A device and method for preparing dry coal powder with particle size classification

Abstract

The invention discloses a device and method for preparing dry coal powder with particle size classification. The device comprises a pre-mill bin, a weighing coal feeder, a coal mill, a classifying dust collector, a coarse powder bin, a fine powder bin, a circulating fan, a monitoring station, a heat exchanger, a gas-liquid separator, an air blower, a combustion furnace, and a hot flue gas fan. The raw coal in the pre-mill bin falls into the coal mill after being measured by the weighing coal feeder, and the ground coal powder is transported to the classifying dust collector by mixed low-humidity hot air from the combustion furnace, the hot flue gas fan and the circulating fan to produce coarse powder and fine powder. After the dust is removed, the high-humidity hot air is pressurized by the circulating fan, and a part of it is returned to continue drying the coal powder, and the other part is discharged after passing through the heat exchanger and the gas-liquid separator in turn. The invention realizes low-cost classification of coarse coal powder and fine coal powder, resource utilization of waste fuel gas and discharged hot flue gas, and efficient recovery of water resources, and the device has large operation flexibility, high reliability, small equipment investment, high energy utilization efficiency, and remarkable water-saving effect.

Description

Technical Field

[0001] The present invention relates to the technical field of coal processing, and in particular to a device and method for preparing dry coal powder with particle size classification. Background Art

[0002] In the field of deep processing of coal, some process technologies have strict requirements on the particle size of raw coal powder. Coal powders of different particle sizes are suitable for feeding in different reaction zones or for different reactors, otherwise it will have a great negative impact on the processing process.

[0003] At present, the conventional dry pulverized coal preparation process usually uses online coal-fired flue gas or off-site boiler tail gas as the drying medium to evaporate the moisture in the pulverized coal and carry it away with the airflow. However, the main disadvantage of using online coal-fired flue gas is that some of the delayed-burning high-temperature coal particles fly to the dust collector with the airflow and burn the filter bag in a point-like manner, causing the dust removal function to fail. The off-site boiler tail gas is available in a small amount or has a high relative humidity in some plant areas, which is difficult to meet the drying requirements in the dry pulverized coal preparation process.

[0004] In addition, the conventional dry coal powder preparation process uses the dry medium airflow to blow the dry coal powder smaller than a certain particle size in the pulverizer out of the equipment to the dust removal bin, and then the dry coal powder is captured by the filter at the top of the dust removal bin and falls to the bottom of the bin by gravity for unloading. However, the particle size distribution of the produced coal powder is usually wide, and when the proportion of fine powder is high, it is difficult to meet the particle size index requirements of some pulverized coal deep processing technologies for feed coal powder.

[0005] It can be seen that in view of the shortcomings of the existing coal pulverizer pulverizing system, it is urgent to develop a coal powder preparation device and method that can efficiently remove most of the fine coal powder with small particle size, has low operating costs, and requires little modification to the existing coal powder making system. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a device and method for preparing dry coal powder with particle size classification, which realizes the low-cost classification of coarse coal powder and fine coal powder, the resource utilization of waste fuel gas and vented hot flue gas, and improves economic and environmental benefits.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A dry coal powder preparation device for particle size classification, comprising a pre-mill bin, a weighing coal feeder, a coal mill, a classification dust collector, a coarse powder bin, a fine powder bin, a circulating fan, a particle classification air control valve, a circulating air control valve, a monitoring station, an air discharge control valve, a heat exchanger, a gas-liquid separator, an air blower, a gas, a combustion furnace, and a hot flue gas fan;

[0009] The top of the weighing coal feeder is connected to the bottom of the pre-mill bin above the equipment through a powder-related pipeline, and the bottom of the weighing coal feeder is connected to the feed pipe opening of the coal mill below the equipment through a powder-related pipeline;

[0010] The feed pipe opening of the classifying dust collector is connected to the discharge pipe opening of the coal mill through a pipeline, the two discharge pipe openings at the bottom of the classifying dust collector are respectively connected to the coarse powder bin and the fine powder bin below the equipment through powder-related pipelines, and the exhaust pipe opening at the top of the classifying dust collector is connected to the inlet of the circulating fan through a pipeline;

[0011] The outlet of the circulating fan is respectively connected with the regulating pipe port of the coarse powder chamber in the lower part of the classifying dust collector, the air inlet pipe port at the bottom of the coal mill, and the hot fluid inlet of the heat exchanger through pipelines, and the corresponding pipelines are respectively connected with a classifying air regulating valve, a circulating air regulating valve, and an air release regulating valve, and a branch pipeline is connected on the pipeline between the outlet of the circulating fan and the air release regulating valve, and the other end of the branch pipeline is connected with the monitoring station;

[0012] The hot fluid outlet of the heat exchanger is connected to the inlet of the gas-liquid separator through a pipeline, the cold fluid inlet of the heat exchanger is connected to the outlet of the air blower through a pipeline, and the cold fluid outlet of the heat exchanger is connected to the air pipe port of the combustion furnace;

[0013] The gas pipe outlet of the combustion furnace is connected to the gas through a pipeline, the air distribution pipe outlet of the combustion furnace is connected to the outlet of the hot flue gas fan through a pipeline, the exhaust pipe outlet of the combustion furnace is connected to the circulating gas pipeline through a pipeline, and the circulating gas pipeline is a pipeline connecting the circulating air control valve and the coal mill.

[0014] Furthermore, the grading dust collector comprises a cone, a feed pipe, a cylinder, a chamber partition, a filter bag assembly, a backflush pipe and a head;

[0015] The bottom end of the cylinder is seamlessly connected to the large-diameter end of the cone, and the top end of the cylinder is seamlessly connected to the end cap to form a closed cavity;

[0016] The partition plate is vertically arranged in the closed cavity to divide the lower half of the cavity of the equipment into a coarse powder cavity with a smaller volume and a fine powder cavity with a larger volume. The bottom edge of the partition plate is seamlessly connected to the inner surface of the cone, the outer edges on both sides of the partition plate are seamlessly connected to the inner surface of the cylinder, and the top outer edge of the partition plate is not connected to any part of the equipment.

[0017] The small-diameter end of the cone is connected to the fine powder discharge pipe port; the bottom of the cone in the coarse powder chamber formed by the cone, the cylinder and the partition is connected to the coarse powder discharge pipe port, the upper part of the bottom of the cone is connected to the fluidizing gas pipe port, the bottom of the cylinder is connected to the lower pressure measuring pipe port, and the upper part of the bottom of the cylinder is connected to the feed pipe;

[0018] The filter bag assembly is detachably connected to the upper area of ​​the cylinder; the back-blowing pipe extends into the cylinder and is located above the filter bag assembly, and the back-blowing pipe is connected to an array of parallel nozzles and the nozzles are all aimed at the filter bag units of the filter bag assembly; the cover is connected to an inspection hole and an exhaust pipe opening; after the feed pipe extends into the cylinder from the outside of the equipment, a wear-resistant elbow with an outlet vertically downward is seamlessly connected to the end of the feed pipe.

[0019] Furthermore, an upper pressure measuring pipe opening and a manhole are connected to the cylinder, wherein the horizontal height of the contact point between the upper pressure measuring pipe opening and the cylinder is not lower than the highest point of the chamber partition.

[0020] Furthermore, the angle between all powder-related pipelines interconnected between the pre-mill bin, weighing coal feeder, coal mill, grading dust collector, coarse powder bin, and fine powder bin and the horizontal plane is not less than 35°.

[0021] Furthermore, the monitoring station can measure online the oxygen content, carbon monoxide content, pressure value, temperature value, and humidity value in the induced gas, and the relevant data can be read and displayed.

[0022] Furthermore, the heat exchanger is a partition wall heat exchanger.

[0023] Furthermore, the circulating fan, air blower and hot flue gas fan are all driven by variable frequency motors, and the particle classification air regulating valve, circulating air regulating valve and air release regulating valve are all automatically controlled valves.

[0024] A method for preparing dry coal powder comprises the following steps:

[0025] Step 1: Start the circulation fan and establish gas circulation by adjusting the opening of the circulation air control valve;

[0026] Step 2: While starting the air blower and introducing the fuel gas, start the ignition device in the combustion furnace to ignite the above two gases, and at the same time adjust the pressure in the whole system by adjusting the opening of the air release control valve;

[0027] Step 3: Start the hot flue gas fan, coal mill, and weighing coal feeder in sequence, and adjust the discharge rate of the raw coal in the pre-mill bin by the feed rate feedback value of the weighing coal feeder, and adjust the particle size distribution of the powder falling into the coarse powder bin and the fine powder bin by adjusting the opening of the particle classification air control valve;

[0028] Step 4: Collect the condensed water flowing out of the gas-liquid separator and discharge the gas phase; control the oxygen volume content measured online by the monitoring station within 12% by adjusting the frequency of the air blower motor;

[0029] Step 5: After the pulverizing task is completed, the weighing coal feeder is turned off, and the coal mill is turned off after it is inferred from relevant parameters that there is almost no powder in the coal mill;

[0030] Step 6: Then turn off the air blower and gas in turn, gradually reduce the frequency of the hot flue gas fan motor, and, under the premise of maintaining a stable pressure value in the monitoring station, reduce the opening of the air release control valve while increasing the opening of the circulating air control valve;

[0031] Step 7: After the hot flue gas fan is completely shut down, turn off the circulation fan.

[0032] Furthermore, the pre-grinding bin contains raw coal to be ground, which has been pre-treated for iron removal and the mass proportion of lumps with a particle size greater than 50 mm in the raw coal does not exceed 1%.

[0033] Furthermore, the fuel gas may be selected from, but not limited to, natural gas, coal gas, effluent gas, synthesis gas, refinery gas, or a mixture of the above, and the higher calorific value of the fuel gas shall not be less than 6MJ / Nm 3 .

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] First, in view of the different requirements of different pulverized coal deep conversion and utilization technologies for pulverized coal particle size distribution, the present invention sets up a classification dust collector device, which has a simple structure and realizes the integration of pulverized coal particle size classification and conveying gas dust removal. The device can simultaneously produce coarse pulverized coal and fine pulverized coal products, and the output ratio of the two products is flexible and the ratio can be flexibly controlled.

[0036] Second, in view of the abnormality that the dust collector bags in the device are frequently burned by the fast hot particles and become ineffective when pulverized coal is used as the fuel of the combustion furnace, the present invention selects gas as the fuel of the combustion furnace, and the gas includes but is not limited to a mixture of one or more of coal gas, synthesis gas, coke oven gas, and vent gas, so as to achieve the resource utilization of waste gas.

[0037] Third, the hot flue gas from outside the boundary is used as the first heat medium in the powder making and drying process, and the flue gas produced by gas combustion is used as the second heat medium. This not only realizes the deep resource utilization of the hot flue gas from outside the boundary, but also increases the operational elasticity and flexibility of the drying process.

[0038] Fourth, the installation of heat exchangers and gas-liquid separators in the device has greatly improved the overall energy utilization efficiency of the device, while achieving industrial water saving by recovering moisture from the raw coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0040] Figure 2 It is a schematic diagram of the equipment structure of the classifying dust collector 24 in the embodiment of the present invention;

[0041] Among them: 1. cone; 2. fine powder discharge pipe outlet; 3. coarse powder discharge pipe outlet; 4. fluidizing gas pipe outlet; 5. lower pressure measuring pipe outlet; 6. feed pipe; 7. cylinder; 8. chamber partition; 9. upper pressure measuring pipe outlet; 10. filter bag assembly; 11. backflush pipe fittings; 12. end cap; 13. inspection hole; 14. exhaust pipe outlet; 15. manhole; 21. pre-grinding bin; 22. weighing coal feeder; 23. coal mill; 24. graded dust collector; 25. coarse powder bin; 26. fine powder bin; 27. circulating fan; 28. particle classification air control valve; 29. ​​circulating air control valve; 30. monitoring station; 31. air release control valve; 32. heat exchanger; 33. gas-liquid separator; 34. air blower; 35. fuel gas; 36. combustion furnace; 37. hot flue gas fan. DETAILED DESCRIPTION

[0042] The present invention will be further explained below in conjunction with specific embodiments.

[0043] like Figure 1 As shown, the device of the present invention includes a pre-grinding bin 21, a weighing coal feeder 22, a coal mill 23, a classifying dust collector 24, a coarse powder bin 25, a fine powder bin 26, a circulating fan 27, a particle classification air control valve 28, a circulating air control valve 29, a monitoring station 30, an air release control valve 31, a heat exchanger 32, a gas-liquid separator 33, an air blower 34, a gas 35, a combustion furnace 36, and a hot flue gas fan 37.

[0044] The top of the weighing coal feeder 22 is connected to the bottom of the pre-mill bin 21 above the equipment through a powder-related pipeline, and the bottom of the weighing coal feeder 22 is connected to the feed pipe opening of the coal mill 23 below the equipment through a powder-related pipeline.

[0045] The feed pipe opening of the classifying dust collector 24 is connected to the discharge pipe opening of the coal mill 23 through a pipeline, the two discharge pipe openings at the bottom of the classifying dust collector 24 are respectively connected to the coarse powder bin 25 and the fine powder bin 26 below the equipment through powder-related pipelines, and the exhaust pipe opening at the top of the classifying dust collector 24 is connected to the inlet of the circulating fan 27 through a pipeline.

[0046] The outlet of the circulating fan 27 is connected to the regulating pipe port of the coarse powder chamber in the lower part of the classifying dust collector 24, the air inlet pipe port at the bottom of the coal mill 23, and the hot fluid inlet of the heat exchanger 32 through pipelines, and the particle classification air regulating valve 28, the circulating air regulating valve 29, and the air release regulating valve 31 are respectively connected and arranged on the corresponding pipelines, and a branch pipeline is connected and led out on the pipeline between the outlet of the circulating fan 27 and the air release regulating valve 31, and the other end of the branch pipeline is connected to the monitoring station 30.

[0047] The hot fluid outlet of the heat exchanger 32 is connected to the inlet of the gas-liquid separator 33 through a pipeline, the cold fluid inlet of the heat exchanger 32 is connected to the outlet of the air blower 34 through a pipeline, and the cold fluid outlet of the heat exchanger 32 is connected to the air pipe opening of the combustion furnace 36.

[0048] The gas pipe outlet of the combustion furnace 36 is connected to the gas 35 through a pipeline, the air distribution pipe outlet of the combustion furnace 36 is connected to the outlet of the hot flue gas fan 37 through a pipeline, and the exhaust pipe outlet of the combustion furnace 36 is connected to the circulating gas pipeline through a pipeline, and the circulating gas pipeline is a pipeline connecting the circulating air control valve 29 and the coal mill 23.

[0049] The angle between all the powder-related pipelines interconnected between the pre-mill bin 21, the weighing coal feeder 22, the coal mill 23, the classifying dust collector 24, the coarse powder bin 25, and the fine powder bin 26 and the horizontal plane is not less than 35°.

[0050] The pre-grinding bin 21 contains raw coal to be ground, which has been pre-treated for iron removal and in which the mass proportion of lumps with a particle size greater than 50 mm does not exceed 1%.

[0051] The weighing coal feeder 22 has the characteristics that the instantaneous coal feeding rate mean value can be read and displayed, and the coal feeding load can be flexibly adjusted.

[0052] The coal mill 23 is a low-speed coal mill, a medium-speed coal mill or a high-speed coal mill.

[0053] The classifying dust collector 24 is an integrated static device capable of classifying and separating coal powder according to particle size and removing dust from coal powder conveying gas.

[0054] The monitoring station 30 can measure the oxygen content, carbon monoxide content, pressure value, temperature value and humidity value in the drawn gas online, and the relevant data can be read and displayed.

[0055] The heat exchanger 32 is a partition type heat exchanger.

[0056] The circulating fan 27, the air blower 34 and the hot flue gas fan 37 are all driven by variable frequency motors, and the particle classification air regulating valve 28, the circulating air regulating valve 29 and the air release regulating valve 31 are all automatically controlled valves.

[0057] The fuel gas 35 may be selected from, but not limited to, natural gas, coal gas, effluent gas, synthesis gas, refinery gas, or a mixture of the above, and the high calorific value of the fuel gas 35 is not less than 6 MJ / Nm 3 .

[0058] The control method of the present invention is as follows,

[0059] Step 1: Start the circulation fan 27 and establish gas circulation by adjusting the opening of the circulation air control valve 29;

[0060] Step 2: while starting the air blower 34 and introducing the fuel gas 35, start the ignition device in the combustion furnace 36 to ignite the above two gases, and at the same time adjust the pressure in the whole system by the opening of the air release control valve 31;

[0061] Step 3: start the hot flue gas fan 37, the coal mill 23, and the weighing coal feeder 22 in sequence, and adjust the discharge rate of the raw coal in the pre-mill bin 21 by the feed rate feedback value of the weighing coal feeder 22, and adjust the particle size distribution of the powder falling into the coarse powder bin 25 and the fine powder bin 26 by adjusting the opening of the particle classification air control valve 28;

[0062] Step 4: Collect the condensed water flowing out of the gas-liquid separator 33 and discharge the gas phase. By adjusting the motor frequency of the air blower 34, the volume content of oxygen measured online by the monitoring station 30 is controlled within 12%;

[0063] Step 5: After the pulverizing task is completed, the weighing coal feeder 22 is turned off, and after it is inferred through relevant parameters that there is almost no powder in the coal mill 23, the coal mill 23 is turned off;

[0064] Step 6: Then turn off the air blower 34 and the gas 35 in turn, gradually reduce the motor frequency of the hot flue gas blower 37, and, under the premise of maintaining a stable pressure value in the monitoring station 30, reduce the opening of the air release control valve 31 while increasing the opening of the circulating air control valve 29;

[0065] Step 7: After the hot flue gas fan 37 is completely turned off, the circulation fan 27 is turned off.

[0066] like Figure 2 As shown, the graded dust collector 24 in the embodiment of the present invention includes a cone 1, a fine powder discharge pipe port 2, a coarse powder discharge pipe port 3, a fluidizing gas pipe port 4, a lower pressure measuring pipe port 5, a feed pipe 6, a cylinder 7, a chamber partition 8, an upper pressure measuring pipe port 9, a filter bag assembly 10, a backblowing pipe 11, a head 12, an inspection hole 13, an exhaust pipe port 14, and a manhole 15.

[0067] The bottom end of the cylinder 7 is seamlessly connected to the large-diameter end of the cone 1, and the top end of the cylinder 7 is seamlessly connected to the head 12, thereby forming a closed cavity including the head, the cylinder and the cone.

[0068] The chamber partition 8 is a flat plate or a curved plate, the bottom edge of the panel is seamlessly connected to the inner surface of the cone 1, the outer edges of both sides of the panel are seamlessly connected to the inner surface of the cylinder 7, and the top outer edge of the panel is the intersection line formed by the surface where the chamber partition 8 is located and the horizontal plane, and the top outer edge is not connected to any part of the equipment. The chamber partition 8 divides the lower half of the equipment into a coarse powder chamber with a smaller volume and a fine powder chamber with a larger volume.

[0069] The small-diameter end of the cone 1 is connected to the fine powder discharge pipe port 2. In the coarse powder chamber formed by the cone 1, the cylinder 7 and the chamber partition 8, the bottom of the cone 1 is connected to the coarse powder discharge pipe port 3, the upper part of the bottom of the cone 1 is connected to the fluidizing gas pipe port 4, the bottom of the cylinder 7 is connected to the lower pressure measuring pipe port 5, and the upper part of the bottom of the cylinder 7 is connected to the feed pipe 6.

[0070] The cylinder 7 is connected with an upper pressure measuring pipe port 9 and a manhole 15 , wherein the level of the contact point between the upper pressure measuring pipe port 9 and the cylinder 7 is not lower than the highest point of the chamber partition 8 .

[0071] The backflush pipe 11 is connected to the upper area of ​​the cylinder 7, and is connected to an array of parallel nozzles, and the nozzles are all aimed at the filter bag unit of the filter bag assembly 10. The support frame unit of the filter bag assembly 10 is detachably connected to the upper area of ​​the cylinder 7, and the filter bag unit is detachably connected to the support frame unit.

[0072] The sealing head 12 is provided with an inspection hole 13 and an exhaust pipe port 14 in communication.

[0073] After the feed pipe 6 extends from the outside of the equipment into the cylinder 7, a wear-resistant elbow with an outlet pointing vertically downward is seamlessly connected to the end of the feed pipe 6.

[0074] The lowest point of the filter bag assembly 10 is higher than the highest point of the chamber partition 8 and the distance between the two is L3. The highest point of the chamber partition 8 is higher than the highest point of the feed pipe 6 and the distance between the two is L2. The lowest point of the outlet end of the feed pipe 6 is higher than the highest point of the connection between the lower pressure measuring pipe port 5 and the cylinder 7 and the distance between the two is L1. The above dimensions must meet the following constraints, namely 400mm≤L1≤4000mm, 500mm≤L2≤5000mm, 300mm≤L3≤9000mm.

[0075] The cone angle of the cone 1 is a, the distance between the outer end of the fine powder discharge pipe 2 and the outer end of the exhaust pipe 14 is H, the outer diameter of the cylinder 7 is D, and the above dimensions must meet the following constraints, namely 45°≤a≤140°, 3000mm≤H≤25000mm, 1500mm≤D≤15000mm.

[0076] Working process:

[0077] The raw coal powder carried by the conveying gas flows into the coarse powder chamber of the equipment through the feed pipe 6 in the form of gas-solid two-phase flow. Under the flow-guiding effect of the vertical downward elbow at the end of the feed pipe 6, the coal powder with larger particle size is thrown to the bottom of the chamber under the action of inertia, and then discharged through the coarse powder discharge pipe port 3, while the fine coal powder is swept and entrained to the outside of the coarse powder chamber by the turbulent airflow. After leaving the coarse powder chamber area, the conveying airflow penetrates the filter bag assembly 10 and then is discharged through the exhaust pipe port 14. The fine powder intercepted on the filter bag assembly 10 falls to the bottom of the fine powder chamber and is discharged through the fine powder discharge pipe port 2 under the periodic backblowing of the backblowing gas from the backblowing pipe 11 and the action of gravity.

[0078] The specific embodiments listed above are intended to better illustrate the structural principles of the present invention, and do not limit the present invention. Any modifications, equivalent substitutions and improvements made within the scope of the present invention do not deviate from the scope defined by the claims of the present invention.

Claims

1. A device for preparing dry coal powder with particle size classification, characterized in that: It includes a pre-grinding bin (21), a weighing coal feeder (22), a coal mill (23), a classifying dust collector (24), a coarse powder bin (25), a fine powder bin (26), a circulating fan (27), a particle classification air regulating valve (28), a circulating air regulating valve (29), a monitoring station (30), an air discharge regulating valve (31), a heat exchanger (32), a gas-liquid separator (33), an air blower (34), a gas combustion furnace (36), and a hot flue gas fan (37); The top of the weighing coal feeder (22) is connected to the bottom of the pre-mill bin (21) above the weighing coal feeder (22) through a powder-related pipeline, and the bottom of the weighing coal feeder (22) is connected to the feed pipe opening of the coal mill (23) below the weighing coal feeder (22) through a powder-related pipeline; The feed pipe opening of the classifying dust collector (24) is connected to the discharge pipe opening of the coal mill (23) through a pipeline, the two discharge pipe openings at the bottom of the classifying dust collector (24) are respectively connected to the coarse powder bin (25) and the fine powder bin (26) below the classifying dust collector (24) through powder-related pipelines, and the exhaust pipe opening at the top of the classifying dust collector (24) is connected to the inlet of the circulating fan (27) through a pipeline; The outlet of the circulating fan (27) is respectively connected to the fluidizing gas pipe opening at the middle and lower part of the classifying dust collector (24), the air inlet pipe opening at the bottom of the coal mill (23), and the hot fluid inlet of the heat exchanger (32) through pipelines, and a classification air control valve (28), a circulating air control valve (29), and an air release control valve (31) are respectively connected and arranged on the corresponding pipelines, and a branch pipeline is connected and led out on the pipeline between the outlet of the circulating fan (27) and the air release control valve (31), and the other end of the branch pipeline is connected to the monitoring station (30); The hot fluid outlet of the heat exchanger (32) is connected to the inlet of the gas-liquid separator (33) through a pipeline, the cold fluid inlet of the heat exchanger (32) is connected to the outlet of the air blower (34) through a pipeline, and the cold fluid outlet of the heat exchanger (32) is connected to the air pipe opening of the combustion furnace (36); The gas pipe opening of the combustion furnace (36) is connected to the gas through a pipeline, the air distribution pipe opening of the combustion furnace (36) is connected to the outlet of the hot flue gas fan (37) through a pipeline, and the exhaust pipe opening of the combustion furnace (36) is connected to the circulating gas pipeline through a pipeline, and the circulating gas pipeline is a pipeline connecting the circulating air control valve (29) and the coal mill (23); The classifying dust collector (24) comprises a cone (1), a feed pipe (6), a cylinder (7), a chamber partition (8), a filter bag assembly (10), a backflush pipe (11) and a sealing head (12); The bottom end of the cylinder (7) is seamlessly connected to the large-diameter end of the cone (1), and the top end of the cylinder (7) is seamlessly connected to the end cap (12) to form a closed cavity; The chamber partition (8) is vertically arranged in the closed cavity to divide the lower half of the cavity of the classification dust collector (24) into a coarse powder cavity with a smaller volume and a fine powder cavity with a larger volume. The bottom edge of the chamber partition (8) is seamlessly connected to the inner surface of the cone (1), the outer edges of both sides of the chamber partition (8) are seamlessly connected to the inner surface of the cylinder (7), and the top outer edge of the chamber partition (8) is not connected to any part of the classification dust collector (24); The small-diameter end of the cone (1) is connected to the fine powder discharge pipe opening (2); the bottom of the cone (1) in the coarse powder chamber formed by the cone (1), the cylinder (7) and the chamber partition (8) is connected to the coarse powder discharge pipe opening (3); the cone (1) is connected to the fluidizing gas pipe opening (4), and the fluidizing gas pipe opening (4) is located above the coarse powder discharge pipe opening (3); the bottom of the cylinder (7) is connected to the lower pressure measuring pipe opening (5); the cylinder (7) is connected to the feed pipe (6), and the feed pipe (6) is located above the lower pressure measuring pipe opening (5); The filter bag assembly (10) is detachably connected to the upper area of ​​the cylinder (7); the back-blowing pipe (11) extends into the cylinder (7) and is located above the filter bag assembly (10); the back-blowing pipe (11) is connected to a plurality of parallel nozzles and the nozzles are all aligned with the filter bag units of the filter bag assembly (10); the sealing head (12) is connected to an inspection hole (13) and an exhaust pipe port (14); after the feed pipe (6) extends from the outside of the grading dust collector (24) into the cylinder (7), a wear-resistant elbow with an outlet pointing vertically downward is seamlessly connected to the end of the feed pipe (6).

2. The device for preparing dry coal powder with particle size classification according to claim 1, characterized in that: The cylinder (7) is connected with an upper pressure measuring pipe port (9) and a manhole (15), wherein the level of the connecting contact point between the upper pressure measuring pipe port (9) and the cylinder (7) is not lower than the highest point of the chamber partition (8).

3. The device for preparing dry coal powder with particle size classification according to any one of claims 1 to 2, characterized in that: The monitoring station (30) can measure the oxygen content, carbon monoxide content, pressure value, temperature value and humidity value in the drawn gas online, and the relevant data can be read and displayed.

4. The device for preparing dry coal powder with particle size classification according to any one of claims 1 to 2, characterized in that: The heat exchanger (32) is a partition type heat exchanger.

5. The device for preparing dry coal powder with particle size classification according to any one of claims 1 to 2, characterized in that: The circulating fan (27), the air blower (34), and the hot flue gas fan (37) are all driven by variable frequency motors, and the particle classification air control valve (28), the circulating air control valve (29), and the air release control valve (31) are all automatically controlled valves.

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