The catalyst matrix may be made of a material with adsorption function (for adsorbing NO). x It is made of microwave absorbing material (NH3) (which can improve heating efficiency); the active component of the catalyst is immersed in the matrix pores.

[0053] The present invention also provides a flue gas denitrification method, which uses the aforementioned apparatus and includes the following steps:

[0054] Step S101: Mix the ultra-low temperature flue gas with the ammonia-air mixture in the flue (the temperature of the ultra-low temperature flue gas can be 50-120℃).

[0055] In step S102, when the mixed gas stream passes through catalyst module 1, the NO in the mixed gas... xNH3 is adsorbed onto the catalyst matrix. Specifically, the catalyst matrix filled in catalyst module 1 can be activated carbon, etc.; the active components of the catalyst can be oxides of V, Ti, W, and Mo, and the mass ratio of the active components, based on oxides, is as follows: V is 0.01 wt%, Ti is 99 wt%, W is 0.1 wt%, and Mo is 0.02 wt%.

[0056] Step S103: Drive the microwave component 2 to reciprocate horizontally within the flue 100, so that microwave radiation (the maximum power of the microwave generator is preferably 6×10) is generated. 5 W / m 3 The catalyst module 1 is gradually covered in each row or column, and remains above each catalyst module 1 for the same preset time (preferably 2s to 3s). During this preset time, the heating and NO removal of the catalyst module are completed. x The catalyst undergoes a denitrification reaction with NH3 and undergoes catalyst regeneration. The heating temperature of the catalyst module can be controlled between 200 and 450°C.

[0057] Furthermore, preferably but not limitingly, the catalyst module 1 can be configured with multiple layers in the height direction. These multiple catalyst modules can construct a catalyst bed, and multiple catalyst beds can be arranged within the flue gas duct according to process requirements. The catalyst bed temperature can be adjusted according to the flue gas composition: when the SO2 content in the flue gas is low, the catalyst bed temperature is controlled below 300℃; when the SO2 content in the flue gas is high, the catalyst bed temperature is controlled between 320℃ and 450℃.

[0058] The following two specific embodiments will be used to illustrate the details:

[0059] Example 1

[0060] Flue gas to be denitrified: Flue gas volume is 55,000 Nm³ 3 / h, temperature 60℃, pressure 10kPa, NO x Concentration of 600 mg / Nm 3 SO2 concentration is 100 mg / Nm 3 The SO3 concentration is 10 mg / Nm³. 3 The dust content is 200 mg / Nm³. 3 .

[0061] NO x The emission standard is 100 mg / Nm³. 3 The ammonia-air mixture flow rate used is 800 Nm³. 3 / h, of which ammonia gas accounts for 3%. The flue cross-section is 1240×2480mm.

[0062] In this embodiment, a honeycomb carbon-based denitration catalyst is used. The active components of the catalyst are oxides of V, Ti, W, and Mo. The mass ratio of the active components, based on oxides, is as follows: V 0.01 wt%, Ti 99 wt%, W 0.1 wt%, and Mo 0.02 wt%. The catalyst module consists of five layers, each 150 mm × 150 mm in size, with a height of 200 mm. Each layer contains 128 catalyst modules.

[0063] Ammonia-air mixture is injected into the flue gas duct by an ammonia injection element. After mixing with the 60°C flue gas through the ammonia mixing element, it enters the SCR flue gas denitrification device of this invention. The device is equipped with two microwave components, each with four microwave generators, and a maximum microwave power of 6 × 10⁻⁶. 5 W / m 3 The temperature of the heated catalyst module is controlled at 250℃. The microwave assembly stays above the catalyst module for 2 seconds before moving to an adjacent catalyst module. The microwave assembly moves horizontally back and forth, cyclically heating each catalyst module. After the catalyst modules are regenerated, the NO in the emitted purified flue gas... x Content less than 50mg / Nm 3 It meets emission requirements.

[0064] Example 2

[0065] Flue gas to be denitrified: Flue gas volume is 35,000 Nm³ 3 / h, temperature 120℃, pressure 10kPa, NO x Concentration of 200 mg / Nm 3 The SO2 concentration is 1000 mg / Nm³. 3 The SO3 concentration is 20 mg / Nm³. 3 The dust content is 200 mg / Nm³. 3 .

[0066] NO x The emission standard is 50 mg / Nm³. 3 The ammonia-air mixture flow rate used was 170 Nm³. 3 / h, of which ammonia gas accounts for 3%. The flue cross-section is 1240×2480mm.

[0067] In this embodiment, a granular carbon-based denitration catalyst is used. The active components of the catalyst particles are oxides of V, Ti, W, and Mo. The mass ratios of the active components, based on oxides, are as follows: V 0.01 wt%, Ti 99 wt%, W 0.1 wt%, and Mo 0.02 wt%. The catalyst is spherical with a particle size of 5 mm and a bulk density of 0.68 g / cm³. 3Specific surface area is 80m² 2 / g, pore volume is 0.57cm 3 / g. The granular catalyst module consists of a wire mesh, catalyst particles, and a column. The cross-sectional dimensions are 150mm × 150mm, and the module height is 150mm. It is arranged in four layers, with 128 catalyst modules in each layer.

[0068] Ammonia-air mixture is injected into the flue gas duct by an ammonia injection element. After mixing with the 120°C flue gas through the ammonia mixing element, it enters the SCR flue gas denitrification device of this invention. The device is equipped with four microwave components, each with two microwave generators, and a maximum microwave power of 6 × 10⁻⁶. 5 W / m 3 The microwave generator is the same as in Example 1, and the heating method is also the same. The temperature of the catalyst module being heated is controlled at 350°C. The microwave component stays above the catalyst module for 2 seconds and then moves to an adjacent catalyst module. The microwave component moves horizontally back and forth, cyclically heating each catalyst module. After the catalyst module is regenerated, the NO in the emitted purified flue gas... x Content less than 50mg / Nm 3 It meets emission requirements.

[0069] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A flue gas denitrification device, characterized in that, An SCR flue gas denitrification process suitable for ultra-low temperature flue gas, where ultra-low temperature flue gas refers to flue gas with a temperature of 50~120℃, the device includes: Multiple catalyst modules, arranged in rows and columns, are fixedly installed on the cross-section of the flue gas to adsorb NO from the ultra-low temperature flue gas in a non-heated state. x The NH3 in the ammonia-air mixture, and the NO when heated to the flue gas denitrification window temperature. x The catalyst module includes: a metal wire mesh, which is a cubic structure enclosed by sidewalls and bottom, with pillars at the four edges of the cube; the metal wire mesh is made of a non-transparent material; and a catalyst, which is honeycomb or granular and filled in the cubic structure. A microwave assembly is disposed above the catalyst module within the flue. This microwave assembly includes a horizontally moving microwave generator for heating each catalyst module in a row or column by zone. After the heated zone completes the denitrification reaction and the catalyst is regenerated, the microwave generator moves to the next zone for heating. The microwave assembly also includes a metal enclosed cavity, which is a hollow cavity disposed directly below the microwave generator, for limiting the microwave radiation range to the area within the metal enclosed cavity; and a microwave-transparent material plate disposed at the bottom of the metal enclosed cavity for supporting the microwave window constructed from the microwave-transparent material.

2. The flue gas denitrification device according to claim 1, characterized in that, The sidewall of the metal enclosed cavity is equipped with rollers, which roll along a slide rail fixed in the flue, causing the microwave assembly to move horizontally as a whole.

3. The flue gas denitrification device according to claim 1, characterized in that, The width of the metal enclosed cavity is adapted to the width of the catalyst module.

4. The flue gas denitrification device according to claim 2, characterized in that, The microwave assembly is equipped with a drive rod for connecting to a controller outside the flue and driving the microwave assembly to move as a whole. The drive rod is fixed to the outer wall of the metal enclosed cavity.

5. The flue gas denitrification device according to claim 1, characterized in that, The microwave-transparent material has multiple microwave windows that are evenly spaced on the microwave-transparent material plate.

6. The flue gas denitrification device according to claim 1, characterized in that, The number of microwave generators is multiple, and they are evenly spaced at the top of the metal enclosed cavity.

7. The flue gas denitrification device according to claim 1, characterized in that, The catalyst matrix is ​​made of a microwave absorbing material with adsorption function; the active component of the catalyst is immersed in the matrix pores.

8. The flue gas denitrification device according to claim 1, characterized in that, The horizontal movement is a reciprocating motion on the cross-section of the flue.

9. A method for flue gas denitrification, characterized in that, Using the apparatus as described in any one of claims 1 to 8, the method includes the following steps: A. Mix ultra-low temperature flue gas with ammonia-air mixture in the flue; B. When the mixed gas flows through the catalyst module, the NO in the mixed gas... x NH3 is adsorbed onto the catalyst matrix; C. Drive the microwave component to move horizontally back and forth within the flue, so that microwave radiation gradually covers each row or column of catalyst modules, and stays above each catalyst module for the same preset time, during which the heating of the catalyst module and the NO are completed. x The denitrification reaction with NH3 and catalyst regeneration.

10. The flue gas denitrification method according to claim 9, characterized in that, The catalyst matrix filled in the catalyst module is made of activated carbon.

11. The flue gas denitrification method according to claim 9, characterized in that, The maximum power of each microwave generator in the microwave assembly is 6 × 10⁻⁶. 5 W / m 3 The preset time in step C is 2s~3s; the heating temperature of the catalyst module is controlled at 200~450℃.

12. The flue gas denitrification method according to claim 11, characterized in that, The catalyst module is arranged in multiple layers in the height direction, and the multi-layer catalyst module forms a catalyst bed. Multiple catalyst beds are arranged in the flue.

13. The flue gas denitrification method according to claim 12, characterized in that, The catalyst bed temperature is adjusted according to the flue gas composition: when the SO2 content in the flue gas is low, the catalyst bed temperature is controlled below 300℃; when the SO2 content in the flue gas is high, the catalyst bed temperature is controlled between 320 and 450℃.

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