Selective catalytic reduction denitrification apparatus
The cylindrical apparatus with an injection pipe, catalyst, and drain pan efficiently manages condensate in selective catalytic reduction systems, preventing droplet formation and corrosion, thus reducing costs and maintaining catalyst effectiveness.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MITSUBISHI HEAVY IND ENVIRONMENTAL & CHEM ENG CO LTD
- Filing Date
- 2025-12-24
- Publication Date
- 2026-05-29
Smart Images
Figure 0007867616000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a selective catalytic reduction denitration device.
Background Art
[0002] Exhaust gas generated by combustion devices such as incinerators in waste cleaning factories and boilers in thermal power plants is discharged from chimneys. Since the exhaust gas contains nitrogen oxides, after decomposing and purifying the nitrogen oxides contained in the exhaust gas by a denitration device, the exhaust gas is discharged from the chimney into the atmosphere. As a denitration device, there is one that uses the selective catalytic reduction method (Selective Catalytic Reduction method; hereinafter referred to as the "SCR method"). The SCR method is a method in which an ammonia source aqueous solution such as aqueous ammonia or aqueous urea is vaporized and mixed with exhaust gas, and then the nitrogen oxides contained in the exhaust gas are decomposed by a catalyst installed downstream thereof.
[0003] As such a denitration device, for example, Patent Document 1 discloses a configuration in which a gas obtained by vaporizing steam and an ammonia source aqueous solution with an ejector is injected toward exhaust gas. In this configuration, the gas is introduced into a linear injection pipe and injected toward the exhaust gas from a plurality of holes or nozzles arranged in alignment in the length direction of the injection pipe. Then, the exhaust gas is denitrified by a catalyst installed downstream of the injection pipe. Here, when drain (that is, what remains after the gas obtained by vaporizing steam and an ammonia source aqueous solution is liquefied) is generated in the injection pipe, if the drain remains in the injection pipe, it may be impossible to appropriately inject the gas. Therefore, in this denitration device, a drain trap is installed to capture the drain.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, in the configuration described in Patent Document 1, depending on conditions such as the gas pressure, the drain generated in the injection tube may be ejected in the form of droplets. Since these droplets are an aqueous ammonia source solution, if they adhere to the walls of the internal structure of the denitrification device, they may cause corrosion and damage to the walls, and if they adhere to the catalyst, they may degrade the catalyst.
[0006] The present invention has been made to solve the above problems, and aims to provide a selective catalytic reduction denitrification apparatus that can reduce manufacturing costs and prevent the injection of liquid droplets of condensate from the injection tube even when condensate is generated in the injection tube. [Means for solving the problem]
[0007] To solve the above problems, the selective catalytic reduction denitrification apparatus according to the present invention has at least the following configuration: A cylindrical metal structure equipped with an inlet and outlet for exhaust gas generated by a combustion device, An injection pipe is installed inside a cylindrical structure and injects a vaporized ammonia source aqueous solution into the exhaust gas, A denitrification catalyst is installed inside a cylindrical structure and positioned downstream of the injection pipe in the direction of exhaust gas flow within the cylindrical structure, A drain pan is installed inside the cylindrical structure and positioned below the injection pipe. It holds.
[0008] The above-mentioned injection pipe is provided horizontally, or is provided so as to extend downward from the first end to the second end at a predetermined angle of 0 to 10 degrees from the horizontal, and has a straight pipe section having a plurality of injection holes or a plurality of injection nozzles, A bent pipe section is connected to a straight pipe section, and a portion of the straight pipe is bent in an L-shape or J-shape in a direction different from the longitudinal direction of the straight pipe. It is equipped with.
[0009] The straight pipe section described above has its first end on one side in the direction of extension, or a portion of its vicinity, airtightly connected to the wall surface of the cylindrical structure. The bent pipe section is positioned lower than the straight pipe section, with the third end on one side in the direction of extension of the bent pipe section connected to or near the second end on the other side in the direction of extension of the straight pipe section, and the fourth end on or near the other side in the direction of extension of the bent pipe section is provided with a discharge hole located vertically above the drain pan and facing downward.
[0010] Then, when the above gas is introduced into the first end of the injection pipe and condensate is generated in the straight section, the condensate is discharged from the discharge hole in the bent section to the drain pan due to the pressure or gravity of the gas introduced at that time, and the drain pan captures the condensate. [Effects of the Invention]
[0011] According to the selective catalytic reduction denitrification apparatus of the present invention, a vaporized ammonia source aqueous solution is injected from the injection nozzle of the injection pipe into the exhaust gas introduced into the cylindrical structure. As a result, nitrogen oxides contained in the exhaust gas are decomposed by a denitrification catalyst located downstream of the injection pipe, and the exhaust gas is purified. The gas introduced into the injection tube liquefies in the straight section of the tube, and the resulting condensate moves smoothly from the straight section to the bent section of the tube below it, due to the pressure or gravity of the gas. The condensate that has moved to the bent section then falls into a drain pan through a discharge hole installed in the bent section and is captured. Therefore, since the drain in the straight pipe section is quickly removed, it is possible to prevent the drain from being sprayed in droplet form from the injection nozzle of the injection pipe. As a result, corrosion of the wall surface of the cylindrical structure and deterioration of the denitrification catalyst can be prevented. Furthermore, the injection tube has a simple structure and does not require the installation of complex devices such as drain traps, thus reducing manufacturing costs. In other words, it is possible to provide a selective catalytic reduction denitrification apparatus that can reduce manufacturing costs while preventing the injection of condensate droplets from the injection tube even when condensate is generated in the injection tube. [Brief explanation of the drawing]
[0012] [Figure 1] This is a cross-sectional view showing the schematic configuration of the selective catalytic reduction denitrification apparatus 1A of the embodiment. [Figure 2] This is a cross-sectional view taken along the line II-II in Figure 1. [Figure 3] This is a cross-sectional view showing the schematic configuration of a selective catalytic reduction denitrification apparatus 1B, which is an application example of the embodiment. [Figure 4] This is a cross-sectional view showing the schematic configuration of the first modified example, selective catalytic reduction denitrification apparatus 1C. [Figure 5] This is a cross-sectional view showing the schematic configuration of a second modified example, a selective catalytic reduction denitrification apparatus 1D. [Modes for carrying out the invention]
[0013] The following describes the selective catalytic reduction denitrification apparatus, including embodiments and various modifications, sequentially with reference to Figures 1 to 5, which use a Cartesian coordinate system with X, Y, and Z axes. Here, the Z axis is the vertical direction. The arrow on the Z axis indicates an upward direction, and the opposite direction indicates a downward direction. The embodiments and their variations are merely illustrative examples and do not preclude the application of various modifications or techniques not explicitly stated. Except for the components essential to the present invention, the components described below can be selected or modified as needed.
[0014] (Selective catalytic reduction denitrification apparatus 1A of the embodiment) First, the selective catalytic reduction denitrification apparatus 1A of the embodiment will be described using Figure 1. The metal cylindrical structure 2A is a cylindrical structure with an inlet 6 at one end and an outlet 7 at the other end. Exhaust gas generated by a combustion device (not shown), such as an incinerator or boiler, is introduced through piping (not shown), such as a duct, into the inlet 6 located above the Z-axis, passes through the inside of the cylindrical structure 2A, and is discharged from the outlet 7 located below the Z-axis. Therefore, the exhaust gas flowing inside the selective catalytic reduction denitrification device 1A flows from top to bottom. Therefore, the injection pipe 3, drain pan 5, and denitration catalyst 4 described below are installed inside the selective catalytic reduction denitration apparatus 1A in this order from above to below. That is, the drain pan 5 is installed below the injection pipe 3, and the denitration catalyst 4 is installed below the drain pan 5. Also, as will be described later, a support portion 11 that can support one end of the injection pipe 3 from below is installed on the inner wall of the cylindrical structure 2A.
[0015] The injection pipe 3 is inserted into the inside of the cylindrical structure 2A through a through-hole 2h arranged on the side surface of the cylindrical structure 2A, and is stably installed inside the cylindrical structure 2A by airtightly fixing a flange 10 described later to the through-hole 2h. The injection pipe 3 includes a straight pipe portion 8 that is a straight linear pipe, and a bent pipe portion 9 connected to the straight pipe portion 8. A plurality of injection nozzles 12 are installed in a row in the X-axis direction on the straight pipe portion 8. The injection nozzles 12 can inject the gas described later upward. That is, the injection nozzles 12 can inject the gas in a direction opposite to the flow of the exhaust gas, in other words, toward the upstream of the flow of the exhaust gas. The bent pipe portion 9 includes a curved portion 9w in which a part of a straight linear pipe separate from the straight pipe portion 8 is bent in an L-shape or a J-shape in a direction different from the length direction of the straight pipe, and a straight portion 9s that is the straight pipe.
[0016] The injection pipe 3 is configured such that one end of the bent pipe portion 9 (one end of the curved portion 9w, the third end portion 9a) is connected to the second end portion 8b of the straight pipe portion 8 described later or its vicinity. The inner spaces of the straight pipe portion 8 and the bent pipe portion 9 are connected to each other without being blocked at the connected location. Therefore, drain can flow smoothly from the straight pipe portion 8 to the bent pipe portion 9. However, since the bent pipe portion 9 has a curved portion 9w connected to the straight pipe portion 8, due to an increase in the flow path resistance in the curved portion 9w, the gas flowing through the straight pipe portion 8 is difficult to enter the bent pipe portion 9. Therefore, the gas can be efficiently used for injection by the injection nozzles 12 of the straight pipe portion 8. If the inner diameter of the curved portion 9w is designed to be smaller than the inner diameter of the straight pipe portion 8, this effect can be further enhanced. A discharge hole 14 is installed facing downwards at the other end of the bent pipe section 9 (one end of the straight section 9s, which is the fourth end 9b) or in its vicinity. The discharge hole 14 is positioned so that a drain pan 5 is located directly below it. The drain pan 5 is a dish-shaped structure that captures the drain that falls from the discharge hole 14. The drain captured in the drain pan 5 is automatically vaporized by the high-temperature exhaust gas. Therefore, by appropriately designing the size of the drain pan 5, it is possible to avoid situations where the drain overflowing from the drain pan 5 comes into contact with the denitrification catalyst 4 below.
[0017] The straight pipe section 8 and the bent pipe section 9 may be fixed to a metal, rod-shaped connecting member 13, for example by welding, so that they are firmly integrated as a spray pipe 3 by connecting them at multiple points, for example, two points, rather than just one point. In Figure 1, the fourth end portion 9b of the bent pipe section 9 and the side surface of the straight pipe section 8 located vertically above it are fixed with the connecting member 13.
[0018] With the injection tube 3 positioned inside the cylindrical structure 2A, one end of the straight section 8 of the injection tube 3 is the first end 8a, which protrudes from the hole 2h on the side of the cylindrical structure 2A. The other end of the straight section 8 is the second end 8b. From the first end 8a, a gas is introduced into the straight section 8, which is produced by vaporizing steam and an ammonia source aqueous solution (e.g., ammonia water, urea water, etc.) in an ejector. A flange 10 is airtightly inserted into the straight pipe section 8 at or near the first end 8a.
[0019] In Figure 1, the straight pipe section 8 is installed horizontally (in the X-axis direction). However, the straight pipe section 8 may be installed tilted downward by a predetermined angle from 0 to 10 degrees from the virtual horizontal plane, from the first end 8a to the second end 8b. For example, the injection pipe 3 may be installed such that the straight pipe section 8 is tilted downward by an angle of 7 degrees from the first end 8a to the second end 8b. If condensate is generated in the straight pipe section 8, even if the straight pipe section 8 is installed horizontally, the pressure generated when the gas is introduced into the straight pipe section 8 will push the condensate out from the straight pipe section 8 to the bent pipe section 9, and the condensate can be discharged from the discharge hole 14 of the bent pipe section 9 to the drain pan 5. However, as described above, by arranging the straight pipe section 8 at an angle, gravity can also be used to guide the condensate more smoothly from the straight pipe section 8 to the bent pipe section 9. Similarly, the straight portion 9s of the bent pipe section 9 may be installed horizontally, or it may be installed tilted downward by a predetermined angle from 0 to 10 degrees from the virtual horizontal plane, from the third end 9a to the fourth end 9b.
[0020] Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. The support portion 11 has a linear shape in the longitudinal direction, and its cross-sectional shape should preferably be wider towards the top, for example, a V-shape or a U-shape. For the support portion 11, for example, a commercially available metal angle material can be used. When installing the injection pipe 3 inside the cylindrical structure 2A, temporarily placing the second end 8b of the straight pipe section 8 on the support section 11 makes the installation of the injection pipe 3 easier. Also, when removing the injection pipe 3 from inside the cylindrical structure 2A for maintenance, temporarily placing the second end 8b on the support section 11 makes the removal process easier. When the injection pipe 3 is fixed to the cylindrical structure 2A with the flange 10, depending on the design, the second end portion 8b may be resting on the support portion 11, or it may not be resting on the support portion 11 and may be floating above the support portion 11. The support portion 11 only needs to be a structure that stably supports the second end 8b of the straight pipe portion 8 inside the cylindrical structure 2A, so it is not limited to the above structure, and for example, it may be a metal rod (support bar) fixed at both ends to the inner wall of the cylindrical structure 2A.
[0021] (Selective catalytic reduction denitrification apparatus 1B, an application example of the embodiment) Next, a selective catalytic reduction denitrification apparatus 1B, which is an application example in which the connecting member 13 of the selective catalytic reduction denitrification apparatus 1A of the embodiment is replaced with a guide plate 15, will be described with reference to Figure 3. The only difference between the selective catalytic reduction denitrification apparatus 1B and the selective catalytic reduction denitrification apparatus 1A is that the guide plate 15 is installed instead of the connecting member 13. Therefore, a description of the same configuration and effects as the selective catalytic reduction denitrification apparatus 1A will be omitted. The guide plate 15 is a metal member in the shape of a right-angled triangular plate. When viewed in the X-axis direction, it is installed closer to the first end 8a of the straight pipe section 8 than to a virtual line L that is perpendicular to the straight pipe section 8 and passes through the fourth end 9b of the bent pipe section 9. For example, in the right-angled triangular guide plate 15, one of the two sides excluding the hypotenuse is fixed (e.g., welded) below the straight pipe section 8, and the other side extending vertically is fixed (e.g., welded) to the fourth end 9b of the bent pipe section 9. When the guide plate 15 is installed in this manner, the portion 15s corresponding to the hypotenuse becomes an inclined surface connecting a part of the straight pipe section 8 and the fourth end portion 9b. When the injection pipe 3 is withdrawn from the inside of the cylindrical structure 2A for maintenance, this inclined surface can be used as a sliding surface for the injection pipe 3. For example, by gradually withdrawing the injection pipe 3 while bringing this sliding surface into contact with the hole 2h of the cylindrical structure 2A, the injection pipe 3 can be safely and quickly removed from the outside of the cylindrical structure 2A.
[0022] (Selective catalytic reduction denitrification apparatus 1C, which is the first modified example) Next, the first modified example, the selective catalytic reduction denitrification apparatus 1C, will be explained using Figure 4. The difference between the selective catalytic reduction denitrification apparatus 1C and the selective catalytic reduction denitrification apparatus 1A of the embodiment is that, in the selective catalytic reduction denitrification apparatus 1C, the exhaust gas flow is from bottom to top, so the positions of each component of the selective catalytic reduction denitrification apparatus 1A are changed to correspond to the exhaust gas flow. The cylindrical structure 2C of the selective catalytic reduction denitrification apparatus 1C is the same as the cylindrical structure 2A of the selective catalytic reduction denitrification apparatus 1A, installed upside down, and therefore has an inlet 6 at the bottom and an outlet 7 at the top. The support portion 11 is appropriately installed on the inner wall of the cylindrical structure 2C so that the second end portion 8b of the straight pipe portion 8 can be placed on it. Furthermore, in the selective catalytic reduction denitrification apparatus 1A, the denitrification catalyst 4, which was located inside the cylindrical structure 2A below the drain pan 5, is installed above the injection pipe 3 in the selective catalytic reduction denitrification apparatus 1C. In the selective catalytic reduction denitrification apparatus 1C, as in the selective catalytic reduction denitrification apparatus 1A, the injection nozzle 12 of the injection pipe 3 injects upward a vaporized ammonia source aqueous solution. Therefore, the distance between the denitrification catalyst 4 and the injection pipe 3 is designed so that the gas is not directly sprayed onto the denitrification catalyst 4. Further explanations regarding the same configuration and effects as the selective catalytic reduction denitrification apparatus 1A will be omitted.
[0023] (Second modified example: Selective catalytic reduction denitrification apparatus 1D) Finally, the second modified example, the selective catalytic reduction denitrification apparatus 1D, will be explained using Figure 5. The difference between the selective catalytic reduction denitrification apparatus 1D and the selective catalytic reduction denitrification apparatus 1A of the embodiment is that in the selective catalytic reduction denitrification apparatus 1D, the exhaust gas flow is horizontal, specifically, from left to right in Figure 5, so the positions of each component of the selective catalytic reduction denitrification apparatus 1A are changed to correspond to the exhaust gas flow. The cylindrical structure 2D of the selective catalytic reduction denitrification apparatus 1D is a horizontally mounted version of the cylindrical structure 2A of the selective catalytic reduction denitrification apparatus 1A, and therefore, when viewed along the X-axis, it has an inlet 6 on the left and an outlet 7 on the right. Unlike the embodiments and the first modified example, the injection tube 3' has its injection nozzle 12 positioned horizontally to allow for horizontal injection. Specifically, the injection nozzle 12 of the injection tube 3' injects the vaporized ammonia source aqueous solution to the right. The denitrification catalyst 4 is positioned to the right of the injection pipe 3', downstream of the injection pipe 3' in the exhaust gas flow. Since the injection nozzle 12 of the injection pipe 3' injects the gas to the right, the distance between the denitrification catalyst 4 and the injection pipe 3' is designed so that the gas is not directly sprayed onto the denitrification catalyst 4. Although not shown in Figure 5, the support section 11 is installed on the inner wall of the cylindrical structure 2D so that the second end 8b of the corresponding straight pipe section 8 can be placed on it. Figure 5 shows a configuration in which two sets of unit configurations, each consisting of an injection pipe 3' and a drain pan 5 positioned directly below the injection pipe 3', are arranged vertically. Therefore, two support sections 11 are installed according to each unit configuration. Further explanations regarding the same configuration and effects as the selective catalytic reduction denitrification apparatus 1A will be omitted.
[0024] Embodiments and modifications of the present invention have been described above. However, the selective catalytic reduction denitrification apparatus of the present invention is not limited to these configurations. For example, in the embodiments, application examples, and first modifications, multiple sets of a single unit configuration consisting of an injection pipe and a drain pan positioned directly below the injection pipe may be installed, similar to the selective catalytic reduction denitrification apparatus of the second modification. Furthermore, in the embodiment and application examples, the injection nozzle of the injection tube is configured to inject the gas in the opposite direction to the exhaust gas flow, while in each modified example, it is configured to inject the gas in the same direction as the exhaust gas flow. However, the injection nozzle may be installed facing any direction, as long as it is appropriately designed so that the gas is not directly sprayed onto the inner wall of the denitrification catalyst or cylindrical structure located downstream of the injection tube in the exhaust gas flow, and so that the gas can be mixed into the exhaust gas without bias. Furthermore, the injection nozzle in the above description may simply be replaced with an injection hole, which is a hole that penetrates the injection tube. [Explanation of symbols]
[0025] 1A~1D…Selective catalytic reduction denitrification equipment 2A, 2C, 2D...Cylindrical structure 2h…hole 3, 3´...Injection pipe 4...Denitrification catalyst 5... Drain pan 6... Inlet 7…Discharge port 8…Straight pipe section 8a...first end 8b…Second end 9...Bent tube part 9a...Third end 9b...Fourth end 9s…straight line part 9w... curved part 10…Flange 11...Support part 12... Spray nozzle 13…Connecting member 14...Discharge hole 15… Guide plate
Claims
1. A cylindrical metal structure equipped with an inlet and outlet for exhaust gas generated by a combustion device, An injection pipe is installed inside the cylindrical structure and injects a gas obtained by vaporizing an ammonia source aqueous solution into the exhaust gas, A denitrification catalyst is installed inside the cylindrical structure and positioned downstream of the injection pipe in the direction of exhaust gas flow within the cylindrical structure, A drain pan is installed inside the cylindrical structure and positioned below the injection pipe. It has, The injection tube is A straight pipe section is provided horizontally, or is provided so as to extend downward from the first end to the second end at a predetermined angle of 0 to 10 degrees from the horizontal direction, and has a plurality of injection holes or a plurality of injection nozzles, A bent pipe section connected to the straight pipe section, in which a part of the straight pipe is bent in an L-shape or J-shape in a direction different from the longitudinal direction of the straight pipe, Equipped with, The straight pipe section is airtightly connected to the wall surface of the cylindrical structure at one end or near the first end on one side in the direction of extension. The curved pipe section is positioned lower than the straight pipe section, with the third end on one side in the direction of extension of the curved pipe section connected to or near the second end on the other side in the direction of extension of the straight pipe section, and the fourth end on or near the other side in the direction of extension of the curved pipe section is provided with a discharge hole located vertically above the drain pan and facing downward. When the gas is introduced into the first end of the injection pipe and condensate is generated in the straight section, the condensate is discharged from the discharge hole in the bent section to the drain pan due to the pressure or gravity of the gas introduced during the introduction, and the drain pan captures the condensate. Selective catalytic reduction denitrification apparatus.
2. The selective catalytic reduction denitrification apparatus according to claim 1, wherein the bent pipe section has a smaller inner diameter than the straight pipe section.
3. The cylindrical structure further has a support portion that is fixed to the inner wall and supports the second end of the straight pipe section from below, The selective catalytic reduction denitrification apparatus according to claim 2, wherein when the injection pipe is installed inside the cylindrical structure, the second end can be temporarily placed at least on the support portion.
4. The selective catalytic reduction denitrification apparatus according to claim 3, wherein the straight pipe section and the bent pipe section are fixed by an inclined guide plate provided on the first end side of a virtual line perpendicular to the straight pipe section passing through the fourth end in the extension direction of the straight pipe section, and connecting a part of the straight pipe section and the fourth end.
5. The selective catalytic reduction denitrification apparatus according to any one of claims 1 to 4, wherein the straight pipe section is positioned such that the second end is inclined downward by an angle of 7 degrees from the horizontal compared to the first end.