JP2012217920A - Vertical mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vertical mill achieving the enhancement of classification efficiency by increasing the flow velocity of the primary air rising through a classification chamber while revolving to increase the centrifugal force acting on an object to be ground.SOLUTION: The vertical mill includes a housing 2, which is constituted of a cylindrical grinding part 3, a truncated cone-shaped speed increasing part 4 upwardly extending from the upper end of the grinding part to upwardly reduce in diameter and a rectification part 5 upwardly extending from the upper end of the cone-shaped speed increasing part 4, and which forms a classification chamber 12; a classifier 21 provided to the rectification part; a grinding table 7 provided to the lower part of the grinding part; and pressure rollers 9 pressed to the grinding table and grinding a lumpy substance, wherein primary air is ejected from the periphery of the grinding table so as to revolve in the classification chamber.

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 into pulverized coal, and the pulverized coal is supplied together with primary air to a burner that is a combustion apparatus.

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

  A lump of coal is fed from the chute to the center of the crushing table 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 rises while swirling by the primary air blown up from the primary air outlet around the pulverization table.

  In the process of raising the pulverized coal, centrifugal classification is performed on the pulverized coal by a centrifugal force of rotation, and gravity classification in which gravity by its own weight acts is performed. Among the pulverized coal, the centrifugal force and the gravity acting on the coarse pulverized coal having a large particle size are large, so that the pulverized coal is separated from the rising flow of the primary air and falls on the pulverization table.

  The pulverized coal after classification by centrifugal classification and gravity classification is subjected to collision classification by a classifier at the upper part of the housing, and further, the coarse pulverized coal is separated from the pulverized coal, so that the pulverized coal with a small particle size is primary air. And supplied to the burner.

  In the case of a conventional vertical mill, the swirling flow of the primary air gradually weakens as the housing moves up, so that the centrifugal classification effect cannot be fully exhibited.

  In addition, since the cross-sectional area inside the container surrounded by each side wall decreases from the lower part toward the upper part, a sufficient blowing flow rate can be obtained even if the amount of hot air flowing into the container is reduced. As a vertical roller mill that can perform the above, there is one disclosed in Patent Document 1.

JP 2000-93820 A

  In view of such circumstances, the present invention provides a vertical mill that improves the classification efficiency by increasing the flow velocity of primary air that rises while swirling the classification chamber and increasing the centrifugal force that acts on the pulverized product. To do.

  The present invention relates to a cylindrical pulverizing part, a truncated cone-shaped speed increasing part extending upward from the upper end of the pulverizing part, and a rectification extending upward from the upper end of the speed increasing part. And a classifier provided in the rectifying unit, a crushing table provided in a lower part of the crushing unit, and pressed by the crushing table to crush the lump. The present invention relates to a vertical roller that ejects primary air from the periphery of the pressure roller and the grinding table so as to swirl in the classification chamber.

  Further, according to the present invention, the rectifying unit has an inverted truncated cone shape that extends upward from the upper end of the speed increasing portion and expands upward, and is directed upward from the upper end of the inverted truncated cone portion. A cylindrical large cylindrical portion extending from the upper end of the large cylindrical portion; a truncated cone-shaped secondary speed increasing portion extending upward from the upper end of the large cylindrical portion; and an upper end of the secondary speed increasing portion The classifier includes a vertical mill provided on the small cylindrical portion. The small classifier includes a cylindrical small cylindrical portion extending upward.

  Further, the present invention relates to a vertical mill in which the large cylindrical portion further includes an auxiliary primary air supply port for jetting auxiliary primary air in a tangential direction from the peripheral surface to increase the swirling flow.

  Further, according to the present invention, the rectifying portion extends upward from the upper end of the speed increasing portion and has an inverted truncated conical shape with a diameter increasing upward, and is directed upward from the upper end of the inverted truncated conical portion. The classifier is related to a vertical mill provided in the cylindrical portion.

  Furthermore, the present invention relates to a vertical mill in which the rectifying portion has a cylindrical shape.

  According to the present invention, a cylindrical pulverizing part, a truncated cone-shaped speed increasing part extending upward from the upper end of the pulverizing part, and extending upward from the upper end of the speed increasing part. A rectifying unit configured to form a classification chamber, a classifier provided in the rectifying unit, a pulverizing table provided below the pulverizing unit, and pressed by the pulverizing table, A pressure roller for pulverization and a blow-out port for ejecting primary air from the periphery of the pulverization table so as to swirl in the classification chamber. The primary air flow rate increases with the diameter reduction of the part, and the centrifugal force acting on the crushed lump conveyed to the primary air increases. It can be separated from the upward flow of air more, improving the classification performance. Possible to exhibit an excellent effect that it is.

1 is a schematic sectional elevation view of a vertical mill according to a first embodiment of the present invention. It is a schematic sectional elevation view of a vertical mill according to a second embodiment of the present invention. It is a schematic sectional elevation of a vertical mill according to a third embodiment of the present invention. It is a schematic elevation sectional drawing of the vertical mill which concerns on the 4th Example of this invention.

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

  First, referring to FIG. 1, a first embodiment of the present invention will be described.

  In FIG. 1, 1 is a vertical mill, and the vertical mill 1 has a housing 2 erected on a base (not shown), and the housing 2 forms a sealed space inside. The housing 2 includes a cylindrical crushing portion 3, a frustoconical speed increasing portion 4 extending upward from the upper end of the crushing portion 3 and reducing in diameter upward, and an upper end of the speed increasing portion 4. It is comprised with the cylindrical rectification | straightening part 5 extended upwards.

  A table drive device (not shown) is provided below the housing 2, and a drive shaft 6 that passes through the housing 2 vertically from the lower portion to the lower portion of the crushing unit 3 is connected to the table drive device. . A crushing table 7 is provided at the upper end of the drive shaft 6, and the crushing table 7 is rotated at a constant speed or a variable speed by the table driving device via the drive shaft 6.

  A concave groove 8 is formed concentrically with the center of the pulverizing table 7 on the upper surface of the pulverizing table 7, and a required number of sets, for example, three sets of pressure rollers at intervals of 120 ° are formed radially from the rotation center of the pulverizing table 7. 9 is tiltably provided. The pressure roller 9 is pressed against the concave groove 8 by an actuator such as a hydraulic cylinder (not shown).

  A primary air chamber 11 is formed below the grinding table 7 in the housing 2, and a classification chamber 12 is located above the grinding table 7. The classification chamber 12 includes a crushing chamber 13 formed inside the crushing unit 3, a speed increasing chamber 14 formed inside the speed increasing unit 4, and a rectifying chamber formed inside the rectifying unit 5. It consists of 15. The speed increasing chamber 14 functions as a primary centrifugal classifying unit that performs primary centrifugal classification.

  A primary air supply port 16 is attached to the lower portion of the housing 2, and the primary air supply port 16 is connected to a blower (not shown) and communicates with the primary air chamber 11. Around the pulverizing table 7, primary air outlets 17 inclined in the circumferential direction are provided on the entire circumference.

  A raw material supply / discharge portion (not shown) is provided above the housing 2, and the raw material supply / discharge portion has a pipe-like chute 18. The chute 18 extends to the crushing chamber 13 inside the housing 2, and the lower end is positioned above the center of the crushing table 7. Bulk coal is supplied to the chute 18, and the supplied coal falls to the center of the crushing table 7.

  The rectifying chamber 15 is provided with a classifier 21 having a blade 19 so as to be rotatable with respect to the chute 18. The classifier 21 is rotated by a classifier driving device (not shown). The blades 19 are in the shape of strips, and a predetermined number, for example, 20 to 60, is disposed on the inverted conical curved surface at a predetermined angular pitch in the circumferential direction. The blade 19 is inclined from the lower end toward the upper end so as to be separated from the center of the rectifying chamber 15.

  A pulverized coal feed pipe 22 for feeding the pulverized pulverized coal is connected to the raw material supply / discharge section, and the pulverized coal feed pipe 22 is connected to a burner (not shown) of a boiler. .

  Next, the pulverization of coal in the vertical mill 1 will be described.

  The crushing table 7 is rotated by a table driving device (not shown) via the drive shaft 6, and primary air at around 200 ° C. is introduced into the primary air chamber 11 from the primary air supply port 16. In this state, lump 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 7 and is supplied onto the crushing table 7.

  The coal on the crushing table 7 is moved in the outer peripheral direction by the centrifugal force generated by the rotation of the crushing table 7, and is caught by the pressure roller 9 and consists of coarse coal with a large particle size and pulverized coal with a small particle size. It is pulverized into pulverized charcoal and further moved to the outer periphery by centrifugal force.

  The primary air introduced into the primary air chamber 11 from the primary air supply port 16 blows up from the outlet 17 of the pulverizing table 7, and the pulverized coal that has climbed over the concave groove 8 by centrifugal force is: It rides on the primary air blown up from the outlet 17, and rises as a pulverized coal flow 23 while turning the outer peripheral portion of the classification chamber 12 along the inner wall surface of the pulverization unit 3.

  Note that the swirl flow velocity of the pulverized coal flow 23 is inversely proportional to the square of the diameter of the swirl flow. The centrifugal force is proportional to the square of the swirl flow velocity (inversely proportional to the fourth power of the diameter), and inversely proportional to the first power of the rotational radius (diameter) of the swirl flow. Accordingly, the centrifugal force acting on the pulverized coal flow 23 is inversely proportional to the fifth power of the diameter of the swirling flow. On the other hand, the drag force caused by the swirling flow and the upward flow is proportional to the square of the flow velocity (inversely proportional to the fourth power of the diameter).

  In the course of ascending the outer periphery of the pulverizing chamber 13, the pulverized coal flow 23 is subjected to centrifugal classification due to the swirling of the primary air, and centrifugal classification is performed. Done. At this time, since a large centrifugal force and gravity act on the coarse pulverized coal having a large particle size, only the coarse pulverized coal is separated in the radial direction from the pulverized coal flow 23 and is blown to the inner wall of the pulverized portion 3, and the direction of gravity And fall on the crushing table 7.

  The pulverized coal flow 23 rising in the pulverizing chamber 13 then moves upward while turning around the speed increasing chamber 14 whose diameter is reduced upward.

  As described above, the flow velocity of the pulverized coal flow 23 is inversely proportional to the square of the diameter of the swirling flow, and the centrifugal force acting on the pulverized coal flow 23 is inversely proportional to the fifth power of the diameter of the swirling flow. As the speed increasing chamber 14 is raised and the diameter of the speed increasing chamber 14 is reduced, the rotational radius of the swirling flow of the pulverized coal flow 23 decreases, the flow velocity increases, The centrifugal force acting on the pulverized coal becomes larger. In addition, since the rotational radius of the swirl flow gradually decreases, an increase in swirl flow pressure loss when the diameter is reduced can be suppressed.

  Accordingly, in the speed increasing chamber 14, the effect of centrifugal classification on the pulverized coal flow 23 is increased. Therefore, the coarse pulverized coal that could not be separated in the pulverization chamber 13 by centrifugal classification and gravity classification is crushed by the centrifugal force. 23 can be separated in the radial direction.

  Further, since the speed increasing chamber 14 has a truncated cone shape, the pulverized coal separated from the pulverized coal flow 23 and colliding with the inner wall of the speed increasing chamber 14 receives a reaction force in the downward direction and is easily Fall down.

  The pulverized coal flow 23 that has moved up the speed increasing chamber 14 then moves up the rectifying chamber 15. In the rectifying chamber 15, the pulverized coal stream 23 swirling while being reduced in diameter is rectified again into a swirling flow whose ascending direction is vertical along the inner wall of the rectifying unit 5. It flows into the classifier 21 and collision classification is performed.

  When the pulverized coal flow 23 flowing into the classifier 21 crosses the blade 19, coarse coal having a predetermined particle size or more is repelled by the blade 19 and falls onto the pulverization table 7. The pulverized coal having a predetermined particle size or less that has passed through the blade 19 is fed from the pulverized coal feed pipe 22 and supplied to a burner of a boiler (not shown).

  Coarse coal that has been classified by gravity classification, centrifugal classification, and collision classification and dropped onto the pulverizing table 7 moves to the concave groove 8 by the rotational centrifugal force of the pulverizing table 7 and is pulverized again by the pressure roller 9. In the process of ascending the classification chamber 12 and flowing into the classifier 21, classification is performed again by gravity classification, centrifugal classification, and collision classification.

  As described above, in the first embodiment, the speed increasing portion 4 having a truncated cone shape with a diameter decreasing upward is provided in the housing 2, and the swirling speed of the pulverized coal flow 23 rising in the classification chamber 12. Since the centrifugal force acting on the pulverized coal flow 23 is increased, the effect of centrifugal classification is increased, and the classification performance in the vertical mill 1 can be improved.

  In addition, since the cylindrical rectifying unit 5 extending from the upper end of the speed increasing unit 4 is provided and rectified so that the pulverized coal flow 23 rises in the vertical direction while turning along the inner wall of the rectifying unit 5, The pulverized coal stream 23 can be prevented from concentrating and flowing into a part of the classifier 21 while being reduced in diameter, and the flow distribution of the pulverized coal stream 23 flowing into the classifier 21 is made uniform and classified. Performance can be improved.

  Furthermore, in the first embodiment, since the classifier 21 is provided in the rectifying unit 5 having a diameter smaller than that of the pulverizing unit 3, the classifier 21 can be miniaturized and the cost can be reduced. it can.

  Next, referring to FIG. 2, a second embodiment of the present invention will be described. 2 that are the same as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  In the second embodiment, the housing 2 is constituted by a pulverizing part 3, a speed increasing part 4, and a rectifying part 24. The rectifying unit 24 extends upward from the upper end of the speed increasing unit 4 and extends upward from the upper end of the inverted frustoconical portion 25. A rectifying chamber 27 is formed inside the rectifying unit 24.

  The classifier 21 is housed concentrically in the upper part of the rectifying chamber 27, that is, in the cylindrical part 26.

  The pulverized coal introduced from the chute 18 and pulverized by the pressure roller 9 is blown up to the primary air and ascends as the pulverized coal flow 23 turns around the outer periphery of the classification chamber 12.

  The pulverized coal flow 23 whose speed has been increased in the process of ascending the speed increasing chamber 14 then moves up the rectifying chamber 27. As the diameter of the swirling flow increases along the inner wall of the inverted truncated cone portion 25, the flow velocity of the pulverized coal flow 23 rising in the rectifying chamber 27 decreases.

  The pulverized coal flow 23 becomes a stable flow as the flow velocity decreases, and is further rectified so as to rise vertically while swirling along the inner wall of the cylindrical portion 26. Since the ascending direction is rectified into a vertical swirling flow, the pulverized coal flow 23 can be prevented from concentrating and flowing into a part of the classifier 21, so that the pulverization flowing into the classifier 21 can be prevented. The flow distribution of the coal flow 23 can be made uniform, and the classification performance can be improved.

  Further, since the pulverized coal stream 23 is rectified so as to rise vertically while swirling, the pulverized coal stream 23 easily flows into the classifier 21 from the direction orthogonal to the blade 19, and the performance of the classifier 21 is improved. Can be stabilized.

  Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the third embodiment, the housing 2 is constituted by the pulverizing part 3, the speed increasing part 4, and the rectifying part 28. The straightening portion 28 extends upward from the upper end of the speed increasing portion 4 and extends upward from the upper end of the inverted truncated cone portion 29, and an inverted truncated cone portion 29 having an inverted truncated cone shape that expands in diameter upward. From a cylindrical large cylindrical portion 31, a frustoconical secondary speed increasing portion 32 that extends upward from the upper end of the large cylindrical portion 31 and contracts in diameter upward, and from the upper end of the secondary speed increasing portion 32 A rectifying chamber 34 is formed inside the rectifying unit 28, which is constituted by a small cylindrical portion 33 having a cylindrical shape extending upward. The rectifying chamber 34 also functions as a secondary centrifugal classifying unit that performs secondary centrifugal classification by the secondary speed increasing unit 32.

  The classifier 21 is housed concentrically in the upper portion of the rectifying chamber 34, that is, in the small cylindrical portion 33.

  The pulverized coal introduced from the chute 18 and pulverized by the pressure roller 9 is blown up to the primary air and ascends as the pulverized coal flow 23 turns around the outer periphery of the classification chamber 12.

  The pulverized coal flow 23 whose speed has been increased in the process of moving up the speed increasing chamber 14 then moves up the rectifying chamber 34. As the diameter of the swirling flow increases along the inner wall of the inverted truncated cone portion 29, the flow velocity of the pulverized coal flow 23 decreases.

  Thereafter, the pulverized coal flow 23 is rectified so as to rise vertically while turning along the inner wall of the large cylindrical portion 31, and then the diameter of the swirling flow is reduced again along the inner wall of the secondary speed increasing portion 32. As a result, the flow rate of the pulverized coal flow 23 increases.

  By increasing the flow rate of the pulverized coal flow 23 again, the centrifugal force acting on the pulverized coal in the pulverized coal flow 23 is increased, and centrifugal classification is performed again, and the pulverized coal stream 23 and the speed increasing chamber 14 are separated. Coarse coal that could not be produced can be separated from the pulverized coal flow 23 in the radial direction by centrifugal force.

  Coarse coal separated from the pulverized coal flow 23 receives a force downward from the inner wall of the secondary speed increasing portion 32 and falls down, slides down along the inner wall of the inverted truncated cone portion 29, and is placed on the pulverizing table 7. Fall.

  Further, the pulverized coal flow 23 whose flow velocity has been increased by being reduced in diameter along the inner wall of the secondary speed increasing portion 32 is again turned into a swirling flow whose ascending direction is vertical along the inner wall of the small cylindrical portion 33. The rectified and rectified pulverized coal stream 23 flows into the classifier 21.

  At this time, it is desirable to increase the rotational speed of the classifier 21 in accordance with the increase in the flow rate of the pulverized coal flow 23 by the secondary speed increasing unit 32.

  Since the pulverized coal flow 23 is rectified into a swirl flow whose vertical direction is vertical, the flow distribution of the pulverized coal flow 23 flowing into the classifier 21 becomes uniform, and the classification performance can be improved.

  In addition, since the centrifugal force acting on the pulverized coal flow 23 is increased by the secondary speed increasing portion 32 and the centrifugal classification is performed again, the coarse that could not be separated in the pulverizing chamber 13 and the speed increasing chamber 14 could be obtained. The pulverized coal can be separated from the pulverized coal flow 23 in the radial direction by centrifugal force, and the classification performance in the vertical mill 1 can be improved.

  Further, since the speed of the pulverized coal flow 23 is increased again in the rectifying chamber 34, the amount of pulverized coal classified by the classifier 21 and fed to a burner (not shown) can be increased. it can. Therefore, it is possible to suppress the pulverized coal from staying in the rectifying chamber 34 due to the difference in the rising speed of the pulverized coal flow 23 in the speed increasing chamber 14 and the rectifying chamber 34, thereby preventing the mill differential pressure from rising. At the same time, the grinding capacity can be increased.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. 4 that are the same as those in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

  In the fourth embodiment, an auxiliary primary air supply port 35 connected to a blower (not shown) and communicating from the rectifying chamber 34 in the tangential direction is provided in the large cylindrical portion 31 of the rectifying portion 28 in the third embodiment. ing.

  The auxiliary primary air supply port 35 is provided so as to be inclined downward and circumferentially with respect to the outer wall of the large cylindrical portion 31 so as to form a swirling flow in which the supplied auxiliary primary air swirls upward. It has been. The inclination angle of the auxiliary primary air supply port 35 (the angle with respect to the horizontal) can accelerate the flow rate of the pulverized coal flow 23 that rises while the supplied auxiliary primary air swirls in the rectifying chamber 34. An angle is desirable.

  At the time of the coal pulverization process, the auxiliary primary air is supplied from the auxiliary primary air supply port 35 to the pulverized coal flow 23 that rises while swirling in the rectifying chamber 34, whereby the flow velocity of the pulverized coal flow 23 is increased. Can be increased. Therefore, the effect of centrifugal classification performed again in the secondary speed increasing unit 32 can be further increased, and the classification performance can be improved.

  At this time, the rotational speed of the classifier 21 is increased in accordance with the flow speed of the rising pulverized coal flow 23.

  Since the flow rate of the pulverized coal flow 23 can be increased by the auxiliary primary air, the amount of pulverized coal fed to a boiler burner (not shown) can be further increased than in the third embodiment. It is possible to further suppress an increase in the mill differential pressure due to a difference in the rising speed of the pulverized coal flow 23 between the speed increasing chamber 14 and the rectifying chamber 34, and further increase the pulverization capacity.

  In the present invention, the pulverization of coal has been described, but it is needless to say that the vertical mill of the present invention can also be applied to the pulverization of other massive materials such as limestone.

DESCRIPTION OF SYMBOLS 1 Vertical mill 2 Housing 3 Crushing part 4 Speed increasing part 5 Rectification part 7 Crushing table 9 Pressure roller 17 Outlet 21 Classifier 23 Crushing coal flow 24 Rectification part 25 Inverted truncated cone part 26 Cylindrical part 27 Rectification room 28 Rectification part 29 Inverted truncated cone part 31 Large cylindrical part 32 Secondary acceleration part 33 Small cylindrical part 34 Rectification room 35 Auxiliary primary air supply port

Claims (5)

  Consists of a cylindrical pulverizing part, a truncated cone-shaped speed increasing part extending upward from the upper end of the pulverizing part and reducing the diameter upward, and a rectifying part extending upward from the upper end of the speed increasing part A classification chamber, a classifier provided in the rectifying unit, a pulverizing table provided in a lower portion of the pulverizing unit, and a pressure roller that is pressed by the pulverizing table and pulverizes the lump. A vertical mill that ejects primary air from the periphery of the crushing table so as to swivel in the classification chamber.   The straightening portion includes an inverted truncated cone portion extending upward from the upper end of the speed increasing portion and expanding upward, and a cylinder extending upward from the upper end of the inverted truncated cone portion. A large cylindrical portion having a shape, a truncated cone-shaped secondary speed increasing portion extending upward from the upper end of the large cylindrical portion, and extending upward from the upper end of the secondary speed increasing portion. The vertical mill according to claim 1, further comprising a cylindrical small cylindrical portion that comes out, wherein the classifier is provided in the small cylindrical portion.   3. The vertical mill according to claim 2, wherein the large cylindrical portion further includes an auxiliary primary air supply port that ejects auxiliary primary air in a tangential direction from a peripheral surface to increase a swirl flow.   The straightening portion includes an inverted truncated cone portion extending upward from the upper end of the speed increasing portion and expanding upward, and a cylinder extending upward from the upper end of the inverted truncated cone portion. The vertical mill according to claim 1, further comprising a cylindrical portion having a shape, wherein the classifier is provided in the cylindrical portion.   The vertical mill according to claim 1, wherein the rectifying unit has a cylindrical shape.

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