A method of igniting a circulating fluidized bed boiler

Abstract

This invention discloses an ignition method suitable for circulating fluidized bed boilers, belonging to the field of circulating fluidized bed boiler heating technology, including the following steps: preparing fuel, starting the return air fan, injecting spare bed material, with a static bed material layer thickness of not less than 500mm; conducting cold-state characteristic tests; determining the minimum fluidizing air volume of the bed material; adjusting the ignition damper to 100% full opening and the fluidizing damper to 10% opening, and igniting according to the operating procedures; adjusting the oil pressure according to the bed temperature rise rate after ignition; when the average temperature of the furnace bed reaches 450℃, opening the exhaust valve of the return air chamber to 60%, and reducing the air chamber pressure from 11Kpa to 6Kpa; when the average temperature of the furnace bed material reaches 550℃, pulse coal feeding is performed; gradually adjusting the primary air volume and secondary air volume; slowly closing the exhaust valve of the return air chamber, increasing the pressure, gradually increasing the circulating ash volume, and adjusting the coal feed rate, primary air volume, and secondary air volume until the exhaust valve is completely closed.

Description

Technical Field

[0001] This invention relates to the field of circulating fluidized bed boiler heating technology, and more specifically to an ignition method suitable for circulating fluidized bed boilers. Background Technology

[0002] Circulating fluidized bed (CFB) boilers use fluidizing air to blow coal particles, biomass, and other fuels and bed materials from the bottom of the furnace, fluidizing the particles and facilitating combustion. The flue gas carries some fine particles out of the furnace and into a gas-solid separator, which captures particles from fly ash and returns them to the furnace via a return feeder, forming a circulation of solid particles. The furnace contains a large amount of fluidized, inert solid particle bed material, mainly composed of ash residue from coal combustion; these particles do not participate in the combustion reaction. Due to the strong heat storage capacity of the high-temperature bed material, the residence time of fuel in the furnace is increased, and combustion efficiency is high, thus CFB boilers have a wide range of fuel applicability. CFB boilers can achieve stable combustion at relatively low combustion temperatures (800-900℃), resulting in lower nitrogen oxide formation compared to pulverized coal boilers. By adding limestone into the furnace, sulfur dioxide can be removed during combustion, significantly reducing desulfurization costs. Based on the above advantages, circulating fluidized bed boilers are the best choice for large-scale clean utilization of fuels such as high-sulfur and high-ash coal, gangue, middlings coal, coal slime, and biomass.

[0003] The existing ignition steps for a circulating fluidized bed boiler are as follows: (1) Start the induced draft fan, the forced draft fan, and the return material fan; (2) Inject the bed material for ignition; (3) Conduct a cold-state characteristic test; (4) Determine the minimum bed material fluidization air volume; (5) Adjust the ignition damper to 100% full opening and the fluidization damper to 10% opening, and ignite according to the operating specifications; (6) When the average bed temperature of the boiler furnace reaches 650℃, perform pulse coal feeding; (7) Adjust the air and coal volume according to the temperature rise and oxygen changes, and raise the furnace temperature to the normal operating temperature of 850℃ in 6-8 hours.

[0004] Because the return system of a circulating fluidized bed boiler is an external circulation device, it can automatically balance the pressure between the circulating ash and the furnace during normal operation, requiring no adjustment and having no regulation method. Therefore, there is also no regulation method during ignition. This leads to a situation where, during ignition and temperature rise, the circulating cold ash in the return system continuously returns into the furnace to absorb heat, causing the furnace bed temperature to rise slowly or even fluctuate repeatedly after reaching 450℃, resulting in the risk of coking and potentially causing an accidental shutdown. Summary of the Invention

[0005] This invention aims to solve problems such as slow furnace bed temperature rise and repeated furnace bed temperature fluctuations leading to coking risks. It provides an ignition method suitable for circulating fluidized bed boilers. The circulating fluidized bed boiler return feeder, as an external circulation device, can achieve automatic balance of material resistance and circulation during normal operation without adjusting the circulating ash amount to control the rise and fall of bed temperature. Therefore, this invention uses the opening size of the exhaust valve in the return feeder's air chamber to adjust the circulating ash amount during ignition, thereby increasing the furnace temperature rise rate.

[0006] The objective of this invention is achieved through the following technical solution: An ignition method suitable for circulating fluidized bed boilers includes the following steps: Step 1: Prepare fuel, start the return blower, and pump in the spare bed material. The thickness of the stationary bed material layer should be controlled at 450-550mm. Step 2: Conduct cold-state characteristic tests; Step 3: Determine the minimum fluidizing air volume for the bed material; Step 4: Adjust the ignition damper to 100% full opening and the fluidization damper to 10% opening, then ignite according to the ignition procedure; Step 5: After ignition, adjust the oil pressure according to the rate of bed temperature rise; when the average temperature of the furnace bed reaches 450℃, open the exhaust valve of the return feeder air chamber to 60%, and reduce the air chamber pressure from 11Kpa to 6Kpa. Step 6: When the average temperature of the furnace bed material reaches 550℃, pulse coal feeding is carried out; Step 7: When the average temperature of the furnace bed reaches 700℃ using pulse coal feeding, adjust the coal feeder speed to 120 r / m for continuous coal feeding. When the average temperature of the furnace bed rises to 750℃, increase the opening of the primary air fan inlet regulating damper by 3000 m³ / min based on the minimum fluidizing air volume. 3 When the average temperature of the furnace bed reaches 850℃, the secondary air fan is started to maintain the oxygen content of the flue gas at no less than 8%; Step 8: Slowly close the exhaust valve of the return feeder's air chamber, increase the pressure, and gradually increase the circulating ash volume. When the temperature drops to 750℃, reduce the volume by 2000m³. 3 To increase the primary air volume by 100 m³ / h, increase the coal feeder speed to 150 r / min. When the average temperature change rate of the furnace bed is +5℃ / min and continues to increase, increase the opening of the primary air fan inlet regulating damper by 3000 m³ / h. 3 The primary air volume is increased by 1 / h, and the opening of the secondary air fan inlet regulating damper is increased to maintain the oxygen content of the flue gas at no less than 6% until the exhaust valve is completely closed.

[0007] Preferably, in step one, the particle size of the fuel is less than 10 mm and the carbon content of the fuel is less than 2%.

[0008] Preferably, in step two, the cold-state characteristic test includes the following tests: (1) Inspection of electric doors, dampers and regulating baffles; (2) Measure the air volume and pressure head of the induced draft fan, primary air fan, return air fan and secondary air fan, and check whether the induced draft fan, primary air fan, return air fan and secondary air fan meet the nameplate parameters and can meet the hot operation requirements; (3) Measure the boiler's tightness; (4) Measure the empty bed resistance of the boiler and check the uniformity of air distribution by the air distribution plate; (5) Measure the critical fluidization air volume; (6) Verify the output of the coal feeder and assess the performance of the coal feeder system; (7) Performance test of material circulation system; (8) Start the induced draft fan and primary air fan to conduct an air plate resistance test.

[0009] Preferably, in step three, after the cold-state characteristic test is completed, the return fan, primary air fan, and induced draft fan are shut down, and the primary air fan inlet regulating damper, fluidizing air regulating damper, and induced draft fan inlet regulating damper are quickly closed. The flatness of the stationary material layer in the furnace is observed. After the overall flatness is achieved without material pile-up, the induced draft fan, primary air fan, and return fan are restarted, maintaining a negative pressure of -0.08 kPa. The opening of the primary air fan inlet regulating damper is gradually increased until the entire bed material layer is boiling without any "dead zones." The primary air fan current, primary air volume, primary air fan inlet regulating damper opening, and bed pressure value are recorded under this state. The primary air volume at this time is the minimum fluidizing air volume under this material layer.

[0010] Preferably, in step four, ignition is performed according to the ignition procedure: start purging, stop purging, advance the electronic ignition gun, start the high-energy electronic burner to ignite, open the oil valve, observe the ignition through the observation mirror, and then withdraw the electronic ignition gun.

[0011] Preferably, in step five, when the bed temperature change rate is less than 1℃ / min, the opening of the return oil valve is adjusted to decrease, from the initial oil pressure of 0.8Mpa to 1.0Mpa, and then adjusted incrementally in increments of 0.2Mpa / time.

[0012] Preferably, in step six, the pulse coal feeding is as follows: start the coal feeder, adjust the speed to 100 r / m, run for 3 minutes and then stop. When the oxygen content in the flue gas decreases and the original oxygen content drops to 2% and then shows an upward trend, start the coal feeder again.

[0013] Preferably, in step eight, the closure status of the exhaust valve in the return material's air chamber is as follows: (1) Adjust the opening of the exhaust valve of the return material air chamber to 50%, increase the air chamber pressure to 7 kPa, and maintain it for 10 minutes; (2) Adjust the opening of the exhaust valve of the return material air chamber to 40%, increase the air chamber pressure to 8 kPa, and maintain it for 10 minutes; (3) Adjust the opening of the exhaust valve of the return material air chamber to 30%, increase the air chamber pressure to 9 kPa, and maintain it for 10 minutes; (4) Adjust the opening of the exhaust valve of the return material air chamber to 20%, increase the air chamber pressure to 10 kPa, maintain for 30 minutes, and gradually increase the temperature of the circulating ash in the return material to 600℃. (5) Adjust the opening of the exhaust valve of the return material air chamber to 10%, increase the air chamber pressure to 11 kPa, maintain for 30 minutes, and the temperature of the circulating ash in the return material gradually rises to 750℃. (6) When the exhaust valve of the return material chamber is closed to 0%, the average temperature of the furnace bed material rises steadily to the normal operating temperature of 880℃.

[0014] The beneficial effects of this technical solution are as follows: I. The present invention provides an ignition method suitable for circulating fluidized bed boilers, which shortens the ignition time and saves ignition diesel consumption.

[0015] II. The ignition method for circulating fluidized bed boilers provided by this invention can reduce the boiler restart time after flameout and reduce losses in the field of cogeneration. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the circulating fluidized bed boiler in this invention; The components include: 1. Furnace; 2. Bed temperature sensor; 3. Pressure transmitter; 4. Air chamber; 5. Return feeder; 6. Ash discharge valve; 7. Return feeder fan; 8. Return feeder air chamber exhaust valve; 9. Fluidizing damper; 10. Ignition burner; 11. Ignition damper; 12. Pressure gauge; 13. Oil return valve; 14. Ignition oil pump; 15. Oil tank; 16. Primary air fan; 17. Primary air fan regulating damper; 18. Secondary air fan; 19. Secondary air fan regulating damper; 20. Exhaust fan; 21. Exhaust fan regulating damper; 22. Air preheater I; 23. Air preheater II; 24. Economizer; 25. Low-temperature superheater; 26. High-temperature superheater; 27. Cyclone separator; 28. Air preheater II regulating damper. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0018] It should be noted that when a component is referred to as being "mounted on," "fixed to," or "set on" another component, it can be directly on the other component or may have an intervening component present. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or may have an intervening component present.

[0019] It should also be noted that the directional terms such as left, right, up, and down in the embodiments of the present invention are only relative concepts or are based on the normal use state of the product, and should not be considered as restrictive.

[0020] like Figure 1 As shown, Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 all employ a circulating fluidized bed boiler, including a furnace 1, a wind chamber 4, a cyclone separator 27, and a return feeder 5. The wind chamber 4 is equipped with a pressure transmitter 3 and multiple bed temperature sensors 2. The upper end of the cyclone separator 27 is sequentially equipped with an air preheater 22, an air preheater 23, an economizer 24, a low-temperature superheater 25, and a high-temperature superheater 26. The lower end of the air preheater 22 is connected to the induced draft fan. The regulating damper 21 is connected to the induced draft fan 20. The lower end of the return feeder 5 is connected to the ash discharge valve 6, the return feeder fan 7, and the return feeder air chamber exhaust valve 8. The side wall of the first air preheater 22 is connected to the secondary air fan regulating damper 19 and the secondary air fan 18. The side wall of the second air preheater 23 is connected to the primary air fan 16 and the sequential air fan regulating damper 17. The side wall of the air chamber 4 is connected to the fluidization damper 9, the ignition burner 10, the ignition damper 11, the pressure gauge 12, the oil return valve 13, the ignition oil pump 14, and the oil tank 15.

[0021] Example 1 An ignition method suitable for circulating fluidized bed boilers includes the following steps: Step 1: Prepare fuel, start the return blower, and inject spare bed material. The thickness of the stationary bed material layer should be controlled at 450mm. The fuel particle size should be less than 10mm, with 15% of the fuel having a particle size less than 1mm. The carbon content of the fuel should be 2%. (The proportion of fuel with a particle size less than 1mm should be less than 20%. If this proportion is exceeded or higher, it is easy to be separated from the furnace during ignition and enter the tail dust collector, causing a reduction in bed material thickness and affecting the heating and ignition time. If the carbon content is greater than 2% or higher, under the action of newly added fuel at 550℃, after the bed temperature reaches 750℃ and completes ignition, it may cause deflagration, increasing the risk of coking.) Step 2: Conduct cold-state characteristic tests, including the following tests: (1) Inspection of electric doors, dampers and regulating baffles; (2) Measure the air volume and pressure head of the induced draft fan, primary air fan, return air fan and secondary air fan, and check whether the induced draft fan, primary air fan, return air fan and secondary air fan meet the nameplate parameters and can meet the hot operation requirements; (3) Measure the boiler's tightness; (4) Measure the empty bed resistance of the boiler and check the uniformity of air distribution by the air distribution plate; (5) Measure the critical fluidization air volume; (6) Verify the output of the coal feeder and assess the performance of the coal feeder system; (7) Performance test of material circulation system; (8) Start the induced draft fan and primary air fan to conduct an air plate resistance test; Step 3: After the dynamic characteristic test is completed, shut down the return fan, primary air fan, and induced draft fan. Quickly close the primary air fan inlet regulating damper, fluidizing air regulating damper, and induced draft fan inlet regulating damper, and observe the flatness of the static material layer in the furnace. After the overall flatness is achieved and there is no material pile-up, restart the induced draft fan, primary air fan, and return fan, maintain a negative pressure of -0.08 kPa, and gradually increase the opening of the primary air fan inlet regulating damper until the entire bed material layer is boiling without any "dead zones". Record the primary air fan current, primary air volume, primary air fan inlet regulating damper opening, and bed pressure value under this state. The primary air volume at this time is the minimum fluidizing air volume under this material layer. Step 4: Adjust the ignition damper to 100% full opening and the fluidization damper to 10% opening. Ignite according to the ignition procedure: turn on the purge, turn off the purge, advance the electronic ignition gun, turn on the high-energy electronic burner to ignite, open the oil valve, observe the ignition through the observation mirror, and then withdraw the electronic ignition gun. Step 5: After ignition, when the bed temperature change rate is less than 1℃ / min, adjust the opening of the return oil valve to reduce the pressure from the initial oil pressure of 0.8Mpa to 1.0Mpa, increasing the pressure by 0.2Mpa per adjustment. When the average temperature of the furnace bed reaches 450℃, open the exhaust valve of the return feeder air chamber to 60%, reducing the air chamber pressure from 11Kpa to 6Kpa. Step 6: When the average temperature of the furnace bed material reaches 550℃, pulse coal feeding is carried out: Start the coal feeder, adjust the speed to 100r / m, run for 3 minutes and then stop. Observe the oxygen content of the flue gas. When the original oxygen content drops to 2% and then shows an upward trend, start the coal feeder again. Step 7: When the average temperature of the furnace bed reaches 700℃ using pulse coal feeding, adjust the coal feeder speed to 120 r / m for continuous coal feeding. When the average temperature of the furnace bed rises to 750℃, increase the opening of the primary air fan inlet regulating damper by 3000 m³ / min based on the minimum fluidizing air volume. 3 When the average temperature of the furnace bed reaches 850℃, the secondary air fan is started to maintain the oxygen content of the flue gas at no less than 8%; Step 8: Slowly close the exhaust valve of the return material air chamber: (1) Adjust the opening of the exhaust valve of the return material air chamber to 50%, increase the air chamber pressure to 7 kPa, and maintain it for 10 minutes; (2) Adjust the opening of the exhaust valve of the return material air chamber to 40%, increase the air chamber pressure to 8 kPa, and maintain it for 10 minutes; (3) Adjust the opening of the exhaust valve of the return material air chamber to 30%, increase the air chamber pressure to 9 kPa, and maintain it for 10 minutes; (4) Adjust the opening of the exhaust valve of the return material air chamber to 20%, increase the air chamber pressure to 10 kPa, maintain for 30 minutes, and gradually increase the temperature of the circulating ash in the return material to 600℃. (5) Adjust the opening of the exhaust valve of the return material air chamber to 10%, increase the air chamber pressure to 11 kPa, maintain for 30 minutes, and the temperature of the circulating ash in the return material gradually rises to 750℃. (6) When the exhaust valve of the return feeder air chamber is closed to 0%, the average temperature of the furnace bed material rises steadily to the normal operating temperature of 880℃. Increase the pressure and gradually increase the circulating ash volume. When the temperature drops to 750℃, reduce the volume by 2000m³. 3 To increase the primary air volume by 100 m³ / h, increase the coal feeder speed to 150 r / min. When the average temperature change rate of the furnace bed is +5℃ / min and continues to increase, increase the opening of the primary air fan inlet regulating damper by 3000 m³ / h. 3 The primary air volume is increased by 1 / h, and the opening of the secondary air fan inlet regulating damper is increased to maintain the oxygen content of the flue gas at no less than 6% until the exhaust valve is completely closed.

[0022] Example 2 The difference between this embodiment and Embodiment 1 is that in step one, the thickness of the static bed material layer is controlled at 500mm, and the proportion of fuel with a particle size of less than 1mm is 15%.

[0023] Example 3 The difference between this embodiment and Embodiment 1 is that in step one, the thickness of the static bed material layer is controlled at 550mm, and the proportion of fuel with a particle size of less than 1mm is 10%.

[0024] Comparative Example 1 The difference between this comparative example and Example 1 is that in step one, the thickness of the static bed material layer is controlled at 600 mm, and the proportion of fuel with a particle size of less than 1 mm is 25%.

[0025] Comparative Example 2 The difference between this comparative example and Example 1 is that in step one, the thickness of the stationary bed material layer is controlled at 400mm.

[0026] Comparative Example 3 The difference between this comparative example and Example 1 is that in step one, the carbon content of the fuel is 3%.

[0027] Comparative Example 4 The circulating fluidized bed boiler uses existing ignition methods, including the following steps: (1) Start the induced draft fan, the blower, and the return fan; (2) Inject the ignition bed material; (3) Conduct cold-state characteristic tests; (4) Determine the minimum fluidization air volume for the bed material; (5) Adjust the ignition damper to 100% full opening and the fluidization damper to 10% opening, and ignite according to the operating procedure; (6) When the average bed temperature of the boiler furnace reaches 650℃, pulse coal feeding shall be carried out; (7) Adjust the amount of air and coal according to the changes in temperature and oxygen content, and raise the furnace temperature to the normal operating temperature of 850℃ in 6-8 hours.

[0028] The ignition time, ignition diesel consumption, and coking status of Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4; and the boiler restart time after flameout in the field of cogeneration; are shown in the table below.

[0029] As can be seen from the above, compared with existing ignition methods, the ignition time provided by this invention is shortened from 6 hours to 4.5 hours, and the diesel consumption for ignition is reduced from 4 tons to 3 tons. In the field of combined heat and power, the boiler restart time after flameout can be reduced from 4 hours to within 2 hours, thus reducing losses.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. An ignition method suitable for circulating fluidized bed boilers, characterized in that: Step 1: Prepare fuel, start the return blower, and pump in the spare bed material. The thickness of the stationary bed material layer should be controlled at 450-550mm. Step 2: Conduct cold-state characteristic tests; Step 3: Determine the minimum fluidizing air volume for the bed material; Step 4: Adjust the ignition damper to 100% full opening and the fluidization damper to 10% opening, then ignite according to the ignition procedure; Step 5: After ignition, adjust the oil pressure according to the rate of bed temperature rise; when the average temperature of the furnace bed reaches 450℃, open the exhaust valve of the return feeder air chamber to 60%, and reduce the air chamber pressure from 11kPa to 6kPa. Step 6: When the average temperature of the furnace bed material reaches 550℃, pulse coal feeding is carried out; Step 7: When the average temperature of the furnace bed reaches 700℃ using pulse coal feeding, adjust the coal feeder speed to 120 r / min for continuous coal feeding. When the average temperature of the furnace bed rises to 750℃, increase the opening of the primary air fan inlet regulating damper by 3000 m³ / min based on the minimum fluidizing air volume. 3 When the average temperature of the furnace bed reaches 850℃, the secondary air fan is started to maintain the oxygen content of the flue gas at no less than 8%; Step 8: Slowly close the exhaust valve of the return feeder's air chamber, increase the pressure, and gradually increase the circulating ash volume. When the average temperature of the furnace bed drops to 750℃, reduce the volume by 2000m³. 3 To increase the primary air volume by 100 m³ / h, increase the coal feeder speed to 150 r / min. When the average temperature change rate of the furnace bed is +5℃ / min and continues to increase, increase the opening of the primary air fan inlet regulating damper by 3000 m³ / h. 3 The primary air volume is increased by 1 / h, and the opening of the secondary air fan inlet regulating damper is increased to maintain the oxygen content of the flue gas at no less than 6% until the exhaust valve is completely closed.

2. The ignition method for a circulating fluidized bed boiler according to claim 1, characterized in that: In step one, the particle size of the fuel is less than 10 mm, and the carbon content of the fuel is less than 2%.

3. A method of igniting a circulating fluidized bed boiler according to claim 2, characterized in that: In step two, the cold-state characteristic test includes the following tests: (1) Inspection of electric doors, dampers and regulating baffles; (2) Measure the air volume and pressure head of the induced draft fan, primary air fan, return air fan and secondary air fan, and check whether the induced draft fan, primary air fan, return air fan and secondary air fan meet the nameplate parameters and can meet the hot operation requirements; (3) Measure the boiler's tightness; (4) Measure the empty bed resistance of the boiler and check the uniformity of air distribution by the air distribution plate; (5) Measure the critical fluidization air volume; (6) Verify the output of the coal feeder and assess the performance of the coal feeder system; (7) Performance test of the material circulation system; (8) Start the induced draft fan and primary air fan to conduct an air plate resistance test.

4. A method of igniting a circulating fluidized bed boiler according to claim 3, characterized in that: In step three, after the cold-state characteristic test is completed, the return fan, primary air fan, and induced draft fan are shut down. The inlet regulating damper of the primary air fan, the fluidizing air regulating damper, and the inlet regulating damper of the induced draft fan are quickly closed. The flatness of the stationary material layer in the furnace is observed. After the overall flatness is achieved and there is no material pile-up, the induced draft fan, primary air fan, and return fan are restarted. The negative pressure is maintained at -0.08 kPa. The opening of the primary air fan inlet regulating damper is gradually increased until the entire bed material layer is boiling without any "dead zones". The primary air fan current, primary air volume, primary air fan inlet regulating damper opening, and bed pressure value are recorded under this state. The primary air volume at this time is the minimum fluidizing air volume under this material layer.

5. A method of igniting a circulating fluidized bed boiler according to claim 4, characterized in that: In step four, ignition is performed according to the ignition procedure: turn on the purge, turn off the purge, advance the electronic ignition gun, turn on the high-energy electronic burner to ignite, open the oil valve, observe the ignition through the viewing mirror, and then withdraw the electronic ignition gun.

6. A method of igniting a circulating fluidized bed boiler according to claim 5, characterized in that: In step five, when the bed temperature change rate is less than 1℃ / min, the pressure is adjusted by closing the return oil valve, from the initial oil pressure of 0.8Mpa to 1.0Mpa, and then increased by 0.2Mpa / time.

7. The ignition method for a circulating fluidized bed boiler according to claim 6, characterized in that: In step six, pulse coal feeding is performed as follows: start the coal feeder, adjust the speed to 100 r / min, run for 3 minutes and then stop. When the oxygen content in the flue gas decreases and then shows an upward trend after decreasing to 2%, start the coal feeder again.

8. A method of igniting a circulating fluidized bed boiler according to claim 7, characterized in that: In step eight, the closing status of the exhaust valve in the return material device's air chamber is as follows: (1) Adjust the opening of the exhaust valve of the return material air chamber to 50%, increase the air chamber pressure to 7 kPa, and maintain it for 10 minutes; (2) Adjust the opening of the exhaust valve of the return material air chamber to 40%, increase the air chamber pressure to 8 kPa, and maintain it for 10 minutes; (3) Adjust the opening of the exhaust valve of the return material air chamber to 30%, increase the air chamber pressure to 9 kPa, and maintain it for 10 minutes; (4) Adjust the opening of the exhaust valve of the return material air chamber to 20%, increase the air chamber pressure to 10 kPa, maintain for 30 minutes, and gradually increase the temperature of the circulating ash in the return material to 600℃. (5) Adjust the opening of the exhaust valve of the return material air chamber to 10%, increase the air chamber pressure to 11 kPa, maintain for 30 minutes, and the temperature of the circulating ash in the return material gradually rises to 750℃. (6) When the exhaust valve of the return material chamber is closed to 0%, the average temperature of the furnace bed material rises steadily to the normal operating temperature of 880℃.

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