WO2015049912A1

WO2015049912A1 - Vertical roller mill

Info

Publication number: WO2015049912A1
Application number: PCT/JP2014/069859
Authority: WO
Inventors: 卓一郎大丸; 有馬　謙一; 松本　慎治; 菅　啓史; 串岡　清則
Original assignee: 三菱日立パワーシステムズ株式会社
Priority date: 2013-10-01
Filing date: 2014-07-28
Publication date: 2015-04-09
Also published as: JP2015066544A; JP6275442B2

Abstract

The purpose of the present invention is to provide a vertical roller mill having a rotary classifier, by which the ratio of rough particles in a powdered coal product is reduced. Provided is a vertical roller mill having, in a housing, a rotary classifier (20) that classifies fine particles with small diameters and effuses the same to the outside by allowing to pass a solid-gas two phase flow in which a powder made of a pulverized solid is subject to gas flow conveyance, wherein the rotary classifier (20) is provided with a plurality of plate shaped rotary blades (22A) that are provided, at the same pitch in the circumferential direction, to a circumferential wall surface of a cone (21) which rotates inside the housing. With respect to a line orthogonal to outer tangent lines (La, Lb) of a rotation trajectory, the plate shaped rotary blades (22A) are installed so that the radial direction inner sides of the blades are inclined in the rotation direction. The angle of installation of the plate shaped rotary blades (22A) from the outer tangent lines (La, Lb) is set to be a value (α1 >α2) such that an installation angle (α1) of the blade upper end side is larger than an installation angle (α2) of the blade lower end side.

Description

Vertical roller mill

The present invention relates to a vertical roller mill applied to, for example, a pulverized coal-fired boiler, and more particularly to a vertical roller mill equipped with a rotary classifier.

Conventionally, in a coal-fired boiler, for example, raw material coal is charged into a pulverized coal machine (mill) such as a vertical roller mill 10 shown in FIG. 3 and pulverized pulverized coal is used as a fuel. In the vertical roller mill 10 shown in the drawing, inside the vertical roller mill 10, the grinding roller 13 turns while rotating on the grinding table 12 installed at the lower part in the housing 11. In addition, the code | symbol 14 in a figure is a coal input pipe which inject | throws-in raw material coal.

The raw material carbon introduced into the vertical roller mill 10 is pulverized by being caught between the pulverizing table 12 and the pulverizing roller to be pulverized coal. The pulverized coal is air-borne and transported to a rotary classifier 20 disposed above the inside of the housing 11 while being dried by hot air jetted from a throat (not shown) disposed around the grinding table 12. At this time, coarse particles having a large particle diameter are subjected to gravity classification which is dropped by gravity and returned to the crushing table 12, and therefore, the particles are repeatedly crushed until a desired particle diameter is obtained.

After the primary classification by the above-described gravity classification, pulverized coal of product particles including coarse particles is further classified by the rotary classifier 20 disposed on the top of the grinding table 12. As such a classifier, in addition to the rotary classifier 20, there is also a stationary type or a combination of a stationary type and a rotary type. The rotary classifier 20 performs classification by collision and inertial force by plate-like rotary blades, and is known to have high classification performance.

The pulverized coal which has been carried by air flow is dried by hot air and is further classified by passing through a rotary classifier 20. The classified pulverized coal passes through the pulverized coal outlet 15 communicating from the inside to the outside of the housing 11 from the inside of the rotary classifier 20, and is airflow-carried to the boiler by the primary air for conveyance.

For example, as shown in FIGS. 4 and 5, the rotary classifier 20 includes a large number of plate-like rotary vanes 22 arranged at equal intervals in the circumferential direction of the cone 21 rotating in the arrow direction (clockwise). As shown in FIG. 4, the plate-like rotary vanes 22 are flat plate-like members installed so as to have an inclination angle θ in the same direction. Note that the inclination angle θ in this case is with respect to the tangent L of the circular locus along which the cone 21 rotates.
As a result, a large number of inlet openings 23 penetrating the wall surface of the cone 21 are formed between the adjacent plate-like rotary vanes 22. The inlet opening 23 serves as an inlet and a flow passage through which a flow for conveying pulverized coal by air flow (hereinafter, referred to as “solid-gas two-phase flow”) passes and flows into the inside of the cone 21. Further, inside the cone 21, a wall surface 24 opposed to the inlet opening 23 is provided.

As a prior art related to such a rotary type classifier 20, as disclosed in, for example, the following Patent Document 1, the angle of the blade differs between the upper side and the lower side, that is, from the lower side in the side view Some have an inclination angle that increases in diameter toward the upper side.
Further, as disclosed in Patent Document 2 below, there is one in which the shape of the rotary blade is made wider at the upper portion than at the lower portion, and the coarse particle collision probability with the blade is made uniform in the upper and lower direction.

Unexamined-Japanese-Patent No. 4-349944 JP-A-8-266923

By the way, the fineness of pulverized coal pulverized by a pulverizer such as the vertical roller mill 10 is generally expressed by 200 # pass (particle ratio of 75 μm or less) and has a good correlation with the power required for the pulverization. On the other hand, in the pulverized coal-fired boiler, the unburned content when pulverized coal is supplied to the boiler has a high correlation with 100 # remaining (particle ratio of 150 μm or more). In this case, the proportion of pulverized coal coarse particles having a residual amount of 100 #, which is about 100 mesh or more, means the ratio of coarse particles in product pulverized coal which adversely affects the combustibility.
Therefore, it is necessary for the vertical type roller mill 10 for coal crushing applied to the pulverized coal burning boiler etc. to minimize the 100 # remaining to the 200 # pass.

As described above, the rotary classifier 20 rotates the cone 21 of the rotating body provided with the plate-like rotary vanes 22 and separates coarse particles by colliding them with the plate-like rotary vanes 22. Usually, a flat plate is used for the blade 22.
The conventional plate-like rotary vanes 22 are inclined (angle θ) in the direction in which particles collide with and repel the plate-like rotary vanes 22 with respect to the rotational direction, and are also inclined in the height direction. For this reason, if the width of the plate-like rotary vanes 22 is constant in the vertical direction, the rotational peripheral speed is different in the height (vertical direction) direction, and the probability that the particles collide is different in the height direction. For this reason, as shown in Patent Document 2, the width of the plate-like rotary vane 22 is increased at a portion where the radius of the rotary classifier 20 becomes large.

The above-described conventional plate-like rotary vanes 22 have different rotational peripheral speeds in the height direction, so, for example, as shown in FIG. An air flow containing a large amount of air easily enters from the lower side of the plate-like rotary vanes 22.
As for the inclination angle θ of the plate-like rotary vanes 22, 45 degrees, which has the smallest relation of 100 # remaining to the same 200 # pass, is adopted according to the grinding test result and the like. The inclination angle θ is constant from the upper portion to the lower portion of the blade because the rotary blade 22 is a flat plate.

However, for example, as shown in FIG. 6, change the installation angle of the classification blade, that is, the inclination angle θ of the plate-like rotary blade 22 from 45 degrees (line A in the figure) to 30 degrees (line B in the figure). The remaining 100 # for the same 200 # pass tends to increase.
On the other hand, at a fixed classifier rotation number (rotation number of cone 21 and rotary blade 22), as shown in FIG. 6, the ratio of 100 # remaining decreases by changing the inclination angle θ from 45 degrees to 30 degrees. Therefore, there is room for improvement by devising to minimize the 100 # remaining for the 200 # pass.
The present invention has been made in view of the above-mentioned circumstances, and the purpose thereof is that in a vertical roller mill equipped with a rotary classifier, the proportion of coarse particles in product pulverized coal (which adversely affects the flammability) 100) to reduce the ratio of 100 # remaining.

The present invention adopts the following means in order to solve the above-mentioned problems.
The vertical roller mill according to an aspect of the present invention is a rotary classifier that classifies fine powder having a small particle size and discharges it to the outside by passing a solid-gas two-phase flow that conveys powder obtained by pulverizing a solid by gas flow. In the vertical roller mill, the rotary type classifier includes a large number of plate-like rotary vanes arranged at equal pitch in the circumferential direction on the peripheral wall surface of the cone-shaped member which rotates in the housing, The plate-like rotary vanes are installed such that the inner side in the radial direction is inclined in the rotational direction with respect to a line orthogonal to the outer tangent of the rotation locus, and the installation angle of the plate-like rotary vanes from the outer tangent is The installation angle (α1) on the upper end side is set to a value (α1> α2) larger than the installation angle (α2) on the blade lower end side.

According to the vertical roller mill of the above aspect, the rotary classifier is provided with a large number of plate-like rotary vanes arranged at equal intervals in the circumferential direction on the peripheral wall surface of the cone-shaped member rotating in the housing. The installation is performed by inclining the inside in the radial direction to the direction of rotation with respect to the line orthogonal to the outside tangent of the rotation path, and the installation angle of the plate-like rotary vane from the outside tangent is Since the angle (α1) is set to a value (α1> α2) larger than the installation angle (α2) on the lower end of the blade, the lower end of the blade whose installation angle is smaller than the upper end of the blade The angle of attack against the air flow is increased. For this reason, the coarse particles that easily flow in from the lower end portion side of the blade easily collide with the plate-like rotary vanes, so on the lower end side of the plate-like rotary vanes, the coarse particles tended to flow in by the flow velocity distribution formation of the air flow. As a result, coarse particles are repelled downward and difficult to flow.

In the above aspect, the plate-like rotary vane has a vane shape obtained by bending a flat plate so that the installation angle (α1) at the upper end of the vane and the installation angle (α2) at the lower end of the vane are different. Is desirable.
Alternatively, the plate-like rotary vane has a three-dimensional vane shape formed so that the installation angle (α1) at the upper end of the vane and the installation angle (α2) at the lower end of the vane are different. Is desirable.
And as for the suitable plate-shaped rotary blade, the installation angle ((alpha) 1) at the said blade upper end part side is set in the range of 20-40 degrees, and the installation angle ((alpha) 2) at the said blade lower end part side is 40-60 degrees. Is set in the range of

According to the present invention described above, in the vertical roller mill equipped with a rotary classifier, the ratio of coarse particles (the ratio of coarse particles exceeding 100 mesh which adversely affects the combustibility) in the product pulverized coal is reduced. It becomes possible. For this reason, if the vertical roller mill of the present invention is applied to a pulverized coal-fired boiler, the ratio of coarse particles in product pulverized coal can be reduced, and the unburned component in ash can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the vertical roller mill which concerns on this invention, and is a principal part perspective view which shows the outline about the plate-shaped rotary blade installed with installation angles (alpha) 1 and (alpha) 2 in a rotary type classifier. is there. It is a figure which shows the partial classification efficiency with respect to the particle diameter of pulverized coal compared with a conventional structure about the rotary classifier which employ | adopted the plate-shaped rotary blade of this invention. It is sectional drawing which shows the example of a schematic structure of a vertical roller mill. In the conventional rotary classifier, it is a figure which shows the arrangement | sequence of the plate-shaped rotary blade | wing provided in the rotating cone. In the rotary type classifier shown in FIG. 4, it is a figure which shows inflow velocity distribution of the airflow which arises by the resistance difference etc. by a plate-shaped rotary blade. It is a figure which shows the relationship of 200 # pass (%) and 100 # remainder by the difference (45 degrees and 30 degrees) of the inclination angle ((theta)) of a plate-shaped rotary blade.

Hereinafter, an embodiment of a vertical roller mill according to the present invention will be described based on the drawings.
The vertical roller mill 10 shown in FIG. 3 is, for example, an apparatus (pulverized coal machine) for manufacturing pulverized coal to be a fuel of pulverized coal burning boiler. In the vertical roller mill 10, raw material coal is pulverized into pulverized coal, and the pulverized coal after gravity classification is classified by the rotary classifier 20. As a result, product fines classified through the rotary classifier 20 are classified as pulverized coal fuel having a desired degree of fineness from the pulverized coal outlet (milled powder outlet) 14 provided on the upper part of the vertical roller mill 10, The air is transported to the pulverized coal-fired boiler by the primary air.
The configuration of the vertical roller mill 10 according to this embodiment is the same as that of the prior art described above except for the plate-like rotary vanes 22A of the rotary classifier 20 described later, and therefore the detailed description thereof is omitted.

That is, in the vertical roller mill 10 according to the present invention, the solid-gas two-phase flow (pulverized coal + primary air) for conveying the pulverized coal (powder) obtained by crushing the raw material coal (solid) in an air flow passes through. The rotary type classifier 20 is provided in the upper part in the housing 11 for classifying the small fine powder of the above by centrifugal force and flowing it out to the pulverized coal burning boiler (outside). The rotary classifier 20 introduces a solid-gas two-phase flow into the interior of the cone from a large number of inlet openings 23 opened in the circumferential wall of a rotating cone (cone-shaped member) 21.

The above-described inlet openings 23 are formed between the plate-like rotary vanes 22A, which are arranged at equal pitches in the circumferential direction, with respect to the circumferential wall of the cone 21. In other words, the rotary classifier 20 includes a large number of plate-like rotary vanes 22A arranged at equal pitches in the circumferential direction on the peripheral wall surface of the cone 21 rotating in the housing 11, and the adjacent plate-like rotary vanes 22A An inlet opening 23 is formed therebetween.

For example, as shown in FIG. 1, the plate-like rotary vanes 22A according to this embodiment include tangents (outside tangents) La and Lb that are on the outer side in a rotation locus formed by rotation of the cone 21 and the plate-like rotary vanes 22A. With respect to the orthogonal line (radial line), the inside in the radial direction is inclined in the rotational direction. That is, the plate-like rotary vanes 22A are inclined such that the end side facing the inside of the cone 21 is positioned on the rotational direction side from the line orthogonal to the tangents La and Lb.

Furthermore, the installation angle of the plate-like rotary blade 22A, that is, the installation angle from the tangents La and Lb described above, is the installation angle (tilt angle) α1 at the blade upper end side, the installation angle (tilt angle) at the blade lower end side It is set to a value larger than α2 (α1> α2).
The plate-like rotary blade 22A shown in the drawing is a broken line M in the figure so that the installation angle α1 on the blade upper end side and the installation angle α2 on the blade lower end portion are different and the installation angle α1 on the blade upper end side is large. The blade shape which bent the flat plate is adopted. In this case, the broken line M in the figure coincides with the diagonal of the substantially rectangular flat plate.

The plate-like rotary blade 22A having the above-described structure has a blade area facing the flow because the attack angle of the plate-like rotary blade 22A against the air flow becomes large on the blade lower end side set at the installation angle α2 smaller than the blade upper end side. Will increase. For this reason, on the lower end portion side of the wing, coarse particles flowing in with the air flow easily collide with the wing surface.
That is, the coarse particles that easily flowed in from the lower end portion of the plate-like rotary vane 22A due to the formation of the inflow velocity distribution of the air flow easily collide with the surface of the plate-like rotary vane as the angle of attack increases. At the lower end portion side of the easy plate-like rotary vane 22A, the coarse particles are repelled downward and hardly flow into the cone 21. And since plate-shaped rotary blade 22A of such a shape turns into a simple blade shape of upper and lower integral, it can be easily manufactured, even if it changes installation angle alpha1 of upper and lower sides alpha2.

The plate-like rotary vane 22A may have a three-dimensional vane shape formed so that the installation angle α1 on the upper end side of the vane and the installation angle α2 on the lower end side of the vane are different. Specifically, the flat plate is formed into a curved surface or into a shape combining the curved surface and a flat surface so that the installation angle α1 on the blade upper end side is larger than the installation angle α2 on the blade lower end side 3 You may employ | adopt plate-shaped rotary blade 22A of a two-dimensional shape.
Even with such a plate-like rotary blade 22A, the same function and effect as the blade shape obtained by bending the flat plate at the broken line M can be obtained.

By the way, in order to obtain the effects described above efficiently and reliably, the plate-like rotary blade 22A described above sets the installation angle α1 on the blade upper end side to a range of 40 to 60 degrees, and the blade lower end side It is desirable to set the installation angle α2 of the above in the range of 20 to 40 degrees.

Thus, as shown in FIG. 2, for example, as shown in FIG. 2, the vertical roller mill 10 equipped with the rotary classifier 20 according to the present embodiment is coarse-grained which has an adverse effect on the combustibility due to an increase in unburned matter in product pulverized coal. It becomes possible to reduce the ratio, that is, the ratio of 100 # remaining to 200 # pass (particle ratio of 75 μm or less). For this reason, if the vertical roller mill 10 of the present embodiment is applied to a pulverized coal-fired boiler, the ratio of coarse particles in product pulverized coal can be reduced, and therefore the unburned component in ash can be reduced. FIG. 2 shows the case where the rotation speed of the cone 20 is 110 rpm.

By the way, in the embodiment mentioned above, although pulverized coal is handled as powder, the present invention is not limited to the embodiment mentioned above, for example, it is applicable also to powder other than pulverized coal, etc. It can change suitably in the range which does not deviate from a summary.

Reference Signs List 10 vertical roller mill 11 housing 12 grinding table 13 grinding roller 14 coal feeding pipe 15 pulverized coal outlet (fine powder outlet)
20 rotary classifier 21 cone (cone-shaped member)
22A plate-like rotary blade 23 inlet opening

Claims

In a vertical roller mill equipped with a rotary classifier in a housing that classifies fine powder having a small particle size and discharges it to the outside by passing a solid-gas two-phase flow that conveys powder obtained by pulverizing a solid through a gas flow.
The rotary type classifier includes a large number of plate-like rotary vanes arranged at equal pitches in a circumferential direction on a peripheral wall surface of a cone-shaped member which rotates in the housing.
The plate-like rotary vanes are installed such that the inner side is inclined in the radial direction with respect to a line orthogonal to the outer tangent of the rotation locus, and the installation angle of the plate-like rotary vanes from the outer tangent is The vertical roller mill in which the installation angle (α1) on the blade upper end side is set to a value (α1> α2) larger than the installation angle (α2) on the blade lower end side.
The plate-like rotary blade has a blade shape obtained by bending a flat plate so that the installation angle (α1) on the blade upper end portion side and the installation angle (α2) on the blade lower end portion side are different. Vertical roller mill as described in.
The plate-like rotary blade has a three-dimensional blade shape shaped so that the installation angle (α1) at the upper end of the blade and the installation angle (α2) at the lower end of the blade are different. The vertical roller mill according to 1.
The installation angle (α1) at the blade upper end portion side is set in the range of 40 to 60 degrees, and the installation angle (α2) at the blade lower end portion side is set in the range of 20 to 40 degrees The vertical roller mill according to any one of to 3.