JP2011098316A - Vertical roller mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical roller mill of which the classifier is improved in the classification capacity and classification precision and which can be miniaturized in size. <P>SOLUTION: The vertical roller mill is so constituted that a crushing table 8 is installed at the lower part of a classifying chamber 12, that a classifier 25 positioned at the upper part of the classifying chamber and arranged so that crashed powders pass as an air mixed flow, and a turning giving means 32 giving a turning flow to the ascending air-mixed flow are included, that the classifier having blades 26 of a required number of sheets rotating on the perpendicular axis is inclined to make the upper end pull away from the perpendicular axis, and that the turning giving means gives turning force so that the centrifugal force by the classifier and the flow drag by the gas flow may be balanced over the total length of the blades. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vertical roller mill that pulverizes massive coal, limestone, etc., and supplies it as a fine powder and as a fuel for boilers or as a raw material for cement.

  In a coal-fired boiler using coal as fuel, massive coal is pulverized by a vertical roller mill into pulverized coal having a predetermined particle size, and the pulverized coal is supplied together with primary air to a burner that is a combustion apparatus.

  The vertical roller mill supplies massive coal on a grinding table, grinds massive coal with a roller that rolls on the grinding table, and the pulverized pulverized coal is conveyed by primary air, but is supplied to the burner. The pulverized coal is classified by a classifier provided inside the vertical roller mill so that the pulverized coal has a predetermined diameter.

  FIG. 7 is a schematic view of a conventional classifier 1. In the figure, 2 is a chute that causes massive coal to flow down to the center of the crushing table, and a rotation installed around the chute 2 in a double cylindrical shape. The shaft 28 is rotated by a required driving device. A strip-like blade 4 is supported on the rotary shaft 28 via a blade support 3, and the blade 4 is provided so as to be inclined so that the upper end is separated from the center, and at a predetermined interval in the circumferential direction. It is arranged by.

  The pulverized coal is classified by passing through the classifier 1 rotating on primary air, and only those having a predetermined particle size or less pass through the classifier 1 and are supplied to the pulverized coal burner. It is supposed to be done.

  As a principle of classifying the particles, by rotating the blade 4, the pulverized coal follows the rotation of the blade 4 so that the pulverized coal is swirled, and centrifugal force acts on the pulverized coal by the swirling. Since the centrifugal force increases in proportion to the mass, the larger the particle, the larger the centrifugal force acts.

  On the other hand, the primary air passes through the blade 4 and flows in toward the center of the classifier 1 and further rises. Therefore, the centrifugal force and the force pushed back by the primary air flow (hereinafter referred to as fluid drag) act on the pulverized coal in opposition.

  For this reason, those having a small particle size and a fluid drag larger than the centrifugal force are carried on the primary air, and those having a large particle size and a centrifugal force larger than the fluid drag are pushed back and dropped.

  The small particle size moves with the air flow to avoid the blade 4 with respect to the rotation of the blade 4, but the large particle size collides with the blade 4 and falls downward.

  Classification is performed by the rotation of the blade 4 and the behavior of the pulverized coal with respect to the rotation.

  Next, the centrifugal force acting on the pulverized coal becomes larger when the turning radius is larger, and when the blade 4 is mounted, the lower end radius and the upper end radius are increased, and the upper end radius is increased. As the centrifugal force of the classifier 1 increases, a difference in classification ability occurs between the upper part and the lower part of the classifier 1, and the particle size after classification varies.

  For this reason, conventionally, the blade 4 is provided in parallel to the rotating shaft 28, or measures such as reducing the inclination angle are taken to equalize the centrifugal force.

  On the other hand, when the blade 4 is provided parallel to the rotary shaft 28 or the inclination angle is reduced, the flow of primary air rises vertically, deflects horizontally and flows into the blade 4, The flow is deflected in the vertical direction and flows out, and the flow direction is greatly changed. For this reason, a pressure loss becomes large and the loss of ventilation power also becomes large. Further, the flow of air flows more in the lower part of the blade 4 due to the deflection in the flow direction, and the air mixed flow passing through the blade 4 is biased, so that the classifier 1 is partially used. The classifying ability of the classifier 1 was lowered.

  Further, if the blade 4 is provided on the rotating shaft 28 or provided with a small inclination angle, the height of the classifier 1 becomes large, which makes it difficult to reduce the size of the vertical roller mill. .

JP-A-11-57515 JP-A-4-349944 JP-A-11-207202

  In view of such circumstances, the present invention provides a vertical roller mill that improves the classification ability and classification accuracy of the classifier in the vertical roller mill and enables downsizing.

  The present invention provides a classifier provided with a pulverization table at the lower part of the classification chamber, and positioned so as to pass the pulverized powder as an air mixed flow, and an ascending air mixed flow. The classifier has a required number of blades rotating about a vertical axis, and the blades are inclined so that their upper ends are separated from the vertical axis. The swivel imparting means relates to a saddle type roller mill configured to impart a swirl force so that a centrifugal force by the classifier and a fluid drag force by a gas flow are balanced over the entire length of the blade.

  Further, the present invention relates to a vertical roller mill in which an air jet port inclined at least in the circumferential direction is provided around the pulverization table, and a swirl flow is applied in the process of ejecting primary air from the air jet port. It is.

  Further, according to the present invention, there is provided a vertical roller mill in which rectifying plates that are inclined with respect to a generatrix of the inner wall surface are provided on the inner wall surface of the classification chamber at predetermined intervals in the circumferential direction, and that imparts a swirl flow to the rising air mixed flow. It is concerned.

  Further, according to the present invention, an auxiliary air jet nozzle is provided at a required interval on the inner wall surface of the classification chamber, and auxiliary air is jetted in a tangential direction from the auxiliary air jet nozzle so as to impart a swirl flow to the rising air mixed flow. This relates to a die roller mill.

  According to the present invention, a pulverizing table is provided in the lower part of the classification chamber, the classifier is located at the upper part of the classification chamber and arranged to pass the pulverized powder as an air mixed flow, and the rising air Swirl imparting means for imparting a swirl flow to the mixed flow, and the classifier has a required number of blades that rotate about a vertical axis, and the blades have their upper ends separated from the vertical axis. The swirl imparting means is configured to impart a swirl force so that the centrifugal force by the classifier and the fluid drag force by the gas flow are balanced over the entire length of the blade. The classifying function can be effectively exhibited, the classifying ability can be improved, and the blade is inclined in a direction close to the horizontal, so that the height of the blade of the classifier is reduced, and the vertical roller mill Downsizing There is exhibited an excellent effect that can be achieved.

It is a schematic sectional drawing of the vertical roller mill in which this invention is implemented. It is explanatory drawing which shows the 2nd turning provision means in this invention, and is AA arrow line view of FIG. It is a BB arrow line view of FIG. It is explanatory drawing of the classifier used for the vertical roller mill which concerns on this invention. It is comparison explanatory drawing of this invention and the conventional classifier. It is explanatory drawing of a 3rd turning provision means. It is the schematic of the conventional classifier.

  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 also shows a vertical roller mill 5 that is pulverized into pulverized coal.

  A cylindrical casing 7 is erected on the base 6, and a coal supply / discharge unit 10 is provided on the upper side of the casing 7.

  A crushing table 8 is housed in the lower part of the casing 7, and a table driving device 9 is provided below the crushing table 8 so that the crushing table 8 is rotated at a constant speed by the table driving device 9. It has become. A primary air chamber 11 is formed between the base 6 and the crushing table 8, and a classification chamber 12 is provided above the crushing table 8 inside the casing 7.

  A primary air supply port 13 is attached to the lower end portion of the casing 7, and the primary air supply port 13 communicates with the primary air chamber 11. A nozzle ring 14 is provided around the pulverizing table 8, and a required number of air ejection ports 14 a are provided at equal intervals on the nozzle ring 14. The air outlet 14a is inclined at a required angle in at least the circumferential direction with respect to the vertical line. In addition, in FIG. 1, the state inclined also to the radial direction is shown.

  The primary air chamber 11 and the classification chamber 12 communicate with each other through the air jet port 14a, and primary air for transporting pulverized coal is sent from the primary air chamber 11 from the air jet port 14a. In the process of jetting upward and passing through the air jet port 14a, a swirl flow is given to the primary air from the inclination of the air jet port 14a.

  Thus, the nozzle ring 14 communicates with the primary air chamber 11 and the classification chamber 12 and functions as a primary air outlet and as a first swivel imparting means 31.

  Under the casing 7, there are provided three sets of roller pressurizing devices 15 that radiate through the casing 7, and the roller pressurizing devices 15 are provided at intervals of 120 ° and are mainly hydraulic cylinders. The pressure roller unit 18 includes a pressure cylinder unit 18 and a pressure roller unit 18 that can rotate in the vertical direction about a horizontal shaft 17. The pressure roller unit 18 further includes a pressure roller 19 that is rotatable.

  A table segment 20 that forms a ring-shaped recess is provided on the upper surface of the crushing table 8, and the pressure roller 19 is pressed against the recess of the table segment 20 by the pressure cylinder 16.

  The coal supply / discharge unit 10 includes a coal output casing 21 and a pipe-like chute 22 that penetrates the coal output casing 21 and extends into the casing 7.

  The lower end of the coal output casing 21 is opened and communicates with the classification chamber 12. Further, a pulverized coal feed pipe 23 is connected to the coal output portion casing 21, and the pulverized coal feed pipe 23 is connected to a burner (not shown) of a boiler.

  The chute 22 is on an extension of the rotation center of the crushing table 8, and a rotary shaft 28 installed in a double cylindrical shape around the chute 22 is supported so as to be rotatable about a vertical axis. The upper end of 22 is connected to a coal feeder (not shown), and the lower end is located above the center of the crushing table 8. A classifier 25 is provided in the middle of the rotary shaft 28, and the classifier 25 is located in the upper part of the classifying chamber 12 and is adjacent to the lower end opening of the coal output part casing 21. The classifier 25 is connected to the rotation driving unit 24 and is rotated by the rotation driving unit 24.

  The classifier 25 includes a required number of strip-shaped blades 26, which are arranged at a predetermined angular pitch in the circumferential direction and supported by the rotary shaft 28 via a blade support 27. The blade 26 rotates on a conical curved surface.

  As shown in FIGS. 2 and 3, a second turning imparting means 32 is provided on the inner wall surface of the casing 7 above the roller pressing device 15. The second swivel imparting means 32 is composed of rectifying plates 33 arranged at a required interval. The rectifying plates 33 are strips extending in the vertical direction, and at a required angle with respect to the bus bar of the casing 7. The swirl flow is imparted to the mixed flow of the rising primary air and pulverized coal (hereinafter referred to as the air mixed flow). Therefore, the swirl flow is given to the air mixed flow by the first swirl imparting means 31 and the swirl flow is further strengthened by the second swirl imparting means 32. If the swirl flow provided from either the first swirl imparting means 31 or the second swirl imparting means 32 is sufficiently strong, the other may be omitted.

  The classifier 25 used in this embodiment will be described with reference to FIG.

  The blade 26 is supported on the rotary shaft 28 via a blade support 27. The blade 26 is inclined so that the upper end 26a is separated from the center, and at a predetermined interval in the circumferential direction. It is arranged. The inclination angle α formed by the blade 26 with respect to the horizontal is preferably 60 ° to 40 °.

  As described above, the centrifugal force induced by the rotation of the classifier 25 increases as the diameter increases, and a large centrifugal force acts on the pulverized coal flowing through the upper portion (large diameter portion) of the classifier 25. A small centrifugal force acts on the pulverized coal flowing in the lower part (small diameter part).

  On the other hand, the air mixed flow that rises up the classification chamber 12 and flows into the blade 26 is given a swirl flow by the first swirl imparting means 31 and the second swirl imparting means 32, and the inflowing air mixed flow Centrifugal force is acting on itself. This centrifugal force has an effect of causing the air-mixed flow to drift to the outer diameter side.

  For this reason, primary air having a large flow rate, that is, a large fluid drag flows from the large diameter side of the classifier 25. Further, a large centrifugal force due to the rotation of the classifier 25 acts on the upper part of the classifier 25. Accordingly, a centrifugal force and fluid drag acting on the pulverized coal are applied such that a large fluid drag acts on the upper part of the classifier 25 where a large centrifugal force acts and a small fluid drag acts on the lower part where a small centrifugal force acts. Is balanced at the top and bottom.

  By balancing the centrifugal force and fluid drag acting on the pulverized coal at the upper and lower parts, the classification ability is equalized at the upper and lower parts, and the classified pulverized coal has no particle size variation.

  Further, by reducing the inclination angle α of the blade 26, the amount of change in direction when the air mixed flow flows into the classifier 25 is reduced, and the pressure loss is reduced. In addition, since the amount of change in the direction of inflow is reduced, it is possible to prevent the air mixed flow from flowing partially into the blade 26 and to fully exhibit the classifying ability of the classifier 25. .

  Furthermore, by reducing the inclination angle α of the blade 26, the height dimension of the classifier 25 can be reduced, and the height h of the vertical roller mill 5 can be reduced.

  FIG. 5 shows a comparison between the classifier 25 of the present invention and the conventional classifier 1. In FIG. 5, the left half represents the conventional art and the right half represents the present invention.

  In the classifier 25 of the present invention, by reducing the inclination angle α, the height is lowered from h2 to h1 with respect to the conventional classifier 1 without changing the upper radius Ra, and the lower radius Rb1. Is made smaller than the conventional radius Rb2, the lengths of the blades 4 and 26 can be made equal, that is, the inflow area of the pulverized coal mixed air to the classifier 25 can be made the same.

  Hereinafter, the operation of the vertical roller mill 1 will be described.

  The pulverizing table 8 is rotated, and massive coal is introduced from the chute 22 in a state where primary air is introduced from the primary air supply port 13. The massive coal flows down from the lower end of the chute 22 and is supplied onto the crushing table 8. The coal on the crushing table 8 is pulverized by the pressure roller 19 into powder, and the powdered coal rises on the primary air blown up from the air outlet 14a, and the primary air is the air. A swirling flow is given by the jet nozzle 14a.

  The pulverized coal having a large particle diameter falls in the middle of ascending, and the pulverized coal having a predetermined diameter or less reaches the classifier 25.

  The rising air mixed flow is further swirled by the rectifying plate 33 and reaches the classifier 25.

  As described above, a swirl flow is given to the air mixed flow, so that a centrifugal force is generated in the air mixed flow, and the air mixed flow flows in a large portion of the classifier 25 and the fluid of the air mixed flow. Drag increases. Further, the centrifugal force applied by the rotation of the blade 26 also increases at a portion where the classifier 25 has a large diameter.

  Accordingly, by applying a swirl flow to the air mixed flow flowing into the classifier 25, the fluid drag force due to the gas flow and the centrifugal force due to the classifier 25 can be balanced over the entire length of the blade 26. That is, the classification function can be effectively exhibited over the entire length of the blade 26, and the classification ability can be improved.

  Further, the blade 26 is inclined in a direction nearly horizontal (the inclination angle α is reduced), so that the height of the blade 26 is lowered. Further, when the air mixed flow crosses the blade 26, the pulverized coal having a large particle size collides with the blade 26 and falls, but the blade 26 is inclined so that it rebounds on the blade 26. The pulverized coal is turned downward, and the classification effect is improved by a synergistic effect with the action of gravity.

  The air mixed flow flows into the classifier 25 across the blade 26, and the classified air mixed flow flows into the coal output portion casing 21 from the lower end opening of the coal output portion casing 21. Thus, only pulverized coal having a particle size smaller than a predetermined diameter is discharged from the pulverized coal feed pipe 23 through the coal outlet casing 21 and supplied to a boiler burner (not shown).

  Next, FIG. 6 shows the third turning imparting means 35 which is another turning imparting means.

  The auxiliary air ejection nozzle 36 is placed in the casing 7 at a required equal position in the circumferential direction (4 equal positions in the figure), and the center line of the auxiliary air ejection nozzle 36 is tangential to the inner wall surface of the casing 7. It is provided as follows.

  By ejecting the auxiliary air 37 from the auxiliary air ejection nozzle 36, the swirl flow 38 can be imparted to the rising air mixed flow. The auxiliary air ejection nozzle 36 is not necessarily required to coincide with the tangential direction as long as the swirling flow is given to the rising air mixed flow.

  In the present invention, at least one or all of the first turning imparting means 31, the second turning imparting means 32, and the third turning imparting means 35 may be provided. Further, the swivel imparting means 31, 32, and 35 are selected so that the centrifugal force by the classifier 25 and the fluid drag force by the gas flow are balanced over the entire length of the blade 26.

  In the above description, the present invention has been described as a vertical roller mill for pulverized coal, but it goes without saying that the present invention can be implemented as a vertical roller mill for pulverizing cement raw materials.

DESCRIPTION OF SYMBOLS 4 Blade 5 Vertical roller mill 6 Base 7 Casing 8 Grinding table 10 Coal supply / exhaust part 11 Primary air chamber 12 Classifying chamber 15 Roller pressurizer 19 Pressure roller 22 Chute 24 Rotation drive part 25 Classifier 26 Blade 28 Rotating shaft 31 First turning imparting means 32 Second turning imparting means 33 Current plate 35 Third turning imparting means 36 Auxiliary air ejection nozzle 37 Auxiliary air

Claims (4)

  A pulverization table is provided at the lower part of the classification chamber, and is located at the upper part of the classification chamber, and is disposed so that the pulverized powder passes as an air mixed flow, and a swirl flow is provided to the rising air mixed flow. The classifier has a required number of blades that rotate about a vertical axis, and the blades are inclined so that their upper ends are separated from the vertical axis. The vertical roller mill is characterized in that the means is configured to apply a turning force so that the centrifugal force by the classifier and the fluid drag force by the gas flow are balanced over the entire length of the blade.   The vertical roller mill according to claim 1, wherein an air outlet inclined at least in the circumferential direction is provided around the crushing table, and a swirl flow is applied in the process of ejecting primary air from the air outlet.   The vertical roller mill according to claim 1, wherein rectifying plates that are inclined with respect to a generatrix of the inner wall surface are provided on the inner wall surface of the classifying chamber at predetermined intervals in the circumferential direction to impart a swirl flow to the rising air mixed flow.   2. A vertical roller mill according to claim 1, wherein auxiliary air jet nozzles are provided at required intervals on the inner wall surface of the classifying chamber, the auxiliary air is jetted tangentially from the auxiliary air jet nozzle, and a swirling flow is imparted to the rising air mixed flow. .

Images