JP5625473B2 - Vertical roller mill - Google Patents

Description

  The present invention relates to a vertical roller mill for finely pulverizing a lump, and more particularly to a vertical roller mill equipped with a cyclone classifier capable of varying classification performance.

  A vertical roller mill rolls a roller on a rotating crushing table, crushes a lump of coal or the like supplied to the crushing table with a roller, and crushes it into a fine powder. The fine powder is classified into fine powder having a particle size or less, and the fine powder is sent out from the vertical roller mill together with air as a carrier medium.

  One of the classifiers provided in the vertical roller mill is a cyclone classifier.

  The cyclonic classifier defines a classification chamber inside a vertical roller mill, and turns the mixed flow of powder and carrier air (hereinafter referred to as a mixed flow) flowing into the classification chamber into a swirling flow. A centrifugal force of swirling is applied to the powder, and those having a large particle size are blown to the outer peripheral side, and only fine particles having a small particle size are sent out from the center of the classification chamber together with the carrier air. Therefore, in the cyclone classifier, the classification performance varies depending on the strength of the swirling flow, and the particle size of the fine powder to be sent out is adjusted by changing the strength of the swirling flow.

  The conventional vertical roller mill cyclone type classifier has variable blades that swirl the mixed flow at the part where the mixed flow flows into the classification chamber, and mixing that flows into the classification chamber by adjusting the angle of the variable blades The flow inflow angle was adjusted to adjust the strength of the swirl flow.

  Here, the variable blades are rotatably provided at a predetermined angular pitch in the circumferential direction and are connected by a link mechanism so that all the variable blades rotate integrally through the link mechanism.

  For this reason, there are many connecting parts, the structure is complicated, and it is difficult to obtain accuracy due to the backlash of the connecting part. When the rotation direction is changed and the angle of the variable blade is adjusted, hysteresis occurs due to the backlash of the connecting part. However, the angle of the variable blade cannot be set accurately. In addition, the error tends to increase over time due to wear and the like, and there are problems such as requiring maintenance.

JP-A-10-28890 JP 2007-61684 A

  In view of such circumstances, the present invention makes it possible to change the classifying performance of the cyclonic classifier included in the vertical roller mill with a simple configuration, and the mechanism for changing the classifying performance does not include an increase in error over time. A vertical roller mill is provided.

  The present invention provides a vertical roller mill having a cyclone classifier as a classifier, wherein the cyclone classifier has an opening through which a mixed flow of crushed powder and carrier air flows in an upper peripheral surface, and an upper center A classifier outlet tube, and fixed swirl vanes provided at predetermined intervals in the opening, the classifier outlet tube being concentric with the fixed swivel center tube and the fixed swivel center tube. It comprises at least one movable swivel center tube that can be moved up and down with respect to the tube, and is configured such that the axial center length of the classifier outlet tube is changed by raising and lowering the movable swivel center tube, The mixed flow that flows into the classifier is swirled by the fixed swirler, and the mixed flow that flows in swirls around the classifier outlet tube and flows out through the classifier outlet tube. This relates to a vertical roller mill.

  The present invention also relates to a vertical roller mill provided with an elevating mechanism for elevating and lowering the movable turning center tube.

  According to the present invention, in a vertical roller mill equipped with a cyclonic classifier as a classifier, the cyclonic classifier has an opening into which a mixed flow of crushed powder and carrier air flows into the upper peripheral surface, A classifier outlet cylinder is provided at the center of the upper part, and fixed swirl vanes are provided at predetermined intervals in the opening. It comprises at least one movable turning center tube that can be raised and lowered with respect to the turning center tube, and is configured such that the axial center length of the classifier outlet tube is changed by raising and lowering the movable turning center tube, The mixed flow that flows into the classifier is swirled by the fixed swirl blade, and the mixed flow that flows in swirls around the classifier outlet tube and flows out through the classifier outlet tube. Because it is configured, the axis of the classifier outlet tube Is changed, the swirling time of the mixed flow is changed, the centrifugal force acting on the powder of the mixed flow is changed, and the classification performance can be adjusted. The tube only moves in the axial direction with respect to the fixed turning center tube, and the backlash between the fixed turning center tube and the movable turning center tube affects the axial center length of the classifier outlet tube. There is no influence on the axial center length of the classifier outlet cylinder even if the backlash increases with time, and the positioning accuracy between the fixed turning center cylinder and the movable turning center cylinder is not changed over time. There is no deterioration.

  Further, according to the present invention, an elevating mechanism for raising and lowering the movable turning center tube is provided, so that the axial center length of the classifier outlet tube can be changed at any time, and the classification performance can be changed at any time. The excellent effect of being.

It is a schematic sectional drawing which shows the vertical roller mill which concerns on the Example of this invention. It is an AA arrow line view of FIG. It is sectional drawing which shows the classifier of a present Example, (A) shows the case where classification performance is made low, (B) shows the case where classification performance is made high.

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

  FIG. 1 shows an example of a vertical roller mill in which the present invention is implemented, and an outline of the vertical roller mill 1 will be described with reference to FIG. The lump to be crushed is coal.

  A sealed space 3 is formed by the housing 2, and a pulverizing table 5 is erected at a lower portion of the space 3 via a table driving device 4, and the pulverizing table 5 is rotated at a constant speed by the table driving device 4. . On the upper surface of the pulverizing table 5, a table segment 7 having a concave groove 6 having a circular cross section is provided.

  A required number of sets, for example, three sets of pressure roller units 8 are provided radially from the rotation center of the crushing table 5. The pressure roller unit 8 has a pressure roller 9 and is tiltable about a horizontal support shaft 11. In addition, three sets of roller pressurizing devices 12 penetrating radially are provided at the lower portion of the housing 2. The roller pressure device 12 includes an actuator, for example, a hydraulic cylinder, and presses the pressure roller 9 against the concave groove 6.

  A primary air chamber 13 is formed below the pulverizing table 5, and a primary classification chamber 14 is provided above the pulverizing table 5 inside the housing 2.

  A primary air supply port 15 is attached to the lower part of the housing 2, and the primary air supply port 15 communicates with the primary air chamber 13. A gap is formed around the crushing table 5, and the gap serves as a primary air outlet 16.

  A coal supply / discharge portion 17 is provided on the upper side of the housing 2, and a pipe-like chute 18 is provided so as to penetrate the center portion of the coal supply / discharge portion 17. It extends to. The chute 18 is supplied with coal, and the supplied coal falls on the crushing table 5.

  A classifier 19 is rotatably provided in the middle of the chute 18. The classifier 19 has a hollow inverted frustoconical classifying cylinder 21, the classifying cylinder 21 defines a secondary classifying chamber 20 inside, the classifying cylinder 21 has an open lower end, and the chute 18 A coal supply dropping port 22 is formed between the two. The secondary classification chamber 20 and the primary classification chamber 14 communicate with each other through the coal supply dropping port 22.

  An introduction portion 23 is provided at the upper end portion of the classification tube 21, and the peripheral surface of the introduction portion 23 is opened to serve as a mixed flow inlet. Fixed swirl vanes 24 are provided at the mixed flow inlet at a predetermined pitch in the circumferential direction, for example, a pitch of 22.5 °, and at a tilt angle of a predetermined angle with respect to the tangent of the circumference (see FIG. 2). . The inclination angle is set based on results, experiments, calculations, and the like.

  A fixed turning center tube 25 concentric with the classifying tube 21 is suspended downward from the center of the upper end surface of the classifying tube 21, and the fixed turning center tube 25 faces the introduction portion 23. The axial center length of the fixed turning center tube 25 is equal to or substantially the same as the vertical length of the fixed turning blade 24.

  The coal supply / discharge unit 17 includes a distributor 26, and the distributor 26 is provided above the classifier 19. The distributor 26 is concentric with the classifier 19 and has a substantially inverted truncated cone shape. The lower end is open and communicates with the fixed turning center tube 25. Moreover, the coal feeding pipe 27 corresponding to the number of coal burners (not shown) is connected to the upper end surface, and the coal feeding pipe 27 is connected to each coal burner. The connection end of the coal feeding pipe 27 opens into the distributor 26, and the opening of the coal feeding pipe 27 can be closed by a cut damper 28.

  As shown in FIG. 3, a movable turning center tube 29 is fitted inside the fixed turning center tube 25, and the movable turning center tube 29 can be slid along the axis with respect to the fixed turning center tube 25. And The fixed turning center tube 25 and the movable turning center tube 29 form a classifier outlet tube 30 through which the mixed flow 37 classified by the classifier 19 flows out.

  A rack 31 is provided at the upper end of the movable turning center tube 29, and the rack 31 extends upward and is parallel to the axis of the movable turning center tube 29. A rotation adjustment motor 32 is provided on the upper surface of the classifying cylinder 21, and a drive shaft 33 of the rotation adjustment motor 32 penetrates the distributor 26 in the horizontal direction, and a pinion gear is provided at the tip of the drive shaft 33. 34 is provided, and the pinion gear 34 meshes with the rack 31. In addition, a shaft seal 35 is provided in the portion of the drive shaft 33 that penetrates the distributor 26.

  The rack 31, the turning adjustment motor 32, the pinion gear 34 and the like constitute a movable turning center cylinder lifting mechanism, and the fixed turning center cylinder 25, the movable turning center cylinder 29, the rack 31, and the turning adjustment. The motor 32, the pinion gear 34, and the like constitute swirl flow adjusting means. Instead of the rack 31, the turning adjustment motor 32, and the pinion gear 34, the movable turning center tube 29 may be moved up and down by a cylinder.

  Hereinafter, the operation of the present embodiment will be described with reference to FIG. 1 and FIG. FIG. 3A shows a state in which the classifying performance is low, that is, fine powder to be sent out, in a state where the movable turning center tube 29 is raised, that is, in a state where the axial center length of the classifier outlet tube 30 is shortened. The case where the minimum particle size of is large is shown.

  The crushing table 5 is rotated at a constant speed at a predetermined speed, and in the state where primary air is introduced from the primary air supply port 15, massive coal is introduced from the chute 18. The lump coal flows down from the lower end of the chute 18 to the center of the crushing table 5 and is supplied onto the crushing table 5.

  The coal on the pulverizing table 5 moves in the outer circumferential direction by centrifugal force, is pulverized by being pressed by the pressure roller 9, and further overflows from the table segment 7 to the outer periphery due to centrifugal force. Rides on the primary air that blows up the outlet 16 and rises as a mixed flow 37 of pulverized coal and primary air.

  The mixed flow 37 that has risen through the primary classification chamber 14 passes through the introduction portion 23 and flows into the secondary classification chamber 20, but in the process of passing through the introduction portion 23, the mixed flow 37 is swirled by the fixed swirl blade 24. Given. The mixed flow 37 that has become a swirl flow swirls around the fixed swirl center tube 25. As the mixed flow 37 swirls in the secondary classification chamber 20, pulverized coal having a large particle size is blown to the outer periphery by centrifugal force, flows down along the inner surface of the classification cylinder 21, and the coal supply dropping port. 22 falls onto the crushing table 5. Further, the pulverized coal having a small particle diameter is introduced together with the primary air into the distributor 26 through the lower ends of the fixed turning center tube 25 and the movable turning center tube 29, and is sent out from the coal feeding pipe 27. .

  Accordingly, the mixed flow 37 flows into the secondary classification chamber 20 through the introduction portion 23 and is classified by the swirling flow.

  FIG. 3B shows a state in which the classifying performance is high in the state where the movable turning center tube 29 is lowered, that is, the axial center length of the classifier outlet tube 30 is long, that is, the minimum amount of fine powder to be delivered. The case where the particle size is small is shown.

  In the state shown in FIG. 3B, when the mixed flow 37 flows into the secondary classification chamber 20 through the introduction portion 23 and swirl is given, the movable swivel center tube 29 is lowered. The mixed flow 37 swirls around the fixed swivel center tube 25 and the movable swivel center tube 29.

  That is, as the movable swivel center tube 29 descends, the swirl center of the mixed flow 37 becomes longer in the vertical direction, and the mixed flow 37 swirls more than the state in which the movable swivel center tube 29 is raised. It will be.

  When the mixed flow 37 is swirled in the secondary classification chamber 20 for a long time and the swirling length is long, the time for which centrifugal force acts on the pulverized coal contained in the mixed flow 37 becomes long, and the particle size is small. Powdered coal is also blown to the outer periphery. Therefore, the particle size of the pulverized coal contained in the mixed flow 37 that rises around the lower end of the movable swivel center tube 29 becomes small.

  Thus, by moving the movable swivel center tube 29 up and down, the swirling time and swirling length of the mixed flow 37 in the secondary classification chamber 20 change, and the classification performance changes. That is, by moving the movable turning center tube 29 up and down, the classification performance is adjusted, and it becomes possible to send the pulverized coal in accordance with the particle size of the pulverized coal required by the burner.

  Further, according to the present embodiment, the movable turning center tube 29 is lifted and lowered with the fixed turning center tube 25 as a guide, so that no error occurs over time with respect to the lifting movement, and the movable turning center tube In the rack and pinion that is a drive mechanism for moving the elevator 29 up and down, the weight of the movable swivel center tube 29 acts, so the load direction is constant, and the backlash in the rack and pinion has little influence on the positioning accuracy. Therefore, in this embodiment, the positioning accuracy does not deteriorate with time, and the need for maintenance is almost eliminated.

  The classifier outlet cylinder 30 is a double cylinder of the fixed turning center cylinder 25 and the movable turning center cylinder 29, but it goes without saying that it may be a triple cylinder or a quadruple cylinder.

  The movable turning center tube 29 is slidably fitted into the fixed turning center tube 25, but may be slidably fitted to the fixed turning center tube 25.

  Further, the rack 31, the turning adjustment motor 32, and the pinion gear 34 may be omitted, and the movable turning center tube 29 may be fixed at a required position of the fixed turning center tube 25 by a fixing tool such as a bolt. .

DESCRIPTION OF SYMBOLS 1 Vertical roller mill 2 Housing 3 Space 5 Grinding table 8 Pressure roller unit 14 Primary classification chamber 19 Classifier 20 Secondary classification chamber 21 Classification cylinder 22 Classification coal supply drop port 23 Introduction part 24 Fixed turning blade 25 Fixed turning center cylinder 26 Distributor 29 Movable swivel center tube 30 Classifier outlet tube 31 Rack 32 Turning adjustment motor 33 Drive shaft 34 Pinion gear 37 Mixed flow

Claims (2)

In a vertical roller mill equipped with a cyclone classifier as a classifier, the cyclone classifier has an opening through which a mixed flow of pulverized powder and carrier air flows in the upper peripheral surface, and the classifier outlet in the upper center. A fixed swirl vane provided at a predetermined interval in the opening and facing the classifier outlet tube, and the classifier outlet tube is equal to or substantially equal to the vertical length of the fixed swirl vane A fixed turning center tube and at least one movable turning center tube that is concentric with the fixed turning center tube and can be moved up and down with respect to the fixed turning center tube. The mixed flow that flows into the classifier through the fixed swirler is swirled by the fixed swirler, and the mixed flow that flows into the classifier outlet tube 該分classifier outlet tube to pivot the circumferential Included a lower end times, is configured such that flowing through the該分classifier outlet tube, the pivot center of said mixed flow by the movable pivot cylinder drops becomes longer in the vertical direction, the turning time and the turning length increases A vertical roller mill characterized by the configuration .   The vertical roller mill according to claim 1, further comprising an elevating mechanism for elevating and lowering the movable turning center tube.

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