A steam turbine stationary blade heating and dehumidifying system coupled with waste heat recovery

Abstract

The application belongs to the technical field of steam turbines, and relates to a steam turbine stationary blade heating and dehumidifying system coupled with waste heat recovery, which comprises a steam turbine, a condenser, a low-pressure heater and a deaerator connected in sequence, a heating channel is arranged in the last-stage stationary blade in the steam turbine, the inlet of the heating channel is communicated with the steam extraction port of the steam turbine, and the steam-water separator and the switching control unit are further included. The steam-water separator is used for separating the outlet medium after heat exchange into steam and liquid, and the separated steam-phase medium is sent back to the deaerator, the low-pressure heater or the condenser in stages by the switching control unit according to the pressure grade of the separated steam-phase medium, so that the waste heat originally directly discharged into the condenser can be recovered and utilized in stages, the remaining work capacity in the steam after heat exchange can be effectively recovered to the heat recovery system, the complete loss of the work capacity of the steam after heat exchange is avoided, the loss of the effective work capacity of the unit is reduced, and the circulating thermal efficiency of the unit and the economy of overall operation are improved.

Description

Technical Field

[0001] This invention belongs to the field of steam turbine technology and relates to a steam turbine stator blade heating and dehumidification system coupled with waste heat recovery. Background Technology

[0002] During normal operation of a wet steam turbine, the main steam flows sequentially through the turbine, condenser, condensate pump, low-pressure heater, deaerator, feedwater pump, and high-pressure heater before being sent to the boiler, forming a complete regenerative cycle system. This system heats the condensate through extraction steam at each stage to improve the unit's cycle thermal efficiency. The steam expands progressively within the turbine's low-pressure cylinder, and its humidity gradually increases as pressure and temperature decrease. Especially in the final low-pressure stage, the wet steam contains a large number of fine droplets, which easily deposit on the surface of the stationary blades and gradually form a water film. Under the action of the main steam flow and the shear force on the blade surface, the water film migrates downstream along the stationary blade surface, rupturing, being ejected, and re-atomizing near the trailing edge of the stationary blade, thus forming larger secondary droplets. Due to the velocity slip between the secondary droplets and the main steam flow, when these droplets are carried by high-speed steam and impact downstream moving blades, they can easily cause erosion damage to the leading edge, tip, and other high-relative-velocity areas of the moving blades. To reduce the risk of blade erosion and improve unit performance, the industry commonly uses static blade dehumidification methods.

[0003] Currently, for dehumidification of turbine stationary blades, heating channels are often installed inside the stationary blades. Turbine extraction steam or auxiliary steam is then used as the heat source and introduced into the heating channels. The high-temperature steam transfers heat to the metal wall of the stationary blades, increasing the overall temperature of the outer surface and accelerating the evaporation rate of surface droplets and water films, thereby inhibiting water film development and secondary droplet formation. After heat exchange, the steam pressure drops significantly, and since it is mostly a two-phase medium of steam and water, it cannot be directly connected to low-pressure heaters, deaerators, or other regenerative equipment. Therefore, the industry generally discharges it directly into the condenser.

[0004] However, since the heated steam after heat exchange is directly discharged into the condenser, the residual heat inside cannot be recovered, resulting in the complete loss of the original work capacity of this steam. This leads to a reduction in the effective work output of the unit, which significantly reduces the unit's cycle thermal efficiency and ultimately affects the overall economic efficiency of the unit's operation. Summary of the Invention

[0005] The purpose of this invention is to provide a turbine stator blade heating and dehumidification system coupled with waste heat recovery, which can reduce the energy loss of heating steam and improve the overall economic efficiency of the unit operation.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A turbine stator blade heating and dehumidification system coupled with waste heat recovery includes a turbine, a condenser, a low-pressure heater, and a deaerator connected in sequence. The last-stage stator blades within the turbine have a heating channel for the flow of heated steam. The inlet of the heating channel is connected to the turbine's extraction port, which is located upstream of the last-stage stator blades. The system also includes: The steam-water separator has its inlet connected to the outlet of the heating channel. The vapor phase outlet of the steam-water separator is connected to the steam inlet of the condenser, the steam inlet of the low-pressure heater, and the steam inlet of the deaerator, respectively. The steam-water separator is used to separate the outlet medium after heat exchange into a vapor phase medium and a liquid phase medium. The switching control unit, located at the vapor phase outlet of the steam-water separator, is used to selectively guide the vapor medium into the condenser, low-pressure heater, or deaerator based on its pressure. When the vapor medium pressure is higher than the deaerator's operating pressure, it is guided into the deaerator; when the vapor medium pressure is lower than the deaerator's operating pressure but higher than the low-pressure heater's operating pressure, it is guided into the low-pressure heater; and when the vapor medium pressure is lower than the low-pressure heater's operating pressure, it is guided into the condenser.

[0007] The invention is further characterized by: The switching control unit includes: a switching valve, the inlet of which is connected to the vapor phase outlet of the steam-water separator, and three outlets which are respectively connected to the steam inlet of the condenser, the steam inlet of the low-pressure heater, and the steam inlet of the deaerator; and a controller, which is electrically connected to the switching valve and is used to selectively guide the vapor phase medium into the condenser, the low-pressure heater, or the deaerator according to the pressure of the vapor phase medium.

[0008] A return steam pressure regulating valve and a check valve are sequentially installed between the vapor phase outlet of the steam-water separator and the switching valve.

[0009] The extraction ports include the front extraction port of the steam turbine, the exhaust port of the intermediate pressure cylinder, and the front extraction port of the low pressure cylinder.

[0010] The extraction steam port is connected to the inlet of the heating channel via an extraction steam switching valve. The extraction steam switching valve is electrically connected to the controller. The controller is used to control the extraction steam switching valve to select the corresponding extraction steam port according to the turbine load. When the turbine load is higher than the preset threshold, the extraction steam port of the turbine's low-pressure cylinder front stage is selected as the source of heating steam. When the turbine load is lower than the preset threshold, the extraction steam port of the turbine's front stage or the exhaust steam port of the intermediate-pressure cylinder is selected as the source of heating steam.

[0011] A pressure reducing valve and a flow regulating valve are sequentially installed between the extraction steam switching valve and the inlet of the heating channel.

[0012] The liquid phase outlet of the steam-water separator is connected to a hydrophobic expansion container, and a hydrophobic regulating valve is installed at the liquid phase outlet of the steam-water separator.

[0013] The internal heating channel of the last stage stationary blade has a single-pass or multi-pass structure.

[0014] The turbine stator blade heating and dehumidification system coupled with waste heat recovery according to the present invention has the following advantages: This invention uses a steam-liquid separator to separate the outlet medium after heat exchange. Based on the pressure level of the separated vapor medium, a switching control unit is used to return it in stages to the deaerator, low-pressure heater, or condenser. This allows the waste heat that would otherwise be lost by directly discharging into the condenser to be recovered and utilized in stages. The remaining work capacity of the steam after heat exchange is effectively recovered to the regenerative system, avoiding the complete loss of the steam's work capacity after heat exchange, reducing the loss of the unit's effective work, and thus improving the unit's cycle thermal efficiency and overall operating economy. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0016] Figure 2 This is a schematic diagram of a typical steam turbine regenerative system.

[0017] Figure label: 1. Steam turbine; 2. Condenser; 3. First booster pump; 4. Low-pressure heater; 5. Deaerator; 6. Second booster pump; 7. High-pressure heater; 8. Boiler; 9. Steam extraction source; 10. Steam extraction switching valve; 11. Pressure reducing regulating valve; 12. Flow regulating valve; 13. Last stage stationary vane; 14. Steam-water separator; 15. Return steam pressure regulating valve; 16. Check valve; 17. Switching valve; 18. Drainage regulating valve; 19. Drainage expansion tank. Detailed Implementation

[0018] The technical solutions of the present invention will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of the present invention, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0019] like Figure 2The diagram shows a typical steam turbine regenerative system, illustrating the basic thermodynamic cycle environment upon which this invention is based. This system comprises a steam turbine 1, a condenser 2, a first booster pump 3, a low-pressure heater 4, a deaerator 5, a second booster pump 6, a high-pressure heater 7, and a boiler 8, connected sequentially. The main steam generated by the boiler 8 enters the steam turbine 1 and expands to perform work. The exhaust steam from the steam turbine 1 enters the condenser 2 and is cooled and condensed to form condensate. The condensate is pressurized by the first booster pump 3 and enters the low-pressure heater 4, where it absorbs heat from the corresponding low-pressure extraction steam or other recovered steam, thus increasing its temperature. The heated condensate then enters the deaerator 5, which thermally deoxygenates the condensate and also provides some mixing and heating. The deoxygenated feedwater is pressurized by the second booster pump 6 and enters the high-pressure heater 7, where it further absorbs heat from higher-pressure extraction steam before returning to the boiler 8, completing the steam-water cycle. Through the above process, the turbine regenerative system uses extracted steam at different pressure levels to heat the condensate in stages, thereby increasing the feedwater temperature entering boiler 8, reducing heat input to the boiler side, and improving the unit's cycle thermal efficiency. The low-pressure heater 4, deaerator 5, and high-pressure heater 7 are regenerative heating devices at different pressure levels. The extracted steam from turbine 1 enters the matching regenerative heating devices according to its pressure, temperature, and system acceptance conditions, and is used to preheat the condensate about to enter the boiler in stages, thereby improving system efficiency and reducing equipment thermal shock. Condenser 2 typically serves as the turbine exhaust steam condensation device, and can also serve as a safe reception location for low-grade steam or steam under abnormal operating conditions.

[0020] like Figure 1 , Figure 2 As shown, this invention provides a turbine stator blade heating and dehumidification system coupled with waste heat recovery. Based on the aforementioned turbine regenerative system, it includes a turbine 1, a condenser 2, a low-pressure heater 4, and a deaerator 5 connected in sequence. The structure of the remaining parts of this system is similar to... Figure 2 The typical steam turbine regenerative system shown is the same, including a first booster pump 3, a second booster pump 6, a high-pressure heater 7, and a boiler 8. The connection relationships between the components are the same as those shown. Figure 2Consistent. Based on this, the last stage stator 13 within the turbine 1 is equipped with a heating channel for the flow of heated steam. The inlet of the heating channel is connected to the extraction port of the turbine 1, which is located upstream of the last stage stator 13. It also includes a steam-water separator 14 and a switching control unit. The inlet of the steam-water separator 14 is connected to the outlet of the heating channel, and the vapor phase outlet of the steam-water separator 14 is connected to the steam inlet of the condenser 2, the steam inlet of the low-pressure heater 4, and the steam inlet of the deaerator 5, respectively. The steam-water separator 14 is used to separate the steam from the outlet after heat exchange. The medium is separated into a vapor phase medium and a liquid phase medium. The switching control unit is located at the vapor phase outlet of the steam-water separator 14. The switching control unit is used to selectively introduce the vapor phase medium into the condenser 2, the low-pressure heater 4, or the deaerator 5 according to the pressure of the vapor phase medium. When the pressure of the vapor phase medium is higher than the working pressure of the deaerator 5, it is introduced into the deaerator 5. When the pressure of the vapor phase medium is lower than the working pressure of the deaerator 5 but higher than the working pressure of the low-pressure heater 4, it is introduced into the low-pressure heater 4. When the pressure of the vapor phase medium is lower than the working pressure of the low-pressure heater 4, it is introduced into the condenser 2. This invention uses a steam-liquid separator 14 to separate the outlet medium after heat exchange. Based on the pressure level of the separated vapor medium, the separation is staged and returned to the deaerator, low-pressure heater, or condenser by a switching control unit. This allows the waste heat that would otherwise be lost by directly discharging into the condenser to be recovered and utilized in stages. The remaining work capacity of the steam after heat exchange is effectively recovered to the regenerative system, avoiding the complete loss of the work capacity of the steam after heat exchange, reducing the loss of the unit's effective work, and thus improving the unit's cycle thermal efficiency and overall operating economy.

[0021] like Figure 1 As shown, the switching control unit includes a switching valve 17 and a controller. The inlet of the switching valve 17 is connected to the vapor phase outlet of the steam-water separator 14. The three outlets of the switching valve 17 are respectively connected to the steam inlet of the condenser 2, the steam inlet of the low-pressure heater 4, and the steam inlet of the deaerator 5. The controller is electrically connected to the switching valve 17 and is used to selectively introduce the vapor phase medium into the condenser 2, the low-pressure heater 4, or the deaerator 5 according to the pressure of the vapor phase medium. By automatically controlling the opening and closing of the outlet of the switching valve 17 according to the pressure of the vapor phase medium, the selective introduction of the vapor phase medium into the condenser 2, the low-pressure heater 4, or the deaerator 5 according to the pressure level is realized. This ensures that the vapor phase medium can enter the regenerative equipment with a matching pressure level under different operating conditions, avoiding backflow or inability to connect due to pressure mismatch. At the same time, no manual intervention is required, improving the automation level and operational reliability of the system.

[0022] like Figure 1As shown, a return steam pressure regulating valve 15 and a check valve 16 are sequentially installed between the vapor phase outlet of the steam-water separator 14 and the switching valve 17. Based on the selection of the deaerator 5, low-pressure heater 4, or condenser 2 by the switching valve 17 according to the pressure level of the vapor phase medium, the return steam pressure regulating valve 15 can finely adjust the pressure of the vapor phase medium, eliminating pressure deviations caused by pipeline friction losses or operating condition fluctuations. This ensures a precise match between the pressure of the vapor phase medium and the working pressure of the introduced regenerative equipment, thereby guaranteeing a stable and efficient connection of the vapor phase medium. The check valve 16 prevents the steam introduced into the deaerator 5, low-pressure heater 4, or condenser 2 from flowing back into the heating channel of the steam-water separator 14 or the final stage stationary vane 13, avoiding interference from backflowing steam to the heat exchange process within the heating channel or causing equipment malfunctions, thus improving the operational safety and stability of the system.

[0023] like Figure 1 As shown, the extraction ports include the turbine's front-stage extraction port, the intermediate-pressure cylinder exhaust port, and the low-pressure cylinder's front-stage extraction port. By setting multiple extraction ports with different pressure levels, various pressure-level heat source access points are provided for the final-stage stator blade heating channel 13. The extraction steam with matching parameters can be selected to access the heating channel according to the actual operating conditions of the turbine, thus ensuring stable and suitable heating steam for stator blade heating under different load conditions and broadening the system's operating condition adaptability.

[0024] like Figure 1 As shown, the extraction steam port and the inlet of the heating channel are connected by an extraction steam switching valve 10. The extraction steam switching valve 10 is electrically connected to the controller. The controller is used to control the extraction steam switching valve 10 to select the corresponding extraction steam port according to the load of the turbine 1. When the load of the turbine 1 is higher than the preset threshold, the extraction steam port of the low-pressure cylinder of the turbine 1 is selected as the source of heating steam. When the load of the turbine 1 is lower than the preset threshold, the extraction steam port of the turbine 1 or the exhaust steam port of the intermediate-pressure cylinder is selected as the source of heating steam. The controller automatically controls the extraction steam switching valve 10 to select the extraction steam port with matching pressure level as the source of heating steam according to the load of turbine 1. When the load of turbine 1 is high, the extraction steam port of the low-pressure cylinder of turbine 1 is selected. When the load of turbine 1 is low, the extraction steam port of the low-pressure cylinder or the exhaust steam port of the intermediate-pressure cylinder is selected. This ensures that the pressure and temperature of the heating steam entering the stationary blade heating channel are within a suitable range under different load conditions. It avoids the problem of excessive thermal stress on the stationary blade due to excessive extraction steam parameters or insufficient heating effect due to excessive extraction steam parameters, thereby improving the load adaptability and operational reliability of the system.

[0025] like Figure 1As shown, a pressure-reducing valve 11 and a flow-regulating valve 12 are sequentially installed between the extraction steam switching valve 10 and the inlet of the heating channel. Based on the selection of the extraction steam port by the extraction steam switching valve 10, the pressure-reducing valve 11 can reduce the pressure of the heating steam entering the heating channel, so that its pressure matches the pressure-bearing capacity and heat exchange requirements of the heating channel of the stationary vane 13. The flow-regulating valve 12 can precisely control the flow rate of the heating steam, thereby realizing flexible adjustment of the heating temperature and heat exchange intensity of the stationary vane 13, avoiding excessive thermal stress or overheating of the stationary vane 13 due to excessive steam pressure or flow, and ensuring that the stationary vane 13 operates in a safe and efficient state.

[0026] like Figure 1 As shown, the liquid phase outlet of the steam-water separator 14 is connected to a condensate expansion container 19, and a condensate regulating valve 18 is installed at the liquid phase outlet of the steam-water separator 14. The condensate regulating valve 18 can control the flow rate of the liquid phase medium discharged from the steam-water separator 14, so that the liquid phase medium enters the condensate expansion container 19 smoothly, avoiding system pressure fluctuations or pipeline impacts caused by sudden discharge of the liquid phase medium; the condensate expansion container 19 can expand and depressurize the discharged liquid phase medium, separate and recover the secondary flash vapor in it, avoid heat loss caused by direct discharge of the liquid phase medium, and further improve the waste heat recovery efficiency of the system.

[0027] like Figure 1 As shown, the internal heating channels of the last-stage stationary blade 13 are either single-pass or multi-pass structures. A single-pass structure is simple and has low flow resistance, suitable for applications with sufficient heating steam flow and low temperature distribution requirements. A multi-pass structure allows for uniform distribution of heating steam within the stationary blade, improving the uniformity of the temperature field on the blade surface and preventing localized overheating or undercooling. Furthermore, it allows for the distribution of different flow rates of heating steam according to the moisture-proofing needs of different areas of the stationary blade, achieving differentiated heating. This reduces heating steam consumption and improves heating efficiency while ensuring dehumidification.

[0028] Working principle: Heating steam supply process: The steam extracted from the extraction port of turbine 1 serves as extraction steam source 9. After passing through extraction steam switching valve 10, pressure reducing regulating valve 11, and flow regulating valve 12, the steam enters the internal heating channel of the last stage stationary vane 13. Extraction steam switching valve 10 selects or cuts off the corresponding extraction steam source. Pressure reducing regulating valve 11 regulates the steam pressure from extraction steam source 9 to the allowable working pressure range of the internal heating channel of the last stage stationary vane 13. Flow regulating valve 12 regulates the flow rate of heating steam entering the last stage stationary vane 13. Through the cooperation of the above valves, the heating steam entering the last stage stationary vane 13 meets the pressure, temperature, and flow rate requirements for dehumidification of the stationary vane.

[0029] The heat exchange process of the final stage stationary blade is as follows: The heating steam, after being regulated by the flow regulating valve 12, enters the internal heating channel of the final stage stationary blade 13 and flows along the internal heating channel; during the flow, the heating steam transfers heat to the outer surface of the stationary blade through the metal wall of the final stage stationary blade 13, causing the temperature of the outer surface of the stationary blade to rise; after the droplets in the mainstream of wet steam are deposited on the outer surface of the stationary blade, they are evaporated or thinned by the heating effect of the stationary blade wall, and the formation and development of the water film on the surface of the stationary blade are inhibited, thereby reducing the probability of water film rupture, ejection and formation of secondary droplets; after the heating steam completes the heat exchange in the final stage stationary blade 13, it is discharged from the outlet of the final stage stationary blade 13 and enters the steam-water separator 14.

[0030] Steam-water separation process: The outlet medium discharged from the last stage stationary vane 13 enters the steam-water separator 14 and is separated into a vapor phase medium and a liquid phase medium; the vapor phase medium is discharged from the vapor phase outlet of the steam-water separator 14, and the liquid phase medium is discharged from the liquid phase outlet of the steam-water separator 14; by setting the steam-water separator 14 on the outlet side of the last stage stationary vane 13, the steam-water two-phase mixture is prevented from directly entering the low-pressure heater 4, deaerator 5 or other regenerative equipment, thereby reducing the risk of water hammer, liquid level fluctuation, heat exchange surface erosion and regenerative system disturbance.

[0031] Vapor phase waste heat recovery process: The vapor phase medium separated by the steam-water separator 14 selectively enters the deaerator 5, low-pressure heater 4, or condenser 2 after passing through the return steam pressure regulating valve 15, check valve 16, and switching valve 17; the return steam pressure regulating valve 15 adjusts the pressure of the vapor phase medium before entering the corresponding recovery equipment to match the working pressure of the target recovery location; the check valve 16 prevents steam, condensate, or other media from flowing back into the steam-water separator 14 and the internal heating channel of the last stage stationary vane 13 according to the pressure of the vapor phase medium; the controller selectively guides the vapor phase medium into the deaerator 5, low-pressure heater 4, or condenser 2 according to the pressure of the vapor phase medium. Heater 4 or condenser 2; when the vapor medium pressure is higher than the working pressure of deaerator 5, the controller controls the switching valve 17 to introduce it into deaerator 5, so that it can participate in the condensate heating and thermal deaeration process as supplementary heating steam for deaerator 5; when the vapor medium pressure is lower than the working pressure of deaerator 5 but higher than the working pressure of low-pressure heater 4, the controller controls the switching valve 17 to introduce it into low-pressure heater 4, so that it can be used as a supplementary heat source for heating condensate for low-pressure heater 4; when the vapor medium pressure is lower than the working pressure of low-pressure heater 4, the controller controls the switching valve 17 to introduce it into condenser 2.

[0032] Liquid phase hydrophobic recovery process: The liquid phase medium separated by the steam-water separator 14 enters the hydrophobic expansion tank 19 through the hydrophobic regulating valve 18; the hydrophobic regulating valve 18 regulates the discharge rate of the steam-water separator 14 and maintains the liquid level in the steam-water separator 14 within the allowable range; the liquid phase medium entering the hydrophobic expansion tank 19 undergoes expansion, flash evaporation or stabilization treatment in the hydrophobic expansion tank 19, and then enters the condenser hot well, condensate system or other hydrophobic recovery location.

[0033] The process under different loads and dehumidification requirements: The controller controls the extraction steam switching valve 10 to select the corresponding extraction steam port according to the turbine 1 load. When the turbine 1 load is higher than the preset threshold, i.e., full load operation or low dehumidification requirement of the last stage stationary blade 13, although there is wet steam flow in the low-pressure last stage area of ​​turbine 1, the degree of water film deposition on the stationary blade surface, the water film thickness, or the risk of water erosion of the downstream moving blades are within the allowable range. At this time, the heating intensity required for the last stage stationary blade 13 is low. The controller controls the extraction steam switching valve 10 to select the low-pressure cylinder front extraction steam port of turbine 1 as the heating steam source; this type of heating steam enters the internal heating channel of the last stage stationary blade 13 after being regulated by the pressure reducing valve 11 and the flow regulating valve 12, and moderately heats the last stage stationary blade 13. Under this operating condition, due to the low pressure of the heating steam source and the further reduction in pressure and temperature after heat exchange within the final stage stationary vane 13, the vapor phase outlet pressure of the steam-water separator 14 is insufficient to stably enter the deaerator 5, but is higher than the operating pressure of the low-pressure heater 4. The controller controls the switching valve 17 to guide the vapor phase medium separated by the steam-water separator 14 into the low-pressure heater 4. The vapor phase medium entering the low-pressure heater 4 serves as a supplementary heating steam source to heat the condensate, thereby replacing or reducing part of the conventional low-pressure extraction steam volume. The liquid phase medium separated by the steam-water separator 14 then enters the condensate expansion tank 19 via the condensate regulating valve 18.

[0034] When the turbine 1 load is below the preset threshold, i.e., during partial load operation or when the dehumidification requirement of the last-stage stationary blade 13 is high, the last-stage stationary blade 13 requires higher wall heating intensity due to changes in the steam flow state, exhaust humidity, water film thickness on the stationary blade surface, or downstream moving blade water erosion risk in the low-pressure last-stage region of turbine 1. The controller controls the extraction steam switching valve 10 to select either the front-stage extraction port or the intermediate-pressure cylinder exhaust port of turbine 1 as the heating steam source. This type of heating steam has a high pressure and temperature. After being adjusted to the allowable pressure range of the internal heating channel of the last-stage stationary blade 13 by the pressure reducing regulating valve 11, the flow rate is then adjusted by the flow regulating valve 12 and enters the internal heating channel of the last-stage stationary blade 13 to improve the heat transfer intensity of the stationary blade wall and enhance the effects of droplet evaporation, water film thinning, and secondary droplet suppression. Under this condition, because the heating steam source pressure is high, even if the heating steam undergoes a certain degree of cooling, pressure reduction, or partial condensation after heat exchange inside the last-stage stationary blade 13, the vapor phase outlet of the steam-water separator 14 still has a high pressure and a high enthalpy value. When the vapor phase outlet pressure of the steam-water separator 14 is higher than the working pressure of the deaerator 5, the controller controls the switching valve 17 to introduce the vapor phase medium separated by the steam-water separator 14 into the deaerator 5. The vapor phase medium entering the deaerator 5 serves as supplementary heating steam to participate in the condensate heating and thermal deaeration process, thereby recovering the residual heat of the heating steam of the last stage stationary vane 13 and compensating for some of the work capacity loss caused by extracting higher pressure steam for heating the last stage stationary vane 13. When the vapor phase outlet pressure of the steam-water separator 14 is lower than the working pressure of the low-pressure heater 4, or when the liquid level of the steam-water separator 14 is abnormal, the system enters a low-level recovery or safety bypass mode. At this time, the controller controls the switching valve 17 to introduce the vapor phase medium into the condenser 2 to prevent backflow, water hammer, or liquid level disturbance in the regenerative equipment. At the same time, the drain regulating valve 18 adjusts its opening according to the liquid level of the steam-water separator 14 to introduce the separated liquid phase medium into the drain expansion tank 19 to ensure the safe operation of the heating channels inside the steam-water separator 14 and the last stage stationary vane 13.

[0035] The turbine stator blade heating and dehumidification system coupled with waste heat recovery according to the present invention has the following other advantages: First, while achieving dehumidification, the present invention performs steam-water separation on the outlet medium after the final stage static blade heating is completed, and performs graded recovery according to the vapor phase pressure, temperature and the acceptance conditions of the regeneration system, so that the waste heat of the heating steam can re-participate in the condensate heating process, thereby reducing the loss of steam extraction work capacity and the decrease in overall thermal efficiency caused by heating and dehumidification.

[0036] Secondly, this invention couples the final stage stationary blade heating and dehumidification process with the turbine regenerative system, thereby improving the utilization rate of waste heat from the heating steam while ensuring the dehumidification effect of the stationary blades, and enhancing the system's operational safety, economy, and adaptability to different operating conditions.

[0037] Third, this invention establishes a tiered operation mode adapted to load, dehumidification requirements, and the state of the regenerating system: when the dehumidification requirement is low, lower pressure steam is used preferentially for stationary blade heating, and the vapor medium separated by the steam-water separator is recovered to the low-pressure heater; when the dehumidification requirement is high, higher pressure steam is used to increase the heating intensity of the stationary blades, and the vapor medium with higher pressure and higher enthalpy is preferentially recovered to the deaerator; when the regenerating system does not have the conditions to receive the vapor medium and the pressure of the vapor medium does not meet the requirements, the system switches to the condenser safety bypass, thereby balancing the stationary blade dehumidification effect, waste heat recovery efficiency, and the operational safety of the turbine regenerating system under different operating conditions.

[0038] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A turbine stator blade heating and dehumidification system coupled with waste heat recovery, comprising a turbine, a condenser, a low-pressure heater, and a deaerator connected in sequence, wherein a heating channel for heating steam is provided inside the last-stage stator blade of the turbine, the inlet of the heating channel is connected to the turbine's extraction port, and the extraction port is located in the upstream section of the last-stage stator blade, characterized in that, Also includes: The steam-water separator has its inlet connected to the outlet of the heating channel. The vapor phase outlet of the steam-water separator is connected to the steam inlet of the condenser, the steam inlet of the low-pressure heater, and the steam inlet of the deaerator, respectively. The steam-water separator is used to separate the outlet medium after heat exchange into a vapor phase medium and a liquid phase medium. The switching control unit, located at the vapor phase outlet of the steam-water separator, is used to selectively guide the vapor medium into the condenser, low-pressure heater, or deaerator based on its pressure. When the vapor medium pressure is higher than the deaerator's operating pressure, it is guided into the deaerator; when the vapor medium pressure is lower than the deaerator's operating pressure but higher than the low-pressure heater's operating pressure, it is guided into the low-pressure heater; and when the vapor medium pressure is lower than the low-pressure heater's operating pressure, it is guided into the condenser.

2. The turbine stator blade heating and dehumidification system with coupled waste heat recovery according to claim 1, characterized in that, The switching control unit includes: a switching valve, the inlet of which is connected to the vapor phase outlet of the steam-water separator, and three outlets which are respectively connected to the steam inlet of the condenser, the steam inlet of the low-pressure heater, and the steam inlet of the deaerator; and a controller, which is electrically connected to the switching valve and is used to selectively guide the vapor phase medium into the condenser, the low-pressure heater, or the deaerator according to the pressure of the vapor phase medium.

3. The turbine stator blade heating and dehumidification system with coupled waste heat recovery according to claim 2, characterized in that, A return steam pressure regulating valve and a check valve are sequentially installed between the vapor phase outlet of the steam-water separator and the switching valve.

4. The turbine stator blade heating and dehumidification system with coupled waste heat recovery according to claim 2, characterized in that, The extraction ports include the front-stage extraction port of the steam turbine, the intermediate-pressure cylinder exhaust port, and the front-stage extraction port of the low-pressure cylinder.

5. A turbine stator blade heating and dehumidification system with coupled waste heat recovery according to claim 4, characterized in that, The extraction port is connected to the inlet of the heating channel via an extraction steam switching valve. The extraction steam switching valve is electrically connected to a controller. The controller is used to control the extraction steam switching valve to select the corresponding extraction port according to the turbine load. When the turbine load is higher than a preset threshold, the extraction port of the low-pressure cylinder of the turbine is selected as the source of heating steam. When the turbine load is lower than the preset threshold, the extraction port of the turbine or the exhaust port of the intermediate-pressure cylinder is selected as the source of heating steam.

6. A turbine stator blade heating and dehumidification system coupled with waste heat recovery according to claim 5, characterized in that, A pressure reducing valve and a flow regulating valve are sequentially installed between the extraction steam switching valve and the inlet of the heating channel.

7. A turbine stator blade heating and dehumidification system with coupled waste heat recovery according to claim 1, characterized in that, The liquid phase outlet of the steam-water separator is connected to a hydrophobic expansion container, and the liquid phase outlet of the steam-water separator is equipped with a hydrophobic regulating valve.

8. A turbine stator blade heating and dehumidification system with coupled waste heat recovery according to claim 1, characterized in that, The internal heating channel of the last stage stationary blade has a single-channel or multi-channel structure.

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