Method and system for fast load change of a circulating fluidized bed combustion

Abstract

The application discloses a combustion method and system for quick load regulation of a circulating fluidized bed, and relates to the technical field of power systems. Fine powder fuel is delivered to a fine powder fuel supply pipe which is nested in a secondary air pipe by recirculated flue gas, and the secondary air of the secondary air pipe entrains the fine powder fuel into a dilute phase zone of the furnace. The pulverized coal is delivered in an inert environment formed by the recirculated flue gas, effectively isolating oxygen and reducing the risk of spontaneous combustion or deflagration that may occur due to volatilization and accumulation of the pulverized coal in the closed space such as the fine powder fuel supply pipe. By adjusting the fine powder fuel in the dilute phase zone, the load of the circulating fluidized bed boiler is adjusted. Compared with the related art which adjusts the load of the circulating fluidized bed boiler by changing the primary fuel and air volume in the dense phase zone, the present application responds quickly and significantly improves the flexibility of the circulating fluidized bed boiler and the peak regulation capacity of the power grid.

Description

Technical Field

[0001] This application relates to the field of power system technology, and in particular to a combustion method and system for rapid load adjustment in a circulating fluidized bed. Background Technology

[0002] Circulating fluidized bed (CFB) combustion technology, as a highly efficient and clean coal combustion technology, has been widely used over the past few decades. The core advantages of CFB lie in its wide fuel adaptability (it can burn various types of coal, biomass, industrial waste, etc.), high combustion efficiency, low in-furnace desulfurization costs, and low initial nitrogen oxide (NOx) emissions.

[0003] In related technologies, CFB boilers mostly use an independent coal feeding system to add granular coal. However, in actual operation, the rapid load response capability of circulating fluidized beds is relatively weak. The main reason is that the ignition and burnout time of granular coal is relatively long. When the load needs to be increased rapidly, the rate at which the fuel releases heat is insufficient, making it difficult to achieve a rapid increase in boiler load in a short period of time even with an increase in the amount of coal fed.

[0004] Fine fuel is characterized by rapid ignition and combustion. Introducing fine fuel into the furnace can significantly improve the dynamic response performance of the boiler. However, directly feeding fine fuel into the boiler presents the following problems: 1. Fine fuel is highly prone to deflagration, posing a safety risk; 2. Using high-temperature air to feed fine fuel into the furnace can easily lead to excessively high local temperatures, increasing the formation of thermal NOx. Although some related technologies employ flue gas recirculation (FGR) to reduce the formation of thermal NOx, it is usually introduced directly into the furnace, causing the oxygen content in the combustion zone to be diluted overall, resulting in incomplete combustion of fine fuel, reduced boiler thermal efficiency, and decreased combustion stability, posing a risk of flameout.

[0005] Therefore, how to achieve rapid load adjustment of boilers and ensure boiler thermal efficiency and combustion stability has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This application proposes a combustion method for rapid load adjustment in a circulating fluidized bed boiler, enabling rapid load adjustment while ensuring boiler thermal efficiency and combustion stability. This application also proposes a system applicable to the aforementioned combustion method for rapid load adjustment in a circulating fluidized bed boiler.

[0007] To achieve the above objectives, this application provides a combustion method for rapid load adjustment in a circulating fluidized bed, comprising:

[0008] The main fuel is supplied to the dense phase zone of the furnace in a circulating fluidized bed boiler;

[0009] Fine fuel is transported by recirculated flue gas to a fine fuel supply pipe nested within a secondary air duct, so that the secondary air in the secondary air duct draws the fine fuel into the dilute phase zone of the furnace.

[0010] Optionally, in the above-mentioned combustion method for rapid load adjustment in a circulating fluidized bed, the flow rate ratio of the fine fuel, the secondary air, and the recirculated flue gas is 1:(2~8):(0.8~3), and the ratio of the velocity of the fine fuel jet to the velocity of the secondary air is 0.6~0.9.

[0011] Optionally, in the above-mentioned combustion method for rapid load adjustment in a circulating fluidized bed, the embedment length of the fine fuel supply pipe in the secondary air duct is at least 5 times the diameter of the fine fuel supply pipe.

[0012] And / or, the diameter ratio of the fine powder fuel supply pipe to the secondary air pipe is 0.15~0.35.

[0013] Optionally, the above-mentioned combustion method for rapid load adjustment in a circulating fluidized bed further includes:

[0014] Adjust the flow rates of the fine powder fuel, the secondary air, and the recirculated flue gas according to the load adjustment requirements of the circulating fluidized bed boiler;

[0015] The load adjustment requirements include both increasing and decreasing the load.

[0016] Optionally, in the above-described combustion method for rapid load adjustment in a circulating fluidized bed boiler, the flow rates of the fine powder fuel, the secondary air, and the recirculated flue gas are adjusted according to the load demand of the circulating fluidized bed boiler. Specifically,

[0017] When the load increases, the flow rates of the fine fuel, the secondary air, and the recirculated flue gas are increased;

[0018] When the load is reduced, the flow rates of the fine fuel and the secondary air are decreased, while the flow rate of the recirculated flue gas is increased.

[0019] Optionally, in the above-mentioned circulating fluidized bed combustion method for rapid load adjustment, fine powder fuel is transported to a fine powder fuel supply pipe nested within a secondary air duct via recirculated flue gas. Specifically,

[0020] The fine fuel bin supplies fine fuel to the fine fuel feeder;

[0021] The recirculated flue gas pipeline supplies the recirculated flue gas to the fine fuel feeder, so that the fine fuel and the recirculated flue gas are mixed to obtain a gas-solid two-phase flow of the fine fuel and the recirculated flue gas;

[0022] The recirculated flue gas provides the power to transport the gas-solid two-phase flow, enabling the gas-solid two-phase flow to be transported to the fine powder fuel supply pipe through the transport pipeline.

[0023] Optionally, in the above-mentioned combustion method for rapid load adjustment in a circulating fluidized bed, the fine fuel bin supplies fine fuel to the fine fuel feeder, and before that, the coarse fuel is ground to obtain the fine fuel, and the fine fuel is transported to the fine fuel bin;

[0024] The main fuel is supplied to the dense phase zone of the furnace in a circulating fluidized bed boiler, specifically as follows:

[0025] The main fuel is supplied to the dense phase region through the main fuel supply pipeline, which is independent of the fine fuel supply pipeline.

[0026] Optionally, in the above-described combustion method for rapid load adjustment in a circulating fluidized bed, the recirculated flue gas is supplied to the fine powder fuel feeder via the recirculated flue gas pipeline, and the process further includes:

[0027] Adjust the temperature of the recirculated flue gas to 80℃~150℃.

[0028] Secondly, this application provides a system for rapid load adjustment of a circulating fluidized bed, including a circulating fluidized bed boiler, a main fuel supply pipeline, a secondary air pipeline, and a fine powder fuel supply assembly;

[0029] The main fuel supply pipeline is connected to the dense phase zone of the furnace of the circulating fluidized bed boiler, and the main fuel supply pipeline is used to deliver main fuel to the dense phase zone to achieve stable combustion.

[0030] The fine fuel supply assembly includes a fine fuel feeder, a fine fuel supply pipe, and a recirculated flue gas pipeline.

[0031] The recirculated flue gas pipeline is connected to the fine powder fuel feeder. The recirculated flue gas pipeline is used to supply recirculated flue gas into the fine powder fuel feeder so that the recirculated flue gas mixes with the fine powder fuel supplied into the fine powder fuel feeder to obtain a gas-solid two-phase flow of the fine powder fuel and the recirculated flue gas.

[0032] The outlet of the fine fuel feeder is connected to the inlet of the fine fuel supply pipe through a conveying pipeline. The recirculated flue gas provides conveying power for the gas-solid two-phase flow. The fine fuel supply pipe is nested inside the secondary air duct. The outlet of the fine fuel supply pipe is located at the secondary air inlet so that the secondary air entrains the fine fuel into the dilute phase region.

[0033] Optionally, the above-mentioned circulating fluidized bed rapid load adjustment system also includes a fine powder fuel bin for supplying fine powder fuel to the fine powder fuel feeder.

[0034] Optionally, the above-mentioned circulating fluidized bed rapid load adjustment system also includes a coal mill, which is used to grind the main fuel to obtain fine powder fuel;

[0035] The coal mill is connected to the fine powder fuel bin.

[0036] Optionally, in the above-mentioned circulating fluidized bed rapid load adjustment system, the recirculated flue gas pipeline includes a flue gas duct, a fan, a superheater, an economizer, and an air preheater;

[0037] A superheater, economizer, air preheater, and fan are sequentially installed on the flue gas duct along the flue gas flow direction.

[0038] This application provides a combustion method for rapid load adjustment in a circulating fluidized bed boiler. Fine pulverized fuel is transported via recirculated flue gas to a fine pulverized fuel supply pipe nested within a secondary air duct. The secondary air in the secondary air duct entrains the fine pulverized fuel into the dilute phase zone of the furnace. The pulverized coal is transported within the inert environment created by the recirculated flue gas, effectively isolating oxygen and reducing the risk of spontaneous combustion or deflagration that may occur due to volatile matter release and accumulation of pulverized coal in confined spaces such as the fine pulverized fuel supply pipe. This solution adjusts the load of the circulating fluidized bed boiler by regulating the fine pulverized fuel in the dilute phase zone. Compared to related technologies that rely on changing the main fuel and air volume in the dense phase zone to adjust the load of the circulating fluidized bed boiler, this method offers rapid response and significantly improves the flexibility and grid peak-shaving capability of the circulating fluidized bed boiler.

[0039] This application also proposes a system applicable to the aforementioned combustion method for rapid load adjustment in circulating fluidized beds. Since the combustion method for rapid load adjustment in circulating fluidized beds has the aforementioned technical effects, the system applicable to this combustion method also has the same technical effects, and will not be elaborated further here. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort, and this application can be applied to other similar scenarios based on the provided drawings. Unless obvious from the linguistic context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0041] Figure 1This is a schematic diagram of the structure of the circulating fluidized bed rapid load adjustment system provided in the embodiments of this application.

[0042] in:

[0043] 1-Circulating fluidized bed boiler; 2-Secondary air duct; 3-Fine powder fuel supply pipe; 4-Fine powder fuel bin; 5-Fine powder fuel feeder; 6-Conveying pipeline; 7-Main fuel supply pipeline; 8-Recirculating flue gas pipeline; 9-Coal mill; 10-Secondary air fan; 11-Air preheater; 12-Secondary air valve; 13-Flue gas valve. Detailed Implementation

[0044] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. The described embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without inventive effort are within the scope of protection of the present application.

[0045] It should be noted that, for ease of description, only the parts relevant to the application are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0046] It should be understood that the terms "system," "apparatus," "unit," and / or "module" used in this application are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0047] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0048] In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, in the description of the embodiments of this application, "multiple" refers to two or more.

[0049] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0050] In a first aspect, this application discloses a combustion method for rapid load adjustment in a circulating fluidized bed, comprising:

[0051] The main fuel is supplied to the dense phase zone of the furnace of the circulating fluidized bed boiler 1;

[0052] Fine powder fuel is supplied to the dilute phase zone of the furnace of the circulating fluidized bed boiler 1.

[0053] In the circulating fluidized bed boiler 1, the dense phase zone and the dilute phase zone are divided according to the concentration and flow state of the bed material in the furnace. The dense phase zone is located in the lower part of the furnace, with a high bed material concentration, maintaining basic, stable, and low-load combustion and thermal inertia; the dilute phase zone is located in the upper part of the furnace, with a lower bed material concentration and a higher gas velocity in the gas-solid two-phase flow, and the solid particles are in a state of rapid fluidization or transport, mainly transferring heat to the heating surfaces around the furnace through radiation and convection heat transfer.

[0054] For ease of description, this solution is illustrated using coal as the fuel. However, the fuel is not limited to coal; other fuels suitable for circulating fluidized bed boilers 1 in the power system field can also be used, all of which are within the scope of this application.

[0055] The main fuel supplied to the furnace is granular coal (the particle size of the granular coal is 1mm-10mm). The granular coal is sent into the lower dense phase zone of the furnace of the circulating fluidized bed boiler 1 to maintain a stable combustion state of the circulating fluidized bed boiler 1.

[0056] The fine fuel supplied to the furnace is pulverized coal (particle size of 0mm-1mm). Fine fuel can also be petroleum coke, dried biomass fine powder, gasification slag, sludge, and other difficult-to-treat or explosive waste fuels.

[0057] Fine fuel is transported through fine fuel supply pipe 3. Fine fuel supply pipe 3 is embedded in secondary air duct 2.

[0058] Please see Figure 1 In some embodiments of this application, the main fuel supply pipeline 7, which supplies main fuel to the dense phase zone of the furnace of the circulating fluidized bed boiler 1, and the fine powder fuel supply pipeline 3, which supplies pulverized coal fuel to the dilute phase zone of the furnace of the circulating fluidized bed boiler 1, are independent of each other and not connected to each other, so as to realize the separate transportation of main fuel and fine powder fuel, and deliver them to different positions in the furnace.

[0059] The granular coal is transported through an independent main fuel supply pipeline 7, which allows for individual adjustment of the granular coal transport flow rate and speed, thereby enabling the regulation of the main fuel supply, ensuring full combustion of the main fuel in the dense phase zone, and maintaining a stable combustion state in the circulating fluidized bed boiler 1.

[0060] Continue reading Figure 1 In this application, the fine powder fuel supply pipe 3 is embedded in the secondary air duct 2, and the outlet of the fine powder fuel supply pipe 3 is located at the secondary air inlet. After the pulverized coal is ejected at the outlet of the fine powder fuel supply pipe 3, it is immediately drawn in, carried and fully mixed by the secondary air in the secondary air duct 2, and thus enters the dilute phase zone in the upper part of the furnace.

[0061] This solution provides a novel pulverized coal feeding method for a circulating fluidized bed boiler 1, utilizing secondary air for pulverized coal feeding. The pulverized coal is directly fed into the dilute phase zone (the area with the highest oxygen concentration) of the furnace in the circulating fluidized bed boiler 1 via secondary air. Upon entering the furnace, the pulverized coal ignites rapidly and burns intensely, directly and quickly altering the instantaneous heat release of the dilute phase zone (the main heat release area of ​​the furnace) without lag, significantly improving the combustion intensity and reaction rate of the dilute phase zone, and achieving rapid load regulation.

[0062] This solution adjusts the load of the circulating fluidized bed boiler 1 by regulating the fine powder fuel in the dilute phase zone. Compared with related technologies that rely on changing the main fuel and air volume in the dense phase zone to adjust the load of the circulating fluidized bed boiler 1, this solution offers a rapid response and significantly improves the flexibility and grid peak-shaving capability of the circulating fluidized bed boiler 1.

[0063] This design integrates the fine fuel supply pipe 3 within the secondary air duct 2, achieving the integration of the fine fuel injection function with the secondary air system, and thus integrating the air supply and pulverized coal conveying systems. The secondary air duct 2, in addition to supplying air to the dilute phase zone of the furnace, also serves to convey pulverized coal. Utilizing high-speed secondary air as an ejector and mixer, the fine fuel is thoroughly mixed with the combustion air upon entering the furnace. This design, through the combination of the fine fuel supply pipe 3 and the secondary air duct 2, forms an integrated design that enhances mixing and combustion.

[0064] The pulverized coal is immediately drawn in and carried by the secondary air the instant it leaves the fine fuel supply pipe 3, achieving mixing and full contact between the pulverized coal and the combustion air. The pulverized coal is then directly fed into the dilute phase zone of the furnace of the circulating fluidized bed boiler 1, which requires the highest oxygen concentration. After entering the furnace, the pulverized coal ignites rapidly and burns intensely, directly and quickly changing the instantaneous heat release of the dilute phase zone (the main heat release area of ​​the furnace) without lag, greatly improving the combustion intensity and reaction rate of the dilute phase zone, and achieving rapid load regulation.

[0065] The fine coal fuel supply pipe 3 is embedded in the secondary air duct 2. On the one hand, it does not require modification of the boiler furnace structure, thus reducing costs. On the other hand, the pneumatic conveying of pulverized coal (recirculated flue gas) and the combustion air (secondary air) converge and coordinate at the secondary air inlet, reducing the demand for an independent air system.

[0066] The fine coal fuel supply pipe 3 is connected to the recirculated flue gas pipe 8, using the recirculated flue gas to provide power for the transportation of pulverized coal. That is, the power for the pneumatic transportation of pulverized coal comes from the recirculated flue gas. The recirculated flue gas is the flue gas from the tail end of the boiler.

[0067] This scheme utilizes recirculated flue gas as the conveying medium for pulverized coal, providing an inert environment for its transport. It's important to note that this inert environment is not a purely inert gas environment, but rather a gaseous environment with low oxygen content and insufficient combustion conditions. The main components of the boiler tail gas (or recirculated flue gas) are nitrogen, carbon dioxide, and water vapor.

[0068] During the transportation of pulverized coal, especially in confined spaces (such as the fine fuel supply pipe 3 and the fine fuel feeder 5), there is a risk of volatile matter release and mixing with oxygen. Specifically, pulverized coal releases flammable volatile gases (such as methane and hydrogen) when heated; if air is used as the transportation medium, these volatile gases will mix with oxygen, forming a flammable or even explosive mixture, which can easily lead to spontaneous combustion or deflagration.

[0069] This scheme transports pulverized coal in an inert environment formed by recirculated flue gas, effectively isolating it from oxygen. Even if the pulverized coal is heated and releases volatiles during transportation, these volatiles cannot be ignited, reducing the risk of spontaneous combustion or deflagration that may occur in enclosed spaces such as the fine fuel supply pipe 3 due to the release and accumulation of volatiles.

[0070] Meanwhile, the temperature of the recirculated flue gas is usually lower than the ignition point of pulverized coal, ensuring that the recirculated flue gas does not provide a heat source sufficient to ignite volatiles during transportation, further reducing the risk of spontaneous combustion or deflagration.

[0071] Pulverized coal is burned in the relatively low-temperature (750℃~900℃) dilute phase zone, which avoids the generation of large amounts of high-temperature thermal NOx from the source; the injection of recirculated flue gas further dilutes the oxygen concentration in the combustion zone and reduces the flame temperature, thus doubly inhibiting the generation of NOx.

[0072] This solution enables the safe, precise, and direct feeding of pulverized coal into the dilute phase zone of the circulating fluidized bed boiler 1, while simultaneously utilizing recirculated flue gas to address safety and environmental protection issues (recovering and utilizing flue gas from the boiler tail end).

[0073] like Figure 1As shown, the secondary air system for providing secondary air includes a secondary air fan 10, an air preheater 11, a secondary air valve 12, and a secondary air duct 2. The air preheater is used to heat the secondary air to 300℃-400℃; the secondary air valve 12 is used to regulate the flow rate of the incoming secondary air.

[0074] In some embodiments of this application, the flow rate ratio of fine fuel powder, secondary air, and recirculated flue gas is 1:(2~8):(0.8~3). The proportion of secondary air should not be too low, otherwise it will significantly reduce the rigidity of the secondary air and weaken its entrainment capacity for fine fuel powder.

[0075] The ratio of the velocity of the fine fuel jet to the velocity of the secondary air is 0.6 to 0.9. When the velocity ratio of the fine fuel jet to the secondary air is too large (>1), the fine fuel will enter the furnace in the form of a "core jet", resulting in poor mixing and easy local high temperature and incomplete combustion. When the velocity ratio of the fine fuel jet to the secondary air is small (<0.5), the fine fuel may not be able to effectively penetrate the secondary air boundary layer and may adhere to the outlet of the secondary air duct or near the furnace wall, posing a risk of coking.

[0076] The embedment length of the fine fuel supply pipe 3 within the secondary air duct 2 is at least 5 times the diameter of the fine fuel supply pipe 3. The longer embedment length of the fine fuel supply pipe 3 allows for a more uniform distribution of the secondary air velocity at the outlet of the fine fuel supply pipe 3, which is beneficial for the uniform mixing of pulverized coal and secondary air.

[0077] The diameter ratio of the fine fuel supply pipe 3 to the secondary air pipe 2 is 0.15~0.35. When the pipe diameter ratio is too small (<0.15), the flow rate of the fine fuel jet is too low and cannot effectively penetrate the secondary air boundary layer. The fuel is carried "on the wall" and is prone to coking. When the pipe diameter ratio is too large (>0.35), the fine fuel jet occupies too large a flow area. The encapsulation and shearing effect of the secondary air on the fuel is weakened, the combustion is concentrated in the central area, NOx generation increases, and the temperature distribution in the dilute phase region is uneven.

[0078] Coordination during load increase: In the initial stage of load increase, the supply of fine powder fuel is rapidly increased to meet the load increase demand by utilizing the rapid response of the dilute phase region. After the combustion in the dilute phase region stabilizes, the supply of main fuel is gradually increased to supplement the heat storage capacity and basic load support capacity of the dense phase region. The increase in main fuel accounts for 30% to 50% of the load increase, with the remainder being supplied by fine powder fuel. This ensures rapid response while avoiding fluidization instability in the dense phase region due to sudden changes in heat load.

[0079] Coordination during load reduction: When reducing load, the supply of fine fuel should be reduced rapidly first, followed by a gradual reduction of the main fuel supply according to the load target. The reduction in main fuel should be slightly less than the reduction in fine fuel to maintain the bed temperature in the dense phase zone within a reasonable range and avoid unstable combustion or flameout due to excessively low bed temperature.

[0080] The combustion method of the circulating fluidized bed boiler 1 disclosed in this scheme also includes: adjusting the flow rates of fine powder fuel, secondary air and recirculated flue gas according to the load demand of the circulating fluidized bed boiler 1.

[0081] The load requirements of circulating fluidized bed boiler 1 include load increase, load decrease and stable operation.

[0082] The flow rates of fine fuel, secondary air, and recirculated flue gas are synergistically adjusted to meet the rapid load adjustment requirements of circulating fluidized bed boilers.

[0083] Specifically, when increasing the load, increase the flow rates of fine fuel, secondary air, and recirculated flue gas; when decreasing the load, decrease the flow rates of fine fuel and secondary air, and increase the flow rate of recirculated flue gas.

[0084] Recirculated flue gas is transported through a flue gas duct, which is equipped with a flue gas valve 13. The flow rate of the recirculated flue gas is adjusted by regulating the opening of the flue gas valve 13. A secondary air valve 12 is installed on the secondary air duct 2, and the flow rate of the secondary air is adjusted by regulating the opening of the secondary air valve 12. A fine powder fuel supply pipe 3 is equipped with a fine powder fuel valve, and the flow rate of the fine powder fuel is adjusted by regulating the opening of the fine powder fuel valve. In this embodiment, the flow rate of the corresponding components is regulated by adjusting the opening of the corresponding pipeline valves.

[0085] Both the flue gas duct and the secondary air duct 2 are equipped with fans. Optionally, the flow rates of the recirculated flue gas and secondary air can be adjusted by coordinating the fans with valves.

[0086] A fine powder fuel bin 4 is installed upstream of the fine powder fuel supply pipe 3. The fine powder fuel bin 4 is used to store the prepared fine powder fuel. The outlet of the fine powder fuel bin 4 is equipped with a valve. Optionally, the valve of the outlet cooperates with the valve of the fine powder fuel supply pipe 3 to regulate the flow rate of the fine powder fuel.

[0087] Optionally, the control of the above valves and fans is achieved through a controller, realizing the automatic adjustment of the flow rates of fine fuel, secondary air and recirculated flue gas, and optimizing the response speed.

[0088] The flow rates of fine fuel powder, secondary air, and recirculated flue gas can be adjusted according to a set ratio. When the load increases, the flow rates of fine fuel powder, secondary air, and recirculated flue gas can be adjusted according to a set ratio of 1:(4~8):(0.8~1.5); when the load decreases, the flow rates of fine fuel powder, secondary air, and recirculated flue gas can be adjusted according to a set ratio of 1:(2~4):(1.5~3); during normal operation, the flow rates of fine fuel powder, secondary air, and recirculated flue gas can be adjusted according to a set ratio of 1:(5~7):(1~1.8).

[0089] Increasing the flow rate of fine fuel, i.e., increasing the fuel supply, rapidly increases the thermal power input to the boiler; increasing secondary air provides sufficient oxygen and maintains the flow field, ensuring the full and complete combustion of the new fuel, reducing the generation of incomplete combustion products, maintaining the turbulence intensity in the dilute phase zone of the furnace, and extending the residence time of pulverized coal in the furnace to ensure complete combustion; increasing recirculated flue gas, optionally, increases the recirculated flue gas proportionally or in excess of the fine fuel, ensuring the formation of a gas-solid two-phase flow between the fine fuel and the recirculated flue gas, avoiding deflagration, and ensuring that the pulverized coal is in an inert environment formed by the recirculated flue gas, ensuring safe transportation.

[0090] The coordinated regulation of fine fuel, secondary air, and recirculated flue gas creates an environment that ensures safe and complete combustion of fuel, guaranteeing that the load increase process is not only rapid but also efficient, safe, and stable.

[0091] When reducing load, decrease the flow rate of fine fuel and secondary air, and increase the flow rate of recirculated flue gas. Specifically, decrease the flow rate of fine fuel, decrease the flow rate of secondary air, and increase the flow rate of recirculated flue gas.

[0092] Reducing the flow rate of fine powder fuel, i.e. reducing the amount of fuel entering the dilute phase zone for combustion, lowers the thermal power input and rapidly reduces the thermal power output of the circulating fluidized bed boiler 1; reducing the flow rate of secondary air matches the air-to-coal ratio (the ratio of total air volume to total coal volume entering the boiler), and reducing secondary air can also reduce the turbulence intensity and oxygen supply rate in the dilute phase zone, allowing the load to decrease smoothly; increasing the amount of recirculated flue gas dilutes the concentration of fine powder fuel and oxygen concentration, gently suppressing the intensity of the combustion reaction and reducing the peak flame temperature. At the same time, the additional recirculated flue gas helps maintain the momentum and stability of the flow field in the upper part of the furnace when the secondary air is reduced, preventing turbulent airflow structure.

[0093] By coordinating the regulation of fine fuel, secondary air, and recirculated flue gas, the thermal power of the circulating fluidized bed boiler 1 is rapidly, stably, and safely reduced to the target value, and the circulating fluidized bed boiler 1 system is always protected in a controllable inert environment.

[0094] In some embodiments, the circulating fluidized bed boiler 1 is in a stable operating state, the opening degree of the secondary air valve 12 is 30%~50%, the opening degree of the flue gas valve 13 is 20%~30%, and the opening degree of the fine powder fuel valve is 5%~20%, providing only a small amount of pulverized coal into the furnace.

[0095] When the circulating fluidized bed boiler is at a load of 1 liter, increase the opening of the fine fuel valve to 20%~50%, and simultaneously increase the opening of the secondary air valve 12 to 50%~80% to provide sufficient oxygen for pulverized coal combustion and enhance upper combustion. Increase the opening of the flue gas valve 13 to 30%~50% to avoid deflagration and suppress NOx formation (different valve opening combinations can be set according to the required load increase, and the valve opening can also be dynamically adjusted within a small range based on feedback control of the current state).

[0096] When the temperature of the circulating fluidized bed boiler 1 exceeds the preset temperature, and the NOx content generated is too high and does not meet environmental protection requirements, the opening of the flue gas valve 13 is increased to 50%~80%, and the opening of the secondary air valve 12 is reduced to 10%~30% to reduce NOx generation.

[0097] When it is necessary to blend other fuels such as biomass and petroleum coke, the opening of the three valves can be dynamically adjusted to find the optimal combination.

[0098] When blending fine powder or other fuels, first determine the required flow rate of the fine powder or other fuel. Then, adjust the fine powder fuel valve until the flow rate of the fine powder or other fuel matches the preset value. Subsequently, simultaneously adjust the opening of the secondary air valve 12 and the flue gas valve to ensure that the NOx content meets the requirements and that the blended fine powder fuel can be fully combusted. The adjustment process is similar to the process of increasing load and suppressing NOx formation when using pulverized coal, except that the specific valve opening will vary depending on the type and flow rate of fuel.

[0099] This solution not only enables efficient combustion of conventional coal types but also provides a new approach for processing various special fuels. It can safely blend petroleum coke, dried biomass powder, gasification slag, sludge, and other difficult-to-process or explosive waste fuels, thus broadening fuel sources and reducing fuel costs.

[0100] Fine fuel is transported via recirculated flue gas to a fine fuel supply pipe 3 nested within a secondary air duct 2. Specifically...

[0101] The fine powder fuel bin 4 supplies fine powder fuel to the fine powder fuel feeder 5;

[0102] Recirculated flue gas is supplied to the fine fuel feeder 5 to mix the fine fuel with the recirculated flue gas, resulting in a gas-solid two-phase flow of fine fuel and recirculated flue gas.

[0103] The recirculated flue gas provides the power for conveying the gas-solid two-phase flow, which is then conveyed through the conveying pipeline 6 to the fine powder fuel supply pipeline 3.

[0104] Optionally, the fine powder fuel feeder 5 is a screw feeder valve or a screw feeder.

[0105] The fine fuel feeder 5 receives fine fuel from the fine fuel bin 4. The pulverized coal mixes with the recirculated flue gas in the enclosed environment of the fine fuel feeder 5. This means the fine fuel is pre-mixed with the recirculated flue gas before entering the fine fuel supply pipe 3, resulting in a safe, uniform, and controllable gas-solid two-phase flow. This avoids sedimentation, blockage, or pulsed conveying of pulverized coal in the fine fuel supply pipe 3 due to uneven mixing of pulverized coal and recirculated flue gas.

[0106] The gas-solid two-phase flow formed by premixing is ejected from the secondary air inlet and immediately mixes with the secondary air at a faster and more microscopic scale. At the same time, the recirculated flue gas preheats and dries the pulverized coal, which helps the pulverized coal to reach the ignition temperature more quickly when injected into the furnace, thereby increasing the combustion reaction rate.

[0107] The fine fuel bin 4 supplies fine fuel to the fine fuel feeder 5, which includes grinding coarse fuel to obtain fine fuel and then conveying the fine fuel to the fine fuel bin 4.

[0108] The circulating fluidized bed rapid load adjustment system is equipped with a coal mill 9. The working efficiency of the coal mill assembly can be adjusted according to the circulating fluidized bed boiler 1's demand for fine fuel, improving the convenience of obtaining fine fuel.

[0109] To further improve the safety of the combustion method for rapid load adjustment in circulating fluidized bed, recirculated flue gas is supplied to the fine powder fuel feeder 5, and the temperature of the recirculated flue gas is adjusted to 80°C to 150°C beforehand.

[0110] Firstly, it ensures that the temperature of the flue gas is always above the dew point to avoid condensation, maintain the stability of the physical properties of the conveying medium, and facilitate the stable operation of pneumatic conveying, ensuring that the concentration and flow rate of pulverized coal are controllable. Secondly, it avoids thermal shock, as the temperature difference between the recirculated flue gas and the furnace is smaller, resulting in less impact on the local combustion state when it is injected as a conveying medium. Thirdly, it prevents high-temperature spontaneous combustion.

[0111] Secondly, this application also provides a system for rapid load adjustment of a circulating fluidized bed, including a circulating fluidized bed boiler 1, a main fuel supply pipeline 7, a secondary air pipeline 2, and a fine powder fuel supply assembly.

[0112] The circulating fluidized bed boiler 1 has a dense phase zone and a dilute phase zone. The main fuel supply pipeline 7 is connected to the dense phase zone and is used to supply main fuel to the dense phase zone to achieve stable combustion; the secondary air pipeline 2 is connected to the dilute phase zone and is used to supply combustion air to the dilute phase zone of the circulating fluidized bed boiler 1.

[0113] The fine fuel supply assembly includes a fine fuel supply pipe 3, a fine fuel feeder 5, and a recirculated flue gas pipeline 8.

[0114] The recirculated flue gas pipeline 8 is connected to the fine powder fuel feeder 5, and the outlet of the fine powder fuel feeder 5 is connected to the inlet of the fine powder fuel supply pipeline 3 through the conveying pipeline 6.

[0115] The recirculated flue gas pipeline 8 is used to supply recirculated flue gas into the fine powder fuel feeder 5 so that the fine powder fuel and the recirculated flue gas are mixed to obtain a gas-solid two-phase flow of fine powder fuel and recirculated flue gas.

[0116] The recirculated flue gas is a gas-solid two-phase flow that enters the fine powder fuel supply pipe 3 through the conveying pipeline 6, providing the power for pneumatic conveying.

[0117] The fine fuel supply pipe 3 is nested inside the secondary air duct 2, and the outlet of the fine fuel supply pipe 3 is located at the secondary air inlet so that the secondary air can draw the fine fuel into the dilute phase region.

[0118] like Figure 1 As shown, the fine fuel supply pipe 3 is nested at one end of the secondary air duct 2 near the secondary air inlet. The diameter of the fine fuel supply pipe 3 is smaller than that of the secondary air duct 2. The fine fuel supply pipe 3 and the secondary air duct 2 are arranged coaxially, forming an annular channel for secondary air to pass through. The secondary air duct 2 has a pipe hole for the fine fuel supply pipe 3 to pass through. The wall of the fine fuel supply pipe 3 is sealed to the pipe hole, thus fixing the fine fuel supply pipe 3 to the secondary air duct 2.

[0119] like Figure 1 As shown, the main fuel supply pipeline 7, which supplies the main fuel to the dense phase zone of the furnace of the circulating fluidized bed boiler 1, and the fine powder fuel supply pipeline 3, which supplies pulverized coal fuel to the dilute phase zone of the furnace of the circulating fluidized bed boiler 1, are independent of each other, so as to realize the separate transportation of the main fuel and the fine powder fuel, and deliver them to different positions in the furnace.

[0120] For ease of description, this solution is illustrated using coal as the fuel. However, the fuel is not limited to coal; other fuels suitable for circulating fluidized bed boilers 1 in the power system field can also be used, all of which are within the scope of this application.

[0121] The main fuel supplied to the furnace is granular coal (the particle size of the granular coal is 1mm-10mm). The granular coal is sent into the lower dense phase zone of the furnace of the circulating fluidized bed boiler 1 to maintain a stable combustion state of the circulating fluidized bed boiler 1.

[0122] The fine fuel supplied to the furnace is pulverized coal (particle size of 0mm-1mm). Fine fuel can also be petroleum coke, dried biomass fine powder, gasification slag, sludge, and other difficult-to-treat or explosive waste fuels.

[0123] Large coal particles are transported through an independent main fuel supply pipeline 7, which allows for individual adjustment of the transport flow rate of large coal particles, ensuring complete combustion of fuel and maintaining a stable combustion state in the circulating fluidized bed boiler 1.

[0124] Continue reading Figure 1 In this application, the fine powder fuel supply pipe 3 is embedded in the secondary air duct 2, and the outlet of the fine powder fuel supply pipe 3 is located at the secondary air inlet. After the pulverized coal is ejected at the outlet of the fine powder fuel supply pipe 3, it is immediately drawn in, carried and fully mixed by the secondary air in the secondary air duct 2, and thus enters the dilute phase zone in the upper part of the furnace.

[0125] This solution provides a novel pulverized coal feeding method for a circulating fluidized bed boiler 1, utilizing secondary air for pulverized coal feeding. The pulverized coal is directly fed into the dilute phase zone (the area with the highest oxygen concentration) of the furnace in the circulating fluidized bed boiler 1 via secondary air. Upon entering the furnace, the pulverized coal ignites rapidly and burns intensely, directly and quickly altering the instantaneous heat release of the dilute phase zone (the main heat release area of ​​the furnace) without lag, significantly improving the combustion intensity and reaction rate of the dilute phase zone, and achieving rapid load regulation.

[0126] This solution adjusts the load of the circulating fluidized bed boiler 1 by regulating the fine powder fuel in the dilute phase zone. Compared with related technologies that rely on changing the main fuel and air volume in the dense phase zone to adjust the load of the circulating fluidized bed boiler 1, this solution offers a rapid response and significantly improves the flexibility and grid peak-shaving capability of the circulating fluidized bed boiler 1.

[0127] This design integrates the fine fuel supply pipe 3 within the secondary air duct 2, achieving the integration of the fine fuel injection function with the secondary air system, and thus integrating the air supply and pulverized coal conveying systems. The secondary air duct 2, in addition to supplying air to the dilute phase zone of the furnace, also serves to convey pulverized coal. Utilizing high-speed secondary air as an ejector and mixer, the fine fuel is thoroughly mixed with the combustion air upon entering the furnace. This design, through the combination of the fine fuel supply pipe 3 and the secondary air duct 2, forms an integrated design that enhances mixing and combustion.

[0128] The pulverized coal is immediately drawn in and carried by the secondary air the instant it leaves the fine fuel supply pipe 3, achieving mixing and full contact between the pulverized coal and the combustion air. The pulverized coal is then directly fed into the dilute phase zone of the furnace of the circulating fluidized bed boiler 1, which requires the highest oxygen concentration. After entering the furnace, the pulverized coal ignites rapidly and burns intensely, directly and quickly changing the instantaneous heat release of the dilute phase zone (the main heat release area of ​​the furnace) without lag, greatly improving the combustion intensity and reaction rate of the dilute phase zone, and achieving rapid load regulation.

[0129] The fine coal fuel supply pipe 3 is embedded in the secondary air duct 2. On the one hand, it does not require modification of the boiler furnace structure, thus reducing costs. On the other hand, the pneumatic conveying of pulverized coal (recirculated flue gas) and the combustion air (secondary air) converge and coordinate at the secondary air inlet, reducing the demand for an independent air system.

[0130] The fine coal fuel supply pipe 3 is connected to the recirculated flue gas pipe 8, using the recirculated flue gas to provide power for the conveying of pulverized coal. That is, the power for the pneumatic transport of pulverized coal comes from the recirculated flue gas. The recirculated flue gas is the flue gas discharged from the tail end of the boiler.

[0131] This scheme utilizes recirculated flue gas as the conveying medium for pulverized coal, providing an inert environment for its transport. It's important to note that this inert environment is not a purely inert gas environment, but rather a gaseous environment with low oxygen content and insufficient combustion conditions. The main components of the boiler tail gas (or recirculated flue gas) are nitrogen, carbon dioxide, and water vapor.

[0132] During the transportation of pulverized coal, especially in confined spaces (such as the fine fuel supply pipe 3 and the fine fuel feeder 5), there is a risk of volatile matter release and mixing with oxygen. Specifically, pulverized coal releases flammable volatile gases (such as methane and hydrogen) when heated; if air is used as the transportation medium, these volatile gases will mix with oxygen, forming a flammable or even explosive mixture, which can easily lead to spontaneous combustion or deflagration.

[0133] This scheme transports pulverized coal in an inert environment formed by recirculated flue gas, effectively isolating it from oxygen. Even if the pulverized coal is heated and releases volatiles during transportation, these volatiles cannot be ignited, reducing the risk of spontaneous combustion or deflagration that may occur in enclosed spaces such as the fine fuel supply pipe 3 due to the release and accumulation of volatiles.

[0134] Meanwhile, the temperature of the recirculated flue gas is usually lower than the ignition point of pulverized coal, ensuring that the recirculated flue gas does not provide a heat source sufficient to ignite volatiles during transportation, further reducing the risk of spontaneous combustion or deflagration.

[0135] This solution enables the safe, precise, and direct feeding of pulverized coal into the dilute phase zone of the circulating fluidized bed boiler 1, while simultaneously utilizing recirculated flue gas to address safety and environmental protection issues (recovering and utilizing flue gas from the boiler tail end).

[0136] This solution achieves rapid and precise load adjustment of the circulating fluidized bed boiler by dynamically adjusting the flow ratio of fine fuel, secondary air, and recirculated flue gas.

[0137] The flow ratio of fine fuel, secondary air and recirculated flue gas is 1:(2~8):(0.8~3).

[0138] Specifically, when the load increases, the flow rates of fine fuel, secondary air, and recirculated flue gas can be adjusted according to a set ratio of 1:(4~8):(0.8~1.5); when the load decreases, the flow rates of fine fuel, secondary air, and recirculated flue gas can be adjusted according to a set ratio of 1:(2~4):(1.5~3); and during normal operation, the flow rates of fine fuel, secondary air, and recirculated flue gas can be adjusted according to a set ratio of 1:(5~7):(1~1.8).

[0139] The flow rate ratio of secondary air to recirculated flue gas is 1.5 to 5.5. The proportion of secondary air should not be too low, otherwise it will significantly reduce the rigidity of the secondary air and weaken its ability to entrain fine fuel.

[0140] The velocity ratio of the fine fuel jet to the secondary air velocity is 0.6~0.9. When the velocity ratio of the fine fuel jet to the secondary air velocity is too large (>1), the fine fuel will enter the furnace in the form of a "core jet", resulting in poor mixing and easy to cause local high temperature and incomplete combustion. When the velocity ratio of the fine fuel jet to the secondary air velocity is small (<0.5), the fine fuel may not be able to effectively penetrate the secondary air boundary layer and adhere to the secondary air duct outlet or near the furnace wall, posing a risk of coking.

[0141] The embedment length of the fine fuel supply pipe 3 within the secondary air duct 2 is at least 5 times the diameter of the fine fuel supply pipe 3. The longer embedment length of the fine fuel supply pipe 3 allows for a more uniform distribution of the secondary air velocity at the outlet of the fine fuel supply pipe 3, which is beneficial for the uniform mixing of pulverized coal and secondary air.

[0142] The diameter ratio of the fine fuel supply pipe 3 to the secondary air pipe 2 is 0.15~0.35. If the flow rate of the fine fuel jet is too low, it cannot effectively penetrate the secondary air boundary layer, and the fuel is carried "on the wall", which easily leads to coking. If the pipe diameter ratio is too large (>0.35), the fine fuel jet occupies too large a flow area, the encapsulation and shearing effect of the secondary air on the fuel is weakened, the combustion is concentrated in the central region, NOx generation increases, and the temperature distribution in the dilute phase region is uneven.

[0143] Coordination during load increase: In the initial stage of load increase, the supply of fine powder fuel is rapidly increased to meet the load increase demand by utilizing the rapid response of the dilute phase region. After the combustion in the dilute phase region stabilizes, the supply of main fuel is gradually increased to supplement the heat storage capacity and basic load support capacity of the dense phase region. The increase in main fuel accounts for 30% to 50% of the load increase, with the remainder being supplied by fine powder fuel. This ensures rapid response while avoiding fluidization instability in the dense phase region due to sudden changes in heat load.

[0144] Coordination during load reduction: When reducing load, the supply of fine fuel should be reduced rapidly first, followed by a gradual reduction of the main fuel supply according to the load target. The reduction in main fuel should be slightly less than the reduction in fine fuel to maintain the bed temperature in the dense phase zone within a reasonable range and avoid unstable combustion or flameout due to excessively low bed temperature.

[0145] In some embodiments, when the circulating fluidized bed boiler 1 is running stably, the opening degree of the secondary air valve 12 is 30%~50%, the opening degree of the flue gas valve 13 is 20%~30%, and the opening degree of the fine powder fuel valve is 5%~20%.

[0146] When increasing the load, increase the opening of the secondary air valve 12 to 50%~80%, increase the opening of the flue gas valve 13 to 30%~50%, and increase the opening of the fine powder fuel valve to 20%~50%;

[0147] When the temperature of the circulating fluidized bed boiler 1 exceeds the preset temperature, it is necessary to reduce the load, decrease the opening of the secondary air valve 12 to 10%~30%, increase the opening of the flue gas valve 13 to 50%~80%, and reduce or even close the fine powder fuel valve.

[0148] The fine powder fuel feeder 5 is a screw feeder valve or a screw feeder.

[0149] The fine fuel feeder 5 receives fine fuel from the fine fuel bin 4. The pulverized coal mixes with the recirculated flue gas in the enclosed environment of the fine fuel feeder 5. This means the fine fuel is pre-mixed with the recirculated flue gas before entering the fine fuel supply pipe 3, resulting in a safe, uniform, and controllable gas-solid two-phase flow. This avoids sedimentation, blockage, or pulsed conveying of pulverized coal in the fine fuel supply pipe 3 due to uneven mixing of pulverized coal and recirculated flue gas.

[0150] The gas-solid two-phase flow formed by premixing is ejected from the secondary air inlet and immediately mixes with the secondary air at a faster and more microscopic scale. At the same time, the recirculated flue gas preheats and dries the pulverized coal, which helps the pulverized coal to reach the ignition temperature more quickly when injected into the furnace, thereby increasing the combustion reaction rate.

[0151] The circulating fluidized bed rapid load adjustment system disclosed in this scheme also includes a fine powder fuel bin 4, which is used to supply fine powder fuel to the fine powder fuel feeder 5.

[0152] A fine powder fuel valve is installed on the pipeline connecting the fine powder fuel bin 4 and the fine powder fuel feeder 5. The fine powder fuel valve is used to control the flow rate of fine powder fuel supplied from the fine powder fuel bin 4 to the fine powder fuel feeder 5.

[0153] Fine powder fuel is stored in the fine powder fuel bin 4. The opening of the fine powder fuel valve is adjusted according to the load demand of the circulating fluidized bed boiler 1.

[0154] Optionally, the circulating fluidized bed rapid load adjustment system also includes a coal mill 9 for grinding the main fuel to obtain fine powder fuel.

[0155] The coal mill 9 is connected to the fine powder fuel bin 4.

[0156] The circulating fluidized bed rapid load adjustment system is equipped with a coal mill 9. The working efficiency of the coal mill assembly can be adjusted according to the circulating fluidized bed boiler 1's demand for fine fuel, improving the convenience of obtaining fine fuel.

[0157] This solution not only enables efficient combustion of conventional coal types but also provides a new approach for processing various special fuels. It can safely blend petroleum coke, dried biomass powder, gasification slag, sludge, and other difficult-to-process or explosive waste fuels, thus broadening fuel sources and reducing fuel costs.

[0158] The recirculated flue gas pipeline 8 includes a flue gas duct, a fan, a superheater, an economizer, and an air preheater; the superheater, economizer, air preheater, and fan are sequentially installed on the flue gas duct along the flue gas flow direction.

[0159] After leaving the furnace, the high-temperature flue gas first passes through the superheater to generate superheated steam, then heats the boiler feedwater through the economizer, and finally heats the combustion air through the air preheater, thus realizing the step-by-step and cascade utilization of the heat from the high-temperature flue gas. The blower then transports the flue gas, after releasing its heat, to the fine powder fuel feeder 5.

[0160] The temperature of the recirculated flue gas is maintained between 80℃ and 150℃. Firstly, this ensures the flue gas temperature remains above the dew point, preventing condensation, maintaining the stability of the transport medium's properties, which is beneficial for the stable operation of pneumatic conveying and ensures controllable pulverized coal concentration and flow rate. Secondly, it avoids thermal shock; the smaller temperature difference between the recirculated flue gas and the furnace means that when injected as a transport medium, it has less impact on localized combustion. Thirdly, it prevents high-temperature spontaneous combustion.

[0161] Optionally, a dust collector is also installed on the flue gas duct to reduce dust in the recirculated flue gas entering the fine powder fuel feeder 5.

[0162] This scheme establishes a dual-fuel supply mode of stable combustion in the lower bed layer and load adjustment by pulverized coal in the upper bed layer. By adjusting the proportion of pulverized coal in the feed, which is 5% to 50% of the total coal feed, the boiler load can be flexibly adjusted within a wide range without affecting the fluidization and stable combustion in the lower dense phase zone.

[0163] This scheme reduces the risk of slagging in the furnace by transferring part of the combustion load to the dilute phase zone in the upper part of the furnace, thereby reducing the heat load in the dense phase zone in the lower part and avoiding excessively high local temperatures.

[0164] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed, and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. The scope of this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described application concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A combustion method for rapid load adjustment in a circulating fluidized bed, characterized in that, include: Main fuel is supplied to the dense phase zone of the furnace of the circulating fluidized bed boiler (1); Fine pulverized fuel is transported through recirculated flue gas to a fine pulverized fuel supply pipe (3) nested within a secondary air duct (2). The recirculated flue gas provides power for the transport of pulverized coal. The outlet of the fine pulverized fuel supply pipe (3) is located at the secondary air inlet. The pneumatic transport of pulverized coal and the combustion air converge and coordinate at the secondary air inlet so that the secondary air in the secondary air duct (2) entrains the fine pulverized fuel into the dilute phase zone of the furnace. The proportion of pulverized coal fed is 5% to 50% of the total coal feed. According to the load adjustment requirements of the circulating fluidized bed boiler (1), the flow rates of the fine powder fuel, the secondary air and the recirculated flue gas are adjusted; the load adjustment requirements include increasing the load and decreasing the load. When the load increases, the flow rates of the fine fuel, the secondary air, and the recirculated flue gas are increased; When the load is reduced, the flow rates of the fine fuel powder and the secondary air are decreased, while the flow rate of the recirculated flue gas is increased. The flow rate ratio of the fine fuel powder, the secondary air, and the recirculated flue gas is 1:(2~8):(0.8~3), and the ratio of the velocity of the fine fuel powder jet to the velocity of the secondary air is 0.6~0.9; The embedment length of the fine powder fuel supply pipe (3) in the secondary air duct (2) is at least 5 times the diameter of the fine powder fuel supply pipe (3); And / or, the diameter ratio of the fine powder fuel supply pipe (3) to the secondary air pipe (2) is 0.15~0.

35.

2. The combustion method for rapid load adjustment in a circulating fluidized bed according to claim 1, characterized in that, Fine fuel is transported via recirculated flue gas to a fine fuel supply pipe (3) nested within a secondary air duct (2), specifically, The fine fuel bin (4) supplies fine fuel to the fine fuel feeder (5); The recirculated flue gas pipeline supplies the recirculated flue gas to the fine powder fuel feeder (5), so that the fine powder fuel and the recirculated flue gas are mixed to obtain a gas-solid two-phase flow of the fine powder fuel and the recirculated flue gas; The recirculated flue gas provides the power to transport the gas-solid two-phase flow, which is then transported through the transport pipeline (6) to the fine powder fuel supply pipe (3).

3. The combustion method for rapid load adjustment in a circulating fluidized bed according to claim 2, characterized in that, The fine fuel bin (4) supplies fine fuel to the fine fuel feeder (5), which includes grinding coarse fuel to obtain the fine fuel and then conveying the fine fuel to the fine fuel bin (4). The main fuel is supplied to the dense phase zone of the furnace of the circulating fluidized bed boiler (1), specifically, The main fuel is supplied to the dense phase region through the main fuel supply pipeline (7), which is independent of the fine powder fuel supply pipeline (3).

4. The combustion method for rapid load adjustment in a circulating fluidized bed according to claim 2, characterized in that, Before the recirculated flue gas is supplied to the fine powder fuel feeder (5) by the recirculated flue gas pipeline, the following are also included: Adjust the temperature of the recirculated flue gas to 80℃~150℃.

5. A system for rapid load adjustment in a circulating fluidized bed, characterized in that, The combustion method applicable to rapid load adjustment in a circulating fluidized bed as described in any one of claims 1-4; It includes a circulating fluidized bed boiler (1), a main fuel supply pipeline (7), a secondary air pipeline (2), and a fine powder fuel supply assembly; The main fuel supply pipeline (7) is connected to the dense phase zone of the furnace of the circulating fluidized bed boiler (1). The main fuel supply pipeline (7) is used to supply main fuel to the dense phase zone to achieve stable combustion. The fine fuel supply assembly includes a fine fuel feeder (5), a fine fuel supply pipe (3), and a recirculated flue gas pipeline (8). The recirculated flue gas pipeline (8) is connected to the fine powder fuel feeder (5). The recirculated flue gas pipeline (8) is used to supply recirculated flue gas into the fine powder fuel feeder (5) so that the recirculated flue gas is mixed with the fine powder fuel supplied into the fine powder fuel feeder (5) to obtain a gas-solid two-phase flow of the fine powder fuel and the recirculated flue gas. The outlet of the fine fuel feeder (5) is connected to the inlet of the fine fuel supply pipe (3) through the conveying pipeline (6). The recirculated flue gas provides conveying power for the gas-solid two-phase flow. The fine fuel supply pipe (3) is nested in the secondary air duct (2). The outlet of the fine fuel supply pipe (3) is located at the secondary air inlet so that the secondary air can entrain the fine fuel into the dilute phase region.

6. The system for rapid load adjustment of a circulating fluidized bed according to claim 5, characterized in that, It also includes a fine fuel bin (4) for supplying fine fuel to the fine fuel feeder (5).

7. The system for rapid load adjustment of a circulating fluidized bed according to claim 6, characterized in that, It also includes a coal mill (9) for grinding the main fuel to obtain fine powder fuel; The coal mill (9) is connected to the fine powder fuel bin (4).

8. The system for rapid load adjustment of a circulating fluidized bed according to any one of claims 5-7, characterized in that, The recirculated flue gas pipeline (8) includes a flue gas duct, a fan, a superheater, an economizer, and an air preheater; A superheater, economizer, air preheater, and fan are sequentially installed on the flue gas duct along the flue gas flow direction.

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