Double-reheat boiler tail three-flue full-circumferential baffle structure and adjusting method thereof

Abstract

The application discloses a secondary reheat boiler tail three flue full circumference baffle structure and a regulating method thereof, and solves the problems of uneven resistance in the circumferential direction, the existence of flue gas short circuit phenomenon and the serious uneven distribution of heat exchange amount on each tube bundle of the heating surface when the opening of the existing flue baffle structure is regulated, and comprises peripheral blades and central blades, wherein inner peripheral blades are uniformly distributed between the peripheral blades and the central blades, the peripheral blades, the central blades and the inner peripheral blades independently rotate around the same rotating shaft, and the flow passage areas cut off by the blade profiles are equal when the opening of the peripheral blades, the central blades and the inner peripheral blades is 0. The flue gas flow in the flue is evenly distributed, and the local overheating problem of the heating surface in the tail three flue and the risk of not meeting the parameters are reduced.

Description

Technical Field

[0001] This invention relates to the field of double reheat unit technology, and in particular to a double reheat boiler tail section three flue full-circumference baffle structure and its adjustment method. Background Technology

[0002] Ultra-supercritical double reheat units represent a significant upgrade in thermal power technology. Through double reheat technology, energy savings are achieved, and carbon emissions are correspondingly reduced. However, coal-fired boilers have high thermal inertia, leading to frequent fluctuations in key parameters such as steam temperature during transient operations under varying loads. Therefore, regulating the reheat steam temperature has become crucial for ensuring the safe and stable operation of the unit. Currently, the main method involves altering the opening of the flue gas dampers in the three tail flues to change the resistance of the airflow through each flue, thereby varying the amount of flue gas passing through different flues and changing the heat absorption ratio of each heating surface, thus regulating the reheat steam temperature.

[0003] For example, the flue gas damper arrangement structure and reheat steam temperature control method of the CN114110559A double reheat boiler, by adding a low-reheat main flue gas damper, allows its opening degree to track the average outlet steam temperature of the primary and secondary high-reheat boilers. This decouples the original three-parameter coupled regulation problem into two sets of two-parameter regulation problems, reducing the operational difficulty of the control system and improving its response and convergence speed. However, this patent does not consider the problems of low flue gas flow rate and insufficient heat distribution at both ends of the damper blades due to the extremely uneven velocity distribution of flue gas in the flow channel caused by the boundary layer effect. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that the existing flue damper structure has uneven circumferential resistance when adjusting the opening, resulting in flue gas short-circuiting and thus causing serious uneven heat exchange distribution on the tube bundles of the heating surface. The invention provides a full-circumferential damper structure for the tail three flues of a secondary reheat boiler and its adjustment method, which evenly distributes the flue gas flow in the flue and reduces the risk of local overheating and parameter non-compliance on the heating surface of the tail three flues.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for adjusting the three-flue full-circumference baffle structure at the tail end of a reheat boiler includes: outer blades and a central blade, with inner circumferential blades evenly distributed between the outer blades and the central blade, and the outer blades, central blades and inner circumferential blades rotating independently around the same rotation axis; when the opening of the outer blades, central blades and inner circumferential blades is 0, the flow channel area cut off by the blade profile is equal.

[0006] The three-flue full-circumference baffle structure at the tail end of the double reheat boiler provided by this invention ensures that the circumferential resistance distribution is similar when the flue gas flows through a certain flue, and the heat exchange amount distributed to each tube bundle on the same heating surface is basically consistent. Compared with the prior art, this structure can effectively prevent the phenomenon of "flue gas short circuit" at both ends of the blades caused by uneven circumferential resistance during opening adjustment (mainly reflected in the improved flow uniformity), effectively solve the problem of severely uneven heat exchange distribution on each tube bundle on the same heating surface, and improve the overall operational stability of the unit.

[0007] Preferably, the outer perimeter of the outermost blade covers more than 90% of the inner perimeter of the flue, and the perimeter of the center blade covers more than 90% of the inner perimeter of the innermost innermost blade.

[0008] Preferably, there is one outer leaflet, one central leaflet, and 2-6 inner leaflets.

[0009] A method for adjusting the full-circumference baffle structure of the three flues at the tail end of a double reheat boiler, comprising: S1: Adjust the opening of each blade to balance the resistance of each corresponding flow channel in the flue, and record the opening of each blade under different equivalent total flow areas to obtain the flow area-opening table; S2: Determine the initial value of each blade opening and the increment of each blade opening at the next moment; S3: If an overheated flue exists, activate the desuperheating water spray plan. While maintaining the current blade opening stability, calculate the desuperheating water volume based on the overheating range, and assist in temperature control through heat release from non-overheated flues.

[0010] As a preferred method, the triggering conditions for determining whether there is an overheated flue include overheating triggering, prediction triggering, and fault triggering; if any triggering condition is met, the desuperheating water spraying plan is activated, and the desuperheating water spraying plan is stopped after the overheating phenomenon disappears.

[0011] Preferably, the over-temperature trigger is when the temperature of any flue heating surface exceeds the design value of the first temperature threshold; the prediction trigger is when the predicted temperature of the flue heating surface at the next moment is greater than the design value of the second temperature threshold and cannot be avoided by adjusting the full circumference baffle opening; the fault trigger is when one or more blades fail and other blade adjustments cannot compensate for the flow deviation to within the deviation threshold.

[0012] Preferably, S2 includes: calculating the required heat distribution ratio of the three flues based on the measured values ​​of the heating surface measuring points and the return parameters of the reheated steam in the secondary reheat boiler; determining the flow rate of each flue and obtaining the target value of the blade opening under the current operating condition based on the flow area-opening table; and calculating the blade opening increment based on the difference between the target value of the blade opening under the current operating condition and the target value of the blade opening under the next operating condition.

[0013] As a preferred option, after activating the desuperheating water spray plan: maintain the blade opening of the non-overheating flue, adjust the airflow path through the baffle, and release heat to the flue where the overheating degree is less than the overheating threshold; simultaneously calculate the expected external heat exchange volume generated by the flue gas flow at the next moment, convert it into the required desuperheating water volume, and then start the water spray.

[0014] As a preferred approach, when establishing the flow area-opening table, the mapping relationship is established through flow resistance calculation or CFD.

[0015] As a preferred option, the initial opening value of each blade is fully open.

[0016] Therefore, the present invention has the following beneficial effects: by adopting a full-circumferential baffle structure of "outer circumferential blades + inner circumferential blades + central blades", the local resistance is reduced by increasing the blade opening in the near-wall area, and the resistance is increased by appropriately reducing the opening in the middle section. This breaks the inherent problem of "high resistance in the near-wall area and low resistance in the middle section" caused by the boundary layer effect of traditional baffles, effectively achieving uniform distribution of flue gas flow throughout the circumference, and effectively avoiding the problem of severe uneven heat exchange conditions, heat exchange rates and heat exchange of different tube bundles on the same heating surface during variable load operation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the full-circumference baffle structure of the three flues at the tail end of the secondary reheat boiler in this invention.

[0018] Figure 2 This is a flowchart of the method for adjusting the full-circumference baffle structure of the three flues at the tail end of the secondary reheat boiler in this invention.

[0019] Figure 3 This is a schematic diagram of the circumferential baffle operation effect in Example 2.

[0020] Figure 4 This is another schematic diagram of the circumferential baffle operation effect in Example 2.

[0021] Figure 5 This is a schematic diagram showing the velocity distribution at the baffle outlet of a reheat unit operating at 75% load.

[0022] Figure 6 This is a schematic diagram showing the velocity distribution at the baffle outlet of a reheat unit operating at 50% load.

[0023] In the diagram: 1. Outer blades; 2. Inner blades; 3. Center blades; 4. Secondary reheat unit; 5. Flue; 6. Full circumferential baffle. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this application will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only one preferred embodiment of this application and are only used to explain this application. They do not limit the scope of protection of this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] In double reheat units, adjusting the opening of the flue gas dampers in each of the three tail flues is the core control technology for regulating reheat steam temperature. By adjusting the flue gas flow distribution in the flues, precise, efficient, and reliable control of the reheat steam temperature can be achieved. Due to the boundary layer effect, the flow resistance near the wall is relatively high, the flue gas velocity is lower at the ends of the blades and higher in the middle section, resulting in a highly uneven velocity distribution of the flue gas in the flow channels. Simultaneously, because the heat exchange tube bundles in the three tail flues are arranged perpendicular to the flow channels at certain intervals, the uneven flue gas flow will lead to different flue gas flow rates through different tube bundles on the same heat exchange surface, resulting in different convective heat transfer conditions and varying amounts of heat exchange between the flue gas and each tube bundle.

[0026] On the other hand, because the heat absorbed by each tube bundle through the tail flue varies significantly—namely, the flue gas flow rate at both ends of the baffle blades is small, the heat distribution is low, and the heat exchange effect is poor—the local heating surfaces do not adequately heat the reheat steam, resulting in substandard reheat steam parameters. Meanwhile, other heating surfaces exchange heat with excessive flue gas, leading to a risk of localized dynamic overheating.

[0027] Therefore, this application designs a novel three-flue outlet baffle structure at the tail of a boiler. Its full-circumference design ensures that the flow distribution of flue gas is similar across the flue cross-section when the flue gas flows through a certain flue, thereby improving the operational stability of the secondary reheat unit.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] Example 1: This embodiment provides a three-flue full-circumference baffle structure for the tail section of a secondary reheat boiler, such as... Figure 1 As shown, the full-circumference baffle adopts a three-layer coaxial blade structure consisting of an outer periphery, an inner periphery, and a center. Each blade rotates independently around the same axis of rotation. Figure 1 Draw a line at the midpoint. The specific hierarchy and functions of the full-circumference baffle structure are as follows, including: (1) Outer blade 1: Located in the outermost layer, its outer perimeter needs to cover more than 90% of the inner wall perimeter of the flue to ensure that the blade is basically in contact with the inner wall of the flue. (2) Inner peripheral blades 2 (n blades): evenly distributed between the central blade and the outer blades, it is the core regulating unit for achieving circumferential flow uniformity.

[0030] The value of n needs to be determined by a combination of the principle of performance balance and practical engineering constraints: The basic value range for n is preferably 2-6 blades, and can be adjusted directionally according to the actual boiler flue conditions. This range can ensure the flow uniformity effect while avoiding control redundancy and mechanical failure risks caused by an excessive number of blades.

[0031] Critical constraint condition: The dimensionless width of the blade (blade frame width b / blade height h) must be ≥0.01 to ensure that the b / h value of each blade is within the critical range and to avoid insufficient blade structural strength.

[0032] (3) Center blade 3: Located in the innermost layer, it has a rectangular structure and its circumference should cover more than 90% of the inner wall circumference of the innermost blade. Its main function is to stabilize the central flow field and prevent the airflow from forming vortices in the axial region.

[0033] The three-flue full-circumference baffle structure at the tail end of the secondary reheat boiler provided in this embodiment ensures that the flow distribution of flue gas is similar across the flue cross-section when the flue gas flows through a particular flue. Compared with existing technologies, this structure effectively solves the problems of uneven circumferential resistance and "flue gas short-circuiting" phenomenon in existing baffle structures when adjusting the opening, which leads to severely uneven heat transfer distribution on the tube bundles of the heating surface. Therefore, it can significantly improve the overall operational stability of the unit. It can also solve the problem of dynamic steam temperature exceeding or failing to meet standards due to unreasonable flue gas flow distribution in the three flue ends when a secondary reheat boiler in a coal-fired power plant is operating under varying loads or other conditions deviating from the design conditions.

[0034] In this embodiment, there is no fixed formula for the size design of the outer blades, inner blades, and center blades, as long as the requirements are met. Figure 1 The full-circumference blade structure and coaxial independent rotation adjustment requirements shown are sufficient, but the following basic principles must be followed: ①Efficiency balance principle: On the one hand, the larger the n value, the more blades there are, which is more conducive to the flow reforming and fine adjustment of flue gas flow; at the same time, the size of each blade must meet the material mechanics requirements for fatigue deformation control, that is, the dimensionless width of the material frame of any blade must not be lower than the critical value. ② Equivalent Area Principle: To reduce control redundancy and ensure the benefits of independent adjustment of each blade, the flow channel area covered by each blade when the opening is 0 should be numerically similar and should not deviate too much (i.e., Figure 1 In the three diagrams of the outer blade, inner blade, and center blade, the flow channel area [gray area] truncated by the blade outline should be equal, or the difference in flow channel area truncated by the blade outline of the three types of blades should be less than a threshold.

[0035] The full-circumferential design ensures that the circumferential resistance distribution is similar when the flue gas flows through a certain flue, resulting in a basically consistent heat exchange amount distributed to each tube bundle on the same heating surface. Compared with existing technologies, this structure can effectively prevent uneven circumferential resistance and the "flue gas short-circuiting" phenomenon at both ends of the blades during opening adjustment (mainly reflected in improved flow uniformity), effectively solving the problem of severely uneven heat exchange distribution on each tube bundle on the same heating surface, thus improving the overall operational stability of the unit.

[0036] Because of the use of a full-circumference structural design, the flue gas flow rate is effectively evenly distributed throughout the entire circumference. Because the flue gas flow rate is evenly distributed in the flue, the problem of severe uneven heat exchange conditions, heat exchange rates, and heat exchange of different tube bundles on the same heating surface during variable load operation is effectively avoided. Because the problem of uneven heat exchange of each tube bundle on the heating surface is solved, the problem of local overheating or substandard reheat steam parameters in the three flues at the tail end is effectively improved, while retaining the emergency measure of desuperheating water spray in the event of overheating of all flues.

[0037] This embodiment also provides a method for operating the full-circumference baffle structure, including the following steps: Step (1): Create a flow area-opening table. Step (2): Determine the initial value of the opening x i,t0 It can be set to fully open (100% opening); or set according to the values ​​recorded in the opening table; or according to other manual settings. Step (3): During the operation of the full-circumference baffle structure, determine the increment d of the opening of each blade at the next moment. xi,t (Can be negative). Step (4): Start-up and shutdown of emergency de-cooling water spray response.

[0038] The desuperheating water spray emergency plan shall be activated immediately in any of the following situations: (a) The self-testing point measurement results showed that any flue gas duct experienced overheating due to excessive fluctuations in steam parameters. (b) Under extreme conditions, all calculated flow distribution schemes cannot prevent overheating at the next moment (e.g., water-coal ratio control imbalance during load increase, rapid increase in temperature of primary and secondary reheat heating surfaces, and the inability of the third flue to withstand all flue gas heat). (c) If the opening action of one or more baffle blades fails, adjusting other flue baffle blades is insufficient to achieve the expected distribution of flue gas heat.

[0039] Cooling spray water emergency start-up and shutdown operation: Maintain the current opening of all blades, or selectively release heat to the flue with a less severe overheating, and simultaneously calculate the expected external heat exchange caused by the flue gas flow at the next moment, convert it into the required cooling water volume and start the operation until the overheating phenomenon or trend disappears.

[0040] The three-flue full-circumference baffle structure at the tail end of the double reheat boiler provided in this embodiment has the following beneficial effects: (1) This embodiment adopts a full-circumferential baffle structure of “outer circumferential blades + inner circumferential blades + central blades”, which can effectively guide the flue gas flow. This structure can overcome the inherent problem of “high resistance in the near-wall area and low resistance in the middle section” caused by the boundary layer effect of traditional baffles. (2) The blades can be independently adjusted to compensate for the resistance differences at different circumferential positions. Specifically, in the near-wall region, the local resistance is reduced by increasing the blade opening, and the resistance is increased by appropriately reducing the opening in the middle section. Ultimately, the flue gas flow is evenly distributed when it flows through the flue, so that the flow rate and velocity of the flue gas flowing through different tube bundles on the same heating surface tend to be consistent. This avoids the hidden danger of uneven local heat exchange from the root level of flow field adjustment. (For the heating surfaces of the primary low reheat, secondary low reheat and low temperature superheater arranged in the three flues at the tail end, because their tube bundles are arranged perpendicular to the flow channel at a fixed interval, the uniform flue gas flow can ensure that each tube bundle can contact the flue gas with the same amount and velocity, avoiding the extreme situation of "excessive flue gas in some tube bundles and insufficient flue gas in some tube bundles" under the traditional baffle condition.) (3) This improvement in heat exchange uniformity can also reduce thermal stress damage to the heated surfaces. Excessive local flue gas caused by traditional baffles will keep the corresponding tube bundle at a high temperature for a long time. The thermal expansion is greater than that of the surrounding tube bundles, which will cause thermal stress between the tube bundles. Long-term operation can easily cause tube bundle deformation and weld cracking. Under the condition of full-circumference baffles, the thermal stress is evenly distributed, which can significantly extend the service life of the heated surfaces and reduce the unit maintenance cost. It can be easily promoted and used in existing double reheat units. (4) Regarding the size design of each blade of the full-circumference baffle, the rules for the number of blades and the principle of equivalent area (the area of ​​the flow channel covered by each blade when it is fully closed are approximately the same) are clarified. Designers can directly apply the rules according to the flue parameters of the specific unit without having to re-perform complex flow field simulation verification.

[0041] Example 2: Based on Embodiment 1, this embodiment provides a method for adjusting the full-circumference baffle structure of the three flues at the tail of a double reheat boiler. This method is used to adjust the full-circumference baffle structure of the three flues at the tail of a double reheat boiler. Based on the structural design of the full-circumference baffle, this method forms a complete set of standardized methods covering size design and operation. It does not require a radical transformation of the overall structure of the tail flue of the existing double reheat unit. The baffles can be directly replaced at the original installation position, reducing the complexity and cost of engineering modification.

[0042] This embodiment mainly addresses the problem of uneven flue gas flow distribution caused by the baffle blade structure in the tail section of a traditional double reheat boiler. Its purpose is to evenly distribute the flue gas flow in the flue and reduce the risk of local overheating of the heating surface and failure to meet parameters in the tail section of the three flues.

[0043] This embodiment provides a method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler, including the following steps: Step 1: Adjust the opening of each blade to balance the resistance of the corresponding flow channels in the flue, and record the opening of each blade under different equivalent total flow areas to obtain the flow area-opening table.

[0044] Specifically: Through flow resistance characteristic calculations or three-dimensional computational fluid dynamics simulations, the opening of each blade is adjusted to balance the resistance of the corresponding flow channels within the flue, and the opening of each blade is recorded under different equivalent total flow areas (e.g., the total flow area is set to 15%~95% of the flue area, with each 5% change forming a group). For example, when the total flow area is 50% of the flue area, the openings of the four baffle blades are set from the outside to the inside as follows: 55%, 50%, 45%, and 40%. The percentage data mentioned in this embodiment are only examples and are not the optimal values ​​used in this scheme.

[0045] In terms of operation, it provides a method for creating a flow area-opening table (establishing a mapping relationship through flow resistance calculation or CFD simulation), dynamic adjustment logic (calculating the opening increment based on measured parameters), and emergency response procedures. Existing unit control systems only need to be upgraded with software programs to adapt to the control requirements of full-circumference baffles.

[0046] Step 2: Determine the initial opening value and the opening increment of each blade at the next moment.

[0047] The initial opening value can be set to fully open, or the initial value can be set according to the value recorded in the flow area-opening table obtained in step one.

[0048] During operation, the required heat distribution ratio for the three flues is calculated based on the measured values ​​of the heating surfaces inside the secondary reheat boiler and the return parameters of the reheat steam. After determining the flow rate of each flue, the target value x of the blade opening under the current operating conditions is obtained by referring to the flow area-opening table.i,t+1 Based on the target value x of the blade opening under the current operating conditions i,t+1 The target value x of the blade opening under the next time step operating condition. i,t The difference is used to obtain the opening increment of each blade at the next moment, and the increment is transmitted to the control system to synchronously execute the opening adjustment of each blade.

[0049] Step 3: If there is an overheated flue, activate the cooling water spray plan. While maintaining the current blade opening stability, calculate the cooling water volume based on the overheating range, and use the heat release from non-overheated flues to assist in temperature control.

[0050] In this embodiment, the triggering conditions for the de-icing water spray plan include the following: Over-temperature trigger: When the temperature of any heated surface exceeds the design value by more than 5°C (which can be adjusted according to the unit model and actual operating conditions, the same below), the sensor will transmit the over-temperature signal to the main controller, which will immediately trigger the desuperheating water spray.

[0051] Predictive trigger: The temperature at the next moment is predicted by the data processing unit. If the predicted value exceeds the design value by 3 ℃ and cannot be avoided by adjusting the baffle opening, the cooling water spray will be started in advance.

[0052] Fault Trigger: If one or more blades malfunction (such as jamming), and other blade adjustments cannot compensate for the flow deviation to within 10%, the opening of the currently malfunctioning blade will be locked, and the desuperheating spray will be activated.

[0053] The cooling and water spraying plan will be executed if any one of the above three triggering criteria is met.

[0054] The cooling water spray execution logic includes: Flow calculation: The main controller calculates the required amount of desuperheating water based on the overtemperature range ΔT.

[0055] Cooling water is sprayed in while maintaining a stable blade opening in the non-overheating flue. The airflow path is adjusted by baffles to direct excess heat to other areas until the overheating phenomenon disappears.

[0056] The method for adjusting the full-circumference baffle structure of the three flues at the tail end of a double reheat boiler provided in this embodiment has the following beneficial effects: (1) Improved reliability and intelligence of the method.

[0057] The full-circumference baffle adjustment method proposed in this invention retains emergency measures for desuperheating water spraying in case of overheating, and improves safety by optimizing the triggering logic. In extreme situations such as overheating of any flue, unavoidable overheating as predicted, or baffle blade failure, the desuperheating water spraying plan can be activated immediately. While maintaining the current blade opening stable (avoiding exacerbation of flow field fluctuations due to opening adjustments), the desuperheating water volume is accurately calculated based on the overheating amplitude, and the temperature is quickly controlled through desuperheating water spraying. Simultaneously, heat release from non-overheating flues can further assist in temperature control, forming a dual protection system of "active flow equalization regulation + passive emergency water spraying," significantly improving the unit's operational safety.

[0058] (2) Environmental emission indicators have been consistently and stably met.

[0059] After the upgrade, relying on the stable control of reheat steam temperature and the optimized flow field uniformity, the unit's environmental emission indicators have been further optimized. In the NOx emission control stage, the improved flow field uniformity at the inlet of the denitrification reactor promotes uniform ammonia distribution in the ammonia injection stage, effectively avoiding secondary pollution problems caused by localized excessive ammonia. In the SO2 emission control stage, the stable operation of reheat steam temperature has significantly improved the stability of the flue gas temperature at the inlet of the desulfurization system, significantly reducing excessive emissions and effectively ensuring that the power plant's environmental emissions meet standards, thus establishing a good environmental reputation for the company.

[0060] The following examples and specific application scenarios further illustrate the technical solution and effects of the present invention. The following examples are explanations of the present invention, but the present invention is not limited to the following examples.

[0061] The implementation object of this embodiment is a 1000MW ultra-supercritical double reheat unit 4 of a power plant.

[0062] According to the equivalent area method, each of the three flues 5 in this embodiment is equipped with four layers of full-circumference baffles 6, as shown in the structural diagram below. Figure 3 and Figure 4 As shown, Figure 3 This indicates that the outermost baffle is closed. Figure 4 This indicates that the two outer baffles are closed; other operating conditions follow the same principle. In the diagram, orange indicates that the circumferential baffles are closed, and white indicates that the circumferential baffles are open.

[0063] (1) Comparison of flow field uniformity before and after implementation.

[0064] The velocity distribution at the damper outlet of the unit operating at 75% load (750MW) is as follows: Figure 5 As shown, the vertical axis represents the standardized dimensionless flue gas velocity; the ordinary baffle (diamond-shaped mark) represents the result before modification, and the full-circumference baffle (circular mark) represents the result after modification.

[0065] It is evident that the modified flow velocity is more uniform, and the high-velocity region is significantly reduced.

[0066] Analysis of the coefficient of variation of velocity distribution: Before the modification, the coefficient of variation of velocity distribution at the outlet section was 0.797775, and after the modification, it was 0.760963. The coefficient of variation decreased by 4.61% after the modification, and the uniformity of the flow field distribution was improved.

[0067] Operating at 50% load (500MW), the velocity distribution at the baffle outlet is as follows: Figure 6 As shown.

[0068] visible: First, with Figure 5 In comparison, the flue gas flow distribution is more uniform under this operating condition (low load).

[0069] Statistical calculations show that the coefficient of variation of the velocity distribution at the outlet section was 0.764540 before the modification and 0.739759 after the modification. The coefficient of variation decreased by 3.24% after the modification, and the uniformity of the flow field distribution was improved.

[0070] (2) Improved uniformity of flow field in tail flue Measured data based on the coefficient of variation evaluation method show that the uniformity of flue gas velocity distribution at the outlet section was significantly improved after the implementation of the tail-end three-flue modification project. This flow field optimization effect can directly improve the operating conditions of downstream flue gas treatment equipment, achieving improved equipment performance and efficiency. Specifically, the uniformity of ammonia concentration distribution at the inlet of the denitrification reactor improved synchronously with the flow field optimization, the system ammonia slip rate was significantly reduced, and the stability of denitrification efficiency was effectively guaranteed. This lays a solid flow field foundation for the continuous and efficient operation of subsequent flue gas purification processes, while also improving the operational reliability and process adaptability of the entire flue gas treatment system.

[0071] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A three-flue full-circumference baffle structure for the tail section of a double reheat boiler, characterized in that, include: The outer blades and the center blades, with inner peripheral blades evenly distributed between the outer blades and the center blades, and the outer blades, the center blades and the inner peripheral blades rotating independently around the same rotation axis; When the opening of the outer blades, center blades, and inner blades is 0, the flow channel area cut off by the blade profile is equal.

2. The three-flue full-circumference baffle structure at the tail end of a double reheat boiler according to claim 1, characterized in that, The outer perimeter of the outermost blade covers more than 90% of the inner perimeter of the flue, and the perimeter of the center blade covers more than 90% of the inner perimeter of the innermost innermost blade.

3. A three-flue full-circumference baffle structure for the tail section of a secondary reheat boiler according to claim 1 or 2, characterized in that, The number of inner circumferential blades is 2-6.

4. A method for adjusting a three-flue full-circumference baffle structure at the tail end of a double reheat boiler, characterized in that, include: S1: Adjust the opening of each blade to balance the resistance of each corresponding flow channel in the flue, and record the opening of each blade under different equivalent total flow areas to obtain the flow area-opening table; S2: Determine the initial value of each blade opening and the increment of each blade opening at the next moment; S3: If an overheated flue exists, activate the desuperheating water spray plan. While maintaining the current blade opening stability, calculate the desuperheating water volume based on the overheating range, and assist in temperature control through heat release from non-overheated flues.

5. The method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler according to claim 4, characterized in that, The triggering conditions for determining whether there is an overheated flue include overheating trigger, prediction trigger, and fault trigger; if any triggering condition is met, the desuperheating water spraying plan will be activated, and the desuperheating water spraying plan will be stopped after the overheating phenomenon disappears.

6. The method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler according to claim 5, characterized in that, The over-temperature trigger is when the temperature of any flue heating surface exceeds the first design temperature threshold; the prediction trigger is when the predicted temperature of the flue heating surface at the next moment is greater than the second design temperature threshold and cannot be avoided by adjusting the full circumference baffle opening; the fault trigger is when one or more blades fail and other blade adjustments cannot compensate for the flow deviation to within the deviation threshold.

7. The method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler according to claim 4, characterized in that, S2 includes: calculating the required heat distribution ratio of the three flues based on the measured values ​​of the heating surface measuring points and the return parameters of the reheated steam in the secondary reheat boiler; determining the flow rate of each flue and obtaining the target value of the blade opening under the current operating condition based on the flow area-opening table; and calculating the blade opening increment based on the difference between the target value of the blade opening under the current operating condition and the target value of the blade opening under the next operating condition.

8. A method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler according to claim 4, 5, 6, or 7, characterized in that, After activating the desuperheating water spray plan: maintain the blade opening of the non-overheating flue, adjust the airflow path through the baffle, and release heat to the flue where the overheating degree is less than the overheating threshold; simultaneously calculate the expected external heat exchange volume generated by the flue gas flow at the next moment, convert it into the required desuperheating water volume, and then start the water spray.

9. A method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler according to claim 4, 5, 6, or 7, characterized in that, When establishing the flow area-opening table, the mapping relationship is established through flow resistance calculation or CFD.

10. A method for adjusting the full-circumference baffle structure of the three flues at the tail end of a secondary reheat boiler according to claim 4, 5, 6, or 7, characterized in that, The initial opening value for each blade is fully open.

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