Combustion system of pure combustion Zhundong coal circulating fluidized bed hot water boiler

Abstract

The utility model discloses a combustion system of a pure-combustion Zhundong coal circulating fluidized bed hot water boiler. The utility model aims to solve the problem that the existing pure combustion Zhundong coal can generate strong slagging and strong contamination, so that a boiler is frequently shut down for maintenance and cannot continuously and stably run for a long time. The device comprises an oil ignition device, a boiler front coal feeding pipe, an air distribution plate, an isobaric air chamber, a primary air chamber, a boiler bottom slag discharging pipe, a hearth, a secondary air box, a separator, a vertical pipe, a material returning device, a material returning leg, a water-cooling enclosure wall, an enclosure wall water-cooling screen, an inertia separation flue and a tail vertical shaft flue, wherein the exhaust end of the separator is communicated with the bottom of the water-cooling enclosure wall; a wall enclosure water-cooling screen is arranged in the water-cooling wall enclosure, the tail end of the water-cooling wall enclosure is communicated with the air inlet end of the inertia separation flue, and the air outlet end of the inertia separation flue is communicated with the air inlet end of the tail vertical shaft flue. The device is used for combustion of the circulating fluidized bed hot water boiler.

Description

Technical Field

[0001] The utility model relates to the technical field of circulating fluidized bed hot water boilers purely burning Zhundong coal, in particular to a combustion system of a circulating fluidized bed hot water boiler purely burning Zhundong coal. Background Art

[0002] Zhundong coal is produced in abundance in the Zhundong region of Xinjiang. The Zhundong coalfield in Xinjiang is the largest integrated coalfield discovered in China and the world so far, with abundant coal resources. Zhundong coal has the characteristics of easy ignition and easy burnout, as well as the advantages of low price and low pollution, but it also has the characteristics of high moisture, low ash content, medium calorific value, and extremely high content of alkali metal oxides, especially sodium oxide and potassium oxide. As a result, boilers burning Zhundong coal will have strong slagging and strong contamination in the temperature field range of 600-1000℃. Even if the boiler is mixed with Zhundong coal, there will be serious coking and ash sticking on the heating surface, blocking the flue, and high-temperature heating surface accompanied by high-temperature corrosion and other problems. For high-parameter steam boilers, there have been cases of blending in coal in China, but for hot water boilers, there have been no cases of pure combustion of Zhundong coal in China. Some boilers have a small amount of blending of Zhundong coal, but the entire boiler is completely blocked by coke slag, which is very hard and thick, seriously affecting the safe operation of the boiler; the operation time is very short and the boiler is forced to shut down to clean the coke slag, which is difficult to handle and has high maintenance costs. The losses and maintenance costs are far higher than the fuel costs saved by blending Zhundong coal. The abundant coal resources in the Zhundong region are not reasonably utilized and cannot reach the value they generate. Considering the above factors comprehensively, there is an urgent need for a circulating fluidized bed hot water boiler that purely burns Zhundong coal and its combustion system to solve the problem of strong slagging and strong contamination caused by pure combustion of Zhundong coal, while also achieving comprehensive utilization of the abundant coal resources in the Zhundong region and meeting the heating needs of the Zhundong region. Utility Model Content

[0003] In order to solve the problem that the existing pure Zhundong coal-fired circulating fluidized bed hot water boiler will have strong slagging and strong contamination, which leads to frequent shutdown of the boiler for maintenance and cannot operate continuously and stably for a long time, the utility model proposes a combustion system for a pure Zhundong coal-fired circulating fluidized bed hot water boiler.

[0004] The technical solution adopted by the utility model to solve the above technical problems is:

[0005] A combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal comprises an oil ignition device, a furnace front coal feeding pipe, an air distribution plate, an isobaric air chamber, a primary air chamber, a boiler bottom ash discharge pipe, a furnace, a secondary air box, a separator, a vertical pipe, a return device, a return leg, a water-cooled wall, a wall-wrapped water-cooled screen, an inertial separation flue and a tail shaft flue, the air distribution plate is arranged at the bottom of the furnace, the lower part of the air distribution plate is connected with the isobaric air chamber, the upper end of the boiler bottom ash discharge pipe passes through the isobaric air chamber and the air distribution plate and is connected with the bottom of the furnace, the lower end of the boiler bottom ash discharge pipe is connected with a slag cooler, the rear side of the isobaric air chamber is connected with a primary air chamber, the oil ignition device is arranged at the rear side of the primary air chamber, the furnace front coal feeding pipe is arranged At the lower part of the front wall of the furnace, the secondary air box is arranged around the lower and middle part of the furnace and on the upper side of the coal feeding pipe in front of the furnace. The air inlet end of the separator is connected with the upper exhaust end of the furnace, and the lower discharge end of the separator is connected with the feed end of the returner through a vertical pipe. The discharge end of the returner is connected with the lower part of the rear wall of the furnace through the return leg. The exhaust end of the separator is connected with the bottom of the water-cooled wall. A wall-wrapped water-cooled screen is arranged in the water-cooled wall. The tail end of the water-cooled wall is connected with the air inlet end of the inertial separation flue, and the air outlet end of the inertial separation flue is connected with the air inlet end of the tail vertical shaft flue. A high-temperature economizer, a low-temperature economizer and an air preheater are arranged in the tail vertical shaft flue from top to bottom.

[0006] Furthermore, the front and rear walls and side walls of the water-cooled wall are provided with wall-covering water-cooling screens, and the tops between two adjacent wall-covering water-cooling screens are provided with air-energy soot blowers.

[0007] Furthermore, the distance between two adjacent wall-wrapped water-cooling screens is greater than or equal to 500 mm.

[0008] Furthermore, the secondary air box is connected to the furnace through a plurality of branch pipes distributed on the front wall and the rear wall of the furnace.

[0009] Furthermore, the branch pipes are respectively connected to the outlet ends of the secondary air boxes, and the multiple branch pipes are staggered on the front wall and the rear wall of the furnace, and the number of branch pipes on the front wall is greater than or equal to the number of branch pipes on the rear wall. The wind speed at the outlet end of the secondary air box is 85-90m / s, and the distance from the air distribution plate is 3.2-4.2m.

[0010] Furthermore, the separator includes an inlet tangential acceleration section, a straight cylinder, an inverted cone and an exhaust center tube, the inlet end of the inlet tangential acceleration section is connected to the upper exhaust end of the furnace, the outlet end of the inlet tangential acceleration section is connected to an air intake end on one side of the upper part of the straight cylinder, and the outlet end of the inlet tangential acceleration section is inclined downward along the tangential direction of the straight cylinder, the inverted cone is arranged at the lower end of the straight cylinder, the lower end of the inverted cone is connected to the upper end of the riser, the exhaust center tube is arranged at the exhaust end at the top of the straight cylinder, and the exhaust center tube is eccentrically arranged with the center line of the straight cylinder.

[0011] Furthermore, the outlet end of the inlet tangential acceleration section is inclined downward by 9.5° along the tangential direction of the straight cylinder.

[0012] Furthermore, the height of the tangential acceleration section is 0.8 times the diameter of the straight cylinder, the height of the straight cylinder is 1.25 times its diameter, the throat flow velocity at the tangent point between the tangential acceleration section and the straight cylinder is designed to be 30m / s, the inclination angle between the height direction of the inverted cone and the vertical direction is 12°, and the insertion depth of the exhaust center tube is 0.35-0.4 times the height of the tangential acceleration section.

[0013] Furthermore, the cross-sectional area of ​​the air distribution plate is 0.4 times the cross-sectional area of ​​the furnace, and a large bell-shaped hood is used on the air distribution plate, the flow rate of the hood small hole is 35-40Nm / s, and the hood resistance is 2500pa.

[0014] Furthermore, the water-cooling wall is a membrane-type wall fully sealed welded structure, and a wear-resistant and fire-resistant plastic layer is laid on the inner wall of the water-cooling wall.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] 1. The circulating fluidized bed hot water boiler can efficiently burn pure Zhundong coal without blending, rationally and efficiently utilize local resources, and utilize the difficult-to-use Zhundong coal resources. The price of Zhundong coal fuel is low, which saves users a lot of fuel costs.

[0017] 2. The problem of short operation cycle of fluidized bed hot water boilers burning pure Zhundong coal is solved. Zhundong coal contains a large amount of alkali metal oxides, which is prone to strong contamination and strong slagging. The application of the utility model can completely solve the problem of short boiler operation cycle and forced shutdown for slag cleaning, dust cleaning and maintenance, so that the boiler can operate continuously and stably for a long time, improve the utilization rate of the boiler unit, and save users a lot of costs in boiler unit maintenance and care.

[0018] 3. When using a high-temperature adiabatic separator, the boiler can still operate stably for a long time, with higher combustion efficiency and higher thermal efficiency than the previous medium-temperature separation technology, saving fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The utility model is a schematic diagram of a combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal. DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects solved by the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0021] Specific implementation method 1: Combination Figure 1 1. The combustion system of a circulating fluidized bed hot water boiler burning purely Zhundong coal described in this embodiment comprises an oil ignition device 1, a furnace front coal feeding pipe 2, an air distribution plate 3, an isobaric air chamber 4, a primary air chamber 5, a boiler bottom ash discharge pipe 6, a furnace 7, a secondary air box 8, a separator 9, a riser 10, a return device 11, a return leg 12, a water-cooled wall 13, a wall water-cooled screen 14, an inertial separation flue 15 and a tail shaft flue 16. The air distribution plate 3 is arranged at the bottom of the furnace 7, and the lower part of the air distribution plate 3 is connected with the isobaric air chamber 4. The upper end of the boiler bottom ash discharge pipe 6 passes through the isobaric air chamber 4 and the air distribution plate 3 and is connected with the bottom of the furnace 7. The lower end of the boiler bottom ash discharge pipe 6 is connected with a slag cooler. The rear side of the isobaric air chamber 4 is connected with the primary air chamber 5. The oil ignition device 1 is arranged at the rear side of the primary air chamber 5. The coal pipe 2 is arranged at the lower part of the front wall of the furnace 7, the secondary air box 8 is arranged around the lower middle part of the furnace 7, and is arranged on the upper side of the coal feeding pipe 2 in front of the furnace, the air inlet end of the separator 9 is connected with the upper exhaust end of the furnace 7, the lower discharge end of the separator 9 is connected with the feed end of the returner 11 through the riser 10, the discharge end of the returner 11 is connected with the lower part of the rear wall of the furnace 7 through the return leg 12, the exhaust end of the separator 9 is connected with the bottom of the water-cooled wall 13, and the water-cooled wall 13 is provided with a wall water-cooled screen 14, the tail end of the water-cooled wall 13 is connected with the air inlet end of the inertial separation flue 15, the air outlet end of the inertial separation flue 15 is connected with the air inlet end of the tail shaft flue 16, and the tail shaft flue 16 is provided with a high-temperature economizer 17, a low-temperature economizer 18 and an air preheater 19 from top to bottom.

[0022] The front-of-furnace coal feeding pipe 2 is arranged at the lower part of the front wall of the furnace 7, and its upper part is connected to the front-of-furnace coal feeder through a metal expansion joint; the upper exhaust end of the furnace 7 is connected to the air inlet end of the separator 9 through a non-metallic expansion joint; a non-metallic expansion joint needs to be arranged inside the return leg 12; a non-metallic expansion joint is arranged in the inertial separation flue 15; the air preheater 19 is connected to the bottom of the low-temperature economizer 18 through a metal expansion joint.

[0023] The furnace 7 includes a lower dense phase zone 7-1, an upper dilute phase zone 7-2 and a furnace water-cooling screen 7-3. The upper dilute phase zone 7-2 is arranged on the upper part of the lower dense phase zone 7-1, and the furnace water-cooling screen 7-3 is inserted in the upper dilute phase zone 7-2 of the furnace. The lower end width of the lower dense phase zone 7-1 is the same as that of the upper dilute phase zone 7-2, and the depth is 0.4 times that of the upper part. The entire lower dense phase zone 7-1 shrinks to 0.4 times the original depth from top to bottom. The upper dilute phase zone 7-2 of the furnace and the furnace water-cooling screen 7-3 are the main heat transfer areas. The flue gas flow rate of the lower dense phase zone 7-1 and the upper dilute phase zone 7-2 of the furnace is 4.8m / s.

[0024] The separator 9 is a high temperature adiabatic large diameter separator.

[0025] Specific implementation method 2: Combination Figure 1 To explain this embodiment, the front and rear walls and side walls of the water-cooled wall 13 described in this embodiment are provided with wall-covering water-cooling screens 14, and the tops between two adjacent wall-covering water-cooling screens 14 are provided with air-energy soot blowers 20. The undisclosed technical features in this embodiment are the same as those in the first embodiment.

[0026] Specific implementation method three: Combination Figure 1 To illustrate this embodiment, the spacing between two adjacent wall-wrapped water-cooling panels 14 in this embodiment is greater than or equal to 500 mm. The undisclosed technical features in this embodiment are the same as those in the second embodiment.

[0027] Specific implementation method four: Combination Figure 1 To explain this embodiment, the secondary air box 8 in this embodiment is connected to the furnace 7 by a plurality of branch pipes distributed on the front wall and the rear wall of the furnace 7. The undisclosed technical features in this embodiment are the same as those in the first embodiment.

[0028] Specific implementation method five: Combination Figure 1 This embodiment is described. The branch pipes in this embodiment are respectively connected to the outlet ends of the secondary wind box 8. A plurality of branch pipes are respectively arranged on the front wall and the rear wall of the furnace 7 in an interlaced manner. The number of branch pipes on the front wall is greater than or equal to the number of branch pipes on the rear wall. The wind speed at the outlet end of the secondary wind box 8 is 85-90 m / s, and the distance from the air distribution plate 3 is 3.2-4.2 m. The undisclosed technical features in this embodiment are the same as those in the fourth embodiment.

[0029] Specific implementation method six: Combination Figure 1 This embodiment is described. The separator 9 described in this embodiment includes an inlet tangential acceleration section 9-1, a straight cylinder 9-2, an inverted cone 9-3 and an exhaust center tube 9-4. The inlet end of the inlet tangential acceleration section 9-1 is connected to the upper exhaust end of the furnace 7, and the outlet end of the inlet tangential acceleration section 9-1 is connected to the air intake end on one side of the upper part of the straight cylinder 9-2. The outlet end of the inlet tangential acceleration section 9-1 is tilted downward along the tangential direction of the straight cylinder 9-2. The inverted cone 9-3 is arranged at the lower end of the straight cylinder 9-2. The lower end of the inverted cone 9-3 is connected to the upper end of the vertical pipe 10. The exhaust center tube 9-4 is arranged at the exhaust end at the top of the straight cylinder 9-2, and the exhaust center tube 9-4 is eccentrically arranged with the center line of the straight cylinder 9-2. The undisclosed technical features in this embodiment are the same as those in the first embodiment.

[0030] The inlet tangential acceleration section 9-1 is arranged at an air inlet end on one side of the upper part of the straight cylinder 9-2, and is connected to the upper exhaust end of the furnace 7 through a non-metallic expansion joint.

[0031] Specific implementation method seven: Combination Figure 1 To explain this embodiment, the outlet end of the inlet tangential acceleration section 9-1 of this embodiment is inclined downward by 9.5° along the tangential direction of the straight cylinder 9-2. The undisclosed technical features of this embodiment are the same as those of the sixth embodiment.

[0032] Specific implementation method eight: Combination Figure 1 This embodiment is described. The height of the tangential acceleration section 9-1 in this embodiment is 0.8 times the diameter of the straight cylinder 9-2, and the height of the straight cylinder 9-2 is 1.25 times its diameter. The throat velocity at the tangent point between the tangential acceleration section 9-1 and the straight cylinder 9-2 is designed to be 30m / s, the inclination angle between the height direction of the inverted cone 9-3 and the vertical direction is 12°, and the insertion depth of the exhaust center tube 9-4 is 0.35-0.4 times the height of the tangential acceleration section 9-1. The undisclosed technical features in this embodiment are the same as those in the specific embodiment 6.

[0033] Specific implementation method nine: Combination Figure 1 This embodiment is described. The cross-sectional area of ​​the air distribution plate 3 in this embodiment is 0.4 times the cross-sectional area of ​​the furnace 7. At the same time, a large bell hood is used on the air distribution plate 3. The flow rate of the hood small hole is 35-40Nm / s, and the hood resistance is 2500pa. The undisclosed technical features in this embodiment are the same as those in the specific embodiment 1. Such a design enables the boiler to operate smoothly under low-load operation.

[0034] Specific implementation method ten: Combination Figure 1 To explain this embodiment, the water-cooling wall 13 in this embodiment is a membrane-type wall fully sealed welded structure, and a wear-resistant and fire-resistant plastic layer is laid on the inner wall of the water-cooling wall 13. The undisclosed technical features in this embodiment are the same as those in the first embodiment.

[0035] The water-cooled wall 13 is a membrane-type fully sealed welded structure, and the internal easily-worn area is paved with a wear-resistant and fire-resistant plastic layer, and the wall water-cooled screen 14 is arranged inside, and air-energy soot blowers 20 are set between each screen of the wall water-cooled screen 14, and the air-energy soot blowers need to blow soot continuously.

[0036] How it works

[0037] A combustion system of a circulating fluidized bed hot water boiler purely fueled by Zhundong coal comprises the following steps:

[0038] The Zhundong coal with a particle size of 0 to 8 mm is fed into the lower dense phase zone 7-1 of the furnace 7 through the coal feeding pipe 2 in front of the furnace. The primary hot air heated by the air preheater 19 enters the isobaric wind chamber 4 through the primary wind chamber 5, and then enters the lower dense phase zone 7-1 of the furnace through the air distribution plate 3. Under the action of the primary air, the Zhundong coal particles in the lower dense phase zone 7-1 of the furnace 7 and the circulating material returned to the furnace 7 through the return leg 12 are mixed together to form a bubbling bed state of high-concentration material. The material rises under the action of the primary hot air, and when it reaches the outlet end of the secondary wind box 8, it is mixed with the secondary hot air heated by the air preheater 19, and reaches the center of the furnace 7 under the action of the secondary hot air to eliminate the oxygen-depleted zone. The primary hot air accounts for 40% of the total air volume; the secondary air accounts for 60% of the total air volume. Under the combined action of the primary and secondary air, the material is then sent to the dilute phase zone 7-2 at the upper part of the furnace, and then the particles with a particle size greater than 200um adhere to the wall and reflux to form the internal circulation material. After the fine material with a particle size less than 200um enters the separator 9, 99.96% of the material is captured to form the external circulation material, and the remaining ultra-fine materials are carried by the flue gas into the water-cooled wall 13 and the wall water-cooled screen 14 in the form of fly ash. In the temperature field area of ​​the water-cooled wall 13 and the wall water-cooled screen 14, burning Zhundong coal will cause serious slagging and contamination. Therefore, it is necessary to avoid the deposition of fine ash on the water-cooled wall 13 and the water-cooled screen 14. The water-cooled screen 14 is arranged with a large intercept between each screen, and the spacing between each screen is ≥500mm. An air-energy soot blower 20 is required to be installed on the top of each screen. To ensure its soot blowing effect, the compressed air pressure of the air-energy soot blower is set to 0.8-1.2MPa, which effectively blows away the slag and ash formed in the temperature field area. The blown slag and ash will be separated through the inertial separation flue 15 and discharged out of the furnace through the ash discharge hole. The function of the inertial separation flue 15 is to separate the slag and ash blown away by the soot blower and discharge them out of the furnace to avoid affecting the heat exchange capacity of the economizer and the air preheater. In order to avoid serious slagging and contamination on other heating surfaces at the tail, it is necessary to ensure that the flue gas temperature at the outlet of the water-cooled wall is lower than 550℃. At this temperature, the alkali metals in the fly ash will not turn into gaseous salts to form strong slagging and strong contamination. Since the Zhundong coal fuel has a high alkali metal content, it is not recommended to use in-furnace desulfurization. The use of in-furnace desulfurization will accelerate the formation of calcium sulfate and other polluted heating surfaces on the tail heating surface of the boiler. The boiler economizer is 2-3m / s higher than that of conventional boilers, ensuring that the heating surface at the tail of the boiler is not easily contaminated. When the boiler is running, the furnace differential pressure is maintained at 7-8Kpa, and the oxygen content at the tail is 2-3%. At this time, the bed temperature is maintained at about 860℃, and the furnace differential pressure above the secondary air inlet is maintained at an average of 120Pa / m, ensuring efficient combustion of the boiler while better suppressing NO x Generation of.

[0039] The above shows and describes the basic principle and main features of the utility model and the advantages of the utility model. Those skilled in the art should understand that the utility model is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model may have various changes and improvements, which fall within the scope of the utility model to be protected. The scope of protection claimed by the utility model is defined by the attached claims and their equivalents.

Claims

1. A combustion system for a circulating fluidized bed hot water boiler burning pure Zhundong coal, characterized in that: The invention comprises an oil ignition device (1), a coal feeding pipe in front of a furnace (2), an air distribution plate (3), an isobaric air chamber (4), a primary air chamber (5), a boiler bottom ash discharge pipe (6), a furnace (7), a secondary air box (8), a separator (9), a vertical pipe (10), a return device (11), a return leg (12), a water-cooled wall (13), a wall water-cooled screen (14), an inertial separation flue (15) and a tail shaft flue (16). The air distribution plate (3) is arranged in the furnace. The bottom of the furnace (7) is connected to the bottom of the furnace (7), the lower part of the air distribution plate (3) is connected to the isobaric air chamber (4), the upper end of the boiler bottom ash discharge pipe (6) passes through the isobaric air chamber (4) and the air distribution plate (3) and is connected to the bottom of the furnace (7), the lower end of the boiler bottom ash discharge pipe (6) is connected to the slag cooler, the rear side of the isobaric air chamber (4) is connected to the primary air chamber (5), the oil ignition device (1) is arranged on the rear side of the primary air chamber (5), and the front coal feeding pipe (2) is arranged in the furnace (7) The secondary air box (8) is arranged at the lower part of the front wall around the middle and lower part of the furnace (7) and at the upper side of the coal feeding pipe (2) in front of the furnace. The air inlet end of the separator (9) is connected to the upper exhaust end of the furnace (7). The lower discharge end of the separator (9) is connected to the feed end of the return material device (11) through the vertical pipe (10). The discharge end of the return material device (11) is connected to the lower part of the rear wall of the furnace (7) through the return material leg (12). The exhaust end of the separator (9) is connected to the lower part of the rear wall of the furnace (7). The end is connected to the bottom of the water-cooled wall (13), a wall water-cooled screen (14) is arranged in the water-cooled wall (13), the tail end of the water-cooled wall (13) is connected to the air inlet end of the inertial separation flue (15), the air outlet end of the inertial separation flue (15) is connected to the air inlet end of the tail shaft flue (16), and the tail shaft flue (16) is provided with a high-temperature economizer (17), a low-temperature economizer (18) and an air preheater (19) in sequence from top to bottom.

2. According to claim 1, a combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal is characterized in that: The front and rear walls and side walls of the water-cooled wall (13) are provided with wall-covering water-cooling screens (14), and the tops between two adjacent wall-covering water-cooling screens (14) are provided with air-energy soot blowers (20).

3. According to claim 2, a combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal is characterized in that: The distance between two adjacent wall-wrapped water-cooling screens (14) is greater than or equal to 500 mm.

4. According to claim 1, a combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal is characterized in that: The secondary wind box (8) is connected to the furnace (7) via a plurality of branch pipes distributed on the front wall and the rear wall of the furnace (7).

5. The combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal according to claim 4 is characterized in that: The branch pipes are respectively connected to the outlet ends of the secondary wind box (8), and the plurality of branch pipes are respectively arranged in a staggered manner on the front wall and the rear wall of the furnace (7), and the number of branch pipes on the front wall is greater than or equal to the number of branch pipes on the rear wall. The wind speed at the outlet end of the secondary wind box (8) is 85-90 m / s, and the distance between the outlet end and the air distribution plate (3) is 3.2-4.2 m.

6. The combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal according to claim 1, characterized in that: The separator (9) comprises an inlet tangential acceleration section (9-1), a straight cylinder (9-2), an inverted cone (9-3) and an exhaust center tube (9-4); the inlet end of the inlet tangential acceleration section (9-1) is connected to the upper exhaust end of the furnace (7); the outlet end of the inlet tangential acceleration section (9-1) is connected to an air intake end on one side of the upper part of the straight cylinder (9-2); the outlet end of the inlet tangential acceleration section (9-1) is arranged to be inclined downward along the tangential direction of the straight cylinder (9-2); the inverted cone (9-3) is arranged at the lower end of the straight cylinder (9-2); the lower end of the inverted cone (9-3) is connected to the upper end of the vertical pipe (10); the exhaust center tube (9-4) is arranged at the exhaust end at the top end of the straight cylinder (9-2); and the exhaust center tube (9-4) is arranged eccentrically with respect to the center line of the straight cylinder (9-2).

7. The combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal according to claim 6, characterized in that: The outlet end of the inlet tangential acceleration section (9-1) is inclined downward by 9.5° along the tangential direction of the straight cylinder (9-2).

8. The combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal according to claim 6, characterized in that: The height of the tangential acceleration section (9-1) is 0.8 times the diameter of the straight cylinder (9-2), and the height of the straight cylinder (9-2) is 1.25 times its diameter. The throat flow velocity at the tangent point between the tangential acceleration section (9-1) and the straight cylinder (9-2) is designed to be 30 m / s. The inclination angle between the height direction of the inverted cone (9-3) and the vertical direction is 12°. The insertion depth of the exhaust center tube (9-4) is 0.35-0.4 times the height of the tangential acceleration section (9-1).

9. The combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal according to claim 1, characterized in that: The cross-sectional area of ​​the air distribution plate (3) is 0.4 times the cross-sectional area of ​​the furnace (7). At the same time, a large bell-shaped hood is used on the air distribution plate (3), the flow rate of the hood's small holes is 35-40Nm / s, and the hood resistance is 2500pa.

10. The combustion system of a circulating fluidized bed hot water boiler burning pure Zhundong coal according to claim 1, characterized in that: The water-cooling wall (13) is a membrane-type wall fully sealed welded structure, and a wear-resistant and fire-resistant plastic layer is laid on the inner side wall of the water-cooling wall (13).

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