Peak shaving system and method for circulating fluidized bed boiler and circulating fluidized bed boiler

Abstract

The invention provides a peak shaving system and method for a circulating fluidized bed boiler and the circulating fluidized bed boiler, and relates to the technical field of power generation. The lower port of the ash cooling pipe is communicated with the upper side of the material return leg, and the upper port of the ash cooling pipe is connected with the first end of the ash cooling conveying line; an upper port of the hot ash pipe is communicated with the lower side of the material return leg, and the hot ash pipe is provided with a first adjusting valve; a first signal output end of the controller is connected with a control end of the cold ash conveying line, and a second signal output end of the controller is connected with the first regulating valve; the controller is used for controlling the opening degree of the first adjusting valve under the condition of load reduction, and the larger the load reduction degree is, the larger the opening degree of the first adjusting valve is; under the condition that the load is increased, the cold ash conveying line is controlled to operate, and the higher the load increasing degree is, the higher the circulating ash conveying speed of the cold ash conveying line is. Therefore, the stability of the boiler in the wide load interval is achieved, meanwhile, the circulating ash amount is actively adjusted, and the requirement for rapid peak regulation of the boiler is met.

Description

Technical Field

[0001] The present application relates to the field of power generation technology, and in particular to a circulating fluidized bed boiler peak-shaving system, method, and circulating fluidized bed boiler. Background Art

[0002] Circulating fluidized bed (CFB) boilers are widely used in coal-fired power generation due to their wide fuel adaptability, low pollutant emissions, and wide load regulation range. In recent years, driven by the "dual carbon" goals, CFB units have been required to frequently participate in deep peak regulation of the power grid to accommodate fluctuating renewable energy sources (such as wind power and photovoltaics).

[0003] However, when CFB units operate at low load, there are problems with unstable combustion and reduced energy efficiency, making it difficult for CFB units to operate stably for a long time at low load, restricting the CFB units' ability to perform deep peak regulation. When CFB units operate at high load, they are not safe and environmentally friendly, and the CFB units have a lagging load change rate, making them unable to respond to grid demand. Summary of the Invention

[0004] In view of this, the present application provides a circulating fluidized bed boiler peak-shaving system, method and circulating fluidized bed boiler, aiming to solve the problem that CFB units are difficult to meet the stable, safe, environmentally friendly and rapid peak-shaving requirements within a wide load range.

[0005] In a first aspect, the present application provides a circulating fluidized bed boiler peak shaving system, comprising a hot ash pipe, a cold ash pipe, and a controller;

[0006] The lower end of the cold ash pipe is connected to the upper side of the return leg, and the upper end of the cold ash pipe is connected to the first end of the cold ash conveying line; the upper end of the hot ash pipe is connected to the lower side of the return leg, and the hot ash pipe is equipped with a first regulating valve; the first signal output end of the controller is connected to the control end of the cold ash conveying line, and the second signal output end of the controller is connected to the first regulating valve;

[0007] The controller is used to control the opening of the first regulating valve when the load is reduced, and the greater the degree of load reduction, the greater the opening of the first regulating valve; and to control the operation of the cold ash conveying line when the load is increased, and the greater the degree of load increase, the faster the rate of transmission of circulating ash by the cold ash conveying line.

[0008] The above system also includes a cooling transmission line;

[0009] The first end of the cooling conveying line is connected to the lower port of the hot ash pipe, and the second end of the cooling conveying line and the second end of the cold ash conveying line are both connected to the ash storage bin; the cooling conveying line is used to convey the circulating ash output by the hot ash pipe and reduce the temperature of the circulating ash.

[0010] Optionally, the cold ash conveying line includes a feeder;

[0011] The input end of the feeder is arranged corresponding to the lower port of the ash storage bin, and the lower port of the ash storage bin outputs the circulating ash;

[0012] The output end of the feeder is arranged corresponding to the upper port of the first transmission pipeline, the lower port of the first transmission pipeline is connected to the upper port of the cold ash pipe, and a second regulating valve is provided on the first transmission pipeline.

[0013] Optionally, the cooling and conveying line includes a cooler and a bucket elevator;

[0014] The lower end of the hot ash pipe is connected to the input end of the cooler, the output end of the cooler is connected to the feeding end of the bucket elevator, and the output end of the bucket elevator is connected to the upper end of the storage bin.

[0015] Optionally, the controller is connected to the second regulating valve, the feeder, and the valve at the lower port of the storage bin, and the valve is used to control the conduction state of the lower port of the storage bin;

[0016] The controller is specifically configured to control the valve and the second regulating valve to open in response to a load increase instruction; and to control the transmission rate of the feeder transmitting the circulating ash according to the load increase degree indicated by the load increase instruction.

[0017] Optionally, the controller is further connected to the cooler and the bucket elevator;

[0018] The controller is specifically used to respond to a load reduction instruction, determine the diversion ratio of the hot ash pipe according to the load reduction degree indicated by the load reduction instruction; adjust the opening of the first regulating valve according to the diversion ratio; and control the opening of the cooler and the bucket elevator.

[0019] Optionally, the temperature of the circulating ash output from the ash storage bin does not exceed a preset temperature;

[0020] The ash storage bin is equipped with a material level detector and a nitrogen protection device.

[0021] Optionally, the inner material of the cold ash tube and the inner material of the hot ash tube are ceramic.

[0022] In a second aspect, the present application provides a peak shaving method for a circulating fluidized bed boiler, the method comprising: controlling the opening of a first regulating valve in a load reduction situation, wherein the greater the load reduction, the greater the opening of the first regulating valve; the first regulating valve is disposed on a hot ash pipe, and the upper end of the hot ash pipe is connected to the lower side of a return leg;

[0023] When the load is increased, the operation of the cold ash conveying line is controlled. The greater the degree of load increase, the faster the transmission rate of the cold ash conveying line. The first end of the cold ash conveying line is connected to the upper port of the cold ash pipe, and the lower port of the cold ash pipe is connected to the upper side of the return leg.

[0024] In a third aspect, the present application provides a circulating fluidized bed boiler, which adopts a circulating fluidized bed boiler peak-shaving system as described in any one of the above.

[0025] The present application provides a circulating fluidized bed boiler peak-shaving system, method and circulating fluidized bed boiler. The peak-shaving system in the present application is a system in which a cold ash pipe is connected to the upper side of the return leg of the boiler, and a hot ash pipe is connected to the lower side. Furthermore, the cold ash pipe is connected to a cold ash conveying line for adding circulating ash into the boiler through the return leg when the load is increased. After the circulating ash is added, the amount of circulating ash in the furnace increases rapidly, and the heat transfer between the circulating ash and the water-cooled wall and the screen-type heating surface in the furnace is enhanced, so that the evaporation amount and steam temperature increase rapidly, and the boiler load increase rate increases; especially when the load is further increased under high load conditions, the ash concentration in the dilute phase zone increases rapidly, the heat transfer coefficient increases, and the temperature of the dense phase zone is reduced, which can reduce the amount of NOx generated, improve safety and environmental protection, and improve the high-load operation capacity of the boiler. When load reduction is necessary, the hot ash pipe is equipped with a first regulating valve, connected to the lower side of the return leg. This valve can divert the circulating ash in the return leg. By diverting some of the circulating ash, the amount of circulating ash returning to the boiler is reduced, reducing the amount of circulating ash remaining in the furnace. Heat transfer between the circulating ash and the water-cooled walls and the screen-type heating surfaces within the furnace is weakened, rapidly reducing the evaporation rate and steam temperature, and increasing the boiler's load reduction rate. Especially when further reducing the load at low load, by diverting some of the circulating ash, the amount of ash returning to the furnace is reduced, increasing the combustion share of the dense phase zone, raising the dense phase bed temperature and boiler combustion efficiency, and improving the stability of the boiler's low-power operation. Simultaneously, the desulfurization reaction temperature is increased, the molar ratio of calcium (Ca) to sulfur (S) is reduced, reducing limestone consumption and improving economic efficiency. This achieves boiler stability across a wide load range. At the same time, the aforementioned system actively adjusts the circulating ash volume to meet the boiler's rapid peak-shaving needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the following briefly introduces the drawings required for use in the embodiment or the prior art description. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic structural diagram of a circulating fluidized bed boiler peak-shaving system provided in an embodiment of the present application;

[0028] Figure 2 A schematic flow chart of a circulating fluidized bed boiler load raising method provided in an embodiment of the present application;

[0029] Figure 3 A schematic flow chart of a circulating fluidized bed boiler load reduction method provided in an embodiment of the present application.

[0030] Description of the accompanying figures

[0031] 1-cold ash pipe; 2-hot ash pipe; 3-first regulating valve; 4-second regulating valve; 5-circulating material conveyor; 6-storage silo; 7-bucket elevator; 8-cooler. DETAILED DESCRIPTION

[0032] Currently, circulating fluidized bed (CFB) boilers are widely used in coal-fired power generation. In recent years, driven by the "dual carbon" goals, CFB units have frequently been required to participate in deep peak-shaving operations on the power grid to accommodate fluctuating renewable energy sources (such as wind power and photovoltaics). However, existing technologies still face several bottlenecks in peak-shaving operations across multiple scenarios. These include poor stability at low loads, which limits the depth of peak-shaving; insufficient safety and environmental performance at high loads; and delayed load-variation rates, which limit the ability to respond to grid demand.

[0033] The specific manifestation of this problem, particularly poor low-load operational stability, limits the depth of peak shaving. Existing CFB boilers can operate stably between 30% and 100% load under conventional combustion conditions. However, when the load drops below 30%, the bed temperature in the dense phase region of the furnace drops significantly due to a sharp decrease in fuel input, dropping below 800°C, sometimes even below 700°C. This decreases the combustion reaction rate, easily leading to unstable combustion and even the risk of fire extinguishing. Furthermore, desulfurization efficiency decreases, limestone consumption increases, and unit energy efficiency declines. This severely restricts the deep peak shaving capabilities of CFB units, making them unable to meet the requirements of new power systems for coal-fired power units to operate stably and for extended periods at lower loads (e.g., below 20%).

[0034] The specific manifestation of insufficient safety and environmental protection under high-load conditions is that, under high-load operation (for example, exceeding 80% load), the increased fuel input to the dense phase zone leads to a sharp increase in the heat load of the dense phase cross-section, raising the bed temperature, which can easily exceed 950°C. This high dense phase bed temperature is prone to local overheating, causing coking and threatening the safe operation of the boiler. Furthermore, the increased bed temperature exacerbates the generation of fuel- and thermal-type NOx, increasing the original emission concentration, leading to increased denitrification costs and ammonia slip, decreased desulfurization efficiency, and increased limestone consumption. Furthermore, based on this, to avoid localized excessive bed temperatures at high loads, the load ramp rate needs to be reduced to ensure that the bed temperature does not exceed the limit, resulting in a slow load ramp rate.

[0035] The specific manifestations of the problem of delayed load change rate and insufficient ability to respond to grid demand are that, due to the heat storage characteristics of a large amount of refractory castables, bed material and circulating ash in the furnace of a CFB boiler, its thermal inertia is significantly higher than that of a pulverized coal boiler. Consequently, when the fuel input is reduced, the release of stored heat delays the decrease in bed temperature and steam parameters, resulting in a delayed load response and difficulty in meeting the grid's rapid load reduction instructions (such as a load change rate of 2%-5% per minute). At the same time, the load increase is limited. After the coal feed is rapidly increased to increase the load, the heat released by combustion in the dense phase increases, and the heat cannot be quickly and effectively transferred to the heating surface in the dilute phase. Therefore, the steam parameters increase slowly and the load increase rate is slow. This results in the problem of delayed load change rate in frequent load change scenarios.

[0036] Based on the above issues, the inventors considered that the material circulation of CFB boilers is a key factor influencing the gas-solid flow, heat and mass transfer characteristics within the furnace. The wide-screened material particle size distribution results in differences in the combustion fraction within the CFB boiler under various loads. Recirculating ash, a key heat transfer medium within the furnace, significantly affects the material concentration in different spatial domains within the furnace and the distribution of heat transfer fractions among the heating surfaces. The heat transfer coefficient of a CFB boiler is positively correlated with the circulating ash concentration. However, current CFB boilers cannot actively adjust the circulating ash content, nor can they dynamically adjust the heat transfer ratio between the dilute and dense phases within the boiler.

[0037] Based on this, the present application proposes a circulating fluidized bed boiler peak-shaving system, method and circulating fluidized bed boiler. Specifically, the system includes a hot ash pipe 2, a cold ash pipe 1 and a controller; the lower port of the cold ash pipe 1 is connected to the upper side of the return leg, and the upper port of the cold ash pipe 1 is connected to the first end of the cold ash conveying line; the upper port of the hot ash pipe 2 is connected to the lower side of the return leg, and the hot ash pipe 2 is equipped with a first regulating valve 3; the first signal output end of the controller is connected to the control end of the cold ash conveying line, and the second signal output end of the controller is connected to the first regulating valve 3; the controller is used to control the opening of the first regulating valve 3 when the load is reduced, and the greater the degree of load reduction, the greater the opening of the first regulating valve 3; and to control the operation of the cold ash conveying line when the load is increased, and the greater the degree of load increase, the faster the transmission rate of the cold ash conveying line.

[0038] In this way, the controller controls the hot ash pipe 2 to divert the circulating ash from the return leg during load reduction, while the cold ash pipe 1 increases the circulating ash flow to the boiler during load increase. Furthermore, at low loads, by diverting some of the circulating ash, the amount of ash returning to the furnace is reduced, increasing the dense phase combustion share by approximately 15%, raising the dense phase bed temperature by 50-80°C, and improving boiler combustion efficiency by over 2%. This resolves the aforementioned issue of unstable boiler operation at low loads, which limits peak-shaving depth. Furthermore, the desulfurization reaction temperature is increased, the Ca / S molar ratio is reduced, and limestone consumption is reduced, improving both economic efficiency and environmental performance. At high loads, the low-temperature circulating ash can be transported to the furnace, rapidly increasing the dilute phase ash concentration and improving the heat transfer coefficient by 30%-50%. This approach can reduce the dense phase temperature by approximately 50°C, keeping it below 900°C, and reducing NOx generation to below 150 mg / Nm³, thus addressing the aforementioned safety and environmental issues at high loads. Moreover, the relationship between the boiler evaporation capacity Q and the circulating ash capacity G can be simplified as Q=K·G·ΔT, where ΔT is the temperature difference. In traditional systems, the circulating ash capacity G is not adjustable, and the change of ΔT lags behind the adjustment of the fuel capacity. However, when the load is changed in this application, the heat transfer coefficient and evaporation capacity are directly changed by quickly increasing or decreasing the circulating ash capacity, for example, increasing / decreasing the ash capacity by 20% within 5 minutes. The immediate effect of ash capacity adjustment on heat transfer is achieved, and its response time is <30 seconds, rather than relying on slow changes in bed temperature. In this way, the material concentration in the furnace is quickly adjusted through the circulating ash storage system, the heat exchange in the furnace is quickly changed, the load change rate is improved, and the problem of load change lag in the existing system is solved.

[0039] In order to be able to understand the features and technical content of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The accompanying drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the sake of convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, to simplify the drawings, well-known structures and devices can be simplified for display.

[0040] In the description and claims of the embodiments of the present disclosure, as well as in the accompanying drawings, the terms "first," "second," and the like are used to distinguish similar items and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate to describe the embodiments of the present disclosure herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions.

[0041] Unless otherwise specified, the term "plurality" means two or more. In the disclosed embodiments, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B. The term "and / or" describes an association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0043] See also Figure 1 , Figure 1 A schematic structural diagram of a circulating fluidized bed boiler peak-shaving system provided in an embodiment of the present application, comprising: a hot ash pipe 2, a cold ash pipe 1, and a controller;

[0044] The lower port of the cold ash pipe 1 is connected to the upper side of the return leg, and the upper port of the cold ash pipe 1 is connected to the first end of the cold ash conveying line; the upper port of the hot ash pipe 2 is connected to the lower side of the return leg, and the hot ash pipe 2 is equipped with a first regulating valve 3; the first signal output end of the controller is connected to the control end of the cold ash conveying line, and the second signal output end of the controller is connected to the first regulating valve 3.

[0045] The above-mentioned return leg can be an inclined pipeline connecting the return valve at the bottom of the CFB boiler separator or the output end of the S-shaped pipeline and the bottom of the boiler furnace. The inclination direction of the return leg is that the end connected to the separator is higher and the end connected to the boiler furnace is lower.

[0046] Optional, such as Figure 1 The hot ash pipe 2 is welded to the underside of the return leg. It is connected close to the return leg. It can be made of high-temperature-resistant stainless steel with an inner inlay of wear-resistant ceramic tubes. It has an inner diameter of 200 mm and a temperature resistance of ≥1000°C. It is specifically used to divert circulating ash from the return leg without disrupting the pressure balance of the CFB external circulation.

[0047] Optionally, the cold ash pipe 1 is an ash delivery pipeline welded on the upper side of the return leg, which is used to re-inject circulating ash into the return pipe. The lining of the cold ash pipe 1 can also be made of wear-resistant ceramic to increase its service life.

[0048] Optionally, the opening range of the first regulating valve 3 can be 0-100%, with a control accuracy of ±1%, supporting DCS remote adjustment, and being able to accurately divert 0%-50% of the ash from the return leg through opening adjustment.

[0049] The controller is used to control the opening of the first regulating valve 3 when the load is reduced, and the greater the degree of load reduction, the greater the opening of the first regulating valve 3; and to control the operation of the cold ash conveying line when the load is increased, and the greater the degree of load increase, the faster the rate of transmission of circulating ash by the cold ash conveying line.

[0050] Optionally, the controller can utilize a DCS control system, acquiring signals such as bed temperature and load commands in real time through an I / O module. Based on the load command (a load increase or load decrease command generated based on actual production needs, such as a command configured based on the power grid's deep peak-shaving requirements), the cold ash conveying line can be adjusted to increase the boiler's circulating ash volume and increase the load. The opening of the first regulating valve 3 can also be adjusted; a larger opening increases the amount of circulating ash diverted from the return leg, thereby reducing the boiler's circulating ash volume and reducing the load.

[0051] Based on the above system, during low-load combustion, this application forces heat to remain in the dense phase by diverting circulating ash, raising the bed temperature to the optimal desulfurization temperature window (850-900°C), achieving stable combustion and efficient desulfurization, and improving low-load combustion stability. During high-load combustion, low-temperature circulating ash injection enhances dilute-phase heat transfer, suppresses overheating in the dense phase, and reduces NOx generation at the source. Furthermore, the controller dynamically adjusts the circulating ash to change the heat transfer coefficient, achieving rapid response to evaporation rate and steam temperature, and improving the variable load rate. In this way, this application uses an external independent system to actively divert and inject circulating ash for rapid bidirectional adjustment, achieving real-time optimization of combustion and heat transfer within the furnace. This application simultaneously addresses combustion stability, coking suppression, NOx control, and variable load rate issues through a single control variable (circulating ash volume), avoiding the coupled interference associated with traditional multi-parameter adjustments. In addition, compared with taking materials directly from the bottom of the separator, the above-mentioned method of taking materials from the side opening of the return leg in this application does not destroy the original pressure balance of the return material from the bottom of the boiler separator to the boiler, does not affect the stability of the circulation loop of the boiler circulating ash, and ensures the safety and reliability of the circulating ash diversion process system.

[0052] Based on the above embodiment, the above system also includes a cooling conveying line, the first end of the cooling conveying line is connected to the lower port of the hot ash pipe 2, and the second end of the cooling conveying line and the second end of the cold ash conveying line are both connected to the ash storage bin; the cooling conveying line is used to convey the circulating ash output by the hot ash pipe and reduce the temperature of the circulating ash.

[0053] Optionally, the capacity of the storage bin 6 is not less than 100 tons to achieve the storage of the circulating ash.

[0054] Optionally, the temperature of the circulating ash output from the ash storage bin does not exceed 50 degrees Celsius, thereby ensuring that the cold ash conveying line can convey the cold ash more safely and reliably, avoiding problems such as agglomeration.

[0055] Optionally, the ash storage bin can be equipped with a material level detector and a nitrogen protection device.

[0056] During load reduction, the cooling conveying line transports the diverted hot ash to the ash storage bin. Subsequently, when the load needs to be increased, the circulating ash in the storage bin 6 can be transported to the cold ash pipe 1 via the cold ash conveying line and then fed into the boiler through the cold ash pipe 1. In this way, the circulating ash is stored as a heat transfer medium, breaking through the rigid heat storage constraints within the boiler and achieving spatiotemporal heat redistribution. During load reduction, the diverted ash volume reduces the heat exchange in the dilute phase, forcing heat to remain in the dense phase. During load increase, the rapid injection of cold ash enhances heat exchange in the dilute phase, while suppressing overheating of the dense phase bed temperature, achieving thermal inertia decoupling.

[0057] Based on the above embodiment, see Figure 1 For increased load, the above-mentioned cold ash conveying line may include a feeder, the input end of the feeder is arranged corresponding to the lower port of the ash storage bin, and the lower port of the ash storage bin outputs circulating ash; the output end of the feeder is arranged corresponding to the upper port of the first transmission pipeline, the lower port of the first transmission pipeline is connected to the upper port of the cold ash pipe 1, and the first transmission pipeline is provided with a second regulating valve 4.

[0058] Optionally, the first transmission pipeline and the cold ash pipe 1 can be a unified pipeline or independent pipelines.

[0059] In one example, the feeder is a circulating material conveyor 5, and the loading end of the transmission crawler of the circulating material conveyor 5 is set corresponding to the lower port of the ash storage bin, and the lower port of the ash storage bin outputs the circulating ash; the discharge end of the transmission crawler of the circulating material conveyor 5 is set corresponding to the upper port of the first transmission pipeline, and the lower port of the first transmission pipeline is connected to the upper port of the cold ash pipe 1, and the first transmission pipeline is provided with a second regulating valve 4.

[0060] Optionally, the weighing type circulating material conveyor 5 is used to weigh the amount of circulating ash conveyed and quickly convey the circulating ash in the storage bin 6 to the furnace of the boiler, and the output can reach 80 tons per hour.

[0061] Optionally, the weighing-type circulating material conveyor 5 can achieve a circulating ash conveying rate of 0.5-1.5 tons per minute according to the adjustment of the controller.

[0062] Alternatively, the second regulating valve 4 can be a regulating valve whose opening is adjustable by a controller, and can be adjusted in conjunction with the conveying rate of the weighing-type circulating material conveyor 5. Of course, a regulating valve with an opening and closing function can also be directly used, and the second regulating valve 4 can be controlled to open when the circulating ash needs to be injected, and closed when the circulating ash does not need to be injected.

[0063] It can be understood that when the load is increased, the first regulating valve 3 has been closed by the controller at the end of the most recent load reduction.

[0064] The amount of diverted circulating ash is accurately adjusted through the first control valve, and the injection amount of cold circulating ash is accurately adjusted through the circulating material conveyor 5, and the injection rate is large, thereby realizing precise intelligent control of the system.

[0065] In another example, the good fluidity of the circulating ash can also be utilized, and the feeder can also adopt a large-flow rotary feeder, and the amount of injected circulating ash can be controlled by adjusting the rotation speed of the large-flow rotary feeder.

[0066] Furthermore, the controller can be specifically used to control the opening of the valve and the second regulating valve 4 in response to a load increase instruction; and control the transmission rate of the circulating material conveyor 5 according to the load increase degree indicated by the load increase instruction.

[0067] To control the bed temperature under high load, the material stored in the circulating ash bin is fed into the furnace via a weighing-type circulating ash conveyor. This rapidly increases the concentration of circulating ash within the furnace, which in turn increases the heat transfer coefficient between the circulating ash and the water-cooled walls. This increased heat transfer coefficient allows more heat to be transferred to the water-cooled walls quickly. This continuous heat transfer from the circulating ash draws more heat from the lower, high-temperature dense phase zone into the upper, dilute phase zone, where it is transferred to the furnace water-cooled walls and platen heating surfaces. This lowers the bed temperature in the dense phase zone, preventing localized overheating and coking, and improving the stability of high-load boiler operation. Simultaneously, the dilute phase zone heat transfer capacity is enhanced, increasing evaporation, lowering the furnace outlet flue gas temperature, and reducing heat absorption by the tail convection heating surfaces. This lowers the main steam temperature, reduces overheating of the heating surface tubes, and enhances boiler operational safety. Furthermore, the furnace temperature is brought closer to the optimal desulfurization temperature, further improving desulfurization efficiency. Furthermore, the lowered temperature in the dense phase zone reduces initial NOx generation, improving environmental performance.

[0068] In one example, see Figure 1For load reduction, the above-mentioned cooling and conveying line includes a cooler 8 and a bucket elevator 7; the lower port of the hot ash pipe 2 is connected to the input end of the cooler 8, the output end of the cooler 8 is connected to the feeding end of the bucket elevator 7, and the output end of the bucket elevator 7 is connected to the upper port of the storage bin 6.

[0069] Optionally, the cooler 8 can be a drum-type countercurrent heat exchanger, which uses cooling water to reduce the circulating ash temperature to below 50°C, with an output rate of 25 tons per hour. In this way, the circulating ash is cooled to ensure the safety of its storage and transportation.

[0070] Optionally, the transmission rate of the bucket elevator 7 can be the same as the transmission rate of the cooler 8, and is used to lift the cooled circulating ash and add it to the storage bin 6, so that the storage bin 6 can seal the filled circulating ash at low temperature.

[0071] In this way, hot ash is difficult to transport, store and measure, and is prone to agglomeration. Through the cooling and conveying line of this application, the circulating ash is cooled to below a preset temperature (for example, fifty degrees Celsius) before being transported and stored, thereby improving safety and operational reliability.

[0072] Furthermore, the controller is specifically used to respond to a load reduction instruction, determine the diversion ratio of the hot ash pipe 2 according to the load reduction degree indicated by the load reduction instruction; adjust the opening of the first regulating valve 3 according to the diversion ratio; and control the opening of the cooler 8 and the bucket elevator 7.

[0073] It is understandable that when the load is reduced, the components on the cold ash conveying line (such as the second regulating valve 4, the circulating material conveyor 5 and the valve of the ash storage bin) have been closed by the controller at the end of the most recent load increase.

[0074] Thus, when the boiler is reduced to a low load, in order to increase the bed temperature to avoid flameout or incomplete combustion, the controller can control the opening of the first regulating valve 3, allowing a portion of the circulating ash material in the return leg to enter the cooling conveying line and exchange heat with the circulating water in the cooler 8. The cooled circulating ash is finally conveyed to the circulating storage bin 6 via the bucket elevator 7. This reduces the concentration of fine particulate material in the furnace, thereby reducing the amount of heat transported to the dilute phase zone in the furnace, reducing the proportion of heat generated by combustion in the dense phase zone that is carried into the dilute phase zone, and increasing the bed temperature in the dense phase zone, thereby improving the stability of the boiler's low-load operation. At the same time, the increased bed temperature in the dense phase zone brings the desulfurization in the boiler furnace closer to the optimal reaction temperature, improving desulfurization efficiency and enhancing environmental protection.

[0075] Based on the above embodiments, the beneficial effects of this application include:

[0076] 1. This system improves low-load combustion stability. Specifically, by diverting 0-50% of the circulating ash to an external ash storage bin, the amount of ash recirculating back to the furnace is reduced, the furnace material concentration is lowered, and the amount of fine particles carried by the primary air is reduced. This reduces the heat load in the dilute phase, thereby reducing the heat exchange rate of the evaporating heating surface, decreasing the main steam flow rate, and rapidly reducing the load. At the same time, the increased heat retained in the dense phase increases the temperature of this region, increasing the combustion share in the dense phase from 60% to 75% and the bed temperature from 780°C to 850°C, reaching the optimal desulfurization temperature window. This improves combustion and desulfurization efficiency, reduces desulfurization costs, and saves money.

[0077] 2. This system can improve the safety and environmental protection of high-load operation. Specifically, this application increases the ash concentration in the dilute phase zone and the heat exchange capacity in the dilute phase zone by quickly injecting cold circulating ash into the furnace, so that the heat brought into the dilute phase zone by the dense phase zone increases and the retained heat decreases, thereby slowing down the bed temperature rise, avoiding high operating temperatures in the dense phase zone of the boiler, reducing the probability of coking during high-load operation, and improving the safety of high-load operation. At the same time, the temperature in the dense phase zone drops, destroying the NOx generation conditions, inhibiting the generation of thermal NOx, reducing the cost of denitrification, and avoiding the problem of increased carbon content in fly ash and increased energy consumption caused by traditional methods such as increasing the primary air volume.

[0078] 3. Increased load rate. Specifically, the circulating ash path formed by the return leg connecting the hot ash pipe 2, the hot ash conveying line, the storage bin 6, the cold ash conveying line, and the cold ash pipe 1 connected to the return leg can achieve load reduction by diversion and load increase by ash injection. The diversion rate and the ash injection rate can be adjusted to achieve two-way dynamic regulation of the increase and decrease of the circulating ash amount in the boiler, thereby making the furnace heat transfer coefficient h=α×G 0.8 (α is a coefficient with a value of 0.35; G is the ash concentration). Rapid changes in heat absorption by the evaporating heating surface immediately respond to this change, adjusting the main steam flow rate to increase the load by 2.5% / min and decrease the load by 2% / min. This direct regulation of ash circulation through the external system achieves thermal inertia decoupling, avoiding the delayed response associated with traditional solutions like split-compartment coal feeding, which require coordinated fuel and air flow.

[0079] 4. Improved economic efficiency. Specifically, by regulating heat transfer through circulating ash, the rigid constraints of heat storage within the furnace are overcome. Ash can be allocated on demand, avoiding the "load lag" (typical delay >5 minutes) caused by heat storage inertia in traditional CFBs. This improves variable load capacity, extends annual peak-shaving time, and increases peak-shaving revenue.

[0080] Based on the above system structure, the present application also provides a peak-shaving method for a circulating fluidized bed boiler, the peak-shaving method comprising:

[0081] In the case of load reduction, the opening of the first regulating valve 3 is controlled. The greater the degree of load reduction, the greater the opening of the first regulating valve 3. The first regulating valve 3 is arranged on the hot ash pipe 2, and the upper end of the hot ash pipe 2 is connected to the lower side of the return leg.

[0082] When the load is increased, the operation of the cold ash conveying line is controlled. The greater the load increase, the faster the transmission rate of the cold ash conveying line. The first end of the cold ash conveying line is connected to the upper port of the cold ash pipe 1, and the lower port of the cold ash pipe 1 is connected to the upper side of the return leg.

[0083] Based on the above method, when the CFB boiler in this application reduces load, the amount of circulating ash returned to the furnace bottom reduces the concentration of fine particulate matter in the furnace. This reduces the cross-sectional heat load of the space domain within the dilute phase zone of the furnace, which is transported by the primary air. The heat exchange rate of each heating surface in the dilute phase zone decreases, rapidly reducing the main steam flow rate and steam temperature, and thus rapidly reducing the boiler load. When the load is increased, the circulating ash is increased and returned to the furnace bottom, increasing the concentration of fine particulate matter in the furnace, effectively increasing the combustion share of the CFB dilute phase zone and the heat exchange rate of each heating surface. Therefore, the feedwater rate can be increased, thereby increasing the main steam flow rate, while ensuring that the main steam does not overheat, ultimately increasing the boiler load increase rate.

[0084] In one specific example, see Figure 2 The flow diagram of a circulating fluidized bed boiler load increasing method shown in FIG. A circulating fluidized bed boiler load increasing method may specifically include:

[0085] S201, in response to a load increase instruction, controlling the discharge valve of the storage bin 6 to open, and controlling the second regulating valve 4 to open.

[0086] S202: Calculate the transmission rate of the feeder transmitting the circulating ash according to the load increase level indicated by the load increase instruction.

[0087] It can be understood that the degree of load increase is proportional to the transmission rate.

[0088] S203 , starting the feeder according to the transmission rate to transport the circulating ash to the cold ash pipe 1 at the transmission rate.

[0089] This rapidly increases the ash concentration in the dilute phase zone, improving heat exchange. This in turn rapidly increases boiler evaporation, boosts main steam flow, and increases the load rate to 2.5% / min. The dense phase temperature drops below 900°C, enhancing boiler operation safety. Simultaneously, the furnace temperature approaches the optimal desulfurization temperature, further improving desulfurization efficiency. Furthermore, the lowered dense phase temperature reduces initial NOx generation.

[0090] In one specific example, see Figure 3A flow chart of a circulating fluidized bed boiler load reduction method is shown. A circulating fluidized bed boiler load reduction method may specifically include:

[0091] S301, in response to a load reduction instruction, determining the diversion ratio of the hot ash pipe 2 according to the load reduction degree indicated by the load reduction instruction;

[0092] S302 : Determine the opening of the first regulating valve 3 according to the diversion ratio adjustment.

[0093] It can be understood that the degree of load reduction is proportional to the diversion ratio, and the diversion ratio is proportional to the opening of the first regulating valve 3.

[0094] S303 , adjusting the opening of the first regulating valve 3 according to the diversion ratio, controlling the cooler 8 and the bucket elevator 7 to open, so that the circulating ash passes through the cooling zone of the cooler 8 and is transported by the bucket elevator 7 to be stored in the storage bin 6 .

[0095] In this way, the circulating ash concentration in the dilute phase zone decreases rapidly, the combustion share in the dense phase zone increases, the bed temperature rises to 850°C, the desulfurization effect is improved, and the boiler operation is more stable; and the heat transfer in the dilute phase zone is reduced, the boiler evaporation volume decreases, and the load reduction rate can reach 2% / min.

[0096] The embodiments of the present application also provide a circulating fluidized bed boiler and a computer storage medium for implementing the solution provided in the embodiments of the present application.

[0097] Among them, a circulating fluidized bed boiler adopts a circulating fluidized bed boiler peak-shaving system described in any one of the above.

[0098] The computer storage medium stores codes. When the codes are executed, the device executing the codes implements the peak-shaving method for a circulating fluidized bed boiler described in any embodiment of the present application.

[0099] The “first” and “second” in the names such as “first” and “second” (if any) mentioned in the embodiments of this application are only used as name identifiers and do not mean the first or second in order.

[0100] Through the description of the above embodiments, it can be seen that those skilled in the art can clearly understand that all or part of the steps in the above-mentioned embodiment methods can be implemented by means of software plus a general hardware platform. Based on this understanding, the technical solution of the present application can be embodied in the form of a software product. The computer software product can be stored in a storage medium, such as a read-only memory (ROM) / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network communication device such as a router) to execute the methods described in various embodiments or certain parts of the embodiments of the present application.

[0101] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiment. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment. Those of ordinary skill in the art can understand and implement it without paying any creative work.

[0102] The above description is merely an exemplary embodiment of the present application and is not intended to limit the scope of protection of the present application.

Claims

1. A circulating fluidized bed boiler peak shaving system, characterized in that: Including hot ash pipe, cold ash pipe and controller; The lower end of the cold ash pipe is connected to the upper side of the return leg, and the upper end of the cold ash pipe is connected to the first end of the cold ash conveying line; the upper end of the hot ash pipe is connected to the lower side of the return leg, and the hot ash pipe is equipped with a first regulating valve; the first signal output end of the controller is connected to the control end of the cold ash conveying line, and the second signal output end of the controller is connected to the first regulating valve; The controller is used to control the opening of the first regulating valve when the load is reduced, and the greater the degree of load reduction, the greater the opening of the first regulating valve; and to control the operation of the cold ash conveying line when the load is increased, and the greater the degree of load increase, the faster the rate of transmission of circulating ash by the cold ash conveying line.

2. The system according to claim 1, characterized in that It also includes cooling transmission lines; The first end of the cooling conveying line is connected to the lower port of the hot ash pipe, and the second end of the cooling conveying line and the second end of the cold ash conveying line are both connected to the ash storage bin; the cooling conveying line is used to convey the circulating ash output by the hot ash pipe and reduce the temperature of the circulating ash.

3. The system according to claim 2, characterized in that The cold ash conveying line includes a feeder; The input end of the feeder is arranged corresponding to the lower port of the ash storage bin, and the lower port of the ash storage bin outputs the circulating ash; The output end of the feeder is arranged corresponding to the upper port of the first transmission pipeline, the lower port of the first transmission pipeline is connected to the upper port of the cold ash pipe, and a second regulating valve is provided on the first transmission pipeline.

4. The system according to claim 2, wherein: The cooling and conveying line includes a cooler and a bucket elevator; The lower end of the hot ash pipe is connected to the input end of the cooler, the output end of the cooler is connected to the feeding end of the bucket elevator, and the output end of the bucket elevator is connected to the upper end of the storage bin.

5. The system according to claim 3, wherein: The controller is connected to the second regulating valve, the feeder, and the valve at the lower port of the storage bin, and the valve is used to control the conduction state of the lower port of the storage bin; The controller is specifically configured to control the valve and the second regulating valve to open in response to a load increase instruction; and to control the transmission rate of the feeder transmitting the circulating ash according to the load increase degree indicated by the load increase instruction.

6. The system according to claim 4, characterized in that The controller is also connected to the cooler and the bucket elevator; The controller is specifically used to respond to a load reduction instruction, determine the diversion ratio of the hot ash pipe according to the load reduction degree indicated by the load reduction instruction; adjust the opening of the first regulating valve according to the diversion ratio; and control the opening of the cooler and the bucket elevator.

7. The system according to any one of claims 1 to 6, characterized in that: The temperature of the circulating ash output from the ash storage bin does not exceed a preset temperature; The ash storage bin is equipped with a material level detector and a nitrogen protection device.

8. The method according to claim 1, characterized in that The inner material of the cold ash pipe and the inner material of the hot ash pipe are ceramic.

9. A peak load regulation method for a circulating fluidized bed boiler, characterized in that: In the case of load reduction, the opening of the first regulating valve is controlled. The greater the degree of load reduction, the greater the opening of the first regulating valve. The first regulating valve is arranged on the hot ash pipe, and the upper end of the hot ash pipe is connected to the lower side of the return leg. When the load is increased, the operation of the cold ash conveying line is controlled. The greater the degree of load increase, the faster the transmission rate of the cold ash conveying line. The first end of the cold ash conveying line is connected to the upper port of the cold ash pipe, and the lower port of the cold ash pipe is connected to the upper side of the return leg.

10. A circulating fluidized bed boiler, characterized in that: A circulating fluidized bed boiler peak shaving system according to any one of claims 1 to 8 is used.

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