An integrated hydraulic turbine boiler water circulation pump and start-stop method

Abstract

The present invention discloses an integrated hydraulic turbine boiler water circulation pump and a start-up and shutdown method. The boiler water circulation pump is divided into a hydraulic turbine unit, a first water chamber unit, a boiler water pump unit, a second water chamber unit, and an axial force balance unit according to their functions. By designing a unique main and secondary channel water inlet structure, the problem of high-temperature and high-pressure boiler water sealing in conventional shaft seal pumps is solved, and the working environment of each seal is greatly improved, the service life is extended, and the inner core can be pulled out and replaced as a whole, which is convenient for maintenance. On this basis, a step-by-step preheating and rapid shutdown method is also designed, which not only improves the reliability and service life under frequent start-up and shutdown, but also deeply integrates its start-up and shutdown process into the deep peak regulation process of the supercritical boiler, so that the feed water flow of the supercritical boiler can be quickly restored after the hydraulic turbine boiler water circulation pump exits due to an accident, and no water outage and shutdown failure occurs. At the same time, it can replace the recirculation function of the pneumatic feed water pump group and improve the reliability of the water supply system.

Description

Technical Field

[0001] The present invention belongs to the field of boiler water circulation pumps and relates to a boiler water circulation pump applied to a supercritical once-through boiler, and in particular to an integrated hydraulic turbine boiler water circulation pump and a start-stop method. Background Art

[0002] Currently, electric shielded pumps are commonly used for boiler water circulation pumps, primarily used during the startup process in supercritical boilers. These pumps utilize a sealless design with a high pressure rating, effectively preventing leakage of high-temperature boiler water. Their high reliability in continuous operation has led to widespread adoption. However, their bearings are typically self-lubricated with the conveying liquid. Pressure fluctuations during startup and shutdown can cause flash vaporization of saturated water, rupturing the liquid film and forming a vapor-liquid two-phase flow. This can lead to bearing lubrication failure and reduced reliability under frequent startup and shutdown conditions. Because electric boiler water circulation pumps lack a seal and are enclosed within a sealed housing, they are difficult to inspect and maintain, typically requiring factory repairs and lengthy maintenance cycles. When used in the boiler water recirculation scenarios of deep peak-shaving wet conditions in supercritical boilers, the pumps require frequent startups and shutdowns, maintaining moderate operating pressures, and minimizing their advantages of high pressure rating, strong sealing, and high reliability during continuous operation. In addition, when the electric boiler water circulation pump is used in the boiler water circulation scenario of the supercritical DC boiler deep peak-shaving wet working conditions, the water supply system includes two power sources: the electric boiler water pump and the pneumatic feed water pump group. When the electric boiler water pump stops operating due to an accident, the water supply system will trigger the water cut-off protection due to insufficient power, causing the water supply flow entering the boiler to drop rapidly. The above defects make it difficult to use in this scenario.

[0003] A hydraulic turbine-driven boiler water circulation pump utilizes the technology disclosed in the patent "A Direct Current Boiler Water Feed Pump System and Control Method for Coupled Steam-Driven Feedwater Pumps and Hydraulic Turbine Boiler Water Circulation Pumps" (CN119468191A), addressing the reliability issues associated with multiple power sources connected in parallel in feedwater systems. To address the reliability issues and maintenance difficulties associated with frequent start-stop operations of electric boiler water circulation pumps, the present invention discloses an integrated hydraulic turbine boiler water circulation pump and start-stop method. Designed based on the operating characteristics of boiler water circulation pumps for supercritical direct current furnaces, the pump incorporates a unique water inlet structure and start-stop method based on a conventional shaft-sealed counter-rotating hydraulic turbine. This achieves self-sealing of the high-temperature, high-pressure boiler water within the pump, achieving sealing effectiveness comparable to that of sealless electric canned motor pumps. This design also leverages the advantages of conventional counter-rotating pumps, such as external bearings and high reliability during frequent starts and stops. The pump core packing can be replaced on-site, facilitating easy maintenance and repair. Summary of the Invention

[0004] The integrated hydraulic turbine boiler water circulation pump and start-up and shutdown method disclosed in the present invention are designed based on the operating characteristics of the boiler water circulation pump of a supercritical direct current furnace. On the basis of a conventional shaft-sealed reverse pump hydraulic turbine, a unique water inlet structure and start-up and shutdown method are designed to achieve self-sealing of the high-temperature and high-pressure boiler water in the boiler water circulation pump. The sealing effect is comparable to that of an electric shielded pump without a shaft seal. At the same time, the design also takes into account the advantages of high reliability of the frequent start-up and shutdown of conventional reverse pumps. The pump core pack can be replaced on site as a whole, and the inspection and maintenance are convenient, overcoming the shortcomings of the electric shielded pump. The specific design boundaries are: (1) The power water source of the hydraulic turbine (the water from the outlet of the steam-driven feed water pump) and the boiler water are both boiler feed water, with exactly the same water quality and can be mixed with each other. (2) Since the outlet of the steam-driven feedwater pump is located at the upstream of the boiler feedwater system and has the highest pressure, the pressure of the hydraulic turbine's power water source (the feedwater at the outlet of the steam-driven feedwater pump) is higher than the inlet pressure of the boiler water circulation pump. Depending on the location of the boiler water circulation, the pressure difference between the two in the deep peak regulation range is 0.5-2 MPa. (3) In the load range where the boiler water circulation pump needs to be put into operation, the temperature of the hydraulic turbine's power water source (the feedwater at the outlet of the steam-driven feedwater pump) is lower than that of the high-temperature boiler water circulation (300-350°C), generally below 150°C.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses an integrated hydraulic turbine furnace water circulation pump structure, which is mainly as follows:

[0007] The structure of the integrated hydraulic turbine boiler water circulation pump adopts the core package structure widely used in the field of boiler feed water pumps. The core package is placed in the pump outer shell as an independent part. The outer shell has a radially split structure and consists of an outer cylinder and an end cover. Mechanical shaft seals are used at both ends. The core package can be pulled out as a whole, which is convenient for inspection and maintenance.

[0008] The core assembly is composed of a rotor and multiple sections of inner casing with different functions. The inner casing is completely axially split for easy installation and maintenance. It is functionally divided into a hydraulic turbine unit, a first water chamber unit, a boiler water pump unit, a second water chamber unit, and an axial force balancing unit. The hydraulic turbine unit provides power for the hydraulic turbine's boiler water circulation pump. The first and second water chambers serve as the hydraulic turbine's auxiliary water inlet and preheating channels before startup, isolating the high-temperature, high-pressure boiler water from the boiler water pump unit and providing low-temperature coolant for its sealing device. The boiler water pump unit pressurizes the circulating boiler water, and the axial force balancing unit balances the axial forces generated by the hydraulic turbine unit and the boiler water pump unit.

[0009] The hydraulic turbine unit adopts a layout similar to that of a conventional multi-stage centrifugal counter-rotating pump, and consists of a hydraulic turbine inner volute and a multi-stage hydraulic turbine impeller. The hydraulic turbine inner volute adopts a center-split structure, and the hydraulic turbine impeller is installed on the rotor of the unit. The interlayer between the hydraulic turbine inner volute and the outer shell is connected to the main inlet of the hydraulic turbine. The main inlet of the hydraulic turbine is connected to the high-pressure water supply pipeline from the outlet of the steam-driven water supply pump group through the hydraulic turbine water inlet main regulating valve, and the hydraulic turbine outlet is connected to the low-pressure water supply pipeline to the unit deaerator through the hydraulic turbine outlet regulating valve.

[0010] The hydraulic turbine water inlet main regulating valve has a quick closing function, which can achieve rapid shutdown in a fault state.

[0011] The flow capacity of the hydraulic turbine is designed according to the minimum head of the hydraulic turbine during the operation of the unit and the power required by the boiler water pump; this design can ensure that the hydraulic turbine has sufficient power during actual operation, and the main regulating valve of the hydraulic turbine water inlet is always in a throttling state. Its speed and output power can be controlled by adjusting the opening of the main regulating valve of the hydraulic turbine.

[0012] The inner shells of the first and second water chamber units are cylindrical structures. Ribs can be added internally to enhance axial rigidity, and are symmetrically arranged on either side of the boiler water pump unit. The inner shells comprise a first and second inner shells, with a clearance for expansion between them. The inner shells are sealed with high-temperature elastic material near the boiler water pump unit to prevent the influx of high-temperature boiler water from the pump unit. The first and second water chamber inlets are connected to the high-pressure water supply pipes from the outlet of the steam-driven feedwater pump unit via auxiliary water chamber inlet regulating valves.

[0013] The gap between the inner casing and the rotor of the first and second water chamber units adjacent to the boiler water pump unit is sealed with a dynamic pressure floating seal ring. The other side of the dynamic pressure floating seal ring is the boiler water pump unit interlayer. Due to the operating characteristics of the hydraulic turbine boiler water circulation pump, the pressure within the two water chambers is always higher than the pressure at the boiler water pump unit inlet and the interlayer connected to it. Even if the dynamic pressure floating seal ring fails, boiler water leakage will not occur, achieving a self-sealing function for high-temperature boiler water. The cooler feedwater in the water chambers provides cooling for the dynamic pressure floating seal rings.

[0014] The first and second water chamber units serve as the secondary water inlet channels of the hydraulic turbine. The secondary water inlet channels are constructed as follows: high-pressure feedwater entering the first water chamber unit flows into the hydraulic turbine unit interlayer through the gap between the inner casing and the rotor adjacent to the hydraulic turbine unit. High-pressure feedwater entering the second water chamber unit flows into the axial force balancing unit front chamber through the gap between the inner casing and the rotor adjacent to the axial force balancing unit, and then flows into the hydraulic turbine unit interlayer through the axial force balancing unit front chamber connecting pipe. The high-pressure feedwater entering the hydraulic turbine interlayer ultimately flows to the hydraulic turbine main inlet. The gap size or throttling sleeve in the secondary water inlet channel is determined according to the required flow rate of the first and second water chamber units.

[0015] The flow rate flowing through the first water chamber unit and the second water chamber unit is determined according to the residual flow rate required by the inlet high-pressure water feed pipe of the hydraulic turbine unit when the hydraulic turbine water inlet main regulating valve is quickly closed without causing a destructive water hammer effect; this can be achieved by adjusting the gap size between the water chamber inner shell and the rotor on the secondary water inlet channel or the throttling capacity of the throttling kit installed at the gap.

[0016] The boiler water pump unit utilizes a structure similar to a conventional single-stage centrifugal pump, consisting of a single-stage boiler water pump impeller and an inner volute. The impeller utilizes a double-suction structure, and the interlayer between the inner volute and the outer casing communicates with the boiler water pump inlet. The interlayer at the boiler water pump outlet is sealed with a high-pressure metal bellows. The boiler water pump unit includes a boiler water pump inlet and a boiler water pump outlet. The boiler water pump inlet is connected to the boiler water pipeline from the boiler separator water storage tank via a boiler water pump inlet regulating valve. A boiler water pump outlet regulating valve is installed on the connecting pipe of the boiler water pump outlet, which is connected to the boiler water pipeline leading to the boiler economizer inlet via the boiler water pump outlet regulating valve. A boiler water pump outlet drain regulating valve is installed in the pipeline preceding the boiler water pump outlet regulating valve, connecting to the boiler drain expansion tank.

[0017] The axial force balancing unit utilizes a thrust balancing structure similar to that of a conventional multi-stage centrifugal pump, comprising an axial force balancing inner housing, an axial force balancing unit front chamber, an axial force balancing unit rear chamber, an axial force balancing plate, and an axial force balancing disc. The axial force balancing inner housing can be integrally designed with the second water chamber inner housing, with the axial force balancing plate mounted on the axial force balancing inner housing, and the axial force balancing disc mounted on the corresponding position of the rotor. The axial force balancing unit front chamber is enclosed by the axial force balancing plate and the second water chamber inner housing, and is connected to the hydraulic turbine unit interlayer via an axial force balancing unit front chamber connecting pipe. The axial force balancing unit rear chamber is enclosed by the axial force balancing disc and the axial force balancing inner housing, and is connected to the hydraulic turbine outlet via an axial force balancing unit rear chamber connecting pipe. A portion of the high-pressure feedwater from the second water chamber is depressurized through the gap between the axial force balancing disc and the axial force balancing plate, ultimately flowing to the hydraulic turbine outlet and generating the desired axial thrust on the axial force balancing disc. The gap between the axial force balancing disc and the axial force balancing plate can be dynamically adjusted according to the desired axial thrust.

[0018] The method for starting the integrated hydraulic turbine boiler water circulation pump is as follows:

[0019] The status of each valve before the hydraulic turbine boiler water circulation pump is started is: the hydraulic turbine water inlet main regulating valve is closed, the hydraulic turbine outlet regulating valve is open, the water chamber water inlet auxiliary regulating valve is closed, the boiler water pump inlet regulating valve and the boiler water pump outlet regulating valve are closed, and the boiler water pump outlet drain regulating valve is open.

[0020] In the first step, when the supercritical boiler load begins to peak deeply, and the feed water flow rate drops to near the minimum flow rate of the steam-driven feed water pump group, the water chamber inlet auxiliary regulating valve is opened to a certain opening, and the pressure difference of the chambers on both sides of the dynamic pressure floating seal ring is monitored to ensure that it does not exceed the design value. The low-temperature high-pressure feed water from the outlet of the steam-driven feed water pump is used to initially preheat the various components of the hydraulic turbine boiler water circulation pump.

[0021] In the second step, after the initial preheating is completed, when the supercritical boiler load is further reduced, the water chamber inlet auxiliary regulating valve is gradually fully opened, and the boiler water pump inlet regulating valve is opened accordingly to control the pressure difference of the chamber on both sides of the dynamic pressure floating sealing ring not to exceed the design value, and use high-pressure and high-temperature boiler water to further preheat the boiler water pump unit to a state that allows startup.

[0022] In the third step, at the end of the preheating stage, when the supercritical boiler load is further reduced and the boiler water pump needs to be put into operation, the hydraulic turbine water inlet main regulating valve is opened to quickly increase the hydraulic turbine boiler water pump speed. After entering the high-efficiency stable range, the boiler water pump flow is automatically controlled. During this process, the boiler water pump outlet regulating valve is gradually fully opened, and the boiler water pump outlet drain regulating valve is gradually fully closed.

[0023] The normal shutdown method of the integrated hydraulic turbine boiler water circulation pump is as follows: when the supercritical boiler load increases and exits deep peak regulation, the hydraulic turbine water inlet main regulating valve can be gradually closed, the hydraulic turbine boiler water pump speed can be reduced, and then the boiler water pump inlet regulating valve and the boiler water pump outlet regulating valve can be slowly closed; the boiler water pump outlet drain regulating valve can be gradually opened, and the water chamber water inlet auxiliary regulating valve is closed accordingly to control the pressure difference of the chamber on both sides of the dynamic pressure floating sealing ring to not exceed the design value.

[0024] The described method for shutting down the integrated hydraulic turbine boiler water circulation pump in the event of a fault is as follows: while the supercritical boiler is still in deep peak regulation operation, the main hydraulic turbine water inlet regulating valve is quickly closed, the water chamber water inlet auxiliary regulating valve remains open, and the subsequent shutdown steps are the same as for a normal shutdown. This design can quickly re-route the high-pressure feed water passing through the hydraulic turbine back into the main feed water pipeline, rapidly restoring the feed water flow entering the supercritical boiler without causing a water outage or shutdown. When the supercritical boiler trips, the main hydraulic turbine water inlet regulating valve is quickly closed, the boiler water pump outlet drain regulating valve is quickly opened to prevent the pressure differential on both sides of the dynamic pressure floating seal ring from exceeding the design value, the boiler water pump inlet regulating valve and the boiler water pump outlet regulating valve are then closed, and finally, the water chamber water inlet auxiliary regulating valve is gradually closed.

[0025] During startup, the high-pressure feedwater flow rate returning to the deaerator through the hydraulic turbine boiler water circulating pump gradually increases as the supercritical boiler load decreases. This feature, consistent with the function of the pneumatic feedwater pump recirculation valve, eliminates the need for the pneumatic feedwater pump recirculation valve during startup, reducing disturbances in the feedwater system and avoiding internal leakage in the pneumatic feedwater pump recirculation valve. Furthermore, this step-by-step preheating method reduces thermal stress during the preheating process and the probability of component jamming due to uneven expansion, thereby improving the reliability and lifespan of the hydraulic turbine boiler water circulating pump during frequent startups and shutdowns.

[0026] The integrated hydraulic turbine boiler water circulation pump and start-up and shutdown method disclosed in the present invention have the following innovations:

[0027] (1) A unique main and auxiliary channel water inlet structure is designed, which not only solves the problem of high temperature and high pressure boiler water sealing in conventional shaft seal pumps, but also greatly improves the working environment of each seal and greatly extends its service life. At the same time, the inner core can be pulled out and replaced as a whole, which is convenient for maintenance.

[0028] (2) A step-by-step preheating and rapid shutdown method was designed. This not only improves reliability and service life under frequent start-up and shutdown conditions, but also deeply integrates the start-up and shutdown process into the deep peak regulation process of the supercritical boiler. This allows the feed water flow of the supercritical boiler to be quickly restored after the hydraulic turbine boiler water circulation pump fails, without causing water outage and shutdown failures. At the same time, it can replace the recirculation function of the steam-driven feed water pump group, improving the reliability of the water supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the integrated hydraulic turbine furnace water circulation pump structure of the present invention;

[0030] In the picture:

[0031] 1. Rotor; 2. Mechanical seal in front of outer casing; 3. Inner volute of hydraulic turbine; 4. Impeller of hydraulic turbine; 5. Inner casing of first water chamber; 6. Main inlet of hydraulic turbine; 7. Main regulating valve for hydraulic turbine water inlet; 8. Auxiliary regulating valve for water chamber water inlet; 9. Inlet of first water chamber; 10. Inner volute of boiler water pump; 11. High-pressure metal bellows; 12. Outlet of boiler water pump; 13. Outlet regulating valve of boiler water pump; 14. Outlet drain regulating valve of boiler water pump; 15. Impeller of boiler water pump; 16. Inlet of second water chamber; 17. Inner casing of second water chamber; 18. Axial force Front chamber of the balancing unit; 19. Axial force balancing plate; 20. Axial force balancing disc; 21. Mechanical shaft seal at the rear of the outer shell; 22. Rear chamber of the axial force balancing unit; 23. Connecting pipe to the rear chamber of the axial force balancing unit; 24. Connecting pipe to the front chamber of the axial force balancing unit; 25. Dynamic pressure floating seal ring of the second water chamber; 26. Boiler water pump inlet; 27. Dynamic pressure floating seal ring of the first water chamber; 28. Boiler water pump inlet regulating valve; 29. ​​Hydraulic turbine unit interlayer; 30. Outer shell; 31. Hydraulic turbine outlet; 32. Hydraulic turbine outlet regulating valve. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, the structure of the integrated hydraulic turbine boiler water circulation pump described in the present invention adopts a core package structure widely used in boiler feedwater pumps. The core package is placed as an independent part in the outer shell 30 and can be withdrawn as a whole. The two ends of the pump shell are sealed with the outer shell front mechanical shaft seal 2 and the outer shell rear mechanical shaft seal 21, respectively. Because it is only subjected to the pressure and temperature of the hydraulic turbine outlet, the operating environment is relatively good, and there are no special requirements for mechanical seal performance, so mature products can be selected. The outer shell 30 generally adopts a radially split structure, consisting of an outer cylinder and end covers. The overall compressive strength is high, reaching approximately 40MPa, which fully meets the operating pressure requirements of the hydraulic turbine boiler water circulation pump.

[0034] The core package is composed of a rotor 1 and multiple inner shells. The inner shells are axially split to facilitate installation and maintenance. They are divided into hydraulic turbine unit, first water chamber unit, boiler water pump unit, second water chamber unit and axial force balance unit according to their functions.

[0035] The hydraulic turbine unit utilizes a layout similar to that of a conventional multi-stage centrifugal counter-rotating pump, consisting of a hydraulic turbine inner volute 3 and a hydraulic turbine impeller assembly 4. Depending on the pressure differential, three to five impeller stages can be configured. The hydraulic turbine unit interlayer 29 between the hydraulic turbine inner volute 3 and the outer casing 30 is connected to the hydraulic turbine main inlet 6. This inlet is connected to the high-pressure feedwater pipeline from the steam-driven feedwater pump assembly via a hydraulic turbine inlet main regulating valve 7. The hydraulic turbine outlet 31 is connected to the low-pressure feedwater pipeline to the unit's deaerator via a hydraulic turbine outlet regulating valve 32. The hydraulic turbine inner volute 3 is subject only to compressive stress, so the center face can be sealed with only very small bolts.

[0036] The first and second water chamber inner shells 5, 17 are cylindrical structures, with internal reinforcement ribs for enhanced axial rigidity. They are symmetrically arranged on either side of the boiler water pump unit. The first and second water chamber inlets 9, 16 are connected to the high-pressure water supply pipe from the steam-driven feedwater pump unit via the water chamber inlet auxiliary regulating valve 8. A sufficient expansion gap is provided between the first and second water chamber inner shells 5, 17 and the outer shell 30. The inner shell is sealed with a high-temperature elastic material near the boiler water pump unit to prevent the inflow of high-temperature boiler water from the boiler water pump unit.

[0037] The gap between the first water chamber inner shell 5 and the rotor 1 on the side of the first water chamber unit adjacent to the boiler water pump unit is sealed with a first water chamber dynamic pressure floating seal ring 27. The gap between the first water chamber inner shell 5 and the rotor 1 on the other side communicates directly with the hydraulic turbine unit interlayer 29, either directly or through a throttle kit, without a seal. The gap between the second water chamber inner shell 17 and the rotor 1 on the side of the second water chamber unit adjacent to the boiler water pump unit is sealed with a second water chamber dynamic pressure floating seal ring 25. The gap between the second water chamber inner shell 17 and the rotor 1 on the other side communicates directly with the axial force balancing unit front chamber 18, either directly or through a throttle kit, without a seal. The first and second water chamber inner shells 5 and 17 serve as the secondary water inlet passages for the hydraulic turbine. The incoming high-pressure feed water ultimately flows to the main inlet of the hydraulic turbine. The size of the gap in the secondary water inlet passages or the throttling capacity of the throttle kit is determined by the required flow rates of the first and second water chamber units.

[0038] The boiler water pump unit utilizes a structure similar to a conventional single-stage centrifugal pump, consisting of a single-stage boiler water pump impeller 15 and an inner boiler water pump volute 10. The impeller 15 utilizes a double-suction structure with self-balancing axial forces. The interlayer between the inner boiler water pump volute 10 and the outer shell 30 communicates with the boiler water pump inlet 26, and the interlayer at the outlet is sealed with a high-pressure metal bellows 11. The boiler water pump inlet 26 is connected to the boiler water pipeline from the boiler separator water storage tank via a boiler water pump inlet regulating valve 28. The boiler water pump outlet 12 is connected to the boiler water pipeline to the boiler economizer inlet via a boiler water pump outlet regulating valve 13. A boiler water pump outlet drain regulating valve 14 is installed in the pipeline upstream of the boiler water pump outlet regulating valve 13, connecting to the boiler drain expansion tank.

[0039] The axial force balancing unit utilizes a thrust balancing structure similar to that of a conventional multi-stage centrifugal pump, comprising an axial force balancing inner housing, an axial force balancing unit front chamber 18, an axial force balancing unit rear chamber 22, an axial force balancing plate 19, and an axial force balancing disc 20. The axial force balancing inner housing can be designed as an integral structure with the second water chamber inner housing 17, with the axial force balancing plate 19 mounted on the second water chamber inner housing 17, and the axial force balancing disc 20 mounted at a corresponding position on the rotor 1. The axial force balancing unit front chamber 18 is enclosed by the axial force balancing plate 19 and the second water chamber inner housing 17, and is connected to the hydraulic turbine unit interlayer 29 via an axial force balancing unit front chamber connecting pipe 24. The axial force balancing unit rear chamber 22 is enclosed by the axial force balancing disc 20 and the axial force balancing inner housing, and is connected to the hydraulic turbine outlet 31 via an axial force balancing unit rear chamber connecting pipe 23. A portion of the high-pressure feedwater from the second water chamber unit is depressurized through the gap between the axial force balancing plate 19 and the axial force balancing disc 20, ultimately flowing to the hydraulic turbine outlet 31 and generating the required axial thrust on the axial force balancing disc 20. The gap between the axial force balancing plate 19 and the axial force balancing disc 20 can be dynamically adjusted according to the required axial thrust. Because the boiler water pump unit utilizes a single-stage, double-suction impeller structure, the axial force is self-balancing, and the axial force balancing unit is primarily responsible for balancing the thrust generated by the hydraulic turbine unit.

[0040] The hydraulic turbine unit provides power for the hydraulic turbine boiler water circulation pump. The first and second water chamber units serve as auxiliary water inlet channels for the hydraulic turbine and preheating channels before startup. They are responsible for isolating the high-temperature, high-pressure boiler water from the sealed boiler water pump unit and providing low-temperature coolant for its sealing device. The boiler water pump unit boosts the circulating boiler water pressure, and the axial force balancing unit balances the axial forces generated by the hydraulic turbine unit and the boiler water pump unit.

[0041] The flow capacity of the hydraulic turbine is designed based on the minimum head of the hydraulic turbine during unit operation and the power required by the boiler water pump unit. This design ensures sufficient power for the hydraulic turbine. During actual operation, the hydraulic turbine water inlet main regulating valve 7 is always in a throttling state. The hydraulic turbine speed and actual output power can be controlled by the opening of the hydraulic turbine water inlet main regulating valve 7. The hydraulic turbine water inlet main regulating valve 7 has a fast closing function, which can achieve rapid shutdown in the event of a fault.

[0042] Due to the operating characteristics of the hydraulic turbine boiler water circulation pump, the pressure within the first and second water chamber inner shells 5 and 17 is consistently higher than the pressure at the boiler water pump inlet 26 and the interlayer connected thereto. Even if the first or second water chamber dynamic pressure floating seal rings 27 and 25 fail, boiler water will not leak out. Furthermore, the cooler feedwater within the first and second water chamber inner shells 5 and 17 provides cooling for the dynamic pressure floating seal rings. Because the dynamic pressure floating seal rings utilize non-contact sealing technology, they utilize the kinetic energy of rotation to draw low-temperature feedwater into the sealing surface, forming a liquid film and cooling the sealing surface. The cooling flow rate can be determined by designing the sealing surface flow path, resulting in a long service life. Furthermore, the static leakage rate of the dynamic pressure floating seal rings is much higher than that during high-speed operation. This characteristic can be exploited to provide the feedwater required for preheating the boiler water pump unit from the water chambers during the initial preheating phase of the pump body.

[0043] The required flow rates of the first and second water chamber units are determined by the residual flow rate required to prevent destructive water hammer in the turbine's main inlet high-pressure water feed pipeline after the turbine's main water inlet regulating valve 7 is rapidly closed. The design principle is that the turbine's auxiliary water inlet channel remains fully open. The greater the flow rate, the smaller the change in pipeline flow velocity before and after the turbine's main water inlet regulating valve 7 is rapidly closed, significantly reducing the water hammer effect caused by sudden changes in flow velocity. Furthermore, to further reduce the water hammer effect, energy-absorbing devices such as accumulators can be installed in the pipeline.

[0044] The design of the boiler water pump unit interlayer connected to the inlet is primarily driven by the low head of the boiler water pump and the small pressure differential between the inner and outer casings. The inner casing is installed in a horizontal axial split, and the bolts on the split surface are subjected to low stress. Existing technology fully meets these requirements. This design also eliminates the need for shaft seals at the water inlets on both sides of the boiler water pump unit, further improving the pump's reliability.

[0045] The method for starting the integrated hydraulic turbine boiler water circulation pump is as follows:

[0046] The status of each valve before the hydraulic turbine boiler water circulation pump is started is: the hydraulic turbine water inlet main regulating valve 7 is closed, the hydraulic turbine outlet regulating valve 32 is open, the water chamber water inlet auxiliary regulating valve 8 is closed, the boiler water pump inlet regulating valve 28 and the boiler water pump outlet regulating valve 13 are closed, and the boiler water pump outlet drain regulating valve 14 is open.

[0047] In the first step, when the supercritical boiler load begins to deeply peak, and the feed water flow rate is reduced to near the minimum flow rate of the steam-driven feed water pump group, the water chamber water inlet auxiliary regulating valve 8 is opened to a certain opening, and the pressure difference of the chambers on both sides of the dynamic pressure floating seal ring is monitored to ensure that it does not exceed the design value. The low-temperature high-pressure feed water from the outlet of the steam-driven feed water pump is used to initially preheat the various components of the hydraulic turbine boiler water circulation pump.

[0048] In the second step, after the initial preheating is completed, when the supercritical boiler load is further reduced, the water chamber inlet auxiliary regulating valve 8 is gradually fully opened, and the boiler water pump inlet regulating valve 28 is opened accordingly to control the pressure difference of the chamber on both sides of the dynamic pressure floating sealing ring to not exceed the design value, and use high-pressure and high-temperature boiler water to further preheat the boiler water pump unit to a state that allows startup.

[0049] In the third step, after the preheating phase ends and the supercritical boiler load decreases further, requiring the boiler water pump to be put into operation, the hydraulic turbine water inlet main regulating valve 7 is opened to rapidly increase the hydraulic turbine boiler water pump speed. Once the speed enters the high-efficiency and stable range, the boiler water pump flow rate is automatically controlled. During this process, the boiler water pump outlet regulating valve 13 is gradually fully opened, and the boiler water pump outlet drain regulating valve 14 is gradually fully closed.

[0050] During startup, the high-pressure feedwater flow rate returning to the deaerator through the hydraulic turbine boiler water circulating pump gradually increases as the supercritical boiler load decreases. This feature, consistent with the function of the pneumatic feedwater pump recirculation valve, eliminates the need for the pneumatic feedwater pump recirculation valve during startup, minimizing disturbances to the feedwater system. Furthermore, this step-by-step preheating method reduces thermal stress during the preheating process and the likelihood of component seizures due to uneven expansion, thereby improving the reliability and lifespan of the hydraulic turbine boiler water circulating pump during frequent startups and shutdowns.

[0051] The normal shutdown method of the integrated hydraulic turbine boiler water circulation pump is as follows: when the supercritical boiler load increases and exits deep peak regulation, the hydraulic turbine water inlet main regulating valve 7 can be gradually closed to reduce the speed of the hydraulic turbine boiler water pump, and then the boiler water pump inlet regulating valve 28 and the boiler water pump outlet regulating valve 13 are slowly closed; the boiler water pump outlet drain regulating valve 14 is gradually opened, and the water chamber water inlet auxiliary regulating valve 8 is closed accordingly to control the pressure difference of the chamber on both sides of the dynamic pressure floating sealing ring to not exceed the design value.

[0052] The described method for shutting down the integrated hydraulic turbine boiler water circulation pump in the event of a fault is as follows: when the supercritical boiler is still in deep peak regulation operation, the hydraulic turbine water inlet main regulating valve 7 is quickly closed, and the water chamber water inlet auxiliary regulating valve 8 remains open. The subsequent shutdown steps are the same as normal shutdown. This design can quickly re-introduce the high-pressure feed water passing through the hydraulic turbine into the main feed water pipeline, so that the feed water flow entering the supercritical boiler is quickly restored and the water outage shutdown failure does not occur. When the supercritical boiler trips, the hydraulic turbine water inlet main regulating valve 7 is quickly closed, and the boiler water pump outlet drain regulating valve 14 is quickly opened to prevent the pressure difference on both sides of the dynamic pressure floating seal ring from exceeding the design value. Then, the boiler water pump inlet regulating valve 28 and the boiler water pump outlet regulating valve 13 are closed, and finally, the water chamber water inlet auxiliary regulating valve 8 is gradually closed.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An integrated hydraulic turbine boiler water circulation pump, characterized in that: The invention comprises an outer shell (30) and a core package arranged inside the outer shell (30), wherein the outer shell (30) comprises an outer cylinder and an end cover, and mechanical shaft seals are adopted at both ends. The core package is composed of a rotor (1) and a plurality of inner shells with different functions, and is divided into a hydraulic turbine unit, a first water chamber unit, a boiler water pump unit, a second water chamber unit and an axial force balancing unit according to the functions. The hydraulic turbine unit is used to provide power for the hydraulic turbine boiler water circulation pump. The first water chamber unit and the second water chamber unit are used as auxiliary water inlet channels and preheating channels before starting of the hydraulic turbine, and are responsible for isolating the high-temperature and high-pressure boiler water of the boiler water pump unit and providing low-temperature coolant for its sealing device. The boiler water pump unit is used to pressurize the circulating boiler water. The axial force balancing unit is used to balance the axial force generated by the hydraulic turbine unit and the boiler water pump unit. The boiler water pump unit adopts a single-stage centrifugal pump structure, consisting of a first-stage boiler water pump impeller (15) and a boiler water pump inner volute (10), wherein the boiler water pump impeller (15) adopts a double-suction structure; the interlayer between the boiler water pump inner volute (10) and the outer shell (30) is connected to the boiler water pump inlet (26), and the interlayer in the boiler water pump outlet (12) area is sealed with a high-pressure metal bellows (11); the boiler water pump unit includes a boiler water pump inlet (26) and a boiler water pump outlet (12); the boiler water pump The inlet (26) is connected to the boiler water pipeline from the boiler separator water storage tank through the boiler water pump inlet regulating valve (28), and a boiler water pump outlet regulating valve (13) is provided on the connecting pipeline of the boiler water pump outlet (12). The boiler water pump outlet (12) is connected to the boiler water pipeline to the boiler economizer inlet through the boiler water pump outlet regulating valve (13); a boiler water pump outlet drain regulating valve (14) is provided in the pipeline before the boiler water pump outlet regulating valve (13) and connected to the boiler drain expansion tank; The axial force balancing unit adopts the thrust balancing structure of a multi-stage centrifugal pump, including an axial force balancing inner shell, an axial force balancing unit front chamber (18), an axial force balancing unit rear chamber (22), an axial force balancing plate (19) and an axial force balancing disc (20); the axial force balancing inner shell and the second water chamber inner shell (17) are designed as a whole, the axial force balancing plate (19) is installed on the axial force balancing inner shell, and the axial force balancing disc (20) is installed on the corresponding position of the rotor (1); the axial force balancing unit front chamber (18) is enclosed by the axial force balancing plate (19) and the second water chamber inner shell (17), and is connected to the rotor (1) through the axial force balancing unit front chamber. The through pipe (24) is connected to the hydraulic turbine unit interlayer (29); the rear chamber (22) of the axial force balancing unit is formed by the axial force balancing disc (20) and the axial force balancing inner shell, and is connected to the hydraulic turbine outlet (31) through the axial force balancing unit rear chamber connecting pipe (23); part of the high-pressure feed water from the second water chamber unit is reduced in pressure through the gap between the axial force balancing disc (20) and the axial force balancing plate (19), and finally flows to the hydraulic turbine outlet (31), and generates the required axial thrust on the axial force balancing disc (20), and the gap between the axial force balancing disc (20) and the axial force balancing plate (19) can be dynamically changed according to the required axial thrust; The first water chamber unit and the second water chamber unit serve as auxiliary water inlet channels of the hydraulic turbine unit. The auxiliary water inlet channels are constructed as follows: the high-pressure feed water entering the first water chamber unit flows into the hydraulic turbine unit interlayer through the gap between the inner shell and the rotor adjacent to the hydraulic turbine unit side; the high-pressure feed water entering the second water chamber unit flows into the axial force balancing unit front chamber (18) through the gap between the inner shell and the rotor adjacent to the axial force balancing unit side, and then flows into the hydraulic turbine unit interlayer (29) through the axial force balancing unit front chamber connecting pipe (24); the high-pressure feed water flowing into the hydraulic turbine unit interlayer (29) eventually flows to the hydraulic turbine main inlet (6); the flow rate of the auxiliary water inlet channel is determined according to the residual flow rate required for the hydraulic turbine unit inlet high-pressure feed water pipeline to be quickly closed at the hydraulic turbine water inlet main regulating valve (7) without causing a destructive water hammer effect; this can be achieved by adjusting the gap between the inner shell and the rotor on the auxiliary water inlet channel or the throttling capacity of the throttling kit installed at the gap.

2. The integrated hydraulic turbine furnace water circulation pump according to claim 1, characterized in that: The hydraulic turbine unit is composed of a hydraulic turbine inner volute (3) and a multi-stage hydraulic turbine impeller (4). The hydraulic turbine inner volute (3) adopts a center-split structure. The hydraulic turbine impeller (4) is installed on the rotor (1) of the hydraulic turbine unit. The interlayer between the hydraulic turbine inner volute (3) and the outer shell (30) is connected to the hydraulic turbine main inlet (6). The hydraulic turbine main inlet (6) is connected to the high-pressure water supply pipeline from the outlet of the steam-driven water supply pump group through the hydraulic turbine water inlet main regulating valve (7). The hydraulic turbine outlet (31) is connected to the low-pressure water supply pipeline to the unit deaerator through the hydraulic turbine outlet regulating valve (32); the hydraulic turbine water inlet main regulating valve (7) has a fast closing function.

3. The integrated hydraulic turbine furnace water circulation pump according to claim 1, characterized in that: The inner shells of the first water chamber unit and the second water chamber unit are cylindrical structures, with reinforcing ribs added inside to enhance the axial rigidity of the inner shells. The first water chamber unit and the second water chamber unit are symmetrically arranged on both sides of the boiler water pump unit; the inner shell includes a first water chamber inner shell (5) and a second water chamber inner shell (17); a certain expansion gap is set between the inner shell and the outer shell (30), and the inner shell is sealed with a high-temperature elastic material near the end of the boiler water pump unit to prevent the high-temperature boiler water of the boiler water pump unit from flowing in; the first water chamber water inlet (9) and the second water chamber water inlet (16) are connected to the high-pressure water supply pipe from the outlet of the steam-driven water supply pump group through the water chamber water inlet auxiliary regulating valve (8).

4. The integrated hydraulic turbine furnace water circulation pump according to claim 3, characterized in that: The gaps between the inner shell and the rotor of the first water chamber unit and the second water chamber unit adjacent to the boiler water pump unit are sealed by dynamic pressure floating sealing rings, including a first water chamber dynamic pressure floating sealing ring (27) and a second water chamber dynamic pressure floating sealing ring (25), and the other side of the first water chamber dynamic pressure floating sealing ring (27) and the second water chamber dynamic pressure floating sealing ring (25) is the boiler water pump unit interlayer; according to the operating characteristics of the hydraulic turbine boiler water circulation pump, the pressure in the first water chamber unit and the second water chamber unit is always higher than the pressure of the boiler water pump unit inlet and the interlayer connected thereto; the lower temperature feed water in the first water chamber unit and the second water chamber unit can provide cooling for the dynamic pressure floating sealing ring.

5. The integrated hydraulic turbine furnace water circulation pump according to claim 4, characterized in that: Both ends of the outer shell (30) are sealed with mechanical shaft seals, and the mechanical shaft seals include an outer shell front mechanical shaft seal (2) and an outer shell rear mechanical shaft seal (21).

6. A method for starting and stopping an integrated hydraulic turbine boiler water circulation pump according to claim 4 or 5, characterized in that: The method for starting the integrated hydraulic turbine boiler water circulation pump is as follows: The valve states before the hydraulic turbine boiler water circulation pump is started are: the hydraulic turbine water inlet main regulating valve (7) is closed, the hydraulic turbine outlet regulating valve (32) is open, the water chamber water inlet auxiliary regulating valve (8) is closed, the boiler water pump inlet regulating valve (28) and the boiler water pump outlet regulating valve (13) are closed, and the boiler water pump outlet drain regulating valve (14) is open; In the first step, when the supercritical boiler load begins to peak deeply, and the feedwater flow rate drops to near the minimum flow rate of the steam-driven feedwater pump group, the water chamber water inlet auxiliary regulating valve (8) is opened to a certain opening, and the pressure difference between the chambers on both sides of the dynamic pressure floating seal ring is monitored to not exceed the design value. The low-temperature high-pressure feedwater from the outlet of the steam-driven feedwater pump is used to initially preheat the various components of the hydraulic turbine boiler water circulation pump; In the second step, after the initial preheating is completed, when the supercritical boiler load is further reduced, the water chamber inlet auxiliary regulating valve (8) is gradually fully opened, and the boiler water pump inlet regulating valve (28) is opened accordingly, so as to control the pressure difference between the chambers on both sides of the dynamic pressure floating seal ring to not exceed the design value, and use the high-pressure and high-temperature boiler water to further preheat the boiler water pump unit to a state that allows starting; In the third step, after the preheating stage is over, when the supercritical boiler load is further reduced and the boiler water pump needs to be put into operation, the hydraulic turbine water inlet main regulating valve (7) is opened to quickly increase the hydraulic turbine boiler water pump speed. After entering the high-efficiency stable range, the boiler water pump flow is automatically controlled. During this process, the boiler water pump outlet regulating valve (13) is gradually fully opened, and the boiler water pump outlet drain regulating valve (14) is gradually fully closed.

7. The method for starting and stopping an integrated hydraulic turbine boiler water circulation pump according to claim 6, characterized in that: The normal shutdown method of the integrated hydraulic turbine boiler water circulation pump is as follows: when the supercritical boiler load increases and exits deep peak regulation, the hydraulic turbine water inlet main regulating valve (7) can be gradually closed to reduce the speed of the hydraulic turbine boiler water pump, and then the boiler water pump inlet regulating valve (28) and the boiler water pump outlet regulating valve (13) are slowly closed; the boiler water pump outlet drain regulating valve (14) is gradually opened, and the water chamber water inlet auxiliary regulating valve (8) is closed accordingly, so as to control the pressure difference of the chambers on both sides of the dynamic pressure floating seal ring to not exceed the design value; The integrated hydraulic turbine boiler water circulation pump fault accident shutdown method is as follows: when the supercritical boiler is still in deep peak regulation operation, the hydraulic turbine water inlet main regulating valve (7) is quickly closed, the water chamber water inlet auxiliary regulating valve (8) is kept open, and the subsequent shutdown steps are consistent with normal shutdown; this method quickly re-sends the high-pressure feed water from the hydraulic turbine into the main feed water pipeline, so that the feed water flow entering the supercritical boiler is quickly restored and the water outage shutdown fault does not occur; when the supercritical boiler trips, the hydraulic turbine water inlet main regulating valve (7) is quickly closed, the boiler water pump outlet drain regulating valve (14) is quickly opened to prevent the pressure difference on both sides of the dynamic pressure floating seal ring from exceeding the design value, and then the boiler water pump inlet regulating valve (28) and the boiler water pump outlet regulating valve (13) are closed, and finally the water chamber water inlet auxiliary regulating valve (8) is gradually closed.

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