Reheater flexible heating surface system and method

Abstract

The invention relates to the technical field of cogeneration equipment, in particular to a reheater flexible heating surface system and method, and the system comprises a double-loop reheater subsystem which comprises a first reheater and a second reheater which are connected in parallel; a steam inlet of the final-stage reheater is connected with a steam outlet of the double-loop reheater subsystem; the temperature adjusting subsystem is respectively connected with the double-loop reheater subsystem and the final-stage reheater; the double-loop reheater subsystem is provided with a valve set with a bidirectional flow adjusting function, and the valve set is used for conducting steam flow switching between the preset heat supply working condition and the preset pure condensing working condition. Therefore, the problems that an existing reheater cannot give consideration to flexible switching of the heat supply working condition and the pure condensing working condition, overtemperature pipe explosion is likely to happen, and oxide skin falling is likely to happen are solved, and through the design of the double-loop reheater and the cooperative temperature adjusting system, the operation safety, the heat supply flexibility and the energy efficiency of the supercritical coal-fired unit reheater are remarkably improved; meanwhile, oxide skin generation and nitrogen oxide emission are reduced.

Description

Technical Field

[0001] This application relates to the field of combined heat and power equipment technology, and in particular to a flexible heating surface system and method for a reheater. Background Technology

[0002] In coal-fired power generating units, the performance and safety of the boiler reheater are crucial. With increasing heating demands and frequent load changes, existing reheater designs are struggling to meet the fluctuations in working fluid flow caused by load variations, leading to decreased operating efficiency and increased energy consumption. On one hand, the frequent fluctuations in tube wall temperature (570-620℃) in existing boiler reheaters during operation cause accelerated oxide scale formation and shedding. This shed oxide scale accumulates at narrow bends in the tubes during steam flow, leading to tube overheating and rupture, seriously threatening the safe operation of the unit. Statistics show that over 60% of pipes have excessive oxide scale.

[0003] On the other hand, with the continuous growth of unit heating demand and the increasingly frequent load changes, the existing reheater design is difficult to adapt to flexible and varied operating conditions. When switching between heating and pure condensing conditions, the existing reheater will generate large thermal stress and temperature deviation due to the drastic changes in temperature and pressure, which increases the risk of equipment operation and may even affect the normal start-up, shutdown and operation of the unit. For example, in the operation of boilers in thermal power plants, when high-parameter heating needs to be met, the reheater has a high risk of overheating and cannot stably provide a large flow of heating steam, which greatly limits the heating capacity and operational flexibility of the unit.

[0004] Furthermore, given the energy shortage and increasingly stringent environmental requirements, the existing reheater designs of boilers are significantly inadequate in terms of energy conservation and emission reduction. Due to their limited heating capacity, they cannot efficiently meet the heat load demands of surrounding businesses, forcing some areas to still rely on small, high-pollution, and high-energy-consuming boilers to meet heating needs. This not only increases energy consumption but also exacerbates environmental pollution problems, which urgently need to be addressed. Summary of the Invention

[0005] This application provides a flexible reheating surface system and method for reheaters to solve problems such as oxide scale shedding, overheating and tube rupture, and difficulty in flexibly switching between heating and pure condensing conditions in existing reheaters of boilers in thermal power plants during long-term operation. Through the dual-loop reheater design and coordinated temperature control system, the operational safety, heating flexibility and energy efficiency of the reheater of supercritical coal-fired units are significantly improved, while reducing oxide scale formation and nitrogen oxide emissions.

[0006] The first aspect of this application provides a reheater flexible heating surface system, including the following steps: A dual-loop reheater subsystem, comprising a first reheater and a second reheater connected in parallel; The final stage reheater, wherein the steam inlet of the final stage reheater is connected to the steam outlet of the dual-loop reheater subsystem; A temperature control subsystem is connected to the dual-loop reheater subsystem and the final-stage reheater, respectively. The dual-loop reheater subsystem is equipped with a valve group with bidirectional flow regulation function, which is used to switch the steam flow between preset heating conditions and preset pure condensation conditions.

[0007] According to one embodiment of this application, the second reheater is fixed to the tail flue of the boiler by a hanging structure.

[0008] According to one embodiment of this application, the tube panel structure of the final stage reheater is a U-shaped structure.

[0009] According to one embodiment of this application, the temperature control subsystem includes: A de-heating component is provided on the cross connection pipe between the dual-loop reheater subsystem and the final stage reheater. The de-heating component is used to control the outlet steam temperature of the final stage reheater to be within a preset temperature range. Temperature sensing components are installed in the inlet header of the second reheater, the outlet header of the second reheater, and the tube panel structure of the final stage reheater, for monitoring the steam temperature of the inlet header of the second reheater, the steam temperature of the outlet header of the second reheater, and the tube wall temperature of the final stage reheater.

[0010] According to one embodiment of this application, the reheater flexible heating surface system further includes: A control subsystem, which is communicatively connected to the temperature sensing component, is used to adjust the water spray volume of the cooling component based on the temperature data sent by the temperature sensing component.

[0011] According to one embodiment of this application, the heat exchange tubes of the second reheater are arranged vertically.

[0012] According to one embodiment of this application, the reheater flexible heating surface system further includes: A safety protection component, comprising a safety valve and a pressure monitoring unit; The safety valve is used to automatically release pressure when the reheater flexible heating surface system meets the preset overpressure conditions; The pressure monitoring unit is used to monitor the pressure of the reheater flexible heating surface system.

[0013] According to the control system of the reheater flexible heating surface system provided in the embodiments of this application, by adding a heating surface (adding a low-temperature reheater) above the tail flue and before the vertical low-temperature superheater, and dividing the low-temperature reheater into two parts for operation, seamless switching between pure condensing and heating conditions is achieved. Simultaneously, the heating area of ​​the final reheater is reduced, the steam flow rate is increased, the reheater heating surface material is upgraded, the risk of oxide scale shedding is reduced, and the operational safety and reliability of the reheater are improved, meeting the operational requirements under both heating and pure condensing conditions.

[0014] A second aspect of this application provides a control method for a reheater flexible heating surface system, employing the aforementioned reheater flexible heating surface system, wherein the method includes the following steps: When the reheater flexible heating surface system is in the preset heating condition, the valve group controls all the cold reheat steam to flow into the first reheater, and the high-pressure heating steam is introduced into the second reheater for heating, and the steam heated by the second reheater is used to supply heat to the outside. When the flexible heating surface system of the reheater is in the preset pure condensation condition, a first preset proportion of cold reheat steam is introduced into the second reheater through the valve group, and a second preset proportion of cold reheat steam is introduced into the first reheater. The steam heated by the second reheater and the steam heated by the first reheater are mixed, and the mixed steam is input into the final stage reheater for heating.

[0015] According to one embodiment of this application, when the reheater flexible heating surface system is in the preset pure condensation condition, it further includes: Obtain the current unit load; Based on a preset adjustment strategy, the first preset ratio and the second preset ratio are dynamically adjusted according to the current unit load.

[0016] According to one embodiment of this application, when the reheater flexible heating surface system is in the preset heating condition, it further includes: The steam temperature of the inlet header and outlet header of the second reheater and the tube wall temperature of the final reheater are monitored using temperature sensing components. Based on the steam temperature of the inlet header and outlet header of the second reheater and the tube wall temperature of the final reheater, the water spray volume of the desuperheating component is adjusted by the control subsystem to control the outlet steam temperature of the final reheater to be within the preset temperature range.

[0017] According to the control method of the reheater flexible heating surface system provided in the embodiments of this application, by adding a heating surface (adding a low-temperature reheater) above the tail flue and before the vertical low-temperature superheater, and dividing the low-temperature reheater into two parts for operation, seamless switching between pure condensing and heating conditions is achieved. Simultaneously, the heating area of ​​the final reheater is reduced, the steam velocity is increased, the reheater heating surface material is upgraded, the risk of oxide scale shedding is reduced, and the operational safety and reliability of the reheater are improved, meeting the operational requirements under both heating and pure condensing conditions.

[0018] Compared with the prior art, the advantages of the present invention are as follows: 1) Regarding boiler operational safety, the addition of a low-temperature reheater above the tail flue and before the vertical low-temperature superheater, arranged vertically, effectively reduces the risk of fly ash wear and blockage on the tubes. Simultaneously, the tube material has been upgraded to an anti-oxidation and high-temperature resistant material, significantly reducing oxide scale shedding and lowering the risk of tube rupture caused by oxide scale blockage. Furthermore, the desuperheating water system added between the two reheaters allows for flexible control of steam temperature, preventing overheating and ensuring stable operation under different conditions. The valve switching system allows the newly added low-temperature reheater to flexibly adjust the steam flow direction according to operating conditions, ensuring stable unit operation under both conditions, greatly improving the flexibility and reliability of unit operation and meeting diverse operational needs.

[0019] 2) In terms of improving heating capacity, the minimum steam flow rate of the newly added low-temperature reheater is optimized according to the actual situation, which can flexibly adapt to the heating demand under different loads, effectively enhance the heating capacity of the unit, and provide a more stable and reliable heat source for surrounding enterprises.

[0020] 3) In terms of energy conservation and environmental protection, by optimizing the existing reheater system, the risk of reheater overheating is reduced, the boiler combustion adjustment is more stable, nitrogen oxide and dust emissions are reduced in a coordinated manner, the boiler thermal efficiency is improved, the unit heat consumption is reduced, and the energy consumption is reduced accordingly. This is of great significance for promoting energy conservation and emission reduction and achieving sustainable development of coal-fired power plants.

[0021] 4) In terms of economic benefits, this technology retains the original boiler steel frame and most of the pipes, and only adds a low-temperature reheater and some pipe fittings. This not only reduces the maintenance and replacement costs caused by equipment failure, but also improves the unit's operating efficiency, extends the service life of the equipment, and creates more economic value.

[0022] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a block diagram of a reheater flexible heating surface system according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a reheater flexible heating surface system according to an embodiment of this application; Figure 3 This is a flowchart of a control method for a reheater flexible heating surface system provided according to an embodiment of this application. Detailed Implementation

[0024] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0025] Those skilled in the art will understand that the modification of reducing the reheater heating surface in the background technology is an irreversible operation, resulting in a lower reheat steam temperature under pure condensing conditions (e.g., dropping to 530°C), affecting unit efficiency. Furthermore, simply increasing the desuperheating water flow rate in the background technology will exacerbate oxide scale formation and the risk of pipe cracking. In addition, the traditional flue gas damper adjustment precision is insufficient, with steam temperature control deviations reaching ±15°C.

[0026] It is evident that existing boiler reheater technology can no longer meet the comprehensive requirements of modern coal-fired power generating units in terms of safety, flexibility, efficiency, and environmental protection. There is an urgent need for a new type of boiler reheater technology to solve the above problems, improve the unit's operating performance, heating capacity, and economic benefits, while reducing environmental impact and meeting the dual demands of increasingly stringent policies and regulations and market development.

[0027] To address the problems faced by existing boiler reheaters during operation, such as scale shedding, overheating and tube rupture, and difficulty in flexibly switching between heating and condensing modes, this invention proposes a flexible heating surface technology for boiler reheaters in supercritical high-flow industrial heating units. This technology is particularly suitable for the retrofitting of boiler reheaters in coal-fired power plants, meeting the safety requirements of coal-fired power plants that frequently switch between heating and condensing modes. A new low-temperature reheater is added above the boiler tail flue and before the vertical low-temperature superheater, forming a dual-loop system in parallel with the original low-temperature reheater. A valve group with bidirectional flow regulation (response time ≤0.5s) enables seamless switching between operating modes. The new reheater tubes are vertically arranged with optimized outer diameters, and the final reheater uses a U-shaped tube screen to reduce scale formation. A coordinated temperature control system reduces steam temperature control deviation to ±5℃. Experimental data shows that the unit's heat consumption is reduced, nitrogen oxide emissions are decreased, the proportion of pipes with excessive scale is reduced, the safety, reliability, and flexibility of the reheater are improved, maintenance costs are reduced, and the energy-saving, high-efficiency, and environmentally friendly operation requirements of coal-fired power units are met.

[0028] The reheater flexible heating surface system and method of this application are described below with reference to the accompanying drawings.

[0029] Specifically, Figure 1 This is a block diagram of a reheater flexible heating surface system provided in an embodiment of this application.

[0030] like Figure 1 As shown, the reheater flexible heating surface system 10 includes: a dual-loop reheater subsystem 100, a final-stage reheater 200, and a temperature control subsystem 300.

[0031] The system includes a dual-loop reheater subsystem 100, which includes a first reheater and a second reheater connected in parallel; a final-stage reheater 200, whose steam inlet is connected to the steam outlet of the dual-loop reheater subsystem; and a temperature control subsystem 300, which is connected to both the dual-loop reheater subsystem and the final-stage reheater. The dual-loop reheater subsystem is equipped with a valve group that has bidirectional flow regulation function. The valve group is used to switch the steam flow between the preset heating condition and the preset pure condensing condition.

[0032] Specifically, the dual-loop reheater subsystem 100 of this application embodiment consists of the original low-temperature reheater (i.e., the first reheater) and a newly added low-temperature reheater (i.e., the second reheater) arranged in parallel before the vertical low-temperature superheater in the tail flue. The two are connected in parallel to achieve the steam flow switching between heating and pure condensing conditions through a valve group with bidirectional flow regulation function. The valve group switching response time is ≤0.5s, ensuring that the steam pressure fluctuation is ≤±2% and the temperature fluctuation is ≤±3% during the condition switching process. In the heating condition, all the cold reheat steam enters the original low-temperature reheater, and the high-pressure extracted steam is heated by the newly added low-temperature reheater before being supplied to the outside. In the pure condensing condition, 20%-30% of the cold reheat steam is diverted to the newly added low-temperature reheater, and the rest enters the original low-temperature reheater. After heating, they are mixed and enter the final reheater 200. The tube screen of the final reheater 200 is optimized to be a pure co-current heat exchange "U" shape design, which reduces the heating area by 15%-20%. The material of the outlet section tube can be SA-213S30432.

[0033] Furthermore, the temperature control subsystem 300 includes a reheater desuperheating water device arranged on the cross-connecting pipe between the two reheaters, and temperature sensors arranged at the inlet and outlet of the newly added low-temperature reheater and the tube panel of the final reheater 200. The desuperheating water device controls the steam temperature deviation at the outlet of the final reheater 200 to be ≤±5℃, and the temperature sensor measurement accuracy is ±0.5℃.

[0034] Optionally, in some embodiments, the second reheater is fixed to the tail flue of the boiler by a hanging structure, and the heat exchange tubes of the second reheater are arranged vertically.

[0035] Specifically, in this embodiment, a new low-temperature reheater (i.e., a second reheater) is added above the boiler tail flue and before the vertical low-temperature superheater, and fixed to the tail flue hanging pipe. This new low-temperature reheater operates in parallel with the original low-temperature reheater, and operates independently under pure condensing and heating conditions respectively. The new low-temperature reheater and the original low-temperature reheater achieve steam flow switching between heating and pure condensing conditions through a valve group with bidirectional flow regulation function.

[0036] Preferably, the tubes of the newly added low-temperature reheater are arranged vertically, that is, the tubes on the heating surface are arranged vertically; the pitch can be 300mm, the tube specifications can be Φ51×5, and the material can be 12Cr1MoVG. This arrangement and tube design can reduce fly ash adhesion and reduce the risk of wear.

[0037] The tube panels and the number of tubes per panel in the newly added low-temperature reheater can remain the same as the original design, but the outer diameter of the tubes will be reduced (e.g., from Φ51mm to Φ44.5mm) to increase the steam flow rate, enhance the cooling effect of the tubes, and prevent overheating. Meanwhile, the material of the tubes in the 200 outlet section of the final reheater will be upgraded to SA-213S30432. This material has better oxidation resistance and high-temperature resistance, effectively reducing oxide scale formation and extending the service life of the reheater.

[0038] Optionally, for supercritical units of different power levels, the minimum steam flow rate of the newly added low-temperature reheater can be designed within the following ranges: 50-80 t / h for 300MW units, 100-150 t / h for 600MW units, and 200-280 t / h for 1000MW units. This flow rate range can be determined based on the flue gas heat exchange efficiency formula (Q=K×A×Δt, where K is the heat transfer coefficient, A is the heat exchange area, and Δt is the logarithmic mean temperature difference) and experimental data from pilot units, which can meet the heating demand under different loads.

[0039] Optionally, in some embodiments, the tube panel structure of the final stage reheater 200 is a U-shaped structure.

[0040] Specifically, this application changes the tube panel arrangement of the final stage reheater 200 from a mixed counter-current heat exchange arrangement to a pure co-current heat exchange arrangement, adopting a simpler "U"-shaped design to reduce tube panel cracking. Simultaneously, it reduces the heating area of ​​the final stage reheater 200 (by 15%-20%), further increasing the steam velocity (by 25%). The material of the tubes at the outlet section of the final stage reheater 200 is upgraded; this material, when operating at 620℃, reduces the oxide scale formation rate by more than 50% compared to traditional materials, effectively reducing the risk of oxide scale shedding and enhancing the safety and reliability of the reheater operation.

[0041] Tests showed that the steam flow rate of the optimized final stage reheater 200 in this embodiment of the application was increased by 25% compared with that before the modification, and the oxide scale formation rate of the SA-213S30432 material tubes under 620℃ conditions was reduced by more than 50% compared with that of the 12Cr1MoVG material.

[0042] Optionally, in some embodiments, the temperature control subsystem 300 includes: a de-cooling component disposed on the cross-connection pipe between the dual-loop reheater subsystem 100 and the final reheater 200, the de-cooling component being used to control the outlet steam temperature of the final reheater 200 to be within a preset temperature range; and a temperature sensing component disposed on the inlet header of the second reheater, the outlet header of the second reheater, and the tube wall structure of the final reheater 200, for monitoring the steam temperature of the inlet header of the second reheater, the steam temperature of the outlet header of the second reheater, and the tube wall temperature of the final reheater 200.

[0043] Optionally, in some embodiments, the reheater flexible heating surface system 10 further includes: a control subsystem, which is communicatively connected to the temperature sensing component and is used to adjust the water spray volume of the de-cooling component based on the temperature data sent by the temperature sensing component.

[0044] Optionally, the diameter of the cross-connecting pipe of the temperature control subsystem 300 in this embodiment can be Φ108×8 and the material can be 20G.

[0045] Specifically, in this embodiment of the application, a desuperheating water system is set between the newly added low-temperature reheater and the original low-temperature reheater. When the steam temperature deviates from the set value by ±3℃, the desuperheating water flow rate is adjusted by 5-10t / h to regulate the steam temperature and prevent overheating.

[0046] Furthermore, the temperature control subsystem 300 of this embodiment can be arranged between the newly added low-temperature reheater and the original low-temperature reheater, as well as at other critical locations within the reheater. It automatically adjusts the flow rate of the desuperheating water according to actual operating parameters to ensure the steam temperature remains within a safe range. An additional desuperheating water path is added to the cross-connection pipe between the two reheaters. This desuperheating water system has a sensitive regulating effect on the wall temperature of the heated surface of the final reheater 200 and the steam temperature deviation on the left and right sides of the outlet of the final reheater 200. It can reduce the steam temperature control deviation from the traditional ±15℃ to ±5℃, effectively controlling the overheating risk caused by the reduced reheat steam flow rate after steam extraction, and ensuring the safe and stable operation of the reheater under different operating conditions.

[0047] Furthermore, temperature sensors are placed in key locations. For example, two temperature sensors are installed at the inlet and outlet headers of the newly added low-temperature reheater, and one wall temperature sensor is installed for every 10 tubes on the 200-tube panel of the final-stage reheater. These sensors monitor steam and tube wall temperatures in real time, with a sensor spacing of 1.5m and a signal transmission method of 4-20mA analog signal. When the temperature exceeds the safe range of 570-600℃, the automatic control system will promptly adjust the desuperheating water flow or steam flow to ensure the reheater operates within the safe temperature range. Simultaneously, safety valves and pressure monitoring devices are installed to prevent equipment damage due to excessive pressure. Optionally, in some embodiments, the reheater flexible heating surface system further includes: a safety protection component, which includes a safety valve and a pressure monitoring unit; wherein the safety valve is used to automatically depressurize when the reheater flexible heating surface system meets a preset overpressure condition; and the pressure monitoring unit is used to monitor the pressure of the reheater flexible heating surface system.

[0048] Optionally, in this embodiment, the safety valve opening pressure can be 1.05 times the design pressure, and the pressure monitoring device can measure a range of 0-4MPa with an accuracy of ±0.02MPa. Both are linked to the automatic control system.

[0049] Specifically, the safety protection component in this application embodiment is a key safety guarantee part of the reheater flexible heating surface system. It mainly consists of a safety valve and a pressure monitoring unit. Its core function is to monitor the system pressure in real time and actively intervene when the pressure rises abnormally to prevent the equipment from being damaged due to overpressure and ensure the safe and stable operation of the entire system.

[0050] The safety valve serves as the final protective barrier, with its activation setting at 1.05 times the system design pressure. When the internal system pressure continuously rises due to changes in operating conditions, sudden load changes, or other abnormal situations, and reaches this preset overpressure condition, the safety valve will immediately and automatically open to quickly release pressure, reducing it to within a safe range, thereby preventing permanent deformation or rupture accidents in pressure-bearing components such as pipelines and manifolds.

[0051] The pressure monitoring unit can be composed of high-precision pressure sensors, with a measurement range covering 0 to 4 MPa and a measurement accuracy of up to ±0.02 MPa, enabling continuous and accurate real-time monitoring of system pressure.

[0052] In addition, the pressure monitoring unit is directly linked to the unit's automatic control system, transmitting the collected pressure signals to the control center in real time. This provides operators with accurate data references and issues early warnings when the pressure approaches dangerous values, providing a basis for decision-making regarding the triggering of safety valves or the automatic adjustment of the system. This greatly improves the reliability and safety of the reheater system under complex operating conditions.

[0053] To facilitate a more intuitive understanding of the reheater flexible heating surface system proposed in this application by those skilled in the art, the following is combined with... Figure 2 Please provide a detailed explanation.

[0054] like Figure 2 As shown, steam is drawn from the high-pressure steam supply header, passes through a desuperheater with a water spray device, and then enters the new low-pressure recharge inlet header. It is then output through the new low-pressure recharge outlet header. The system uses multiple desuperheaters for instantaneous frequency regulation and temperature control. Shut-off valves, electric shut-off valves, electric regulating valves, and check valves are installed on the pipeline. A safety valve is also installed on the new low-pressure recharge outlet header section to ensure system safety.

[0055] The following details the workflow of the reheater flexible heating surface system according to the embodiments of this application under pure condensation and heating conditions.

[0056] Under pure condensation conditions, a portion of the cold reheat steam (approximately 20%-30% of the total steam volume) is introduced into the newly added low-temperature reheater to cool the tubes. The cooled steam mixes with the steam from the outlet of the original low-temperature reheater and then enters the final stage reheater 200 for heating before entering the intermediate-pressure cylinder of the turbine to perform work.

[0057] In heating operation, all cold reheat steam is heated in the original low-temperature reheater, while high-pressure heating extraction steam is heated to the required temperature in the newly added low-temperature reheater before being supplied to the outside. A valve switching system enables seamless switching between the two operating conditions, ensuring stable unit operation.

[0058] It should be noted that the minimum steam flow rate of the newly added low-temperature reheater in this embodiment is optimized according to actual conditions to meet the heating needs of the unit under different loads. By precisely controlling the steam flow rate and temperature, flexible heating adjustment is achieved, thereby improving the unit's heating capacity and operating efficiency.

[0059] In actual operation, operators can adjust the steam flow and desuperheating water flow of the newly added low-temperature reheater through the control system according to the unit's operating conditions and heat load requirements. Simultaneously, various operating parameters of the reheater, such as temperature, pressure, and flow rate, are monitored in real time to ensure the safe, stable, and efficient operation of the equipment. This technology can significantly improve the operational safety and reliability of boiler reheaters, reduce maintenance costs, extend equipment lifespan, and improve energy utilization efficiency, providing strong support for the energy-saving, efficient, flexible, and environmentally friendly operation of coal-fired power generating units.

[0060] Experimental verification shows that the 600MW supercritical unit using the reheater flexible heating surface system of this application has a monthly failure rate of ≤0.2 times during 18 consecutive months of operation, with the tube wall temperature controlled between 570-600℃ and the monthly heating steam flow fluctuation ≤±5%. When the system is applied to a supercritical coal-fired unit, the unit's heat consumption is reduced by approximately 6.25% compared to a traditional reheater system, the nitrogen oxide emission concentration is reduced by approximately 25%, and the proportion of pipes with excessive oxide scale is reduced to ≤15%.

[0061] The flexible reheater surface system proposed in this application adopts an integrated design of "dual-loop low-temperature reheater + optimized final-stage reheater + coordinated temperature control system". By adding a new stage of heating surface (a new low-temperature reheater) above the tail flue and before the vertical low-temperature superheater, and dividing the low-temperature reheater into two parts for operation, seamless switching between pure condensing and heating conditions is achieved. Simultaneously, the heating area of ​​the final-stage reheater is reduced, the steam velocity is increased, the reheater heating surface material is upgraded, the risk of oxide scale shedding is reduced, and the operational safety and reliability of the reheater are improved. Through thermodynamic system reconstruction and flow field optimization, flexible switching between heating and pure condensing conditions is achieved, meeting the operational requirements under both conditions.

[0062] Secondly, combine Figure 3 This application introduces the control method for the flexible heating surface system of the reheater.

[0063] In this embodiment, the control method for the reheater flexible heating surface system adopts the aforementioned reheater flexible heating surface system, wherein, as... Figure 3 As shown, the method includes the following steps: In step S301, when the reheater flexible heating surface system is in the preset heating condition, the valve group controls all the cold reheat steam to flow into the first reheater, and the high-pressure heating steam is introduced into the second reheater for heating, and the steam heated by the second reheater is used to supply heat to the outside.

[0064] In step S302, when the reheater flexible heating surface system is in a preset pure condensation condition, a first preset proportion of cold reheated steam is introduced into the second reheater through the valve group, and a second preset proportion of cold reheated steam is introduced into the first reheater. The steam heated by the second reheater and the steam heated by the first reheater are mixed, and the mixed steam is input into the final reheater for heating.

[0065] Furthermore, in some embodiments, when the reheater flexible heating surface system is in a preset pure condensing condition, the method further includes: obtaining the current unit load; and dynamically adjusting the first preset ratio and the second preset ratio according to the current unit load based on a preset adjustment strategy.

[0066] Furthermore, in some embodiments, when the reheater flexible heating surface system is in a preset heating condition, the method further includes: using temperature sensing components to monitor the steam temperature of the inlet header of the second reheater, the steam temperature of the outlet header, and the tube wall temperature of the final reheater; based on the steam temperature of the inlet header of the second reheater, the steam temperature of the outlet header, and the tube wall temperature of the final reheater, adjusting the water spray volume of the desuperheating component through a control subsystem to control the outlet steam temperature of the final reheater to be within a preset temperature range.

[0067] It should be noted that the foregoing explanation of the reheater flexible heating surface system embodiment also applies to the control method of the reheater flexible heating surface system in this embodiment, and will not be repeated here.

[0068] According to the control method of the reheater flexible heating surface system proposed in the embodiments of this application, an additional heating surface (a new low-temperature reheater) is added above the tail flue and before the vertical low-temperature superheater, and the low-temperature reheater is divided into two parts for operation, achieving seamless switching between pure condensing and heating conditions. Simultaneously, the heating area of ​​the final reheater is reduced, the steam velocity is increased, the reheater heating surface material is upgraded, the risk of oxide scale shedding is reduced, and the operational safety and reliability of the reheater are improved, meeting the operational requirements under both heating and pure condensing conditions.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] 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 at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0072] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0073] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0074] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0075] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0076] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A flexible heating surface system for a reheater, characterized in that, include: A dual-loop reheater subsystem, comprising a first reheater and a second reheater connected in parallel; The final stage reheater, wherein the steam inlet of the final stage reheater is connected to the steam outlet of the dual-loop reheater subsystem; A temperature control subsystem is connected to the dual-loop reheater subsystem and the final-stage reheater, respectively. The dual-loop reheater subsystem is equipped with a valve group with bidirectional flow regulation function, which is used to switch the steam flow between preset heating conditions and preset pure condensation conditions.

2. The system according to claim 1, characterized in that, The second reheater is fixed to the tail flue of the boiler by a hanging structure.

3. The system according to claim 1, characterized in that, The tube panel structure of the final stage reheater is a U-shaped structure.

4. The system according to claim 1, characterized in that, The temperature control subsystem includes: A de-heating component is provided on the cross connection pipe between the dual-loop reheater subsystem and the final stage reheater. The de-heating component is used to control the outlet steam temperature of the final stage reheater to be within a preset temperature range. Temperature sensing components are installed in the inlet header of the second reheater, the outlet header of the second reheater, and the tube panel structure of the final stage reheater, for monitoring the steam temperature of the inlet header of the second reheater, the steam temperature of the outlet header of the second reheater, and the tube wall temperature of the final stage reheater.

5. The system according to claim 4, characterized in that, Also includes: A control subsystem, which is communicatively connected to the temperature sensing component, is used to adjust the water spray volume of the cooling component based on the temperature data sent by the temperature sensing component.

6. The system according to claim 1, characterized in that, The heat exchange tubes of the second reheater are arranged vertically.

7. The system according to claim 1, characterized in that, Also includes: A safety protection component, comprising a safety valve and a pressure monitoring unit; The safety valve is used to automatically release pressure when the reheater flexible heating surface system meets the preset overpressure conditions; The pressure monitoring unit is used to monitor the pressure of the reheater flexible heating surface system.

8. A control method for a reheater flexible heating surface system, characterized in that, The reheater flexible heating surface system as described in any one of claims 1-7 is used, wherein the method includes the following steps: When the reheater flexible heating surface system is in the preset heating condition, the valve group controls all the cold reheat steam to flow into the first reheater, and the high-pressure heating steam is introduced into the second reheater for heating, and the steam heated by the second reheater is used to supply heat to the outside. When the flexible heating surface system of the reheater is in the preset pure condensation condition, a first preset proportion of cold reheat steam is introduced into the second reheater through the valve group, and a second preset proportion of cold reheat steam is introduced into the first reheater. The steam heated by the second reheater and the steam heated by the first reheater are mixed, and the mixed steam is input into the final stage reheater for heating.

9. The method according to claim 8, characterized in that, When the reheater flexible heating surface system is in the preset pure condensation condition, it further includes: Obtain the current unit load; Based on a preset adjustment strategy, the first preset ratio and the second preset ratio are dynamically adjusted according to the current unit load.

10. The method according to claim 8, characterized in that, When the reheater flexible heating surface system is in the preset heating condition, it further includes: The steam temperature of the inlet header and outlet header of the second reheater and the tube wall temperature of the final reheater are monitored using temperature sensing components. Based on the steam temperature of the inlet header and outlet header of the second reheater and the tube wall temperature of the final reheater, the water spray volume of the desuperheating component is adjusted by the control subsystem to control the outlet steam temperature of the final reheater to be within the preset temperature range.

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