Rapid and flexible peak-shaving boiler water working medium circulating system with energy storage bypass circulation and rapid and flexible peak-shaving boiler water working medium circulating method

Abstract

The invention discloses a rapid and flexible peak regulation boiler water working medium circulating system and method with energy storage bypass circulation, and relates to the technical field of boiler water working medium circulation.The rapid and flexible peak regulation boiler water working medium circulating system comprises a steam pocket, a heat storage tank, a descending pipe, a circulating water pump, a hearth water cooling wall, a first valve and a second valve, the heat storage tank is communicated with an inlet of a circulating water pump through a pipeline via a second valve, an outlet of the circulating water pump is communicated with a downcomer, the downcomer is communicated with a hearth water-cooled wall, the hearth water-cooled wall and the steam pocket form a circulation loop, and an economizer, a superheater and a water feeding pump can be selectively arranged. The method comprises an energy charging step and an energy releasing step, the high-enthalpy-value working medium in the steam pocket is stored in the heat storage tank during energy charging, and the high-enthalpy-value working medium in the heat storage tank is conveyed to the hearth water wall circulating system during energy releasing. Storage and quick release of the high-enthalpy working medium are achieved through bypass circulation, the enthalpy value of the working medium at the inlet of the boiler and the steam yield rate are directly increased, and the variable load response capacity of the boiler is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of boiler water working medium circulation, in particular to a fast and flexible peak-shaving boiler water working medium circulation system with energy storage bypass circulation and a method thereof, which is suitable for coal power peak-shaving scenarios in a new power system with high renewable energy ratio under the "double carbon" target, can significantly improve the variable load response rate of the boiler, and meets the demand of the power grid for flexible peak-shaving. BACKGROUND

[0002] Now, under the guidance of the "double carbon" target, the energy structure transformation in China is accelerating, and the installed capacity of renewable energy such as wind power and photovoltaic power is growing rapidly. Gradually building a new power system with high renewable energy ratio has become an inevitable trend in the future development of the power industry. However, renewable energy such as wind power and photovoltaic power is significantly affected by natural conditions and has inherent intermittency, volatility and unpredictability. After large-scale grid connection, it will bring serious challenges to the safe and stable operation of the power grid, making it more difficult to balance supply and demand. To solve this problem, power sources with flexible adjustment capacity are needed as support, and coal power, as an important base power source of China's power system, is changing its role from traditional base load power to flexible peak-shaving power, which requires coal power to have a higher variable load response rate to quickly respond to the power supply and demand imbalance caused by renewable energy output fluctuations.

[0003] At present, the variable load response rate of coal-fired boilers in China is generally low, with an average variable load response rate of only 1.0%Pe / min~2.5%Pe / min (rated load / minute), which is far from meeting the demand of the new power system for flexible peak-shaving. In-depth analysis of the reasons shows that the inherent defects in the heat transfer characteristics of the boiler itself are the main cause: there is a significant rate difference between the fuel combustion heat release process in the boiler and the heat absorption process of the working medium in the boiler. Specifically, the residence time of coal powder in the furnace is extremely short, only about 1 second, and the fuel combustion heat release process is rapid and intense, which can quickly release a large amount of heat. However, the heat absorption process of the working medium (mainly water and steam) in the boiler has a large delay, and the working medium needs to complete heat exchange in the furnace water wall and other heating surfaces to realize the state change from water to saturated steam and then to superheated steam. This delay causes the heat generated in the furnace to be unable to be absorbed and utilized by the working medium in time, resulting in a heat transfer lag in the furnace. This heat transfer lag directly limits the variable load response capacity of the boiler. When the power grid needs the boiler to quickly increase the load, the working medium cannot absorb the combustion heat and convert it into steam in time, which slows down the steam production rate and affects the variable load response rate of the entire unit.

[0004] In the prior art, in order to improve the boiler variable load response rate, relevant technical personnel has tried various improvement schemes, such as optimizing the combustion system, increasing the circulating water pump power, improving the heating surface structure and the like, but these schemes cannot fundamentally solve the core problem of heat transfer lag in the furnace. Although the optimization of the combustion system can improve the combustion efficiency, it cannot change the inherent characteristics of the heat absorption delay of the working medium; the increase of the circulating water pump power can only speed up the flow speed of the working medium, and has limited effect on the enthalpy increase of the working medium, and will cause the increase of energy consumption; the improvement of the heating surface structure faces the problems of high cost and great difficulty in transformation, and is difficult to be popularized and applied on a large scale in the existing coal-fired generating units.

[0005] Therefore, it has become a technical problem to be solved in the field to develop a boiler water working medium circulating system which is simple in structure, reliable in operation, controllable in cost and can fundamentally solve the problem of heat transfer lag. SUMMARY

[0006] In view of the above defects of the prior art, the technical problem to be solved by the present application is that the existing coal-fired boiler has a rate difference between the heat release of fuel combustion in the furnace and the heat absorption of the working medium in the furnace, which causes heat transfer lag in the furnace, and further limits the variable load response rate of the boiler, and cannot meet the demand of the new power system for coal-fired flexible peak regulation under the "double carbon" target.

[0007] To achieve the above-mentioned purpose, the present application provides a fast and flexible peak regulation boiler water working medium circulating system with energy storage bypass circulation, which comprises a steam drum, a heat storage tank, a downcomer, a circulating water pump, a furnace water cooling wall, a valve one and a valve two; the steam drum is communicated with the inlet of the heat storage tank through a first pipeline and the valve one, the outlet of the heat storage tank is communicated with the inlet of the circulating water pump through a second pipeline and the valve two, the outlet of the circulating water pump is communicated with one end of the downcomer, the other end of the downcomer is communicated with the inlet of the furnace water cooling wall, the outlet of the furnace water cooling wall is communicated with the steam drum, forming a working medium circulating main loop; the heat storage tank and the first pipeline and the second pipeline constitute an energy storage bypass circulation branch.

[0008] Preferably, the system further comprises an economizer, the outlet of the economizer is communicated with the inlet of the steam drum through a third pipeline, for preheating the feed water entering the steam drum. As a tail heating surface of the boiler, the economizer can absorb the waste heat in the flue gas of the boiler, preheat the feed water to a certain temperature before sending it into the steam drum, which not only improves the thermal efficiency of the boiler, but also reduces the heating load of the working medium in the steam drum, and provides favorable conditions for the generation of high-enthalpy working medium.

[0009] Preferably, the system further comprises a feed water pump, an outlet of the feed water pump being communicated with an inlet of the economizer through a fourth pipeline for stably conveying feed water to the economizer. The feed water pump adopts constant pressure frequency conversion control, can adjust the output flow and pressure according to the feed water demand of the economizer, ensures the stability and continuity of the feed water conveying, and provides guarantee for the stable operation of the whole water working medium circulating system.

[0010] Preferably, the system further comprises a superheater, an inlet of the superheater being communicated with a steam outlet of the steam drum through a fifth pipeline for superheating the steam output by the steam drum to improve the steam parameters. The superheater can heat the saturated steam generated by the steam drum to a superheated state, improve the enthalpy value and work capacity of the steam, meet the requirements of the steam parameters of the steam turbine, and further improve the operation efficiency of the unit.

[0011] Preferably, the heat storage tank is a high-temperature and high-pressure resistant sealing structure, and an inner wall of the heat storage tank is provided with a heat preservation layer for maintaining the stability of the enthalpy value of the stored working medium. The material of the heat storage tank is selected from high-temperature and high-pressure resistant alloy steel, which can withstand the high-temperature and high-pressure action of the working medium output by the steam drum, and avoid leakage or structural damage. The heat preservation layer arranged on the inner wall is made of high-temperature ceramic fiber material, has excellent heat preservation performance, can effectively reduce the heat loss of the working medium in the heat storage tank, and ensure that the enthalpy value of the working medium remains stable in the standby energy storage state, thereby laying a foundation for subsequent rapid energy release.

[0012] The present application also provides a fast and flexible peak shaving boiler water working medium circulating method with energy storage bypass circulation.

[0013] The energy charging step: when the boiler is in a high load operation state, valve one is opened and valve two is closed, so that the high-enthalpy working medium in the steam drum is injected into the heat storage tank through the first pipeline. After the heat storage tank is filled with the working medium, valve one is closed, and the heat storage tank enters a standby energy storage state.

[0014] The energy releasing step: when the boiler needs to be rapidly upgraded, valve two is opened, the high-enthalpy working medium stored in the heat storage tank enters the circulating water pump through the second pipeline, is pressurized by the circulating water pump, is then conveyed to the downcomer, and finally enters the furnace water wall from the downcomer to participate in the heat absorption and steam generation process of the working medium circulating main loop.

[0015] Preferably, in the energy charging step, the high-enthalpy working medium in the steam drum is saturated working medium, and the natural flow of the working medium is realized through the pressure difference between the steam drum and the heat storage tank during the injection process, without the need for additional power transmission devices. When the boiler is in a high load operation state, the working medium in the steam drum is in a high-temperature and high-pressure state, while the heat storage tank is in a normal pressure or low pressure state before energy charging. The pressure difference between the two provides a natural power for the flow of the working medium, which not only simplifies the system structure, but also reduces the energy consumption.

[0016] Preferably, in the energy releasing step, the operating frequency of the circulating water pump is adjusted according to the boiler load increase demand to control the delivery rate of the high-enthalpy working medium, so that the boiler steam production rate matches the load increase demand. When the load increase demand is large, the operating frequency of the circulating water pump is increased to increase the delivery rate of the high-enthalpy working medium, so that the overall enthalpy of the working medium in the water-cooled wall of the furnace is quickly increased. When the load increase demand is small, the operating frequency of the circulating water pump is reduced to reduce the delivery rate of the working medium, so that the steam production rate is not too high to cause fluctuations in the power grid, and accurate regulation and control of the variable load response is achieved.

[0017] Preferably, before the energy charging step, the heat storage tank needs to be pretreated to discharge the residual gas in the heat storage tank, so that the injected high-enthalpy working medium is free of impurities and the enthalpy of the working medium is stable. The pretreatment process is realized by a vent valve arranged at the bottom of the heat storage tank. When the vent valve discharges pure working medium (without air bubbles), the vent valve is closed and the valve is opened for energy charging, effectively avoiding the mixing of gas which may reduce the enthalpy of the working medium or affect the stable operation of the circulating system.

[0018] Preferably, in the energy releasing step, the high-enthalpy working medium cooperates with the heat generated by the fuel burning in the furnace after entering the water-cooled wall of the furnace, so that the heat absorption delay time of the working medium is shortened and the variable load response rate of the boiler is quickly increased. The high-enthalpy working medium released by the heat storage tank itself has a high energy level. After entering the water-cooled wall of the furnace, it can quickly absorb the heat generated by the burning of the fuel in the furnace, without going through the long heat absorption process from low-temperature water to saturated water, thereby significantly shortening the heat absorption delay time of the working medium, so that the boiler can quickly increase the steam production rate and thus the variable load response rate.

[0019] The present application stores the high-enthalpy working medium generated in the steam drum during high-load operation of the boiler through the energy storage bypass circulation branch. Compared with the prior art, the present application has the following technical effects:

[0020] (1) The present application stores the high-enthalpy working medium in the heat storage tank and directly injects the high-enthalpy working medium into the water-cooled wall circulation system of the furnace during energy release, avoiding the delay process of heat absorption from low-temperature state, quickly increasing the enthalpy of the working medium at the inlet of the boiler and the steam production rate, effectively alleviating the heat transfer lag problem in the furnace, greatly improving the variable load response rate of the boiler, and meeting the demand of new power systems for flexible peak shaving of coal-fired power plants.

[0021] (2) The energy storage bypass circulation branch of the present application is only composed of a steam pocket, a heat storage tank, a pipeline and a valve, and can be realized by modifying the existing boiler water working medium circulation system without large-scale modification of the main structure of the boiler, so the modification difficulty is low and the cost is controllable; meanwhile, the charging and discharging can be realized by only adjusting the opening and closing of the valve and the rotating speed of the circulating water pump during the operation of the system, so the operation is simple, the fault points are few and the operation reliability is high.

[0022] (3) The high-enthalpy working medium stored in the present application comes from the excess working medium in the steam pocket during the high load operation of the boiler, so the high-enthalpy working medium does not need to be generated by consuming additional energy, and the energy recycling is realized; the natural flow of the working medium is realized by using the pressure difference between the steam pocket and the heat storage tank during the charging process, so additional power devices do not need to be additionally added, the system energy consumption is further reduced, and the overall energy utilization rate is improved.

[0023] (4) The present application is not only suitable for newly-built coal-fired boilers, but also can be widely applied to the flexibility modification of existing coal-fired boilers, without changing the core components such as the combustion system and the heating surface structure of the boiler, so the modification compatibility is strong; meanwhile, the capacity of the heat storage tank, the pipeline specification and the valve type can be flexibly adjusted according to the parameters and peak shaving demand of different boilers, so the coal-fired boilers with different capacities and different parameters can be adapted, and the application range is extremely wide.

[0024] The concept, specific structure and generated technical effects of the present application will be further described below in combination with the drawings, so as to fully understand the purpose, features and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structural schematic diagram of the quick and flexible peak shaving boiler water working medium circulation system with energy storage bypass circulation of the present application.

[0026] In the figure: 1, steam pocket; 2, heat storage tank; 3, downcomer; 4, circulating water pump; 5, valve one; 6, valve two; 7, furnace water wall; 8, economizer; 9, superheater; 10, feed water pump. DETAILED DESCRIPTION

[0027] The following reference description of the drawings introduces several preferred embodiments of the present application, so that the technical content of the present application is clearer and easier to understand. The present application can be embodied in many different forms of embodiments, and the protection scope of the present application is not limited to the embodiments mentioned in the text.

[0028] In the drawings, the same numbers are used to represent the same components throughout the drawings, and the components with similar structures or functions are represented by similar numbers. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present application does not limit the size and thickness of each component. In order to make the drawing clearer, the thickness of some components is appropriately exaggerated in some places in the drawing.

[0029] Example 1

[0030] This embodiment provides a fast and flexible peak-shaving boiler water circulation system with energy storage bypass circulation, the structure of which is as follows: Figure 1 As shown, it includes a steam drum 1, a heat storage tank 2, a downcomer 3, a circulating water pump 4, a furnace water-cooled wall 7, valve 1 5, and valve 2 6.

[0031] Among them, the steam drum 1 is the core pressure-bearing component of the boiler, which is used to contain the working fluid and separate water and steam. Its material is Q345R low alloy high strength steel. The design pressure and temperature are adapted to the rated operating parameters of the boiler, and it can operate stably under high temperature and high pressure conditions to ensure the production of high enthalpy saturated working fluid that meets the requirements.

[0032] The heat storage tank 2 is a high-temperature and high-pressure resistant sealed structure, made of high-temperature and high-pressure resistant alloy steel. Its capacity is determined according to the rated load and peak-shaving requirements of the boiler, and it can store a sufficient amount of high-enthalpy working fluid to meet the needs of rapid load increase. The inner wall of the heat storage tank 2 is equipped with a heat insulation layer, which is made of high-temperature resistant ceramic fiber material with a thickness of 50mm~80mm. This can effectively reduce the heat loss of the working fluid and maintain the stability of the working fluid's enthalpy.

[0033] Both valve 5 and valve 6 are high-temperature and high-pressure shut-off valves made of chromium-molybdenum-vanadium steel, with excellent sealing performance. They can withstand the high temperature and high pressure of the working fluid output from steam drum 1, ensuring no leakage when closed and meeting the flow requirements of the working fluid when open. Circulating water pump 4 is a horizontal centrifugal pump, characterized by large flow rate, stable head, and reliable operation. Its material and sealing structure are adapted to the parameter requirements of high-enthalpy working fluids, enabling it to stably deliver the working fluid released from heat storage tank 2 to downcomer 3.

[0034] The specific connection relationships of each component are as follows: the bottom outlet pipe (first pipe) of the steam drum 1 is connected to the inlet flange of valve 5, and the outlet flange of valve 5 is connected to the top inlet of the thermal storage tank 2 through a pipe, realizing the connection between the steam drum 1 and the thermal storage tank 2; the bottom outlet of the thermal storage tank 2 is connected to the inlet flange of valve 6 through a pipe, and the outlet flange of valve 6 is connected to the inlet flange of the circulating water pump 4 through a pipe, realizing the connection between the thermal storage tank 2 and the circulating water pump 4; the outlet flange of the circulating water pump 4 is welded to one end of the downcomer 3, and the other end of the downcomer 3 is welded to the inlet header of the furnace water-cooled wall 7; the outlet header of the furnace water-cooled wall 7 is welded to the top inlet of the steam drum 1 through a riser pipe, forming the main loop of the working fluid circulation; the thermal storage tank 2, together with the first pipe (the pipe from the steam drum 1 to the thermal storage tank 2) and the second pipe (the pipe from the thermal storage tank 2 to the circulating water pump 4), constitute the energy storage bypass circulation branch.

[0035] During the assembly process of the system in this embodiment, it is necessary to ensure the sealing and strength of each pipe connection. All welded joints adopt the welding process of argon arc welding for the root and manual electric arc welding for the cover. After welding, non-destructive testing (UT+RT) is performed to ensure that there are no welding defects. Before installation, valve 5 and valve 6 need to undergo pressure test and sealing test. The test pressure is 1.5 times the rated working pressure to ensure that the valves do not leak under the rated parameters. When installing the circulating water pump 4, it is necessary to align it to ensure that the coaxiality error between the pump shaft and the motor shaft meets the requirements to avoid vibration and noise during operation.

[0036] The system works as follows: During normal boiler operation, the working fluid flows in the main working fluid circulation loop. The furnace water-cooled wall 7 absorbs the heat generated by fuel combustion in the furnace, heating the working fluid to saturation before it is delivered to the steam drum 1. After steam-water separation is completed in the steam drum 1, the steam is delivered to subsequent equipment, while the water re-enters the furnace water-cooled wall 7 through the downcomer 3 for recirculation and heating. When the boiler is operating at high load, a high enthalpy working fluid is stored through the energy storage bypass circulation branch during the energy charging process. When a rapid load increase is required, the stored high enthalpy working fluid is injected into the main loop through the energy storage bypass circulation branch during the energy release process, thereby increasing the steam production rate.

[0037] Example 2

[0038] Based on Example 1, this embodiment adds an economizer 8, and the outlet of the economizer 8 is connected to the inlet of the steam drum 1 through a third pipe.

[0039] Economizer 8 is a horizontal, bare-tube economizer located in the boiler tail flue. It absorbs waste heat from the boiler exhaust. It is made of 20G boiler steel, and the number and length of the tubes are determined based on the boiler exhaust temperature and feedwater flow rate. The third pipeline is made of seamless steel pipe, with the same material as economizer 8. The outlet header of economizer 8 is welded to one end of the third pipeline, and the other end of the third pipeline is connected to the feedwater inlet flange of steam drum 1. The connection is sealed with asbestos gaskets to ensure no leakage.

[0040] In this embodiment, the feedwater first enters the economizer 8, where it absorbs waste heat from the flue gas and is preheated to a certain temperature before being sent to the steam drum 1 through a third pipe. Compared with Embodiment 1, this embodiment, by adding the economizer 8, not only improves the boiler's thermal efficiency and reduces flue gas heat loss, but also reduces the heating load of the working fluid in the steam drum 1, enabling the steam drum 1 to generate a high-enthalpy working fluid more quickly, providing a more sufficient source of working fluid for the charging process of the energy storage bypass circulation branch. At the same time, the preheated feedwater entering the steam drum 1 reduces the thermal stress within the steam drum 1, extending its service life.

[0041] Example 3

[0042] Based on Example 2, this embodiment adds a water supply pump 10, and the outlet of the water supply pump 10 is connected to the inlet of the economizer 8 through a fourth pipe.

[0043] Feedwater pump 10 is a multi-stage centrifugal feedwater pump, characterized by high pressure, stable flow, and good regulation performance. Its rated flow and head are determined based on the boiler's rated evaporation capacity and feedwater pressure requirements. It is made of chromium-molybdenum steel and uses a mechanical seal to ensure stable operation under high temperature and high pressure conditions. The fourth pipeline is made of seamless steel pipe, with the same material as the outlet pipe of feedwater pump 10. The outlet flange of feedwater pump 10 is connected to one end of the fourth pipeline, and the other end of the fourth pipeline is welded to the inlet header of economizer 8. Anti-vibration pads are installed at the connection points to reduce the impact of vibrations generated by feedwater pump 10 during operation on the pipeline.

[0044] The feedwater pump 10 is equipped with a variable frequency control system, which can adjust the operating frequency in real time according to the feedwater demand of the economizer 8, thereby regulating the feedwater flow and pressure. When the boiler load changes, the variable frequency control system automatically adjusts the output parameters of the feedwater pump 10 based on the water level signal of the steam drum 1 and the inlet pressure signal of the economizer 8, ensuring that the feedwater flow and pressure delivered to the economizer 8 are stable, avoiding problems such as abnormal water level in the steam drum 1 or dry burning of the economizer 8 due to feedwater fluctuations, and providing a reliable guarantee for the stable operation of the entire circulation system.

[0045] Example 4

[0046] Based on Example 1, this embodiment adds a superheater 9, and the inlet of the superheater 9 is connected to the steam outlet of the steam drum 1 through a fifth pipe.

[0047] Superheater 9 adopts a combined structure of screen-type superheater and convection superheater, arranged in the upper part of the furnace and in the horizontal flue. It can fully absorb the radiant heat of the furnace and the convective heat of the flue gas. Its material is heat-resistant alloy steel, which can withstand the corrosion and oxidation of high-temperature steam. The fifth pipe is made of seamless steel pipe, and the material is the same as that of the inlet pipe of superheater 9. The steam outlet flange of steam drum 1 is connected to one end of the fifth pipe, and the other end of the fifth pipe is welded to the inlet header of superheater 9. The connection is sealed with a high-temperature resistant gasket.

[0048] In this embodiment, the saturated steam separated from the steam drum 1 enters the superheater 9 through the fifth pipe. In the superheater 9, it is further heated to a superheated state, increasing its enthalpy and work capacity before being delivered to the steam turbine for power generation. By adding the superheater 9, not only are the steam turbine's steam parameter requirements met, improving the unit's power generation efficiency, but it also works synergistically with the energy storage bypass circulation branch: when the energy storage bypass circulation branch releases energy to increase steam yield, the superheater 9 can simultaneously increase the steam temperature, ensuring stable output steam parameters and preventing a decrease in steam temperature due to a rapid increase in steam yield, further improving the stability of the unit during variable load operation.

[0049] Example 5

[0050] Based on Example 1, this embodiment provides a detailed description of the heat storage tank 2, which is a high-temperature and high-pressure resistant sealed structure with an insulation layer on its inner wall.

[0051] The thermal storage tank 2 has a cylindrical structure with a diameter of 2m-3m and a height of 5m-8m. The wall thickness is determined based on design pressure and temperature calculations. It is made of SA387Gr11 heat-resistant alloy steel, capable of withstanding a pressure of 17MPa and a temperature of 350℃. The top of the thermal storage tank 2 is equipped with an inlet pipe, a safety valve interface, and a pressure gauge interface, while the bottom is equipped with an outlet pipe and a vent valve interface. The safety valve interface is fitted with a spring-loaded safety valve with a set pressure of 1.05 times the design pressure, ensuring timely pressure relief in case of overpressure and guaranteeing equipment safety. The pressure gauge interface is equipped with a shock-resistant pressure gauge for real-time monitoring of the pressure inside the thermal storage tank 2.

[0052] The inner wall of the thermal storage tank 2 is equipped with an insulation layer made of high-temperature resistant ceramic fiber material. This material features high temperature resistance, low thermal conductivity, good insulation performance, and strong chemical stability, enabling it to operate stably for extended periods in high-temperature environments above 350℃. The construction process for the insulation layer is as follows: First, a high-temperature adhesive is applied to the inner wall of the thermal storage tank 2. Then, ceramic fiber blankets are laid in layers on the tank wall, each layer being 20mm~30mm thick, for a total thickness of 50mm~80mm. During the laying process, it is ensured that the insulation layer is tightly fitted to the tank wall without gaps. Finally, a layer of stainless steel wire mesh is laid on the inner surface of the insulation layer to fix it in place and prevent it from falling off when the working fluid flows.

[0053] In this embodiment, the heat storage tank 2, through its high-temperature and high-pressure resistant structural design and efficient insulation layer, can reliably store the high-enthalpy working fluid (17MPa, 350℃) output from the steam drum 1, and effectively reduce the heat loss of the working fluid. This ensures that the enthalpy of the working fluid remains at a high level during standby energy storage, providing a reliable guarantee for subsequent rapid energy release and improving the boiler's response rate to load changes.

[0054] Example 6

[0055] This embodiment provides a rapid and flexible peak-shaving boiler water working fluid circulation method with energy storage bypass circulation, applied to the system described in Embodiment 1. The method includes an energy charging step and an energy releasing step, as detailed below:

[0056] Charging Procedure: When the boiler is operating at high load, the working fluid in steam drum 1 has reached a high-temperature, high-pressure saturated state (pressure 17MPa, temperature 350℃), exhibiting high enthalpy characteristics. The operator issues a charging command through the control system. The control system opens valve 5 and keeps valve 6 closed. Under the pressure difference between steam drum 1 and heat storage tank 2, the high-enthalpy saturated working fluid in steam drum 1 is continuously injected into heat storage tank 2 through the first pipeline (the pipeline from steam drum 1 to heat storage tank 2). During the charging process, the pressure inside the tank is monitored in real time using a pressure gauge at the top of heat storage tank 2. When the pressure reaches the same level as the pressure in steam drum 1, and the level gauge at the bottom of heat storage tank 2 indicates that the working fluid is full, the charging is complete. The control system then closes valve 5, and heat storage tank 2 enters a standby energy storage state, awaiting the energy release command.

[0057] Energy Release Procedure: When the power grid issues a load increase command and the boiler needs to rapidly increase its load, the operator issues an energy release command through the control system. The control system then opens valve 26, allowing the high-enthalpy saturated working medium (pressure 17MPa, temperature 350℃) stored in the thermal storage tank 2 to enter the circulating water pump 4 through the second pipeline (the pipeline from the thermal storage tank 2 to the circulating water pump 4) under its own pressure and the suction of the circulating water pump 4. The circulating water pump 4 starts operating, pressurizing the high-enthalpy working medium and delivering it to the downcomer 3. During its flow within the downcomer 3, the working medium mixes with the existing circulating working medium in the downcomer 3, and then both enter the inlet header of the furnace water-cooled wall 7. The mixed working medium (high-enthalpy working medium + existing circulating working medium) entering the furnace water-cooled wall 7 absorbs the heat generated by fuel combustion in the furnace. Due to the high initial enthalpy of the mixed working medium, it can quickly reach saturation and convert into steam, thereby rapidly increasing the boiler's steam production rate, achieving rapid load increase, and improving the load change response rate.

[0058] When the working fluid in the thermal storage tank 2 is completely released (as monitored by the level gauge), or when the boiler load reaches the target value, the control system controls valve 6 to close, the circulating water pump 4 to stop running, the energy release step is completed, and the boiler resumes normal working fluid circulation main circuit operation; if the boiler subsequently enters a high-load operation state again, the above energy charging steps can be repeated to achieve the cycle operation of energy storage and energy release.

[0059] The method in this embodiment stores a high-enthalpy working fluid through an energy-charging step and rapidly releases the high-enthalpy working fluid through an energy-releasing step, directly increasing the initial enthalpy of the working fluid in the furnace water-cooled wall 7, shortening the heat absorption delay time of the working fluid, effectively solving the problem of heat transfer lag in the furnace, and significantly improving the boiler's variable load response rate.

[0060] Example 7

[0061] Based on Example 6, this embodiment further optimizes the charging steps. During the charging process, the pressure difference between the steam drum 1 and the heat storage tank 2 is used to achieve the natural flow of the working fluid, without the need for additional power supply devices.

[0062] Before charging, the thermal storage tank 2 is at atmospheric pressure (close to atmospheric pressure), while the pressure inside the steam drum 1 is 17 MPa during high-load boiler operation, creating a significant pressure difference. When valve 5 is opened and valve 6 is closed, the high-enthalpy working fluid in the steam drum 1 automatically flows into the thermal storage tank 2 driven by the pressure difference, eliminating the need for additional pumps or other power devices. During charging, as the amount of working fluid in the thermal storage tank 2 increases, the pressure inside gradually rises, the pressure difference between the tank and the steam drum 1 gradually decreases, and the flow rate of the working fluid slows down. When the pressure inside the thermal storage tank 2 equals the pressure inside the steam drum 1, the flow of the working fluid stops, indicating that the thermal storage tank 2 is full and charging is complete.

[0063] The method in this embodiment utilizes pressure difference to achieve natural flow of the working fluid, which not only simplifies the system structure and reduces equipment investment and operating energy consumption, but also reduces the risk of failure and improves the reliability and stability of the charging process. At the same time, the pressure difference-driven flow mode can ensure that the working fluid is injected smoothly into the heat storage tank 2, avoiding loss of working fluid enthalpy or impact vibration in the heat storage tank 2 due to excessive flow rate.

[0064] Example 8

[0065] Based on Example 6, this embodiment further optimizes the energy release step. The circulating water pump 4 adopts frequency conversion control, which adjusts the operating frequency according to the load increase requirements of the boiler, thereby controlling the delivery rate of the high enthalpy working fluid.

[0066] The circulating water pump 4 is equipped with a variable frequency controller, which is connected to the boiler's load control system and can receive real-time load increase demand signals from the boiler (such as load increase rate, target load, etc.). When the boiler needs to rapidly and significantly increase its load, the load control system sends a high-frequency command to the variable frequency controller, which increases the operating frequency of the circulating water pump 4, increases the pump's output flow rate and head, and accelerates the delivery rate of the high-enthalpy working fluid, allowing a large amount of high-enthalpy working fluid to quickly enter the furnace water-cooled wall 7, rapidly increasing the steam yield and meeting the rapid load increase demand. When the boiler needs to slowly and gradually increase its load, the load control system sends a low-frequency command to the variable frequency controller, which reduces the operating frequency of the circulating water pump 4, decreases the working fluid delivery rate, ensures a stable increase in steam yield, and avoids grid frequency and voltage instability caused by fluctuations in steam yield.

[0067] The method in this embodiment achieves precise control of the high enthalpy working fluid delivery rate through frequency conversion regulation, so that the boiler's steam output rate is precisely matched with the load increase demand. This ensures both the effect of rapid peak shaving and the stability of unit operation, and improves the flexibility and adaptability of the entire system.

[0068] Example 9

[0069] Based on Example 6, this embodiment adds a pretreatment step of the heat storage tank 2 before the charging step to ensure the purity and enthalpy stability of the injected working fluid.

[0070] The pretreatment steps are as follows: Before opening valve 5 for charging, first open the vent valve at the bottom of the thermal storage tank 2. The vent valve is connected to the atmosphere and is used to discharge residual gases (such as air, nitrogen, etc.) inside the thermal storage tank 2. After opening the vent valve, the residual gases inside the thermal storage tank 2 are discharged under atmospheric pressure. After 3-5 minutes of continuous discharge, close the vent valve to complete the pretreatment. If there is a large amount of residual gas or impurities in the thermal storage tank 2, the above venting process can be repeated 2-3 times to ensure that the residual gases inside the tank are completely discharged.

[0071] The purpose of the pretreatment step is to prevent residual gas from mixing into the high-enthalpy working fluid, which would reduce the enthalpy of the working fluid (the enthalpy of the gas is much lower than that of the saturated working fluid) and affect the peak-shaving effect during energy release. At the same time, the presence of residual gas may cause gas resistance in the heat storage tank 2, affecting the flow stability of the working fluid, and may even cause pipeline vibration due to gas expansion during energy release. Pretreatment can effectively avoid the above problems and ensure the stability and reliability of the charging and releasing process.

[0072] Example 10

[0073] Based on Example 6, this embodiment details the synergistic mechanism between the high enthalpy working fluid and the combustion heat in the furnace during the energy release step.

[0074] In the energy release step, the high-enthalpy working fluid (17MPa, 350℃) released from the heat storage tank 2 enters the furnace water-cooled wall 7 and synergistically interacts with the heat generated by fuel combustion in the furnace. Specifically, under normal operating conditions, the working fluid in the furnace water-cooled wall 7 is low-temperature feedwater (its temperature is still far below the saturation temperature after preheating by the economizer 8), which needs to absorb a large amount of heat to reach saturation and be converted into steam. This process leads to a delay in the heat absorption of the working fluid. However, in this embodiment, the high-enthalpy working fluid is already saturated and has a high enthalpy value. After entering the furnace water-cooled wall 7, it does not need to undergo a long heat absorption process in the low-temperature stage. It can quickly absorb the combustion heat in the furnace and directly convert it into superheated steam, or synergistically interact with the combustion heat in the furnace to accelerate the vaporization process of the working fluid in the entire water-cooled wall.

[0075] Meanwhile, the injection of a high-enthalpy working fluid increases the flow rate and heat capacity of the working fluid within the furnace water-cooled wall 7, enabling the working fluid to more fully absorb the combustion heat within the furnace, reducing heat loss, and further improving heat utilization efficiency. This synergistic effect significantly shortens the working fluid heat absorption delay time, allowing the boiler's steam yield to increase rapidly in a short period of time, thereby greatly improving the boiler's variable load response rate and effectively solving the problem of insufficient peak-shaving capacity caused by heat transfer hysteresis in existing technologies.

[0076] The preferred embodiments of the present invention 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 the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention 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 and flexible peak-shaving boiler water circulation system with energy storage bypass circulation, characterized in that, This includes the steam drum, thermal storage tank, downcomer, circulating water pump, furnace water-cooled wall, valve one, and valve two; The steam drum is connected to the inlet of the thermal storage tank via a first pipe and a valve. The outlet of the thermal storage tank is connected to the inlet of the circulating water pump via a second pipe and a valve. The outlet of the circulating water pump is connected to one end of the downcomer, and the other end of the downcomer is connected to the inlet of the furnace water-cooled wall. The outlet of the furnace water-cooled wall is connected to the steam drum, forming the main working fluid circulation loop. The thermal storage tank, the first pipe, and the second pipe constitute an energy storage bypass circulation branch.

2. The system as described in claim 1, characterized in that, It also includes an economizer, the outlet of which is connected to the inlet of the steam drum via a third pipe, for preheating the feedwater entering the steam drum.

3. The system as described in claim 2, characterized in that, It also includes a water pump, the outlet of which is connected to the inlet of the economizer via a fourth pipe, for stably supplying water to the economizer.

4. The system as described in claim 1, characterized in that, It also includes a superheater, the inlet of which is connected to the steam outlet of the steam drum via a fifth pipe, for superheating the steam output from the steam drum to improve the steam parameters.

5. The system as described in claim 1, characterized in that, The heat storage tank has a high-temperature and high-pressure resistant sealed structure, and the inner wall of the heat storage tank is provided with a heat insulation layer to maintain the stability of the enthalpy value of the stored working fluid.

6. A rapid and flexible peak-shaving boiler water circulation method with energy storage bypass circulation, applied to the rapid and flexible peak-shaving boiler water circulation system with energy storage bypass circulation as described in any one of claims 1-5, characterized in that, Includes the energy charging step and the energy releasing step: Charging steps: When the boiler is operating at high load, open valve one and close valve two to allow the high enthalpy working fluid in the steam drum to be injected into the heat storage tank through the first pipeline. After the heat storage tank is full of working fluid, close valve one and the heat storage tank enters the standby energy storage state. Energy release steps: When the boiler needs to rapidly increase the load, valve two is opened, and the high enthalpy working fluid stored in the heat storage tank enters the circulating water pump through the second pipeline. After being pressurized by the circulating water pump, it is transported to the downcomer and then enters the furnace water-cooled wall through the downcomer to participate in the heat absorption and steam generation process of the main working fluid circulation loop.

7. The method as described in claim 6, characterized in that, In the charging step, the high-enthalpy working fluid in the steam drum is a saturated working fluid. During the injection into the heat storage tank, the working fluid flows naturally through the pressure difference between the steam drum and the heat storage tank, without the need for additional power supply devices.

8. The method as described in claim 6, characterized in that, In the energy release step, the operating frequency of the circulating water pump is adjusted according to the boiler's load increase demand to control the delivery rate of the high-enthalpy working fluid, so that the boiler steam production rate matches the load increase demand.

9. The method as described in claim 6, characterized in that, Before the charging step, the heat storage tank needs to be pretreated to remove residual gas and ensure that the injected high-enthalpy working fluid is free of impurities and maintains a stable enthalpy value.

10. The method as described in claim 6, characterized in that, In the energy release step, after the high-enthalpy working fluid enters the water-cooled wall of the furnace, it works synergistically with the heat generated by the combustion of fuel in the furnace to shorten the heat absorption delay time of the working fluid and rapidly improve the boiler's variable load response rate.

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