SCR denitration system

Abstract

The present application relates to the technical fields of atmospheric pollutant treatment, and discloses a SCR denitration system, which comprises a coal economizer, a flue, a denitration device and an intercepting assembly. The coal economizer is provided with an exhaust port on the side surface. The gas inlet of the flue is connected to the exhaust port of the coal economizer. The denitration device is installed in the flue. The intercepting assembly is arranged at the exhaust port. The intercepting assembly comprises a vibrator and an intercepting part. The intercepting part covers the exhaust port. The intercepting part comprises an intercepting filter screen and a baffle which are connected in sequence. The vibrator drives the intercepting part to vibrate so as to shake off the dust deposited on the intercepting part. Since the flow direction of the flue gas rotates from the exhaust port of the coal economizer to the flue, under the combined action of the initial speed and gravity, the large-particle dust in the flue gas is separated by inertia, and the volume of the dust particles from top to bottom at the exhaust port of the coal economizer is from small to large. The vibrator is used to beat the intercepting part. The large-particle dust freely falls and almost does not block the intercepting screen, so that the large-particle dust entering the denitration device is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air pollution control, in particular to an SCR denitration system. BACKGROUND

[0002] Coal is usually used as the fuel source in thermal power plants as the main energy source. Nitrogen oxides are one of the gaseous pollutants discharged in the process of burning coal. At present, the selective catalytic reduction (SCR) technology is widely used in coal-fired units at home and abroad due to its advantages such as mature technology, high denitration efficiency, etc. The principle of the SCR technology is that the reducing agent NH3 is selectively reduced into N2 under the action of the catalyst at a temperature range of 290-410 ℃, which is a nitrogen oxide emission reduction technology. The denitration efficiency of the SCR technology can usually reach more than 90%, and the catalyst is the core element of the SCR denitration process, the activity of which is affected by the temperature, the flue gas condition and the flue gas composition. The SCR denitration reactor is generally installed in the high-temperature and high-dust area between the boiler economizer and the air preheater, and in the actual application, a large amount of dust entering the denitration device is one of the factors affecting the performance of the denitration catalyst, and the influence of large-particle dust on the activity of the denitration catalyst is the most obvious.

[0003] At present, most power plants pursue economic operation, and the mixed combustion of coal, sludge and biomass is variable, and the burning of coal and the combustion conditions are unstable, which is easy to generate sticky large-particle dust with a diameter possibly exceeding 1 cm. The structure of the denitration catalyst is generally honeycomb or plate type, and the spacing or opening thereof can reach 8 mm. When the fly ash particle is larger than the opening of the catalyst, the catalyst is easily blocked, which can cause the service life of the catalyst to be significantly shortened and the denitration effect to be greatly reduced. The accumulated large-particle dust not only blocks the catalyst in a large area, but also causes the flue gas flow field distribution in the denitration reactor to be uneven, the local flue gas flow rate to be too fast, the catalyst to be worn and collapsed, and the SCR denitration system to be abnormally operated, and even safety production accidents can be caused. SUMMARY

[0004] The purpose of the present application is to provide an SCR denitration system which can intercept large-particle sticky dust, effectively prevent the denitration device from being blocked, and thus ensure the safe and stable operation of the system.

[0005] In order to solve the above technical problems, the present application provides an SCR denitration system, which comprises an economizer, a flue, a denitration device and an interception assembly. The top of the economizer is provided with an air inlet, and the bottom side of the economizer is provided with an air outlet. The flue gas inlet end of the flue is connected to the air outlet of the economizer. The denitration device is installed in the flue. The interception assembly is arranged at the air outlet and comprises a vibrator and an interception part. The interception part covers the air outlet and comprises an interception screen and a baffle connected in sequence from top to bottom. The vibrator can drive the interception part to vibrate so as to shake off the dust deposited on the interception part.

[0006] Further, the SCR denitration system further comprises a pressure detection device capable of detecting pressure values of the upstream and downstream ends of the interception part respectively, the vibrator is electrically connected with the pressure detection device, and the vibrator is configured to:

[0007] obtain the pressure values detected by the pressure detection device;

[0008] when the pressure value of the upstream end of the interception part is greater than the pressure value of the downstream end of the interception part, the vibrator is started, and the vibration frequency and power are automatically adjusted according to the difference between the pressure value of the upstream end of the interception part and the pressure value of the downstream end of the interception part.

[0009] Further, the interception filter screen is in a wave shape.

[0010] Further, the interception filter screen comprises a plurality of filter units connected in sequence from top to bottom, the filter units are in a V shape, and the openings of the filter units face the upstream end.

[0011] Further, the filter unit comprises two filter sheets connected at an angle of 60°-90°.

[0012] Further, the height of the baffle is H1, and the height of the exhaust port is H;

[0013] Both satisfy the following relationship: 0.15*H≤H1≤0.25*H.

[0014] Further, the mesh holes of the interception filter screen are in a strip shape, the length of each mesh hole ranges from 15mm to 25mm, and the width of each mesh hole ranges from 5mm to 7mm.

[0015] Let the area of the interception filter screen be a, and the total area of the mesh holes on the interception filter screen be b, which satisfy the following relationship:

[0016] Further, the material of the interception part is a corrosion-resistant metal plate, and the surface of the interception part is coated with a wear-resistant coating. The interception part and the interception filter screen are both made of metal plates, and the material of the interception part and the interception filter screen connected by welding is a corrosion-resistant metal plate, and the surface of the interception part is coated with a wear-resistant coating.

[0017] Further, the denitration device comprises an ammonia injection grid and a denitration catalyst layer arranged in sequence along the flue, and the denitration catalyst layer is arranged downstream of the ammonia injection grid.

[0018] Further, the SCR denitration system further comprises a soot blower installed on the flue for blowing off dust on the denitration catalyst layer.

[0019] Compared with the prior art, an SCR denitrification system according to an embodiment of the present invention has the following beneficial effects: an interception assembly is provided at the position connecting the economizer and the flue, and the interception assembly includes an interception part and a vibrator, the interception part includes a through-port that is sequentially connected and sealed from top to bottom, and the vibrator is used to drive the interception part to vibrate; based on this, the dust-laden flue gas first flows from top to bottom through the economizer, and the flow velocity decreases after colliding with the bottom wall of the economizer, and the flow direction is rotated to flow horizontally from the exhaust port to the flue, and under the combined action of the initial velocity and gravity, the large particles of ash in the flue gas are separated by inertia At the exhaust port of the economizer, the distribution of ash particles is that their weight and volume gradually increase from top to bottom, that is, the ash particles are smaller in the upper layer and larger in the lower layer. The dust-laden flue gas is blown onto the interception part, and the interception filter above the interception part is beaten by a vibrator. Even if the flue gas contains sticky dust, the interception filter will hardly be blocked. The baffle at the bottom of the interception part is a solid part, so the large particles of ash in the dust-laden flue gas fall freely after being blown to the baffle. Without affecting the flue gas flow rate, the large particles of dust entering the denitrifier are reduced, thereby improving the denitrification effect of the denitrification device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a front view of an embodiment of the present invention;

[0021] Figure 2 It is a partial enlarged view of the main view of an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of an interception filter according to an embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of a filter unit according to an embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of a filter sheet according to an embodiment of the present invention;

[0025] Figure 6 is a schematic diagram of a vibrator according to an embodiment of the present invention.

[0026] In the figure, 1. economizer; 11. exhaust port; 2. denitrifier; 3. vibrator; 31. magnetic hammer rod; 32. outer shell; 33. pressure plate; 34. base; 35. junction box; 36. coil (not revealed in the figure); 4. interception part; 41. baffle; 42. interception filter; 421. filter unit; 422. filter plate; 5. flue; 51. first cavity; 52. second cavity; 53. third cavity; 54. fourth cavity; 55. first channel; 56. second channel; 57. third channel; 6. ammonia catalytic layer; 7. denitrification catalyst catalytic layer. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application will be further described in conjunction with the drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0028] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "vertical", "horizontal", "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like in the present application are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0029] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "vertical", "horizontal", "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like in the present application are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0030] As shown in Figure 1 and Figure 2 The preferred embodiment of the present application is an SCR denitration system, which comprises an economizer 1, a flue 5, a denitration device 2 and an interception assembly. The economizer 1 has an exhaust port 11 on the side. The inlet of the flue 5 is connected to the exhaust port 11 of the economizer 1. The denitration device 2 is installed in the flue 5. The interception assembly is arranged at the exhaust port 11. The interception assembly comprises a vibrator 3 and an interception part 4. The interception part 4 covers the exhaust port 11. The interception part 4 comprises an interception filter screen 42 and a baffle 41 connected in sequence from top to bottom. The vibrator 3 can drive the interception part 4 to vibrate, so as to shake off the dust deposited on the interception part 4.

[0031] The working process of the SCR denitration system of the application is as follows: the dust-containing flue gas flows from the upper gas inlet to the lower of the economizer 1, and the speed of the flue gas is reduced after the collision, and the flue gas flows out from the exhaust port 11 of the economizer 1. Since the flue gas flows from the economizer 1 to the flue 5, the flow direction of the flue gas is rotated, and under the joint action of the initial speed and gravity, the large particles of ash in the flue gas are separated out by inertia, and at the exhaust port 11 of the economizer 1, the ash particles are from top to bottom, the ash particles are from low to high in weight, and since the weight of the ash particles is proportional to the volume of the ash particles, that is, the volume of the ash particles is from small to large. The application sets the intercepting part 4, and the baffle 41 of the lower part of the intercepting part 4 blocks the ash particles with large volume and large influence on the catalytic layer outside the exhaust port 11, preventing the large particles of ash from entering the flue 5 and avoiding affecting the performance of the catalyst in the SCR denitration system. If the baffle 41 is separately provided to block the large particles of ash, but a part of the ash will still enter the flue 5 from above the baffle 41, so the application further provides the intercepting filter screen 42, which blocks the remaining ash outside the flue 5. Compared with the filter screen provided alone, the application provides the vibrator 3 on the intercepting filter screen 42, and the vibrator 3 continuously vibrates the intercepting filter screen 42 to prevent the large particles of ash with viscosity from blocking the mesh holes of the intercepting filter screen 42. The application effectively reduces the large particles of ash entering the flue, effectively prevents the denitration device from being blocked, and ensures the safe and stable operation of the SCR denitration system.

[0032] Preferably, the SCR denitration system of some embodiments further comprises: a pressure detection device capable of detecting the pressure values of the upstream and downstream ends of the intercepting part 4 respectively, and the vibrator 3 is electrically connected with the pressure detection device, and the vibrator 3 is configured to:

[0033] obtain the pressure values detected by the pressure detection device;

[0034] when the pressure value of the upstream end of the intercepting part 4 is greater than the pressure value of the downstream end of the intercepting part 4, the vibrator 3 is started, and the vibration frequency and power are automatically adjusted according to the difference between the pressure value of the upstream end of the intercepting part 4 and the pressure value of the downstream end of the intercepting part 4, when the pressure difference is large, it indicates that the blockage is more serious, at this time the vibration frequency and vibration intensity output by the vibrator can be automatically increased.

[0035] For example, the pressure detection device comprises a pressure sensor, and the pressure sensor is arranged at the upstream end of the intercepting part 4 and the downstream end of the intercepting part 4 respectively. Figure 6As shown, the vibrator 3 includes a magnetic hammer 31, a shell 32, a pressing plate 33 and a base 34. The magnetic hammer 31 is sleeved with the shell 32, and slides up and down relative to the shell 32 in the vertical direction. The shell 32 is externally provided with a junction box 35, and a coil is arranged in the shell 32. The junction box 35 is internally provided with a wire connected to the coil, so as to generate a magnetic field after the coil is electrified. The magnetic hammer 31 is lifted under the action of the magnetic field, and freely falls and vibrates the intercepting part 4 under the action of gravity after being de-energized. The shell 32 is fixedly connected to the pressing plate 33 by a fixing member, the pressing plate 33 is fixedly connected to the top of the base 34, and the bottom of the base 34 is fixedly connected to the intercepting part 4. When the pressure difference value increases, the vibrator 3 increases the intensity of the coil electrification to generate a larger magnetic field, and the magnetic hammer 31 is lifted to a higher height. After being de-energized, the vibration intensity generated by the free fall of the magnetic hammer 31 also increases. The relative position between the magnetic hammer 31 and the shell 32 is not affected by the thermal expansion and contraction of the economizer 1 outlet and the flue 5, and the stress effect of the magnetic hammer 31 will not change with environmental factors, so it is suitable for the temperature range of 290-410°C of the SCR system reaction in the application.

[0036] The SCR denitration system in some embodiments of the application is provided with a plurality of vibrators 3, which can be set to vibrate simultaneously or in sequence according to the needs of on-site construction. The plurality of vibrators 3 can better vibrate out the dust stuck at any position from one end to the other end of the intercepting filter screen 42, further improve the interception effect, and hardly affect the flow rate of flue gas. The pressure difference between the upstream and downstream ends of the intercepting part 4 is within a reasonable range to avoid causing problems of non-safe and stable operation of the system.

[0037] As shown in Figure 3 Preferably, the intercepting filter screen 42 is in a wave shape. Compared with the planar intercepting filter screen 42, the wave-shaped intercepting filter screen 42 further increases the interception area, so that the effect of intercepting and filtering large-particle dust is better. Large-particle dust hits the convex part of the wave-shaped intercepting filter screen 42, and since this part is the stopping point of the speed of large-particle dust, the large-particle dust loses momentum and freely falls into the ash bucket below the economizer 1. Therefore, the wave-shaped intercepting filter screen 42 has the advantages of wear resistance, low pressure loss and long service life.

[0038] As shown in Figure 4As shown, the intercepting filter 42 preferably includes a plurality of filter units 421 connected sequentially from top to bottom. The filter units 421 are V-shaped, and the openings of the filter units 421 face the upstream end. One filter unit 421 includes two filter plates 422, one end of which is fixedly connected, and the angle between the two filter plates 422 is 60° to 90°. When large ash particles hit the filter plates 422, they will converge toward the top along the filter plates 422. Since the top of the filter unit 421 is the velocity stagnation point, the convergence effect is better, and the large ash particles will lose momentum and more easily fall freely into the ash hopper below the economizer 1.

[0039] Preferably, the height of the baffle 41 is H1, and the height of the exhaust port 11 is H; the two satisfy the following relationship: 0.15*H≤H1≤0.25*H. The baffle 41 can prevent large dust particles from entering the denitrifier 2, and compared to the interception filter 42, the baffle 41 does not have the problem of mesh clogging. However, if the height of the baffle 41 is too high, the flow rate of the flue gas will be significantly reduced, affecting the operating efficiency of the denitrifier 2. If the height of the baffle 41 is too low, it will not be effective in intercepting large dust particles in the flue gas. Taking these two points into consideration, the best embodiment of the present application sets the height of the baffle 41 to: H1 = 0.2*H.

[0040] like Figure 5 As shown, preferably, the opening structure of the intercepting filter 42 adopts a rectangular mesh structure, and the length of the rectangular mesh structure ranges from 15 mm to 25 mm and the width ranges from 5 mm to 7 mm.

[0041] Assuming the area of ​​the interception filter 42 is a, and the total area of ​​the mesh holes of the interception filter 42 is b, the following relationship is satisfied: The interception filter 42 primarily intercepts large dust particles larger than 10 mm, which pose a significant threat to the denitrification catalyst layer 7. Compared to circular meshes, the rectangular mesh structure is less susceptible to clogging by irregularly shaped large dust particles and provides more free space. Furthermore, the staggered arrangement of the rectangular meshes offers improved mechanical properties, ensuring effective dust interception without affecting the flue gas flow rate or excessive pressure differentials within the SCR denitrification system, thus ensuring stable and safe operation of the SCR denitrification system.

[0042] Preferably, the interception portion 4 is made of an anti-corrosion metal plate and coated with a wear-resistant coating. This further extends the service life of the interception portion 4, avoids frequent shutdowns and maintenance during subsequent use of the SCR denitration system, and improves the overall efficiency of the SCR denitration system.

[0043] For example, in one embodiment of the present invention, the bottom of the intercepting filter 42 is preferably welded to the top of the baffle 41. This further improves the mechanical properties of the intercepting filter 42 and the baffle 41. Furthermore, welding is more suitable for the high-temperature environment at the outlet of the economizer 1 than bonding, and is less prone to failure and has better durability.

[0044] Preferably, the flue 5 comprises a first cavity 51, a second cavity 52, a third cavity 53 and a fourth cavity 54, the first cavity 51 is fixedly connected to the exhaust port 11 of the economizer 1 in a horizontal direction, the second cavity 52 extends in a vertical direction, the second cavity 52 is fixedly connected to the first cavity 51 through a first channel 55, the third cavity 53 extends in a horizontal direction, the third cavity 53 is fixedly connected to the second cavity 52 through a second channel 56, the fourth cavity 54 extends in a vertical direction, and the third cavity 53 is fixedly connected to the fourth cavity 54 through a third channel 57. The denitrator 2 comprises an ammonia gas catalytic layer 6 and a denitration catalyst catalytic layer 7, the ammonia gas catalytic layer 6 is arranged in the second cavity 52 in a horizontal direction, and the denitration catalyst catalytic layer 7 is arranged in the fourth cavity 54 in a horizontal direction. The ammonia gas catalytic layer 6 sprays ammonia gas, flue gas enters the second cavity 52 from bottom to top, and then enters the second channel 56, the third cavity 53 and the third channel 57 in sequence, in this process, the ammonia gas and the flue gas are fully mixed and uniformly distributed, and then pass through the denitration catalyst catalytic layer 7 of the fourth cavity 54 from top to bottom. The principle of SCR denitration refers to a nitrogen oxide emission reduction technology in which a reducing agent NH3 (ammonia gas) is selectively reduced into non-polluting N2 (nitrogen gas) under the action of a catalyst in a temperature range of 290-410 DEG C.

[0045] Further, in the denitrator 2, the ammonia gas catalytic layer 6 and the denitration catalyst catalytic layer 7 are arranged perpendicularly to the extension direction of the corresponding cavities, the area of the flue gas flowing through the ammonia gas catalytic layer 6 and the denitration catalyst catalytic layer 7 is the maximum, the flue gas is fully contacted with the catalytic layer, and the denitration effect is better.

[0046] Further, in some embodiments of the present application, two denitration catalyst catalytic layers 7 are arranged in parallel, so that the denitration effect is further improved.

[0047] Preferably, the SCR denitration system in some embodiments of the present application further comprises a soot blower installed on the flue for blowing off dust on the denitration catalyst catalytic layer. The dust removal effect of the denitration catalyst catalytic layer is further improved, the denitration effect is improved, and the safe and stable operation of the system is further ensured.

[0048] Further, in some embodiments of the present application, the soot blower is preferably a telescopic steam soot blower, and in some embodiments of the present application, a sound wave soot blower is selected, which can achieve the above-mentioned effect, and is not limited herein.

[0049] In summary, the embodiments of the present application provide an SCR denitration system, which intercepts dust in the dust-containing flue gas entering the flue gas inlet end through the arrangement of the interception assembly, effectively prevents the denitrator from being blocked, and ensures the safe and stable operation of the system.

[0050] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and replacements can be made without departing from the technical principles of the present application, and these improvements and replacements should also be considered as the protection scope of the present application.

Claims

1. An SCR denitrification system, characterized in that: include: An economizer, a flue, a denitrifier, and an interception assembly, wherein the economizer is provided with an air inlet at the top, an exhaust port at the bottom side of the economizer, a flue gas inlet end of the flue being connected to the exhaust port of the economizer, the denitrifier being installed in the flue, and the interception assembly being provided at the exhaust port, the interception assembly comprising a vibrator and an interception portion, the interception portion covering the exhaust port, the interception portion comprising an interception filter and a baffle connected in sequence from top to bottom, the vibrator being capable of driving the interception portion to vibrate to shake off dust deposited on the interception portion; The device comprises a pressure detection device capable of detecting pressure values ​​at the upstream and downstream ends of the interception portion, respectively; the vibrator is electrically connected to the pressure detection device, and the vibrator is configured to: Obtaining a pressure value detected by the pressure detection device; When the pressure value at the upstream end of the interception portion is greater than the pressure value at the downstream end of the interception portion, the vibrator is activated and automatically adjusts the vibration frequency and power according to the difference between the pressure value at the upstream end of the interception portion and the pressure value at the downstream end of the interception portion, and the interception filter becomes wavy; Let the height of the baffle be H1, and let the height of the exhaust port be H; The two satisfy the following relationship: 0.15*H≤H1≤0.25*H.

2. The SCR denitration system according to claim 1, characterized in that: The intercepting filter screen includes a plurality of filter units connected sequentially from top to bottom, wherein the filter units are V-shaped and the openings of the filter units face the upstream end of the intercepting portion.

3. The SCR denitration system according to claim 2, characterized in that: The filter unit comprises two filter plates connected at an angle of 60° to 90°.

4. The SCR denitration system according to claim 1, characterized in that: The mesh of the intercepting filter is in the shape of a long strip, the length of each mesh ranges from 15 mm to 25 mm, and the width of each mesh ranges from 5 mm to 7 mm; Assume that the area of ​​the intercepting filter is a, and the total area of ​​the meshes on the intercepting filter is b, and the following relationship is satisfied:

5. The SCR denitration system according to claim 1, characterized in that: The baffle and the intercepting filter are both made of metal plates, and are connected to each other by welding. The surfaces of the baffle and the intercepting filter are coated with a wear-resistant coating.

6. The SCR denitration system according to claim 1, characterized in that: The denitrifier comprises an ammonia injection grid and a denitrification catalyst layer which are sequentially arranged along the flue, and the denitrification catalyst layer is arranged downstream of the ammonia injection grid.

7. The SCR denitration system according to claim 6, characterized in that: It also includes a soot blower, which is installed on the flue and is used to blow away dust on the catalytic layer of the denitration catalyst.

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