JP5137272B2 - Vertical roller mill - Google Patents

Description

  The present invention relates to a versatile vertical roller mill suitable for fine pulverization of coal and petroleum coke, pulverization of raw materials in which pulverized fine powder such as limestone is likely to adhere to the roller surface.

  Many boilers for power generation still use coal or petroleum coke as fuel. This is because fuel costs are low and the amount of power generation can be easily adjusted. Of course, China and other developing countries rely on coal and petroleum coke for a considerable portion of the amount of power generation. . However, coal and petroleum coke have the major drawback of high carbon dioxide emissions.

  Japan pledged to reduce 25% of carbon dioxide emissions in 1990 by 2020 worldwide. This commitment is an extremely difficult figure that the public and industry have to bear a great responsibility to achieve, but after making a commitment, we must strive toward that goal. To that end, it is very important to reduce the amount of carbon dioxide generated from coal and petroleum coke used in power generation boilers.

  In other words, the use of coal or petroleum coke as a fuel for power generation has an extremely large amount of carbon dioxide emissions, and therefore, the carbon dioxide emissions have been evaluated as the source of various evils. However, it is impossible for Japan without resources to immediately stop the use of coal among fossil fuels. At least until nuclear power generation or clean alternative energy is prepared, its use cannot be stopped because of its economic efficiency, convenience, reserves, and difficulty in depletion.

  Therefore, how to control the amount of carbon dioxide emitted from these fossil fuels will be an important technical issue in the future, and the development of new technologies to solve this issue is an extremely important theme. Become. As part of this, it is worth considering the coal supplied to the boiler and the pulverization of petroleum coke at the stage of pulverization, thereby reducing the amount of carbon dioxide generated. Of course, although the reduction effect achieved by one crushing mill is insignificant, there are an infinite number of units used worldwide, and when combined, this can contribute to a huge reduction in carbon dioxide emissions. Is possible. In advanced countries, especially Japan, which is a technology-based country, it is considered that its mission and responsibility are to take the initiative in pulverization with a grinding mill.

  The present inventor has paid attention to this from an early stage and worked on measures for pulverization in a pulverizing mill, and has also achieved great results. A typical technique is the improvement of the roller crushing surface shape described in Patent Documents 1 and 2, particularly the development of a slit roller. The slit roller is formed by forming slit grooves in the center line direction (a direction perpendicular to the roller circumferential direction) on the outer circumferential surface, which is a crushing surface of the grinding roller, at predetermined intervals in the circumferential direction. As a result, in the vertical roller mill field, compared to existing mills, the biting property of the pulverized material has been improved and the fine powder rate has been improved.

  In other words, in the case of a thermal power plant, the average coal pulverization particle size is 200 mesh passing and 75% average, but this pulverization particle size is further reduced, and 200 mesh passing and 75% over fine powder is larger than the conventional mill. By making it possible to collect it, it has succeeded in improving the combustion efficiency in the boiler and, as a result, enabling complete combustion and contributing to the reduction of carbon dioxide emissions.

  In addition, pig iron is produced in a blast furnace at a smelter, but a large amount of coke reducing gas is generated and used to reduce and dissolve iron ore, but because coke is produced from expensive caking coal, it is very In order to reduce the amount used, pulverized coal that is cheaper than the blast furnace tuyere is blown to reduce coke consumption and reduce pig iron production costs.

  Many of the slit rollers developed by the present inventor have been adopted in blast furnace pulverized coal blowing equipment, which greatly contributes to cost reduction. At the Sakai Works, the cost reduction effect is said to reach 600 to 700 million yen per year. When the production amount of fine powder of 200 mesh or less including 200 mesh is increased by about 20% or more compared to the conventional mill, the blast furnace combustion efficiency is increased, which contributes to further reduction of coke consumption. In other words, the reduction of coke consumption leads to the reduction of carbon dioxide generated during coke production, and makes a great contribution to the reduction.

  A vertical roller mill is often used as a coal pulverizer in a power generation boiler. The vertical roller mill is composed of one drive table that rotates horizontally, and a plurality of grinding rollers arranged on the drive table so as to surround the rotation center line. The coal supplied to is conveyed outward by centrifugal force and is crushed one after another by being bitten between the roller and the table. The pulverized coal is air-carryed upward by a carrier air-flow and classified by a classifier, the coal having the required particle size is captured and conveyed to the subsequent stage, and the coal having a larger particle size is returned to the inside of the mill again.

  The vertical roller mill for coal pulverization is a Roche mill type in which the shape of the pulverization roller is a trapezoidal shape, and the circular crushing part on the upper surface of the rotary table is a horizontal surface, and the outer peripheral surface of the pulverization roller is within the plane perpendicular to the rotation direction. It is roughly classified into a tire type type which is curved in a convex direction to the side and has an annular groove having an arc cross section in which the outer peripheral surface of the grinding roller is fitted on the upper surface of the rotary table. The tire-type crushing roller further has a ratio of the maximum diameter D to the radius of curvature R in a plane perpendicular to the rotation direction of the tire crushing surface of 4.3 or more, and a flat type tire less than 4.3. Be divided. When this inventor investigated D / R of the tire type | mold roller marketed, average D / R of the former convex type tire is 4.5-5.0, and the average of the latter flat type tire Since the typical D / R was in the range of 3.8 to 4.1, D / R = 4.3 is appropriate as a branch point between the two.

  Apart from slit rollers, the inventor has also continued research on screw rollers. A screw roller is provided with a plurality of screw grooves (spiral grooves) inclined with respect to the roller circumferential direction in parallel on the roller outer peripheral surface (Patent Documents 3 and 4). The slit groove in the direction parallel to the roller shaft (perpendicular to the circumferential direction of the roller) is excellent in raw material biting performance, but has an extremely high ability to scatter to the outside. On the other hand, in the circumferential groove in the direction perpendicular to the roller shaft (roller circumferential direction), the pulverized raw material cannot be bitten. On the other hand, if the slit groove is screw-shaped and formed in the direction in which the pulverized raw material is scraped back to the center side of the table, the insertion amount of the pulverized raw material increases in the pulverization space formed between the roller and the table, Even in the case of the same roller clearance, the contact friction force with the roller is increased, and it can be expected that mill vibration is effectively prevented during low load operation in a thermal power plant.

However, there is a problem common to both the pulverizing roller in which the slit groove for improving the biting property is formed on the entire crushing surface of the vertical pulverizing roller and the pulverizing roller in which the screw groove having excellent pulverizing raw material transportability is formed. This has become clear from many years of experience and experimental studies by the present inventors.

  That is, in the case of a roller with a slit groove and a roller with a screw groove, there is a situation in which the high value of the added value of the ground raw material having high hardness cannot be fully utilized due to excessive wear. The inventor has continuously searched for a solution. Even if this can be solved, the crushing roller with slit groove and crushing roller with screw groove can be used for all materials of high hardness material, high moisture content material, adhesion and adhesive material except for any crushing material, i.e. ignitable material. However, it is possible to achieve a finished shape of a vertical mill roller having a performance capable of exerting the true value of the grindability.

  Therefore, the present inventor decided to go back to the basics, elucidate the true function and action of the existing crushing roller, and fundamentally develop a new crushing surface. For this purpose, the present inventor first investigated the problems common to the slit grooved roller and the screw grooved roller. As a result, the following two problems with respect to the roller circumferential direction and the roller axial direction emerged.

  The first problem is a problem related to the wear form in the roller circumferential direction (rotation direction) of the crushing roller crushing surface. The details are as follows. When grinding hard materials, the slit groove has a major drawback that it tends to cause premature wear. That is, conventionally, slit grooves are formed on the entire roller crushing surface. In such a crushing roller, when a soft raw material is crushed, the wear of the soft ribs forming the slit grooves gradually proceeds, and the slit grooves start to be formed, and the wear-resistant hardened metal interposed between the soft ribs is the gear. Appear in the form. However, since the pulverized raw material is soft, the edges of the hardened metal that has emerged remain almost at right angles without being worn, and as a result, they show excellent biting and wear resistance, and they have a long period of time. Maintains effects and longevity and gives satisfactory use results. In the case of pulverizing such a soft raw material, even if slit grooves and screw grooves were formed on the entire surface of the roller crushing surface, the effect could be exhibited.

  For example, in the case of coal pulverization with an HGI of 45 or more or in slag pulverization of blast furnace slag, it was possible to exert a remarkable effect in improving productivity and extending the life.

  On the other hand, when grinding very hard grinding raw materials, the soft ribs forming the slit grooves will wear out early, and the wear resistant metal will appear like a gear in a short period of time, and the corner of the wear resistant metal will be While hard materials are efficiently ground to improve grinding efficiency, the hard gears are subject to extreme wear and the sharp gear shape changes to a chevron shape at an early stage. Phenomenon that forced to replace in a short period of time caused by excessive wear. The wear speed is extremely short compared with the existing circumferentially wound fill roller.

  For example, in the case of a cement raw material crushing roller used in a cement factory, the production amount per unit time has improved by about 20% or more, but the life has become less than half of the life of the existing build-up roller. The wear rate also increased dramatically when grinding very hard silica stones and ceramics, unweathered blast furnace slag, and low grade coal containing a large amount of ash.

From these phenomena, the present inventor found that the service life of rollers with slit grooves and rollers with screw grooves is not only dependent on the wear resistance of the wear-resistant metal employed but also greatly on the shape of the crushing surface to be crushed. Judged to be dependent. As a result of numerical analysis, as a result of the analysis of the hardened metal with the same wear resistance, the edge of the gear shape in the slit grooved roller compared to the case of the smooth crushing surface circumferentially wound and piled up by the tire type roller. It has been found that the contact pressure increases about three times.

  In general, it is said that the wear is proportional to the power of the surface pressure received by the wear surface, so that it is estimated that the wear received by the edge receives 2 to 4 times or more of the surface pressure compared to the smooth surface. Therefore, even when pulverizing hard pulverized raw materials, a new crushing surface that develops high-efficiency crushing of slit grooves and can ensure the same life as a smooth crushing surface even when using the same wear-resistant metal is developed. The need is urgently needed.

  The second problem is a problem relating to the wear form of the crushing roller crushing surface in the roller axial direction. That is, when the wear shape of the crushing roller is observed in detail, a deep wear groove is formed on the large diameter side and wear is generated on the small diameter side with respect to the trapezoidal roller crushing surface when the crushing efficiency is reduced and replaced. The shape that has not been shown. A convex roller (D / R = 5) with a tire type roller having a small curvature, like a trapezoid type roller, tends to generate maximum wear mainly on the large diameter side, and a flat type roller with a tire type roller having a large curvature. With regard to (D / R = 4), there was a tendency for maximum wear to occur on the small diameter side.

The crushing part that generates the maximum wear is the part that contributes most to the crushing surface among all the crushing surfaces of the rollers, and is the area where the crushing work is maximum, and it is determined that fine crushing is mainly performed in this area. it can. Naturally, the other crushing surfaces are also finely pulverized, but rather than finely pulverizing because of less wear, the crushed raw material supplied to the center of the rotary table is sent to the main crushing surface with centrifugal force. It was assumed that it was a transfer surface that played a role. This transfer crushing surface is a part where the raw material is first bitten and has a major purpose of crushing the raw material having a large particle size. However, if the material transferability on this transfer crushing surface is promoted by any means, the fine powder is pulverized. It was speculated that the sex could be greatly improved. At the stage of developing the slit groove, the emphasis was mainly on biting, but in crushing adhesive substances such as limestone, we developed a screw groove that is effective for effective crushing without causing adhesion to the rollers. Since then, I have noticed the importance of material transferability on the crushing surface.

Theoretically, the roller crushing surface was thought to be composed of two crushing surfaces, namely, a main crushing surface in a region where fine crushing was performed and a transfer surface in a region where raw materials were fed into the main crushing surface . By clarifying the division of roles for each individual crushing surface , the raw material can be reliably and reliably transferred to the main crushing surface regardless of the type of raw material. This reduces the waste of wasted energy required for crushing, enables the design of crushing surfaces that can perform crushing operations more efficiently, and also serves as a countermeasure against wear on the main crushing surface. We were able to recognize it based on experience and trial and error.

  Thus, one of the important roles of the crushing surface is the transportability of the raw material. It turns out that the current smooth surface roller does not actually play its role. When crushing a hard crushing raw material or a crushing raw material with a lot of moisture, the crushing surface is smooth, so it is inferior in biting and transportability, and the roller generates slip and generates a large vibration in the crusher itself. As a result, the production of fine powder decreases. If excessive surface pressure is applied to the roller in order to suppress the slip and vibration of the roller, the shaft current of the mill increases and a large power loss occurs.

Japanese Patent No. 1618574 Japanese Patent No. 2863768 Japanese Utility Model Publication Sho 63-11939 International Publication WO2009 / 157335 Specification

  An object of the present invention is to solve the problems in the circumferential direction and the axial direction of the crushing surface of the crushing roller and to provide a high-performance and economical vertical roller mill capable of maintaining an excellent crushing capacity for a long period of time. .

Theoretically, the crushing surface that plays the most important role in the production of fine powder is the main crushing surface. In order to make the fine powder crushing action more effective, if there are no extra grooves such as slit grooves and screw grooves on the main crushing surface, the effective crushing area can be increased and the fine powder crushing efficiency can be improved. It is self-explanatory. If the main crushing surface can be changed to a smooth surface, naturally, the unique phenomenon of severe wear on the gear-shaped hard metal edge disappears, and a long life is achieved in the same way as the smooth surface, and the amount of fine powder produced If you take into account the increase, you can get both. This is the first step in providing a complete solution.

However, the effect of improving the pulverization amount of the fine powder cannot be obtained only by changing the main crushing surface to a smooth surface. If the pulverized raw material is not stably supplied continuously to the main crushing surface , it becomes difficult to improve the productivity of fine powder. Therefore, it is necessary to complement the crushing surface other than the main crushing surface, and the transporting ability to reliably feed any main material to the main crushing surface is required as the complementing operation.

When a large amount of raw material is fed to the crushing surface , naturally the raw material layer thickness is increased in the crushing chamber formed between the roller and the table, the grinding action between the raw materials becomes remarkable, and the productivity of fine powder is improved. When the load surface pressure on the roller is constant, the layer thickness increases as the amount of biting increases, and as a result, the axial current of the mill increases due to the increase in work amount, but the pulverization amount of fine powder also increases. In comparison with the power intensity obtained by dividing the amount of power used by the amount of fine powder sampled to be obtained, the larger the denominator, the lower the power intensity, contributing to energy saving. Speaking of the correlation between the roller crushing area and the power consumption, as the roller surface area increases, the frictional resistance increases and the power consumption also tends to increase, so the main crushing surface is a 100% smooth surface. However, since the contact area cannot be reduced, the transfer surface is not mainly pulverized, so it is possible to reduce the contact area by forming a groove.

In the vertical roller mill, the crushing roller is divided into two roles: a main crushing surface that mainly crushes fine powder on one crushing surface, and a crushing surface that transfers pulverized raw material to the main crushing surface. It becomes very easy to understand. As an example, consider a trapezoidal roller. The main crushing surface that mainly pulverizes the fine powder is located on the large diameter side, and the small diameter side can be clearly described as a crushing surface for transferring the raw material to the large diameter side, divided into two clearly. Originally, the crushing action is not clearly divided in this way. For vertical roller mills, the pulverized raw material is supplied from the center of the mill and is driven out of the table by the centrifugal force generated by the table rotation. As the process proceeds, the pulverization progresses in stages from coarse grains to fine grains. Of course, fine pulverization is also performed on the small diameter side, but the frequency is very high on the large diameter side, and coarse particles are mainly bitten on the small diameter side, and the large diameter side is gradually pulverized into fine particles. The fine powder is pulverized mainly in the main pulverization zone. As evidence, the crushing surface on the large diameter side, which has the most pulverizing action, reveals an extreme wear region, and the actual progress is that the progress of the wear is not observed on the small diameter side.

From these facts and verifications, the present inventor found that the main crushing surface that mainly pulverizes the fine powder in one roller crushing surface and the raw material transfer surface that feeds the raw material reliably and stably to the main crushing surface coexist. It was theoretically and empirically derived that an effective pulverizing effect could not be obtained if either one was missing.

  In raw material crushing with low adhesion, slit grooves that are parallel to the roller shaft or have an angle of up to 45 degrees are effective for improving biting properties. The screw groove with an angle of 45 degrees or more and 85 degree which improves the transportability is effective, and the improvement of the grindability for all grinding raw materials is established by including two kinds of grooves Was verified by grinding experiments.

The vertical roller mill of the present invention is an epoch-making pulverizer developed on the basis of such knowledge, and has a plurality of pulverizing rollers arranged on the rotary table so as to surround the rotation center line of the rotary table. In the type roller mill, the crushing surface of the crushing roller is composed of a main crushing surface that mainly performs fine crushing and a crushing surface other than the main crushing surface, the main crushing surface is a smooth surface, and a crushing surface other than the main crushing surface has a roller A slit groove that is perpendicular to the circumferential direction or inclined at an angle of more than 45 ° or a screw groove that is inclined at an angle of 45 ° or less with respect to the circumferential direction of the roller is formed, and an annular shape that faces the grinding roller in the rotary table The crushing part is a saddle type roller having a crushing roller with a hybrid crushing surface structure, in which the entire surface is a smooth crushing surface or a slit groove perpendicular to the rotation direction is formed on the entire surface. Lamil.

Judging from the function of the crushing surface of the crushing roller, the main crushing surface is constituted by a smooth surface to improve the amount of fine powder crushing and to reduce wear. For crushing surfaces other than the main crushing surface , if there is little adhesion to the crushing raw material, it is a slit groove with a large angle with respect to the roller circumferential direction to improve the biting property to the crushing surface, or the roller circumference to improve the transferability A screw groove having an angle close to the direction is formed. When the pulverized raw material is an adhesive substance, a screw groove that is inclined at an angle of 45 ° to 85 ° with respect to the roller shaft (5 ° to 45 ° with respect to the roller circumferential direction) is limitedly formed. . The reason for this is that when the groove angle is parallel to the roller axis or less than 45 degrees, the biting property is exerted and adhesion or transfer occurs on the roller surface, making the pulverization operation difficult. A groove angle that exhibits transportability is desirable, specifically, 45 to 85 degrees, and particularly an average angle of 60 to 70 degrees is desirable as the screw groove angle.

As a method of actually forming the main crushing surface into a smooth surface, the crushing surface of the trapezoidal roller is flat in the roller axis direction, so the main crushing surface and the transfer surface can be clearly divided. The main crushing surface of a flat roller having a large tire R exists on the small diameter side, and a convex roller having a small tire R with a tire type roller tends to have a main crushing surface on the tire center side (large diameter side). is there. However, regarding the tire type roller, the main crushing surface exists in a curved surface that is curved in the roller axial direction, so that it is difficult to work the main crushing surface into a flat surface as compared with the trapezoidal roller.

Therefore, in the case of a tire-type roller, in the region corresponding to the main crushing surface , the depth of the slit groove is made shallower than the other parts, so that the shallow groove is filled with the pulverized raw material to form a smooth surface. The groove area itself is designed by adding to the effective crushing area, or slit grooves are formed on the entire crushing surface in advance, and then the slit groove corresponding to the area of the main crushing surface is welded. There is a method of forming a smooth surface by burying with a build-up. This technique can be applied to all shapes of grinding rollers.

The vertical roller mill of the present invention generates extreme wear peculiar to slit grooves by limiting the main crushing surface of the grinding roller that receives the most wear to a smooth surface based on a new crushing theory even in the world. Can be improved to at least the same level as the wear of the smooth surface, and the effective crushing area can be made 100%, which can contribute to the improvement of the production amount of fine powder.

  Regarding the power consumption of the crusher, it is possible to reduce the wasteful power consumption by reducing the surface area of the material transfer surface and reducing the contact area compared to the smooth surface roller by sharing the function of the crushing surface. It is.

  Establishing a complete form of crushing surface technology, including two forms of slit grooves and screw grooves, is one ultimate goal for the inventor who has continued research on the crushing surface shape for many years. However, we have succeeded in developing a finished shape with a crushing surface shape that brings about even better operational effects not seen in the practical world, especially by further enhancing the operational effects of screw grooves. The result is the above-mentioned breakthrough surface form.

The crushing roller in the vertical roller mill of the present invention is a front view showing a trapezoidal roller in comparison with a conventional mill roller. (A) shows a conventional mill roller, (b) shows the present mill roller. The front view which showed the crushing roller in the vertical roller mill of this invention compared with the conventional mill roller about another trapezoid type | mold roller, (a) shows a conventional mill roller, (b) shows this invention mill roller. The front view which showed the grinding roller in the vertical roller mill of this invention compared with the conventional mill roller about the tire convex type roller, (a) shows a conventional mill roller, (b) shows this invention mill roller. The front side which showed the grinding roller in the vertical roller mill of this invention compared with the conventional mill roller about another tire convex roller, (a) shows a conventional mill roller, (b) shows this invention mill roller. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a grinding roller in a vertical roller mill of the present invention in comparison with a conventional mill roller with respect to a flat tire type roller, where (a) shows a conventional mill roller and (b) shows a present invention mill roller. It is a block diagram of the experimental small crusher. It is a vertical side view which shows a table groove | channel shape.

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

  Each of the vertical mill rollers shown in FIGS. 1 to 5 is a crushing roller used in the vertical roller mill.

  The vertical mill roller shown in FIG. 1 is a trapezoidal roller 10 used in a vertical roller mill called a Roche mill. A trapezoidal roller 10 shown in FIG. 1A is a conventional mill roller (hereinafter simply referred to as a conventional roller), and a plurality of screw grooves 11A are formed on the entire outer peripheral surface 12 at equal intervals in the roller axial direction. The inclination direction of the screw groove 11A is a raw material discharge direction in which the pulverized raw material is positively transferred to the outer peripheral side as it rotates, and the inclination angle is 67.5 ° represented by an inclination angle θ with respect to the roller axis here. The inclination angle with respect to the roller circumferential direction is 22.5 °.

  On the other hand, the trapezoidal roller 10 shown in FIG. 1B is a mill roller of the present invention in which the outer peripheral surface 12 is roughly divided into a main crushing surface 12A having a larger diameter side and other portions (hereinafter simply referred to as the present invention roller). It is said). The main crushing surface 12A has a smooth surface. In portions other than the main crushing surface 12A, a plurality of screw grooves 11A are formed at equal intervals in the roller axis direction. The inclination direction of the screw groove 11A is a raw material discharge direction in which the pulverized raw material is positively transferred to the outer peripheral side as it rotates and is sent to the main crushing surface 12A. The angle is 67.5 °, and the inclination angle with respect to the circumferential direction of the roller is 22.5 °.

  That is, the outer peripheral surface 12 of the trapezoidal roller 10 here is composed of a smooth main crushing surface 12A on the large diameter side and a material transfer surface 12B on the small diameter side and provided with screw grooves 11A in the material discharge direction. is there.

  Here, the main crushing surface 12A is defined as a region in which wear of 2/3 or more of the maximum wear amount of the roller outer peripheral surface 12 occurs, and the axial length of the main crushing surface 12A in the roller, that is, the main crushing surface 12A. The lateral width of the trapezoidal roller is usually about 30 to 40% of the entire width of the roller.

  The vertical mill roller shown in FIG. 2 is a trapezoidal roller 10 used in a vertical roller mill called a Roche mill, similar to the vertical mill roller shown in FIG. The trapezoidal roller 10 shown in FIG. 2A is a conventional roller, and a plurality of slit grooves 11B perpendicular to the circumferential direction of the roller are formed on the entire outer circumferential surface at equal intervals in the circumferential direction of the roller. On the other hand, the trapezoidal roller 10 shown in FIG. 2B has a main crushing surface 12A whose outer peripheral surface 12 has a large diameter side, and other portions, that is, slit grooves 11B perpendicular to the circumferential direction of a plurality of rollers. Is roughly divided into a material biting surface 12C formed at equal intervals in the roller circumferential direction.

  The vertical mill roller shown in FIG. 3 is a convex roller 20 (D / R = 5) which is a tire type roller and has a small curvature. The tire convex roller 20 shown in FIG. 3A is a conventional roller, and a plurality of screw grooves 21A are formed on the entire outer peripheral surface 22 at equal intervals in the roller axial direction. The inclination direction of the screw groove 21A is a raw material discharge direction in which the pulverized raw material is positively transferred to the outer peripheral side as it rotates, and the inclination angle is 45 °, expressed here as an inclination angle θ with respect to the roller shaft, The inclination angle with respect to the direction is 45 °.

  On the other hand, in the tire convex roller 20 shown in FIG. 3B, the outer peripheral surface 22 has a large diameter side, that is, a smooth main crushing surface 22A at the center, and the screw groove 21A in the material discharge direction is in the roller axial direction. This is a roller of the present invention composed of raw material transfer surfaces 22B and 22B on both sides (small diameter side) formed at intervals. Here, the inclination angle of the screw groove 21A is 45 ° represented by the inclination angle θ with respect to the roller axis, and the inclination angle with respect to the roller circumferential direction is also 45 °.

  The vertical mill roller shown in FIG. 4 is a tire convex roller 20 (D / R = 5), similar to the vertical mill roller shown in FIG. The trapezoidal roller 10 shown in FIG. 4A is a conventional roller, and the slit groove 21B in the material scraping direction is formed in the circumferential direction of the entire outer peripheral surface 22 contrary to the vertical mill roller shown in FIG. It is formed at equal intervals. On the other hand, in the tire convex roller 20 shown in FIG. 4B, the main crushing surface 22A having a smooth outer peripheral surface 22 and the slit groove 21B in the raw material scraping direction are equally spaced in the roller circumferential direction. It is this invention roller which consists of the raw material transfer surfaces 22B and 22B of the formed both sides (small diameter side). Here, the inclination angle of the screw groove 21A is 45 ° represented by the inclination angle θ with respect to the roller axis, and the inclination angle with respect to the roller circumferential direction is also 45 °.

  The vertical mill roller shown in FIG. 5 is a flat roller 30 (D / R = 4) which is a tire-type roller and has a large curvature. The flat tire roller 30 shown in FIG. 5A is a conventional roller, and a plurality of screw grooves 31A are formed on the entire outer peripheral surface 32 at equal intervals in the roller axial direction. The inclination direction of the screw groove 31A is a direction in which the pulverized raw material is scraped back to the center side with rotation. The angle is 22.5 °.

  On the other hand, in the tire flat roller 30 shown in FIG. 5B, the outer peripheral surface 32 has a small diameter side, that is, smooth main crushing surfaces 32A and 32A on both sides, and the screw groove 31 in the raw material scraping direction has a roller axial direction. This is a roller of the present invention comprising a central material transfer surface 32B formed at regular intervals. Here, the inclination angle of the screw groove 31 is 67.5 ° represented by the inclination angle θ with respect to the roller axis, and 22.5 ° with respect to the roller circumferential direction.

  The feature of the tire-type roller shown in FIGS. 3 to 5 is that it can be used twice in reverse. In particular, since the tire flat roller 30 shown in FIG. 5 is pulverized near the small side diameter, it is generally used twice horizontally. In individual use, crushing is performed by the main crushing surface 32A on one side and a part 32B 'of the raw material transfer surface 32B. The lateral width of the main crushing surface 32A on one side is usually 15 to 20% of the entire width of the roller, and the total width is about 30 to 40% of the same roller width as that of the trapezoidal roller.

  On the other hand, the tire convex roller 20 shown in FIGS. 3 and 4 is often pulverized near the central large diameter, and therefore often cannot be reversed. That is, in individual use, crushing is performed exclusively on the main crushing surface 22A and the raw material transfer surface 22B on one side, and in the case of reversal use, the main crushing surface 22A overlaps, and wear of this part proceeds extremely. This makes it difficult to use the reversal. The horizontal width of the main crushing surface 22A here is usually about 30 to 40% of the entire width of the roller, as with other rollers.

〔Experimental device〕
In order to investigate the effectiveness of the present invention, an experimental small pulverizer similar to a Roche mill having a trapezoidal roller, which is a kind of vertical roller mill, was produced. As shown in FIG. 6, this pulverizer has a structure in which the pulverizing roller 2 faces the outer peripheral surface of the horizontal rotary table 1 as a base member. The crushing roller 2 is a truncated cone shaped roller, and is inclined so that the large diameter side faces the outer peripheral side and the small diameter side faces the central side, and the facing surface with the table 1 is horizontal. Since it was an experimental machine, the number of rollers was one.

  A plurality of screw grooves 7 are provided on the outer peripheral surface of the grinding roller 2. The plurality of screw grooves 7 discharges the pulverized raw material from the center of rotation to the outer peripheral side as it rotates, and sends it to the pulverization chamber formed by the rotary table 1 and the pulverization roller 2.

  In the rotary table 1, the outer peripheral portion facing the crushing roller 2 becomes an annular crushing portion 3, and the annular crushing portion 3 is a test machine, and thus can be attached to and detached from the table body 4. As the crushing part 3, a surface having a smooth surface, a slit groove perpendicular to the rotation direction of the table on the surface, or a groove attached with an angle at which the edge of the right-angle groove with respect to the direction of feeding limestone holds an acute angle of 60 ° -142809 gazette) was prepared. The crushing roller 2 is attached to the support mechanism 5 so as to be rotatable and movable up and down so that the clearance with the crushing unit 3 can be arbitrarily adjusted. In order to apply a predetermined pressure to the pulverized raw material, the pulverizing roller 2 is urged by a spring in a direction to be pressed against the crushing part 3.

  As the rotary table 1 rotates, the rotary table 1 and the crushing roller 2 perform a relative turning motion. In this experiment, in order to confirm the pulverization performance of the roller itself, no classification device using air of the pulverized raw material is installed. Therefore, since the crushed raw material is discharged from the inside of the rotary table to the outside due to the discharge capability of the roller and the centrifugal force of the table rotation, a collection container 8 that can completely collect the discharged limestone is provided outside the rotary table. did.

  The Roche mill compact tester was designed so that a tire type table could be attached by removing the table 4. Naturally, the grinding roller attached to the support mechanism 5 can be replaced with a tire-type grinding roller. It was designed so that all rollers and tables could be tested with a single testing machine. Further details of the testing machine will be described later.

[Crushing raw material]
When the crushing roller was actually used with the crushing surface of the crushing roller divided into the main crushing surface and the raw material transfer surface, the amount of fine powder crushing formed the conventional slit groove and screw groove on the whole crushing surface It was clarified using a small crushing tester whether or not it increased compared with the case. As the pulverized raw materials used in the confirmation experiment, two types of coal were selected: 1) limestone having high adhesion and adhesion, and 2) coal having less adhesion and adhesion than limestone.

[Crushing experiment of limestone]
When pulverizing limestone, screw grooves were formed to prevent the limestone from adhering to the roller surface and transferring. As the screw groove, an intermediate 67.5 degrees was selected from an angle range of 45 degrees or more and 85 degrees or less with respect to the roller shaft. It has already been found that when slit grooves up to 45 degrees are used for limestone crushing, the slit grooves have excellent ability to scrape the raw material, resulting in adhesion and transfer of limestone on the roller surface, making the grinding operation difficult. Therefore, it was decided to form a screw groove having an angle of 45 degrees or more. In particular, the screw groove of 45 degrees or more reduces the performance of scraping the raw material, and is excellent in transportability for feeding the raw material. As the angle increases, the transportability is further improved, and the transfer and adhesion of limestone to the roller surface is improved. There is a property to reduce. In particular, 67.5 degrees with a large oblique gradient was assumed to be the most excellent inclination angle.

Two types of roller shapes were selected for the experiment, the trapezoidal roller shown in FIG. 1 and the flat tire roller (D / R = 4) shown in FIG. Regarding the groove, when the screw groove is formed on the entire surface of the roller crushing surface (FIGS. 1A and 5A), and when the main crushing surface is a smooth surface and the screw groove is formed in the remaining portion [ 1 (b) and 5 (b)] were selected. For each roller, the difference between the amount of finely pulverized 200 mesh and the amount of power consumption of the pulverization tester was measured, and the effectiveness of both crushing surfaces was compared by comparing the power intensity.

  The slit groove shape of the rotary table employed in this comparative test is shown in FIGS. This groove shape is one of the table crushing surface shapes suitable for limestone crushing presented in Japanese Patent Application Laid-Open No. 2009-142809. The dimensions and grinding conditions of the trapezoidal roller and the flat tire roller are summarized below.

Roller dimensions:
Trapezoidal roller Large diameter: 200mm, Small diameter: 170mm,
Width 57mm
Tire flat roller (D / R = 4)
Large diameter: 200 mm, tire R: 50 mm,
Width 74mm

Table outer diameter:
For trapezoidal rollers Outer diameter: 410mm, Inner diameter: 280mm,
For tire flat roller outer diameter: 420 mm, inner diameter: 220 mm,
Groove R: 60mm

Peripheral speed: 30 RPM (left rotation)
Roller pressure: 23.5kg
Clearance between roller and table: 0mm
Test time: 30 minutes Limestone supply: +/- 1500 g / 30 minutes Limestone supply method: Continuous supply screw feeder system temperature, humidity: 12-18 ° C, 60-89%

Limestone used in the test Particle size: 1-3mm
Particle size distribution (measured value after drying for 30 minutes)
More than 10 mesh 46.0g
More than 16 mesh 44.0g
More than 30 mesh 9.0g
60 mesh or more Tr
P 0.5g

  In the experimental pulverizer, the amount of limestone discharged to the outer periphery of the table, the remaining amount of limestone in the table, and the weight ratio of particles passing through 200 mesh and −235 mesh under the total pulverization amount were investigated. In this experiment, for convenience, only one crushing roller is used for crushing. In the actual machine, 2 to 4 rollers are used, and a classification device for collecting fine powder is installed. Although the numerical value is different from the pulverization amount, since the same testing machine is used, the obtained tendency is highly reliable.

  In the particle size measurement, after the 30-minute grinding test was completed, the entire amount of limestone discharged from the table to the collector 8 was accurately collected, and the limestone remaining in the table was also collected in the same manner. After measuring the weight of each collected limestone, three samples were collected for particle size measurement from arbitrary locations of the collected limestone. In order to ensure accuracy, the average value of three data was adopted for the particle size measurement results.

  The power consumption of a small crushing tester was measured. The power measuring instrument used is “Clamp on Power HiTester 3168” manufactured by Hioki Electric Co., Ltd. The power consumption is an average value of numerical values measured in units of one second. In this experiment, an average value for 30 minutes was measured. This small experimental pulverizer has a three-phase 220V power consumption of 750 W / H. The reason for measuring the power consumption is as follows. Limestone was fed to the mill with a screw feeder, but often caused clogging, resulting in variable amounts for quantitative cutting. If there is a difference in the supply amount, it is impossible to obtain an accurate result by simply comparing the pulverized amount of 200 mesh under powder. Therefore, the amount of power consumed in each test pulverization was measured, and the fine powder of 200 mesh under obtained at that time The accuracy was maintained by comparing by the power unit divided by the amount of grinding.

  The total pulverization amount for 200 mesh under is measured within 30 minutes of the pulverization test time, and the power consumption (Wh) required for the pulverization is measured. Using the numerical value divided by the unit of electric power, various combinations of roller and table crushing surfaces were obtained and compared.

[Comparative test results]
Table 1 shows the results when the grinding roller is a trapezoidal roller.

Test number (1) is the roller (Fig. 1 (a) having an effective crushing area of 85%) in which screw grooves in the discharge direction of 67.5 degrees are formed on the entire crushing surface, and a table with a right angle slit at an angle of 60 degrees and an acute edge groove. Is a combination. Test number (2) is that the main crushing surface on the large diameter side is a smooth surface, and the roller (effective crushing area 89%) in FIG. 1B in which screw grooves are provided only on the other crushing surface on the small diameter side is used. Is the same as test number (1). Of the total width 57 mm of the test roller, the width of the smooth surface as the main crushing surface was set to 20 mm (about 35% of the total width). The remaining part was screw grooves. The 200 mesh under amount and the power unit of both were compared.

Table 1 shows the 200 mesh under amount when the screw groove is formed on the entire crushing surface of the trapezoidal roller (1) and when the main crushing surface is a smooth surface and the other crushing surface is a screw groove (2). And comparison of power intensity (roller pressure is constant 23.5 kg).

In (1), the amount of limestone input increased more than in (2), indicating that the active power consumption was somewhat increasing. However, although the amount of finely pulverized 200-mesh powder was slight, (2) increased. Therefore, when compared in terms of power consumption, (2) achieved about 7% energy saving compared to (1). Although there is no extreme difference, it is better to divide the roller crushing surface of (2) into two types, the main crushing part and the transfer part, which is 200 mesh under compared to the case where screw grooves are formed on the whole crushing surface. It was found that the amount of fine powder pulverization improved and the electric power consumption rate tended to decrease.

Table 2 shows the results when the grinding roller is a flat tire roller (D / R = 4). The reason for selecting the flat roller is as follows. The main crushing surface of this roller exists on the small diameter side, and if compared at the same table rotation speed, the amount of pulverization per hour is smaller than that of the convex roller, and the amount of fine powder is also reduced. Therefore, it was considered that the credibility of the present invention would be enhanced if there was a difference under the circumstances where the amount of fine powder was small. In addition, it was one of the reasons that the formation of the crushing surface was easy from here, where the small diameter side became the main crushing surface .

Test number (1) is a table (Fig. 5A) in which screw grooves are attached in the scraping direction at an angle of 67.5 degrees on the entire crushing surface, and a table having a right angle slit oblique acute angle groove. Is a combination. Test number (2) is a roller (Fig. 5B) in which a smooth surface having the same width is formed on the small-diameter surfaces on both sides and a screw groove in a scraping direction of 67.5 degrees is formed on the inner surface (effective crushing area 92%). ) Is used in the same combination as test number (1). In test number (2), the smooth surface as the main crushing surface out of the roller total width of 74 mm was set to 25 mm width (12.5 mm width + 12.5 mm width, about 34% of the total width).

Table 2 shows the case where a screw groove of 67.5 degrees is formed on the entire crushing surface of the flat tire roller (D / R = 4), and the smooth surface that is the main crushing surface of the roller is arranged on the left and right sides of the small diameter side. This is a comparison of the 200 mesh under amount and the power consumption rate with the case where a screw groove of 67.5 degrees is formed in the center. The screw groove is formed in a direction to scrape the raw material back to the inside of the table.

  Compared to the case where screw grooves are formed on the entire crushing surface of test number (1), the crushing amount is improved by about 12% when the main crushing surface of test number (2) is smooth, and the power consumption is about 15%. % Reduction. Compared to the trapezoidal roller, the flat tire roller showed excellent results in both fine powder pulverization and power consumption. The reason is considered as follows.

In the trapezoidal roller, crushing is performed between the table and the surface of the table. For materials with high adhesion and adhesion, such as limestone, adhesion to the roller and table surfaces is further promoted and formed between the roller and the table. As a result, the difference in the shape of the crushed surface did not clearly appear as the difference in the amount of pulverized fine powder. On the other hand, the tire type roller, which is line crushing and has a good pulverized raw material, has less adhesion than the trapezoidal type roller, and the difference in the crushing surface appeared as a difference in the fine grinding amount. Regarding limestone crushing, which tends to cause adhesion and adhesion, if the main crushing surface is made smooth with both the trapezoidal roller and the tire-type flat roller, a slight increase in the amount of fine powder is observed, and about 7 for the trapezoidal roller. %, About 15% reduction in electric power consumption was recognized with the tire-type flat roller.

When pulverizing limestone with a vertical roller mill, it is very difficult to improve the pulverization amount of 200-mesh under powder. The reason is as follows. Limestone tends to adhere to and adhere to the grinding roller. As a result, the gap between the roller and the table necessary for grinding becomes small, and the amount of fine powder is difficult to improve by reducing the amount of biting into the gap. Furthermore, the finer the limestone, the easier it is to re-adhere, and the particles become larger and less likely to become finer. Regarding such adhesive substances, it should be noted that when the main crushing surface became smooth, the amount of fine powder pulverized increased, and the amount of fine powder collected increased explosively for raw materials with low adhesion. I was able to expect.

[Coal crushing experiment]
A coal pulverization experiment was conducted in the same manner as limestone for three types of trapezoidal rollers, tire convex rollers (D / R = 5), and tire flat rollers (D / R = 4). The grinding conditions are summarized below.

Coal used: Steel mill raw coal particle size range -G-: 7 mm x 7 mm ≥ G ≥ 0.5 mm x 0.5 mm
Initial particle size distribution:
20g or more 40g
More than 60 mesh 34g
120g or more 3g
13 mesh over 200 mesh
235 mesh or more 2g
P 9g
5% moisture
Roller clearance: 0mm
Roller surface pressure: 23.5Kg
Table rotation speed: 60 RPM
Coal supply amount: 2,530 to 2,850 g / 30 minutes Coal supply method: Screw feeder continuous supply system Test temperature and humidity: 18 to 34 ° C., 62 to 78%

  The dimensions of the trapezoid type roller and the flat tire type roller are described in the section of limestone, and are omitted here. Only the dimensional details of the tire convex grinding roller (D / R = 5) are shown below.

Roller dimensions (D / R = 5)
Tire diameter: 200mm
Tire R: 40mm
Tire width: 66mm

Rotary table dimensions Outer diameter: 410mm
Inner diameter: 230mm
Groove R: 50mm

  Table 3 shows a comparison of the amount of 200 mesh under and the electric power unit by the difference in the crushing surface in the trapezoidal roller (roller pressure is constant 23.5 kg). All tables combined with trapezoidal rollers are smooth surface tables.

Test number 1. Smooth surface roller test number 2. 67.5 degree screw groove in the direction to discharge the raw material on the entire crushing surface
Formation [FIG. 1 (a)]
Test number 3. The main crushing surface is smooth and the rest is 67.5 degrees screw
Groove is formed [FIG. 1 (b)]
Test number 4. Right-angle slit grooves are formed on the entire crushing surface [Fig. 2 (a)]
Test number 5. The main crushing surface is smooth and the rest forms right-angle slit grooves
[Fig. 2 (b)]

Table 4 shows a comparison of the 200 mesh under amount and the electric power unit (roller pressure is constant 23.5 kg) due to the difference in the crushing surface of the tire convex roller (D / R = 5). All the tables combined with the tire convex roller are smooth surface tables. The smooth surface as the main crushing surface was set to 23 mm width (35% of the total width) out of the 66 mm roller total width of the tire convex roller.

Test number 1. Smooth surface roller test number 2. Diagonal 45 degree grooves in the direction of discharging the raw material are formed on the entire fractured surface
[Fig. 3 (a)]
Test number 3. The main crushing surface in the center is a smooth surface, and the remaining 45 degrees oblique to the discharge direction
Groove is formed [FIG. 3 (b)]
Test number 4. The main crushing surface in the center is a smooth surface, and the rest is slanted in the scraping direction.
45 degree groove formation (FIG. 4B)

  Table 5 shows a comparison of the amount of 200 mesh under and the electric power unit (roller pressure is constant 23.5 kg) due to the difference in crushing surface in the flat tire type (D / R = 4). All tables combined with the tire flat roller are smooth surface tables.

Test number 1. Smooth surface roller test number 2. 67.5 degree screw groove in the direction of scraping the raw material over the entire crushing surface
Formation [FIG. 5 (a)]
Test number 3. The main crushing surface on both sides of the small diameter side is smooth, and the remaining central crushing surface is fed with raw materials.
Forms a 67.5 degree screw groove in the direction of scraping [FIG. 5 (b)]

As for coal pulverization, the amount of fine powder pulverized by 200 mesh under markedly increased by making the main crushing surface smooth with the three types of rollers: trapezoidal roller, tire convex type, and tire flat type. The basic unit of electric power indicating the amount of energy required for crushing also showed a minimum value by making the main crushing surface smooth. If the main crushing surface is made smooth, it is effective to use any of the right angle slit groove, 45 degree oblique slit groove that scrapes the raw material into the remaining crushing surface, and 67.5 degree screw groove that excels in material transferability. Remarkably recognized. It should be noted that even when the right-angle slit groove was attached with a trapezoidal roller, the finely pulverized amount was about the same as that of the 67.5 degree screw groove.

Regarding the trapezoidal roller, the difference in effect between the screw groove excellent in transportability of 67.5 degrees and the right angle slit groove excellent in biting property was examined. When the amount of fine powder pulverized between a trapezoidal roller having a normal smooth surface and a roller having a screw groove of 67.5 degrees in the direction of discharging the raw material was compared, it increased by about 20%. This increase in the pulverization amount of the fine powder was brought about by the somewhat biting ability of the screw groove of 67.5 degrees and the raw material transfer performance which is the main function. When the main crushing surface of the roller was made smooth, the increase in the amount of fine powder was improved by about 9%. That is, the main smooth surface contributed to an increase of about 9%.

In the trapezoidal roller, the amount of fine powder pulverized between a normal smooth surface roller and a roller having right-angle slit grooves parallel to the roller axis formed on the entire crushed surface increased by about 21%. This increase in the pulverization amount of the fine powder was brought about by the biting performance of the right angle slit groove. When the main crushing surface of the roller was made smooth, the increase in the amount of fine powder pulverized was improved by about 7%. That is, the main smooth surface contributed to an increase of about 7%. The reason for the decrease of 2% from the former is presumed that the right angle slit is inferior to the screw groove in terms of transportability.

In conclusion, with regard to the trapezoidal roller, the same fine powder pulverization amount can be obtained by adopting either a right-angle slit groove excellent in biting performance or a 67.5 degree screw groove excellent in raw material transportability. found. Therefore, the right-angle slit groove where the grinding edge directly meshes directly with the grinding raw material should be applied when soft raw material is ground from the viewpoint of wear, and the 67.5 degree screw groove smoothly feeds the raw material to the main grinding surface . Since it is excellent in action, it should be applied when handling a hard material or a material containing a large amount of moisture.

It relates adhere easily limestone and coal pulverization, proved to be the crushing surface of the grinding roller vertical pulverizing rollers can be divided into two types of functions of the transfer surface for feeding the primary crushing surface and material correct, further primary crushing It has been proved that by making the surface smooth, it is possible to reduce wear and further increase the amount of fine powder ground.

  In this embodiment, the slit grooves and screw grooves that give biting performance and transfer performance are mainly taken up, but naturally the same effect can be obtained by using not only grooves but also convex rib shapes. However, in the case of a convex rib, its height is limited and is limited to a range of 5 to 20 mm. This is because the ribs are subjected to severe wear because they are directly opposed to the pulverized raw material. Therefore, since a material having excellent wear resistance is used, if it is too high, it is easily broken by the impact of the raw material.

  The slit grooves, screw grooves, and ridge ribs are basically continuous in the longitudinal direction, but may be formed intermittently in the longitudinal direction, and the intermittent formation is particularly suitable for the ridge ribs.

  By establishing a hypothesis based on theoretical reasoning and supporting the confirmation of its performance through crushing experiments, we have now established a complete form for the crushing surface shape of a vertical mill roller that the present inventors have studied over the past years. .

10 Vertical mill roller (trapezoidal grinding roller)
11A Screw groove 11B Slit groove 12 Outer peripheral surface 12A Main crushing surface 12B Raw material transfer surface 12C Raw material biting surface 20 Vertical mill roller (tire convex grinding roller)
21A, 21B Screw groove 22 Outer peripheral surface 22A Main crushing surface 22B Raw material transfer surface 30 Vertical mill roller (flat tire crushing roller)
31 Screw groove 32 Outer peripheral surface 32A Main crushing surface 32B Raw material transfer surface

Claims (5)

In a vertical roller mill in which a plurality of crushing rollers are arranged on a rotary table so as to surround the rotation center line of the rotary table, the crushing roller is a trapezoidal roller and its roller crushing surface mainly performs fine crushing. It consists of a main crushing surface on the large diameter side and a crushing surface other than the main crushing surface, the main crushing surface is a smooth surface, and the crushing surface other than the main crushing surface is perpendicular to the roller circumferential direction or an angle of more than 45 ° In the meantime, a slit groove that is inclined at 45 ° or a screw groove that is inclined at an angle of 45 ° or less with respect to the circumferential direction of the roller is formed. A vertical roller mill having a crushing roller having a hybrid crushing surface structure, in which slit grooves are formed on the entire surface or formed with slit grooves perpendicular to the rotation direction. 2. The vertical roller mill according to claim 1, wherein the direction of inclination of the screw groove in the crushing roller is a raw material discharge direction in which the pulverized raw material is positively transferred to the outer peripheral side with rotation and is fed to the main crushing surface. .   The vertical roller mill according to claim 1 or 2, wherein the inclination angle of the screw groove is 5 ° or more with respect to the roller circumferential direction. The vertical roller mill according to any one of claims 1 to 3 , wherein the main crushing surface is an area of 30 to 40% of the entire width of the roller. The vertical roller mill according to any one of claims 1 to 4 , wherein a convex rib is formed instead of the slit groove or the screw groove.

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