First-layer catalyst inlet sub-zone negative pressure fly ash extraction device for scr and reactor

Abstract

The application discloses an SCR first-layer catalyst inlet partition negative pressure fly ash extraction type fly ash capturing device and a reactor, and the capturing device comprises an inlet bearing frame, an inertial fly ash capturing unit, a partition negative pressure fly ash extraction pipe group, an anti-back-dust fly ash collecting box, a secondary flow uniformizing plate and a fly ash extraction control unit. The inlet bearing frame is divided into a plurality of fly ash extraction control partitions according to the ash particle distribution characteristics of the flue gas inlet section. The inertial fly ash capturing unit comprises a fly ash meeting guide plate and a narrow-slot fly ash capturing groove arranged in the low-speed area of the leeward side of the fly ash meeting guide plate. The narrow-slot fly ash capturing groove is communicated with the fly ash extraction channel through a stable-pressure fly ash collecting cavity, and a pressure-equalizing orifice plate is arranged in the stable-pressure fly ash collecting cavity. The partition negative pressure fly ash extraction pipe group is provided with an independent adjusting valve corresponding to each partition. The fly ash extraction control unit adjusts the opening degree of each independent adjusting valve according to the fly ash capturing state and the operation condition of the unit. The anti-back-dust fly ash collecting box is used for isolating the captured fly ash when the negative pressure is reduced. The secondary flow uniformizing plate is used for compensating the speed disturbance caused by the fly ash extraction. The application can realize the partition differential capturing and active extraction of large-particle fly ash.

Description

Technical Field

[0001] This application belongs to the technical field of wear prevention and fly ash treatment of flue gas denitrification equipment for coal-fired units, and specifically relates to a fly ash collection device and reactor with partitioned negative pressure ash extraction at the inlet of the first layer catalyst of SCR. Background Technology

[0002] Selective catalytic reduction (SCR) flue gas denitrification technology is the mainstream process for controlling nitrogen oxide emissions in coal-fired power plants. Due to economic and space constraints, most coal-fired unit SCR denitrification devices adopt a "high temperature and high dust" layout, with the reactor placed between the economizer and the air preheater, and the catalyst operating directly in a high-concentration fly ash environment.

[0003] Large particulate fly ash in coal-fired flue gas (commonly known as "popcorn ash," with particle sizes reaching millimeters or even larger than 10 mm) is a significant cause of accelerated deactivation of SCR catalysts. These large particles have high inertia, easily forming flow deviation channels and localized accumulations at flue bends, the rear edge of guide vanes, and the reactor sidewalls. After long-term operation, these large particles continuously erode the inlet face of the first-layer catalyst, causing erosion of the catalyst channel edges, increased local pressure differentials, and in severe cases, catalyst layer blockage. Studies also show that the fly ash concentration distribution at the SCR inlet cross-section is extremely uneven—dust concentrations in areas such as the outer side of flue bends and the reactor front wall are often several times higher than the cross-sectional average.

[0004] Currently, passive interception methods such as wear-resistant grids and interception nets are mainly used. However, the large particles of ash that are intercepted still remain in the flue gas passage and are easily re-entrained into the catalyst channels when the unit load fluctuates. Although some solutions introduce the concept of negative pressure suction, they lack the ability to treat different areas and effective ash return isolation measures. Furthermore, there is a lack of compensation for the disturbance to the catalyst inlet flow field caused by local ash suction. Summary of the Invention

[0005] The purpose of this application is to provide a zoned negative pressure fly ash collection device and reactor for the inlet of the first-layer catalyst in a SCR system. This addresses the problems mentioned in the background art, such as the lack of zoned differentiated collection, active extraction, and ash return isolation capabilities for large fly ash particles before the inlet of the first-layer catalyst, and the disturbance of the catalyst inlet flow field caused by localized ash extraction, which in turn affects denitrification efficiency.

[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, a negative pressure fly ash collection device with partitioned ash extraction at the inlet of the first-stage catalyst in a SCR system is provided, which is installed inside the shell of the SCR denitrification reactor of a coal-fired power unit and located above the first-stage denitrification catalyst module, comprising: An inlet support frame is provided across the flue gas passage of the SCR denitrification reactor shell, and the inlet support frame is divided into multiple ash extraction control zones according to the ash particle distribution characteristics of the flue gas inlet section. Multiple inertial ash collection units are installed on the inlet support frame. Each inertial ash collection unit includes an ash guide plate and a narrow slit ash collection trough located in the low-speed zone on the leeward side of the ash guide plate. The narrow slit ash collection trough is connected to the ash extraction channel through a pressure-stabilizing ash collection chamber. The pressure-stabilizing ash collection chamber is equipped with a pressure equalization plate to balance the extraction volume of the multiple narrow slit ash collection troughs. The partitioned negative pressure ash extraction pipe group is connected to the ash extraction channel in each ash extraction control zone, and each ash extraction control zone is equipped with an independent regulating valve. The ash extraction control unit has its signal input terminal connected to a first detection component for detecting the ash collection status of each ash extraction control zone and a second detection component for detecting the unit's operating conditions. Its signal output terminal is connected to each independent regulating valve. The ash extraction control unit adjusts the opening degree of each independent regulating valve according to the ash collection status and the unit's operating conditions, and limits the rate of change of the opening degree of the corresponding independent regulating valve when the denitrification reaction parameters fluctuate beyond a preset range. The anti-backflow ash collection box is located on the outlet side of the partitioned negative pressure ash extraction pipe group and is used to isolate the captured fly ash outside the main flue gas channel when the suction negative pressure decreases or a reverse pressure difference occurs. A secondary flow equalization plate is installed on the downstream side of the inlet support frame to compensate for the flue gas velocity distribution disturbance caused by the partitioned negative pressure ash extraction.

[0007] In one possible implementation, the ash extraction control zone of the inlet support frame is determined based on the ash flux matrix of the flue gas inlet section. The ash flux matrix is ​​calculated by the dust content of the inlet section grid sampling, the grid flue gas velocity, and the weight of large ash particle size. Regions where the ash flux is higher than the average ash flux of the section, regions where the ash flux gradient exceeds the average gradient of adjacent grids, or regions near the outside of the flue bend, the reactor sidewall, or the area with heavy historical wear of the first-layer denitrification catalyst module are classified into the enhanced ash extraction control zone.

[0008] In one possible implementation, the angle of inclination of the ash-facing guide plate relative to the mainstream direction of flue gas is 25° to 45°, and a replaceable wear-resistant strip is provided on its ash-facing side. The replaceable wear-resistant strip is connected to the ash-facing guide plate by a pressure plate, dovetail groove or bolts.

[0009] In one possible implementation, the ratio λ of the slot width Wc of the ash collection trough to the hydraulic width Bh of the adjacent main flow zone is 4% to 15%, where λ = Wc / Bh; the lower limit of the ratio λ is determined based on the minimum lateral suction flow and anti-clogging flow area required for large fly ash particles to enter the slot, and the upper limit of the ratio λ is determined based on the allowable air extraction ratio, the inlet velocity deviation of the first-layer denitrification catalyst module, and the limit of ammonia injection mixing disturbance.

[0010] In one possible implementation, the pressure equalizing orifice plate includes multiple orifice segments arranged along the length of the ash extraction channel. The orifice segments near the negative pressure inlet of the ash extraction channel are provided with throttling holes or a smaller orifice ratio, while the orifice segments far from the negative pressure inlet are provided with a larger orifice ratio.

[0011] In one possible implementation, the anti-backflow ash collection box includes an expansion settling section, a labyrinth baffle section, and a one-way flap section connected in sequence. The flow area of ​​the expansion settling section is larger than the flow area of ​​the corresponding ash extraction channel. The labyrinth baffle section is provided with staggered baffles. The flap closing direction of the one-way flap section is opposite to the direction of the backflow ash airflow.

[0012] In one possible implementation, the ash extraction channel is an ash extraction branch pipe, which is equipped with a pressure measuring point and a purging interface. The purging interface is used to reverse purge the pressure-stabilizing ash collection chamber when the machine is stopped, under maintenance, or when the pressure difference of the ash extraction branch pipe increases abnormally.

[0013] In one possible implementation, the ash extraction control unit determines the adjustment state of the independent regulating valve according to the partitioned ash extraction trigger value S, which is obtained by weighting the normalized differential pressure increase before and after the ash collection tank, the increase in dust content at the SCR inlet, and the boiler load change rate. When S reaches the enhanced ash extraction threshold, the opening degree of the independent regulating valve in the corresponding ash extraction control zone is increased. When the NOx or ammonia escape fluctuation at the SCR outlet exceeds the preset range, the rate of change of the opening degree of the independent regulating valve in the adjacent ash extraction control zone is limited. When the differential pressure measuring points before and after the ash collection tank fail, the dust content signal at the SCR inlet is invalid, or the differential pressure in the ash extraction branch pipe increases abnormally, the opening rate of the corresponding independent regulating valve is maintained or reduced, and a purging or maintenance prompt is issued.

[0014] In one possible implementation, the secondary flow equalization plate has compensation openings with a higher opening ratio than other areas in the downstream projection area of ​​the ash extraction channel. The compensation openings are arranged in groups along the downstream projection area of ​​the ash extraction channel, and the opening ratio of the compensation openings is determined according to the designed ash extraction volume of the corresponding ash extraction control zone.

[0015] Secondly, this application also provides an SCR denitrification reactor, including the SCR first-layer catalyst inlet partition negative pressure ash extraction fly ash collection device described in any of the above claims.

[0016] Compared with the prior art, this application has the following beneficial effects: This application provides a zoned negative pressure fly ash collection device for the inlet of the first-layer catalyst in a SCR system. The device divides the fly ash collection control zones according to the ash particle distribution characteristics of the flue gas inlet cross-section using an inlet support frame. This enables enhanced fly ash collection in areas rich in large-particle fly ash and reduces unnecessary air extraction in low-ash flux areas, achieving differentiated treatment by zone. By placing a narrow-slit fly ash collection trough in the low-speed zone on the leeward side of the fly ash guide plate, the high inertia of large-particle fly ash is utilized to deflect them into the trough, achieving selective collection of high-inertia particles and avoiding excessive extraction of small-diameter fly ash. The pressure equalization orifice plate within the pressure-stabilizing ash collection chamber evens out the pressure of the fly ash collected in the same ash collection channel. By utilizing the suction capacity of multiple narrow-slit ash collection troughs, the problem of uneven suction caused by differences in pipeline resistance is overcome. The ash collection control unit adjusts the opening of independent regulating valves in each zone according to the ash collection status and unit operating conditions, and limits the valve change rate when denitrification reaction parameters fluctuate, achieving adaptive intelligent control of the ash collection process and avoiding impact on denitrification efficiency. The anti-backflow ash collection box isolates the collected fly ash outside the main flue gas channel when the suction negative pressure decreases or a reverse pressure differential occurs, eliminating backflow. The secondary flow equalization plate compensates for the flue gas velocity distribution disturbance caused by zoned negative pressure ash collection, ensuring the stability of the inlet flow field of the first-layer catalyst. These structures work together synergistically to achieve a complete treatment chain for large-particle fly ash, from deflection collection to balanced suction, intelligent control, anti-backflow isolation, and flow field compensation, effectively reducing the risk of wear and blockage of the first-layer catalyst.

[0017] In one possible implementation, the ash extraction control zone is determined by the ash particle flux matrix. Areas with ash particle flux higher than the average cross-sectional value, areas with gradients exceeding the average gradient of adjacent grids, or areas with heavy historical wear are included in the enhanced ash extraction control zone. This provides a quantitative basis for the division of the zone boundaries and avoids over-extraction or under-extraction caused by subjective division.

[0018] In one possible implementation, by setting the tilt angle of the ash-facing guide vane to 25° to 45°, both the deflection efficiency of large fly ash particles and the flow resistance of flue gas are taken into account; by setting replaceable wear-resistant strips on the ash-facing side, the service life of the guide vane under the scouring of dusty flue gas is extended, and the maintenance cost is reduced.

[0019] In one possible implementation, by limiting the ratio λ of the slit ash trap opening width to the hydraulic width of the adjacent main flow zone to 4% to 15%, the required lateral suction flow and anti-clogging flow area for large fly ash particles to enter the slit opening are ensured, while the adverse effects of the extraction ratio on catalyst inlet velocity deviation and ammonia injection mixing are controlled. Moreover, this dimensionless ratio allows the design to be scaled up for different capacity units, exhibiting good universality.

[0020] In one possible implementation, a pressure equalizing orifice plate is segmented along the length of the ash extraction channel with different orifice ratios—throttling at the near end and enlarged orifices at the far end. This simple orifice plate structure achieves a balanced distribution of the suction volume of multiple ash collection points within the same ash extraction channel. The structure is simple, highly reliable, and avoids the increased costs and maintenance difficulties caused by adding complex flow regulation devices.

[0021] In one possible implementation, the flow velocity of the air-ash mixture is reduced by the expansion and settling section of the anti-backflow ash collection box, the backflow ash-carrying capacity is weakened by the labyrinth baffle section, and the one-way flap section is automatically closed when the negative pressure decreases or the pressure difference reverses. The three-section structure works together to achieve multiple isolation of the collected fly ash under conditions such as negative pressure fluctuations and shutdown, thus structurally ensuring a one-way ash conveying path of "only out, no in".

[0022] In one possible implementation, by setting pressure measuring points and purging interfaces on the ash extraction branch pipes, the working status of each branch pipe can be monitored during operation, and reverse purging can be performed when the machine is stopped or the pressure difference is abnormal. Combined with the fault identification logic of the ash extraction control unit, a closed-loop maintenance link of monitoring-judgment-purging-prompt is formed, which improves the maintainability and operational reliability of the device.

[0023] In one possible implementation, the incremental pressure difference before and after the ash collection tank, the incremental dust content at the SCR inlet, and the boiler load change rate are normalized and weighted by using the partitioned ash collection trigger value S. When the outlet NOx or ammonia escape fluctuates, the valve change rate is limited, so that the ash collection control responds to the changes in ash collection demand and takes into account the stability of the denitrification reaction, avoiding fluctuations in denitrification efficiency caused by sudden changes in ash collection.

[0024] In one possible implementation, a secondary flow equalization plate is used to set a compensation opening with a higher opening ratio than other areas in the downstream projection area of ​​the ash extraction channel. The opening ratio is determined according to the designed ash extraction volume of the corresponding zone, which realizes precise compensation for local velocity loss. This allows the collection device to improve the removal capacity of large ash particles while maintaining the uniformity of the catalyst inlet velocity distribution.

[0025] An SCR denitrification reactor, including the aforementioned collection device, can also achieve the technical effects of zoned differentiated ash collection, active extraction, intelligent control, backflow prevention and isolation, and flow field compensation, thereby effectively extending the service life of the first-layer catalyst, reducing the operating resistance of the denitrification system, and improving the operational reliability of the unit under deep peak shaving and high-ash coal co-firing conditions. Attached Figure Description

[0026] Figure 1 A schematic diagram of the overall layout of a SCR first-layer catalyst inlet zoned negative pressure fly ash collection device in an SCR reactor, provided for this application; Figure 2A partial structural diagram of the inertial ash collection unit, narrow slit ash collection trough, pressure-stabilizing ash collection chamber, and partitioned negative pressure ash extraction pipe group in an SCR first-layer catalyst inlet partitioned negative pressure ash extraction fly ash collection device provided in this application; The attached figures are labeled as follows: 10, SCR reactor shell; 20, inlet support frame; 21, inertial ash collection unit; 211, ash guide plate; 212, narrow slit ash collection trough; 213, pressure stabilizing ash collection chamber; 214, replaceable wear-resistant strip; 215, pressure equalization orifice plate; 22, zoned negative pressure ash extraction pipe assembly; 221, ash extraction branch pipe; 222, independent regulating valve; 224, pressure measuring point; 225, purging interface; 23, anti-backflow ash collection box; 231, expansion settling section; 232, labyrinth baffle section; 233, unidirectional flap section; 24, secondary flow equalization plate; 30, first-layer denitrification catalyst module; 40, ash extraction control unit. Detailed Implementation

[0027] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0028] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application.

[0029] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly defined. The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," 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, an electrical connection, or a communication 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. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] like Figure 1 and Figure 2 As shown, this application discloses a fly ash collection device with partitioned negative pressure at the inlet of the first-layer catalyst of an SCR, which is installed inside the shell 10 of the SCR denitrification reactor of a coal-fired unit and located above the first-layer denitrification catalyst module 30.

[0034] In this embodiment, the inlet support frame 20 is installed inside the SCR reactor shell 10 and located above the first-layer denitrification catalyst module 30. The inlet support frame 20 can be connected to the reactor inner wall or support beam, and its installation position is preferably within 0.3m to 1.5m above the inlet end face of the first-layer denitrification catalyst module 30, so as to take into account both ash collection space and maintenance space.

[0035] In one possible embodiment, the inlet support frame 20 is divided into multiple ash extraction control zones according to the ash particle distribution characteristics of the flue gas inlet cross-section. For areas near the outer side of the flue bend, the reactor sidewall, or areas with heavy historical wear, the spacing of the inertial ash collection units 21 can be smaller than the spacing in the middle region of the inlet cross-section. This non-uniform arrangement can increase the ash collection capacity in high ash flux areas while avoiding excessive increase in the overall inlet cross-section resistance.

[0036] In this embodiment, each inertial ash collection unit 21 includes an ash-receiving guide plate 211, a narrow-slot ash-collecting trough 212, and a pressure-stabilizing ash-collecting chamber 213. The narrow-slot ash-collecting trough 212 is arranged in the low-speed zone formed on the leeward side of the ash-receiving guide plate 211, and the upstream lip of the narrow-slot ash-collecting trough 212 is lower than the downstream edge of the ash-receiving guide plate 211. Due to their greater inertia, large particles of fly ash cannot completely change direction with the mainstream flue gas after passing through the ash-receiving guide plate 211, and therefore deviate into the narrow-slot ash-collecting trough 212.

[0037] In one possible embodiment, the angle of inclination of the ash-facing guide plate 211 relative to the mainstream flue gas direction is 25° to 45°. The ash-facing side of the ash-facing guide plate 211 is provided with a replaceable wear-resistant strip 214. The replaceable wear-resistant strip 214 is made of ceramic composite plate, wear-resistant alloy plate or weld overlay plate, and is connected by pressure plate, dovetail groove or bolts, which facilitates replacement during maintenance cycle.

[0038] In one possible embodiment, the ratio λ of the slot width Wc of the ash collection trough 212 to the hydraulic width Bh of the adjacent main flow zone is 4% to 15%, where λ = Wc / Bh. This range can balance the control of ash collection volume and flue gas extraction volume; the bottom of the trough transitions to the pressure-stabilizing ash collection chamber 213 to reduce the amount of fly ash that remains at the edge of the trough and is then carried away again by the mainstream flue gas.

[0039] In this embodiment, the pressure-stabilizing ash collection chamber 213 is connected to the narrow-slot ash collection trough 212 and to the ash extraction channel via a pressure-equalizing orifice plate 215. The pressure-equalizing orifice plate 215 is segmented along the length of the ash extraction channel. The segments near the negative pressure inlet of the ash extraction channel can use a smaller opening ratio or throttling orifices, while the segments farther from the negative pressure inlet can use a larger opening ratio, so that the multiple narrow-slot ash collection troughs 212 connected to the same ash extraction channel have similar suction volumes. The bottom of the pressure-stabilizing ash collection chamber 213 can be provided with a guide slope inclined towards the ash extraction channel to reduce deposition dead zones.

[0040] In this embodiment, the partitioned negative pressure ash extraction pipe group 22 includes multiple ash extraction channels (ash extraction branch pipes 221), each ash extraction branch pipe 221 being connected to at least one pressure-stabilized ash collection chamber 213 within an ash extraction control partition. The ash extraction branch pipe 221 is equipped with an independent regulating valve 222, a pressure measuring point 224, and a purging interface 225.

[0041] In one possible embodiment, the ash extraction control unit 40 adjusts the opening of the independent regulating valve 222 according to the dust content at the SCR inlet, the pressure difference before and after the ash collection tank, and the boiler load change rate: when the pressure difference before and after the ash collection tank of a certain zone increases, and the dust content at the SCR inlet or the boiler load change rate increases synchronously, the opening of the independent regulating valve 222 of that zone is increased; when the NOx or ammonia escape fluctuation at the SCR outlet exceeds the preset range, the opening rate of the independent regulating valve 222 of the adjacent ash extraction control zone is limited.

[0042] In this embodiment, the anti-backflow ash collection box 23 is located downstream of the partitioned negative pressure ash extraction pipe group 22, and includes an expansion settling section 231, a labyrinth baffle section 232, and a one-way flap section 233 connected in sequence. After the fly ash enters the expansion settling section 231, its flow velocity decreases and it settles. The labyrinth baffle section 232 weakens the backflow of air and ash through staggered baffles. The one-way flap section 233 closes when the negative pressure of the partitioned negative pressure ash extraction pipe group 22 decreases or a reverse pressure difference occurs. The anti-backflow ash collection box 23 may also be equipped with an ash level detector and an ash discharge interface for connection to the plant's ash conveying system.

[0043] In this embodiment, a secondary flow equalization plate 24 is provided on the downstream side of the inlet support frame 20. The secondary flow equalization plate 24 has compensation openings with a higher opening ratio in the downstream projection area corresponding to the ash extraction branch pipe 221, and openings with a lower opening ratio in other areas. The opening ratio of the compensation openings can be determined according to the designed ash extraction volume of the corresponding ash extraction control zone, and is used to compensate for the velocity loss caused by local ash extraction, so as to keep the flue gas velocity distribution entering the first-layer denitrification catalyst module 30 stable.

[0044] In one possible embodiment, under high-ash coal operating conditions, an ash flux matrix can be pre-established based on SCR inlet grid sampling, online dust content measurement, or historical wear distribution. The number of ash extraction control zones can be determined according to the number of module columns of the first-layer denitrification catalyst module 30, the allowable coverage width of the ash extraction branch pipe 221, and the location of the maintenance passage.

[0045] In one possible embodiment, the ash extraction control unit 40 can calculate the ash extraction trigger value S for each ash extraction control zone. S can be determined by S=a·ΔP*+b·C*+c·R*, where ΔP* is the normalized value of the pressure difference increment before and after the ash extraction tank, C* is the normalized value of the dust content increment at the SCR inlet, R* is the normalized value of the boiler load change rate, and a, b, and c are non-negative weights with a+b+c=1. Each normalized value is determined based on the effective range of the corresponding measuring point, the historical stable operating range, or the calibration range during the commissioning period. When S reaches the enhanced ash extraction threshold, the opening degree of the corresponding independent regulating valve 222 is increased. When the NOx or ammonia escape fluctuation at the SCR outlet exceeds the preset range, the opening change rate of the independent regulating valve 222 of the adjacent zone is limited. If the pressure difference measuring point before and after the ash extraction tank fails, the dust content signal at the SCR inlet is invalid, or the pressure difference of the ash extraction branch pipe 221 increases abnormally, the ash extraction control unit 40 does not expand the valve opening change permission for the corresponding zone and prompts for inspection or purging.

[0046] In one possible embodiment, during maintenance or shutdown, reverse purging can be performed on the pressure-stabilizing ash collection chamber 213 and the narrow-slot ash collection trough 212 via the purging interface 225. Before reverse purging, the independent regulating valve 222 corresponding to the ash extraction branch pipe 221 is placed in an isolation or limit state, and the one-way flap section 233 is closed to prevent fly ash deposited in the anti-backflow ash collection box 23 from being blown back into the flue gas passage. After purging, the ash extraction control unit 40 can determine whether there is a blockage in the narrow-slot ash collection trough 212 based on the recovery status of the pressure measuring point 224; if the pressure difference still has not recovered to the allowable range, the opening of this zone is kept at a low degree and a maintenance prompt is issued.

[0047] In one possible embodiment, for units of different capacities, the number of inertial ash collection units 21 can be adjusted according to the number of module rows of the first-layer denitrification catalyst module 30, the width of the flue gas inlet cross-section, and the arrangement of maintenance passages. The above adjustments do not change the coordination relationship between the ash guide plate 211, the narrow slit ash collection trough 212, the pressure stabilizing ash collection chamber 213, the zoned negative pressure ash extraction pipe group 22, and the anti-backflow ash collection box 23.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A fly ash collection device with partitioned negative pressure at the inlet of the first-layer catalyst in a SCR system, installed inside the shell (10) of the SCR denitrification reactor of a coal-fired power unit and located above the first-layer denitrification catalyst module (30), characterized in that, include: An inlet support frame (20) is provided across the flue gas passage of the SCR denitrification reactor shell (10), and the inlet support frame (20) is divided into multiple ash extraction control zones according to the ash particle distribution characteristics of the flue gas inlet section; Multiple inertial ash collection units (21) are installed on the inlet support frame (20). Each inertial ash collection unit (21) includes an ash guide plate (211) and a narrow slit ash collection trough (212) installed in the low-speed zone on the leeward side of the ash guide plate (211). The narrow slit ash collection trough (212) is connected to the ash extraction channel through a pressure-stabilizing ash collection chamber (213). The pressure-stabilizing ash collection chamber (213) is provided with a pressure equalization orifice plate (215) to balance the suction volume of the multiple narrow slit ash collection troughs (212). The partitioned negative pressure ash extraction pipe group (22) is connected to the ash extraction channel in each ash extraction control zone, and each ash extraction control zone is provided with an independent regulating valve (222). The ash extraction control unit (40) has its signal input terminal connected to a first detection component for detecting the ash collection status of each ash extraction control zone and a second detection component for detecting the unit's operating conditions. Its signal output terminal is connected to each independent regulating valve (222). The ash extraction control unit (40) adjusts the opening degree of each independent regulating valve (222) according to the ash collection status and the unit's operating conditions, and limits the opening change rate of the corresponding independent regulating valve (222) when the denitrification reaction parameters fluctuate beyond the preset range. The anti-backflow ash collection box (23) is set on the outlet side of the partition negative pressure ash extraction pipe group (22) to isolate the captured fly ash outside the main flue gas channel when the suction negative pressure decreases or a reverse pressure difference occurs. The secondary flow equalization plate (24) is located on the downstream side of the inlet support frame (20) and is used to compensate for the flue gas velocity distribution disturbance caused by the negative pressure ash extraction in the partition.

2. The collection device according to claim 1, characterized in that, The ash extraction control zone of the inlet support frame (20) is determined according to the ash particle flux matrix of the flue gas inlet section; The ash flux matrix is ​​calculated from the dust content of the inlet cross-section grid sampling, the grid flue gas velocity and the weight of large ash particle size. Regions where the ash flux is higher than the average ash flux of the cross-section, regions where the ash flux gradient exceeds the average gradient of the adjacent grid, or regions near the outside of the flue bend, the side wall of the reactor, or the area with heavy historical wear of the first layer denitrification catalyst module (30) are classified into the enhanced ash extraction control zone.

3. The collection device according to claim 1, characterized in that, The angle of inclination of the ash-receiving guide plate (211) relative to the mainstream direction of flue gas is 25° to 45°, and a replaceable wear-resistant strip (214) is provided on its ash-receiving side. The replaceable wear-resistant strip (214) is connected to the ash-receiving guide plate (211) by a pressure plate, dovetail groove or bolts.

4. The collection device according to claim 1, characterized in that, The ratio λ of the slot width Wc of the narrow slot ash trap (212) to the hydraulic width Bh of the adjacent main flow zone is 4% to 15%, where λ = Wc / Bh; The lower limit of the ratio λ is determined based on the minimum transverse suction flow and anti-clogging flow area required for large fly ash particles to enter the slot, and the upper limit of the ratio λ is determined based on the allowable air extraction ratio, the inlet velocity deviation of the first-layer denitrification catalyst module (30), and the limit of ammonia injection mixing disturbance.

5. The collection device according to claim 1, characterized in that, The pressure equalizing orifice plate (215) includes multiple orifice segments arranged along the length of the ash extraction channel. The orifice segments near the negative pressure inlet of the ash extraction channel are provided with throttling holes or smaller orifice ratios, while the orifice segments far from the negative pressure inlet are provided with larger orifice ratios.

6. The collection device according to claim 1, characterized in that, The anti-backflow ash collection box (23) includes an expansion settling section (231), a labyrinth baffle section (232), and a one-way flap section (233) connected in sequence. The flow area of ​​the expansion settling section (231) is larger than the flow area of ​​the corresponding ash extraction channel. The labyrinth baffle section (232) is provided with staggered baffles. The flap closing direction of the one-way flap section (233) is opposite to the direction of the backflow ash airflow.

7. The collection device according to claim 1, characterized in that, The ash extraction channel is an ash extraction branch pipe (221). The ash extraction branch pipe (221) is equipped with a pressure measuring point (224) and a purging interface (225). The purging interface (225) is used to purge the pressure-stabilizing ash collection chamber (213) in the opposite direction when the machine is stopped, under maintenance or when the pressure difference of the ash extraction branch pipe (221) increases abnormally.

8. The collection device according to claim 1, characterized in that, The ash extraction control unit (40) determines the adjustment state of the independent regulating valve (222) according to the partition ash extraction trigger value S. The partition ash extraction trigger value S is obtained by weighting the normalized differential pressure increase before and after the ash collection tank, the increase in dust content at the SCR inlet, and the boiler load change rate. When S reaches the enhanced ash extraction threshold, the opening degree of the independent regulating valve (222) in the corresponding ash extraction control zone is increased. When the NOx or ammonia escape fluctuation at the SCR outlet exceeds the preset range, the opening degree change rate of the independent regulating valve (222) in the adjacent ash extraction control zone is limited. When the differential pressure measuring points before and after the ash collection tank fail, the dust content signal at the SCR inlet is invalid, or the differential pressure of the ash extraction branch pipe (221) increases abnormally, the opening rate of the corresponding independent regulating valve (222) is maintained or reduced, and a purging or maintenance prompt is issued.

9. The collection device according to claim 1, characterized in that, The secondary flow equalization plate (24) has a compensation opening with a higher opening ratio than other areas in the downstream projection area of ​​the ash extraction channel. The compensation openings are arranged in groups along the downstream projection area of ​​the ash extraction channel. The opening ratio of the compensation openings is determined according to the design ash extraction volume of the corresponding ash extraction control zone.

10. An SCR denitrification reactor, characterized in that, Includes the SCR first-layer catalyst inlet partition negative pressure ash extraction fly ash collection device as described in any one of claims 1 to 9.

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