JP5888131B2 - Vertical mill - Google Patents

Description

  The present invention relates to a vertical mill that pulverizes lumps such as coal and limestone into fine powder.

  In a coal-fired boiler using coal as fuel, massive coal is pulverized by a vertical mill or ball mill to form pulverized coal, and the pulverized coal is supplied together with primary air to a burner that is a combustion apparatus.

  A part of the vertical mill includes a housing, a rotary classifier that is housed in the upper part of the housing and rotates at a predetermined speed, a grinding table that is housed in the lower part of the housing and rotates at a predetermined speed, and a housing. A pressure roller unit supported by the pressure roller unit, and the pressure roller unit presses the rotatable pressure roller against the crushing table.

  Lumped coal is fed into the center of the crushing table from the coal supply pipe and supplied to the crushing table. The supplied massive coal moves to the outer periphery by the rotational centrifugal force of the pulverizing table, and is pulverized by being caught between the pressure roller and the pulverizing table in the process of moving the coal to the outer periphery of the pulverizing table. The pulverized pulverized coal is spouted by the primary air that is spouted from the primary air outlet around the pulverization table, and ascends in the housing as a pulverized coal flow.

  In the process in which the pulverized coal flow rises, the pulverized coal is subjected to centrifugal classification based on the centrifugal force of rotation and gravity classification in which gravity due to its own weight acts. Among the pulverized coal, the centrifugal force and gravity load acting on the coarse pulverized coal with a large particle size is large, so the pulverized coal is separated from the rising flow of the primary air, falls on the pulverization table, The pulverized coal flow after classification is subjected to collision classification by a classifier, and further, the coarse pulverized coal is separated from the pulverized coal, whereby pulverized coal having a small particle size is supplied to the burner together with the primary air.

  The conventional vertical mill does not have a structure for collecting coarse pulverized coal classified in the direction of the inner wall of the housing by centrifugal classification and collision classification, and supplying the recovered coarse pulverized coal to the pulverizing table again. Coarse pulverized coal classified by the machine was mixed again with the pulverized coal flow rising in the housing, which caused an increase in the mill differential pressure or a decrease in the classification efficiency of the classifier.

  In addition, an inverted truncated cone-shaped reject chute is provided below the classifier, and the coarse pulverized coal classified by the reject chute is collected, and the collected coarse pulverized coal is supplied again onto the pulverization table and classified by the classifier. There is also a vertical mill that separates the falling coarse coal and the pulverized coal flow rising in the housing to suppress the increase in the mill differential pressure, but in the case of a vertical mill with a reject chute, the rising pulverization The coal flow rises through the opening formed in the reject chute, but the area of the opening cannot be ensured properly, leading to an increase in the mill differential pressure.

  In addition, the coal powder that has reached the classification section is classified into pulverized coal having a predetermined particle diameter or less and coarse coal having a predetermined particle diameter or more with a rotary classification blade, and the classified coarse coal is collected with a cone and pulverized. As a classifying device and a vertical mill to be supplied again to the section, there is one disclosed in Patent Document 1.

JP 2002-18301 A

  In view of such circumstances, the present invention provides a vertical mill in which classified pulverized coal is efficiently supplied again onto a pulverization table to improve pulverization efficiency and suppress an increase in mill differential pressure.

  The present invention includes a housing that forms a classification chamber, a classifier provided at an upper portion of the classification chamber, a pulverization table that is provided at a lower portion of the classification chamber and is driven to rotate by a table driving device, and the pulverization table A plurality of pressure rollers pressed to crush the lump, a blowout port for blowing primary air from the periphery of the crushing table, a chute for supplying lump to the center of the crushing table, and around the chute A swivel having an inverted truncated cone-shaped reject chute and a conical cylinder portion provided between the reject chute and the crushing table and extending above the inner wall of the housing and having a plurality of holes formed in the peripheral surface And a cone-type mill that connects the reject chute to the conical cylinder portion so that the lower end of the reject chute is positioned at the lower end of the hole. That.

  The present invention also relates to a vertical mill in which an integrated flow path having an arc-shaped bottom portion extending in the generatrix direction of the internal surface is formed on the inner surface of the reject chute, and the integrated flow path and the hole communicate with each other. Is.

  Furthermore, the present invention relates to a vertical mill in which a recovery pipe extending toward the center of the crushing table is formed on the inner surface of the conical cylinder portion, and the recovery pipe and the accumulation channel communicate with each other. .

  According to the present invention, the housing forming the classification chamber, the classifier provided in the upper portion of the classification chamber, the pulverization table provided in the lower portion of the classification chamber and driven to rotate by the table driving device, and the pulverization A plurality of pressure rollers that are pressed onto the table to pulverize the lump, a blow-off port that blows out primary air from the periphery of the crushing table, a chute that supplies lump to the center of the crushing table, An inverted truncated cone-shaped reject chute provided around, and a conical cylinder portion provided between the reject chute and the pulverization table and extending above the inner wall of the housing and having a plurality of holes formed in the peripheral surface The reject chute is connected to the conical cylinder portion so that the lower end of the reject chute is positioned at the lower end of the hole. After the primary air blown up from the section does not mix with the classified pulverized coal, the increase in the mill differential pressure can be suppressed, and the primary air is contracted and accelerated by the conical cylinder section. By rapidly increasing the flow path area and applying a rapid centrifugal force, the classification efficiency can be improved, and the classified pulverized coal can be supplied again onto the pulverization table to improve the pulverization efficiency. Exhibits an excellent effect.

It is a schematic sectional elevation view of a vertical mill according to an embodiment of the present invention. It is the turning cone which concerns on the Example of this invention, (A) shows the top view of this turning cone, (B) has shown the perspective view of this turning cone. It is a reject chute concerning an example of the present invention, (A) shows a perspective view of the reject chute, (B) shows a top view of the reject chute, and (C) is an AA arrow of (A). A view is shown.

  Embodiments of the present invention will be described below with reference to the drawings.

  With reference to FIG. 1, a vertical mill 1 according to an embodiment of the present invention will be described.

  A cylindrical housing 3 is erected on a base 2 having a hollow structure or a leg structure, and a sealed space is formed by the housing 3. A crushing table 5 is provided in the lower part of the space via a speed reducer 4, and the crushing table 5 is driven and rotated by a table drive motor 6 via the speed reducer 4. The crushing table 5 is rotated at a constant speed or a variable speed by the table driving motor 6, and the speed reducer 4 and the table driving motor 6 constitute a table driving device 7.

  A table segment 9 having a concave groove 8 having a circular arc cross section is provided on the upper surface of the pulverizing table 5, and the table segment 9 is continuously provided in a ring shape. A ring-shaped pulverizing groove centering on is formed.

  A required number of, for example, three sets of pressure roller units 11 are provided radially from the rotation center of the crushing table 5 at intervals of 120 °. The pressure roller unit 11 has a pressure roller 12 and is tiltable about a pivot shaft 13. In addition, three sets of roller pressing devices 14 are provided below the housing 3 so as to penetrate the housing 3 radially. The roller pressure device 14 includes an actuator, for example, a hydraulic cylinder 15, and presses the pressure roller 12 against the concave groove 8 by the hydraulic cylinder 15.

  A primary air chamber 16 is formed below the grinding table 5, and a classification chamber 17 is located above the grinding table 5 inside the housing 3.

  A primary air supply port 18 is attached to the lower portion of the housing 3, and the primary air supply port 18 is connected to a blower (not shown) and communicates with the primary air chamber 16. Around the crushing table 5, primary air outlets 19 are provided on the entire circumference, and the outlets 19 are opposite to the circumferential direction of the crushing table 5, preferably in the direction opposite to the rotation direction of the crushing table 5. Inclined in the direction. The inclination angle of the outlet 19 is 45 ° or less. For example, the outlet 19 is inclined within a range of 30 ° to 45 ° so that the primary air spouted from the outlet 19 is sufficiently swirled. desirable.

  A raw material supply / discharge portion 21 is provided above the housing 3, and a pipe-like chute 22 is provided so as to penetrate the central portion of the raw material supply / discharge portion 21. The chute 22 extends into the housing 3 and has a lower end located above the center of the crushing table 5. A lump is supplied to the chute 22, and the supplied lump falls to the center of the crushing table 5.

  A rotating tube 23 is fitted on the chute 22, and the rotating tube 23 is rotatably supported by a rotating tube support portion 24 via a bearing 25. The rotary pipe 23 is provided with a pulley 26, and a belt 28 is wound between the pulley 26 and the pulley 27. The pulley 27 is fitted to the output shaft of the speed reducer 29. A classifier motor 31 is connected to 29. Thus, the rotary tube 23 is rotated by the classifier motor 31 through the speed reducer 29, the pulley 27, the belt 28, and the pulley 26.

  A number of blades 32 are radially attached to the rotary tube 23, and a classifier is formed by the rotary tube 23, the pulley 26, the pulley 27, the belt 28, the speed reducer 29, the classifier motor 31, and the blade 32. 33 is configured.

  The blades 32 have a strip shape and are arranged on the inverted conical curved surface at a predetermined angular pitch in the circumferential direction. The blade 32 is inclined from the lower end toward the upper end so as to be separated from the rotary tube 23, and is attached to the rotary tube 23 via a blade support portion 34.

  A swivel cone 35 is disposed above the crushing table 5, and a first classification chamber 17 a is defined below the swivel cone 35. The swivel cone 35 extends upward from the inner wall of the housing 3, and extends upward from the upper end of the conical cylinder part 36 and the conical cylinder part 36 that gradually decreases the flow area of the primary air upward. The conical cylinder part 36 is supported by the chute 22 via a turning cone support part 38. The diameter of the cylindrical portion 37 is larger than the diameter of the chute 22, and a primary air flow path is formed between the cylindrical portion 37 and the chute 22.

  Further, as shown in FIGS. 2A and 2B, the conical tube portion 36 is formed with, for example, three notches 39 so as not to interfere with the pressure roller 12, and the notches Between the holes 39, 39, for example, holes 41 are formed at three positions at intervals of 120 °. Further, a pipe-like recovery pipe 42 extending between the pressure rollers 12 and 12 from the hole 41 toward the lower end of the chute 22 is fixed to the inner surface of the conical cylinder portion 36. The recovery pipe 42 is inclined so that its axial center is directed downward and close to the center side, and the axial center of each recovery pipe 42 is located on an inverted conical curved surface and is divided into three equal parts in the circumferential direction. ing. The lower end of the recovery pipe 42 is positioned near the lower end of the chute 22, and the lower end opening 43 is parallel or substantially parallel to the axis of the chute 22, and is positioned between the pressure rollers 12, 12. ing.

  An inverted truncated cone-shaped reject chute 44 extending downward from the inner wall of the housing 3 is disposed between the swivel cone 35 and the classifier 33, and a second classifier is disposed above the reject chute 44. A chamber 17b is defined.

  FIG. 3 shows details of the reject chute 44. Accumulated channels 45 are formed at predetermined locations on the inner surface of the reject chute 44, for example, at three intervals of 120 °. The accumulation channel 45 has a circular arc at the bottom, extends in the generatrix direction of the conical curved surface, and is formed over the entire length in the vertical direction. The upper end portion of the reject chute 44 is a slope 46 formed by an inverted conical curved surface.

  The lower end of the reject chute 44 is located on the outer peripheral surface of the conical cylinder part 36, and the bottom of the accumulation channel 45 and the position of the hole 41 are coincident with each other, and the accumulation channel 45 and the recovery pipe 42 are aligned. It has come to communicate with. The lower end of the reject chute 44 is fixed to the outer peripheral surface of the conical cylinder part 36 by welding or the like, and is supported by the housing 3 and the conical cylinder part 36.

  The cylindrical portion 37 is an adjustment allowance for adjusting the distance between the classifier 33 and the turning cone 35 to a predetermined distance, and the vertical mill 1 to which the turning cone 35 is attached in advance. If the size is known, the conical cylinder part 36 may be produced so that the distance to the classifier 33 is a predetermined distance, and the cylindrical part 37 may be omitted.

  The raw material supply / discharge unit 21 is connected to a pulverized material supply pipe 47 for supplying pulverized powder, and the pulverized material supply pipe 47 is connected to a boiler burner (not shown). Yes.

  Next, the pulverization of coal in the vertical mill 1 will be described. In FIG. 1, the solid line indicates the flow of primary air, and the dotted line indicates the flow of coal.

  In the state where the crushing table 5 is rotated by the table driving motor 6 via the speed reducer 4 and primary air at around 200 ° C. is introduced into the primary air chamber 16 from the primary air supply port 18. Bulk coal is introduced from the chute 22. The lump coal flows down from the lower end of the chute 22 to the center of the crushing table 5 and is supplied onto the crushing table 5.

  The coal on the pulverizing table 5 is moved in the outer peripheral direction by centrifugal force generated by the rotation of the pulverizing table 5, is pulverized into pulverized coal composed of pulverized coal and pulverized coal, and is further centrifuged. Move to the outer periphery by force.

  The primary air introduced into the primary air chamber 16 from the primary air supply port 18 is inclined within a range of 30 ° to 45 ° so that, for example, sufficient swirling is provided around the pulverization table 5. The air is blown up from the blowout opening 19 formed. The flow rate of the primary air ejected from the outlet 19 is, for example, a minimum flow rate of 30 m / s or more, which is a minimum flow rate for blowing up pulverized coal and performing gravity classification of the pulverized coal, and a lower limit flow velocity at which gravity classification is impaired It is below 100m / s.

  The pulverized coal that has passed over the table segment 9 due to the centrifugal force generated by the rotation of the pulverization table 5 rides on the primary air spouted from the outlet 19 and swirls in the first classification chamber 17a as a pulverized coal flow. To rise.

  In the process of rising in the first classification chamber 17a, the coarse powder having a large particle size is separated from the pulverized coal flow by its own weight and falls onto the pulverizing table 5.

  Further, since the conical cylinder portion 36 of the swivel cone 35 whose diameter gradually decreases upward is provided above the crushing table 5, the pulverized coal flow rising in the first classification chamber 17a. Rises while turning along the inner surface of the conical cylinder portion 36, and gradually contracts and accelerates in the course of ascent.

  The pulverized coal flow reduced and accelerated in the process of passing through the conical cylinder portion 36 and the cylindrical portion 37 is jetted from the upper end of the cylindrical portion 37 into the second classification chamber 17b from the center. When the pulverized coal flow reaches the second classification chamber 17b, the flow passage area suddenly increases, is decelerated, and rises in the second classification chamber 17b in the outer circumferential direction.

  Since a large centrifugal force acts on the pulverized coal flow rising in the second classification chamber 17b with respect to the flow velocity, coarse powder that has not been classified in the first classification chamber 17a from the pulverized coal flow is centrifuged. The coarse powder is separated from the pulverized coal flow by its own weight and falls onto the inner surface of the reject chute 44 through the outer peripheral side of the second classification chamber 17b.

  The pulverized coal flow from which the coarse coal is separated by centrifugal force and gravity load in the second classifying chamber 17b reaches the classifier 33, and the classifier 33 further classifies the pulverized coal.

  By the classifier 33, pulverized coal having a predetermined particle size or less passes through the classifier 33, is sent out from the pulverized material feed pipe 47, and is supplied to a burner of a boiler (not shown). Coarse coal that has not been classified in the second classification chamber 17b is bounced by the blade 32, and is pushed back by the wind generated by the rotation of the blade 32. The pushed coarse pulverized coal falls on the inner surface of the reject chute 44 through the outer peripheral side of the second classification chamber 17b.

  Coarse coal that has fallen onto the inner surface of the reject chute 44 falls into any one of the accumulation channels 45 formed at three locations, and slides down in the accumulation channel 45. Coarse coal that has slid down in the accumulation channel 45 flows into the recovery pipe 42 through the hole 41, slides down in the recovery pipe 42, and enters the central portion of the crushing table 5 from the lower end opening 43. Fall.

  The coarse powder dropped from the recovery pipe 42 moves to the concave groove 8 by the rotational centrifugal force of the pulverizing table 5, is pulverized again by the pressure roller 12, and is blown up by primary air.

  As described above, in this embodiment, the conical swivel cone 35 is provided, the pulverized coal flow is reduced in the first classifying chamber 17a and increased in speed, and then suddenly increased in the second classifying chamber 17b. By increasing the flow path area and decelerating, a rapid centrifugal force can be applied to the pulverized coal flow, and the effect of centrifugal classification can be increased.

  Further, by providing the inverted truncated cone-shaped reject chute 44, the coarse pulverized coal classified in the second classification chamber 17b and the classifier 33 can be supplied again onto the pulverization table 5, The pulverization efficiency can be improved.

  Further, since the pulverized coal flow accelerated in the first classification chamber 17a is jetted from the center of the second classification chamber 17b, the pulverized coal flow rising in the second classification chamber 17b. And the coarse pulverized coal classified and lowered by the second classifying chamber 17b and the classifier 33 is not mixed with each other, and an increase in the mill differential pressure can be suppressed.

  In addition, the accumulation channel 45 is formed on the inner surface of the reject chute 44, and the coarse powdered coal classified by the second classification chamber 17b and the classifier 33 is passed through the accumulation channel 45 to the first classification chamber. Since it can supply now in 17a, the classified coarse coal can be collect | recovered without omission and a grinding | pulverization efficiency can be improved.

  Further, the recovery pipe 42 extending from the hole 41 of the conical cylinder portion 36 toward the lower end of the chute 22 is provided, and the coarse pulverized coal classified and recovered through the recovery pipe 42 is supplied to the crushing table 5. Since the supply to the central portion is performed again, the pulverized coal flow rising in the first classification chamber 17a and the recovered coarse pulverized coal are not mixed, and the increase in the mill differential pressure can be suppressed.

  Further, since the outlet 19 is inclined in a range of 30 ° to 45 ° so that sufficient swirl is given to the pulverized coal flow, the centrifugal force acting on the pulverized coal flow can be increased. Classifying efficiency can be improved.

DESCRIPTION OF SYMBOLS 1 Vertical mill 3 Housing 5 Grinding table 7 Table drive device 12 Pressure roller 17 Classifying chamber 19 Outlet 22 Chute 33 Classifier 35 Turning cone 36 Conical cylinder part 42 Recovery pipe 44 Rejecting chute 45 Accumulated flow path

Claims (3)

  A housing forming a classification chamber, a classifier provided in the upper part of the classification chamber, a pulverization table provided in a lower part of the classification chamber and driven to rotate by a table driving device, and a lump that is pressed onto the pulverization table A plurality of pressure rollers for pulverizing the object, a blow-off port for ejecting primary air from the periphery of the pulverization table, a chute for supplying a lump to the center of the pulverization table, and an inversion provided around the chute A frustoconical reject chute, and a swivel cone provided between the reject chute and the crushing table and having a conical cylinder portion extending above the inner wall of the housing and having a plurality of holes formed in the peripheral surface A vertical mill characterized in that the reject chute is connected to the conical cylinder portion so that the lower end of the reject chute is positioned at the lower end of the hole.   The vertical mill according to claim 1, wherein an integrated flow path having an arcuate bottom extending in the generatrix direction of the inner surface is formed on the inner surface of the reject chute, and the integrated flow path and the hole communicate with each other.   The vertical mill according to claim 2, wherein a recovery pipe extending toward the center of the crushing table is formed on an inner surface of the conical cylinder portion, and the recovery pipe and the accumulation channel communicate with each other.

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