Natural circulation boiler internal circulation pump heating pump system

Abstract

This utility model discloses a warm-up system for an internal circulation pump in a natural circulation boiler, belonging to the technical field of boiler auxiliary equipment. It includes an internal circulation pump, a pre-pump pipeline and a post-pump pipeline respectively equipped with a first valve and a second valve connecting the downcomer to the economizer, a third valve connecting the lower part of the downcomer to the economizer inlet via a pipeline, a warm-up connection pipeline connecting the upstream of the second valve and the upstream of the third valve, and a flow meter, a fourth valve, and a regulating valve arranged sequentially. When the internal circulation pump is in standby mode, the first valve is kept open and the third valve closed, the fourth valve is opened, the electric regulating valve is opened, and the second valve is closed. The working fluid in the downcomer bypasses the pump through the pre-pump pipeline, the internal circulation pump, the post-pump pipeline, the warm-up connection pipeline, and the economizer recirculation pipeline, forming a closed natural circulation loop with the boiler evaporation system. This keeps the pump body hot and at the same temperature as the working fluid during standby. This system is mainly used in natural circulation boilers to maintain the internal circulation pump in a hot standby state, eliminating the risk of thermal shock during pump start-up.

Description

Technical Field

[0001] This utility model relates to the field of boiler auxiliary equipment technology. More specifically, this utility model relates to an internal circulation pump warming system for a natural circulation boiler. Background Technology

[0002] In natural circulation boilers, a hot water internal circulation system is often added to meet the denitrification requirements under wide loads. This system uses an internal circulation pump to deliver high-temperature working fluid to the economizer inlet to increase the flue gas temperature at the denitrification inlet. The internal circulation pump needs to be kept in a hot standby state for a long time to avoid equipment damage caused by excessive temperature difference between the pump body and the working fluid during startup.

[0003] In existing technologies, ultracritical (supercritical) boilers employ a reverse warming pump system (water is drawn from the economizer outlet and flows in the opposite direction through the pump body), which relies on the high resistance of the evaporation system to create the pressure differential required to drive the warming pump flow. However, the evaporation system resistance of natural circulation boilers is significantly lower, causing the reverse warming pump mode to fail to establish an effective circulation.

[0004] 1. Insufficient pressure difference: The natural circulation system relies on the density difference of the working fluid for driving, and the pressure difference is much lower than that of the forced circulation system, so it cannot drive the reverse warm pump water flow;

[0005] 2. Warm-up pump failure: The working fluid cannot continuously flow through the standby pump body, and the pump body temperature gradually drops to the ambient temperature, forming a temperature difference of >100℃ with the high-temperature working fluid;

[0006] 3. Equipment damage risk: Severe thermal shock during pump startup can easily lead to seal failure, bearing deformation, pump casing cracks, or even motor damage.

[0007] Previously, when attempting to transplant the reverse warming pump technology, the inherent low resistance characteristics of the natural circulation system made it impossible to solve the problem of warming pump water flow drive, resulting in a long-term lack of a reliable thermal backup solution for the internal circulation pump. Utility Model Content

[0008] One objective of this utility model is to provide an internal circulation pump heating system for a natural circulation boiler, comprising:

[0009] Internal circulation pump;

[0010] The downstream end of the pre-pump pipeline is connected to the inlet of the internal circulation pump, and the upstream end of the pre-pump pipeline is connected to a downcomer. The pre-pump pipeline is equipped with a first valve.

[0011] The downstream pipeline is connected to the outlet of the internal circulation pump at its upstream end and to the inlet of the economizer at its downstream end. A second valve is installed on the downstream pipeline.

[0012] The upstream end of the economizer recirculation pipeline is connected to the lower part of the downcomer, and the downstream end of the economizer recirculation pipeline is connected to the economizer inlet through a pipeline. A third valve is installed on the economizer recirculation pipeline.

[0013] The inlet end of the warm pump connecting pipeline is connected to the downstream pipeline, and the connection point is located upstream of the second valve. The outlet end of the warm pump connecting pipeline is connected to the economizer recirculation pipeline, and the connection point is located upstream of the third valve, forming a downcomer bypass. A flow meter, a fourth valve, and an electric regulating valve are installed sequentially along the direction from the inlet end to the outlet end of the warm pump connecting pipeline.

[0014] When the internal circulation pump is in standby mode, the first valve is kept open and the third valve is closed, the fourth valve is opened, the electric regulating valve is opened and the second valve is closed. The working fluid in the downcomer passes through the pipeline before the pump, the internal circulation pump, the pipeline after the pump, the warm pump connection pipeline, and the economizer recirculation pipeline to form a bypass, and then forms a closed natural circulation loop with the boiler evaporation system, so that the pump body of the internal circulation pump is kept hot and the temperature is consistent with the working fluid when in standby mode.

[0015] Preferably, a pump inlet medium temperature sensor is provided on the pipeline in front of the pump, and the pump inlet medium temperature sensor is located downstream of the first valve.

[0016] A downstream medium temperature sensor is installed on the downstream pipeline, and the downstream medium temperature sensor is located between the outlet of the internal circulation pump and the inlet of the warm-up connection pipeline.

[0017] Preferably, the flow meter and the electric regulating valve are respectively connected to the controller via electrical signals;

[0018] Specifically, when the flow meter detects a flow rate > 10t / h, the controller controls the electric regulating valve to reduce its opening.

[0019] When the temperature difference between the pump inlet temperature detected by the pump inlet temperature sensor and the pump outlet temperature detected by the pump outlet temperature sensor exceeds the preset temperature difference, the controller controls the electric regulating valve to open wider.

[0020] Preferably, it also includes:

[0021] The boiler drum has its water outlet end connected to a downcomer, which in turn connects to the pipeline before the pump via a welded pipe seat. A wall temperature sensor is installed on the lower wall of the boiler drum.

[0022] When the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor and the boiler drum wall temperature detected by the wall temperature sensor is less than or equal to the preset temperature difference, and the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor and the pump outlet temperature detected by the pump outlet medium temperature sensor is less than or equal to the preset temperature difference, the pump warm-up system is deemed to be operating effectively.

[0023] Preferably, it also includes:

[0024] The lower header has its inlet end connected to the downcomer via a pipeline, and its outlet end connected to the boiler drum via an ascender, forming an evaporation circuit.

[0025] This utility model has at least the following beneficial effects:

[0026] First, this utility model forms a downcomer bypass through the warm-up pump connection pipeline, so that when the internal circulation pump is stopped, a small part of the working fluid still flows through the pump body, keeping the pump body temperature basically the same as the working fluid temperature in the downcomer (the temperature difference is usually less than 5℃), meeting the need for immediate commissioning, ensuring that the internal circulation pump is in a hot standby state, avoiding thermal stress impact caused by excessive temperature difference during startup, and extending the service life of the pump body.

[0027] Secondly, this utility model uses dual temperature difference monitoring (temperature difference between pump inlet / outlet medium temperature sensor and boiler drum wall temperature sensor ≤ 5℃, temperature difference between pump inlet temperature and boiler drum wall temperature ≤ 5℃) to ensure the comprehensiveness of the pump warm-up effect, avoid misjudgment caused by error of a single measuring point, and accurately control the thermal state of the pump body.

[0028] Third, this utility model stabilizes the warm-up pump flow rate at 5-10t / h through closed-loop control of the electric regulating valve and flow meter, ensuring that the bypass water volume of the warm-up pump does not affect the safety of the boiler water circulation. When the flow rate is greater than 10t / h, the valve is closed; when the temperature difference is greater than the preset value (e.g., 5℃), the flow rate is increased, realizing automated regulation of the warm-up pump process. It has a short response time, high regulation accuracy, and a graded regulation logic (closing the valve step by step when the flow rate exceeds the limit by 5%, and opening the valve step by step when the temperature difference exceeds the limit by 10%), which balances regulation efficiency and system stability, reduces valve wear, and ensures uniform heating of the pump body.

[0029] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the internal circulation pump heating system of the natural circulation boiler according to one of the technical solutions of this utility model.

[0031] The markings in the attached diagram are as follows:

[0032] 1. Boiler drum; 2. Downcomer; 3. Lower header; 4. Riser; 5. Economizer; 6. Economizer recirculation line; 7. Pre-pump line; 8. Internal circulation pump; 9. Post-pump line; 10. Warm-up connection line; 11. First valve; 12. Second valve; 13. Third valve; 14. Fourth valve; 15. Electric regulating valve; 16. Wall temperature sensor; 17. Pre-pump medium temperature sensor; 18. Post-pump medium temperature sensor; 19. Flow meter. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0034] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this utility model, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0035] like Figure 1 As shown, this utility model provides an internal circulation pump warm-up system for a natural circulation boiler, comprising:

[0036] Internal circulation pump 8; Specifically, internal circulation pump 8 is a vertical single-stage centrifugal pump, which is suitable for situations where the inlet water temperature of the economizer is increased in a natural circulation boiler, thereby increasing the inlet flue gas temperature of the denitrification device.

[0037] The upstream pipeline 7 is connected to the inlet of the internal circulation pump 8 at its downstream end, and a downcomer 2 is connected to the upstream end of the upstream pipeline 7. A first valve 11 is provided on the upstream pipeline 7. Specifically, the upstream end of the upstream pipeline 7 is connected to the upper part of the downcomer 2, and the downstream end is connected to the inlet of the internal circulation pump 8. The material can be carbon steel or alloy steel. The first valve 11 on the upstream pipeline 7 can be an electric gate valve, which is convenient for remote control of on / off.

[0038] The downstream pipeline 9 is connected to the outlet of the internal circulation pump 8 at its upstream end and to the inlet of the economizer 5 at its downstream end. A second valve 12 is provided on the downstream pipeline 9. Specifically, the upstream end of the downstream pipeline 9 is connected to the outlet of the internal circulation pump 8 and the downstream end is connected to the inlet of the economizer 5. The material can also be carbon steel or alloy steel. The second valve 12 can be an electric shut-off valve for on / off switching, which is convenient for remote control.

[0039] Economizer recirculation line 6 is connected upstream to the lower part of downcomer 2 and downstream to the inlet of economizer 5. A third valve 13 is provided on economizer recirculation line 6. Specifically, the upstream end of economizer recirculation line 6 is connected to the lower part of downcomer 2 and the downstream end is connected to the inlet of economizer 5. The third valve 13 can be an electric gate valve that is only opened when the boiler is started.

[0040] The warm pump connecting pipeline 10 has its inlet end connected to the downstream pipeline 9, with the connection point located upstream of the second valve 12. The outlet end of the warm pump connecting pipeline 10 is connected to the economizer recirculation pipeline 6, with the connection point located on the pipeline connecting the third valve 13 and the downcomer 2, forming a bypass for the downcomer 2. A flow meter 19, a fourth valve 14, and an electric regulating valve 15 are sequentially installed on the warm pump connecting pipeline 10 from the inlet end to the outlet end. Specifically, the inlet end of the warm pump connecting pipeline 10 is connected upstream of the second valve 12 on the downstream pipeline 9, and the outlet end is connected upstream of the third valve 13 on the economizer recirculation pipeline 6. An electromagnetic flow meter 19, a fourth valve 14, and an electric regulating valve 15 can be sequentially installed on the warm pump connecting pipeline 10 to monitor the flow rate, control the on / off state, and regulate the flow rate, respectively.

[0041] When the internal circulation pump 8 is in standby mode, the first valve 11 is kept open, the second valve 12 is opened, the third valve 13 is kept closed, the fourth valve 14 is opened, and the electric regulating valve 15 is opened (to a certain degree). The working fluid in the downcomer 2 bypasses the pump front pipeline 7, the internal circulation pump 8, the pump back pipeline 9, the warm pump connection pipeline 10, and the economizer recirculation pipeline 6, and then forms a closed loop with the boiler evaporation system to maintain the pump body temperature of the internal circulation pump 8 and the working fluid temperature in the downcomer 2.

[0042] The internal circulation pump 8 should be installed vertically, suspended by the pump inlet pipeline. The upstream pipeline 7 should be as long and straight as possible to reduce the number of bends, avoid uneven flow field of the working fluid inside the pipe, and improve the net effective positive pressure head of the working fluid at the pump inlet. The first valve 11 is installed away from the inlet of the internal circulation pump 8 to reduce uneven flow field of the pump working fluid. The second valve 12 on the downstream pipeline 9 is installed between the interface of the warm-up pump connecting pipeline 10 and the economizer 5 to ensure that the warm-up pump bypass and the main circuit can be controlled independently or interlocked. The third valve 13 on the economizer recirculation pipeline 6 is installed near the inlet of the economizer 5. At the end, the connection points of the heating pump connecting pipeline 10 with the downstream pipeline 9 and the economizer recirculation pipeline 6 can be located upstream of the second valve 12 and on the connecting pipeline between the third valve 13 and the downcomer 2, respectively. Welded connections are used to ensure sealing. The flow meter 19 on the heating pump connecting pipeline 10 is installed at a straight pipe section 5 times the pipe diameter at the inlet end of the heating pump connecting pipeline 10. The electric regulating valve 15 is installed downstream of the flow meter 19, at least 5 times the pipe diameter away from the flow meter 19, to ensure measurement accuracy and regulation effect. In terms of parameter setting, the heating pump water flow rate is controlled at 5~10t / h through the electric regulating valve 15.

[0043] In the above technical solution, when the internal circulation pump 8 is in standby mode, the first valve 11 (electric gate valve) on the upstream pipeline 7 is kept open, the second valve 12 (electric shut-off valve) on the downstream pipeline 9 is closed, the third valve 13 (electric gate valve) on the economizer recirculation pipeline 6 is kept closed, and the fourth valve 14 (electric shut-off valve) and the electric regulating valve 15 (at a certain opening) on ​​the warm pump connecting pipeline 10 are opened at the same time. At this time, the working fluid in the downcomer 2 flows into the internal circulation pump 8 through the upstream pipeline 7. Since the main valve of the downstream pipeline 9 is closed, the working fluid enters the warm pump connecting pipeline 10 through the interface of the downstream pipeline 9 and the warm pump connecting pipeline 10. After the flow rate is regulated by the flow meter 19 and the electric regulating valve 15, it returns to the lower part of the downcomer 2 through the economizer recirculation pipeline 6, forming a bypass of the downcomer 2. Finally, it merges with the original boiler evaporation system to form a closed loop of warm pump water circulation. During the circulation process, the electromagnetic flowmeter 19 monitors the flow rate in real time. If the flow rate exceeds 10 t / h, the electric regulating valve 15 automatically closes its opening; if the temperature difference exceeds 5℃, the opening is increased until the warm-up requirements are met. This warm-up process utilizes the pressure difference formed by the density difference of the natural circulation system to drive the working fluid flow, requiring no additional power. This keeps the temperature of the internal circulation pump 8 at a level close to the working fluid temperature in the downcomer 2 (temperature difference ≤ 5℃), far below the pump manufacturer's requirement of a 56℃ temperature difference upper limit. When the internal circulation pump 8 needs to be started, first close the electric regulating valve 15 and the fourth valve 14 on the warm-up connection pipeline 10, keep the first valve 11 open, and then open the second valve 12 to switch to normal internal circulation operation. This system, through positive warm-up circulation, solves the problem of reverse warm-up pump failure caused by the low resistance of the evaporation system in natural circulation boilers, ensuring that the internal circulation pump 8 is always in a hot standby state, reducing the thermal stress impact during startup, extending the service life of the equipment, and providing stable support for wide-load denitrification during deep peak shaving of the boiler.

[0044] In another technical solution, a pump inlet medium temperature sensor 17 is provided on the pump inlet pipeline 7, and the pump inlet medium temperature sensor 17 is located downstream of the first valve 11.

[0045] A downstream medium temperature sensor 18 is installed on the downstream pipeline 9, and the downstream medium temperature sensor 18 is located between the outlet of the internal circulation pump 8 and the inlet of the warm-up connection pipeline 10. Specifically, both the upstream medium temperature sensor 17 and the downstream medium temperature sensor 18 can be thermocouple temperature sensors with a measurement range of 0~400℃, which can meet the measurement requirements of the boiler working fluid temperature. The upstream medium temperature sensor 17 is located downstream of the first valve 11, and the specific installation position can be at a straight pipe section of the upstream pipeline 7 about 1000mm from the inlet of the internal circulation pump 8. The fluid is stable at this location, which facilitates accurate measurement of the working fluid. Temperature: The downstream medium temperature sensor 18 is located between the outlet of the internal circulation pump 8 and the inlet of the warm-up connection pipeline 10. Specifically, it can be installed on a straight pipe section about 1000mm after the outlet of the internal circulation pump 8 in the downstream pipeline 9, and about 1000mm upstream of the inlet of the warm-up connection pipeline 10. During operation, when the internal circulation pump 8 is in standby mode, the upstream medium temperature sensor 17 monitors the working medium temperature in the upstream pipeline 7 in real time, and the downstream medium temperature sensor 18 monitors the working medium temperature in the downstream pipeline 9. By comparing the difference between the upstream and downstream temperatures, the operating effect of the warm-up system is judged. When setting parameters, if the temperature difference between the two does not exceed 5℃, the warm-up pump is considered to be working well, and the internal circulation pump 8 is in hot standby mode. If the temperature difference exceeds this threshold, the warm-up pump water flow rate (usually controlled at 5~10t / h) can be adjusted by adjusting the opening of the electric regulating valve 15 on the warm-up pump connecting pipeline 10 until the temperature difference meets the requirements. This temperature monitoring method can intuitively reflect the temperature matching between the internal circulation pump 8 and the working fluid, providing accurate data support for the operation and control of the warm-up pump system, ensuring that the pump body temperature is consistent with the working fluid temperature, avoiding thermal stress in the pump body due to excessive temperature difference, thereby extending the service life of the internal circulation pump 8 and improving the safety and stability of system operation.

[0046] In another technical solution, the flow meter 19 and the electric regulating valve 15 are respectively connected to the controller via electrical signals;

[0047] When the flow meter 19 detects a flow rate > 10t / h, the controller controls the electric regulating valve 15 to close the opening, so that the flow rate of the bypass heating pump is as small as possible while meeting the heating pump demand, so as not to have an adverse effect on the boiler water circulation.

[0048] When the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor 17 and the pump outlet temperature detected by the pump outlet medium temperature sensor 18 is greater than the preset temperature difference, the controller controls the electric regulating valve 15 to open wider.

[0049] Specifically, the regulating valve on the heating pump connecting pipeline 10 can be an electric regulating valve 15, with a regulating accuracy of ±2% and a response time of less than 10 seconds, suitable for real-time flow regulation scenarios. The flow meter 19 and the electric regulating valve 15 are connected via a 4~20mA current signal or an RS485 digital signal to ensure the stability and accuracy of data transmission. The flow meter 19 and the electric regulating valve 15 should be installed sequentially from the inlet to the outlet of the heating pump connecting pipeline 10. The flow meter 19 should be installed at least 5 times the pipe diameter of the pipeline inlet, and the electric regulating valve 15 should be installed at least 5 times the pipe diameter downstream of the flow meter 19 to ensure the accuracy of measurement and regulation. During the process, when the flow meter 19 detects that the warm pump water flow rate is greater than 10t / h, it sends a signal to the controller. The controller then sends an electrical signal to the electric regulating valve 15. Upon receiving the signal, the electric regulating valve 15 automatically closes its opening to reduce the bypass circulation flow. When the temperature difference between the pump inlet temperature detected by the pump inlet temperature sensor 17 and the pump outlet temperature detected by the pump outlet temperature sensor 18 is greater than the preset temperature difference, it indicates that the warm pump effect is insufficient. The flow meter 19 will trigger the electric regulating valve 15 to open its opening wider, increasing the circulation flow rate until the temperature difference is reduced to the preset range. Through this closed-loop control method, the system can automatically adjust the warm pump water flow rate to maintain the pump body temperature of the internal circulation pump 8 consistent with the working fluid temperature. This control method improves the automation level and adjustment accuracy of the warm pump system, avoids the lag of manual intervention, ensures that the internal circulation pump 8 is always in a stable hot standby state in standby mode, effectively reduces the thermal stress caused by temperature difference in the pump body, extends the service life of the equipment, and ensures the safety and reliability of the boiler system operation.

[0050] Another technical solution also includes:

[0051] Boiler drum 1 has its water outlet end connected to downcomer 2. Downcomer 2 is connected to the pipeline 7 before the pump via a welded pipe seat. A wall temperature sensor 16 is installed on the lower wall of boiler drum 1.

[0052] When the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor 17 and the boiler drum wall temperature detected by the wall temperature sensor 16 is less than or equal to the preset temperature difference, and the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor 17 and the pump outlet temperature detected by the pump outlet medium temperature sensor 18 is less than or equal to the preset temperature difference, the warm-up pump system is deemed to be operating effectively. Specifically, the boiler drum 1, as the core component of the natural circulation system, can be made of high-pressure steel plate for boilers to meet the requirements of high-temperature and high-pressure operating conditions. The water outlet end of the boiler drum 1 is connected to the downcomer 2, and the downcomer 2 is connected to the pump inlet pipeline 7 through a welded pipe seat. The lower wall temperature sensor 16 of the boiler drum 1 can be a K-type thermocouple or a Pt100 resistance temperature sensor with a measurement range of 0~400℃. It is installed near the center of the bottom of the boiler drum 1 to ensure accurate reflection of the boiler drum wall temperature. The connection position between the downcomer 2 and the water outlet end of the boiler drum 1 is... Bottom of the boiler drum; the interface between the pump inlet pipeline 7 and the downcomer 2 is located on the upper part of the downcomer 2. The wall temperature sensor 16 is fixed to the outer surface of the lower wall of the boiler drum 1 by welding or threaded connection. The sensor probe must be in close contact with the wall surface to avoid air gaps affecting the measurement accuracy. The signal cables of all types of temperature sensors are high-temperature shielded cables, which are arranged and fixed along the boiler pipeline to prevent vibration and wear. The preset temperature difference can be 5℃. When the internal circulation pump 8 is in standby mode, the warm pump system heats the pump body through the natural circulation formed by the bypass and the boiler evaporation system. At this time, the water in the boiler drum 1 flows into the pump inlet pipeline 7 through the downcomer 2. The wall temperature sensor 16 monitors the temperature of the lower wall of the boiler drum 1 in real time (reflecting the temperature of the working fluid in the boiler drum 1). The pump inlet medium temperature sensor 17 monitors the temperature of the working fluid flowing into the internal circulation pump 8. The pump outlet medium temperature sensor 18 monitors the temperature of the working fluid after passing through the pump body. The system judges the warm-up effect by comparing two sets of temperature differences: if the temperature difference between the pump inlet temperature and the boiler drum wall temperature is ≤5℃, and the temperature difference between the pump inlet temperature and the pump outlet temperature is ≤5℃, it indicates that the pump body has been uniformly heated and the warm-up system is operating effectively; if the temperature difference exceeds 5℃, the warm-up flow rate is automatically adjusted by the electric regulating valve 15 until the temperature difference meets the requirements. This dual monitoring mechanism ensures the comprehensiveness of the warm-up effect, avoids misjudgment due to errors at a single measuring point, and thus accurately controls the pump body temperature to be consistent with the working fluid temperature, effectively reducing the thermal stress of the pump body during startup, extending the service life of the equipment, and providing a reliable guarantee for the rapid commissioning of the internal circulation pump 8 during deep peak shaving of the boiler.

[0053] In another technical solution, a lower header 3 is also included. Its inlet end is connected to the downcomer 2 via a pipeline, and its outlet end is connected to the boiler drum 1 via an ascender 4, forming an evaporation loop. Specifically, the lower header 3 can be a cylindrical pressure component, made of boiler-grade carbon steel or low-alloy steel to meet the requirements of high-temperature and high-pressure conditions. The inlet end of the lower header 3 is connected to the economizer downcomer 2. The ascender 4 can be a seamless steel pipe, the number of which is designed according to the boiler capacity. Multiple pipe joints can be installed on the lower header 3 to connect to the ascender 4. The pipe joints are welded to ensure sealing. The economizer recirculation pipeline 6 is connected to the lower part of the downcomer 2. The ascender 4 is led out from the outlet end of the lower header 3, arranged vertically upwards, and connected to the boiler drum 1 via the upper header or connecting pipe, forming a natural circulation loop. All connections are made by welding.

[0054] Although not covered by this application, the technical solution may include the following technical details to achieve more technical effects:

[0055] A control method for the internal circulation pump warm-up system of the natural circulation boiler, comprising:

[0056] S1, Warm-up mode activated: When the internal circulation pump 8 needs to enter standby mode, keep the first valve 11 open, open the fourth valve 14, close the second valve 12, and keep the third valve 13 closed.

[0057] S2. Dynamic adjustment of warm pump flow: By adjusting the opening of the electric regulating valve 15, the detection value of the flow meter 19 is stabilized within the range of 5~10t / h.

[0058] S3. Temperature difference verification: Real-time comparison of the temperature before pump, the temperature after pump, and the boiler drum wall temperature. If the temperature difference between any two points is greater than the preset temperature difference, return to step S2 to readjust the opening of the electric regulating valve 15.

[0059] Specifically, when the internal circulation pump 8 needs to enter standby mode, the first valve 11 is kept open and the third valve 13 is kept closed. The control system issues a command to open the fourth valve 14 (such as an electric shut-off valve) and close the second valve 12 (such as an electric shut-off valve). The electric regulating valve 15 can be a straight-through single-seat regulating valve. The actuator can be electric or pneumatic, and the input signal is 4~20mA. The flow meter 19 can be an electromagnetic flow meter 19 or an ultrasonic flow meter 19, with a diameter matching the warm pump connection pipeline 10. It outputs a 4~20mA signal to the control system. During the initialization of the control system, the opening of the electric regulating valve 15 is set to an initial value of 30%~50%, and the bypass circulation is started. The flow meter 19 monitors the flow data in real time. If the detected value is lower than 5t / h, the control system increases the opening of the electric regulating valve 15 proportionally; if it is higher than 10t / h, the opening is reduced. The adjustment step can be 1%~5%, and the adjustment cycle can be 5~10 seconds. At the same time, the upstream medium temperature sensor 17, the downstream medium temperature sensor 18, and the wall temperature sensor 16 collect temperature data at a sampling frequency of 0.5~1 second, and the control system calculates the temperature difference value. If the temperature difference between the pump inlet and outlet is greater than 5℃, or the temperature difference between the pump inlet and boiler drum wall is greater than 5℃, flow rate readjustment is triggered until the temperature difference is ≤5℃. Tests on a 300MW natural circulation boiler show that this control method can stabilize the temperature deviation between the internal circulation pump 8 and the working fluid temperature in the boiler drum 1 within ±5℃ in standby mode. By adjusting the opening of the electric regulating valve 15, the warm-up flow rate can be precisely controlled within the range of 5~10t / h, with a response time of less than 30 seconds. Through dual closed-loop regulation of flow rate and temperature difference, the stability and reliability of the warm-up process are ensured, providing a guarantee for the safe operation of the internal circulation pump in the natural circulation boiler.

[0060] In another technical solution, the dynamic adjustment in S2 specifically includes:

[0061] When the flow rate detected by flow meter 19 is greater than 10t / h, the electric regulating valve 15 is closed in 5% increments.

[0062] When the temperature difference between the pump inlet temperature and the pump outlet temperature is greater than 5℃, the electric regulating valve 15 is opened in 10% increments each time.

[0063] Specifically, the control system can use a PLC or DCS controller, equipped with analog input / output modules and logic operation functions, supporting PID control algorithms. In warm-up mode, if the flow meter 19 detects a flow rate exceeding 10 t / h, the control system triggers the electric regulating valve 15 to decrease its opening by 5% at a time. For example, if the current opening is 60%, it is initially adjusted to 55%. If the flow rate still exceeds the limit after a 10-second interval, the adjustment continues until the flow rate is ≤10 t / h. When the temperature difference between the upstream medium temperature sensor 17 and the downstream medium temperature sensor 18 is >5℃, it indicates uneven heating of the pump body. The control system then instructs the electric regulating valve 15 to decrease its opening by 10% at a time. Increase the opening, for example, when the current opening is 40%, adjust it to 50% for the first time. If the temperature difference is still >5℃ after an interval of 10 seconds, continue to adjust until the temperature difference is ≤5℃. In step S3, when the temperature difference between the pump inlet temperature and the pump outlet temperature, and between the pump inlet temperature and the boiler drum wall temperature are all ≤5℃, it is determined that the warm pump is effective and the adjustment is stopped. Through the graded adjustment strategy, the system can accurately control the warm pump flow under different operating conditions. This method balances the adjustment efficiency and system stability through differentiated adjustment steps, reduces valve wear, and ensures that the internal circulation pump 8 is always in the best hot standby state in the standby state. It effectively reduces the risk of thermal shock during startup and improves the safety and reliability of the boiler system.

[0064] In another technical solution, when the pump inlet medium temperature sensor 17 fails, the boiler drum wall temperature is used instead of the pump inlet temperature.

[0065] At this time, the preset temperature difference value is increased by 2~3℃, while the set value of flow meter 19 remains unchanged. Specifically, when the pump inlet medium temperature sensor 17 fails, the control system issues an alarm signal and switches to boiler drum wall temperature data. At this time, the temperature difference judgment logic is adjusted to the difference between the boiler drum wall temperature and the pump outlet temperature ≤7~8℃. In a test of a 300MW natural circulation boiler, a simulated pump inlet temperature sensor disconnection fault was performed. The system automatically switched to boiler drum wall temperature as a substitute. The temperature difference between the boiler drum wall temperature and the pump outlet temperature gradually decreased from the initial 9℃ to 7.5℃, meeting the adjusted threshold requirement. The warm pump effect was maintained through parameter compensation, avoiding system shutdown due to single-point failure, improving the robustness of the control logic and the reliability of boiler operation, and ensuring that the internal circulation pump 8 can still achieve hot standby management under abnormal equipment conditions.

[0066] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this utility model. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A natural circulation boiler's internal circulation pump warm-up system, characterized in that, include: Internal circulation pump; The downstream end of the pre-pump pipeline is connected to the inlet of the internal circulation pump, and the upstream end of the pre-pump pipeline is connected to a downcomer. The pre-pump pipeline is equipped with a first valve. The downstream pipeline is connected to the outlet of the internal circulation pump at its upstream end and to the inlet of the economizer at its downstream end. A second valve is installed on the downstream pipeline. The upstream end of the economizer recirculation pipeline is connected to the lower part of the downcomer, and the downstream end of the economizer recirculation pipeline is connected to the economizer inlet through a pipeline. A third valve is installed on the economizer recirculation pipeline. The inlet end of the warm pump connecting pipeline is connected to the downstream pipeline, and the connection point is located upstream of the second valve. The outlet end of the warm pump connecting pipeline is connected to the economizer recirculation pipeline, and the connection point is located upstream of the third valve, forming a downcomer bypass. A flow meter, a fourth valve, and an electric regulating valve are installed sequentially along the direction from the inlet end to the outlet end of the warm pump connecting pipeline. When the internal circulation pump is in standby mode, the first valve is kept open and the third valve is closed, the fourth valve is opened, the electric regulating valve is opened and the second valve is closed. The working fluid in the downcomer passes through the pipeline before the pump, the internal circulation pump, the pipeline after the pump, the warm pump connection pipeline, and the economizer recirculation pipeline to form a bypass, and then forms a closed natural circulation loop with the boiler evaporation system, so that the pump body of the internal circulation pump is kept hot and the temperature is consistent with the working fluid when in standby mode.

2. The internal circulation pump warm-up system of the natural circulation boiler as described in claim 1, characterized in that, A pump inlet medium temperature sensor is installed on the pipeline before the pump, and the pump inlet medium temperature sensor is located downstream of the first valve. A downstream medium temperature sensor is installed on the downstream pipeline, and the downstream medium temperature sensor is located between the outlet of the internal circulation pump and the inlet of the warm-up connection pipeline.

3. The internal circulation pump warm-up system of the natural circulation boiler as described in claim 2, characterized in that, The flow meter and the electric regulating valve are respectively connected to the controller via electrical signals; Specifically, when the flow meter detects a flow rate > 10t / h, the controller controls the electric regulating valve to reduce its opening. When the temperature difference between the pump inlet temperature detected by the pump inlet temperature sensor and the pump outlet temperature detected by the pump outlet temperature sensor exceeds the preset temperature difference, the controller controls the electric regulating valve to open wider.

4. The internal circulation pump warm-up system of the natural circulation boiler as described in claim 3, characterized in that, Also includes: The boiler drum has its water outlet end connected to a downcomer, which in turn connects to the pipeline before the pump via a welded pipe seat. A wall temperature sensor is installed on the lower wall of the boiler drum. When the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor and the boiler drum wall temperature detected by the wall temperature sensor is less than or equal to the preset temperature difference, and the temperature difference between the pump inlet temperature detected by the pump inlet medium temperature sensor and the pump outlet temperature detected by the pump outlet medium temperature sensor is less than or equal to the preset temperature difference, the pump warm-up system is deemed to be operating effectively.

5. The internal circulation pump warm-up system of the natural circulation boiler as described in claim 4, characterized in that, Also includes: The lower header has its inlet end connected to the downcomer via a pipeline, and its outlet end connected to the boiler drum via an ascender, forming an evaporation circuit.

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