CN111617890A

CN111617890A - Coarse powder separator for separating and returning powder and working method thereof

Info

Publication number: CN111617890A
Application number: CN202010357832.4A
Authority: CN
Inventors: 石战胜; 敬旭业; 刘袖; 马治安; 董方; 彭丽; 李宗慧; 徐波
Original assignee: Huadian Electric Power Research Institute Co Ltd
Current assignee: Huadian Electric Power Research Institute Co Ltd
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2020-09-04

Abstract

The invention discloses a coarse powder separator for separating and returning powder and a working method thereof, wherein the coarse powder separator comprises an inlet pipe, a powder returning pipe, an outer shell, a sundry removing part, a primary baffle, a secondary baffle, an inner shell, an outlet, a middle shell, a centrifugal inner member, a mixer and a flow equalizing device; the lower end of the outer shell is connected with the inlet pipe and the powder return pipe, the outer shell is sleeved outside the middle shell, the middle shell is sleeved outside the inner shell, and the upper end of the outer shell is connected with the outlet; a flow equalizing device for equalizing a flow field and a centrifugal inner component for generating centrifugal force are arranged in the inlet pipe; the lower part of the middle shell is provided with a gap in the circumferential direction, the upper end of the middle shell is uniformly provided with a first-stage baffle in the circumferential direction, and the upper part of the outer shell is uniformly provided with a second-stage baffle in the circumferential direction; a plurality of impurity removing pieces are fixed on the inner wall of the outer shell, and a mixer is arranged on the upper portion of the outer shell. The invention realizes the separation of the returned powder and the separation of the returned powder, can lead the returned powder to be smooth without reverse channeling, has more flexible combination mode and is convenient to maintain.

Description

Coarse powder separator for separating and returning powder and working method thereof

Technical Field

The invention relates to the field of matched equipment for thermal power generation, cement, chemical industry, metallurgy and the like, in particular to a coarse powder separator for separating and returning powder.

Background

The coarse powder separator is an important device of a powder making system, mainly used for separating qualified coal powder and returning unqualified coal powder to a coal mill for re-grinding, and widely applied to power plants, cement industry, chemical industry and metallurgy industry. At present, the coarse powder separation technology used by the coal-fired power plant pulverizing system in China mainly comprises a radial separation technology and an axial separator. The two coarse powder separators generally have the problems of low efficiency, thick pulverized coal, poor pulverized coal uniformity, easy blockage by soft substances and the like, and particularly, the radial separator has poor blockage prevention function, so that the cleaning time interval is short. In addition, the powder returning and separation of the two separators are not separated, and mutual influence is easy to cause, which may be an important reason for low separation efficiency.

Disclosure of Invention

Aiming at the problems of difficulty in controlling fineness, large volume, uneven outlet concentration and the like of the conventional coarse powder separator, the invention provides the coarse powder separator for separating coarse powder from fine powder, the separation of powder particle sizes is realized by multi-stage separation and accurate increase of a flow equalizing device and a centrifugal separation module, and the deviation of outlet concentration is reduced by increasing a mixer. The coal pulverizer is arranged between the coal pulverizer and the powder pipe, and has the advantages of simple structure, small resistance, high separation efficiency, adjustable fineness, smooth powder return, no reverse channeling, soft substance removal and the like.

The technical scheme adopted by the invention for solving the problems is as follows: a coarse powder separator for separating and returning powder is characterized by comprising an inlet pipe, a powder returning pipe, an outer shell, impurity removing parts, a primary baffle, a secondary baffle, an inner shell, an outlet, a middle shell, a centrifugal inner component, a mixer and a flow equalizing device; the lower end of the outer shell is connected with the inlet pipe and the powder return pipe, the outer shell is sleeved outside the middle shell, an outer separation cavity is formed between the outer shell and the middle shell, the middle shell is sleeved outside the inner shell, an inner separation cavity is formed between the middle shell and the inner shell, and the upper end of the outer shell is connected with the outlet; a flow equalizing device for equalizing a flow field and a centrifugal inner component for generating centrifugal force are arranged in the inlet pipe; the lower part of the middle shell is provided with a gap in the circumferential direction, the upper end of the middle shell is uniformly provided with a primary baffle in the circumferential direction, and the upper part of the outer shell is uniformly provided with a secondary baffle in the circumferential direction; a plurality of impurity removing pieces are fixed on the inner wall of the outer shell, and a mixer is arranged on the upper portion of the outer shell.

Furthermore, the flow equalizing device comprises four channels, a slope plate is arranged in each channel, and the channels are made of wear-resistant materials.

Further, the centrifugal inner member is arranged above the flow equalizing device, the centrifugal inner member comprises twisted blades, a central shaft and a rotating shaft, the twisted blades are arranged on the central shaft, and the rotating shaft is vertically fixed with the central shaft; the number of the twisted blades is 4-10, and the twisted blades are uniformly distributed along the circumferential direction of the central shaft. The centrifugal inner member can be arranged at a distance from the outlet of the inlet pipe, can be exposed out of the outlet of the inlet pipe or can be flush with the outlet of the inlet pipe, and can be used independently or matched with a primary baffle.

Further, the distance between the flow equalizing device and the centrifugal inner member is 300 mm-1000 mm, the distance between the centrifugal inner member and the outlet of the inlet pipe is 0-1000 mm, the distance between the gap and the outlet of the inlet pipe is 0-500 mm, the number of the gaps is 10-30, the gaps are tangential, the tangential angle is 10-80 degrees, and the distance between the lower ends of the gaps and the lower end of the middle shell is 0-500 mm.

Furthermore, the powder return pipe is an inclined cylinder pipe with an inclination angle larger than 50 degrees, and the inlet pipe penetrates into the powder return pipe.

Further, the quantity of one-level baffle is 12~36, and the axle of one-level baffle runs through to the outside of shell body, adjusts the angle of one-level baffle in the outside of shell body, can play the separation effect alone, also can accomplish the separation with the cooperation of centrifugation internals.

Furthermore, the secondary baffles belong to small baffles, and the number of the secondary baffles is 18-36. The second-stage baffle can be matched with the first-stage baffle for use, can also be matched with the centrifugal inner component for completing separation, and can also be matched with the first-stage baffle and the centrifugal inner component for use.

Further, a top cover is arranged at the top end of the outer shell and connected with two outlets; the mixer comprises a stopper, blades and a shaft, wherein the shaft is arranged in the middle of the top cover, the lower end of the shaft is connected with the blades, the blades can be moving blades rotating along with the shaft or stationary blades, the projection size of the blades needs to be larger than the bottom of an outlet, the included angle between the blades and the shaft is 60-90 degrees, the number of the blades is 3-24, and the blades can be arranged in 1-3 layers; the stop is fixed to the inner wall of the outer casing and is disposed at a position flush with or slightly above the blade.

The working method of the coarse powder separator for separating the coarse powder from the returned powder is characterized by comprising the following steps of: powder and airflow mixture pass through the inlet pipe at a certain speed, the solid concentration and the airflow velocity are more uniform through the flow equalizing device, centrifugal force is generated through the centrifugal inner component, and because the rotation radius of coarse powder in the powder is large under the action of larger centrifugal force, the coarse powder can be more easily thrown to the inner wall of the middle shell, enters the outer separation cavity through the tangential gap on the middle shell, falls into the powder return pipe and is discharged; the soft substance can be broken by the flow equalizing device and the twisted blades of the centrifugal inner component, so that the first-stage baffle is prevented from being blocked and the blades of the mixer are prevented from being wound; the rest powder body continuously rises along the inner separation cavity, the gas and the solid touch a first-stage baffle to generate centrifugal force, the thicker powder body is thrown onto the outer shell body and touches a second-stage baffle, the powder body slides along the inner wall of the outer shell body under the action of gravity to the powder return pipe to be discharged, and part of soft substances are hung on the impurity removing piece in the falling process to prevent the powder return pipe from being blocked; the coal powder qualified by separation enters a mixer, is uniformly mixed and then enters an outlet, and then enters a boiler for combustion.

Compared with the prior art, the invention has the following advantages and effects:

(1) the volume is small, and the flexible transformation is convenient;

(2) the resistance is small, and the energy is saved obviously;

(3) the structure is simple, and the manufacture and the adjustment are convenient;

(4) the selection is flexible, and the separation can be carried out from two stages to three stages;

(5) has the function of removing soft substances;

(6) the separation is separated from the powder return, the gas blowby of the powder return pipe is prevented, the separation efficiency is higher, the separator is reduced, and the effective volume strength is increased. (ii) a

(7) The mixer is added, so that the concentration deviation of different outlets can be greatly reduced, the boiler combustion is better and the control is convenient.

Drawings

FIG. 1 is a schematic diagram of the coarse powder separator with separation and return fines separation according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram (front view, top view) of a current share apparatus according to an embodiment of the present invention;

FIG. 3 is a schematic structural view of a concentric inner member according to an embodiment of the present invention;

FIG. 4 is a schematic structural view of a slit in an embodiment of the present invention (front view, sectional view of plane A-A);

FIG. 5 is a schematic view of a stopper in an embodiment of the present invention;

FIG. 6 is a schematic structural view of a sundries removing part in the embodiment of the invention;

in the figure: the device comprises an inlet pipe 1, a powder return pipe 2, an outer shell 3, an impurity removing part 4, a primary baffle 5, a secondary baffle 6, an inner shell 7, an outlet 8, an impurity removing member I9, an impurity removing member I10, an impurity removing member I11, a middle shell 12, a centrifugal inner member 13, a mixer 14, a flow equalizing device 15, a top cover 16, an inner separation cavity 17, an outer separation cavity 18, a baffle plate 6, a baffle plate,

A gap 121,

Twisted blade 131, center shaft 132, rotation shaft 133,

A stopper 141, a blade 142, a shaft 143,

Channel 151, ramp plate 152.

Detailed Description

The present invention will be described in further detail below by way of examples with reference to the accompanying drawings, which are illustrative of the present invention and are not to be construed as limiting the present invention.

A coarse powder separator for separating and returning powder comprises an inlet pipe 1, a powder returning pipe 2, an outer shell 3, an impurity removing piece 4, a primary baffle 5, a secondary baffle 6, an inner shell 7, an outlet 8, a middle shell 12, a centrifugal inner member 13, a mixer 14 and a flow equalizing device 15; the lower end of the outer shell 3 is connected with the inlet pipe 1 and the powder return pipe 2, the outer shell 3 is sleeved outside the middle shell 12, an outer separation cavity 18 is formed between the outer shell 3 and the middle shell 12, the middle shell 12 is sleeved outside the inner shell 7, an inner separation cavity 17 is formed between the middle shell 12 and the inner shell 7, and the upper end of the outer shell 3 is connected with the outlet 8; a flow equalizing device 15 for equalizing a flow field and a centrifugal inner member 13 for generating centrifugal force are arranged in the inlet pipe 1; a gap 121 is formed in the circumferential direction at the lower part of the middle shell 12, primary baffles 5 are uniformly arranged in the circumferential direction at the upper end of the middle shell 12, and secondary baffles 6 are uniformly arranged in the circumferential direction at the upper part of the outer shell 3; a plurality of impurity removing members 4 are fixed to the inner wall of the outer housing 3, and a mixer 14 is provided at the upper portion of the outer housing 3, as shown in fig. 1.

Taking the separated coal powder as an example, the air and the coal powder from the coal mill enter from the inlet pipe 1 together, then rotate and rise through the lower part of the middle shell 12 and the inner separation cavity 17, part of coarse coal powder particles are discharged from the gap 121, and part of coarse powder particles are thrown to the side wall of the outer shell 3 after passing through the inner separation cavity 17, descend under the action of gravity and are discharged from the powder return pipe 2, and fine coal powder particles are discharged from the outlet 8. Generally, soft sundries in a linear shape (such as plastic wires and cotton wires) or a sheet shape (such as plastic sheets and cotton sheets) are mixed in the pulverized coal, the soft sundries are easy to cause blocking between the baffle and the rotating shaft, and the soft sundries can be broken by the flow equalizing device 15 and the centrifugal inner member 13, so that the problem that the baffle of the coarse powder separator is easy to block and block is effectively solved.

The flow equalizing device 15 comprises four channels 151, a slope plate 152 is arranged in each channel 151, the material is wear-resistant, the slope angle of the slope plate 152 is 60-80 degrees, as shown in fig. 2, the slope angle comprises a front view and a top view respectively, and the flow equalizing device mainly has the advantages that the gas-solid concentration entering the inlet pipe 1 is uniform, and the fluid speed and the cross-section speed are consistent.

The centrifugal inner member 13 is arranged above the flow equalizing device 15, the centrifugal inner member 13 comprises twisted blades 131, a central shaft 132 and a rotating shaft 133, the twisted blades 131 are arranged on the central shaft 132, and the rotating shaft 133 is vertically fixed with the central shaft 132; the number of the twisted blades 131 is 4-10, and the twisted blades 131 are uniformly distributed along the circumferential direction of the central shaft 132. The centrifugal internals 13 may be located at a distance from the outlet of the inlet pipe 1, may be exposed from the outlet of the inlet pipe 1 or may be flush, and the centrifugal internals 13 may be used alone or in combination with the primary baffle 5 to produce a primary separation, as shown in fig. 3.

The distance between the flow equalizing device 15 and the centrifugal inner member 13 is 300 mm-1000 mm, the distance between the centrifugal inner member 13 and the outlet of the inlet pipe 1 is 0-1000 mm, the distance between the gap 121 and the outlet of the inlet pipe 1 is 0-500 mm, the number of the gaps 121 is 10-30, as shown in fig. 4, the gaps are tangential, the tangential angle beta is 10-80 degrees, and the distance H1=0 mm-500 mm between the lower end of the gap 121 and the lower end of the middle shell 12.

The powder return pipe 2 is an inclined cylinder pipe with an inclination angle larger than 50 degrees, and the inlet pipe 1 penetrates into the powder return pipe 2.

The quantity of one-level baffle 5 is 12~36, and the axle of one-level baffle 5 runs through to the outside of shell body 3, adjusts the angle of one-level baffle 5 in the outside of shell body 3, can play the separation effect alone, also can accomplish the separation with the cooperation of centrifugation inner member 13. The second-stage baffle 6 belongs to a small baffle, and the number of the second-stage baffles 6 is 18-36. The secondary baffle 6 can be used with the primary baffle 5, can also be used with the centrifugal internals 13 to complete separation, and can also be used with both the primary baffle 5 and the centrifugal internals 13, as shown in fig. 1.

A top cover 16 is arranged at the top end of the outer shell 3, and the top cover 16 is connected with two outlets 8; the mixer 14 comprises a stopper 141, blades 142 and a shaft 143, as shown in fig. 5, the shaft 143 is arranged in the middle of the top cover 16, the lower end of the shaft 143 is connected with the blades 142, the included angle between the blades 142 and the shaft 143 is α =60 ° -90 °, the number of the blades 142 is 3-24, and 1-3 layers of the blades 142 are arranged; the stopper 141 is fixed on the inner wall of the outer casing 3, and 1-2 layers of the stopper 141 are arranged. Gas and qualified powder enter, are stirred and mixed uniformly by the rotating or static blades 142, part of the powder is thrown to the stoppers 141, and is mixed at the side wall, and the uniformly mixed gas and powder are uniformly distributed to different outlets 8, so that the concentration distribution of the outlets 8 is ensured to be uniform.

The impurity removing part 4 is fixed at the lower part of the cone section of the outer shell 3, and in order to hang the separated soft material and prevent it from blocking the powder return pipe 2, the shape of the impurity removing part 4 includes an impurity removing member i 9, an impurity removing member i 10, and an impurity removing member i 11, but is not limited to these three shapes, as shown in fig. 6.

The coarse powder separator for separating and returning powder adopts an advanced separation concept, increases centrifugal separation, basically eliminates impact separation, and has higher separation efficiency, higher uniformity index and the like; the soft substance can be broken, and the situation that the soft substance blocks the separator to influence the performance and the safety is prevented; a multi-stage separation mode is added, and the separation and energy saving effects can be achieved by flexibly allocating the materials according to the properties of the materials and the like in a single stage; the flow equalizing device is added, so that the gas and the powder entering the separator can be uniformly distributed; the top is added with a mixer 14 to ensure the uniform concentration of different outlets 8; in addition, the centrifugal inner member 13 and the gap 121, the primary baffle 5 and the secondary baffle 6 which are matched with the centrifugal inner member can be selected for use, namely, one, more or all of the centrifugal inner member 13 and the gap 121, the primary baffle 5 and the secondary baffle 6 which are matched with the centrifugal inner member can be selected; an alternative embodiment of the coarse powder separator that separates the separated and return fines is described below.

The first method is as follows: gas and solid powder enter through the inlet pipe 1, gas and solid are uniformly mixed through the flow equalizing device 15, then the gas and the solid enter the centrifugal inner component 13, the gas and the solid can remove soft substances through crushing, centrifugal force and primary separation are mainly generated, so that a rotary flow field is generated for the gas and the solid, as the rotary radius of coarse powder in the powder is large under the action of larger centrifugal force, the coarse powder rotates to the wall surface gap 121 of the middle shell 12, enters the outer separation cavity 18 to be separated, and is discharged from the powder return pipe 2, the remaining powder passes through the primary baffle 5 to generate secondary separation, coarse powder is thrown to the side wall, then the coarse powder enters the powder return pipe 2 through the outer separation cavity 18 by gravity to be discharged, the soft substances are thrown to the side wall, can be hung by the impurity removing piece 4 in the process of falling to the powder return pipe 2, in addition, a part of the coarse powder passes through the secondary baffle 6 to generate tertiary separation and is thrown to the side wall, coarse powder enters the powder return pipe 2 through the outer separation cavity 18 by means of gravity and is discharged, qualified fine powder is uniformly mixed through the mixer 14 and then flows out of the outlet 8, and the mixer 14 plays a role in uniformly mixing powder so as to ensure that the concentrations of different outlets 8 are the same.

The second method comprises the following steps: gas and solid powder enter through the inlet pipe 1, gas and solid are uniformly mixed through the flow equalizing device 15, then the gas and the solid enter the centrifugal inner component 13, the gas and the solid can remove soft substances through crushing, centrifugal force and primary separation are mainly generated, so that a rotary flow field is generated for the gas and the solid, as the rotary radius of coarse powder in the powder is large under the action of larger centrifugal force, the coarse powder rotates to the wall surface gap 121 of the middle shell 12, enters the outer separation cavity 18 to be separated, and is discharged from the powder return pipe 2, the remaining powder passes through the primary baffle 5 to generate secondary separation, coarse powder is thrown to the side wall, then the coarse powder enters the powder return pipe 2 through the outer separation cavity 18 by gravity, the soft substances are thrown to the side wall, can be hung by the impurity removing piece 4 in the process of falling to the powder return pipe 2, qualified fine powder is uniformly mixed through the mixer 14 and then is discharged from the outlet 8, and the mixer 14 plays a role of uniformly mixing, to ensure that the different outlet 8 concentrations are the same.

The third method comprises the following steps: gas and solid powder enter through the inlet pipe 1, gas and solid are uniformly mixed through the flow equalizing device 15, then the gas and the solid enter the centrifugal inner component 13, the gas and the solid can remove soft substances through crushing, centrifugal force and primary separation are mainly generated, so that a rotary flow field is generated for the gas and the solid, as the rotary radius of coarse powder in the powder is large under the action of large centrifugal force, the coarse powder rotates to the wall surface gap 121 of the middle shell 12, enters the outer separation cavity 18 to be separated, and is discharged from the powder return pipe 2, part of coarse powder is thrown to the side wall of the outer shell 3 from the top end of the middle shell 12, the coarse powder enters the powder return pipe 2 through the outer separation cavity 18 by gravity to be discharged, the soft substances are thrown to the side wall, can be hung by the impurity removing piece 4 in the process of falling to the powder return pipe 2, in addition, a part of the coarse powder passes through the secondary baffle 6 to generate tertiary separation, and is thrown to the side wall of the outer shell 3, the coarse powder enters the powder, qualified fine powder is uniformly mixed by the mixer 14 and then is discharged from the outlet 8, and the mixer 14 is used for uniformly mixing the powder so as to ensure that the concentrations of different outlets 8 are the same.

The method is as follows: the first method is as follows: gas and solid powder enter through the inlet pipe 1, gas and solid are uniformly mixed through the flow equalizing device 15, then the gas and the solid enter the centrifugal inner component 13, the gas and the solid can remove soft substances through crushing, centrifugal force and primary separation are mainly generated, so that the gas and the solid generate a rotary flow field, as the rotary radius of coarse powder in the powder is large under the action of larger centrifugal force, the coarse powder rotates to the wall surface gap 121 of the middle shell 12, enters the outer separation cavity 18 to be separated, and is discharged from the powder return pipe 2, part of coarse powder is thrown to the side wall of the outer shell 3 from the top end of the middle shell 12, the coarse powder enters the powder return pipe 2 through the outer separation cavity 18 by gravity, the soft substances are thrown to the side wall, can be hung by the impurity removing part 4 in the process of falling to the powder return pipe 2, qualified fine powder is uniformly mixed through the mixer 14 and then goes out from the outlet 8, and the mixer 14 plays a role of, to ensure that the different outlet 8 concentrations are the same.

The fifth mode is as follows: gas and solid powder pass through import pipe 1 and get into, make the gas-solid misce bene through flow straightener 15, later through one-level baffle 5, produce the primary separation, the limit wall is got rid of to thick powder, then the middlings gets into back powder pipe 2 through outer separation cavity 18 and discharges by gravity, soft material is got rid of the limit wall, the in-process that falls back powder pipe 2 can be hung by edulcoration piece 4, in addition, partly middlings passes through second grade baffle 6 in addition, produce the secondary separation, the limit wall of getting rid of shell body 3, the middlings gets into back powder pipe 2 and discharges through outer separation cavity 18 by gravity, qualified farine goes out from export 8 after the blender 14 misce bene, blender 14 effects of blender play powder misce, it is the same to ensure that different export 8 concentrations.

The method six: gas and solid powder pass through import pipe 1 and get into, make the gas-solid misce bene through flow straightener 15, later through one-level baffle 5, produce the primary separation, the limit wall is got rid of to thick powder, then the middlings gets into back powder pipe 2 and discharges through outer separation cavity 18 by gravity, soft material is got rid of the limit wall, the in-process that falls back powder pipe 2 can be hung by edulcoration piece 4, qualified farine goes out from export 8 after 14 misce benes of blender, 14 effects of blender play powder misce bene, it is the same to ensure the 8 concentrations in different exports.

Those not described in detail in this specification are well within the skill of the art.

Although the present invention has been described with reference to the above embodiments, it should be understood that the scope of the present invention is not limited thereto, and that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. The coarse powder separator for separating and returning powder is characterized by comprising an inlet pipe (1), a powder returning pipe (2), an outer shell (3), impurity removing pieces (4), a primary baffle (5), a secondary baffle (6), an inner shell (7), an outlet (8), a middle shell (12), a centrifugal inner member (13), a mixer (14) and a flow equalizing device (15); the lower end of the outer shell (3) is connected with the inlet pipe (1) and the powder return pipe (2), the outer shell (3) is sleeved outside the middle shell (12), an outer separation cavity (18) is formed between the outer shell (3) and the middle shell (12), the middle shell (12) is sleeved outside the inner shell (7), an inner separation cavity (17) is formed between the middle shell (12) and the inner shell (7), and the upper end of the outer shell (3) is connected with the outlet (8); a flow equalizing device (15) for equalizing a flow field and a centrifugal inner member (13) for generating centrifugal force are arranged in the inlet pipe (1); a gap (121) is formed in the circumferential direction at the lower part of the middle shell (12), primary baffles (5) are uniformly arranged in the circumferential direction at the upper end of the middle shell (12), and secondary baffles (6) are uniformly arranged in the circumferential direction at the upper part of the outer shell (3); a plurality of impurity removing pieces (4) are fixed on the inner wall of the outer shell (3), and a mixer (14) is arranged on the upper portion of the outer shell (3).

2. The meal separator of claim 1 wherein the flow straightener (15) comprises four channels (151) and a ramp plate (152) is provided in each channel (151).

3. The meal separator of claim 1 wherein the centrifugal inner member (13) is disposed above the flow equalization device (15), the centrifugal inner member (13) comprises twisted blades (131), a central shaft (132) and a rotating shaft (133), the twisted blades (131) are disposed on the central shaft (132), the rotating shaft (133) is fixed perpendicular to the central shaft (132); the number of the twisted blades (131) is 4-10, and the twisted blades (131) are uniformly distributed along the circumferential direction of the central shaft (132).

4. The coarse powder separator for separating and returning powder according to claim 1 or 3, wherein the distance between the flow equalizing device (15) and the centrifugal inner member (13) is 300-1000 mm, the distance between the centrifugal inner member (13) and the outlet of the inlet pipe (1) is 0-1000 mm, the distance between the gap (121) and the outlet of the inlet pipe (1) is 0-500 mm, and the number of the gaps (121) is 10-30.

5. The coarse powder separator for separating the coarse powder from the returned powder as claimed in claim 1, wherein the number of the primary baffles (5) is 12-36, the shaft of the primary baffles (5) penetrates to the outside of the outer shell (3), and the number of the secondary baffles (6) is 18-36.

6. The coarse powder separator for separating and returning powder as claimed in claim 1, characterized in that the top end of the outer casing (3) is provided with a top cover (16), and two outlets (8) are connected to the top cover (16); the mixer (14) comprises a stopper (141), blades (142) and a shaft (143), the shaft (143) is arranged in the middle of the top cover (16), the lower end of the shaft (143) is connected with the blades (142), an included angle between each blade (142) and the shaft (143) ranges from 60 degrees to 90 degrees, the number of the blades (142) ranges from 3 to 24, and 1 to 3 layers of the blades (142) are arranged; the stopper (141) is fixed on the inner wall of the outer shell (3).

7. A method of operating a meal separator with separation and return fines separation as claimed in any one of claims 1-6, characterized by the following steps: powder and airflow mixture pass through the inlet pipe (1) at a certain speed, the solid concentration and the gas-solid flow speed are more uniform through the flow equalizing device (15), centrifugal force is generated through the centrifugal inner component (13), coarse powder in the powder has large rotating radius under the action of larger centrifugal force, is thrown to the inner wall of the middle shell (12), enters the outer separation cavity (18) through the tangential gap (121) on the middle shell (12), and falls into the powder return pipe (2) to be discharged; the soft substance is broken by the flow equalizing device (15) and the twisted blades (131) of the centrifugal inner component (13) to prevent the first-stage baffle (5) from being blocked and prevent the blades (142) winding the mixer (14); the residual powder continuously rises along the inner separation cavity (17), the gas and the solid touch the first-stage baffle (5) to generate centrifugal force, the thicker powder is thrown onto the outer shell (3) and touches the second-stage baffle (6), and slides along the inner wall of the outer shell (3) under the action of gravity to the powder return pipe (2) for discharging, and part of soft substances are hung on the impurity removing piece (4) in the falling process to prevent the powder return pipe (2) from being blocked; the coal powder qualified by separation enters a mixer (14), is uniformly mixed and then enters an outlet (8), and then enters a boiler for combustion.