Ammonia-air mixing device and denitration system

Abstract

The utility model discloses an ammonia air mixing device and denitration system, including mixing pipeline, fixed support fixed on the inside wall of mixing pipeline, be provided with at least one stage turbulent flow subassembly on the fixed support, mixing pipeline and fixed support coaxial arrangement, the turbulent flow subassembly can rotate around the central axis of fixed support, the turbulent flow assembly is used for changing the movement direction of the ammonia gas and the air from linear movement in the axial direction of the mixing pipeline to rotary movement so as to mix the ammonia gas and the air. According to the technical scheme, the turbulent flow assembly is arranged in the mixing pipeline of the ammonia-air mixing device and is supported by the fixing support, the turbulent flow assembly can rotate around the fixing support, and the movement direction of ammonia gas and air in the mixing pipeline is changed from linear movement in the axial direction of the mixing pipeline to rotary movement, so that the ammonia gas and the air are uniformly mixed; the subsequent denitration efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of ammonia-air mixing, and particularly relates to an ammonia-air mixing device and a denitration system. Background Art

[0002] The SCR flue gas denitration technology, namely Selective Catalytic Reduction (abbreviated as SCR), mainly involves injecting the reducing agent ammonia into the dilution air or flue gas upstream of the catalyst, and using the denitration catalyst to convert nitrogen oxides in the flue gas into nitrogen and water at a temperature of 170 to 450 °C. The principle of this technology is that under the action of the denitration catalyst, ammonia is selective and preferentially reacts with nitrogen oxides.

[0003] In denitration design, urea, liquid ammonia or ammonia water is generally used as the raw material for preparing the reducing agent ammonia. No matter in what form ammonia is used, first ammonia is evaporated, then ammonia is mixed with dilution air or flue gas, and finally the mixed gas is injected into the SCR reactor to start the removal of nitrogen oxides.

[0004] The current mixing method generally directly stores the ammonia produced from urea, liquid ammonia or ammonia water in an ammonia tank, and then uses a pipeline to introduce ammonia into the pipeline where the dilution air or flue gas is located for mixing while flowing. Such a mixing method is difficult to make the gas uniform, resulting in too high or too low ammonia concentration in different regions. If the pipeline is short or the mixing time is insufficient, the mixing effect will be worse. Too low ammonia concentration will affect the subsequent denitration reaction, and too high ammonia concentration will cause the ammonia escape rate to exceed the standard, and too high concentration is easy to generate ammonium bisulfate and ammonium sulfate, which will corrode steel structures and instruments. Summary of the Utility Model

[0005] A technical problem to be solved by the utility model is that the current mixing effect of ammonia and air is uneven and the denitration efficiency is low.

[0006] To achieve the above object, on the one hand, the utility model provides an ammonia-air mixing device, which includes a mixing pipeline, a fixed bracket fixed on the inner side wall of the mixing pipeline, and at least one-stage flow disturbing component arranged on the fixed bracket. Among them, the mixing pipeline and the fixed bracket are coaxially arranged, the flow disturbing component can rotate around the central axis of the fixed bracket, and the flow disturbing component is used to change the movement direction of ammonia gas and air from linear movement along the axial direction of the mixing pipeline to rotational movement, so as to mix ammonia gas and air.

[0007] In some embodiments, the flow disturbing component includes a plurality of blades, and the plurality of blades are circumferentially arranged at equal intervals.

[0008] In some embodiments, the radially inner end of the blade is connected to the fixed bracket, the radially outer end of the blade extends to the inner wall surface of the mixing duct, and the radially outer end of the blade is inclined toward the outlet of the mixing duct.

[0009] In some embodiments, the fixed bracket includes a base and a main shaft disposed on the base. The base is fixedly connected to the inner wall of the mixing duct, and the main shaft is located on the central axis of the mixing duct.

[0010] In some embodiments, a first rotary bearing is disposed on the main shaft. The inner ring of the first rotary bearing is connected to the main shaft, and the outer ring of the first rotary bearing is connected to the first end of the flow disturbing assembly.

[0011] In some embodiments, the flow disturbing assembly is provided as a single stage. A second rotary bearing is disposed on the main shaft, and a rotary bracket is connected between the second end of the flow disturbing assembly and the second rotary bearing.

[0012] In some embodiments, the flow disturbing assembly is provided as multiple stages. The first ends of the multiple stages of the flow disturbing assembly are all connected to the first rotary bearing, and the angles between the first stage to the last stage of the flow disturbing assembly and the central axis of the mixing duct decrease in sequence.

[0013] In some embodiments, the multiple stages of the flow disturbing assembly are integrally provided. A second rotary bearing is disposed on the main shaft, and a rotary bracket is connected between the second end of the last stage of the flow disturbing assembly and the second rotary bearing.

[0014] In some embodiments, the fixed bracket and the flow disturbing assembly are disposed in the middle of the mixing duct.

[0015] The second aspect of the present invention provides a denitration system, including the ammonia-air mixing device, an ammonia production device disposed upstream of the ammonia-air mixing device, and a reactor disposed downstream of the ammonia-air mixing device.

[0016] Through the above technical solution, a flow disturbing assembly is disposed in the mixing duct of the ammonia-air mixing device and supported by a fixed bracket. The flow disturbing assembly can rotate around the fixed bracket, changing the movement direction of ammonia and air in the mixing duct from linear movement along the axial direction of the mixing duct to rotational movement, so as to uniformly mix ammonia and air and improve the subsequent denitration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the front view of the ammonia-air mixing device disclosed by the present invention;

[0018] Figure 2 is the left view of the ammonia-air mixing device disclosed by the present invention.

[0019] Description of the Reference Numerals

[0020] 1. Flange; 2. Ammonia injection pipe; 3. Mixing pipe; 4. Turbulence component; 5. Blade; 6. Fixed bracket; 61. Base; 62. Main shaft; 7. Rotating bracket; 8. First rotating bearing; 9. Connecting rod; 10. Second rotating bearing. Detailed Embodiment

[0021] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present invention, and are not intended to limit the present invention.

[0022] To solve the problems of uneven mixing effect of ammonia and air and low denitrification efficiency existing in the prior art, a first aspect of the present invention provides an ammonia-air mixing device, which includes a mixing pipe 3, a fixed bracket 6 fixed on the inner side wall of the mixing pipe 3, and at least one stage of turbulence component 4 arranged on the fixed bracket 6. Among them, the mixing pipe 3 and the fixed bracket 6 are coaxially arranged, and the turbulence component 4 can rotate around the central axis of the fixed bracket 6. The turbulence component 4 is used to change the movement directions of ammonia gas and air from linear movement along the axial direction of the mixing pipe 3 to rotational movement, so as to mix ammonia gas and air.

[0023] As shown in Figure 1-2 , ammonia gas and air can be respectively introduced into the inlet of the mixing pipe 3 along the axial direction, and the inside is a mixing space for air and ammonia gas. The outlet of the mixing pipe 3 can output the mixed gas after mixing ammonia gas and air.

[0024] The fixed bracket 6 can be used to support the turbulence component 4. At the same time, since the fixed bracket 6 is fixed on the inner side wall of the mixing pipe 3, it can also be used to limit the turbulence component 4 in the axial and radial directions, so as to prevent the turbulence component 4 from shifting or falling in the mixing pipe 3 during rotation, affecting the mixing effect of ammonia gas and air and causing damage to the mixing pipe 3.

[0025] The mixing pipe 3 and the fixed bracket 6 are coaxially arranged, and the turbulence component 4 rotates around the central axis of the fixed bracket 6, that is, the turbulence component 4 rotates around the central axis of the mixing pipe 3. In this way, it can be ensured that the ammonia gas and air located in the upper and lower parts of the mixing pipe 3 can both pass through the turbulence component 4 for mixing, making the mixing more uniform.

[0026] In actual production, the ammonia gas and air moving along the axial direction of the mixing pipe 3 pass through the turbulence component 4. First, they will push the turbulence component 4 to rotate. The rotation of the turbulence component 4 will further drive the ammonia gas and air to rotate, changing the movement directions of the ammonia gas and air. Eventually, a vortex will be continuously formed, making the ammonia gas and air mix evenly. The turbulence component 4 has at least one stage, preferably 2 to 3 stages.

[0027] It should be noted that the air in this solution can also be replaced by flue gas or compressed gas, or a mixture of one or more of the three.

[0028] Through the above technical solution, a flow disturbing component 4 is arranged in the mixing pipe 3 of the ammonia-air mixing device and supported by a fixing bracket 6. The flow disturbing component 4 can rotate around the fixing bracket 6, changing the movement direction of ammonia and air in the mixing pipe 3 from linear movement along the axial direction of the mixing pipe 3 to rotational movement, so as to uniformly mix ammonia and air and improve the subsequent denitration efficiency.

[0029] In some embodiments, the flow disturbing component 4 includes a plurality of blades 5, and the plurality of blades 5 are circumferentially arranged at equal intervals.

[0030] Considering the actual production cost and gas mixing effect, the number of blades 5 is greater than or equal to 3, preferably 3 to 4. When the flow disturbing component 4 is multi-stage, the number of blades 5 of each stage of the flow disturbing component 4 is equal. The plurality of blades 5 are circumferentially arranged at equal intervals, avoiding the disadvantages that the stability and balance of the flow disturbing component 4 are poor due to uneven distribution of the blades 5, and the flow disturbing component 4 has large vibration and high noise when rotating, and also ensuring that ammonia and air at each position in the mixing pipe 3 can be uniformly mixed to improve the mixing effect.

[0031] In some embodiments, the radially inner end of the blade 5 is connected to the fixing bracket 6, the radially outer end of the blade 5 extends to the inner wall surface of the mixing pipe 3, and the radially outer end of the blade 5 is inclined towards the outlet of the mixing pipe 3.

[0032] As Figure 1 shown, the connection position of the radially inner end of the blade 5 to the fixing bracket 6 is close to the inlet of the mixing pipe 3, and the blades 5 of the flow disturbing component 4 are all connected to the same position of the fixing bracket 6. When the flow disturbing component 4 is multi-stage, all the blades 5 can be connected to the same position of the fixing bracket 6 so that each stage of the flow disturbing component 4 rotates synchronously.

[0033] The radially outer end of the blade 5 is inclined towards the outlet of the mixing pipe 3, that is, the included angle between the midline of the blade 5 and the central axis of the mixing pipe 3 is an acute angle. On the one hand, this can reduce the resistance suffered by the blade 5 when rotating, and on the other hand, it increases the spatial range in the axial direction of the mixing pipe 3 where the gas can form a vortex. Considering the actual length of the mixing pipe 3, the total amount of gas to be mixed, the production cost and other requirements, the included angle between the midline of the blade 5 and the central axis of the mixing pipe 3 is preferably 30 to 60 degrees, more preferably 45 degrees. When the flow disturbing component 4 is multi-stage, the difference between the included angles between the midlines of the blades 5 of adjacent two-stage flow disturbing components 4 and the central axis of the mixing pipe 3 can be 10 to 15 degrees.

[0034] The radially outer end of the blade 5 extends to the inner wall surface, enabling the spoiler assembly 4 to be approximately the same width as the mixing duct 3, thereby increasing the spatial range within the mixing duct 3 in the radial direction where gas can form vortices. To prevent the blade 5 from colliding with the inner wall of the mixing duct 3 during rotation, there is a gap between the radially outer end of the blade 5 and the inner wall surface of the mixing duct 3.

[0035] As Figure 1 and 2 shown, the projection of the blade 5 on the cross-section of the mixing duct 3 can be an isosceles triangle to enhance structural stability. There can be a certain angular difference between the angles formed by the two long sides of the blade 5 and the central axis of the mixing duct 3 to further reduce the resistance experienced by the blade 5 during rotation. In some specific embodiments, the angular difference can be set to 12.5 to 14.8 degrees.

[0036] In some embodiments, the fixed bracket 6 includes a base 61 and a main shaft 62 disposed on the base 61. The base 61 is fixedly connected to the inner wall of the mixing duct 3, and the main shaft 62 is located on the central axis of the mixing duct 3.

[0037] As Figure 1 shown, the base 61 can be composed of one or more rods. One end of the rod is fixed to the inner wall of the mixing duct 3, and the other end of the rod is connected to the main shaft 62. To further improve the support effect, the base 61 can also include a ring body fixed to the inner wall of the mixing duct 3. One end of the rod is fixedly connected to the ring body, and the other end is connected to the main shaft 62. The main shaft 62 can be a long rod extending along the central axis of the mixing duct 3. The base 61 and the main shaft 62 can be connected by welding or screwing or integrally formed.

[0038] In some embodiments, a first rotary bearing 8 is provided on the main shaft 62. The inner ring of the first rotary bearing 8 is connected to the main shaft 62, and the outer ring of the first rotary bearing 8 is connected to the first end of the spoiler assembly 4.

[0039] The spoiler assembly 4 is rotatably disposed on the fixed bracket 6 through a rotary bearing. Specifically, as Figure 1 shown, the first end of the spoiler assembly 4 is the end close to the inlet of the mixing duct 3, and it is connected to the first rotary bearing 8 sleeved on the main shaft 62. Among them, the inner ring of the first rotary bearing 8 is connected to the main shaft 62, and the outer ring of the first rotary bearing 8 is connected to the first end of the spoiler assembly 4. When the spoiler assembly 4 rotates, the outer ring of the first rotary bearing 8 rotates together with the spoiler assembly 4, and the inner ring of the first rotary bearing 8 remains fixed to the main shaft 62.

[0040] In some embodiments, the spoiler assembly 4 is provided as a single stage, a second rotary bearing 10 is provided on the main shaft 62, and a rotary bracket 7 is connected between the second end of the spoiler assembly 4 and the second rotary bearing 10.

[0041] The rotating bracket 7 can be a connecting rod connected between the second end of the spoiler assembly 4 and the main shaft 62, which is used to support and shape the spoiler assembly 4, so as to prevent the second end of the spoiler assembly 4 from deforming or displacing under high-speed air flow, which may affect the mixing effect. Specifically, as Figure 1 shown, the second end of the spoiler assembly 4 is the end close to the outlet of the mixing duct 3. The rotating bracket 7 is connected to the second rotating bearing 10 sleeved on the main shaft 62. Among them, the inner ring of the second rotating bearing 10 is connected to the main shaft 62, the outer ring of the second rotating bearing 10 is connected to the rotating bracket 7, and the rotating bracket 7 is fixedly connected to the second end of the spoiler assembly 4. When the spoiler assembly 4 rotates, the rotating bracket 7 and the outer ring of the second rotating bearing 10 rotate together with the spoiler assembly 4, and the inner ring of the second rotating bearing 10 remains fixed to the main shaft 62.

[0042] In some embodiments, the spoiler assembly 4 is provided in multiple stages. The first ends of the multi-stage spoiler assemblies 4 are all connected to the first rotating bearing 8, and the angles between the first stage to the last stage of the spoiler assemblies 4 and the central axis of the mixing duct 3 decrease in sequence.

[0043] As Figure 1 shown, multiple-stage spoiler assemblies 4 can be provided to further enhance the disturbance of ammonia and air and improve the mixing effect. The first ends of the multi-stage spoiler assemblies 4 are all connected to the same position of the fixed bracket 6 so that the spoiler assemblies 4 at all levels rotate synchronously. In order to prevent the multi-stage spoiler assemblies 4 from interfering with each other during rotation, the angles between the first stage to the last stage of the spoiler assemblies 4 and the central axis of the mixing duct 3 decrease in sequence. The difference in the angles between two adjacent stages of the spoiler assemblies 4 and the central axis of the mixing duct 3 is preferably greater than or equal to 10 degrees.

[0044] In some embodiments, the multi-stage spoiler assemblies 4 are integrally provided. A second rotating bearing 10 is provided on the main shaft 62, and a rotating bracket 7 is connected between the second end of the last stage of the spoiler assembly 4 and the second rotating bearing 10.

[0045] As Figure 1 shown, setting the multi-stage spoiler assemblies 4 integrally can further enhance the overall stability of the multi-stage spoiler assemblies 4. Specifically, multiple axially extending connecting rods can be provided at the middle position of the spoiler assembly 4, and both ends of the connecting rods are fixedly connected to two adjacent stages of the spoiler assemblies 4.

[0046] The rotating bracket 7 can be a connecting rod between the second end of the spoiler assembly 4 connected to the last stage and the main shaft 62, which is used to support and shape the spoiler assembly 4, avoiding deformation or displacement of the second end of the spoiler assembly 4 under high-speed air flow and affecting the mixing effect. The rotating bracket 7 is connected to the second rotating bearing 10 sleeved on the main shaft 62. Among them, the inner ring of the second rotating bearing 10 is connected to the main shaft 62, the outer ring of the second rotating bearing 10 is connected to the rotating bracket 7, and the rotating bracket 7 is fixedly connected to the second end of the last-stage spoiler assembly 4. When the multi-stage spoiler assembly 4 rotates synchronously, the rotating bracket 7 and the outer ring of the second rotating bearing 10 rotate together with the multi-stage spoiler assembly 4, and the inner ring of the second rotating bearing 10 remains fixed to the main shaft 62.

[0047] A speed regulating mechanism can be further provided on the above-mentioned first rotating bearing 8 and second rotating bearing 10 to adjust the rotation speed of the spoiler assembly 4. Since the gas flow rate passing through the spoiler assembly 4 is relatively fast, usually only the upper limit of the speed needs to be restricted, and the speed regulating mechanism can be a braking mechanism. The rotation speed of the spoiler assembly 4 in this application is generally 0.6 to 7 revolutions per second.

[0048] In some embodiments, the fixed bracket 6 and the spoiler assembly 4 are arranged in the middle of the mixing pipe 3.

[0049] As Figure 1 shown, arranging the fixed bracket 6 and the spoiler assembly 4 in the middle of the mixing pipe 3 can reserve a flow space for the mixed gas at the rear of the mixing pipe 3. In this way, the space of the mixing pipe 3 can be divided into an ammonia and air intake space at the front, an ammonia and air mixing space in the middle, and a mixed gas flow space at the rear. In some other embodiments, an ammonia injection grid or a vortex mixer can be further installed in the middle space. Ammonia and air can pass through the ammonia injection grid or the vortex mixer first and then be mixed by the spoiler assembly 4; in the rear space, devices such as a guiding member and a rectifying grid can be provided to guide the mixed gas to flow to the subsequent device.

[0050] The second aspect of the present utility model provides a denitration system, which includes an ammonia-air mixing device, an ammonia production device arranged upstream of the ammonia-air mixing device, and a reactor arranged downstream of the ammonia-air mixing device.

[0051] As Figure 1 shown, the outlet end of the ammonia production device can be connected with an ammonia injection pipe 2. The ammonia injection pipe 2 can extend into the central axis of the mixing pipe 3 perpendicular to the outer side wall of the mixing pipe 3 and bend along the central axis of the mixing pipe 3 to eject ammonia. The distance between the air outlet of the ammonia injection pipe 2 and the spoiler assembly 4 is greater than 50 mm to ensure that ammonia forms a dispersed state in the mixing pipe 3 before entering the spoiler assembly 4.

[0052] Flanges 1 are provided at both ends of the mixing pipe 3 of the ammonia-air mixing device. The flange 1 at the inlet is used to connect the air or flue gas inlet pipe, and the flange 1 at the outlet can be connected to a reactor equipped with a denitration catalyst downstream for denitration. The mixing pipe 3 can also be first connected to equipment such as a hopper and a heat exchanger according to actual production needs, and then connected to a reactor equipped with a denitration catalyst downstream for denitration.

[0053] In addition, areas in contact with ammonia and air, such as the inner side walls of the ammonia injection pipe 2 and the mixing pipe 3, the flow disturbance components 4, the fixed brackets 6, the first rotary bearings 8, the connecting rods 9, and the second rotary bearings 10, all need to be treated with rust and corrosion prevention.

[0054] According to the requirements of DL / T 1418-2015 "Technical Specification for Flow Field Simulation of SCR Flue Gas Denitration in Coal-Fired Power Plants", the relative standard deviation of the molar ratio of NH3 / NOX at the inlet of the first layer of catalyst in the reactor in the numerical simulation results should satisfy ≤7% (i.e., the ammonia mixing uniformity index). Experiments have shown that with the denitration system of the present application, the relative standard deviation of the molar ratio of NH3 / NOX at the inlet of the first layer of catalyst in the reactor in the above numerical simulation results can satisfy ≤5%, which is better than the industry standard value (DL / T 1418-2015).

[0055] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any suitable combination of each specific technical feature. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An ammonia-air mixing device, characterized in that, It includes a mixing pipe (3), a fixed bracket (6) fixed on the inner side wall of the mixing pipe (3), and at least one stage of flow disturbance components (4) arranged on the fixed bracket (6). Among them, the mixing pipe (3) and the fixed bracket (6) are coaxially arranged, the flow disturbance component (4) can rotate around the central axis of the fixed bracket (6), and the flow disturbance component (4) is used to change the movement directions of ammonia gas and air from linear movement along the axial direction of the mixing pipe (3) to rotational movement, so as to mix ammonia gas and air.

2. The ammonia-air mixing device according to claim 1, characterized in that, The flow disturbance component (4) includes a plurality of vanes (5), and the plurality of vanes (5) are circumferentially arranged at equal intervals.

3. The ammonia-air mixing device according to claim 2, characterized in that, The radially inner end of the vane (5) is connected to the fixed bracket (6), the radially outer end of the vane (5) extends to the inner side wall surface of the mixing pipe (3), and the radially outer end of the vane (5) is inclined towards the outlet of the mixing pipe (3).

4. The ammonia-air mixing device according to claim 1, characterized in that, The fixed bracket (6) includes a base (61) and a main shaft (62) arranged on the base (61). The base (61) is fixedly connected to the inner side wall of the mixing pipe (3), and the main shaft (62) is located on the central axis of the mixing pipe (3).

5. The ammonia-air mixing device according to claim 4, characterized in that A first rotary bearing (8) is arranged on the main shaft (62). The inner ring of the first rotary bearing (8) is connected to the main shaft (62), and the outer ring of the first rotary bearing (8) is connected to the first end of the flow disturbance component (4).

6. The ammonia-air mixing device according to claim 5, characterized in that, The flow disturbance component (4) is arranged in one stage. A second rotary bearing (10) is arranged on the main shaft (62), and a rotary bracket (7) is connected between the second end of the flow disturbance component (4) and the second rotary bearing (10).

7. The ammonia-air mixing device according to claim 5, characterized in that The flow disturbance component (4) is arranged in multiple stages. The first ends of the multiple stages of flow disturbance components (4) are all connected to the first rotary bearing (8), and the angles between the first stage to the last stage of the flow disturbance components (4) and the central axis of the mixing pipe (3) decrease in sequence.

8. The ammonia-air mixing device according to claim 7, characterized in that, The multiple stages of flow disturbance components (4) are integrally arranged. A second rotary bearing (10) is arranged on the main shaft (62), and a rotary bracket (7) is connected between the second end of the last stage of the flow disturbance component (4) and the second rotary bearing (10).

9. The ammonia-air mixing device according to claim 1, characterized in that The fixed bracket (6) and the flow disturbance component (4) are arranged in the middle of the mixing pipe (3).

10. A denitration system, characterized in that, It includes the ammonia-air mixing device according to any one of claims 1-9, an ammonia production device arranged upstream of the ammonia-air mixing device, and a reactor arranged downstream of the ammonia-air mixing device.

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