Ammonia spraying grid and SCR (Selective Catalytic Reduction) denitration device applied to ultralow-temperature flue gas

Abstract

The utility model relates to an ammonia injection grid and applied to the SCR denitration device of ultralow temperature flue gas, ammonia injection grid includes coaming, first ammonia supply pipe, second ammonia supply pipe and nozzle, coaming is the tubular structure of two open ends, the first ammonia supply pipe is installed in the coaming inner cavity and is perpendicular to the central axis of coaming, the second ammonia supply pipe is installed in the coaming inner cavity and is perpendicular to the central axis of the coaming, the second ammonia supply pipe is installed in the coaming inner cavity and is perpendicular to the central axis of the coaming. A plurality of nozzles are arranged on the first ammonia supply pipe, the spraying directions of the nozzles face the open side of one axial end of the coaming, the second ammonia supply pipe is connected and communicated with the first ammonia supply pipe, and one end of the second ammonia supply pipe extends to the outer side of the coaming; the distance between any two adjacent nozzles is not larger than 200 mm. According to the ammonia spraying grid, the first ammonia supply pipe and the second ammonia supply pipe are arranged, the nozzles on the first ammonia supply pipe and the second ammonia supply pipe are tightly designed, and the flue gas passes through the efficient and low-resistance ammonia spraying grid, so that NOx in the flue gas can be effectively removed, and the flue gas of a boiler can be discharged after reaching the standard.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection technology, specifically to an ammonia injection grid and an SCR denitrification device for ultra-low temperature (below 180°C) flue gas. Background Technology

[0002] Selective catalytic reduction (NH3-SCR) technology using NH3 as a reducing agent is currently the most effective method for industrial flue gas denitrification. Most commercially available catalysts are V2O5-WO3(MoO3) / TiO2 catalysts, with operating temperatures generally ranging from 300℃ to 400℃. To meet this temperature window and eliminate the need for external heating, SCR denitrification units are typically installed before dust removal and desulfurization units, making them suitable for new construction projects.

[0003] Thanks to years of continuous research, SCR denitrification technology and its catalyst system have been developed with good application effects in the range of 180 to 420℃. However, for low-temperature flue gas in industries such as steel, coking, small and medium-sized coal-fired (power generation) boilers and other industries, the flue gas still needs to be heated before it can react, which will greatly increase the cost of denitrification.

[0004] Currently, SCR denitrification treatment of "clean" flue gas after "dust removal and desulfurization" can effectively alleviate the bottleneck problem of catalyst poisoning caused by the complexity of flue gas composition. At the same time, some industries have very "clean" flue gas (low dust and low sulfur). Therefore, the SCR denitrification method at a lower temperature is of great significance in the field of ultra-low temperature (below 180℃) flue gas.

[0005] The use of ultra-low temperature NH3-SCR technology makes it easy to match with existing industrial furnace systems, avoids the energy consumption of flue gas preheating, and is easy to promote. Utility Model Content

[0006] In order to solve one or more technical problems existing in the prior art, this utility model provides an ammonia injection grid and an SCR denitrification device for ultra-low temperature flue gas.

[0007] The technical solution of this utility model to solve the above-mentioned technical problems is as follows: An ammonia spraying grid includes a surrounding plate, a first ammonia supply pipe, a second ammonia supply pipe, and nozzles. The surrounding plate is a cylindrical structure with open ends. The first ammonia supply pipe is installed in the inner cavity of the surrounding plate and is perpendicular to the central axis of the surrounding plate. The first ammonia supply pipe is provided with multiple nozzles. The spraying direction of the nozzles is arranged towards the open end of the surrounding plate along its axial direction. The second ammonia supply pipe is connected and communicates with the first ammonia supply pipe. One end of the second ammonia supply pipe extends to the outside of the surrounding plate. The distance between any two adjacent nozzles is no more than 200mm.

[0008] The beneficial effects of this utility model are: the ammonia injection grid of this utility model, by setting a first ammonia supply pipe and a second ammonia supply pipe, and designing the nozzles on them tightly, allows the flue gas to pass through the high-efficiency and low-resistance ammonia injection grid, which can effectively remove NOx from the flue gas and achieve boiler flue gas emission standards.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, the inner cavity of the enclosure is provided with multiple independently spaced first ammonia supply pipes, and each first ammonia supply pipe is connected to a second ammonia supply pipe.

[0011] The beneficial effect of adopting the above-mentioned further scheme is that by setting up multiple first ammonia supply pipes, each of which is connected to a second ammonia supply pipe, it is possible to achieve individual ammonia supply for each first ammonia supply pipe, ensuring the independent and stable operation of each first ammonia supply pipe and its nozzle.

[0012] Furthermore, the first ammonia supply pipe has an S-shaped bend structure, and the second ammonia supply pipe has an L-shaped structure, a straight structure, or a multi-segment bend structure.

[0013] The beneficial effect of adopting the above-mentioned further solution is that the first ammonia supply pipe with an S-shaped bending structure makes it convenient to set multiple first ammonia supply pipes inside the enclosure without interfering with each other.

[0014] Furthermore, the enclosure has a rectangular cylindrical structure, and multiple rows of first ammonia supply pipes are provided in the inner cavity of the enclosure.

[0015] Furthermore, the second ammonia supply pipe is arranged perpendicular to the central axis of the enclosure, one end of the second ammonia supply pipe is connected to and communicates with the first ammonia supply pipe, and the other end of the second ammonia supply pipe passes through the enclosure and is fixedly connected to the outer wall of the enclosure through the first connector.

[0016] The beneficial effect of adopting the above-mentioned further solution is that the second ammonia supply pipe is connected and fixed to the outer wall of the enclosure, which facilitates the supply of ammonia source from the side wall of the enclosure.

[0017] Furthermore, a connecting beam is provided in the inner cavity of the enclosure, and the first ammonia supply pipe is installed on the connecting beam through a second connector.

[0018] The beneficial effect of adopting the above-mentioned further solution is that by setting a connecting beam inside the enclosure, it is convenient to connect and fix the first ammonia supply pipe.

[0019] Furthermore, the connecting beam is arranged perpendicular to the central axis of the enclosure, and a support rod is vertically fixed on the connecting beam. Part or all of the second ammonia supply pipes are installed on the corresponding support rods through a third connector.

[0020] The beneficial effect of adopting the above-mentioned further solution is that by setting a support rod, it is convenient to connect and fix the second ammonia supply pipe.

[0021] Furthermore, the nozzle includes an injection pipe, a connecting rod, and a static mixer. One end of the injection pipe is vertically fixed to the first ammonia supply pipe, and the outer wall of the other end of the injection pipe is connected and fixed to the static mixer through the connecting rod. An injection interval is reserved between the static mixer and the other end of the injection pipe.

[0022] The beneficial effect of adopting the above-mentioned further scheme is that by setting the injection pipes and static mixers at intervals, it is convenient to diffuse the ammonia-air mixture sprayed from the injection pipes, so that the ammonia-air mixture can be mixed evenly with the flue gas in a short time after the ammonia injection grid.

[0023] An SCR denitrification device for ultra-low temperature flue gas includes an ammonia injection grid as described above, and a denitrification reactor. The denitrification reactor is provided with a catalyst bed and a burner. The burner is located below the catalyst bed, and the ammonia injection grid is disposed in the denitrification reactor and located between the catalyst bed and the burner.

[0024] The beneficial effects of this utility model are: the SCR denitrification device of this utility model, by setting a burner, can control the water vapor content in the flue gas to be less than 20%. When used in combination with the ammonia injection grid, it can ensure that the overall activity of the catalyst is limited in the low temperature flue gas environment, and restore the catalyst activity by short-term heating of the burner, thus avoiding the reduction of catalyst activity due to water vapor occupying the catalyst active sites.

[0025] Furthermore, the burner is connected to a fuel gas pipeline and a combustion air pipeline.

[0026] The beneficial effect of adopting the above-mentioned further scheme is that the combustion air duct provides stable air supply to the denitrification reactor, which can ensure that the oxygen content in the boiler flue gas is not less than 1%.

[0027] Under ultra-low temperature conditions, water vapor in flue gas can occupy the active sites of the catalyst and affect the catalyst's ability to adsorb nitrogen oxides. To solve this problem, this invention proposes to control the water vapor content in the flue gas to maintain the reasonable activity range of the catalyst or to reserve a short-term heating measure for the flue gas to restore the catalyst activity. Specifically, the burner is used to control the water vapor content in the flue gas.

[0028] Under ultra-low temperature conditions, the activity of low-temperature catalysts is limited, and the oxygen content in the flue gas needs to be controlled within a reasonable range to ensure smooth denitrification reaction. This invention proposes controlling the reasonable gas distribution of the boiler burner and setting up combustion air ducts, ensuring that the oxygen content in the flue gas is not lower than 1%. Under ultra-low temperature conditions, vanadium-titanium-based denitrification catalysts have low activity, making it difficult to achieve high denitrification efficiency. This invention uses transition metal and rare earth metal catalysts, which have higher activity at low temperatures, effectively reducing the volume of denitrification catalysts used in low-temperature flue gas environments. Under ultra-low temperature conditions, the activity of denitrification catalysts is relatively low, requiring higher ammonia / flue gas mixing uniformity to ensure ammonia slip concentration. This invention uses a more densely arranged ammonia injection grid to achieve self-uniform ammonia injection. This invention can effectively improve the denitrification efficiency and operational stability of SCR denitrification systems under ultra-low temperature conditions. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the main structure of the ammonia injection grid of this utility model;

[0030] Figure 2 for Figure 1 Schematic diagram of the cross-sectional structure of AA;

[0031] Figure 3 This is a cross-sectional view of the nozzle of this utility model;

[0032] Figure 4 This is a top view of the static mixer of this utility model;

[0033] Figure 5 This is a schematic diagram of the connection between the ammonia injection grid and the ammonia supply main pipe of this utility model;

[0034] Figure 6 This is a schematic diagram of the SCR denitrification device of this utility model applied to ultra-low temperature flue gas.

[0035] The attached diagram lists the components represented by each number as follows:

[0036] 1. Ammonia injection grille;

[0037] 2. Enclosure panel; 21. Connecting beam; 22. Support rod; 23. First connector; 24. Second connector; 25. Third connector;

[0038] 3. First ammonia supply pipe; 4. Second ammonia supply pipe; 41. Main ammonia supply pipe;

[0039] 5. Nozzle; 51. Injection pipe; 52. Connecting rod; 53. Static mixer;

[0040] 6. Denitrification reactor; 61. Catalyst bed; 62. Burner; 63. Fuel gas pipeline; 64. Combustion air pipeline; 65. Combustion air fan. Detailed Implementation

[0041] The principles and features of this utility model are described below. The examples given are only for explaining this utility model and are not intended to limit the scope of this utility model.

[0042] Example 1

[0043] like Figures 1-5 As shown, an ammonia-spraying grid 1 in this embodiment includes a surrounding plate 2, a first ammonia supply pipe 3, a second ammonia supply pipe 4, and nozzles 5. The surrounding plate 2 is a cylindrical structure with open ends. The first ammonia supply pipe 3 is installed in the inner cavity of the surrounding plate 2 and is perpendicular to the central axis of the surrounding plate 2. The first ammonia supply pipe 3 is provided with a plurality of nozzles 5. The spraying direction of the nozzles 5 is arranged towards the open end of the surrounding plate 2 in the axial direction. The second ammonia supply pipe 4 is connected to and communicates with the first ammonia supply pipe 3. One end of the second ammonia supply pipe 4 extends to the outside of the surrounding plate 2. The distance between any two adjacent nozzles 5 is no greater than 200 mm.

[0044] In this embodiment, the ammonia injection grid, by setting a first ammonia supply pipe and a second ammonia supply pipe and designing the nozzles on them tightly, allows the flue gas to pass through the high-efficiency, low-resistance ammonia injection grid, which can effectively remove NOx from the flue gas and achieve boiler flue gas emission standards.

[0045] Example 2

[0046] Regarding the structure and arrangement of the first ammonia supply pipe 3 and the second ammonia supply pipe 4, this embodiment provides the following optional solutions.

[0047] like Figure 1 and Figure 2 As shown, the inner cavity of the enclosure 2 is provided with multiple independently spaced first ammonia supply pipes 3, and each first ammonia supply pipe 3 is connected to a second ammonia supply pipe 4. By setting multiple first ammonia supply pipes, each first ammonia supply pipe is connected to a second ammonia supply pipe, so that each first ammonia supply pipe can supply ammonia independently, ensuring the independent and stable operation of each first ammonia supply pipe and its nozzle.

[0048] like Figure 1 and Figure 2 As shown, the first ammonia supply pipe 3 has an S-shaped bend structure, and the second ammonia supply pipe 4 has an L-shaped structure, a straight structure, or a multi-segment bend structure. The S-shaped bend structure of the first ammonia supply pipe facilitates the installation of multiple first ammonia supply pipes within the enclosure without interference between them.

[0049] like Figure 1 and Figure 2 As shown, the enclosure 2 has a rectangular cylindrical structure, and multiple rows of first ammonia supply pipes 3 are provided in the inner cavity of the enclosure 2.

[0050] like Figure 1 and Figure 2 As shown, the second ammonia supply pipe 4 is arranged perpendicular to the central axis of the enclosure 2. One end of the second ammonia supply pipe 4 is connected and communicates with the first ammonia supply pipe 3, specifically at the middle position of the first ammonia supply pipe 3. The other end of the second ammonia supply pipe 4 passes through the enclosure 2 and is fixedly connected to the outer wall of the enclosure 2 via the first connector 23. Connecting and fixing the second ammonia supply pipe to the outer wall of the enclosure facilitates the supply of ammonia from the side wall of the enclosure.

[0051] Specifically, the first connector 23 can be a sleeve fixed on the enclosure 2, through which the other end of the second ammonia supply pipe 4 can be clamped and fixed.

[0052] Example 3

[0053] Regarding the connection method of the first ammonia supply pipe 3 and the second ammonia supply pipe 4, options are available, such as... Figure 2 As shown, a connecting beam 21 is provided in the inner cavity of the enclosure 2, and the first ammonia supply pipe 3 is installed on the connecting beam 21 through a second connector 24. The connecting beam inside the enclosure facilitates the connection and fixation of the first ammonia supply pipe. The connecting beam 21 can extend perpendicularly to the central axis of the enclosure 2.

[0054] like Figure 2 As shown, the connecting beam 21 is arranged perpendicular to the central axis of the enclosure 2, and a support rod 22 is vertically fixed on the connecting beam 21. Part or all of the second ammonia supply pipe 4 is installed on the corresponding support rod 22 via a third connector 25. The support rod facilitates the connection and fixation of the second ammonia supply pipe. The support rod 22 can be arranged parallel to the central axis of the enclosure 2.

[0055] Specifically, the second connector 24 can be a structure with a U-bolt and nut, which can clamp the first ammonia supply pipe 3 and pass through the connecting beam 21, and then be tightened and fixed by the nut. The third connector 25 can also be a structure with a U-bolt and nut, to achieve clamping and fixing of the second ammonia supply pipe 4.

[0056] Example 4

[0057] This embodiment provides a preferred nozzle structure, such as Figure 3 and Figure 4 As shown, the nozzle 5 includes an injection pipe 51, a connecting rod 52, and a static mixer 53. One end of the injection pipe 51 is vertically fixed to the first ammonia supply pipe 3, and the outer wall of the other end of the injection pipe 51 is connected and fixed to the static mixer 53 via the connecting rod 52. A spray interval is reserved between the static mixer 53 and the other end of the injection pipe 51. By setting the injection pipe and static mixer at intervals, the ammonia-air mixture sprayed from the injection pipe is easily diffused, so that the ammonia-air mixture mixes evenly with the flue gas in a short time after the ammonia injection grid.

[0058] Example 5

[0059] This embodiment provides an SCR denitrification device for ultra-low temperature flue gas, such as... Figure 6 As shown, the device includes an ammonia injection grid 1 as described above, and also includes a denitrification reactor 6. The denitrification reactor 6 is provided with a catalyst bed 61 and a burner 62. The burner 62 is located below the catalyst bed 61. The ammonia injection grid 1 is disposed in the denitrification reactor 6 and is located between the catalyst bed 61 and the burner 62.

[0060] Furthermore, the burner 62 is connected to a fuel gas pipeline 63 and a combustion air pipeline 64. The combustion air pipeline provides stable feed air to the denitrification reactor, ensuring that the oxygen content in the boiler flue gas is not less than 1%. The combustion air pipeline 64 is connected to a combustion air fan 65, which provides combustion air to the combustion air pipeline 64 to meet the oxygen content requirements of the denitrification reaction. A multi-channel flue gas mixing scheme can also be configured before the catalyst bed 61 to control the water vapor content in the flue gas to be below 20%.

[0061] The SCR denitrification device in this embodiment also includes other structural components, all of which are commonly used in SCR denitrification devices. During operation, ammonia water is sent to the ammonia evaporator via an ammonia water transfer pump, where it evaporates into ammonia gas. The ammonia water flow rate is controlled by an ammonia water metering pump and a flow meter. The ammonia water evaporation system is only a supplementary system to ensure the integrity of this process and is a common method for preparing ammonia gas, not a limitation. Air is heated by a steam heat exchanger and an electric heater before being sent to the ammonia water evaporator as a heat source for evaporation. Inside the denitrification reactor, the ammonia-air mixture from the ammonia water evaporator is injected into the denitrification flue gas duct through a high-efficiency, low-resistance ammonia injection grid, where it is uniformly mixed with the flue gas before finally entering the denitrification reactor for reaction. The operating temperature inside the denitrification reactor is 150℃~180℃. The flue gas temperature measurement point is located at the inlet of the denitrification reactor. When the flue gas temperature falls below the allowable ammonia injection range, the temperature signal will automatically shut off the ammonia water transfer pump. Ammonia / air mixture (ammonia-air mixture) from the ammonia zone is injected into the inlet flue of the denitrification reactor through an ammonia injection grid. After being uniformly mixed with the flue gas, the injected ammonia-air mixture enters the denitrification reactor and undergoes a redox reaction in the catalyst bed. The catalyst bed in the denitrification reactor is typically set with one or two layers, depending on the denitrification efficiency and inlet NOx value, with one layer set as a backup. The catalyst is a 30- or 35-pore honeycomb catalyst. Furthermore, the ammonia water delivery pump is interlocked with the inlet and outlet NOx concentrations and flue gas volume via a DCS system to ensure that the NOx concentration at the flue gas outlet meets environmental protection requirements.

[0062] The SCR denitrification device in this embodiment, by setting up a burner, can control the water vapor content in the flue gas to be below 20%. When used in conjunction with an ammonia injection grid, it can ensure that the overall catalyst activity is limited in a low-temperature flue gas environment. The catalyst activity can be restored by short-term heating of the burner, avoiding the reduction of catalyst activity caused by water vapor occupying the catalyst active sites.

[0063] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "inner", "outer", "axial", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0065] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0066] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An ammonia injection grid characterized in that, The device includes a surrounding panel, a first ammonia supply pipe, a second ammonia supply pipe, and nozzles. The surrounding panel is a cylindrical structure with open ends. The first ammonia supply pipe is installed in the inner cavity of the surrounding panel and is perpendicular to the central axis of the surrounding panel. The first ammonia supply pipe is provided with multiple nozzles, and the spray direction of the nozzles is arranged towards the open end of the surrounding panel along its axial direction. The second ammonia supply pipe is connected to and communicates with the first ammonia supply pipe, and one end of the second ammonia supply pipe extends to the outside of the surrounding panel. The distance between any two adjacent nozzles is no greater than 200 mm.

2. The ammonia injection lattice of claim 1 wherein, The inner cavity of the enclosure is provided with multiple independently spaced first ammonia supply pipes, and each first ammonia supply pipe is connected to a second ammonia supply pipe.

3. The ammonia injection lattice of claim 1 wherein, The first ammonia supply pipe has an S-shaped bend structure, and the second ammonia supply pipe has an L-shaped structure, a straight structure, or a multi-segment bend structure.

4. The ammonia injection lattice of claim 1 wherein, The enclosure has a rectangular cylindrical structure, and multiple rows of first ammonia supply pipes are provided in the inner cavity of the enclosure.

5. The ammonia injection lattice of claim 1 wherein, The second ammonia supply pipe is arranged perpendicular to the central axis of the enclosure. One end of the second ammonia supply pipe is connected to and communicates with the first ammonia supply pipe, and the other end of the second ammonia supply pipe passes through the enclosure and is fixedly connected to the outer wall of the enclosure through the first connector.

6. The ammonia injection lattice of claim 1 wherein, A connecting beam is provided in the inner cavity of the enclosure, and the first ammonia supply pipe is installed on the connecting beam through a second connector.

7. The ammonia injection lattice of claim 6 wherein, The connecting beam is arranged perpendicular to the central axis of the enclosure, and a support rod is vertically fixed on the connecting beam. Part or all of the second ammonia supply pipes are installed on the corresponding support rods through a third connector.

8. The ammonia injection grid of claim 1 wherein, The nozzle includes an injection pipe, a connecting rod, and a static mixer. One end of the injection pipe is vertically fixed to the first ammonia supply pipe, and the outer wall of the other end of the injection pipe is connected and fixed to the static mixer through the connecting rod. An injection interval is reserved between the static mixer and the other end of the injection pipe.

9. An SCR denitration device applied to ultra-low-temperature flue gas, characterized in that, The device includes an ammonia injection grid as described in any one of claims 1 to 8, and further includes a denitrification reactor, wherein the denitrification reactor is provided with a catalyst bed and a burner, the burner being located below the catalyst bed, and the ammonia injection grid is disposed in the denitrification reactor and located between the catalyst bed and the burner. 10.The SCR denitration device applied to the ultra-low-temperature flue gas according to claim 9, characterized in that, The burner is connected to a fuel gas pipeline and a combustion air pipeline.

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