Integrated hydraulic turbine furnace water circulating pump and starting and stopping method

Abstract

The invention discloses an integrated hydraulic turbine furnace water circulating pump and a starting and stopping method. The furnace water circulating pump is sequentially divided into a hydraulic turbine unit, a first water chamber unit, a furnace water pump unit, a second water chamber unit and an axial force balancing unit according to functions. By designing a unique main and auxiliary channel water inlet structure, the problem of water sealing of a high-temperature and high-pressure furnace in a conventional shaft seal pump is solved, the working environment of each sealing element is greatly improved, the service life is prolonged, and meanwhile, the inner core can be integrally pulled out for replacement and is convenient to overhaul. On the basis, a step-by-step pre-heating and rapid shutdown method is further designed, the reliability under frequent start and shutdown is improved, the service life is prolonged, the start and shutdown process is further deeply fused into the deep peak regulation process of the supercritical boiler, the feed water flow of the supercritical boiler can be rapidly recovered after a hydraulic turbine boiler water circulating pump exits due to an accident, and the service life of the supercritical boiler is prolonged. And the fault of water cut-off and shutdown is avoided. Meanwhile, the recycling function of a steam feed pump set can be replaced, and the reliability of a water supply system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of boiler furnace water circulation pumps, and relates to a furnace water circulation pump applied to a supercritical once-through boiler, specifically to an integrated hydraulic turbine furnace water circulation pump and a starting and stopping method thereof. Background Art

[0002] Currently, boiler furnace water circulation pumps generally use electric canned pumps, which are mainly used in the start-up process of supercritical boilers. The electric canned pump adopts a shaft-seal-free structure with a high compressive strength grade, which can effectively avoid the leakage of high-temperature furnace water. Its reliability in continuous operation is relatively high and it has been widely used. However, its bearings generally use the self-lubrication of the conveyed liquid. The pressure fluctuation at the moment of starting and stopping can cause the saturated water to flash and vaporize, the liquid film to rupture to form a gas-liquid two-phase flow, and the bearing lubrication to fail, resulting in a reduction in its reliability under frequent starting and stopping conditions. Since the electric furnace water circulation pump adopts a shaft-seal-free structure and is integrally encapsulated in a closed casing, it is not convenient for maintenance and repair. Generally, it needs to be sent back to the factory for repair, and the repair period is long. When it is applied to the furnace water recirculation scenario in the wet condition of deep peak shaving of a supercritical boiler, the furnace water circulation pump needs to start and stop frequently, and the operating pressure is moderate. The advantages of its high compressive strength grade, strong sealing performance, and high reliability during continuous operation are difficult to play. In addition, when the electric furnace water circulation pump is applied to the furnace water circulation scenario in the wet condition of deep peak shaving of a supercritical once-through boiler, the feed water system includes two power sources, namely an electric furnace water pump and a steam-driven feed water pump group. When the electric furnace water pump fails and exits operation, the feed water system will trigger a water cut-off protection due to insufficient power, resulting in a rapid reduction in the feed water flow rate entering the boiler. The above defects make it difficult to apply in this scenario.

[0003] After the furnace water circulation pump driven by a hydraulic turbine uses the technology disclosed in the patent "A once-through boiler feed water system and control method coupling a steam-driven feed water pump group and a hydraulic turbine booster pump group (hydraulic turbine furnace water circulation pump)" (CN119468191A), it can solve the problem of reduced reliability caused by the parallel connection of multiple power sources in the feed water system. To overcome the problems of insufficient reliability and inconvenient maintenance and repair under frequent starting and stopping conditions of the electric furnace water circulation pump, the present invention discloses an integrated hydraulic turbine furnace water circulation pump and a starting and stopping method thereof. Designed according to the operating characteristics of the furnace water circulation pump of a supercritical once-through boiler, a unique water inlet structure and starting and stopping method are designed on the basis of a reverse pump hydraulic turbine with a conventional shaft seal, realizing the self-sealing of high-temperature and high-pressure furnace water in the furnace water circulation pump. The sealing effect can be comparable to that of a shaft-seal-free electric canned pump. At the same time, this design also takes into account the advantages of the external placement of the bearings of a conventional reverse pump and high reliability under frequent starting and stopping. The pump body core package can be replaced on-site as a whole, which is convenient for maintenance and repair. Summary of the Invention

[0004] The disclosed integrated hydraulic turbine boiler water circulation pump and its starting and stopping method are designed according to the operating characteristics of the boiler water circulation pump in a supercritical once-through boiler. Based on the reverse pump hydraulic turbine with a conventional shaft seal, a unique water inlet structure and starting and stopping 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 can be comparable to that of a shaftless electric canned motor pump. At the same time, this design also takes into account the advantage of high reliability in the frequent starting and stopping of a conventional reverse pump. The pump body core package can be replaced as a whole on-site, making maintenance convenient and overcoming the deficiencies of the electric canned motor pump. Its specific design boundaries are as follows: (1) The power water source of the hydraulic turbine (feed water at the outlet of the motor-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 motor-driven feed water pump is located at the uppermost upstream of the boiler feed water system and has the highest pressure, the pressure of the power water source of the hydraulic turbine (feed water at the outlet of the motor-driven feed water pump) is higher than the inlet pressure of the boiler water circulation pump; according to the different positions of the boiler circulating water, the pressure difference between the two in the deep peak shaving range is 0.5 - 2 MPa. (3) In the load range where the boiler water circulation pump needs to be put into operation, compared with the high-temperature boiler circulating water (300 - 350 °C), the temperature of the power water source of the hydraulic turbine (feed water at the outlet of the motor-driven feed water pump) is lower, generally below 150 °C.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a structure of an integrated hydraulic turbine boiler water circulation pump, which is mainly as follows: The structure of the integrated hydraulic turbine boiler water circulation pump adopts a core package structure widely used in the field of boiler feed water pumps. The core package body is placed as an independent part in the pump housing. The housing has a radially split structure, consisting of an outer cylinder and end covers, with mechanical shaft seals at both ends. The core package body can be withdrawn as a whole, making maintenance convenient.

[0006] The core package body is composed of a rotor and multiple inner housings with different functions. All the inner housings are axially split, which is convenient for installation and maintenance. They are sequentially 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. The function of the hydraulic turbine unit is to provide power for the hydraulic turbine boiler water circulation pump. The functions of the first water chamber and the second water chamber are to serve as the secondary water inlet channels of the hydraulic turbine and the preheating channels before startup, 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 function of the boiler water pump unit is to pressurize the circulating boiler water, and the function of the axial force balance unit is to balance the axial forces generated by the hydraulic turbine unit and the boiler water pump unit.

[0007] The described hydraulic turbine unit adopts an arrangement similar to that of a conventional multi-stage centrifugal reverse pump, and is composed of an inner volute of the hydraulic turbine and multi-stage hydraulic turbine impellers. The inner volute of the hydraulic turbine adopts a split structure with a split plane. The hydraulic turbine impellers are installed on the rotor of this unit. The interlayer between the inner volute of the hydraulic turbine and the outer casing is connected to the main inlet of the hydraulic turbine. The main inlet of the hydraulic turbine is connected to the high-pressure feed water pipeline coming from the outlet of the steam-driven feed water pump group through the main regulating valve for the hydraulic turbine inlet water. The outlet of the hydraulic turbine is connected to the low-pressure feed water pipeline going to the deaerator of the unit through the regulating valve for the hydraulic turbine outlet.

[0008] The described main regulating valve for the hydraulic turbine inlet water has a quick closing function and can achieve quick shutdown under fault conditions.

[0009] The flow capacity of the described 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 feed pump; this design can ensure sufficient power during the actual operation of the hydraulic turbine. The main regulating valve for the hydraulic turbine inlet water is always in a throttling state, and its speed and output power can be controlled by adjusting the opening of the main regulating valve of the hydraulic turbine.

[0010] The inner shells of the described first water chamber unit and the second water chamber unit are of cylindrical structure, and strengthening ribs can be added inside to enhance the axial stiffness of the inner shell. They are symmetrically arranged on both sides of the boiler feed pump unit. The inner shell includes the inner shell of the first water chamber and the inner shell of the second water chamber; there is a certain expansion gap between the inner shell and the outer casing. The end of the inner shell close to the boiler feed pump unit is sealed with a high-temperature elastic material to prevent the high-temperature boiler water of the boiler feed pump unit from flowing in. The inlet of the first water chamber and the inlet of the second water chamber are connected to the high-pressure feed water pipeline coming from the outlet of the steam-driven feed water pump group through the auxiliary regulating valve for the water chamber inlet water.

[0011] The gap between the inner shell of the first water chamber unit and the second water chamber unit adjacent to the boiler feed pump unit and the rotor is sealed with a dynamic pressure floating seal ring. The other side of the dynamic pressure floating seal ring is the interlayer of the boiler feed pump unit. According to the operating characteristics of the hydraulic turbine boiler water circulation pump, the pressures in the two water chambers are always higher than the pressure at the inlet of the boiler feed pump unit and the interlayer connected thereto. Even if the dynamic pressure floating seal ring fails, it will not cause the boiler water to leak out, realizing the function of self-sealing for high-temperature boiler water. The relatively low-temperature feed water in the water chamber can provide cooling for the dynamic pressure floating seal ring.

[0012] The described first water chamber unit and second water chamber unit serve as the secondary water inlet channels of the hydraulic turbine. The secondary water inlet channels are structured as follows: The high-pressure feed water entering the first water chamber unit flows into the interlayer of the hydraulic turbine unit through the gap between the inner shell adjacent to the hydraulic turbine unit side and the rotor; the high-pressure feed water entering the second water chamber unit flows into the front chamber of the axial force balance unit through the gap between the inner shell adjacent to the axial force balance unit side and the rotor, and then flows into the interlayer of the hydraulic turbine unit through the connecting pipe of the front chamber of the axial force balance unit. The high-pressure feed water flowing into the interlayer of the hydraulic turbine ultimately flows to the main inlet of the hydraulic turbine. The gap size or throttling kit on the secondary water inlet channel is determined according to the required flow rate of the first water chamber unit and the second water chamber unit.

[0013] The flow rate passing through the described first water chamber unit and second water chamber unit is determined according to the remaining flow rate required for the inlet high-pressure feed water pipeline of the hydraulic turbine unit to quickly close the main regulating valve at the water inlet of the hydraulic turbine without causing a destructive water hammer effect; specifically, it can be achieved by adjusting the gap size between the inner shell of the water chamber and the rotor on the secondary water inlet channel or the throttling capacity of the throttling kit installed at this gap.

[0014] The described boiler feed pump unit adopts a structure similar to that of a conventional single-stage centrifugal pump, consisting of a 1-stage boiler feed pump impeller and an inner volute of the boiler feed pump. The boiler feed pump impeller adopts a double-suction structure. The interlayer between its inner volute of the boiler feed pump and the outer shell is connected to the inlet of the boiler feed pump, and the interlayer in the outlet area of the boiler feed pump is sealed with a high-pressure metal bellows. The boiler feed pump unit includes a boiler feed pump inlet and a boiler feed pump outlet; the boiler feed pump inlet is connected to the boiler water pipeline from the storage tank of the boiler separator through the boiler feed pump inlet regulating valve. A boiler feed pump outlet regulating valve is provided on the connecting pipeline at the outlet of the boiler feed pump. The boiler feed pump outlet is connected to the boiler water pipeline leading to the inlet of the boiler economizer through the boiler feed pump outlet regulating valve; a boiler feed pump outlet drain regulating valve is provided on the pipeline before the boiler feed pump outlet regulating valve, which is connected to the boiler drain flash tank.

[0015] The described axial force balance unit adopts a thrust balance structure similar to that of a conventional multi-stage centrifugal pump, including an axial force balance inner housing, a front chamber of the axial force balance unit, a rear chamber of the axial force balance unit, an axial force balance plate, and an axial force balance disc; the axial force balance inner housing and the inner housing of the second water chamber can be designed as an integral body, the axial force balance plate is installed on the axial force balance inner housing, and the axial force balance disc is installed at the corresponding position of the rotor. The front chamber of the axial force balance unit is enclosed by the axial force balance plate and the inner housing of the second water chamber, and is connected to the interlayer of the hydraulic turbine unit through the connecting pipe of the front chamber of the axial force balance unit. The rear chamber of the axial force balance unit is enclosed by the axial force balance disc and the inner housing of the axial force balance inner housing, and is connected to the outlet of the hydraulic turbine through the connecting pipe of the rear chamber of the axial force balance unit. Part of the high-pressure feed water from the second water chamber unit is depressurized through the gap between the axial force balance disc and the axial force balance plate, and finally flows to the outlet of the hydraulic turbine, generating the required axial thrust on the axial force balance disc. The gap between the axial force balance disc and the axial force balance plate can be dynamically changed according to the required axial thrust.

[0016] The described starting method of the integrated hydraulic turbine boiler circulating pump is as follows: The states of each valve before starting the hydraulic turbine boiler circulating pump are as follows: the main regulating valve for the inlet of the hydraulic turbine is closed, the regulating valve for the outlet of the hydraulic turbine is open, the auxiliary regulating valve for the inlet of the water chamber is closed, the regulating valves for the inlet and outlet of the boiler feed pump are closed, and the drain regulating valve for the outlet of the boiler feed pump is open.

[0017] First step, when the supercritical boiler load starts deep peak shaving and the feed water flow rate decreases to near the minimum flow rate of the steam-driven feed pump group, the auxiliary regulating valve for the inlet of the water chamber is opened to a certain opening degree, and the pressure difference between the two chambers on both sides of the dynamic pressure floating seal ring is monitored not to exceed the design value. The relatively low-temperature high-pressure feed water from the outlet of the steam-driven feed pump is used to initially preheat each component of the hydraulic turbine boiler circulating pump.

[0018] Second step, after the initial preheating is completed, when the supercritical boiler load further decreases, the auxiliary regulating valve for the inlet of the water chamber is gradually fully opened, and the regulating valve for the inlet of the boiler feed pump follows to open, controlling the pressure difference between the two chambers on both sides of the dynamic pressure floating seal ring not to exceed the design value. The high-pressure and high-temperature boiler water is used to further preheat the boiler feed pump unit to the allowable starting state.

[0019] Third step, at the end of the preheating stage, when the supercritical boiler load further decreases and it is necessary to put the boiler feed pump into operation, the main regulating valve for the inlet of the hydraulic turbine is opened to quickly increase the speed of the hydraulic turbine boiler circulating pump. After entering the high-efficiency and stable range, the flow rate of the boiler feed pump is automatically controlled; during this process, the regulating valve for the outlet of the boiler feed pump is gradually fully opened, and the drain regulating valve for the outlet of the boiler feed pump is gradually fully closed.

[0020] The normal shutdown method of the integrated hydraulic turbine boiler water circulation pump is as follows: When the supercritical boiler load increases and it exits the deep peak shaving, the main regulating valve for the hydraulic turbine inlet can be gradually closed to reduce the speed of the hydraulic turbine boiler water pump, and then the inlet regulating valve and outlet regulating valve of the boiler water pump are slowly closed; the outlet drain regulating valve of the boiler water pump is gradually opened, and the auxiliary regulating valve for the water chamber inlet follows to close, controlling the pressure difference between the two chambers on both sides of the dynamic pressure floating seal ring not to exceed the design value.

[0021] The fault shutdown method of the integrated hydraulic turbine boiler water circulation pump is as follows: When the supercritical boiler is still in deep peak shaving operation, quickly close the main regulating valve for the hydraulic turbine inlet, and keep the auxiliary regulating valve for the water chamber inlet open. The subsequent shutdown steps are the same as those for normal shutdown. This design can quickly send the high-pressure feed water passing through the hydraulic turbine back into the main feed water pipeline, quickly restore the feed water flow rate entering the supercritical boiler, and prevent the failure of water cut-off shutdown. When the supercritical boiler trips, quickly close the main regulating valve for the hydraulic turbine inlet, quickly open the outlet drain regulating valve of the boiler water pump to prevent the pressure difference between the two sides of the dynamic pressure floating seal ring from exceeding the design value, then close the inlet regulating valve and outlet regulating valve of the boiler water pump, and finally gradually close the auxiliary regulating valve for the water chamber inlet.

[0022] During the startup process of the hydraulic turbine boiler water circulation pump, as the load of the supercritical boiler decreases, the flow rate of the high-pressure feed water flowing back to the deaerator through the hydraulic turbine boiler water circulation pump gradually increases. This feature is the same as the function of the recirculation valve of the steam-driven feed water pump, so the recirculation valve of the steam-driven feed water pump group does not need to be put into operation throughout the process, reducing the disturbance of its feed water system and avoiding the problem of internal leakage of the recirculation valve of the steam-driven feed water pump group. In addition, this step-by-step preheating method can reduce the thermal stress during the preheating process, reduce the probability of jamming caused by uneven expansion of components, and improve the reliability and service life of the hydraulic turbine boiler water circulation pump under frequent startup and shutdown.

[0023] The integrated hydraulic turbine boiler water circulation pump and its startup and shutdown method disclosed in the present invention have the following innovations: (1) Design a unique main and auxiliary channel water inlet structure, which not only solves the problem of sealing high-temperature and high-pressure boiler water in conventional shaft-sealed pumps, but also greatly improves the working environment of each seal, significantly extends the service life, and at the same time the inner core can be taken out as a whole for replacement, making maintenance convenient.

[0024] (2) Design a method of step-by-step preheating and quick shutdown, which not only improves the reliability and service life under frequent startup and shutdown, but also deeply integrates its startup and shutdown process into the deep peak shaving process of the supercritical boiler, enabling the feed water flow rate of the supercritical boiler to quickly recover after the hydraulic turbine boiler water circulation pump fails to withdraw, without the failure of water cut-off shutdown. At the same time, it can replace the recirculation function of the steam-driven feed water pump group and improve the reliability of the feed water system. Description of the Drawings

[0025] Figure 1This is the structure of the integrated hydraulic turbine boiler water circulation pump of the present invention; In the figure:

[0026] 1. Rotor; 2. Front mechanical shaft seal of the outer casing; 3. Inner volute of the hydraulic turbine; 4. Impeller of the hydraulic turbine; 5. Inner casing of the first water chamber; 6. Main inlet of the hydraulic turbine; 7. Main regulating valve for the inlet of the hydraulic turbine; 8. Auxiliary regulating valve for the inlet of the water chamber; 9. Inlet of the first water chamber; 10. Inner volute of the boiler water pump; 11. High-pressure metal bellows; 12. Outlet of the boiler water pump; 13. Regulating valve for the outlet of the boiler water pump; 14. Drain regulating valve for the outlet of the boiler water pump; 15. Impeller of the boiler water pump; 16. Inlet of the second water chamber; 17. Inner casing of the second water chamber; 18. Front chamber of the axial force balance unit; 19. Axial force balance plate; 20. Axial force balance disk; 21. Rear mechanical shaft seal of the outer casing; 22. Rear chamber of the axial force balance unit; 23. Connecting pipe for the rear chamber of the axial force balance unit; 24. Connecting pipe for the front chamber of the axial force balance unit; 25. Dynamic pressure floating seal ring for the second water chamber; 26. Inlet of the boiler water pump; 27. Dynamic pressure floating seal ring for the first water chamber; 28. Regulating valve for the inlet of the boiler water pump; 29. Interlayer of the hydraulic turbine unit; 30. Outer casing; 31. Outlet of the hydraulic turbine; 32. Regulating valve for the outlet of the hydraulic turbine. Specific embodiments

[0027] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts shall fall within the scope protected by the present invention.

[0028] As Figure 1 shown, the structure of the integrated hydraulic turbine boiler water circulation pump described in the present invention adopts the cartridge structure widely used in the field of boiler feed pumps. The cartridge body is placed in the outer casing 30 as an independent part and can be withdrawn as a whole. The two ends of the pump casing are respectively sealed by the front mechanical shaft seal 2 and the rear mechanical shaft seal 21 of the outer casing. Since it only bears the pressure and temperature at the outlet end of the hydraulic turbine, the working environment is good, and there are no special requirements for the mechanical seal performance, so mature products can be selected. The outer casing 30 generally adopts a radial split structure, which is composed of an outer cylinder and an end cover, and has a high overall compressive strength, reaching about 40 MPa, which can fully meet the working pressure requirements of the hydraulic turbine boiler water circulation pump.

[0029] The described cartridge body is composed of a rotor 1 and multiple inner casings combined. The inner casings all adopt axial splitting, which is convenient for installation and maintenance, and are sequentially 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 functions.

[0030] The described hydraulic turbine unit adopts a layout similar to that of a conventional multi-stage centrifugal reverse pump, and is composed of an inner volute 3 of the hydraulic turbine and a hydraulic turbine impeller group 4. According to the pressure difference before and after, 3 to 5 stages of impellers can be set. The interlayer 29 of the hydraulic turbine unit between the inner volute 3 of the hydraulic turbine and the outer casing 30 is connected to the main inlet 6 of the hydraulic turbine. The main inlet 6 of the hydraulic turbine is connected to the high-pressure feed water pipeline coming from the outlet of the steam-driven feed water pump group through the main regulating valve 7 for the inlet of the hydraulic turbine. The outlet 31 of the hydraulic turbine is connected to the low-pressure feed water pipeline going to the deaerator of the unit through the regulating valve 32 for the outlet of the hydraulic turbine. The inner volute 3 of the hydraulic turbine only bears compressive stress, so only small bolts can be used to seal the split surface.

[0031] The described first inner casing 5 of the water chamber and the second inner casing 17 of the water chamber are of cylindrical structure, and reinforcing ribs can be added inside to enhance the axial stiffness, and they are symmetrically arranged on both sides of the boiler feed pump unit. The inlet 9 of the first water chamber and the inlet 16 of the second water chamber are connected to the high-pressure feed water pipeline coming from the outlet of the steam-driven feed water pump group through the auxiliary regulating valve 8 for the inlet of the water chamber. A certain expansion gap is provided between the first inner casing 5 and the second inner casing 17 of the water chamber and the outer casing 30, and the end near the boiler feed pump unit of the inner casing is sealed with a high-temperature elastic material to prevent the high-temperature boiler water of the boiler feed pump unit from flowing in.

[0032] The gap between the first inner casing 5 of the first water chamber unit and the rotor 1 on the side adjacent to the boiler feed pump unit is sealed by the first dynamic pressure floating seal ring 27 of the water chamber. The gap between the first inner casing 5 of the first water chamber unit and the rotor 1 on the other side is not sealed directly by a seal or is connected to the interlayer 29 of the hydraulic turbine unit through a throttling kit. The gap between the second inner casing 17 of the second water chamber unit and the rotor 1 on the side adjacent to the boiler feed pump unit is sealed by the second dynamic pressure floating seal ring 25 of the water chamber. The gap between the second inner casing 17 of the second water chamber unit and the rotor 1 on the other side is not sealed directly by a seal or is connected to the front chamber 18 of the axial force balance unit through a throttling kit. The first inner casing 5 and the second inner casing 17 of the water chamber serve as the auxiliary water inlet channels of the hydraulic turbine, and the inflowing high-pressure feed water finally flows to the main inlet of the hydraulic turbine. The size of the gap or the throttling capacity of the throttling kit on the auxiliary water inlet channels is determined according to the required flow rate of the first water chamber unit and the second water chamber unit.

[0033] The described boiler feed pump unit adopts a structure similar to that of a conventional single-stage centrifugal pump, and is composed of a 1-stage boiler feed pump impeller 15 and an inner volute 10 of the boiler feed pump. The boiler feed pump impeller 15 adopts a double-suction structure with self-balanced axial force. The interlayer between its inner volute 10 of the boiler feed pump and the outer casing 30 is connected to the inlet 26 of the boiler feed pump. The interlayer in the outlet area is sealed by a high-pressure metal bellows 11. The inlet 26 of the boiler feed pump is connected to the boiler water pipeline coming from the storage tank of the boiler separator through the regulating valve 28 for the inlet of the boiler feed pump. The outlet 12 of the boiler feed pump is connected to the boiler water pipeline going to the inlet of the economizer of the boiler through the regulating valve 13 for the outlet of the boiler feed pump. A regulating valve 14 for draining the boiler feed pump is arranged on the pipeline before the regulating valve 13 for the outlet of the boiler feed pump, and is connected to the boiler drain flash tank.

[0034] The described axial force balance unit adopts a thrust balance structure similar to that of a conventional multi-stage centrifugal pump, including an axial force balance inner housing, a front chamber 18 of the axial force balance unit, a rear chamber 22 of the axial force balance unit, an axial force balance plate 19, and an axial force balance disk 20. The axial force balance inner housing can be designed as an integral structure with the inner housing 17 of the second water chamber. The axial force balance plate 19 is installed on the inner housing 17 of the second water chamber, and the axial force balance disk 20 is installed at the corresponding position of the rotor 1. The front chamber 18 of the axial force balance unit is enclosed by the axial force balance plate 19 and the inner housing 17 of the second water chamber, and it is connected to the interlayer 29 of the hydraulic turbine unit through the connecting pipe 24 of the front chamber of the axial force balance unit. The rear chamber 22 of the axial force balance unit is enclosed by the axial force balance disk 20 and the axial force balance inner housing, and it is connected to the hydraulic turbine outlet 31 through the connecting pipe 23 of the rear chamber of the axial force balance unit. Part of the high-pressure feed water from the second water chamber unit is depressurized through the gap between the axial force balance plate 19 and the axial force balance disk 20, and finally flows to the hydraulic turbine outlet 31, generating the required axial thrust on the axial force balance disk 20. The gap between the axial force balance plate 19 and the axial force balance disk 20 can be dynamically changed according to the required axial thrust. Since the boiler feed pump unit adopts a single-stage double-suction impeller structure with self-balanced axial force, the axial force balance unit is mainly responsible for balancing the thrust generated by the hydraulic turbine unit.

[0035] The function of the described hydraulic turbine unit is to provide power for the hydraulic turbine boiler feed pump. The functions of the first water chamber unit and the second water chamber unit are to serve as the auxiliary water inlet channel of the hydraulic turbine and the preheating channel before startup, responsible for isolating and sealing the high-temperature and high-pressure boiler water of the boiler feed pump unit, and providing low-temperature coolant for its sealing device. The function of the boiler feed pump unit is to boost the circulating boiler water, and the function of the axial force balance unit is to balance the axial forces generated by the hydraulic turbine unit and the boiler feed pump unit.

[0036] The flow capacity of the hydraulic turbine is designed according to the lowest head of the hydraulic turbine during unit operation and the power required by the boiler feed pump unit. This design can ensure sufficient power for the hydraulic turbine. During actual operation, the main regulating valve 7 for the hydraulic turbine inlet is always in a throttling state, and the speed and actual output power of the hydraulic turbine can be controlled by the opening degree of the main regulating valve 7 for the hydraulic turbine inlet. The main regulating valve 7 for the hydraulic turbine inlet has a quick closing function and can achieve quick shutdown under fault conditions.

[0037] According to the operating characteristics of the hydraulic turbine boiler water circulation pump, the pressure inside the first water chamber inner shell 5 and the second water chamber inner shell 17 is always higher than the pressure at the inlet of the boiler water pump 26 and the pressure of the interlayer connected thereto. Even if the dynamic pressure floating seal ring 27 of the first water chamber or the dynamic pressure floating seal ring 25 of the second water chamber fails, it will not cause the leakage of boiler water. At the same time, the feed water with a lower temperature inside the first water chamber inner shell 5 and the second water chamber inner shell 17 can provide cooling for the dynamic pressure floating seal ring. Since the dynamic pressure floating seal ring is a non-contact sealing technology, it can utilize the kinetic energy of rotation to suck the low-temperature feed water into the sealing surface to form a liquid film for sealing, and cool the sealing surface. The cooling flow rate can be determined by designing the flow channel of the sealing surface, and it has a long service life. In addition, the leakage amount of the dynamic pressure floating seal ring in the static state is much higher than that in the high-speed operating state. This characteristic can be used to provide the feed water required for preheating from the water chamber to the boiler water pump unit during the initial preheating stage of the pump body.

[0038] The required flow rates of the first water chamber unit and the second water chamber unit are determined according to the remaining flow rates required for the high-pressure feed water pipeline at the main inlet of the hydraulic turbine to quickly close the main inlet regulating valve 7 of the hydraulic turbine without causing destructive water hammer effects. The design principle is that the auxiliary water inlet channel of the hydraulic turbine always remains fully open. The larger its flow rate, the smaller the change in the pipeline flow velocity before and after the main inlet regulating valve 7 of the hydraulic turbine is quickly closed, and the water hammer effect caused by the sudden change in flow velocity will be greatly reduced. At the same time, in order to further reduce the water hammer effect, energy-absorbing devices such as accumulators can also be arranged on the pipeline.

[0039] The interlayer of the boiler water pump unit is designed to be connected to the inlet mainly considering that the head of the boiler water pump is small, the pressure difference between the inner and outer shells is small, the inner shell is installed with a horizontal axial split, and the stress borne by the bolts on the split surface is not large. The existing technology can fully meet the requirements. At the same time, this design can eliminate the shaft seal device at the water inlets on both sides of the boiler water pump unit, further improving the reliability of the boiler water pump.

[0040] The starting method of the integrated hydraulic turbine boiler water circulation pump is as follows: The states of each valve before the start of the hydraulic turbine boiler water circulation pump are: the main inlet regulating valve 7 of the hydraulic turbine is closed, the outlet regulating valve 32 of the hydraulic turbine is opened, the auxiliary regulating valve 8 for water chamber inlet is closed, the inlet regulating valve 28 of the boiler water pump and the outlet regulating valve 13 of the boiler water pump are closed, and the outlet drain regulating valve 14 of the boiler water pump is opened.

[0041] In the first step, when the supercritical boiler load starts deep peak shaving and the feed water flow rate drops to near the minimum flow rate of the steam-driven feed water pump group, the auxiliary regulating valve 8 for water chamber inlet is opened to a certain opening degree, and the pressure difference between the two chambers on both sides of the dynamic pressure floating seal ring is monitored not to exceed the design value. The initial preheating of each component of the hydraulic turbine boiler water circulation pump is carried out by using the low-temperature high-pressure feed water from the outlet of the steam-driven feed water pump.

[0042] Second step, after the initial preheating is completed, when the load of the supercritical boiler further decreases, gradually fully open the auxiliary regulating valve 8 for water chamber inlet, and the inlet regulating valve 28 of the boiler water pump follows to open, controlling the pressure difference between the two chambers on both sides of the dynamic pressure floating seal ring not to exceed the design value, and using the high-pressure and high-temperature boiler water to further preheat the boiler water pump unit to the allowable starting state.

[0043] Third step, when the preheating stage is completed and the load of the supercritical boiler further decreases and it is necessary to put the boiler water pump into operation, open the main regulating valve 7 for hydraulic turbine inlet to quickly increase the speed of the hydraulic turbine boiler water pump. After entering the high-efficiency and stable range, then automatically control the flow rate of the boiler water pump. During this process, the outlet regulating valve 13 of the boiler water pump is gradually fully opened, and the outlet drain regulating valve 14 of the boiler water pump is gradually fully closed.

[0044] During the startup process of the described hydraulic turbine boiler water circulation pump, as the load of the supercritical boiler decreases, the flow rate of the high-pressure feed water returned to the deaerator through the hydraulic turbine boiler water circulation pump gradually increases. This feature is consistent with the function of the recirculation valve of the steam-driven feed water pump, and the recirculation valve of the steam-driven feed water pump unit does not need to be put into operation throughout the process, reducing its disturbance to the feed water system. In addition, this step-by-step preheating method can reduce the thermal stress during the preheating process, reduce the probability of jamming caused by uneven expansion of components, and improve the reliability and service life of the hydraulic turbine boiler water circulation pump under frequent startup and shutdown.

[0045] The normal shutdown method of the described integrated hydraulic turbine boiler water circulation pump is as follows: when the supercritical boiler load increases and exits the deep peak shaving, the main regulating valve 7 for hydraulic turbine inlet can be gradually closed to reduce the speed of the hydraulic turbine boiler water pump, and then slowly close the inlet regulating valve 28 of the boiler water pump and the outlet regulating valve 13 of the boiler water pump; the outlet drain regulating valve 14 of the boiler water pump is gradually opened, and the auxiliary regulating valve 8 for water chamber inlet follows to close, controlling the pressure difference between the two chambers on both sides of the dynamic pressure floating seal ring not to exceed the design value.

[0046] The fault shutdown method of the described integrated hydraulic turbine boiler water circulation pump is as follows: when the supercritical boiler is still in deep peak shaving operation, quickly close the main regulating valve 7 for hydraulic turbine inlet, and the auxiliary regulating valve 8 for water chamber inlet remains open. The subsequent shutdown steps are the same as those for normal shutdown. This design can quickly send the high-pressure feed water passing through the hydraulic turbine back into the main feed water pipeline, quickly restore the feed water flow rate entering the supercritical boiler, and prevent the failure of water cut-off shutdown. When the supercritical boiler trips, quickly close the main regulating valve 7 for hydraulic turbine inlet, quickly open the outlet drain regulating valve 14 of the boiler water pump to prevent the pressure difference between the two sides of the dynamic pressure floating seal ring from exceeding the design value, then close the inlet regulating valve 28 of the boiler water pump and the outlet regulating valve 13 of the boiler water pump, and finally gradually close the auxiliary regulating valve 8 for water chamber inlet.

[0047] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claimed rights.

Claims

1. An integrated hydraulic turbine furnace 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 functions. The hydraulic turbine unit provides power for the hydraulic turbine boiler water circulation pump, the first water chamber unit and the second water chamber unit serve as auxiliary water inlet channels of the hydraulic turbine and preheating channels before startup, 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 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.

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 mounted 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 shell of the first water chamber unit and the second water chamber unit is a columnar structure, and reinforcing ribs are added inside to enhance the axial rigidity of the inner shell. 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 comprises a first water chamber inner shell (5) and a second water chamber inner shell (17); a certain expansion gap is provided 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 pipeline 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 a 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: The boiler water pump unit adopts a single-stage centrifugal pump structure, and is composed of a first-stage boiler water pump impeller (15) and a boiler water pump inner volute (10). 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). The interlayer in the area of ​​the boiler water pump outlet (12) is sealed by 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); 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.

6. The integrated hydraulic turbine furnace water circulation pump according to claim 5, characterized in that: The axial force balancing unit adopts 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 and the second water chamber inner housing (17) are designed as a whole, the axial force balancing plate (19) is mounted on the axial force balancing inner housing, and the axial force balancing disc (20) is mounted at a corresponding position of the rotor (1); the axial force balancing unit front chamber (18) is formed by the axial force balancing plate (19) and the second water chamber inner housing (17), and is connected to the rotor (1) via the axial force balancing unit front chamber. The chamber connecting 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.

7. The integrated hydraulic turbine furnace water circulation pump according to claim 6, characterized in that: 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 channel is 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 front chamber (18) of the axial force balancing unit 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 front chamber connecting pipe (24) of the axial force balancing unit; the high-pressure feed water flowing into the hydraulic turbine unit interlayer (29) finally 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 close quickly when the hydraulic turbine water inlet main regulating valve (7) is closed without causing a destructive water hammer effect; this can be achieved by adjusting the gap between the inner shell of the water chamber and the rotor on the auxiliary water inlet channel or the throttling capacity of the throttling kit installed at the gap.

8. The integrated hydraulic turbine furnace water circulation pump according to claim 7, 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).

9. A method for starting and stopping an integrated hydraulic turbine boiler water circulation pump as claimed in claim 7 or 8, characterized in that: The method for starting the integrated hydraulic turbine boiler water circulation pump is as follows: Before the hydraulic turbine boiler water circulation pump is started, the valve states are as follows: 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 be deeply peaked, and the feedwater flow rate is reduced 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 be not greater than the design value, and the various components of the hydraulic turbine boiler water circulation pump are initially preheated using the relatively low-temperature high-pressure feedwater from the outlet of the steam-driven feedwater pump; In the second step, after the initial preheating is completed, when the supercritical boiler load is further reduced, the water chamber water inlet auxiliary regulating valve (8) is gradually fully opened, and the boiler water pump inlet regulating valve (28) is opened accordingly, so that the pressure difference of the chambers on both sides of the dynamic pressure floating seal ring does not exceed the design value, and the boiler water pump unit is further preheated to a state that allows startup by using high-pressure and high-temperature boiler water; 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 speed of the hydraulic turbine boiler water pump. After entering the high-efficiency 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.

10. The method for starting and stopping an integrated hydraulic turbine boiler water circulation pump according to claim 9, 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 not to 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 in an open state, and the subsequent shutdown steps are consistent with normal shutdown; the 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 supply failure shutdown 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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