Flue gas baffle system for SCR (Selective Catalytic Reduction) denitration device and use method

Abstract

The invention relates to the technical field of flue gas denitrification, and discloses a flue gas baffle system for an SCR (Selective Catalytic Reduction) denitrification device and a use method.The flue gas baffle system is provided with a control system and a matrix flowmeter, a baffle assembly is composed of a plurality of baffle units, each flue is uniformly divided into a plurality of subareas, and each subarea corresponds to a group of adjusting units; and each baffle unit correspondingly controls one subarea of the cross section, so that the technical effects of automatically detecting the flow field at the inlet of the reactor and automatically adjusting the angle of the baffle under different loads or different flow field conditions are realized, the uniformity of the flue gas flow field under different loads is improved, the adaptability of the SCR denitration device to the loads is improved, and the service life of the SCR denitration device is prolonged. The ammonia escape amount when the load or the flow field changes is reduced, and the technical problem that in the prior art, an SCR denitration device cannot adjust the flue gas flow field according to the incoming flow characteristics of flue gas and cannot adjust the flue gas flow field when the performance of an existing flow equalizing device is damaged is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitration, and in particular to an automatically adjustable baffle system for an SCR denitration device and a use method thereof. Background Art

[0002] In the field of industrial flue gas pollutant removal, SCR denitrification devices are often used to remove nitrogen oxides from flue gas. SCR denitrification is a process in which nitrogen oxides are converted into harmless gases such as nitrogen by adding a reducing agent (usually ammonia) to react with nitrogen oxides in the flue gas under the action of a catalyst. Whether the flue gas and the reducing agent are mixed evenly and whether the two are in sufficient contact with the catalyst are crucial to the denitrification efficiency and the control of the ammonia escape rate. Therefore, a flow equalizing device is usually set inside the denitrification device to improve the uniformity of the flue gas flow field. The most commonly used flow equalizing devices include flue gas baffles and rectifier grids. The inventor first noticed that by guiding the flue gas according to its flow field characteristics, the uniformity of the flue gas flow field under different working conditions can be improved, thereby improving the adaptability of the SCR denitrification device to the load, and ultimately achieving the technical effect of improving the denitrification efficiency and reducing the ammonia escape rate.

[0003] In the existing technology, the flue gas damper is usually arranged in the vertical section of the denitrification flue and has only opening and closing functions; the flue gas damper is usually arranged at the corner of the denitrification flue and the SCR reactor inlet cover, and the rectifier grid is usually arranged at the top of the SCR reactor. The flue gas damper and the rectifier grid are both fixed devices and cannot be adjusted according to the incoming flow characteristics of the flue gas. They cannot be adjusted when the performance of the existing flow equalization device is destroyed (such as dust accumulation on the baffle), or the angle of the flue gas damper and the rectifier grid relative to the flue cross section can be adjusted synchronously. During the production process, as the production load changes, the flow field at the inlet of the SCR denitrification device becomes complex and changeable, and the total amount of flue gas and the uniformity of the flue gas in the flue will change greatly. When the performance of the existing flow equalization device is destroyed, the fixed SCR flue gas flow equalization device in the existing technology is difficult to ensure a good flow equalization effect under different operating conditions, and thus it is difficult to ensure high denitrification efficiency and low ammonia escape rate under different operating conditions. In addition, during actual operation, operators usually give priority to ensuring the priority emission of nitrogen oxides. Therefore, when the load fluctuates frequently and deviates from the design operating conditions, ammonia escape often exceeds the design value. The increase in ammonia escape will greatly increase the generation of ammonium bisulfate, which will be deposited in the denitrification reactor or downstream equipment, causing increased equipment corrosion and increased flue gas resistance, affecting system stability. Summary of the Invention

[0004] In order to solve the technical problem that the SCR denitrification device in the prior art cannot adjust the flue gas flow field according to the incoming flow characteristics of the flue gas and cannot adjust the flue gas flow field when the performance of the existing flow equalization device is destroyed, the present invention proposes a flue gas baffle system for the SCR denitrification device and a method of use.

[0005] A flue gas baffle system for an SCR denitrification device includes a reactor, a flue, and a baffle assembly arranged on the flue cross section. The flue outlet is connected to the air inlet of the reactor. The system also includes a control system and a matrix flow meter arranged at the air inlet of the reactor. The baffle assembly is composed of a plurality of baffle units, each baffle unit corresponding to a partition of the control cross section. A single baffle unit includes a plurality of guide vanes that maintain a consistent angle with the cross section. The control system independently adjusts the size of the guide vane angle in each baffle unit according to the partition flow signal corresponding to the area where each baffle unit is located obtained by the matrix flow meter.

[0006] The above-mentioned flue gas baffle system for the SCR denitrification device, the baffle unit also includes a central shaft and a motor, the guide vanes are fixedly arranged on the central shaft, each baffle unit is equipped with a main connecting rod driven by the motor, and the central shafts of each guide vane belonging to the same baffle unit are connected to the main connecting rod through a crank connecting rod.

[0007] The above-mentioned flue gas baffle system for the SCR denitrification device has a baffle unit arranged along the depth or width direction of the flue. The baffle assembly also includes a crossbeam, which is arranged in the flue perpendicular to the central axis to limit the central axis and form partitions in the width direction of the flue.

[0008] A method for using a flue gas damper system for an SCR denitrification device, using the flue gas damper system for an SCR denitrification device, comprises the following steps:

[0009] S1: Before the system is operated, the guide vane angle on the baffle unit is set to 90°;

[0010] S2: When the system is running, the reducing agent is sprayed into the flue and mixed and preliminarily reacted with the flue gas passing through the baffle assembly under the action of the mixer;

[0011] S3: The matrix flowmeter transmits the flow signal at the reactor air inlet to the control system, and calculates the target flow deviation P2 and the actual cross-sectional flow velocity deviation P1, compares P1 with P2 to decide the adjustment action, and transmits the corresponding action signal to the baffle unit in the corresponding partition. The baffle unit adjusts the angle of the guide vane according to the action signal calculated by the control system. The control system makes decisions on the action signal based on the principle of making the flue gas flow velocity uniform while minimizing the resistance of the guide vane to the flue gas.

[0012] The method for using the flue gas damper system for the SCR denitrification device, step S3 is specifically divided into the following steps:

[0013] S3.1: Set the current adjustment times to N=0 and the total number of partitions to n;

[0014] S3.2: When P1>P2, determine whether N is less than n / 2. If so, execute step S3.3; if not, execute step S3.4. When P1≤P2, execute step S3.5.

[0015] S3.3: Increase the angle of the guide vane in the partition with the lowest flow rate until the flow rate in that partition equals the average flow rate of all partitions, or the guide vane angle is adjusted to 90°. Set N = N + 1. After a unit time, obtain the value of P1 and return to step S3.2.

[0016] S3.4: Reduce the angle of the guide vane in the zone with the highest flow rate until the flow rate in that zone equals the average flow rate of all zones or the angle of the guide vane in that zone reaches 0°. Set N = N + 1. After a unit time, obtain the value of P1 and return to step S3.2.

[0017] S3.5: Return to step S3.1.

[0018] The beneficial effects of the present invention include: the present invention measures the flow field parameters at the reactor air inlet by providing a matrix flow meter and a control system, divides the baffle assembly into a plurality of baffle units, and the control system dynamically adjusts the angle of the adjustable baffle according to the flow field in the flue and in units of partitions, thereby achieving the technical effect of automatically detecting the flow field at the reactor inlet and automatically adjusting the baffle angle under different loads or different flow field conditions, improving the uniformity of the flue gas flow field under different loads, improving the adaptability of the SCR denitrification device to the load, reducing the ammonia escape amount when the load or flow field changes, and solving the technical problem in the prior art that the SCR denitrification device cannot adjust the flue gas flow field according to the incoming flow characteristics of the flue gas and cannot adjust the flue gas flow field when the performance of the existing flow equalization device is destroyed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a cross-sectional view of the overall structure of the flue gas damper system for the SCR denitrification device of the present invention.

[0020] Figure 2 This is a schematic diagram of the angle adjustment structure of the baffle unit of the flue gas baffle system for the SCR denitrification device of the present invention.

[0021] Figure 3 This is a schematic diagram of guide vanes of different baffle units in the flue gas baffle system for an SCR denitrification device of the present invention being at different angles.

[0022] Figure 4 This is a structural schematic diagram of an embodiment of the present invention in which the baffle units of the flue gas baffle system for the SCR denitrification device are arranged along the depth direction of the flue.

[0023] Figure 5It is a structural schematic diagram of one embodiment of the present invention in which the baffle unit of the flue gas baffle system for the SCR denitrification device is arranged along the depth direction of the flue according to the flow field adjustment.

[0024] Figure 6 This is a structural schematic diagram of one embodiment of the present invention in which the baffle units of the flue gas baffle system for the SCR denitrification device are arranged along the width direction of the flue.

[0025] Figure 7 It is a structural schematic diagram of one embodiment of the present invention in which the baffle unit of the flue gas baffle system for the SCR denitrification device is arranged along the width direction of the flue according to the flow field adjustment.

[0026] Figure 8 This is a logic block diagram of step S3 in one cycle of the method for using the flue gas damper system for an SCR denitrification device of the present invention.

[0027] Markings in the figure are: 1-flue, 2-reactor, 3-baffle unit, 31-guide vane, 32-center shaft, 33-crank connecting rod, 34-main connecting rod, 35-motor, 4-crossbeam, 5-matrix flowmeter, 6-control system. DETAILED DESCRIPTION

[0028] The present invention will be described below with reference to the accompanying drawings.

[0029] Example 1:

[0030] like Figure 1 The figure shows a flue gas baffle system for an SCR denitrification device according to the present invention, comprising a reactor 2, a flue 1 and a baffle assembly arranged on the cross section of the flue 1. The outlet of the flue 1 is connected to the air inlet of the reactor 2. The flue gas is adjusted in the flue 1 by the baffle assembly and finally enters the reactor 2 to react with the reducing agent under the action of the catalyst. The system also includes a control system 6 and a matrix flowmeter 5 arranged at the air inlet of the reactor 2. The baffle assembly is composed of a plurality of baffle units 3, each baffle unit 3 corresponding to a partition of the control cross section. A single baffle unit 3 includes a plurality of guide vanes 31 having a consistent angle with the cross section. The matrix flowmeter 5 can measure the flow distribution of the flue gas above the reactor 2 in real time and transmit the flow signal to the control system 6. The control system 5 automatically calculates the relative standard deviation of the velocity and decides on the adjustment action to control the size of the angle between the guide vanes 31 in the baffle unit 3 and the cross section. In this embodiment, the number of partitions is set to 4 according to the unevenness of the flow field (mainly the velocity field of the flue gas) in the flue 1 under different loads.

[0031] Further, such as Figures 2-3As shown, the baffle unit 3 also includes a central shaft 32 and a motor 35. The guide vane 31 is fixedly arranged on the central shaft 32 and rotates with the central shaft 32. The guide vane 31 can rotate 0 to 90 degrees along the central shaft. Each baffle unit 3 is equipped with a main connecting rod 34 driven by the motor 35. The central shaft 32 of each guide vane 31 belonging to the same baffle unit 3 is connected to the main connecting rod 34 through a crank connecting rod 33, so that a crank connecting rod 33 can synchronously drive multiple central shafts 32 to rotate. One end of the crank connecting rod 33 is connected to the output end of the motor 35 to achieve the effect of synchronous rotation of the guide vanes 31 in a baffle unit 3.

[0032] Further, such as Figure 4 As shown, the baffle assembly also includes a crossbeam 4, which is perpendicular to the central axis 32 and is arranged in the flue 1 to limit the central axis 32 to form a partition in the depth direction of the flue 1. According to the flow field distribution of the flue gas in the actual production process, the baffle unit 3 is arranged along the depth direction of the flue 1, as shown in FIG. Figure 5 As shown, when the flue gas flow rate needs to be increased in a certain partition, the baffle unit 3 may not be set in the partition according to the flow field distribution, which saves costs. The crossbeam 4 is provided with a rotation limiting structure that matches the fixed end of the central axis 32. The fixed end of the central axis 32 is fixedly connected to the rotation limiting structure. When the baffle unit 3 is set in the depth direction of the flue 1, the crossbeam 4 can fix the central axis 32 on the baffle unit 3, and play an auxiliary role in the partition of the flue 1.

[0033] A method for using a flue gas damper system for an SCR denitrification device, using the flue gas damper system for an SCR denitrification device, comprises the following steps:

[0034] S1: Before the system is running, the angle of the guide vanes 31 on the baffle unit 31 is set to 90°, and the baffle unit 31 is in a fully open state;

[0035] S2: When the system is running, the reducing agent is sprayed into the flue 1 and mixed and preliminarily reacted with the flue gas passing through the baffle unit 31 under the action of the mixer. Then, the mixed gas of the flue gas and the reducing agent enters the reactor 2 for full reaction. The reacted gas flows out of the entire denitrification device through the outlet of the reactor 2;

[0036] S3: The matrix flowmeter 5 transmits the flow signal at the inlet of the reactor 2 to the control system 6. The control system 6 calculates the target flow rate deviation P2 and the flow rate relative standard deviation P1 according to the flow rate distribution measured by the flowmeter 5 above the reactor 2 (the flow rate relative standard deviation here is obtained according to the calculation method described in the relevant technical regulations for denitrification in the power industry), compares P1 with P2 to decide on the adjustment action, and transmits the corresponding action signal to the motor 35 of the baffle unit 3 in the corresponding partition. The motor 35 adjusts the angle of the guide vane 31 according to the action signal calculated by the control system. The control system 6 makes a decision on the action signal based on the principle of reducing the resistance of the guide vane 31 to the flue gas while the flue gas flow rate tends to be uniform.

[0037] Further, such as Figure 8 As shown in the logic block diagram, step S3 is specifically divided into the following steps:

[0038] S3.1: Set the current adjustment times to N=0 and the total number of partitions to n;

[0039] S3.2: When P1>P2, determine whether N is less than n / 2. If so, execute step S3.3; if not, execute step S3.4. When P1≤P2, execute step S3.5;

[0040] S3.3: Increase the angle of the guide vane 31 in the partition with the lowest flow rate until the flow rate in that partition equals the average flow rate of all partitions, or the angle of the guide vane 31 is adjusted to 90°. Set N = N + 1. After a unit time, obtain the value of P1 and return to step S3.2.

[0041] S3.4: Reduce the angle of the guide vane 31 in the zone with the highest flow rate until the flow rate in that zone equals the average flow rate of all zones or the angle of the guide vane 31 in that zone reaches 0°. Set N = N + 1. After a unit time, obtain the value of P1 and return to step S3.2.

[0042] S3.5: Return to step S3.1.

[0043] Reference Manual Figure 4An industrial kiln employs the flue gas damper system for an SCR denitrification device described in this embodiment. Under different loads, the flue gas volume and temperature of this industrial kiln exhibit significant variations in both the width and length of the denitrification inlet flue cross-section. The flue cross-section measures 2100 mm x 8020 mm, and the corresponding adjustable vanes 31 in the baffle units 3 are 500 mm wide and 3900 mm long. The baffle units 3 are arranged along the depth direction. A crossbeam 4 is provided in the middle of the flue 1, dividing the flue 1 into two zones in the width direction with the crossbeam 4 as the dividing line. The four adjustable baffles 31 on each side are grouped into two adjacent groups of baffle units 3. Each group of baffle units 3 can be independently adjusted and controlled by a control system 6. Driven by the central shaft 32, the guide vanes 31 rotate between 0° and 90°. The areas corresponding to the four groups of baffle units are numbered as ①, ②, ③, and ④. Under different loads, the flow velocity and flue gas temperature distribution of each area are shown in Table 1 below. When the system is running at full load, the angles of the four groups of adjustable guide vanes are all set to 90°, and the relative standard deviation of the flue gas velocity above the catalyst is 14.3%, and the temperature deviation is 0.8°C; when running at medium and high loads, the angles of the adjustable guide vanes in areas ① and ② are adjusted to 45°, and the angles of the adjustable guide vanes in areas ③ and ④ are kept at 90°, and the flue gas velocity above the catalyst is 0.8°C. The relative standard deviation is 7.5% (a decrease of 61% compared to when using traditional baffles), and the temperature deviation is 4°C (a decrease of 15% compared to when using traditional baffles); when operating at medium and low loads, the angles of the adjustable guide vanes in zones ① and ② are adjusted to 45° and 60° respectively, and the angles of the adjustable guide vanes in zones ③ and ④ are maintained at 90°. The relative standard deviation of the flue gas velocity above the catalyst is 9.4% (a decrease of 58% compared to when using traditional baffles), and the temperature deviation is 12.8°C (a decrease of 10% compared to when using traditional baffles).

[0044]

[0045] Table 1

[0046] Example 2:

[0047] In the operation test of Example 1, it was found that the angle of the adjustable guide vanes in the ③ and ④ zones was always kept at 90° during the adjustment process. The guide vanes in the ③ and ④ zones could also be removed. Figure 5 As shown, it is basically equivalent to the situation in embodiment 1.

[0048] like Figure 6 or Figure 7 As shown, the cross section of the flue can also be divided along the flue width direction, and correspondingly arranged with a plurality of baffle units 3. In view of the comparison between embodiments 1 and 2, the guide vanes can also be arranged only on one section of the central axis, that is, Figure 7 The situation shown.

[0049] Example 3:

[0050] like Figure 7 As shown, according to the flow field distribution of the flue gas in the actual production process, the baffle unit 3 is changed to be arranged along the width direction of the flue 1, and the baffle unit 3 may not be set in some partitions according to the flow field distribution, which is basically equivalent to the situation where the baffle with a protection angle of 90° is not set. An end limiting structure matching the fixed end of the central axis 32 is provided on the side wall of the flue 1, and the fixed end of the central axis 32 is rotatably connected relative to the end limiting structure, which does not affect the adjustment of the angle of the baffle unit 3. In this embodiment, a 660MW coal-fired boiler adopts an external dual-reactor SCR denitrification device, and the cross-sectional size of the single-sided denitrification flue is 3500mm×14915mm. According to the characteristics of the coal-fired boiler, the flue gas is less uneven in the left and right width directions, but is more uneven in the front and back depth directions, so two partitions ① and ② are provided. The single-sided denitrification flue is provided with 24 guide vanes 31, wherein the width of a single central shaft 32 and the guide vanes 31 provided thereon is 600mm, and the length of the guide vanes 31 is 1400mm. One end of the central shaft 32 is connected to the crank connecting rod 33, and the other end is rotatably connected to the end limit structure on the side wall of the flue 1. Driven by the central shaft 32, the guide vanes 31 rotate at an angle of 0° to 90°.

[0051] The flue gas flow rate and flue gas temperature of partitions ① and ② under different loads are shown in Table 2 below. When the system operates at BMCR load, which is usually the design condition, the guide vane angle of partitions ① and ② can be set to 90°. At this time, the relative standard deviation of the flue gas velocity above the catalyst is 9.6%, and the temperature deviation is 2.8°C; at 75% THA load, all guide vane angles are adjusted to 60°, the relative standard deviation of the flue gas velocity above the catalyst is 7.2% (a decrease of 25% compared to when traditional baffles are used), and the temperature deviation is 8.2°C (a decrease of 37% compared to when traditional baffles are used); at 50% THA load, the guide vane angles of partitions ① and ② are adjusted to 0°, the relative standard deviation of the flue gas velocity above the catalyst is 7.1% (a decrease of 25% compared to when traditional baffles are used), and the temperature deviation is 9.4°C (a decrease of 46% compared to when traditional baffles are used).

[0052]

[0053] Table 2

[0054] From the above flow field simulation results, it can be found that the flue gas baffle system and use method for the SCR denitrification device described in the present invention can significantly improve the uniformity of the denitrification flow field under different loads and enhance the adaptability of the system.

[0055] Compared with the existing technology, the flue gas baffle system for the SCR denitrification device provided by the present invention pre-partitions the flue gas flow field in the flue, uses a matrix flow meter to measure the flow field parameters at the reactor inlet, and controls the baffle assembly in units of partitions, thereby achieving the technical effect of automatically detecting the flow field at the reactor inlet under different loads or different flow field conditions and automatically adjusting the baffle angle. It improves the uniformity of the flue gas flow field under different loads, improves the adaptability of the SCR denitrification device to the load, reduces the ammonia escape amount when the load or flow field changes, and solves the technical problem in the prior art that the SCR denitrification device cannot adjust the flue gas flow field according to the incoming flow characteristics of the flue gas or when the performance of the existing flow equalization device is destroyed.

Claims

1. A flue gas damper system for an SCR denitrification device, comprising a reactor (2), a flue (1), and a baffle assembly arranged on a cross section of the flue (1), wherein the flue (1) outlet is connected to the air inlet of the reactor (2), and is characterized in that: The invention also includes a control system (6) and a matrix flow meter (5) arranged at the air inlet of the reactor (2); the baffle assembly is composed of a plurality of baffle units (3); each baffle unit (3) corresponds to a partition of the control cross section; a single baffle unit (3) includes a plurality of guide vanes (31) having an angle consistent with the cross section; the control system (6) independently adjusts the size of the angle of the guide vanes (31) in each baffle unit (3) according to the partition flow signal corresponding to the area where each baffle unit (3) is located, obtained by the matrix flow meter (5).

2. The flue gas damper system for an SCR denitrification device according to claim 1, characterized in that: The baffle unit (3) further comprises a central shaft (32) and an electric motor (35); the guide vanes (31) are fixedly arranged on the central shaft (32); each baffle unit (3) is provided with a main connecting rod (34) driven by the electric motor (35); the central shaft (32) of each guide vane (31) belonging to the same baffle unit (3) is transmission-connected to the main connecting rod (34) via a crank connecting rod (33).

3. The flue gas damper system for an SCR denitrification device according to claim 2, characterized in that: The baffle assembly further comprises a crossbeam (4), which is arranged in the flue (1) perpendicular to the central axis (32) and limits the central axis (32) to form partitions in the width direction of the flue (1).

4. A method for using a flue gas damper system for an SCR denitrification device, using the flue gas damper system for an SCR denitrification device according to any one of claims 1 to 3, comprising the following steps: S1: Before the system is operated, the angle of the guide vane (31) on the baffle unit (3) is set to 90°; S2: When the system is in operation, the reducing agent is sprayed into the flue (1), and is mixed and preliminarily reacted with the flue gas passing through the baffle assembly under the action of the mixer; S3: The matrix flow meter (5) transmits the flow signal at the air inlet of the reactor (2) to the control system (6), and calculates the target flow rate deviation P2 and the actual cross-sectional flow rate deviation P1, compares P1 with P2 to decide the adjustment action, and transmits the corresponding action signal to the baffle unit (3) in the corresponding partition. The baffle unit (3) adjusts the angle of the guide vane (31) according to the action signal calculated by the control system. The control system (6) makes a decision on the action signal based on the principle of making the flue gas flow rate uniform while minimizing the flue gas resistance of the guide vane (31).

5. The method for using the flue gas damper system for an SCR denitrification device according to claim 4, characterized in that: Step S3 is specifically divided into the following steps: S3.1: Set the current adjustment times to N=0 and the total number of partitions to n; S3.2: When P1>P2, determine whether N is less than n / 2. If so, execute step S3.3; if not, execute step S3.

4. When P1≤P2, execute step S3.

5. S3.3: Increase the angle of the guide vane (31) of the partition with the lowest flow velocity until the flow velocity in the partition is equal to the average flow velocity of all partitions, or the angle of the guide vane (31) is adjusted to 90°, set N=N+1, obtain the P1 value after a unit time, and return to step S3.2; S3.4: Reduce the angle of the guide vane (31) of the partition with the highest flow velocity until the flow velocity in the partition is equal to the average flow velocity of all partitions or the angle of the guide vane (31) in the partition is 0°, set N=N+1, obtain the P1 value after a unit time, and return to step S3.2; S3.5: Return to step S3.1.

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