JPH02261554A - Vertical type roller mill - Google Patents

Abstract

PURPOSE:To make a grinding part compact and to easily perform attachment and detachment of a roller by integrally constituting a roller supporting frame of both a plurality of brackets supporting the rotary shaft of the roller from the center axis side of a mill and the skirtlike damming bodies joining these brackets. CONSTITUTION:A housing 17, a grinding table 3, a grinding race 26 and the grinding rollers 7 are provided. Further a roller supporting frame 10 is provided which supports the rollers 7 so as to arrange them on the table 3 in the equiintervals and also transmits the pressure loading exerted by the pressure devices 12 to 16. The frame 10 is integrally constituted of both a plurality of brackets 10d supporting the rotary shafts 9 of the rollers from the center axis 5 side of the mill and the skirtlike damming bodies 10b joining the brackets. A horizontal plane pressure receiving part 10c which receives pressure loading exerted by the pressure devices 12 to 16 via d roller pivot 12 is provided to the upper part of this integral constitutional body. As a result, a grinding part can be made compact and the attachment, and detachment work of the roller is easily performed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a vertical roller mill for pulverizing coal, cement raw materials, and other solid raw materials into fine powder, and is particularly characterized by a method of supporting the pulverizing rollers. This invention relates to a vertical roller mill.

[Conventional technology]

In coal-fired boilers, low-pollution combustion (low NOx, reduced unburned matter) and rapid load fluctuation operations (changes in coal feed amount) are being implemented, and as a result, pulverizers (mills) are also required to have higher performance. became.

A vertical roller mill equipped with a crushing table and multiple rollers is used as one type of crusher to finely crush lumps such as coal, raw materials for cement, or raw materials for new materials. It is solidifying its position.

This type of crusher is explained with reference to FIG. 1. This type of crusher is driven by a motor having a speed reducer in the lower part of a cylindrical mill casing (mill housing) 17, and rotates at a low speed on a horizontal plane. 3, and a plurality of crushing rollers 7 which are rotated by being pressed by hydraulic pressure or a spring at positions that equally divide the outer peripheral portion of the upper surface in the circumferential direction.

The material to be crushed, which is supplied from the raw material supply pipe 2 to the center of the crushing table, moves in a spiral trajectory on the table due to the rotation of the crushing table and the centrifugal force, and moves to the outer periphery of the table by the grooves of the crushing race 26 of the table. It gets caught between the surface and the crushing roller and is crushed. Hot air 29 sent through a duct is guided to the base of the mill housing 17, and this hot air blows up from an air throat 28 between the outer periphery of the grinding table and the inner periphery of the mill housing. ing.

After pulverization, the granular material is dried while rising inside the mill housing by hot air blown from the air throat. The powder transported to the upper part of the mill housing is classified by a cyclone separator or rotary classifier 30 installed at the upper part of the mill housing, and fine powder with a predetermined particle size or less is transported by hot air. Sent to storage bin. Coarse powder of a certain particle size or more that does not pass through the classifier falls onto the grinding table,
It is ground again along with the fresh material that has just been fed into the mill. In this way, crushing is repeated by the crushing rollers.

The grinding mechanism in such a vertical roller mill may be based on compression or shear between the grinding race surface on the table and the roller. In order to optimize such grinding conditions, various support structures for rollers have been proposed.

[Problem to be solved by the invention]

As shown in FIG. 8, the conventional roller support/pressure method uses a crushing roller 61 and a roller shaft 6 that supports it.
3 on the outside of the crushing roller 61, that is, the mill housing 78
Since the crushing roller 61 is supported from the side by the roller bracket 62, there is a problem in that a large space is required outside the crushing roller 61. This space is required only for the support structure of the crushing roller 61, and has nothing to do with the diameter Drac of the crushing race 76 (the diameter Drac of the crushing race 76 is a value proportional to the crushing capacity). ). Therefore, the above-mentioned space does not contribute in any way to improving the grinding capacity of the mill. If the space around the pulverizing roller 61 increases, the residence time of wasted coal that does not contribute to pulverization will increase accordingly, and the pressure loss within the mill will increase. Additionally, the amount of air required to transport the coal increases, making the cost of powering the blower high. Furthermore, as the amount of air increases, the C/A (mass flow rate ratio of pulverized coal to primary air) at the pulverized coal injection nozzle at the burner outlet freezes, which is disadvantageous for low-pollution, high-efficiency combustion of pulverized coal. . DSS operation (Daif
y 5tartStop (daily start and stop) coal-fired boiler requires a mill with good responsiveness.

In the conventional type, the response of mill coal output tends to be delayed due to the large capacity of the crushing section at startup or during load fluctuations. In addition, since the outer periphery of the grinding table 73 is set to be slightly larger, there is also the problem that the manufacturing cost of the mill increases.

As for the prior art related to the support structure of the crushing roller, see No. 9
As shown in the figure, the idea of providing the bearing 173 of the roller 172 on the outside of the mill housing 174 (1983-
51649). In this example, the structure of the crushing section is compact, but the structure of the roller support section provided on the outside of the mill housing 174 is somewhat large, resulting in an increase in the size of the mill as a whole. 20 The feature of the roller support structure is that there is no need to supply lubricating oil etc. into the mill,
The purpose is to prevent contamination (mixing of impurities) into the manufactured fine powder.

In the prior art (Japanese Patent Application Laid-open No. 106650/1983) shown in FIG. 10 (axial sectional view) and FIG. 11 (view from above),
Roller brackets (pressing members 108 to 110) are used to provide support for the shafts of the talashing rollers 105 to 107 on the center axis side of the mill (inside the rollers), and these roller brackets 108 to 110 are connected to connecting tools (center pillars). 14). According to this method, the space outside the crushing roller 105 is reduced, making it possible to prevent unnecessary accumulation of particles. However, for the work associated with installing the roller 105, although the connecting tool will play a role in preventing it from falling, an auxiliary member is required to keep the roller 105 stationary when the pressure ring 111 is placed on the race from above. Therefore, it cannot be said that the structure is simple like the conventional example shown in FIG.

An object of the present invention is to propose a new support structure for crushing rollers in a vertical mill in order to solve the above-mentioned problems.

[Means for Solving the Problems] The above object is to provide a mill housing that stands upright, a grinding table that rotates within a horizontal plane inside the mill housing, and a groove surface that is provided on the top surface of the table and has an arcuate cross section along its outer periphery. a crushing race having a pulverizing race, a plurality of pulverizing rollers having an arcuate cross section provided in contact with the grooved surface of the pulverizing race, a pressure device applying a predetermined pressure to the pulverizing rollers, and a crushing roller placed on a table. In a vertical roller mill, the roller support frame includes a plurality of roller support frames that support the rollers so as to be arranged at equal intervals and transmit pressure from a pressure device to the rollers, and the roller support frames include a plurality of roller support frames that support the rotating shaft of the roller from the mill center axis side. It is integrally constructed of a bracket and a skirt-like weir body that connects them, and is characterized in that a horizontal pressure-receiving part is provided on the upper part of this integrated structure to receive pressurizing force from a pressurizing device via a roller pivot. Achieved by a vertical mill.

[Function] By adopting the structure of the roller support frame according to the present invention, the space around the crushing table can be reduced, and a vertical roller mill with a compact crushing section can be realized. This reduces the amount of particles retained in the crushing section, that is, the holdup, and improves the responsiveness of coal extraction at startup or during load fluctuations. In addition, the reduction in hold-up in the crushing section reduces pressure loss, so the amount of air blown to the mill is reduced.

Furthermore, since each roller is supported by an integrated roller support frame, even if the roller gets caught in a foreign object or something goes wrong with the roller's pressure mechanism, there will be no problem of the roller tipping over. . Furthermore, even during inspection work with the mill stopped and pressure removed,
Since the rollers stand still on the race, there is no risk of the rollers falling over, and no auxiliary means are required.

In the case of the present invention, since the crushing race diameter Drac, which is related to the crushing capacity (as a parameter of the scale-up law of the crushing section), is the same, the crushing capacity of the mill is not sacrificed in any way compared to the conventional example.

Since the roller shaft support part of the roller bracket is located on the central axis side of the rotary table, the space between each roller becomes small, and the amount of coal that can be held in the crushing section is slightly reduced.

Therefore, in special cases where the mill is operated under an excessively high load, there is a possibility that coal may overflow from between the rollers. In such cases,
It is predicted that the crushing power will increase slightly due to the increased rolling resistance of the rollers.

Under high load conditions, the amount of particles to be crushed in the crushing section increases, and there is a possibility that particles may overflow from the roller support frame of the present invention to between the rollers. Therefore, the amount of raw material to be crushed that is fed to the crushing section of the rollers is controlled by a skirt-shaped weir between the rollers of the 20-roller support frame.

In this case, the coal holding up of the space within the roller support frame increases.

〔Example〕

FIG. 1 shows the structure of a vertical roller mill embodying the present invention as a longitudinal cross-sectional view including the central axis of the mill. FIG. 2 shows the structure of the crushing section as viewed from above.

The raw material to be crushed 1 is supplied into the mill from a raw material supply pipe (center chute) 2 provided downward on the central axis of the upper part of the mill, and is placed at the lower part of the mill and rotates around the table rotation axis 5 on a horizontal plane at low speed. It falls onto the grinding table 3 which rotates. The raw material 1 to be crushed on the crushing table 3 is fed to the outer periphery of the crushing table 3 by centrifugal force and enters the crushing race 26 .

The crushing roller 7 rolls on the top of it in a compressed state to crush it.

The crushing race 26 is carved along the outer periphery of the crushing table 3 on the top of the crushing ring 6 attached to the ring rod so that its cross section has a substantially arc shape. This crushing race 2
The raw material 1 to be crushed is compressed and crushed between the crushing roller 6 and the crushing roller 7, and the feature of this mill lies in the support structure of this crushing roller rough and the structure of the mill housing 17 accompanying it.

The crushing roller 7 rotates around a fixed roller shaft 8 (bearings or oil seals are omitted in the figure). The roller shaft 8 is supported by a roller support frame 10 having a shaft support portion on the central axis side of the mill.

This roller support frame 10 according to the present invention includes a support portion (bracket: arm type) of the roller shaft 8 corresponding to each crushing roller rough, and a roller support frame 1
An upper flat frame 10c provided with a groove surface on which a roller pivot 12 serving as a pressurizing fulcrum of 0 is placed, and a skirt-shaped weir body 10b provided on each arm-shaped roller shaft support part are integrated.

FIG. 2A is a perspective view of this monolithic support frame. Planar frame body 1 which is the upper part of roller support frame 10
The center of 0c is hollowed out to have a substantially triangular shape, from which the raw material to be crushed 1 and the group of particles circulating from the classification section are supplied onto the crushing table 3.

There is a skirt-shaped inverted weir body 10b between the arm-shaped roller supports, and as shown in FIGS. 3 and 3A, the powder 30 overflows between the respective crushing roller rows under high load. It is designed so that it never comes out. When the particle group 30, which is the raw material to be crushed, overflows between the crushing roller roughs, the transfer resistance of the crushing roller 7 increases, and as a result, the crushing efficiency decreases. There is a space 1 below each arm-shaped roller support part and each weir body 10b, and a space between the crushing table 3, so that the powder and granules, which are the raw materials to be crushed, are smoothly crushed by the crushing roller 7 and the crushing race 26. It is now sent to the department.

As shown in FIG. 2, in the flat frame body 10c which is the upper part of the roller support frame 10, two roller pivots 12 are installed at symmetrical positions with the roller shaft 8 in between in the upper part of the crushing roller rough. There is. This roller pivot 12 serves as a fulcrum for the roller support frame 10 against pressure from above. Integrated roller support frame 1
A configuration in which a large number of roller pivots 12 are used as fulcrums relative to the roller support frame 10 is almost excessively constrained, but under most conditions, the roller pivots 12 are
It is fixed between the grooves provided in the lower pressurizing frame 13 and will not loosen. For some reason, one of the crushing rollers
If the spring 14 operates abnormally, the impact will be applied to the spring 14.
The elastic deformation of is absorbed. Above the roller pivot 12, a lower pressure frame 13 and a pressure frame 15 are provided with a pressure spring 14 interposed therebetween. The initial setting load of the crushing roller rough is set by pulling the tension iron 16 downward to a predetermined condition and compressing the spring 14 under the pressure frame 15. In this example,
Since the support portions of each roller shaft 8 are concentrated on the mill center axis side, the space on the outer peripheral side of the crushing roller rough is reduced compared to the conventional example shown in FIG. The outer diameter Dtab of the grinding table 3 is the same in both examples, but in the embodiment of the present invention, the mill housing 17 changes its diameter upward to the sixth
The structure is smaller than the conventional example shown in the figure. That is, the mill housing 17 around the crushing portion has a truncated cone shape with a slightly large slope. Mill housing 1 on the upper side of the crushing section
Regarding the diameter Du of No. 7, Du of the embodiment of the present invention is significantly narrowed to 82% of that of the conventional example shown in FIG.

Therefore, the volume of the crushing section of the roller mill according to this example (however, the volume of the crushing roller 7 and roller bracket 10d is also included. When evaluating by subtracting these volumes,
The reduction rate of the space in the crushing section will further increase), which is roughly estimated to be 83% of the conventional example. With this structural setting, the volume of the crushing section of the roller mill is reduced, so the responsiveness of the mill is improved, and the pressure loss of the mill is reduced due to the reduction in coal hold-up in the crushing section. Furthermore, in the embodiment of the present invention, since each crushing roller 7 is supported by the roller support frame 10 having an integral structure, there is no problem of the rollers falling over due to an unexpected accident during roller installation or maintenance inspection. . Moreover, even if the crushing roller 7 catches foreign matter during operation, there is no danger of the roller falling down.

Note that the spring 14 alleviates the impact caused by the foreign matter being caught. Especially small to medium size (crushing capacity 2ton/hr)
If the roller support method according to the present invention is adopted in roller mills of the following classes), the roller installation work will be greatly simplified. Since the roller rests naturally on the grinding race 26, no auxiliary equipment is required to stand the roller up.

The powder and granules generated by being crushed by the crushing roller rough are blown into hot air 29 from an air throat 28 fixed to the inner wall of the mill housing 17 on the outer peripheral side of the crushing table 3.
conveyed to the upper part of the mill. Among the transported powder and granular materials, those that are quite coarse fall down due to gravity and undergo primary classification)
, is re-pulverized in the crushing section. On the other hand, the relatively coarse particles that have passed through this gravity classification zone are repelled to the outside of the classifier by the centrifugal action of the rotary classifier (
Secondary classification) It falls by gravity and is re-pulverized in the crushing section. The rotary classifier consists of a rotary classifier cylinder 20 around a raw material supply pipe (center chute) 2, a classifier rotor 21 attached to the lower part of the cylinder, and a plurality of elongated plate-shaped plates arranged at equal intervals in the circumferential direction. It is composed of a rotating classification blade 22. The fine powder that has passed through the rotary classification section is transferred to the outside of the mill system from the product fine powder discharge duct 24 as product fine powder 25.

If the volume reduction due to the reduction in the diameter of the mill housing 17 is replaced by an approximately equivalent cylinder, the cylindrical diameter of the housing 17 of the mill according to the present invention will be as follows, since the height of the crushing section is the same. Since the reduction in the horizontal cross-sectional area of the mill housing 17 corresponds to the reduction in the volume of the crushing section, the volume is reduced to (0,91)2 to 0.83 times that of the conventional example.

The characteristics of a mill that employs the roller support structure of the present invention will be described based on experimental results.

FIG. 4 summarizes the results of the relationship between the fine particle size (200 mesh bath, wt%) and the coal feeding load rate, and compares the characteristics of the mill of the present invention and the conventional mill. It can be seen that under relatively high load conditions, the present invention has a larger crushing capacity and a higher crushing ability. This means that in conventional mills, particles that would stay in the crushing section needlessly (not being crushed) are quickly transferred to the classification section, and are crushed more reliably in the crushing section. This is because of this. In addition, if the support structure of the crushing roller has changed,
Although the parameters governing the capacity of the roller mill crushing section, such as the load, the diameter of the crushing race 26, and the rotation speed of the rotary table 3, are the same, the effective friction coefficient actually involved in crushing is slightly different in this example. increase Incidentally, the grinding capacity Q of a mill capable of grinding particles to a predetermined particle size or higher is given by the following equation.

QcoμeMwD − (1) μe here:
Effective friction coefficient M = load W: table rotation speed D = grinding race diameter.

In this embodiment, D is set the same as in the conventional method, so
This means that the crushing ability was not sacrificed. However, in this embodiment, since the space of the -order classification section is reduced, slightly coarser powder and granules are transported to the secondary classification section than in the conventional method. Therefore, it is predicted that the load on the rotary classifying section will be slightly higher than that of the conventional type, although the capacity of the crushing section is slightly increased (Fig. 4).

Figures 5 and 6 show the starting characteristics. In this way, the response characteristics of this embodiment and the conventional example will be compared. FIG. 5 shows changes in the coal output ratio from the mill (the ratio of the amount of coal output to the amount of coal fed) over time after the start of coal feeding to the mill. The horizontal axis is dimensionless with the settling time in the example of the present invention as 100%. In the experiment, almost all the product fines discharged from the mill were collected by a bag filter and a cyclone collector.

Since there are variations in the experimental points, in the figure, the characteristics of this embodiment are shown by a solid line, and the characteristics of the conventional example are shown by a broken line.

Coal output from the mill begins after a short delay from the start of coal feeding, and the amount of coal output increases in a state that can be approximated by a roughly first-order lag system. Further, it can be seen that the roller mill according to the present invention produces a faster amount of coal. This is because the adoption of the roller support method of the present invention made it possible to reduce the space in the crushing section, shorten the residence time of particles in the crushing zone, and improve the responsiveness of the mill. Figure 6 shows the coal bed differential pressure ratio within the mill (the ratio of the coal bed differential pressure at startup to the coal bed differential pressure at static stability for each mill, where the coal bed differential pressure is the overall The change in the value obtained by subtracting the pressure loss of only air from the pressure loss is shown, and the trend is the same as the example in FIG. In FIG. 6, the horizontal axis is dimensionless with the settling time in the example of the present invention set as 100%.

That is, in the roller mill according to the embodiment of the present invention, the differential pressure in the coal bed increases faster and shows higher responsiveness as it approaches static stability. In the roller mill of this embodiment, the hold-up of coal in the crushing section is small, that is, the number of particles that remain without being crushed is reduced, and as a result, the differential pressure in the coal bed during static settling is also reduced. Therefore, it is considered that this high responsiveness was exhibited.

In the roller mill of this embodiment, as mentioned above, the pressure loss of the mill is lower than in the conventional example, so the amount of air used can be reduced. Therefore, the coal output conditions of the mill, that is, the C/A (mass flow rate ratio of pulverized coal to primary air) at the pulverized coal injection nozzle of the burner can be made high. This is very advantageous when reducing NOx concentration in exhaust gas without sacrificing combustion efficiency during combustion. Near the burner, the coal concentration increases and the jetting speed of coal particles decreases, making it difficult to ignite.・Flame stability improves.This effect causes
A stable low-air ratio combustion zone is formed at the center of the flame, and reducing products (No-N) generated by high-temperature pyrolysis are
, for conversion) are also actively generated at the same time. In this way, a reduction in nitrogen oxides generated from within the flame is achieved. Figure 7 shows the results of arranging the combustion characteristics based on the relationship between the Noxm degree in the exhaust gas and the unburned content in the ash (both the horizontal and vertical axes are dimensionless with the target value in the conventional example as 100%). . Is there more NOx during combustion using the roller mill of the present invention than when using a conventional roller mill?
It can be seen that the temperature was reduced.

A mill that employs and embodies the roller according to the present invention is not limited to a mill for a pulverized coal-fired boiler or a solid fuel-fired boiler such as petroleum coke, as shown in the embodiments mentioned above, but also a mill for a coal-fired blast furnace injection mill. It can also be applied to fine grinding mills, or as special purposes, mills for fine grinding ceramic raw materials, pigment production, etc.

Particularly in the field of cement, where strict quality control and energy-saving operations have recently been promoted, a vertical mill employing the rollers of the present invention is considered to be particularly effective.

In addition, it can also be applied to iron ore crushing mills, where so-called tower mills have traditionally been used.

[Effects of the Invention] The mill of the present invention is compact, and the roller installation,
It is easy to remove, and even if the particles to be crushed accumulate on the rotary table during operation under high load conditions, they are fed between the rollers and the crushing race so that they do not cause transfer resistance of the rollers. No loss of efficiency.

[Brief explanation of drawings]

Figure 1, Figure 2, Figure 2A, Figure 3, Figure 3A, Figure 3B
The figure is a detailed explanatory diagram of the present invention, Figures 4 to 7 are experimental comparison diagrams of an example mill of the present invention and a conventional mill, and Figures 8 to 11 are
The figure is an explanatory diagram of a conventional mill. 3... Grinding table, 6... Grinding ring, 7...
Grinding roller, 8... Roller shaft, 10... Roller support frame, 10b... Skirt-like weir body, 10c
...Horizontal pressure receiving part of roller support frame, 10d...
・Lola bracket, 13...lower pressure frame, 14
...Spring, 15...Pressure frame, 17...
・Mill housing, 26...Crushing race. Representative Babcock Hitachi Co., Ltd. Representative Patent Attorney Takeshi Kawakita Long-grained raw material supply pipe (undershoot) Grinding table Table shaft Table rotating shaft Grinding ring Grinding roller Roller shaft Roller center axis Seal force bar Roller Vivosoto Lower pressurization Frame Nubbling Pressure Frame Tension Rod Mill Housing Oil Seal Air Rotating Classifier Cylindrical Classifier Rotor Rotating Classifying Vane Dashing Ring Product Fine Powder Discharge Duct Product Fine Powder Grinding Race □ Two Rotation Directions orac: Race Diameter 0: Roller Support Frame 2nd A Figure: The hole where the loan goes in. Figure ゐ5゜no1o. Coal feeding load factor (%) Coal feeding start Grinding roller Roller bracket Roller Shaft Roller rotating Seal plate Hage airline Oil line Roller pivot Lower pressure frame Nuplinder Upper pressure frame Load Rotating table Table Rotation center Grinding ring Grinding race Airnu Roto mill housing Drac: Grinding race diameter 103.104 105~ ]07 ]08~ ]O 1] ]2 ]3 Mill housing center line Thalassossing bowl Crushing roller Suppression member Suppression ring Tension Rondo Nozzle ring Center column No. 10 Figure 11

Claims (1)

[Claims] A mill housing that stands upright, a grinding table that rotates within a horizontal plane inside the mill housing, and a grinding race that is provided on the top surface of the table and has a groove surface with an arcuate cross section along the outer periphery of the table.
A plurality of crushing rollers having an arcuate cross section are provided in contact with the grooved surface of the crushing race, a pressure device applies a predetermined pressure to the crushing rollers, and the crushing rollers are arranged on a table at equal intervals. In a vertical roller mill, the roller support frame includes a plurality of brackets that support the rotating shaft of the roller from the mill center axis side, and a roller support frame that supports the roller and transmits the pressure from the pressure device to the roller. 1. A vertical roller mill, which is integrally constructed with a connecting skirt-like weir body, and is characterized in that a horizontal pressure receiving part is provided on the upper part of this integrated structure to receive pressurizing force from a pressurizing device via a roller pivot.