Circulating fluidized bed boiler for purely burning furfural residues and flow state reconstruction method of circulating fluidized bed boiler

Abstract

The invention discloses a circulating fluidized bed boiler purely burning furfural residues and a flow state reconstruction method of the circulating fluidized bed boiler. The flow state reconstruction of the circulating fluidized bed boiler aiming at the furfural residues is creatively realized. A secondary air lower annular air bellow (13) and a secondary air upper annular air bellow (14) are respectively arranged on the outer side wall of the hearth (2) at the dense-phase area (11); the air distribution quantity of a secondary air lower branch air pipe (15) is equal to that of the secondary air upper annular air bellow (14); the ratio of the secondary air distribution quantity to the primary air distribution quantity in the hearth is 55: 45; the shrinkage ratio of the hearth (2) on the dense-phase area (11) is 40%, a furfural residue feeding port (17) is formed in the outer side wall of the hearth (2) between the secondary air lower annular air bellow (13) and the secondary air upper annular air bellow (14), and the pressure intensity at the furfural residue feeding port (17) in the dense-phase area (11) of the hearth (2) is 0 through the air inducing capacity of an induced draft fan (19); and the utilization value of the biomass fuel is expanded.

Description

Technical Field

[0001] The invention relates to a circulating fluidized bed boiler, in particular to a circulating fluidized bed boiler for pure burning furfural slag and a fluid state reconstruction method thereof. Background Art

[0002] Furfural slag, as a biomass material, is a biomass waste generated when furfural is extracted. There is acid residue in the furfural slag, which contains sulfur and chlorine components and is rich in alkali metals. It has the characteristics of high moisture content and low calorific value. How to treat furfural slag in an environmentally friendly way is a difficult problem that relevant enterprises and environmental protection departments urgently need to solve. At present, there is a way to burn furfural slag through a small-capacity chain furnace, but this treatment method has the defect of limited furfural slag treatment capacity and cannot meet the large-scale furfural slag treatment requirements of the market. At the same time, due to the characteristics of furfural slag, there is also the problem of easy slagging in the furnace during combustion. How to develop a circulating fluidized bed boiler system suitable for pure burning of furfural slag through the circulating fluidized bed boiler technology with fluid state reconstruction, and the treatment of furfural slag covers 10-62 tons per hour (based on 45% moisture content), so as to achieve the ability to digest furfural slag in large quantities and turn waste into treasure to produce steam with a pressure of 3.82-13.73MPa, has become a difficult problem that urgently needs to be solved on site.

[0003] Furfural slag has a small particle size and a light specific gravity. When it burns in the furnace, there is a lack of large particles to stabilize the furnace bed pressure and bed temperature. The suspended combustion share in the upper part of the furnace is relatively large. The conventional circulating particle flow rate of 5 meters per second in the circulating fluidized bed furnace is completely unsuitable for the combustion and heat transfer of furfural slag fuel; the fuel has a high alkali metal content, the K2O content in the ash is about 15%, and the fuel ash has a low melting point, which is easy to produce adhesion in the furnace, resulting in poor circulation and fluidization of the fuel in the furnace; the primary air ratio of the conventional circulating fluidized bed boiler design is about 50-60%. The function of the primary air is mainly to ensure the fluidization of the combustion particles in the furnace, and the function of the secondary air is to ensure the fluidization of the combustion particles in the furnace. The main purpose is to strengthen the mixed combustion of fuels, but for the circulating fluidization of furfural slag, due to the fine particle size and small specific gravity of furfural slag, there are few coarse particles in the lower part, and the upper combustion share must be increased. How to adapt to the characteristics of the large upper combustion share in the furnace, and how to design the primary and secondary air ratio to meet the characteristics of furfural slag combustion, all require exploration and experimentation; in addition, in the process of transporting a large amount of furfural slag into the furnace, it is necessary to ensure normal circulation and fluidization in the furnace, and to avoid the occurrence of smoke return and fire when the light furfural slag enters the furnace to the greatest extent, which is also another difficult problem that needs to be solved on site.

[0004] Furfural slag has a low calorific value (1400-2200 kcal / kg) and a moisture content of 40-60%. Therefore, a large amount of flue gas will be produced after the combustion of furfural slag. The alkali metal content of furfural slag is high, and a small amount of acid, sulfur and chlorine remain. The high alkali metal content will lead to a low ash melting point, and the heating surface in the tail flue is prone to slagging, ash accumulation and corrosion, especially at the position of the last stage air preheater. The moisture in the flue gas is more likely to form condensation, which in turn causes low-temperature corrosion and even blockage together with the ash. In view of these characteristics, how to design and layout the tail flue has become a difficult problem that needs to be solved on site.

[0005] The fluidization technology of circulating fluidized bed boiler originated and developed under the condition of coal-fired fuel. The boiler system and fuel combustion flow pattern construction are all based on coal-fired fuel. Furfural slag fuel is essentially different from coal-fired fuel. How to reconstruct the flow pattern of furfural slag fuel in the furnace to adapt to the characteristics of large-scale combustion of furfural slag fuel has become a task that needs to be creatively completed in the design of pure furfural slag circulating fluidized bed boiler. Furfural slag has a small particle size and a light specific gravity. When it enters the furnace, the particles are mostly suspended in the upper part of the furnace, especially when the furfural slag is burned in the furnace. After the flue gas and the particulate matter in the flue gas enter the cyclone separator from the dilute phase area of ​​the furnace, they can easily escape from the exhaust port at the top of the cyclone separator, resulting in a significant reduction in the number of particles entering the cyclone separator for separation, which directly deteriorates the boiler circulation state and affects the combustion and heat transfer of the boiler. Therefore, how to design a reasonable furnace cross-sectional flow velocity, how to enhance the capture ability of the cyclone separator, reconstruct the flue gas flow field and separation efficiency in the cyclone separator, and match the entire boiler circulation system with the fuel are also an important part of the reconstruction of the circulating fluidization state of pure furfural slag. Summary of the invention

[0006] The present invention provides a circulating fluidized bed boiler for pure burning of furfural slag and a flow state reconstruction method thereof, explores a new path for efficiently burning and utilizing a large amount of low-quality furfural slag fuel resources, creatively realizes the flow state reconstruction of the circulating fluidized bed boiler for furfural slag, and expands the utilization methods of biomass fuels.

[0007] The present invention solves the above technical problems through the following technical solutions: A circulating fluidized bed boiler for pure combustion of furfural slag comprises a steel frame, on which a furnace, a cyclone separator and a tail flue are respectively arranged, the furnace is connected with the upper cylinder of the cyclone separator through the furnace upper outlet flue, the lower end of the upper cylinder is connected with the lower cone of the cyclone separator, the lower end of the lower cone is connected with the furnace through a material return device, a separator central outlet cylinder is arranged at the top of the upper cylinder, the other end of the separator central outlet cylinder is connected with the tail flue, and a dust collector, an induced draft fan and a chimney are connected in series in sequence at the outlet of the tail flue; the lower part of the furnace is a dense phase area, and the upper part of the furnace is a dilute phase area; a water-cooled air chamber is arranged at the lower end of the furnace, an air distribution plate is arranged at the connection between the water-cooled air chamber and the furnace, a primary wind box and an igniter are connected to the water-cooled air chamber; A secondary air lower annular bellows and a secondary air upper annular bellows are respectively arranged on the outer wall of the furnace at the phase zone, the secondary air lower annular bellows and the secondary air upper annular bellows are parallel to each other and arranged at intervals, the secondary air lower annular bellows is connected with the dense phase zone through the secondary air lower branch air duct, and the secondary air upper annular bellows is connected with the dense phase zone through the secondary air upper branch air duct, the air distribution volume of the secondary air lower branch air duct is equal to the air distribution volume of the secondary air upper annular bellows; the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace is 55:45; the contraction ratio of the dense phase zone of the furnace is 40%, and a furfural slag feeding port is arranged on the outer wall of the furnace between the secondary air lower annular bellows and the secondary air upper annular bellows, and the pressure at the furfural slag feeding port in the dense phase zone is made 0 by setting the induced draft capacity of the induced draft fan.

[0008] The fluidization velocity of the circulating fluidized particles in the furnace is 3.6-4.2 meters per second. When the circulating fluidized particles enter the upper outlet flue of the furnace from the furnace and then flow out from the separator throat C in the upper cylinder, its fluidization velocity is 30 meters per second.

[0009] The distance H2 between the furfural residue feeding port and the air distribution plate is 4.5 meters, the distance H1 between the outlet of the secondary air lower branch duct and the air distribution plate is 2.5 meters, and the distance H3 between the outlet of the secondary air upper branch duct and the air distribution plate is 5.5-6 meters; the height of the dense phase zone is 9-11 meters.

[0010] A first flue is connected to the central outlet tube of the cyclone separator, and the lower end of the first flue is connected to the second flue through a connecting flue. The first flue, the connecting flue and the second flue are arranged in an N shape. A first flue bottom end slag discharge tube is provided at the lower end of the first flue, and a second flue bottom end slag discharge tube is provided at the lower end of the second flue.

[0011] A high-temperature superheating screen and a medium-temperature superheating screen are arranged in the furnace, a low-temperature superheating screen and a high-temperature economizer are arranged in the first flue, and a low-temperature economizer and an air preheater are arranged in the second flue.

[0012] A method for reconstructing the fluid state of a circulating fluidized bed boiler burning pure furfural slag comprises the following steps: The first step is to set the induced draft power of the induced draft fan. When the induced draft fan is working, the pressure at the furfural slag feeding port in the dense phase area of ​​the furnace is 0; The second step is to set the contraction ratio of the furnace in the dense phase area to 40%; set the air inlet area of ​​the secondary air upper branch duct and the air inlet area of ​​the secondary air lower branch duct to be equal, and make the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace 55:45; Step 3: Control the fluidization velocity of circulating particles in the furnace at 3.6-4.2 meters per second, set the fluidization velocity of circulating particles in the upper cylinder of the cyclone separator to 5 meters per second, and set the fluidization velocity of circulating fluidized particles from the upper outlet flue of the furnace to the separator throat C at the upper cylinder of the cyclone separator to 30 meters per second, so that the cyclone separator circulates and fluidizes the flue gas particles with a particle size greater than 50 microns; Step 4: Set the temperature in the furnace to 740-780°C, the smoke temperature in the first flue to 500°C, and the smoke temperature at the outlet of the second flue to 140°C; set the flue gas flow rate in the first flue to 9 meters per second, and the flue gas flow rate in the second flue to 7 meters per second.

[0013] The fifth step is to set up a coarse particle bottom material adding system in the dense phase area of ​​the furnace. The coarse particle bottom material is added according to the pressure in the furnace to stabilize the furnace bed pressure.

[0014] The present invention is based on the existing circulating fluidized bed boiler technology route. Aiming at the characteristics of furfural slag fuel and the difficulties encountered when pure furfural slag is burned in a circulating fluidized bed boiler, the present invention starts from fluidization reconstruction to improve the bed quality, enhance the ash concentration in the furnace, reduce the tail ash amount in the flue gas, avoid high-temperature slagging corrosion of the heating surface and low-temperature corrosion and ash blocking, and develops a circulating fluidized bed boiler combustion technology with a furnace having low fluidization wind speed, large cross-section, small bed surface, high upper combustion share and high bed quality; the development of this product efficiently utilizes a large amount of idle furfural slag inferior resources, not only finds a way out for the digestion of furfural slag and realizes fuel substitution, but also expands the utilization value of biomass fuel and realizes low-carbon and high-efficiency operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 It is a schematic diagram of the structure of the present invention in a top view. DETAILED DESCRIPTION

[0016] The present invention is described in detail below in conjunction with the accompanying drawings: A method for reconstructing the fluid state of a circulating fluidized bed boiler for pure furfural slag combustion, comprising the following steps: The first step is to set the induced draft power of the induced draft fan 19 so that the pressure at the furfural slag feeding port 17 in the dense phase zone 11 of the furnace 2 is 0 when the induced draft fan 19 is working; The second step is to set the contraction ratio of the furnace 2 in the dense phase area 11 to 40%; set the air inlet area of ​​the secondary air upper branch duct 16 and the air inlet area of ​​the secondary air lower branch duct 15 to be equal, and make the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace 55:45; The third step is to control the fluidization velocity of the circulating particles in the furnace 2 to 3.6-4.2 meters per second, design the fluidization velocity of the circulating particles in the upper cylinder 3 of the cyclone separator to be 5 meters per second, and design the fluidization velocity of the circulating fluidized particles from the upper outlet flue 4 of the furnace to the separator throat C at the upper cylinder 3 of the cyclone separator to be 30 meters per second, so that the cyclone separator can realize the circulating fluidization of flue gas particles with a particle size greater than 50 microns; Step 4: The temperature in the furnace 2 is designed to be 740-780°C, the flue gas temperature in the first flue 4 is designed to be 500°C, and the flue gas temperature at the outlet of the second flue 5 is designed to be 140°C; the flue gas flow rate in the first flue 4 is designed to be 9 meters per second, and the flue gas flow rate in the second flue 5 is designed to be 7 meters per second.

[0017] Step 5: a coarse particle bottom material adding system is set in the dense phase zone 11 of the furnace 2, and coarse particle bottom material is added according to the pressure in the furnace to stabilize the bed pressure; A furfural slag feeding port 17 is provided at the front of the furnace 2, and the furfural slag feeding system outside the furnace adopts a two-stage spiral conveying method to push the furfural slag into the furnace; since this furnace type is purely for burning furfural slag, the design of inert bed material addition should be considered to ensure that the boiler maintains a normal bed pressure, and an inert bed material adding system is separately set up in the furnace, and an inert bed material adding port can be set on the return pipe, or it can be considered to add it in the feeding system in front of the furnace; for a 180-ton-per-hour boiler of the present invention, the furfural slag consumption is 50.87 tons per hour, and about 380,000 tons of furfural slag are digested annually.

[0018] A circulating fluidized bed boiler for pure furfural slag combustion comprises a steel frame 1, on which a furnace 2, a cyclone separator and a tail flue are arranged respectively, the furnace 2 is connected with an upper cylinder 3 of the cyclone separator through an upper furnace outlet flue 4, a lower cone 5 of the cyclone separator is connected to the lower end of the upper cylinder 3, the lower end of the lower cone 5 is connected with the furnace 2 through a return device 6, a separator center outlet cylinder 18 is arranged at the top of the upper cylinder 3, and a separator center outlet cylinder 18 is arranged at the upper end of the upper cylinder 3. The other end is connected to the tail flue, and the outlet of the tail flue is connected in series with a dust collector 31, an induced draft fan 19 and a chimney 32 in sequence; the lower part of the furnace 2 is a dense phase area 11, and the upper part of the furnace 2 is a dilute phase area 12; a water-cooled air chamber 7 is provided at the lower end of the furnace 2, and an air distribution plate 8 is provided at the connection between the water-cooled air chamber 7 and the furnace 2, and a primary air box 9 is connected to the water-cooled air chamber 7; a secondary air lower annular wind box 13 and a secondary air upper annular wind box are respectively provided on the outer side wall of the furnace 2 at the dense phase area 11 14, the secondary air lower annular wind box 13 and the secondary air upper annular wind box 14 are parallel to each other and spaced apart, the secondary air lower annular wind box 13 is connected to the dense phase area 11 through the secondary air lower branch air pipe 15, and the secondary air upper annular wind box 14 is connected to the dense phase area 11 through the secondary air upper branch air pipe 16, and the air distribution volume of the secondary air lower branch air pipe 15 is equal to the air distribution volume of the secondary air upper annular wind box 14; the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace is 55:45; the furnace 2 The shrinkage ratio in the dense phase area 11 is 40%. A furfural slag feed port 17 is provided on the outer wall of the furnace 2 between the secondary air lower annular wind box 13 and the secondary air upper annular wind box 14. By setting the induced draft capacity of the induced draft fan 19, the pressure at the furfural slag feed port 17 in the dense phase area 11 of the furnace 2 is 0, thereby ensuring that the furfural slag with a lighter specific gravity does not return and temper when entering the furnace; the furnace 2 is a membrane water-cooled furnace, the furnace cross section B2 is large, and the fluidization speed is designed to be 3.6 per second. -4.2 meters, to ensure that the fuel has enough residence time in the furnace to achieve full combustion; the lower dense phase zone is 9-11 meters high, all of which are welded with dense pins and coated with wear-resistant plastic; the water-cooled bed section B1 is 40% of the upper section of the furnace; because the fuel is rich in alkali metals and the ash melting point is low, the furnace temperature is designed to be controlled at 740-780℃ to prevent coking in the furnace; the high-temperature superheating screen and the medium-temperature superheating screen 16 are set in the furnace 2, and the high-temperature superheating screen and the medium-temperature superheating screen 16 are made of TP347H material, which can not only ensure the heat absorption of the superheater, but also avoid the high-temperature corrosion problem caused by being placed at the tail; the secondary air inlet is arranged on the front and rear walls of the upper part of the combustion chamber, and the inlet is square. The furfural slag feeding port 17 has a double-layer arrangement of secondary air above and below. The secondary air inlet should have large momentum and low resistance, and the penetration disturbance effect is strong, which improves the boiler combustion efficiency, controls CO production, and reduces the power of the secondary fan.

[0019] The fluidization velocity of the circulating fluidized particles in the furnace 2 is 3.6-4.2 meters per second, and the fluidization velocity of the circulating fluidized particles entering the upper outlet flue 4 of the furnace to the separator throat C at the upper cylinder 3 of the cyclone separator is 30 meters per second; the present invention adopts an adiabatic cyclone separator, increases the cross-section QD of the upper cylinder 3 of the cyclone separator, reduces the cross-section of the separator throat C, optimizes the design of the separator inlet, cone and center cylinder, and achieves a separation efficiency of d99<50μm and d50<20μm, which greatly improves the separator capture ability, prolongs the particle residence time in the furnace, and is beneficial to the combustion of furfural slag fine fuel.

[0020] A first flue 22 is connected to the central outlet tube of the cyclone separator 2. The lower end of the first flue 22 is connected to the second flue 23 through a connecting flue 24. The first flue 22, the connecting flue 24 and the second flue 23 are arranged in an N shape. A first flue bottom end slag discharge tube 25 is provided at the lower end of the first flue 22, and a second flue bottom end slag discharge tube 26 is provided at the lower end of the second flue 23, so that the slag in the flue can fall and be discharged in time.

[0021] A high-temperature superheating screen and a medium-temperature superheating screen 16 are arranged in the furnace 1, a low-temperature superheating screen 27 and a high-temperature economizer 28 are respectively arranged in the first flue 22, and a low-temperature economizer 29 and an air preheater 30 are respectively arranged in the second flue 23; the N-shaped flue not only reduces the large particles of ash brought into the rear vertical second flue 23, but also allows the low-temperature economizer 29 to be safely arranged in a staggered manner, thereby reducing steel consumption and controlling costs; because the fuel is fine and light, and the upper suspended combustion share is high, the primary and secondary air ratio is 45:55 to ensure full combustion of the fuel; the lateral pitch of the last-stage pipe box of the air preheater 30 is increased to avoid ash blockage in the last stage, and at the same time, the last two stages of pipes use enamel pipes with a base material of Q355GNH to avoid low-temperature corrosion and extend service life.

[0022] The distance H2 between the furfural slag feeding port 17 and the air distribution plate 8 is 4.5 meters, the distance H1 between the outlet of the secondary air lower branch duct 15 on the furnace 2 and the air distribution plate 8 is 2.5 meters, and the distance H3 between the outlet of the secondary air upper branch duct 16 on the furnace 2 and the air distribution plate 8 is 5.5-6 meters; the height of the dense phase zone 11 is 9-11 meters; the furfural slag is pushed into the furnace by a spiral conveyor, and the height of the furfural slag feeding port 17 is designed to be 5-6 meters from the height of the air distribution plate. This position has a certain height from the air distribution plate. Controlling the flue gas pressure at the feed port to the zero pressure point can ensure that the furfural slag can enter the furnace smoothly and stably without backflow of smoke or fire, effectively improving the stability and reliability of boiler operation. For existing circulating fluidized bed boilers, the furnace requires both fine particles for heat transfer and coarse particles for stabilizing the bed pressure and bed temperature. However, when burning furfural slag, the fuel basically does not have coarser particles. Therefore, a bottom material adding system is set on the furnace to add coarser bottom material into the dense phase area of ​​the furnace to ensure that the boiler can operate stably and reliably.

Claims

1. A circulating fluidized bed boiler for pure furfural slag combustion, comprising a steel frame (1), on which a furnace (2), a cyclone separator and a tail flue are arranged respectively, the furnace (2) is connected to an upper cylinder (3) of the cyclone separator through an upper furnace outlet flue (4), a lower cone (5) of the cyclone separator is connected to the lower end of the upper cylinder (3), the lower end of the lower cone (5) is connected to the furnace (2) through a material return device (6), and a separator center outlet cylinder is arranged at the top of the upper cylinder (3). (18), a tail flue is connected to the other end of the separator central outlet tube (18), and a dust collector (31), an induced draft fan (19) and a chimney (32) are connected in series at the outlet of the tail flue; the lower part of the furnace (2) is a dense phase zone (11), and the upper part of the furnace (2) is a dilute phase zone (12); a water-cooled air chamber (7) is provided at the lower end of the furnace (2), an air distribution plate (8) is provided at the connection between the water-cooled air chamber (7) and the furnace (2), and a primary wind box (9) is connected to the water-cooled air chamber (7); the characteristics are as follows: A secondary air lower annular wind box (13) and a secondary air upper annular wind box (14) are respectively arranged on the outer side wall of the furnace (2) at the dense phase zone (11). The secondary air lower annular wind box (13) and the secondary air upper annular wind box (14) are arranged parallel to each other and spaced apart. The secondary air lower annular wind box (13) is connected to the dense phase zone (11) through a secondary air lower branch air pipe (15). The secondary air upper annular wind box (14) is connected to the dense phase zone (11) through a secondary air upper branch air pipe (16). The secondary air lower branch air pipe (15) is connected to the dense phase zone (11). ) is equal to the air distribution volume of the secondary air upper annular wind box (14); the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace is 55:45; the contraction ratio of the furnace (2) in the dense phase area (11) is 40%, and a furfural slag feeding port (17) is provided on the outer wall of the furnace (2) between the secondary air lower annular wind box (13) and the secondary air upper annular wind box (14). By setting the induced draft capacity of the induced draft fan (19), the pressure at the furfural slag feeding port (17) in the dense phase area (11) of the furnace (2) is made zero.

2. A circulating fluidized bed boiler for pure burning of furfural slag according to claim 1, characterized in that: The fluidization velocity of the circulating fluidized particles in the furnace (2) is 3.6-4.2 meters per second, and the fluidization velocity of the circulating fluidized particles when flowing out from the separator throat C is 30 meters per second.

3. A circulating fluidized bed boiler for pure burning of furfural slag according to claim 1 or 2, characterized in that: The distance H2 between the furfural residue feeding port (17) and the air distribution plate (8) is 4.5 meters, the distance H1 between the outlet of the secondary air lower branch duct (15) and the air distribution plate (8) is 2.5 meters, and the distance H3 between the outlet of the secondary air upper branch duct (16) and the air distribution plate (8) is 5.5-6 meters; the height of the dense phase zone (11) is 9-11 meters.

4. A circulating fluidized bed boiler for pure burning of furfural slag according to claim 1 or 2, characterized in that: A first flue (22) is connected to the central outlet tube of the cyclone separator (2); the lower end of the first flue (22) is connected to the second flue (23) via a connecting flue (24); the first flue (22), the connecting flue (24) and the second flue (23) are arranged in an N shape; a first flue bottom end slag discharge tube (25) is provided at the lower end of the first flue (22); and a second flue bottom end slag discharge tube (26) is provided at the lower end of the second flue (23).

5. A circulating fluidized bed boiler for pure burning of furfural slag according to claim 4, characterized in that: A high-temperature superheating screen and a medium-temperature superheating screen (16) are arranged in the furnace (1), a low-temperature superheating screen (27) and a high-temperature economizer (28) are arranged in the first flue (22), and a low-temperature economizer (29) and an air preheater (30) are arranged in the second flue (23).

6. The method for fluid state reconstruction of a circulating fluidized bed boiler for pure furfural slag burning according to claim 2, characterized by the following steps: The first step is to set the induced draft power of the induced draft fan (19) so that when the induced draft fan (19) is in operation, the pressure at the furfural slag feeding port (17) in the dense phase region (11) of the furnace (2) is 0; Step 2: The contraction ratio of the furnace (2) in the dense phase region (11) is set to 40%; the air inlet area of ​​the secondary air upper branch duct (16) and the air inlet area of ​​the secondary air lower branch duct (15) are set to be equal, and the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace is set to 55:45; Step 3: Control the fluidization velocity of the circulating particles in the furnace (2) to 3.6-4.2 meters per second, set the fluidization velocity of the circulating particles in the upper cylinder (3) of the cyclone separator to 5 meters per second, and set the fluidization velocity of the circulating fluidized particles from the furnace upper outlet flue (4) to the separator throat C at the upper cylinder (3) of the cyclone separator to 30 meters per second, so that the cyclone separator circulates and fluidizes the flue gas particles with a particle size greater than 50 microns; Step 4: The temperature in the furnace (2) is set to 740-780° C., the smoke temperature in the first flue (4) is set to 500° C., and the smoke temperature at the outlet of the second flue (5) is set to 140° C.; the smoke flow rate in the first flue (4) is set to 9 meters per second, and the smoke flow rate in the second flue (5) is set to 7 meters per second.

7. In the fifth step, a coarse particle bottom material adding system is provided in the dense phase area (11) of the furnace (2). The coarse particle bottom material is added according to the pressure in the furnace to stabilize the furnace bed pressure.

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