Fire banking operation method of circulating fluidized bed boiler

Abstract

The invention discloses a banking fire operation method of a circulating fluidized bed boiler, which relates to the technical field of combustion equipment, is applied to the circulating fluidized bed boiler, and comprises the following steps: in a banking fire preparation stage, increasing the thickness of a bed material from a first thickness to a second thickness, and according to the coking characteristic of banking fire fuel, increasing the thickness of the bed material from the first thickness to the second thickness; gradually increasing the bed temperature from the first temperature to a second temperature; wherein the second thickness is 100 to 300 mm higher than the first thickness; and in the banking fire stage, a fan system assembly in the circulating fluidized bed boiler is shut down, a steam-water system assembly is operated, and it is ensured that a sealing assembly in the circulating fluidized bed boiler is completely closed after the fan system assembly stops rotating. By adopting the method, the banking-up time and the service life of the furnace wall can be effectively prolonged, and the success probability of fire raising is improved.

Description

Technical Field

[0001] The invention relates to the technical field of combustion equipment, and in particular to a pressure-fire operation method of a circulating fluidized bed boiler. Background Art

[0002] In the related art, the ignition time of small and medium-sized circulating fluidized bed industrial boilers is short (generally less than 8 hours). When the boiler needs to be ignited for a long time (greater than 12 hours), it is necessary to use an auxiliary burner to successfully start the boiler. The auxiliary burner fuel is generally diesel or natural gas, which increases the fuel cost of the boiler. On the other hand, when the boiler is in a ignition state for a long time, the temperature of the furnace bed will gradually decrease, resulting in a large temperature difference between the cold state and the hot state, causing the dense phase area furnace wall to deform, affecting the service life of the furnace wall. Summary of the invention

[0003] Based on this, it is necessary to provide a pressure-fire operation method for a circulating fluidized bed boiler that can effectively prolong the pressure-fire time and the service life of the furnace wall in order to address the above technical problems.

[0004] A method for operating a circulating fluidized bed boiler under reduced pressure, applied to the circulating fluidized bed boiler, the method comprising:

[0005] In the ignition preparation stage, the bed material thickness is increased from a first thickness to a second thickness, and the bed temperature is gradually increased from a first temperature to a second temperature according to the coking characteristics of the ignition fuel; wherein the second thickness is 100-300 mm higher than the first thickness;

[0006] During the fire suppression stage, the fan system components in the circulating fluidized bed boiler are shut down and the steam-water system components are operated, and after the fan system components stop rotating, it is ensured that the sealing components in the circulating fluidized bed boiler are completely sealed.

[0007] In the above scheme, the compressed fire fuel is a biomass fuel with a moisture content of less than 10%, a fixed carbon content of more than 15%, and a low calorific value of more than 2300 kcal / kg.

[0008] In the above scheme, the method further comprises:

[0009] In the ignition preparation stage, the amount of ignition fuel is increased.

[0010] In the above scheme, the shutdown sequence of the fan system components is: stop feeding, shut down the feeding sealing fan, stop the secondary fan and close the secondary air door, shut down the primary fan, shut down the induced draft fan, and shut down the return fan;

[0011] The operating sequence of the steam-water system components is: shut down the feedwater pump, open the economizer recirculation valve, and close the main steam valve.

[0012] In the above scheme, the method further comprises:

[0013] After the fan system component stops rotating, the operating parameters of the circulating fluidized bed boiler are monitored.

[0014] In the above scheme, the operating parameters include the drum water level, and the operating steam-water system components include:

[0015] When the drum water level meets preset conditions, the steam-water system components are operated.

[0016] In the above solution, the operating parameters include bed temperature, and the method further includes:

[0017] When the bed temperature drops to a first set temperature, the primary fan is turned on, and when the bed temperature rises to a second set temperature, the primary fan is turned off.

[0018] In the above scheme, the method further comprises:

[0019] During the fire raising stage, the fan system components are turned on in sequence and the steam-water system components are operated in sequence.

[0020] In the above scheme, the order of starting the fan system components is: start the induced draft fan, start the primary fan, start the primary feeding system, start the secondary feeding system, start the return fan, and start the secondary fan;

[0021] The operating sequence of the steam-water system components is: open the main steam valve, close the economizer recirculation valve, start the feed water pump, start the deaerator water pump, and open the deaerator heating steam regulating valve.

[0022] In the above scheme, the ignition fuel is a biomass fuel with a moisture content of less than 10% and a fuel particle size of less than 30 mm.

[0023] The above-mentioned pressure-fire operation method of the circulating fluidized bed boiler can increase the heat capacity in the bed by increasing the thickness of the bed material and gradually increasing the bed temperature during the pressure-fire preparation stage, provide additional heat energy for the fuel in the bed, help maintain the temperature required for combustion and maintain the furnace temperature during the pressure-fire process, thereby extending the thermal stability of the furnace wall and the bed material. During the pressure-fire stage, the fan system components in the circulating fluidized bed boiler are shut down in sequence and the steam-water system components are operated in sequence, so that the boiler is in a pressure-fire state, and it is ensured that the fluid conveying channel in the circulating fluidized bed boiler is completely sealed, so as to reduce the heat loss during the pressure-fire process and maintain the heat in the furnace.

[0024] Based on this, the circulating fluidized bed boiler utilizes the heat capacity of the bed material, the chemical heat of the unburned fuel and the good sealing and thermal insulation properties of the boiler to help maintain the thermal environment in the furnace, slow down the rate of decrease in bed temperature, extend the boiler ignition time, achieve long-term ignition standby status of the boiler, and increase the success rate of ignition operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of a circulating fluidized bed boiler;

[0026] Figure 2 The figure is a flow chart of a method for operating a circulating fluidized bed boiler under reduced pressure in one embodiment.

[0027] Figure numerals: belt conveyor 1; front silo 2; primary feeder 3; secondary feeder 4; secondary air box 5; main combustion chamber 6; auxiliary combustion chamber 7; burnout chamber 8; primary returner 9; secondary returner 10; primary fan 11; secondary fan 12; return fan 13; induced draft fan 14; environmental protection equipment 15; economizer 16; air preheater 17; feed water pump 18; deaerator water pump 19; deaerator 20; main steam valve 21; separator 22; deaerator heating steam valve 23; economizer recirculation valve 24, sealing fan 25. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] The implementation details of the technical solution of the embodiment of the present application are described in detail below.

[0030] like Figure 1 As shown, Figure 1 The schematic diagram of the structure of the circulating fluidized bed boiler is shown. The circulating fluidized bed boiler is a three-bed multi-stage multi-flow multi-fuel circulating fluidized bed boiler, which is mainly composed of a main combustion chamber 6, an auxiliary combustion chamber 7, a burnout chamber 8, a primary return device 9, a secondary return device 10, an economizer 16, an air preheater 17, and a separator 22.

[0031] There are three different beds inside the circulating fluidized bed boiler, which can be used for different fuels or different combustion stages to improve combustion efficiency and thermal energy utilization. Multi-stage means that in the design of the circulating fluidized bed boiler, the combustion process is divided into multiple stages or levels, and each level can be optimized for different fuel characteristics or combustion conditions, thereby improving overall combustion efficiency and reducing emissions. Multi-flow refers to the fact that there may be multiple airflow or fuel flow paths inside the circulating fluidized bed boiler. This design can achieve more flexible operation, allowing different fuels to be burned in different flows, optimizing heat exchange and gas flow. Multi-fuel means that the circulating fluidized bed boiler is able to use multiple types of fuels for combustion, such as biomass, natural gas, etc.

[0032] The operation process of the circulating fluidized bed boiler can be divided into the ignition preparation stage, ignition stage and ignition raising stage. The ignition preparation stage refers to the preparation work before the circulating fluidized bed boiler is about to enter the ignition state; the ignition stage refers to the process of the circulating fluidized bed boiler maintaining the combustion state after the fuel supply is stopped; the ignition raising stage refers to the process of igniting the fuel and resuming normal operation when the circulating fluidized bed boiler is ready to restart.

[0033] The following describes in detail the application of Figure 1 The shown method for operating a circulating fluidized bed boiler under pressure enables the circulating fluidized bed boiler to achieve long-term pressure firing and improve the success rate of firing through operations in the pressure firing preparation stage, the pressure firing stage and the firing raising stage.

[0034] In one embodiment, Figure 2 As shown, Figure 2 A method for operating a circulating fluidized bed boiler under reduced pressure is shown, and the method may include the following steps:

[0035] Step S101, in the ignition preparation stage, the bed material thickness is increased from a first thickness to a second thickness, and the bed temperature is gradually increased from a first temperature to a second temperature according to the coking characteristics of the ignition fuel.

[0036] Here, in order to extend the ignition time of the circulating fluidized bed boiler, several preparatory tasks need to be carried out in the ignition preparation stage.

[0037] In this embodiment, the preparation work includes the preparation of the bed material thickness before the ignition. In the boiler, the bed material refers to the material used to support and fix the fuel, which can provide a stable combustion platform to ensure that the fuel can burn evenly and transfer heat effectively. In practical applications, the heat capacity of the bed material directly affects the thermal stability of the circulating fluidized bed boiler. A larger heat capacity can store more heat energy, help maintain the temperature in the circulating fluidized bed boiler, reduce temperature fluctuations, and thus extend the ignition time.

[0038] Based on this, in the stage of ignition preparation, the bed material thickness needs to be increased from the first thickness to the second thickness, wherein the second thickness is 100-300 mm higher than the first thickness. It should be noted that the first thickness here refers to the bed material thickness during normal operation of the circulating fluidized bed boiler, wherein normal operation may refer to an operation scenario where the circulating fluidized bed boiler does not need ignition. In actual applications, the bed material thickness can be increased about 30 minutes before ignition.

[0039] In the stage of ignition preparation, the thermal capacity of the boiler can be increased by increasing the thickness of the bed material, so that it can store more heat energy, which helps to keep the temperature in the furnace stable during the ignition process and reduce temperature fluctuations. When the thickness of the bed material increases, the heat loss rate of the bed material will slow down, thereby delaying the drop in bed temperature, allowing the circulating fluidized bed boiler to achieve long-term ignition. At the same time, increasing the thickness of the bed material can reduce the temperature difference between the furnace wall and the bed material, reduce thermal stress, and thus extend the service life of the furnace wall. Thicker bed material can provide a better thermal environment, so that the fuel in the bed maintains a certain activity under the ignition state, which helps to make it easier to ignite the fuel in the subsequent ignition process.

[0040] In this embodiment, the preparation work also includes the preparation of the bed temperature before the pressure firing. In the boiler, the adapted bed temperature can ensure that the fuel is fully burned during the pressure firing process and reduce the temperature fluctuation in the furnace, which is very important for maintaining the pressure firing for a long time.

[0041] Based on this, during the pressure ignition preparation stage, the bed temperature needs to be increased. The circulating fluidized bed boiler gradually increases the bed temperature from the first temperature to the second temperature according to the coking characteristics of the pressure ignition fuel. In practical applications, the second temperature is usually 50-200°C higher than the first temperature. It should be noted that the first temperature refers to the temperature of the circulating fluidized bed boiler when pressure ignition preparation is not performed, such as the bed temperature of the circulating fluidized bed boiler in normal operation, or the bed temperature of the circulating fluidized bed boiler in standby mode. The first temperature is at a relatively low level and does not reach the ideal temperature required for pressure ignition. The bed temperature is gradually increased from the first temperature to the second temperature, that is, to reach a temperature range suitable for pressure ignition, to ensure that the fuel can be fully burned and promote the smooth progress of the pressure ignition process.

[0042] Among them, the increase of bed temperature can be carried out about 30 minutes before the ignition. During the process of increasing the bed temperature, the temperature increase amplitude is superimposed on the first temperature, so that the bed temperature reaches the second temperature. Among them, the temperature increase amplitude is determined by the coking characteristics of the ignition fuel. It can be understood that different fuels have different coking tendencies. For ignition fuels with higher coking tendencies, a smaller temperature increase amplitude (such as 50-100°C) is used to avoid excessive coke production during the heating process; for ignition fuels with lower coking tendencies, a larger temperature increase amplitude (such as 150-200°C) is used to quickly reach the temperature required for ignition. After determining the temperature increase amplitude, the bed temperature is gradually increased according to the temperature increase amplitude, so that the bed temperature is increased from the first temperature to the second temperature. It should be noted that the second temperature should be lower than the coking temperature of the ignition fuel (that is, the temperature at which the fuel begins to coke) to prevent the occurrence of coking.

[0043] In practical applications, the bed temperature can be gradually increased by reducing the primary and secondary return rates. By reducing the primary and secondary return rates, the cooling effect of the bed can be reduced, allowing the bed temperature to rise faster, which helps to quickly reach the required temperature range before ignition.

[0044] In the stage of ignition preparation, gradually increasing the bed temperature helps the fuel burn fully, thereby increasing the heat output of the boiler, enhancing the thermal stability of the boiler, extending the ignition time, and slowing down the bed temperature drop. Appropriate bed temperature can reduce the thermal stress of the furnace wall, thereby extending the service life of the furnace wall. At the same time, increasing the bed temperature can improve the combustion conditions, making the fuel easier to volatilize and burn during ignition. In the absence of an auxiliary burner, it can also ensure that the fuel can be ignited quickly, thereby increasing the success rate of ignition.

[0045] In the above embodiment, in the pressure-fire preparation stage, the bed material thickness is increased and the bed temperature is raised, and the heat capacity of the bed material, the chemical heat of the unburned fuel and the insulation effect of the boiler are utilized to achieve long-term pressure-fire standby of the boiler.

[0046] In one embodiment, the compressed fire fuel is a biomass fuel with a moisture content of less than 10%, a fixed carbon content of more than 15%, and a low calorific value of more than 2300 kcal / kg.

[0047] The preparatory work carried out in the compressed fire preparation stage also includes the preparation of compressed fire fuel. Biomass fuel with lower moisture content (less than 10%), higher fixed carbon content (greater than 15%), and higher low calorific value (greater than 2300kcal / kg) is used as compressed fire fuel. Among them, compressed fire fuel with lower moisture content helps to improve combustion efficiency and reduce energy loss; compressed fire fuel with appropriate ash content can help maintain combustion stability; compressed fire fuel with higher calorific value can provide more energy and reduce fuel consumption.

[0048] In this embodiment, by preparing compressed fire fuel, the combustion efficiency of the fuel and the retention of heat in the boiler are improved, so that the compressed fire fuel provides more lasting heat during the combustion process, and the boiler can better maintain the internal temperature during the compressed fire stage, thereby achieving long-term compressed fire.

[0049] In one embodiment, during the ignition preparation stage, the amount of ignition fuel is increased.

[0050] The preparations carried out during the ignition preparation phase also include the control of the oxygen content at the furnace outlet. It is understood that oxygen is one of the key factors in combustion, and the ignition preparation phase needs to ensure that the combustion process gradually weakens to prepare for the ignition operation. The reduction in oxygen content directly affects the intensity of the combustion process. By reducing the oxygen content, the combustion reaction can be weakened, the flame is gradually extinguished, and the conditions for the ignition operation are created.

[0051] Here, by increasing the amount of compressed fire fuel without changing the air supply, the mixing ratio of compressed fire fuel and air is increased, thereby gradually reducing the residual oxygen in the furnace and reducing the oxygen content at the furnace outlet, and finally reducing the oxygen content at the furnace outlet to below 1%. Among them, the increase in the amount of fuel should be controlled within an appropriate range so that the combustion process gradually weakens, rather than suddenly increasing the fuel, resulting in an overly violent or incomplete combustion reaction. In this way, the oxygen content and temperature in the furnace can be better controlled, and a smooth transition to the compressed fire state can be achieved.

[0052] In practical applications, the oxygen content at the furnace outlet can be monitored in real time, the current oxygen level can be recorded, and the supply of compressed ignition fuel can be gradually increased based on the monitoring results. While increasing the supply of compressed ignition fuel, the oxygen content at the furnace outlet is continuously monitored and its changing trend is observed to ensure that the oxygen content at the furnace outlet is reduced to below 1%.

[0053] In this embodiment, by increasing the amount of compressed ignition fuel and reducing the oxygen content at the furnace outlet, the compressed ignition fuel can burn more persistently during the compressed ignition process, thereby achieving a long-term compressed ignition operation.

[0054] Step S102, during the fire suppression stage, shut down the fan system components in the circulating fluidized bed boiler and operate the steam-water system components, and ensure that the sealing components in the circulating fluidized bed boiler are completely sealed after the fan system components stop rotating.

[0055] After the circulating fluidized bed boiler enters the fire suppression stage, the boiler does not need to burn fuel, so the fan system and the steam-water system do not need to continue to operate. It is necessary to shut down the fan system components in the circulating fluidized bed boiler and operate the steam-water system components in sequence. After shutting down the fan system components and operating the steam-water system components in sequence, unnecessary air can be prevented from flowing into the boiler, avoiding heat loss, helping to maintain the heat inside the boiler and achieving a heat preservation effect.

[0056] Among them, the fan system is mainly responsible for providing the air and airflow required by the boiler to support the combustion process, including different components such as different fans and dampers; the steam-water system is mainly responsible for the boiler's feed water, steam generation and discharge, including different components such as different water pumps and air valves.

[0057] After the fan system components have completely stopped rotating, it is necessary to check the closing state of the fluid delivery channel in the circulating fluidized bed boiler to ensure that the sealing components are completely sealed. The sealing components include the dampers, openings (including manholes, inspection holes, observation holes, etc.), fuel channels, and slag and ash discharge ports in the circulating fluidized bed boiler.

[0058] A properly closed damper can prevent external cold air from entering the boiler, thereby reducing heat loss and maintaining the temperature inside the boiler; a properly closed opening can effectively isolate the external environment and prevent heat loss through these openings; a properly closed fuel channel can prevent fuel from accidentally entering the boiler, avoid unnecessary combustion and heat loss, and help maintain the temperature and pressure of the boiler; a properly closed slag and ash discharge port can prevent the leakage of ash and slag, keeping the inside of the boiler clean and the heat concentrated.

[0059] In the above embodiment, by ensuring that the sealing assembly remains airtight during the ignition process and utilizing the good sealing performance of the boiler, it is possible to prevent heat loss in the boiler and provide a heat preservation effect, thereby facilitating the ignition for a long time.

[0060] In one embodiment, the fan system components are shut down in sequence, wherein the shutdown sequence of the fan system components is:

[0061] (1) Stopping feeding, including shutting down the primary feeder 3 and the secondary feeder 4, can stop feeding fuel into the boiler to prevent the boiler from continuing to burn and ensure that the fuel process gradually weakens.

[0062] (2) Shut down the feed seal fan to prevent fuel leakage after the supply is stopped, ensure the sealing of the system, and prevent air from flowing into the combustion chamber, thereby reducing the occurrence of combustion reactions.

[0063] (3) Stop the secondary fan and close the secondary air damper. The secondary fan is used to provide the air required for combustion. Shutting down the secondary fan can cut off the air supply and reduce the intensity of combustion. Closing the secondary air damper further ensures that air does not enter the combustion chamber.

[0064] (4) Shut down the primary fan. The primary fan usually provides primary combustion air. Shutting down the primary fan can reduce air intake.

[0065] (5) Shut down the induced draft fan. The induced draft fan is responsible for extracting the exhaust gas out of the boiler. Shutting down the induced draft fan can prevent too much cold air from entering and avoid cooling the boiler too quickly.

[0066] (6) Turn off the return fan to stop returning unburned fuel or ash to the boiler to avoid affecting the boiler.

[0067] Similarly, the soda system components are operated in sequence, wherein the operation sequence of the soda system components is:

[0068] (1) Shut down the feed pump. The feed pump is responsible for delivering water to the boiler. When shutting down, first stop the feed pump to prevent the water level in the boiler from continuing to rise, thus avoiding excessive water level or other safety hazards caused by the boiler no longer needing steam generation.

[0069] (2) Open the economizer recirculation valve. The economizer is a device that uses the heat of the flue gas at the tail of the boiler to preheat the feed water. When shutting down, opening the economizer recirculation can prevent the water temperature in the economizer from being too low, and prevent cold water from flowing into the economizer without sufficient heat source, causing thermal stress and causing damage to the economizer. At the same time, it can prevent the water in the equipment from being overheated or overcooled.

[0070] (3) Close the main steam valve. The main steam valve controls the output of steam. Closing the main steam valve can cut off the steam transmission to the outside, preventing the steam from continuing to be output after the shutdown, resulting in unstable pressure in the system or damage to other equipment.

[0071] This operating sequence can stop the operation of the equipment in an orderly manner, prevent uncontrolled combustion in the boiler, help maintain the pressure and temperature balance inside the boiler, avoid system instability caused by sudden shutdown, and reduce thermal stress caused by temperature changes inside the boiler, reducing the risk of equipment damage.

[0072] In one embodiment, after the fan system component stops rotating, the operating parameters of the circulating fluidized bed boiler are monitored. In practical applications, the operating parameters of the circulating fluidized bed boiler are monitored to ensure that the boiler is safely shut down and that the states of various systems of the boiler are within a controllable range during the ignition process.

[0073] Among them, the monitored operating parameters may include:

[0074] (1) Bed temperature (i.e., the temperature of the combustion bed). The bed temperature reflects the combustion state of the fuel in the boiler. Even if the feed and fan are stopped, the residual heat of the combustion bed will continue for a period of time. Monitoring the bed temperature helps to understand the changes in bed temperature during the ignition process.

[0075] (2) Temperature of the return device. The temperature of the return device reflects the state of the return system and ensures that the temperature of the return device remains within a reasonable range during the ignition process.

[0076] (3) Furnace flue gas temperature. The furnace flue gas temperature reflects the combustion conditions and residual heat in the combustion chamber. By monitoring the furnace flue gas temperature, the combustion conditions in the furnace during the ignition process can be determined.

[0077] (4) Boiler outlet flue gas temperature. The boiler outlet flue gas temperature shows the flue gas temperature after passing through the boiler. It is an important indicator for judging the internal heat and combustion status of the boiler. It can reflect the heat dissipation in the boiler during the fire suppression process.

[0078] (5) Drum pressure. Drum pressure reflects the status of the boiler steam system. During shutdown, the drum pressure should gradually decrease.

[0079] (6) Drum water level. The drum water level reflects the water level in the boiler and ensures that the boiler will not be damaged due to abnormal water level during the firing process.

[0080] (7) Economizer outlet water temperature. The economizer outlet water temperature reflects the heating condition of boiler feed water. Monitoring the water temperature can help understand the cooling condition of the boiler.

[0081] (8) Boiler oxygen level. The boiler oxygen level reflects the residual oxygen content in the furnace. Monitoring the oxygen level can determine whether combustion has completely stopped.

[0082] By monitoring the above operating parameters, it is possible to determine whether the operating parameters of the boiler during the fire suppression process are within the safe range, ensure that combustion is completely stopped, and prevent abnormal temperature and pressure from causing equipment damage or safety accidents. In addition, through the monitored operating parameters, the boiler system can be appropriately adjusted so that the circulating fluidized bed boiler can achieve long-term fire suppression.

[0083] In one embodiment, the steam-water system components are operated when the steam drum water level meets a preset condition.

[0084] The drum water level meets the preset condition when the water level in the boiler drum reaches the shutdown standard. The boiler drum water level should be within the safe range of normal operation and maintained in the safe water level range specified in the design.

[0085] In actual applications, the steam-water system can deliver water to the boiler drum to maintain the drum water level. When the steam-water system components are shut down, the boiler will no longer be replenished with water through the steam-water system, and the drum water level will no longer rise. Therefore, it is necessary to ensure that the water level has reached the safe water level range before shutting down. If the water level fails to reach the safe water level range before shutting down, shutting down the steam-water system components will cause the drum water level to drop too much, causing the boiler to lack water, and causing serious safety accidents, such as overheating or even damage to the boiler tube. If the water level is too high, the steam may carry moisture, affecting the steam quality and possibly damaging downstream equipment. In addition, shutting down the steam-water system means that the boiler will no longer output steam to the outside, and the pressure and temperature inside the boiler will gradually decrease. In this process, the drum water level may change due to the influence of steam condensation. If the water level is not within the appropriate range, it may cause the water level to rise or fall suddenly, increasing the operating risk of the equipment. Therefore, the water level must reach the safe water level range.

[0086] Determine whether the monitored drum water level is within the safe water level range. If the drum water level is within the safe water level range, operate the steam-water system components to ensure the safety and stability of the boiler during shutdown and prevent boiler equipment from being damaged due to insufficient water level or temperature changes.

[0087] In one embodiment, when the bed temperature drops to a first set temperature, the primary fan is turned on, and when the bed temperature rises to a second set temperature, the primary fan is turned off.

[0088] During the fire suppression process of the boiler, the change of bed temperature directly affects the stable operation of the boiler. When the bed temperature is too low, the boiler may face the risk of incomplete combustion or fire extinguishing. Based on this, it is necessary to continuously monitor the change of bed temperature during the fire suppression process. When the bed temperature gradually decreases to the first set temperature (for example, 550°C), prepare to perform the fire raising operation during the fire suppression process, specifically turning on the primary fan. Due to the addition of primary air, the air supply is increased and the bed temperature will gradually rise. After turning on the primary fan, the air volume of the primary air should be strictly controlled to avoid excessive air volume causing unstable flames in the furnace or blowing away fuel, affecting the combustion effect. When the bed temperature gradually rises to the second set temperature (for example, 650°C), it means that the combustion conditions in the furnace have improved and the bed temperature has returned to a safe range. At this time, the primary fan is turned off.

[0089] In the above embodiment, the bed temperature change is continuously monitored during the ignition process, so that the bed temperature can be kept at a suitable temperature during the ignition process, thereby achieving long-term ignition. In addition, the suitable bed temperature can help maintain a good combustion environment, ensure that the fuel is quickly ignited and stably burned after entering the furnace, and can achieve the ignition operation without the help of additional auxiliary burners, thereby improving the success rate of the ignition operation.

[0090] In one embodiment, during the fire raising stage, the blower system components are turned on sequentially and the steam-water system is operated sequentially.

[0091] During the fire raising stage, the main purpose of fire raising is to restore the combustion of fuel, so the fan system components need to be turned on to increase air inflow, help the fuel ignite and improve combustion efficiency. In addition, the steam-water system components need to be operated in sequence to ensure the overall stable operation of the boiler during the fire raising stage.

[0092] The ignition operation during the ignition stage is to ensure that the fuel can be ignited smoothly, the bed temperature can be raised to the required level, and the boiler maintains stable operation throughout the process.

[0093] It should be noted that the fire raising operation in the fire suppression stage is different from the fire raising operation in the fire raising stage. The fire raising operation in the fire suppression stage is to keep the bed temperature within a suitable temperature range, while the fire raising operation in the fire raising stage is to restore the combustion of the fuel.

[0094] In one embodiment, the fan system components are turned on in sequence, wherein the order of turning on the fan system components is:

[0095] (1) Turn on the induced draft fan 14. The induced draft fan 14 is used to control the negative pressure and flue gas flow in the furnace. Turning on the induced draft fan 14 can help guide the flue gas to flow out and provide appropriate negative pressure conditions for the furnace.

[0096] (2) Turn on the primary fan 11. The primary fan 11 provides air inflow to help the fuel ignite and increase the bed temperature, gradually increasing the air volume to ensure that the fuel can be ignited smoothly.

[0097] (3) Start the primary feeding system 3. Add fuel to the furnace through the primary feeding system 3 to promote the combustion of the fuel. Ensure that the fuel supply matches the air flow to optimize the combustion effect.

[0098] (4) Start the secondary feeding system 4. The secondary feeding system 4 further adds fuel to increase the fuel supply to support the continuous combustion process.

[0099] (5) Turn on the return fan 13. The return fan 13 is used to recover and circulate fuel to ensure uniform distribution and effective use of the fuel. Turning on the return fan 13 helps maintain a stable supply and combustion of the fuel.

[0100] (6) Turn on the secondary fan 12. The secondary fan 12 provides additional air support to promote complete combustion of the fuel.

[0101] Similarly, the soda system components are operated in sequence, wherein the operation sequence of the soda system components is:

[0102] (1) Open the main steam valve 21. The main steam valve 21 controls the steam outflow from the boiler. Opening the main steam valve 21 can release steam and maintain the pressure balance of the boiler.

[0103] (2) Close the economizer recirculation valve 24. The economizer recirculation valve 24 is used to control the water flow loop of the economizer. Closing the valve can stop the water recirculation, thereby adjusting the operating state of the boiler and preparing for the fire raising operation.

[0104] (3) Turn on the feed water pump 18. The feed water pump 18 is used to deliver water to the boiler to maintain the water level of the boiler. Turning on the feed water pump 18 can ensure that the boiler has enough water to carry out the fire-raising process.

[0105] (4) Turn on the deaeration water pump 19. The deaeration water pump 19 is used to provide deaeration water to the boiler, remove oxygen from the water, and prevent internal corrosion of the boiler. Turning on the deaeration water pump 19 helps to protect the stability of the boiler system and extend its service life.

[0106] (5) Open the deoxygenation heating steam regulating valve 23. The deoxygenation heating steam regulating valve 23 is used to adjust the steam heating in the deoxygenation to ensure the deoxygenation effect of the deoxygenated water. Opening this regulating valve can improve the deoxygenation effect and maintain the good water quality.

[0107] In the above embodiment, the operation sequence of the fan system is mainly focused on providing and regulating air, fuel and air volume, while the operation of the steam-water system focuses on regulating the water level, steam outflow and water quality treatment of the boiler. The orderly execution of starting the fan system components and operating the steam-water system components helps to ensure the effective ignition of the fuel and the stable operation of the boiler.

[0108] In one embodiment, the ignition fuel is a biomass fuel with a moisture content of less than 10% and a fuel particle size of less than 30 mm.

[0109] Here, the ignition stage also includes the preparation of ignition fuel, and biomass fuel with a moisture content of less than 10% and a fuel particle size of less than 30 mm is selected as the ignition fuel. Among them, the moisture content of less than 10% means that the fuel has a higher calorific value and better combustion efficiency, and the fuel particle size of less than 30 mm is conducive to more uniform combustion, improving fuel utilization and combustion stability, which is particularly important for the ignition operation, and can establish a stable combustion state more quickly, which is conducive to improving the success rate of the ignition operation.

[0110] In the above embodiment, the circulating fluidized bed boiler increases the bed material thickness and gradually increases the bed temperature during the ignition preparation stage, shuts down the fan system components and operates the steam-water system components during the ignition stage, and ensures that the sealing components are completely sealed after the fan system components stop rotating, thereby utilizing the thermal capacity of the bed material, the chemical heat of the unburned fuel and the good sealing and thermal insulation properties of the boiler to effectively extend the ignition time, slow down the rate of bed temperature drop, and achieve long-term ignition standby status of the boiler, and also extend the service life of the furnace wall, increase the probability of successful ignition, and save fuel costs.

[0111] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0112] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0113] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for operating a circulating fluidized bed boiler under reduced pressure, characterized in that: Applied to a circulating fluidized bed boiler, the method comprises: In the ignition preparation stage, the bed material thickness is increased from a first thickness to a second thickness, and the bed temperature is gradually increased from a first temperature to a second temperature according to the coking characteristics of the ignition fuel; wherein the second thickness is 100-300 mm higher than the first thickness; During the fire suppression stage, the fan system components in the circulating fluidized bed boiler are shut down and the steam-water system components are operated, and after the fan system components stop rotating, it is ensured that the sealing components in the circulating fluidized bed boiler are completely sealed.

2. The method for compressed fire operation according to claim 1, characterized in that: The compressed fire fuel is a biomass fuel with a moisture content lower than 10%, a fixed carbon content higher than 15%, and a low calorific value greater than 2300 kcal / kg.

3. The method for compressed fire operation according to claim 1, characterized in that: The method further comprises: In the ignition preparation stage, the amount of ignition fuel is increased.

4. The method for compressed fire operation according to claim 1, characterized in that: The shutdown sequence of the fan system components is: stop feeding, shut down the feeding sealing fan, stop the secondary fan and close the secondary air door, shut down the primary fan, shut down the induced draft fan, and shut down the return fan; The operating sequence of the steam-water system components is: shut down the feedwater pump, open the economizer recirculation valve, and close the main steam valve.

5. The method for compressed fire operation according to claim 1, characterized in that: The method further comprises: After the fan system component stops rotating, the operating parameters of the circulating fluidized bed boiler are monitored.

6. The method for compressed fire operation according to claim 5, characterized in that: The operating parameters include the drum water level, and the operating steam-water system components include: When the drum water level meets preset conditions, the steam-water system components are operated.

7. The method for compressed fire operation according to claim 4, characterized in that: The operating parameters include bed temperature, and the method further includes: When the bed temperature drops to a first set temperature, the primary fan is turned on, and when the bed temperature rises to a second set temperature, the primary fan is turned off.

8. The fire suppression operation method according to claim 1 or 7, characterized in that: The method further comprises: During the fire raising stage, the fan system components are turned on in sequence and the steam-water system components are operated in sequence.

9. The method for compressed fire operation according to claim 8, characterized in that: The order of starting the fan system components is: start the induced draft fan, start the primary fan, start the primary feeding system, start the secondary feeding system, start the return fan, and start the secondary fan; The operating sequence of the steam-water system components is: open the main steam valve, close the economizer recirculation valve, start the feed water pump, start the deaerator water pump, and open the deaerator heating steam regulating valve.

10. The method for compressed fire operation according to claim 8, characterized in that: The ignition fuel is a biomass fuel with a moisture content of less than 10% and a fuel particle size of less than 30 mm.

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