JPH0268149A - Vertical roller mill - Google Patents

Abstract

PURPOSE:To simply and certainly perform the maintenance and inspection, member replacement or disassembling work of a rotary classifier by providing a connection part making the rotary classifier and a rotary cylinder detachable. CONSTITUTION:A plurality of grinding rollers 13 are arranged to the upper surface of a rotatable grinding table 3 and a raw material supply pipe 2 extending in a vertical downward direction is provided to the center of the upper part of a cylindrical mill housing 8 almost receiving said table 3 and rollers 13. A rotary cylinder 27 having rotary shaft function is provided to the outer periphery of the raw material supply pipe 2 and a rotary classifier 31 having a plurality of classifying blades 18 is mounted to the rotary cylinder 27. Further, bearings 23, 24 are provided between the mill housing 8 and the rotary cylinder 27, and the rotary classifier 31 and the rotary cylinder 27 are made detachable by a connection part 29. As a result, the maintenance and control, member replacement or disassembling work of the rotary classifier can be performed simply and certainly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vertical roller mill, and more particularly to a vertical mill that has an improved support structure for a rotary classifier that rotates around a raw material supply pipe.

[Conventional technology]

In recent years, low-pollution combustion (low NOx, low NOx,
As a result, pulverized coal mills were required to have higher performance.

A vertical roller mill equipped with a grinding table and a plurality of rollers is used as a typical type of mill for finely grinding lumps such as coal, raw materials for cement, or raw materials for new materials.

This vertical roller mill pulverizer is located at the bottom of a cylindrical casing and is driven by a motor with a speed reducer, and has a disc-shaped pulverizing table that rotates at low speed on a horizontal plane, and a pulverizer that rotates the outer periphery of its upper surface in the circumferential direction. It is equipped with a plurality of crushing rollers that are moved to different positions by being pressed down by hydraulic pressure or springs. The material to be crushed is supplied from the center chute to the center of the crushing table, and due to the rotation of the crushing table and centrifugal force, it moves to the outer periphery in a spiral trajectory on the table, and is crushed by the crushing race surface of the table. It gets caught between the rollers and is crushed. Hot air sent from a blower through a heat exchanger is guided to the base of the mill housing, and this hot air is blown up from the air throat between the outer periphery of the grinding table and the inner periphery of the mill housing. There is. The powder after pulverization is dried while rising inside the mill housing by hot air blown up from the air throat. The powder and granules transported to the upper part of the mill housing are classified by a rotary separator (rotary classifier) provided at the upper part of the mill housing, and fine powder with a predetermined particle size or less is transported by hot air.

In the boiler, the coarse powder that does not pass through the zero classifier, which is sent to the pulverized coal burner or the fine powder storage bin, falls by gravity onto the grinding table, and does not reach the raw material that has just been fed into the mill or the classification section. (primary classification) is crushed again together with coarse powder.

Most of the above-mentioned vertical roller mills are internal circulation closed circuit grinding systems that have a classification section in the upper part of the mill, and the performance of not only the grinding section but also the classification section is closely related to the characteristics of the grinding section, and the fine powder of the product is improved. have a great influence on character.

Recently, rotary separators have been increasingly used as classifiers instead of cyclone separators. The rotary separator has a plurality of blades arranged at equal intervals in the circumferential direction on a rotor provided at the center shaft of the mill, and is rotated by a drive system independent of the rotation drive system of the grinding table.

In the mill grinding section, the powder and granules blown up by hot air are
Particles larger than a predetermined particle size are driven to the outer periphery of the separator by the centrifugal force of the airflow generated by the rotating classification blades, and fall back to the crushing section by the action of gravity. On the other hand, fine powder smaller than a predetermined particle size passes between the rotating blades and is discharged to the outside of the mill as product fine powder.

The main reasons behind the widespread use of rotary separators can be summarized as follows.

i) More than ever before, particle size ranges and particle size distributions must meet predetermined requirements. This is not only required to simultaneously achieve low NOx and low unburned content in pulverized coal burners, but also is strongly required in the cement and new material manufacturing fields.

ii) There is a need for improved responsiveness to load fluctuations. This is mainly used to handle load fluctuations in pulverized coal-fired boilers, and is advantageous compared to cyclone separators because it allows rotational speed control.

4 and 5 show the support structure of a rotary classifier according to the prior art.

In Fig. 4, 400 is a raw material, 403 is a vane, 404 is a rotary classifier, 405 is an oil seal, 40
7 is a belt sprocket for rotational driving, and 408 is a belt. In the example shown in FIG. 4, the rotary classifier is completely independent from the center chute 401, and is fixed to the rotary tube 402, with the mill housing 409 and the rotary tube 40
It has a structure that rotates while being supported by two bearings 406 between the two.

In FIG. 5, 500 is a raw material, 501 is a fixed chute, 502 is a rotating cylinder, 503 is a classification vane, 504 is an upper main body casing, 506 and 507 are bearings, 508 is a reduction gear, and 509 is a product fine powder. In the example shown in FIG. 5, the classifier is similarly supported by two bearings 506 and 507, but the location of the bearings is unique. It is interposed between the connecting body of the bearing 506 above the mill, and the classifier is attached to the bearing 5 of the part.
07 is interposed between the fixed chute 501 and the rotating cylinder 502.

In all of these rotary classifier support structure examples, the rotary classifier main body is integrated with the rotating cylinder 402, 502, and in order to replace parts of the rotary classifier, the entire upper mill housing 409 must be disassembled and lifted upward. must be replaced. In addition, the mill housing 409 of the rotary classification mechanism also has
There are no windows that would allow the rotary classifier to be dismantled or parts replaced. Rotary classifiers are capable of producing particle concentrations that are much higher than conventional wisdom (coal/air weight ratio: 5 to 50).
), recent research has revealed that
Furthermore, there are many factors that are disadvantageous to the stable continuous operation of a rotary classifier over a long period of time, such as that the transport air is hot air at 200 to 300° C. and that the airflow contains a considerable proportion of steam. For this reason, consideration should be given to the case where the rotary classifier is damaged due to some reason.

[Problem to be solved by the invention]

The purpose of the present invention is to solve these problems by providing a rotary classifier that can be easily maintained, inspected, replaced with parts, or disassembled.
To provide a vertical roller mill which is also reliable.

[Means to solve the problem]

The present invention was made to solve the above problems, and
The present invention is characterized in that a rotary classifier and a rotating cylinder serving as a rotating shaft of the classifier are configured to be detachable. Grinding rollers 13, a substantially cylindrical mill housing that accommodates them, a raw material supply pipe provided at the center of the upper part of the mill housing and extending vertically downward, and a rotating cylinder having a rotating shaft function provided on the outer periphery of the raw material supply pipe. , a rotary classifier that is attached to the rotary cylinder and has a plurality of classification blades, and a vertical roller mill that has a bearing between the mill housing and the rotary cylinder, a connection part that allows the rotary classifier and the rotary cylinder to be attached and detached. This is achieved by a vertical roller mill that is characterized by being equipped with.

Further, the present invention is characterized in that a window member having a space through which the rotary classifier can pass is provided on the side wall of the mill housing.

〔Example〕

The present invention will be explained below using examples.

FIG. 1 is a side sectional view of a vertical roller mill equipped with a rotary separator (hereinafter referred to as a rotary classifier) showing one embodiment of the present invention.

The raw material to be crushed 1 is supplied from a raw material supply pipe (center chute) 2 fixed to the mill housing 8 so as to be on the center axis of the mill, falls onto the crushing table 3 rotating at low speed, and is crushed by centrifugal force. sent to the department. An annular grinding ring 6 having a grinding race 7 engraved on its upper surface is attached to the outer periphery of the grinding table 3. The raw material 1 to be pulverized is pulverized on the pulverizing race 7 by the compression and shearing action of the pulverizing rollers 13 that rotate in a compressed state. The pulverized powder and granules are conveyed above the mill by hot air 9 blown up from an air throat 10 disposed around the outer periphery of the pulverizing table 3. Among these granules, coarse particles do not reach the rotary classifier 31, fall and circulate due to gravity (first classification), and are re-pulverized. Among the powder particles that have passed through this primary classification area, fine particles pass through the rotary classifier 31 and are discharged from the fine powder discharge duct 21 to the outside of the mill system.

Relatively coarse particles are driven to the outer periphery of the rotary classifier 31 in the radial direction by the aerodynamic centrifugal action of the rotary classifier 31, fall and circulate due to gravity (secondary classification), and are re-pulverized in the crushing section.

The rotary classifier 31 has a structure in which a plurality of plate-like classification blades 18 are radially attached to a rotary classifier rotor 17 at equal intervals in the circumferential direction. It is attached to the support/drive system.

The mill housing 8 at the same height where the rotary classifier 31 is attached is constituted by several frames and a plurality of housing windows 16 having a size that allows at least the main body of the rotary classifier 31 to be taken in and out. Reference numeral 29 denotes a reverse threaded connection part that allows the rotary classifier 31 and the rotating cylinder 27 to be attached and detached.

FIG. 2 is a detailed structural diagram of a rotary classifier which is the main part of the present invention. The rotary classifier 31 is rotated by driving a rotary cylinder 27 from the outside as a rotor, which is provided on the outer periphery of a raw material supply pipe (center chute) 2 fixed to the mill housing 8 .

This rotating cylinder 27 has a rotating cylinder 27 in its upper part.
It is held and rotated by a bearing holder 25 attached to the mill housing 8, and two lower bearings 23 and an upper bearing 24 interposed between the respective member bearing housings 26 and 30 fixed to the mill housing 8. At the lower end of the bearing holder 25, a classifier holding element 28, which is a connecting part between the main body of the rotary classifier 31 and the rotor, is attached, and is mechanically connected by a thread opposite to the screw carved in the lower part of the bearing holder 25. has been done.

The classifier holding element 28 includes a rotary classifier rotor 17
and plate-shaped classification blades 18, which are attached at equal intervals in the circumferential direction, are arranged radially in the radial direction. An oil seal 19 is provided at the lower end of the rotary classifier 31 to prevent dust from entering between the raw material supply pipe (center shade) 2 and the rotary classifier 31 . If it is necessary to inspect or repair the angle of the classification blade 18, the shape of the classification blade 18, the replacement of worn parts of the rotary classifier 31, the oil seal 19, etc., the rotary classifier 31 must be By means of the screw connection 29,
By disassembling the rotary classifier 31 from the bearing holder 25, it is taken out from the mill housing window 16 and inspected.
It can be repaired.

In the support structure of the rotary classifier 31 of the present invention, the rotary classifier 3
1 is attached to the rotor bearing holder 25 and rotating cylinder 27 via the classifier holding element 28, so that the time and effort of disassembling the mill housing 8 is saved when performing maintenance and inspection of the rotary classifier 31 or replacing parts. No work is required at all. In order to cope with this effect, the mill housing 8 is configured with a plurality of mill housing windows 16 large enough to allow the rotary classifier 31 to be inserted and removed. The rotary classifier holding element 28 and the bearing holder 25 are mechanically connected by a reverse threaded connection 29, and the rotary classifier 31
There is little risk that the connection will loosen due to rotation.

FIG. 3 is a diagram showing the measurement results of the vibration displacement of the mill housing with respect to the dimensionless rotational speed of the rotary classifier. In the figure, I shows the measurement results of the rotary classifier according to the present invention (Fig. 2), and ■ shows the vibration characteristics during pulverization and classification for pilot mills equipped with the rotary classifier according to the prior art (Fig. 5). This is a comparison. It has been shown that for both mills, there is a natural frequency condition at the non-dimensional rotational speed Ns/NS*ζ1.2, but the support method of the rotary classifier according to the present invention has a vibration displacement of about half. be. This difference is considered to be due to the influence of the arrangement of the bearings that support the rotor of the rotary classifier.

As described above, by applying the classifier holding structure of the present invention to the rotary classifier of a vertical mill, the operability of the mill that operates under more severe and diverse conditions than before can be greatly improved. Such an improvement effect can improve the operating condition of the entire coal-fired couplant.

A vertical roller mill equipped with a rotary classifier according to the present invention,
It is not limited to mills for pulverized coal-fired boilers or solid fuel-fired boilers such as petroleum coke as shown in the above examples, but also for cement mills (for finishing), pig steel slag mills, or for special purposes such as pulverizing ceramic raw materials, pigments and talc. It can also be applied directly to manufacturing mills.

〔Effect of the invention〕

According to the vertical roller mill of the present invention, parts replacement and maintenance and inspection of the rotary classifier main body are significantly facilitated without disassembling the upper structure of the mill housing, the center chute, or the rotary classifier supporting parts such as bearings. As a result, the operability of the rotary classification vertical roller mill, which is operated more harshly and in a variety of ways than in the past, is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a vertical roller mill showing an embodiment of the present invention, Fig. 2 is a detailed structural diagram of a rotary classifier to which the present invention is applied, and Fig. 3 is a dimensionless rotation of the classifier. 4 and 5 are cross-sectional views of a rotary classifier of a vertical roller mill according to the prior art. 1... Raw material, 2... Raw material supply pipe, 3... Grinding table, 6... Grinding ring, 8... Bell housing, 9
... Hot air, 10 ... Air throat, 13 ... Grinding roller, 16 ... Mill housing window, 17 ... Rotating classifier rotor, 18 ... Classifier blade, 21 ... Fine powder discharge Duct, 22... Product fine powder, 23... Lower bearing, 24... Upper bearing, 25... Bearing holder, 26...
...Bearing housing, 27...Rotating cylinder, 28...
Classifier holding element, 29... Reverse screw connection, 30
...Bearing housing, 31...Rotary classifier. Applicant Babcock-Hitachi Co., Ltd. Agent Patent Attorney Takeshi Kawakita Nagaga Raw material to be crushed Raw material to be crushed To be crushed raw material supply pipe Grinding table Grinding table Shirt Grinding lace mill housing Hot air grinding roller Grinding roller shaft Grinding roller Rotating shaft Mill housing Window rotating classifier Rotato phase 18 " 17 " 23: Lower bearing 24: Upper bearing 25: Bearing E 7-10 ~ 1□/ □2 Rotational direction

Claims (2)

[Claims] (1) A rotatable grinding table, a plurality of grinding rollers 13 arranged on the top surface of the grinding table, a nearly cylindrical mill housing housing them, and a raw material supply provided at the center of the upper part of the mill housing and extending vertically downward. A rotary cylinder having a rotary axis function provided on the outer periphery of the raw material supply pipe, a rotary classifier attached to the rotary cylinder and having a plurality of classification blades, and a vertical shaft having a bearing between the mill housing and the rotary cylinder. A vertical roller mill, characterized in that the rotary classifier and the rotary cylinder are provided with a connection part that allows attachment and detachment of the rotary cylinder. (2) The vertical roller mill according to claim (1), characterized in that a window member having a space through which a rotary classifier can pass is provided on the side wall of the mill housing.