A coal-fired unit rapid peak load regulation and frequency modulation system coupled with a high-temperature working medium regenerative system

Abstract

The utility model discloses a coal fired unit quick peak load regulation and frequency modulation system of high temperature working medium heat storage of heat recovery system coupling relates to conventional heating power electric technology and energy storage technical field, including coal fired unit thermodynamic cycle system and high temperature working medium heat storage system, wherein, high temperature working medium heat storage system and coal fired unit thermodynamic cycle heat recovery system carry out the deep coupling, through the mutual cooperation of reducing steam turbine each stage extraction steam amount and high temperature working medium heat storage system energy supply, realizes the quick combined peak load regulation and frequency modulation of unit. First, when the unit needs quick load, through reducing steam turbine each stage extraction steam amount, realizes the quick promotion of unit power output, at the same time, the high temperature, high pressure saturated water stored in high temperature working medium heat storage tank produces a certain amount of saturated steam through pressure reduction to replace the boiler feed water in steam turbine each stage extraction heating heat recovery system, thereby guaranteeing that the boiler feed water temperature still keeps unchangeable or has the improvement, and then realizes the quick promotion of coal fired unit variable load response ability.

Description

Technical Field

[0001] This utility model relates to the fields of coal-fired power generation technology and energy storage technology, and in particular to a rapid peak-shaving and frequency regulation system for coal-fired power units that couples a regenerative system with high-temperature working fluid heat storage. Background Technology

[0002] Guided by the "dual carbon" goals, the global energy transition is accelerating, and my country is committed to reducing carbon emissions and promoting low-carbon, green economic development. Against this backdrop, intermittent renewable energy sources such as wind and solar power have been developed and applied on a large scale, and are being integrated into the power grid in large quantities. However, the intermittent and unstable nature of these renewable energy sources poses numerous challenges to the safety and stability of the power system. For example, solar power generation is affected by sunlight intensity and weather conditions; on cloudy days, rainy days, or at night when sunlight is insufficient, power generation will drop significantly or even stop. Wind power generation depends on wind speed and its stability; sudden changes in wind speed can lead to drastic fluctuations in power generation. This uncertainty in power output makes it difficult to maintain the supply-demand balance of the power system, reduces voltage and frequency stability, and consequently affects the safe and stable operation of the power grid.

[0003] To address this issue, improving the load change response rate and tracking capability of existing coal-fired power generating units is particularly important. Coal-fired power generating units possess advantages such as large capacity, high stability, and strong dispatchability, and still occupy an important position in the power grid. Improving their load change capability can effectively compensate for the shortcomings of intermittent renewable energy generation, enhancing the flexibility and reliability of the power grid. Currently, existing technologies for peak-shaving and frequency regulation in coal-fired power unit peak-shaving and regenerative systems, such as the No. 0 high-pressure heater and condensate throttling, can meet some peak-shaving and frequency regulation needs to a certain extent, but they also have some limitations. The No. 0 high-pressure heater is mainly designed for deep peak-shaving conditions, and its applicability to other conditions is limited; while condensate throttling can quickly adjust the load, it leads to a decrease in feedwater temperature, thus affecting the unit's thermal efficiency, causing a drop in power generation, and may also have a certain impact on the equipment lifespan of the unit.

[0004] Therefore, in order to better meet the peak-shaving needs of the new power system and ensure the safe and stable operation of the power grid, it is necessary to propose new technological solutions suitable for rapid load changes in coal-fired power units. These new technologies should be able to significantly improve the load change response rate and tracking capability of coal-fired power units without affecting the unit's thermal efficiency and equipment lifespan, enabling them to better adapt to the intermittency and instability of new energy power generation, and providing strong support for achieving the energy transition under the "dual carbon" goal. Utility Model Content

[0005] The purpose of this invention is to improve the load regulation response characteristics of coal-fired power generating units in order to meet the urgent needs of new power systems for coal-fired power generating units in terms of peak shaving and frequency regulation performance.

[0006] To achieve the above objectives, this utility model provides a rapid peak-shaving and frequency regulation system for coal-fired power units with a regenerative system coupled with high-temperature working fluid heat storage, including a regenerative system, a boiler, a steam turbine, a condenser, and a condensate pump; the regenerative system, boiler, steam turbine, condenser, and condensate pump are connected by pipes and valves;

[0007] The steam turbine includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder; the steam turbine performs work to drive a generator to generate electricity.

[0008] The regenerative system includes a low-pressure heater, a deaerator, a feed water pump, a high-pressure heater, and a high-temperature working fluid heat storage system. The high-temperature working fluid heat storage system is coupled to the high-pressure heater, the deaerator, and the low-pressure heater.

[0009] The high-pressure heater is connected to the steam extraction outlet of the high-pressure cylinder or the intermediate-pressure cylinder; the deaerator is connected to the steam extraction outlet of the intermediate-pressure cylinder; the low-pressure heater is connected to the steam extraction outlet of the low-pressure cylinder or the intermediate-pressure cylinder.

[0010] The condenser outlet is equipped with a condensate pump, and the outlet of the condensate pump is connected to the regenerative system; the condensate pump outlet is divided into two paths, one leading to the low-pressure heater and the other leading to the high-temperature working fluid heat storage system.

[0011] The vapor-water mixture after pressure reduction by the pressure regulating valve in the high-temperature working fluid heat storage system is connected to the vapor inlet pipe of the high-pressure heater after separation by the steam-water separator. The liquid-phase high-temperature working fluid outlet pipe after separation by the steam-water separator is connected to the deaerator.

[0012] Preferably, the high-temperature working fluid heat storage system includes a high-temperature working fluid heat storage device and its accessories, a pressure reducing valve, and a steam-water separator;

[0013] The deaerator is connected to a high-pressure heater and a low-pressure heater, and its outlet is equipped with a water pump.

[0014] The inlet of the high-temperature working fluid heat storage device is connected to the condensate pump through a water supply branch, which is used to fill a certain amount of working fluid into the high-temperature working fluid heat storage device for storage.

[0015] The outlet of the high-temperature working fluid heat storage device is connected in sequence to a pressure reducing valve and a steam-water separator.

[0016] The gas phase outlet of the gas-water separator is connected to the high-pressure heater, and the liquid phase outlet is connected to the deaerator.

[0017] Another aspect of this invention provides a method for rapid peak shaving and frequency regulation of a power unit by coupling a regenerative system with high-temperature working fluid heat storage. Regulating valves are installed on the extraction steam pipelines of the high-pressure and low-pressure heaters in the regenerative system of a coal-fired power unit, and the high-temperature working fluid heat storage system is organically integrated into the regenerative system. By precisely controlling the regulating valves, the turbine extraction steam flow rate is rapidly adjusted, thereby enabling flexible control of the power generation frequency and power of the coal-fired power unit. Simultaneously, the heat storage device continuously supplies high-temperature steam and high-temperature water to the heat exchanger (high-pressure heater) of the regenerative system, effectively maintaining the stability of the feedwater temperature, thereby enhancing the frequency regulation capability of the coal-fired power unit.

[0018] This invention also provides a rapid peak-shaving and frequency regulation method for coal-fired power units with a regenerative system coupled with high-temperature working fluid heat storage. When the high-temperature working fluid heat storage system is in heat release mode, the regulating valve of the high-temperature heater extraction steam pipeline is closed or reduced, causing the extracted steam to return to the high-pressure cylinder or intermediate-pressure cylinder to do work. At the same time, the pressure reducing valve of the outlet pipeline of the high-temperature working fluid heat storage device is opened, so that the high-temperature and high-pressure saturated steam in the high-temperature working fluid heat storage device is depressurized to a state matching the original high-pressure heater extraction steam pressure. The depressurized saturated steam is converted into a gas-liquid two-phase flow and enters the steam-water separator for separation. The water vapor at the gas phase outlet of the steam-water separator replaces the original high-pressure heater extraction steam and is transported to the high-pressure heater heat flow inlet to exchange heat with the feedwater. The water at the liquid phase outlet of the steam-water separator is transported to the deaerator to heat the feedwater. In addition, due to the increase in the working fluid flow rate in the deaerator, the feedwater flow rate in the low-pressure heater feedwater pipeline is reduced accordingly, resulting in a corresponding reduction in the extraction steam flow rate of the intermediate-pressure cylinder or low-pressure cylinder. This portion of the saved extraction steam flows back to the intermediate-pressure cylinder or low-pressure cylinder for additional power conversion, thereby increasing the power generation capacity.

[0019] When the high-temperature working fluid thermal storage system is in thermal storage mode, the output power of the coal-fired unit can be reduced by any one or more of the following three methods:

[0020] (1) Indirect heating method using main steam or high-pressure extraction steam: Open the main steam or high-pressure cylinder extraction steam valve, and high-temperature and high-pressure main steam enters from the heat source inlet and flows through the heat exchange tube bundle (various forms of heat exchange tube bundles such as serpentine tube bundle / horizontal tube bundle / vertical tube bundle / coil tube) set in the high-temperature working medium heat storage device. The working medium stored in the high-temperature working medium heat storage device is heated and pressurized to the design value through indirect heat exchange. The steam after heat exchange can be sent to the heating outlet.

[0021] (2) Main steam direct heating method: Open the main steam bypass valve, and the high temperature and high pressure main steam enters the high temperature working medium heat storage device from the heat source inlet. The working medium stored in the high temperature working medium heat storage device is heated and pressurized to the design value through direct mixing heat exchange.

[0022] (3) Electric heating method: Turn on the circuit switch and use part of the electrical energy output by the coal-fired generator to heat the working medium stored in the high-temperature working medium heat storage device, so that its temperature and pressure are increased to the design value (reducing the power output of the system).

[0023] When the high-temperature working fluid heat storage system is in isolation and insulation mode, the high-temperature working fluid heat storage device neither stores nor releases heat. The feedwater branch valve and the outlet pressure reducing valve are closed, putting the high-temperature working fluid heat storage system into an isolation state. Simultaneously, based on changes in temperature and pressure within the high-temperature working fluid heat storage device, the heating source is replenished promptly to ensure the working fluid remains within a stable temperature and pressure range. Similarly, the steam heat storage device neither stores nor releases heat. The heat source inlet and outlet pipelines are closed, and the feedwater branch valve and the outlet pressure reducing valve are also closed, putting the steam heat storage system into an isolation state.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. A high-temperature working fluid heat storage device is embedded in the regenerative system of the coal-fired unit. In the heat release mode, the high-temperature and high-pressure water working fluid stored in the device directly enters the regenerative system of the unit, which indirectly increases the steam flow rate for doing work in the turbine, thereby achieving the effect of increasing the unit's ramp-up rate and solving the problem of reduced steam extraction from the turbine and lower boiler inlet feedwater temperature.

[0026] 2. In the thermal storage mode, this utility model can store the high-parameter steam heat of the unit or convert the power generation into thermal energy for storage, thereby reducing the output power of the unit and benefiting the decoupling of heat and electricity and maintaining the economic operation of the coal-fired unit under deep peak shaving conditions.

[0027] 3. This utility model has a simple structure, is easy to operate, has low energy loss in the heat storage stage, and has low cost for retrofitting existing equipment. It can improve the peak-shaving capacity of coal-fired power generating units under variable load conditions.

[0028] The following will further explain the concept, specific structure and technical effects of this utility model in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of this utility model. Attached Figure Description

[0029] Figure 1 This is a system structure diagram of a preferred embodiment of the present invention.

[0030] In the picture:

[0031] 1. Boiler;

[0032] 2. High-pressure cylinder;

[0033] 3. Intermediate pressure cylinder;

[0034] 4. Low-pressure cylinder;

[0035] 5. Generator;

[0036] 6. Valves;

[0037] 7. Condenser;

[0038] 8. Condensate pump;

[0039] 9. Low-pressure heater;

[0040] 10. Deaerator;

[0041] 11. Water supply pump;

[0042] 12. High-pressure heater;

[0043] 13. Steam-water separator;

[0044] 14. Pressure regulating valve;

[0045] 15. High-temperature working fluid heat storage device;

[0046] 16. Heat source inlet;

[0047] 17. Heating outlet;

[0048] 18. Main steam bypass valve;

[0049] 19. High-pressure cylinder steam extraction valve. Detailed Implementation

[0050] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0051] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and this invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0052] like Figure 1 As shown, this embodiment provides a rapid peak-shaving and frequency regulation system for coal-fired power units with a regenerative system coupled with high-temperature working fluid heat storage, including a regenerative system, a boiler 1, a steam turbine, a condenser 7, and a condensate pump 8; the regenerative system, boiler 1, steam turbine, condenser 7, and condensate pump 8 are connected by pipes and valves;

[0053] The steam turbine includes a high-pressure cylinder 2, an intermediate-pressure cylinder 3, and a low-pressure cylinder 4; the steam turbine drives a generator 5 to generate electricity.

[0054] The regenerative system includes a low-pressure heater 9, a deaerator 10, a feed water pump 11, a high-pressure heater 12, and a high-temperature working fluid heat storage system. The high-temperature working fluid heat storage system is coupled to the high-pressure heater 12, the deaerator 10, and the low-pressure heater 9.

[0055] The high-pressure heater 12 is connected to the steam extraction outlet of the high-pressure cylinder 2 or the intermediate-pressure cylinder 3; the deaerator 10 is connected to the steam extraction outlet of the intermediate-pressure cylinder 4; the low-pressure heater 9 is connected to the steam extraction outlet of the low-pressure cylinder 3 or the intermediate-pressure cylinder 4.

[0056] The condenser 7 outlet is equipped with a condensate pump 8, and the outlet of the condensate pump 8 is connected to the regenerative system; the outlet of the condensate pump 8 is divided into two paths, one leading to the low-pressure heater 9 and the other leading to the high-temperature working fluid heat storage system.

[0057] The gas phase outlet of the high-temperature working fluid heat storage system is connected to the inlet of the high-pressure heater 12, and the liquid phase outlet of the high-temperature working heat storage system is connected to the deaerator 10.

[0058] The high-temperature working fluid heat storage system includes a high-temperature working fluid heat storage device 15, a pressure reducing valve 14, and a steam-water separator 13.

[0059] The deaerator 10 is connected to the high-pressure heater 12 and the low-pressure heater 9, and its outlet is equipped with a water pump 11.

[0060] The inlet of the high-temperature working fluid heat storage device 15 is connected to the condensate pump 8 through a water supply branch, which is used to fill a certain amount of working fluid into the high-temperature working fluid heat storage device 15 for storage.

[0061] The outlet of the high-temperature working fluid heat storage device 15 is connected in sequence to the pressure reducing valve 14 and the steam-water separator 13; the high-temperature working fluid heat storage device 15 also includes a heat source inlet 16 and a heating outlet 17.

[0062] The gas phase outlet of the gas-water separator 13 is connected to the high-pressure heater 12, and the liquid phase outlet is connected to the deaerator 10.

[0063] All connected pipes are equipped with valves 6 to regulate the steam extraction flow rate.

[0064] This invention provides a method for rapid peak shaving and frequency regulation of a power unit by coupling a regenerative system with high-temperature working fluid heat storage. Regulating valves are installed on the extraction steam pipelines of the high-pressure and low-pressure heaters in the regenerative system of a coal-fired power unit, and the high-temperature working fluid heat storage system is organically integrated into the regenerative system. By precisely controlling the regulating valves, the turbine extraction steam flow rate is rapidly adjusted, thereby enabling flexible regulation of the power generation frequency and power of the coal-fired power unit. Simultaneously, the heat storage device continuously supplies high-temperature steam and high-temperature water to the heat exchanger of the regenerative system, effectively maintaining the stability of the feedwater temperature, thus enhancing the frequency regulation capability of the coal-fired power unit.

[0065] Based on the balance between power supply and demand, this utility model discloses a rapid peak-shaving and frequency regulation method for a unit with a regenerative system coupled with high-temperature working fluid heat storage. This method has three operating modes: heat release mode, heat storage mode, and isolation / insulation mode. These are illustrated through the following three embodiments. This utility model can be embodied in many different embodiments, and its scope of protection is not limited to the embodiments mentioned herein.

[0066] Example 1 (Energy Release Mode)

[0067] When the high-temperature working fluid heat storage system is in heat release mode, the regulating valve 6 of the extraction steam pipeline of the high-temperature heater 12 is closed or reduced, causing the extracted steam to return to the high-pressure cylinder 2 and the intermediate-pressure cylinder 3 to perform work. Simultaneously, the pressure reducing valve 14 of the outlet pipeline of the high-temperature working fluid heat storage device 15 is opened, allowing the high-temperature, high-pressure saturated steam in the high-temperature working fluid heat storage device 15 to be depressurized to match the original high-pressure heater extraction steam pressure. The depressurized saturated steam is converted into a gas-liquid two-phase flow and enters the steam-liquid separator 13 for steam-liquid separation. The water vapor at the vapor phase outlet of the steam-liquid separator 13 replaces the original high-pressure heater extraction steam and is transported to the heat inlet of the high-pressure heater 12 to exchange heat with the feedwater; the water at the liquid phase outlet of the steam-liquid separator 13 is transported to the deaerator 10 to heat the feedwater. Furthermore, due to the increase in the working fluid flow rate in the deaerator 10, the feedwater flow rate in the feedwater pipeline of the low-pressure heater 9 decreases accordingly, resulting in a corresponding reduction in the extraction steam flow rate of the intermediate-pressure cylinder 3 and the low-pressure cylinder 4. The saved steam is returned to the intermediate-pressure cylinder 3 and low-pressure cylinder 4 for additional power conversion, thereby further increasing the unit's power generation capacity.

[0068] This embodiment is applicable to the rapid load change conditions and cold / hot start-up conditions of coal-fired power generation boilers. When the unit is in the load increase condition, high-temperature steam and high-temperature water can be directly and quickly provided to the regenerative circulation system through the high-temperature working fluid heat storage device. This effectively solves the problem of insufficient steam output caused by the large thermal inertia and heat transfer lag of the boiler system when the unit is rapidly ramping up, and at the same time helps to maintain the economic efficiency of the unit operation.

[0069] Example 2 (Energy Storage Mode)

[0070] When the high-temperature working fluid heat storage system is in heat storage mode, the following three methods can be used to reduce the output power of the coal-fired unit.

[0071] (1) Indirect heating by main steam or high-pressure extraction steam: Open the main steam bypass valve 18 or the high-pressure cylinder extraction steam valve 19, and high-temperature and high-pressure steam enters the high-temperature working medium heat storage device from the heat source inlet 16. It flows through the heat exchange tube bundle (various forms of heat exchange tube bundles such as serpentine tube bundle / horizontal tube bundle / vertical tube bundle / coil) set in the high-temperature working medium heat storage device, and raises the temperature and pressure of the working medium stored in the high-temperature working medium heat storage device to the design value through indirect heat exchange. The steam after heat exchange can be sent to the heating outlet 17.

[0072] (2) Direct heating of main steam: Open the main steam bypass valve 18, and the high temperature and high pressure main steam enters the high temperature working medium heat storage device from the heat source inlet 16. The working medium stored in the high temperature working medium heat storage device 15 is heated and pressurized to the design value through direct mixing heat exchange.

[0073] (3) Electric heating: Use part of the electrical energy output from the generator 5 of the coal-fired unit to heat the working medium stored in the high-temperature working medium heat storage device 15, so that its temperature and pressure are increased to the design value.

[0074] Since the high-temperature working fluid heat storage device 15 stores a high-enthalpy working fluid (high temperature and high pressure), it is necessary to carry out the charging-releasing process of the high-temperature working fluid heat storage device 15 regularly according to the unit load operation to ensure that the high-temperature working fluid heat storage device 15 is always in a usable state and at a high temperature level, so that the unit boiler can have the ability to respond quickly to load changes at any time.

[0075] Coal-fired power units often experience poor boiler operation under low-load conditions (<50% Pe, especially 20-30% Pe), leading to inefficient unit performance. Storing the heat energy generated during high-load boiler operation or the electrical energy generated by the generator as heat energy facilitates thermoelectric decoupling while maintaining the economic efficiency of the coal-fired unit. In this embodiment, a 600MW supercritical unit is used as an example. This unit operates under a rapid load change at a constant 5% Pe / min rate within the 20%-100% load range, with the high-temperature working fluid heat storage device (15) having a volume of approximately 50-150 m³. 3 The working fluid parameters are 17MPa and 350℃.

[0076] Example 3 (Isolation and Insulation Mode)

[0077] When the high-temperature working fluid heat storage system is in isolation mode or insulation mode, the high-temperature working fluid heat storage device neither stores nor releases heat. The water supply branch valve and the outlet pressure reducing valve are closed to put the high-temperature working fluid heat storage system into isolation mode. At the same time, according to the temperature and pressure changes in the high-temperature working fluid heat storage device, the heating source is replenished in a timely manner to ensure that the working fluid in the high-temperature working fluid heat storage device is within a certain temperature and pressure range.

[0078] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A rapid peak-shaving and frequency regulation system for coal-fired power units with a regenerative system coupled with high-temperature working fluid heat storage, characterized in that, It includes a regenerative system, a boiler, a steam turbine, a condenser, and a condensate pump; the regenerative system, boiler, steam turbine, condenser, and condensate pump are connected by pipes and valves; The steam turbine includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder; the steam turbine performs work to drive a generator to generate electricity. The regenerative system includes a low-pressure heater, a deaerator, a feed water pump, a high-pressure heater, and a high-temperature working fluid heat storage system. The high-temperature working fluid heat storage system is coupled to the high-pressure heater, the deaerator, and the low-pressure heater. The high-pressure heater is connected to the steam extraction outlet of the high-pressure cylinder or the intermediate-pressure cylinder; the deaerator is connected to the steam extraction outlet of the intermediate-pressure cylinder; the low-pressure heater is connected to the steam extraction outlet of the low-pressure cylinder or the intermediate-pressure cylinder. The condenser outlet is equipped with a condensate pump, and the outlet of the condensate pump is connected to the regenerative system; the condensate pump outlet is divided into two paths, one leading to the low-pressure heater and the other leading to the high-temperature working fluid heat storage system. The vapor-water mixture after pressure reduction by the pressure regulating valve in the gas phase steam outlet pipeline of the high-temperature working fluid heat storage system is separated by the steam-water separator and then connected to the steam inlet pipeline of the high-pressure heater. The liquid phase high-temperature working fluid outlet pipeline after separation by the steam-water separator is connected to the deaerator. The high-temperature working fluid heat storage system includes a high-temperature working fluid heat storage device and its accessories, a steam-water separator, and a pressure reducing valve. The deaerator is connected to a high-pressure heater and a low-pressure heater, and its outlet is equipped with a water pump. The inlet of the high-temperature working fluid heat storage device is connected to the condensate pump through a water supply branch, which is used to fill a certain amount of working fluid into the high-temperature working fluid heat storage device for storage. The outlet of the high-temperature working fluid heat storage device is connected in sequence to a pressure reducing valve, a steam-water separator, and a regulating valve. The gas phase outlet of the gas-water separator is connected to the high-pressure heater, and the liquid phase outlet is connected to the deaerator.

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