Variable load peak regulation system of circulating fluidized bed boiler

Abstract

The invention provides a circulating fluidized bed boiler variable load peak regulation system which comprises a hearth used for heating a first part of water fed into the system through combustion heat release of first fuel to generate water vapor, and an ash and smoke mixture at a first temperature is generated after the first fuel is combusted; the combustion heating device is used for receiving the second fuel and part of the ash residues with the first temperature separated from the ash residue and flue gas mixture in the load reduction stage and generating a gas-solid mixture with the second temperature through a combustion exothermic reaction between the part of the ash residues with the first temperature and the second fuel, and the gas-solid mixture comprises circulating flue gas and circulating ash particles; and the heat storage tank is used for storing circulating ash particles at the second temperature obtained after gas-solid separation of the gas-solid mixture in the load reduction stage.

Description

Technical Field

[0001] This disclosure relates to the fields of boiler deep flexible peak shaving technology and heat storage and release technology, specifically to a circulating fluidized bed boiler variable load peak shaving system. Background Technology

[0002] Circulating fluidized bed (CFB) boilers are widely used in the power industry due to their advantages such as wide fuel adaptability, strong low-load stable combustion capability, and low cost of pollutant emission control. Driven by the "dual carbon" goal, the new power system is accelerating its restructuring, requiring coal-fired power plants to assume more flexible power supply responsibilities. However, due to the inherent structural flow characteristics of CFB boilers, the large amount of circulating ash and strong thermal inertia result in slow load change rates and lengthy start-up times. This makes it difficult to match the grid's demand for rapid peak shaving after the large-scale integration of renewable energy, thus limiting the absorption capacity of renewable energy. Currently, on the combustion side, CFB boilers mainly adjust their load change rate by adjusting fuel particle size or replacing with high-quality fuel. Although some technologies have improved the load increase rate of CFB boilers to some extent, overall, the load response rate of CFB units is still severely insufficient when facing the high demands of the grid for rapid peak shaving after the large-scale integration of renewable energy. This is especially true under extreme operating conditions or sudden load changes, where the response delay problem is more prominent, failing to meet the needs of rapid grid load changes in a timely manner and limiting its ability to coordinate with new energy sources in the new power system.

[0003] In some coal-fired power units, thermal storage is used to enhance the load regulation capability of the boiler unit. In the field of thermal storage technology, the mainstream sensible heat storage methods are mainly divided into molten salt thermal storage and solid thermal storage, but both have significant drawbacks. Molten salt thermal storage suffers from high material costs, low and narrow storage temperatures, and low storage density. It also has problems such as easy decomposition and corrosion at high temperatures and easy solidification at low temperatures leading to system blockage, seriously affecting operational reliability and economy. Solid thermal storage technology often uses magnesia brick fixed-bed heat exchange, with air or nitrogen as the heat transfer medium. This method suffers from low heat exchange efficiency, large equipment footprint, and high initial investment costs, all of which make it difficult to meet the thermal storage and flexible peak-shaving requirements of large circulating fluidized bed boiler units.

[0004] In summary, the existing circulating fluidized bed boilers' flexible peak-shaving capability and the performance defects of thermal storage technology create a dual constraint, urgently requiring a thermal storage and release technology and flexible peak-shaving solution that can adapt to the characteristics of circulating fluidized bed boilers and balance low cost and high efficiency. Summary of the Invention

[0005] In view of the above problems, this disclosure provides a variable load peak-shaving system for a circulating fluidized bed boiler, comprising:

[0006] The furnace is used to heat a first portion of water fed into the system to generate steam by releasing heat through the combustion of a first fuel, wherein the combustion of the first fuel generates an ash-slag-flue gas mixture at a first temperature;

[0007] A combustion heating device is used to receive a second fuel and a portion of ash at a first temperature separated from the ash-slag flue gas mixture during a load reduction phase, and to generate a gas-solid mixture at a second temperature through an exothermic combustion reaction between the portion of the first temperature ash and the second fuel. The gas-solid mixture includes circulating flue gas and circulating ash particles.

[0008] A thermal storage tank is used to store circulating ash particles at a second temperature obtained after gas-solid separation of a gas-solid mixture during the load reduction phase.

[0009] According to embodiments of this disclosure, during the load increase phase, in order to increase the system's thermal load, the circulating ash particles in the heat release tank need to reach a higher temperature, such as 900-1000°C, in order to obtain ultra-high temperature steam in the heat release tank. Since the ash residue after combustion in the furnace can generally only reach 700-800°C, directly storing it and then releasing the heat will not meet the requirement of heating water to obtain ultra-high temperature steam (≥540°C). Therefore, during the load decrease phase, fuel is added to the combustion heating device to further increase the temperature of the ash residue and obtain circulating ash particles at 900-1000°C.

[0010] The purpose of the above system is to provide a high-temperature solid particle heat storage and release device, and a fast and flexible peak-shaving system coupled with a circulating fluidized bed boiler unit, so as to realize the fast and flexible peak-shaving of the circulating fluidized bed boiler unit, while having the advantages of low heat storage cost, high efficiency, reliable operation, and fast adjustment and flexible peak-shaving.

[0011] Specifically: 1) Low-cost and reliable heat storage medium: Using high-temperature circulating ash solid particles from a circulating fluidized bed boiler as the heat storage medium eliminates the need for additional procurement of specialized heat storage materials, achieving zero cost for heat storage materials. Furthermore, the circulating ash exhibits stable chemical properties and high operational reliability. 2) Precise and controllable ultra-high temperature heat storage: Employing a two-stage heating mode, the first stage heats the circulating ash solid particles to 700-900℃ through the chemical heat of coal combustion in the furnace. The second stage further heats the circulating ash solid particles to 900-1000℃ through the combustion of a small amount of coal in the combustion heating chamber. No complex additional heating devices are required, and the heat storage temperature can be flexibly adjusted to meet ultra-high temperature heat storage requirements. 3) Two-stage rapid peak shaving in circulating fluidized bed boilers: During load reduction, stored circulating ash lowers the ash concentration in the circulating loop to achieve rapid load reduction. During load increase, recycled circulating ash enhances heat transfer on the combustion side, while high-temperature steam generated by the heat release tank is sent to the main steam pipeline to regulate the steam-water side, achieving flexible peak shaving on both the combustion and steam-water sides. Its load adjustment rate can reach the level of pulverized coal boilers or even gas-fired boilers, contributing to the large-scale consumption of renewable energy. 5) Compared to general solid thermal energy storage technologies such as molten salt thermal energy storage, it offers lower costs, higher and wider storage temperatures, and lower system operation and maintenance costs. Compared to general solid fixed-bed thermal energy storage, it boasts higher heat exchange efficiency, smaller footprint, and lower investment costs. In summary, the system exhibits significant advantages in multiple aspects, bringing new technological breakthroughs to the field of thermal energy storage and conversion, and possesses broad application prospects and economic value. Attached Figure Description

[0012] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0013] Figure 1 A schematic diagram of a variable load peak-shaving system for a circulating fluidized bed boiler according to a first embodiment of the present disclosure is shown.

[0014] Figure 2 A schematic diagram of a circulating fluidized bed boiler variable load peak-shaving system according to a second embodiment of the present disclosure is shown.

[0015] Figure 3 A schematic diagram of a variable load peak-shaving system for a circulating fluidized bed boiler according to a third embodiment of the present disclosure is shown.

[0016] Figure 4 A schematic diagram of a variable load peak-shaving system for a circulating fluidized bed boiler according to a fourth embodiment of the present disclosure is shown.

[0017] Figure 5 A schematic diagram of a circulating fluidized bed boiler variable load peak shaving system according to a fifth embodiment of the present disclosure is shown.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1. Furnace; 11. Secondary air duct; 2. Combustion heating device; 21. Combustion chamber; 211. Ash inlet; 212. Fuel inlet; 22. Conveying chamber; 23. Fuel bin; 3. Heat storage tank; 4. Heat release tank; 41. Evaporation chamber; 42. Superheating chamber; 43. Feeding chamber; 44. Return material inclined pipe; 51. First separator; 52. Second separator; 6. Return material device; 61. Return material riser; 62. Discharge pipe; 63. Return material leg; 7. Denitrification device; 8. Tail flue; 81. Air preheater; 9. Mechanical regulating valve; a. Fluidizing air; b. First fuel; c. Second fuel; d. Steam. Detailed Implementation

[0020] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0022] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0023] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0024] The embodiments of this disclosure provide a variable load peak-shaving system for a circulating fluidized bed boiler. Figure 1 A schematic diagram of a circulating fluidized bed boiler variable load peak shaving system according to a first embodiment of the present disclosure is shown.

[0025] like Figure 1As shown, the circulating fluidized bed boiler variable load peak shaving system includes a furnace 1, a combustion heating device 2, and a heat storage tank 3.

[0026] Furnace 1 is used to heat a first portion of water fed into the system to generate steam d by the heat released from the combustion of the first fuel b, wherein the combustion of the first fuel b generates an ash-slag-flue gas mixture at a first temperature;

[0027] Combustion heating device 2 is used to receive second fuel c and a portion of ash at a first temperature separated from the ash-slag flue gas mixture during the load reduction phase, and generate a gas-solid mixture at a second temperature through a combustion exothermic reaction between the portion of the first temperature ash and the second fuel c. The gas-solid mixture includes circulating flue gas and circulating ash particles.

[0028] The heat storage tank 3 is used to store circulating ash particles at a second temperature obtained after gas-solid separation of the gas-solid mixture during the load reduction phase.

[0029] According to embodiments of this disclosure, the ash and slag in the furnace 1 are further heated to a high temperature and the heat is stored during the load reduction phase by means of the combustion heating device 2 and the heat storage tank 3.

[0030] To achieve load increase and peak shaving, according to embodiments of this disclosure, the system further includes a heat release tank 4, which, during the load increase phase, uses the heat from the circulating ash particles at a second temperature to heat a second portion of water fed into the system to obtain superheated steam d, thereby increasing the system's heat load in a first manner. The circulating ash particles at the second temperature release heat to generate circulating ash particles at a third temperature, and the circulating solid particles at the third temperature are sent back to the furnace 1 to increase the system's heat load in a second manner.

[0031] According to embodiments of this disclosure, the numerical range of the first temperature is 700-900℃; the numerical range of the second temperature is 900-1000℃; and the numerical range of the third temperature is 300-400℃.

[0032] The system may also include a fuel supply device, consisting of a fuel feed pipe (connected to the fuel inlet 212 of the combustion heating device 2), a fuel tank 23, and regulating valves, to provide a second fuel c for the combustion heating device 2.

[0033] The above system is used for peak shaving in circulating fluidized bed (CFB) boilers. It consists of conventional components such as furnace 1, separator, return feeder 6, and tail flue 8. The components work together to realize functions such as feeding, heating, separating, storing heat, releasing heat, and returning high-temperature circulating ash solid particles.

[0034] Among them, the first fuel b and the second fuel c can be solid fuels such as coal, biomass, coal slime, and sludge, or they can be gaseous fuels.

[0035] Furthermore, the inlet and outlet pipes of the heat storage tank 3 can be equipped with mechanical regulating valves 9 to control the storage and release rate of high-temperature ash solid particles. The bottom is connected to the top of the heat release tank 4 through a connecting pipe to form a heat storage and release material channel.

[0036] According to embodiments of this disclosure, the water in the water supply system may include two parts. A water-cooled wall is provided in the furnace 1. The first part of the water in the supply system is fed into the water-cooled wall to generate high-temperature steam d by utilizing the heat released from the combustion of fuel in the furnace 1. The second part of the water in the supply system is fed into the heat release tank 4 to generate high-temperature steam d by utilizing the heat from the high-temperature circulating ash particles during the heat release stage. Therefore, during the load adjustment phase, the load adjustment is manifested in two aspects. On the one hand, the heat of the circulating ash particles at a second temperature of 900-1000℃ is used in the heat release tank 4 to heat the second part of the water fed into the system to obtain superheated steam d, thereby increasing the system heat load in the first way. On the other hand, the circulating ash particles at a lower temperature of 300-400℃ after the high-temperature circulating ash particles are cooled down are sent back to the furnace 1 to increase the ash concentration in the furnace 1, thereby increasing the heat load of the furnace 1. The furnace 1 is equipped with water-cooled walls to heat the first part of the water fed into the system to generate high-temperature steam d. Therefore, the cooled circulating solid particles are sent back to the furnace 1 to increase the system heat load in the second way.

[0037] According to the embodiments of this disclosure, in order to increase the system's heat load during the load-increasing phase, the circulating ash particles in the heat release tank 4 need to reach a higher temperature, such as 900-1000°C, in order to obtain ultra-high temperature steam d in the heat release tank 4. Since the ash residue after combustion in the furnace 1 can generally only reach 700-800°C, directly storing it and then releasing the heat will not meet the requirement of heating water to obtain ultra-high temperature steam d. Therefore, during the load-reducing phase, fuel is added to the combustion heating device 2 to further increase the temperature of the ash residue and obtain circulating ash particles at 900-1000°C.

[0038] The purpose of the above system is to provide a high-temperature solid particle heat storage and release device, and a fast and flexible peak-shaving system coupled with a circulating fluidized bed boiler unit, so as to realize the fast and flexible peak-shaving of the circulating fluidized bed boiler unit, while having the advantages of low heat storage cost, high efficiency, reliable operation, and fast adjustment and flexible peak-shaving.

[0039] Specifically: 1) Low-cost and reliable heat storage medium: Using high-temperature circulating ash solid particles from a circulating fluidized bed boiler as the heat storage medium eliminates the need for additional procurement of specialized heat storage materials, achieving zero cost for heat storage materials. Furthermore, the circulating ash exhibits stable chemical properties and high operational reliability. 2) Precise and controllable ultra-high temperature heat storage: Employing a two-stage heating mode, the first stage heats the circulating ash solid particles to 700-900℃ through the chemical heat of coal combustion in furnace 1. The second stage further heats the circulating ash solid particles to 900-1000℃ through the combustion of a small amount of coal in the combustion heating chamber. No complex additional heating devices are required, and the heat storage temperature can be flexibly adjusted to meet ultra-high temperature heat storage requirements. 3) Two-stage rapid peak shaving in the circulating fluidized bed boiler: During load reduction, stored circulating ash lowers the ash concentration in the circulating loop to achieve rapid load reduction. During load increase, recycled circulating ash enhances heat transfer on the combustion side, while high-temperature steam generated by heat release tank 4 is sent into the main steam pipeline to regulate the steam-water side, achieving flexible peak shaving on both the combustion and steam-water sides. Its variable load regulation rate can reach the level of pulverized coal boilers or even gas boilers, contributing to the large-scale consumption of renewable energy. 5) Compared to general solid thermal energy storage technologies such as molten salt thermal energy storage, it offers lower costs, higher and wider storage temperatures, and lower system operation and maintenance costs. Compared to general solid fixed-bed thermal energy storage, it boasts higher heat exchange efficiency, smaller footprint, and lower investment costs. In summary, the system exhibits significant advantages in multiple aspects, bringing new technological breakthroughs to the field of thermal energy storage and conversion, and possesses broad application prospects and economic value.

[0040] According to embodiments of this disclosure, such as Figure 1 As shown, the combustion heating device 2 includes a combustion chamber 21 and a transport chamber 22. The bottom of the combustion chamber 21 and the transport chamber 22 are provided with fluidizing air a inlet. The bottom of the combustion chamber 21 and the bottom of the transport chamber 22 are connected so that the gas-solid mixture enters the transport chamber 22 from the combustion chamber 21 under the action of the fluidizing air a introduced into the combustion chamber 21.

[0041] Combustion chamber 21 includes an ash inlet 211 for introducing ash at a first temperature and a fuel inlet 212 for introducing second fuel c. It receives the second fuel c from fuel tank 23 and a portion of the ash at the first temperature separated from the ash-flue gas mixture, respectively, and combusts them to obtain a gas-solid mixture at the second temperature. The bottom of combustion chamber 21 is connected to the bottom of transport chamber 22, and each is equipped with an independent air chamber. Fluidizing air a enters both combustion chamber 21 and transport chamber 22 uniformly through the independent air chambers. Under the action of the fluidizing air a entering combustion chamber 21, the gas-solid mixture enters transport chamber 22 from combustion chamber 21.

[0042] The heat exchange tank 4 includes multiple heat exchange chambers, each equipped with a heat exchanger. The second portion of water fed into the system exchanges heat with circulating ash particles at a second temperature through the heat exchanger.

[0043] The heat exchange tank 4 and the furnace 1 are connected by a return material inclined pipe 44. The bottom of the heat exchange chamber is provided with a fluidizing air a inlet. Under the action of the fluidizing air a entering the heat exchange chamber, the circulating solid particles at the third temperature are sent back to the furnace 1 through the return material inclined pipe 44.

[0044] Furthermore, the exothermic tank 4 includes an evaporation chamber 41, a superheating chamber 42, and a feed chamber 43. The feed chamber 43 is connected to the heat storage tank 3, and a mechanical regulating valve 9 is installed on the pipe connecting the two to regulate the material feed and the feed rate. The evaporation chamber 41 and the superheating chamber 42 are respectively located on both sides of the feed chamber 43, and the bottoms of the evaporation chamber 41 and the superheating chamber 42 are respectively connected to the bottom of the feed chamber 43. Water first enters the evaporation chamber 41 to obtain saturated steam d, and then enters the superheating chamber to obtain superheated steam d. Each of the evaporation chamber 41, the superheating chamber 42, and the feed chamber 43 is equipped with an independent air chamber, and fluidizing air a enters the evaporation chamber 41, the superheating chamber 42, and the feed chamber 43 evenly through the air chamber.

[0045] A return material inclined pipe 44 is provided on the upper side of the heat exchange chamber. The return material inclined pipe 44 is connected to the boiler furnace 1. Under the action of the fluidizing air a introduced into the heat exchange chamber, the circulating solid particles at the third temperature are sent back to the furnace 1 through the return material inclined pipe 44, realizing the return of low-temperature ash solid particles after heat exchange.

[0046] According to embodiments of this disclosure, the system further includes a first separator 51, a second separator 52, and a return feeder 6.

[0047] The inlet of the first separator 51 is connected to the material outlet at the top of the furnace 1, so that the ash-slag-flue gas mixture enters the first separator 51 from the material outlet at the top of the furnace 1 and is separated into gas and solid, resulting in ash and slag at the first temperature and flue gas at the first temperature.

[0048] The inlet of the return feeder 6 is connected to the solid phase outlet of the first separator 51 so that ash at the first temperature enters the return feeder 6 through the solid phase outlet. The outlet of the return feeder 6 is connected to the return port at the bottom of the furnace 1 so that ash at the first temperature returns to the furnace 1 through the return port.

[0049] The system also includes a second separator 52, the inlet of which is connected to the top of the transport chamber 22 of the combustion heating device 2, so that under the action of the fluidizing air a entering the transport chamber 22, the gas-solid mixture enters the second separator 52 from the transport chamber 22. The second separator 52 is used to separate the gas-solid mixture to obtain circulating ash particles at a second temperature and circulating flue gas at a second temperature.

[0050] The solid phase outlet of the second separator 52 is connected to the heat storage tank 3 so that circulating ash particles at the second temperature are introduced into the heat storage tank 3 through the solid phase outlet.

[0051] Figure 2A schematic diagram of a circulating fluidized bed boiler variable load peak shaving system according to a second embodiment of the present disclosure is shown.

[0052] like Figure 2 As shown, the above system also includes a boiler tail flue 8.

[0053] In the first separator 51, the ash and flue gas mixture is separated into gas and solid, resulting in ash at a first temperature and flue gas at a first temperature. The flue gas at the first temperature is discharged to the boiler tail flue 8 through the gas phase outlet of the first separator 51.

[0054] An air preheater 81 is installed in the boiler tail flue 8. The air preheater 81 is used to preheat the fluidizing air a introduced into the furnace 1 using the waste heat of the flue gas in the boiler tail flue 8. A bag filter is also installed in the boiler tail flue 8.

[0055] According to embodiments of this disclosure, such as Figure 1 As shown, a denitrification device 7 is also installed at the outlet of the furnace 1, which is located in the inlet flue of the first separator 51.

[0056] Furthermore, the gas-solid mixture is separated in the second separator 52 to obtain circulating ash particles at a second temperature and circulating flue gas at a second temperature. The circulating flue gas at the second temperature has a high temperature of 900-1000℃, and this part of the high-temperature gas can be utilized in various ways.

[0057] For example, the gas phase outlet of the second separator 52 can be connected to the inlet flue of the first separator 51 through a pipeline so that high-temperature flue gas can be introduced into the inlet of the denitrification device 7; the gas phase outlet of the second separator 52 can also be connected to the inlet flue of the air preheater 81 of the tail flue 8; the gas phase outlet of the second separator 52 can also be connected to the upper / lower secondary air inlet of the boiler furnace 1; the gas phase outlet of the second separator 52 can also be connected to the return section of the boiler return leg 63.

[0058] The following explanations are provided in conjunction with the accompanying drawings.

[0059] like Figure 1 As shown, the circulating flue gas at the second temperature obtained after gas-solid separation of the gas-solid mixture at the gas phase outlet of the second separator 52 is introduced into the inlet of the denitrification device 7. That is, the gas phase outlet of the second separator 52 and the inlet flue of the denitrification device 7 are connected so that the circulating flue gas at the second temperature is introduced into the inlet of the denitrification device 7 through the gas phase outlet.

[0060] The denitrification device 7 has a relatively high denitrification efficiency at high flue gas temperatures, but a relatively low efficiency at low flue gas temperatures. For example, the flue gas obtained in the first separator 51 typically has a temperature of only 700-800℃, resulting in a relatively low denitrification efficiency. By introducing circulating flue gas at 900-1000℃ into the inlet of the denitrification device 7, the denitrification efficiency can be significantly improved.

[0061] like Figure 2 As shown, the circulating flue gas at the second temperature obtained after gas-solid separation of the gas-solid mixture at the gas phase outlet of the second separator 52 is introduced into the tail flue 8 of the boiler to increase the exhaust gas temperature of the tail flue 8; the high-temperature flue gas at the top gas phase outlet of the second separator 52 is injected into the tail flue 8 from the nozzle of the air preheater 81 inlet flue of the boiler tail flue 8.

[0062] Under ultra-low load conditions, the flue gas at the first temperature is discharged to the boiler tail flue 8 through the gas phase outlet of the first separator 51. After passing through the heating surface in the tail flue 8, the flue gas temperature decreases, the heat exchange effect of the air preheater 81 is poor, the temperature of the fluidizing air a introduced into the furnace 1 is low, and the combustion efficiency of the furnace 1 is low. The circulating flue gas at 900-1000℃ is introduced into the boiler tail flue 8 to increase the temperature of the flue gas in the tail flue 8, thereby increasing the temperature of the fluidizing air a introduced into the furnace 1 and improving the combustion efficiency of the furnace 1.

[0063] A baghouse dust collector is installed in the boiler tail flue 8. Circulating flue gas at a second temperature, i.e., 900-1000℃, is introduced into the boiler tail flue 8 to raise its temperature, preventing water condensation and thus avoiding blockage of the baghouse dust collector. Flue gas at the first temperature is discharged into the boiler tail flue 8 through the gas phase outlet of the first separator 51. As it passes through the heating surfaces in the tail flue 8, its temperature decreases. During low-load boiler operation, the flue gas temperature is even lower, potentially below 100℃ when it reaches the baghouse dust collector, leading to condensation and reduced dust removal efficiency. By raising the temperature of the flue gas in the tail flue 8, condensation can be prevented, thus avoiding blockage of the baghouse dust collector.

[0064] Figure 3 A schematic diagram of a circulating fluidized bed boiler variable load peak shaving system according to a third embodiment of the present disclosure is shown. Figure 4 A schematic diagram of a circulating fluidized bed boiler variable load peak shaving system according to a fourth embodiment of the present disclosure is shown.

[0065] like Figure 3 , Figure 4 As shown, the circulating flue gas at a second temperature obtained after gas-solid separation of the gas-solid mixture is introduced into furnace 1. The high-temperature circulating flue gas at 900-1000℃ is introduced into furnace 1 to increase the temperature of furnace 1, thereby improving the combustion efficiency and heat load of furnace 1.

[0066] The furnace 1 is equipped with a secondary air duct 11 for supplying secondary air to the furnace 1; the outlet of the return feeder 6 is connected to the return port at the bottom of the furnace 1 via the return leg 63.

[0067] According to embodiments of this disclosure, such as Figure 3As shown, the circulating flue gas at the second temperature is introduced into the furnace 1 via the secondary air duct 11; or, as... Figure 4 As shown, the circulating flue gas at the second temperature is introduced into the furnace 1 via the return leg 63. The gas phase outlet of the second separator 52 is connected to the upper / lower secondary air inlet of the boiler furnace 1; the gas phase outlet of the second separator 52 is connected to the return section of the boiler return leg 63. The introduction method can be flexibly selected according to the actual needs of the project. In this way, the existing boiler inlet can be used directly, and there is no need to set up a separate high-temperature gas inlet.

[0068] According to an embodiment of this disclosure, a return riser 61 is provided between the solid phase outlet of the first separator 51 and the inlet of the return feeder 6.

[0069] There are two ways to introduce ash at a first temperature from the solid phase outlet of the first separator 51 into the combustion chamber 21. Specifically, the combustion chamber 21 includes an ash inlet 211 for introducing ash at the first temperature, and the ash inlet 211 is connected to the return feeder 6 via the discharge pipe 62 or to the return riser 61.

[0070] like Figures 1-4 The first method is shown, in which the combustion heating device 2 is connected to the return feeder 6 via the discharge pipe 62, so that a portion of the ash and slag at the first temperature in the return feeder 6 is fed into the combustion heating device 2 via the discharge pipe 62.

[0071] Figure 5 A schematic diagram of a circulating fluidized bed boiler variable load peak shaving system according to a fifth embodiment of the present disclosure is shown.

[0072] like Figure 5 As shown in the second method, the combustion heating device 2 is connected to the discharge pipe 62 and the return pipe 61 so that a portion of the ash and slag at the first temperature in the return pipe 61 is fed into the combustion heating device 2 through the discharge pipe 62.

[0073] The discharge pipe 62 is equipped with a mechanical regulating valve 9, which is used to regulate the amount of ash and slag fed into the combustion chamber 21.

[0074] The two methods mentioned above can be flexibly selected according to actual installation needs. For example, when there is enough vertical installation space, the combustion heating device 2 can be connected to the return feeder 6 through the discharge pipe 62; when there is insufficient vertical installation space, the heating device can be connected to the return riser 61 through the discharge pipe 62.

[0075] The following provides an exemplary description of a circulating fluidized bed boiler variable load peak-shaving system and a peak-shaving method based on the system, according to embodiments of the present disclosure.

[0076] According to embodiments of this disclosure, a circulating fluidized bed boiler variable load peak shaving system includes a circulating fluidized bed boiler and a heat storage and release system coupled to the boiler.

[0077] The circulating fluidized bed boiler consists of a furnace 1, a first separator 51, a return feeder 6, a tail flue 8, and heating surfaces, including an air preheater 81. The bottom dense phase zone of the furnace 1 has a coal feeder and a fluidizing air a (primary air) at the bottom.

[0078] The heat storage and release system includes a combustion heating device 2, which is connected to a discharge pipe 62 and a return feeder 6. A mechanical regulating valve 9 is installed on the discharge pipe 62. The combustion heating device 2 has a combustion chamber 21 and a transport chamber 22, which are connected at the bottom and each is equipped with an independent air chamber. Fluidizing air a is evenly introduced into the combustion chamber 21 and the transport chamber 22 through the independent air chambers. The top of the combustion chamber 21 is provided with a fuel inlet 212, which is connected to the fuel bin 23. The upper part of the transport chamber 22 is provided with a gas-solid material outlet, which is connected to the inlet of the second separator 52 to realize the transport of the heated gas-solid mixture.

[0079] The gas phase outlet of the second separator 52 is connected to the inlet flue of the first separator 51 of the boiler through a pipeline, and the solid phase outlet is connected to the heat storage tank 3 through a pipeline, so as to realize the separation of high temperature ash and flue gas after gas-solid separation.

[0080] Mechanical regulating valves 9 are installed on both the inlet and outlet pipes of the heat storage tank 3 to control the storage and release rate of high-temperature circulating ash particles. The bottom of the tank is connected to the top of the heat release tank 4 via a connecting pipe, forming a heat storage and release material channel. The heat release tank 4 has a feeding chamber 43 and multiple heat exchange chambers, such as an evaporation chamber 41 and a superheating chamber 42. Preheater heating surfaces, evaporation heating surfaces, or superheating heating surfaces are arranged in the evaporation chamber 41 and superheating chamber 42. Each heat exchange chamber has an independent air chamber at its bottom, through which fluidizing air a is evenly introduced into the heat exchange chamber. A return material inclined pipe 44 is installed on the upper middle part of the side of the heat exchange chamber, connecting to the furnace 1 to realize the return of low-temperature ash solid particles after heat exchange. The high-temperature steam d generated after heat exchange is used for heating or fed into a steam turbine for power generation.

[0081] During the heat storage process (boiler load reduction stage): The mechanical regulating valve 9 on the discharge pipe 62 of the combustion heating device 2 is opened, allowing the medium-high temperature circulating ash solid particles (700-800℃) in the boiler system to enter the combustion chamber 21 of the combustion heating device 2 through the discharge pipe 62. Coal is slowly fed through the fuel bin 23 at the top of the combustion chamber 21, mixing and heating with the medium-temperature circulating ash. Simultaneously, fluidizing air a is introduced through the independent air chamber at the bottom of the combustion chamber 21. The coal undergoes a combustion reaction and releases heat in the combustion chamber 21 with the help of the high-temperature heat source of the circulating ash, raising the ash temperature to 900-1000℃ and producing ultra-high temperature circulating ash solid particles. During this period, the coal feed rate and air feed rate are dynamically adjusted according to the real-time ash temperature of the combustion chamber 21 to maintain a stable target temperature. The high-temperature ash solid particles in the combustion chamber 21 are driven into the conveying chamber 22 by the fluidizing air a, and then sent to the second separator 52 through the gas-solid material outlet at the top of the conveying chamber 22 to achieve gas-solid separation. The separated high-temperature flue gas is fed into the inlet flue of the first separator 51, and the separated high-temperature ash is stored in the heat storage tank 3 through the solid phase outlet pipe, completing the heat storage process. The high-temperature flue gas after gas-solid separation enters the flue before the inlet SNCR nozzle of the boiler's first separator 51 to increase the flue gas temperature, or enters the inlet flue of the air preheater 81 in the boiler tail flue to increase the exhaust temperature under ultra-low load, or enters the secondary air nozzle or return material leg 63 in the boiler furnace 1 to increase the bed temperature in the dense phase zone at the bottom of the boiler furnace 1 and improve combustion efficiency.

[0082] Heat release process (boiler load increase stage): The solid phase at the bottom outlet of the cyclone separator in the heat storage and release system enters the heat storage tank 3, thus completing the heat storage process. Open the mechanical regulating valve 9 at the bottom of the heat storage tank 3 to send the high-temperature ash solid particles (900~1000℃) in the tank to the feed chamber 43 of the heat release tank 4 through the connecting pipe. The high-temperature circulating ash enters two parallel heat exchange chambers from the bottom under the action of the bottom fluidizing air a. The heat exchange chambers are equipped with heat-receiving surfaces. Fluidizing air a is introduced through the independent air chamber at the bottom of the heat exchange chambers to allow the high-temperature ash solid particles to fully exchange heat with the heat-receiving surfaces in the heat exchange chambers. The working fluid in the heat-receiving surfaces absorbs heat to generate high-temperature steam d. The high-temperature steam d is sent to the main steam d pipeline to participate in the power generation and peak shaving on the steam-water side. The high-temperature steam d generated after heat exchange is used for heating or enters the steam turbine for power generation. The low-temperature circulating ash particles after heat exchange then enter the boiler furnace 1 for the next cycle, thus completing the heat release process. For example, the low-temperature ash solid particles that have cooled down after heat exchange are returned to the furnace 1 through the return inclined pipe 44 in the upper middle part of the side of the heat exchange chamber under the action of fluidizing air a, which increases the concentration of circulating ash in the furnace 1, enhances the heat transfer between the circulating ash and the working fluid side of the furnace 1 heating surface, increases the rate of change of load on the combustion side, and completes the heat release process.

[0083] During the above implementation process, parameters such as the opening degree of the mechanical regulating valve, the coal feed rate, and the fluidizing air volume can be adjusted in real time according to changes in boiler load and target ash temperature.

[0084] It is evident that the above system constructs an efficient, stable, and economical fluidized high-temperature solid particle heat storage and release system, which solves the problems existing in current heat storage technologies and improves the efficiency and reliability of energy storage and conversion.

[0085] Those skilled in the art will understand that the features described in the various embodiments of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0086] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A variable load peak-shaving system for a circulating fluidized bed boiler, characterized in that, The system includes: The furnace is used to heat a first portion of water fed into the system to generate steam by releasing heat through the combustion of a first fuel, wherein the combustion of the first fuel generates an ash-slag-flue gas mixture at a first temperature; A combustion heating device is used to receive a second fuel and a portion of ash at a first temperature separated from the ash-slag flue gas mixture during a load reduction phase, and to generate a gas-solid mixture at a second temperature through an exothermic combustion reaction between the portion of ash at the first temperature and the second fuel, the gas-solid mixture comprising circulating flue gas and circulating ash particles. A thermal storage tank is used to store circulating ash particles at a second temperature obtained after gas-solid separation of the gas-solid mixture during the load reduction phase.

2. The system according to claim 1, characterized in that, Also includes: A heat-releasing tank is used to heat a second portion of water fed into the system to obtain superheated steam during the load-increasing phase, using the heat from the circulating ash particles at the second temperature. This is done in a first manner to increase the system's heat load. The circulating ash particles at the second temperature release heat to generate circulating ash particles at a third temperature, and the circulating solid particles at the third temperature are sent back to the furnace to increase the system's heat load in a second manner.

3. The system according to claim 2, characterized in that, Also includes: A first separator, the inlet of which is connected to the furnace, so that the ash-slag-flue gas mixture enters the first separator from the furnace and is separated into gas and solid, resulting in ash at a first temperature and flue gas at a first temperature; The return feeder has an inlet connected to the solid phase outlet of the first separator, so that ash at the first temperature enters the return feeder through the solid phase outlet. The outlet of the return feeder is connected to the return port at the bottom of the furnace, so that ash at the first temperature returns to the furnace through the return port.

4. The system according to claim 3, characterized in that: A return riser is provided between the solid phase outlet of the first separator and the inlet of the return feeder; The combustion heating device is connected to the return feeder via a discharge pipe; Alternatively, the combustion heating device is connected to the return riser via a discharge pipe.

5. The system according to any one of claims 1-4, characterized in that, The numerical range of the first temperature is 700-900℃; The numerical range of the second temperature is 900-1000℃; The numerical range of the third temperature is 300-400℃.

6. The system according to claim 1, characterized in that: A denitrification device is also installed at the horizontal flue outlet of the furnace; The circulating flue gas at a second temperature obtained after gas-solid separation of the gas-solid mixture is introduced into the inlet of the denitrification device.

7. The system according to claim 6, characterized in that: The combustion heating device includes a combustion chamber and a transport chamber. The bottom of the combustion chamber and the transport chamber are provided with fluidizing air inlets. The bottom of the combustion chamber and the bottom of the transport chamber are connected so that the gas-solid mixture enters the transport chamber from the combustion chamber under the action of the fluidizing air introduced into the combustion chamber. The system also includes a second separator, the inlet of which is connected to the top of the transport chamber, so that the gas-solid mixture enters the second separator from the transport chamber under the action of fluidizing air introduced into the transport chamber. The second separator is used to perform gas-solid separation on the gas-solid mixture to obtain circulating ash particles at the second temperature and circulating flue gas at the second temperature. The solid phase outlet of the second separator is connected to the thermal storage tank; The gas phase outlet of the second separator is connected to the inlet of the denitrification device.

8. The system according to claim 1, characterized in that: The system also includes a boiler tail flue; The circulating flue gas at the second temperature obtained after gas-solid separation of the gas-solid mixture is introduced into the inlet of the air preheater in the tail flue of the boiler to increase the exhaust temperature of the tail flue. An air preheater is installed in the tail flue of the boiler. The air preheater is used to preheat the primary and secondary air introduced into the furnace by utilizing the waste heat of the flue gas in the tail flue of the boiler.

9. The system according to claim 3, characterized in that: The circulating flue gas at the second temperature obtained after gas-solid separation of the gas-solid mixture is introduced into the furnace. The furnace is equipped with a secondary air duct for supplying secondary air into the furnace; The outlet of the return feeder is connected to the return port at the bottom of the furnace via the return leg; The circulating flue gas at the second temperature is introduced into the furnace through a secondary air duct; or, the circulating flue gas at the second temperature is introduced into the furnace through a return leg.

10. The system according to claim 1, characterized in that: The heat-exchanging tank includes multiple heat exchange chambers, each equipped with a heat exchanger. The second portion of water fed into the system exchanges heat with the circulating ash particles at the second temperature through the heat exchanger. The heat exchange tank and the furnace are connected by a return inclined pipe. A fluidizing air inlet is provided at the bottom of the heat exchange chamber. Under the action of the fluidizing air introduced into the heat exchange chamber, the circulating solid particles at the third temperature are sent back to the furnace through the return inclined pipe.

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