JPH04702B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a mill for producing slurry. [Prior Art] Conventionally, in this type of slurry manufacturing mill, the mill is divided into a plurality of grinding chambers by a partition wall provided in the longitudinal direction of the mill, and each grinding chamber from the inlet to the outlet of the mill is divided into a plurality of grinding chambers. The solid material and liquid supplied from the mill inlet are each filled with a grinding medium that has a particle size distribution and the average particle size is gradually reduced. It is discharged from the mill outlet and a slurry is produced. FIG. 4 shows a conventional slurry manufacturing mill. 1 indicates a mill, 2 a body of the mill, and 3 a liner provided on the inner wall surface of the body.
4 is the inlet of the mill, and 5 is the outlet of the mill. Partition walls 10 and 6 are provided inside the mill to divide the mill into a grinding chamber 11 on the mill inlet side and a grinding chamber 12 on the mill outlet side. These grinding chambers 11 and 12 are filled with grinding media having different particle size distributions, respectively, and rotate about an axis m. When a solid material and a liquid are supplied from the inlet 4 of the mill at a predetermined supply rate, the solid material is pulverized and becomes fine, and the solid material is pulverized into pieces at a concentration corresponding to the predetermined supply rate. ,6
Pass through the gap (not shown) provided at the mill outlet 5.
A slurry is produced by discharging the slurry. In addition, as another configuration of the partition wall, a scraping plate may be provided inside the partition wall to move the slurry in the grinding chamber to the next grinding chamber. In addition, at this time, along with solid materials and liquids,
A dispersant such as a surfactant is added to improve pulverization. As mentioned above, the grinding chambers 11 and 12 are filled with grinding media having different particle size distributions, respectively.
In order to increase the pulverization efficiency, this medium is filled from large to small diameter from the inlet to the exit of the mill according to the particle size of the solid material. It is preferable to use grinding media. However, in reality, the effects of solid material and fluid flow within the mill may cause them to align in the opposite direction. This will reduce the grinding efficiency, so in order to arrange and fill the grinding media in an appropriate state, it is necessary to partially arrange and fill the partition wall 1 as described above.
The grinding chamber 11 on the inlet side of the mill is filled with grinding media having a particle size distribution with a large average particle size, and the grinding chamber 12 on the outlet side of the mill is filled with a grinding medium having a particle size distribution with a large average particle size. The mill is filled with a grinding medium having a particle size distribution with a small diameter to prevent large-diameter grinding media from moving toward the mill outlet side. By the way, in the above-mentioned conventional slurry manufacturing mill, the viscosity of the slurry, which is a mixed system, changes in response to the progress and concentration of pulverization in a mixed system of solid materials and liquid, and the viscosity of the slurry changes under a high viscosity state. In this case, the movement of the grinding media within the grinding chamber is also irregular, which has a negative effect on grinding efficiency and grinding performance. In addition, a relatively small-diameter grinding medium is used for fine grinding, but as the mill rotates, the grinding medium rises along the liner of the mill, reaches a certain height, and then falls. Although there is a difference depending on the rotation speed of the mill, the impact action and grinding action between the grinding media and the solid material are insufficient. Especially in highly viscous slurry, grinding with a grinding medium with a small unit weight does not provide good grinding efficiency or grinding performance, and in some cases, coarse particles may not receive sufficient grinding action. It moves through the mill, and the finely ground slurry containing coarse particles is discharged from the mill. This is particularly noticeable when the effective diameter of the mill is relatively large and when a small-diameter grinding medium is used for fine grinding. [Problems to be Solved by the Invention] Therefore, the present invention provides an excellent method that can significantly accelerate the movement of the grinding media in the grinding chamber of a mill and obtain high grinding efficiency and grinding performance under high viscosity conditions. The purpose of this invention is to provide a mill for producing slurry. [Means for Solving the Problems] In order to solve the above problems, the slurry manufacturing mill of the present invention divides the mill into a plurality of grinding chambers by partition walls provided in the longitudinal direction of the mill, and In a mill for slurry production in which each grinding chamber toward the outlet is filled with grinding media that has a particle size distribution and the average particle size decreases sequentially, the mill effective diameter is constant in the longitudinal direction of the mill, and each grinding chamber is At least one chamber is filled with a grinding medium having an average particle size in the range of 20 to 25 mm, and the partition wall of each grinding chamber is defined by the following formula l _i ≦d _i / (a√+b) l _i : partition wall spacing (mm) d _i : Average particle size of grinding media in each grinding chamber (mm), weight-based arithmetic mean diameter, D: Mill effective diameter (mm) a: constant, -1.092×10 ^-4 b: constant, 0.01241 They are arranged at intervals according to the following. In the slurry production mill of the present invention, how the above-mentioned formula l _i ≦d _i /(a√+b), which defines the interval between the partition walls of the plurality of divided crushing chambers, was derived will be explained. The present inventors have studied mills for producing high viscosity slurries, and have found that as the mill increases in size, its performance tends to decrease when manufactured using conventional design methods. The experimental mill effective diameter and mill length are as follows. Mill No. = Mill effective diameter [mm] x Mill length [mm] A = 300 x (600 to 1500) B = 478 x 1500 C = 1200 x 2400 D = 2044 x 6330 E = 3850 x 500 F = 3850 x 11550 Also, the diameter of the grinding media used in mills A to F is d=
Various media ranging from 15 mm to 50 mm were used in combination in certain proportions. As a slurry, coal concentration is approximately 50%
Tests were conducted on COM. Particularly noteworthy in the test results was the difference in performance between the E-mill and F-mill, and it was thought that the main factor behind this difference was the length of the grinding chamber. As a mill that approximates the same grinding as the mill for slurry production of the present invention, albeit on a smaller scale,
There are so-called media stirred mills that use 5 mm grinding media. Examples include attritor mills, horizontal axis dyno mills that rotate disks, etc. In a media agitation mill, the ratio of the media to the diameter of the barrel or rotating disk can be more than 100 times, and from this point of view, it is also useful for elucidating the pulverization phenomenon. Among the factors that influence the grinding of a media agitation mill, we consider the missing item in the design factors of the slurry production mill that the present inventors are researching. This is the relationship between the diameter of the grinding medium and the diameter of the grinding medium, and we surmised that this corresponds to the relationship between the diameter of the grinding medium and the partition wall that partitions the grinding chamber of the slurry production mill being studied. Moreover, each term of the dimension between rotating disks and the diameter of the grinding medium with respect to the shear stress between the media in the grinding chamber, which evaluates the performance of the media agitation mill, has been expressed as a low-order proportional term. However, theoretically, it has not yet been clarified. Therefore, the present inventors also created the following experimental formula with reference to these ideas. As shown in Fig. 3c, if the length of the grinding chamber partitioned by partition walls is l, then the more active the movement of the grinding medium (average diameter d _i ) placed in the grinding chamber l is, the more , the shear stress between the grinding media increases and the grinding efficiency increases. Considering the influencing factors of the partition wall imparting its shear force in the length direction of the grinding chamber, that is, in the mill axial direction, the faster the partition wall rotates, the more the shear force can be transmitted in the axial direction. If the distance that can be transmitted is l′ from the partition wall, then
Letting the rotational speed of the partition wall be U, it can be considered that l'∝U...(1). Furthermore, since the larger the average diameter d _i of the grinding media, the easier it is to transmit the influence of the partition wall in the axial direction, it is thought that l′∝d _i ...(2). About the rotational speed U of the partition wall If the mill effective inner diameter is D, the rotational speed U of the partition wall is O on the mill axis, and at the point of the mill effective inner diameter D on the mill body wall, the maximum U _nax It is becoming.
If the speed U of the partition wall is expressed by U _nax , then U = U _nax = πD・N/60... (3) where N: Mill rotation speed (rpm) The critical rotation speed at the mill effective inner diameter D is N _c Then, N _c =42.3/√...(4), N=αN _c =α·42.3/√...(5) where α: constant, and the rotation speed N is determined. Substituting (5) into (3), U=k ₁ √ ...(6) Here, k ₁ =42.3πα/60 (constant), and substituting (6) into (1), we get l′∝ √ ……(7) becomes. Regarding the average diameter of the grinding media d _i and the mill barrel diameter When designing a ball mill, even if you scale up the mill from a small mill diameter to a larger mill diameter, the raw material particle size of the material to be ground will not change significantly, so the grinding The reality is that the design is not designed with a large change in the medium average diameter d _i . This point deviates from the hardware scale-up side, where the scale-up ratio is constant. Focusing on this, we changed equation (2) to the following equation, which is dimensionless. l'∝d _i /D...(8) Here, by combining equations (7) and (8), l'∝√d _i /D l'∝d _i /√...(9) is obtained. When the mill effective inner diameter D, mill rotation speed N, and grinding media diameter d _i are determined in the design specifications of the mill, the distance over which the shear force exerted by the partition wall is transmitted in the axial direction
It was assumed that l' was determined. As a result, as shown in FIG. 3a, the partition wall P _i ,
Comparing a mill in which the interval between P _{i +1} is l _I and a mill in which the interval between partition walls P _i and P _{i +1} is l〓 as shown in Fig. 3b, the partition walls P _i and P _i In the mill shown in FIG. 3a in which _{the +1} interval is narrower, the movement of the grinding media is more active, the shear stress between the grinding media is greater, and the grinding efficiency is higher. To explain this point in detail, Figure 3 a, b
, the horizontal axis corresponds to the shell plate of the mill, and h indicates the height of the partition walls P _i and P _i+1 . In Figure 3a, the shear force curve acting on the grinding medium at partition wall p _i is shown as S _i , and the shear force curve acting on the grinding medium at partition wall P _i+1 is shown as S _i+1. Ru. Also the shear force curve
S _ss is a composite curve of the respective shear force curves S _i and S _i+1 . The value of the shearing force shows a maximum value at a position where the grinding medium contacts and is close to the partition walls P _i , P _i+1 , and decreases at a position away from the partition walls P _i , P _i+1 . Similarly, in FIG. 3b, the respective shear force curves are shown as S _i and S _i+1, and the composite curve is shown as S _s l. Looking at the shear forces acting on the grinding media using the composite shear force curves S _ss and S _s l in Figures 3a and 3b, in the case of Figure 3b, the partition wall P _i ,
The interval l〓 of P _i+1 is wider than l _I , and the resultant shear force at a position away from the partition walls P _i and P _i+1 is
S _s I is significantly reduced and very little action is taking place. Therefore, it can be seen that the mill shown in FIG. 3a, in which the distance between the partition walls P _i and P _i+1 is narrow, has higher grinding efficiency. As a result, in order to have a highly efficient mill, if the interval between partition walls is l _i , then l _i ∝l′ ……(10) In other words, from (9), l _i ∝d _i /√ ……(11) Become. Based on the experimental data, the items of l _i , d _i , and √ are organized to show the grinding efficiency and particle size distribution of the slurry product, which shows the quality of grindability in terms of power consumption.
It was determined based on the n value of Rosin-Rammler equation, and the desirable size or lower value of l _i was examined. This was done on the assumption that d _i and √ can be evaluated individually from equation (11) using the following equation. l _i ≦d _i /a√D+b ...(12) where l _i : Spacing between partition walls (mm) d _i : Average particle size of grinding media in each grinding chamber (mm) (weight-based arithmetic mean diameter) D: Mill effective diameter (mm) a, b: constant In each of the mills A to F tested above, E mill has a smaller distance between walls than the mill effective diameter as shown in Figure 3 a, and the combined shear force is effective. It is assumed that the pulverization properties were very good. In addition, in the case of E mill, the mill inlet wall is as shown in Fig. 3a.
P _i , the mill outlet wall corresponds to P _i+1 . In addition, when experimenting with F mill as a two-chamber mill with one partition wall, the distance between the partition walls in the second chamber is 8085 (mm), and the resultant shear force becomes 0 as shown in Figure 3b. It is thought that no shearing force was applied to the powder, and the crushability was also poor. The limit value at which the combined shear force acts effectively was found under the following conditions for a three-chamber mill with two partition walls: C mill and F mill.

[Effect]

The present invention has the following effects due to the above configuration. In other words, in a mill, the average particle size changes from large to small in each grinding chamber, using a grinding medium with an average particle size according to the particle size distribution according to the particle size as the grinding of the solid material progresses. Under the gradually decreasing filling state, as the mill rotates, the grinding media is lifted upward along the liner and then falls like a waterfall, and there is an impact between the grinding media and the solid material. Furthermore, since the partition walls of each grinding chamber are arranged at intervals according to the above relational expression, the pulverizing action including the grinding action is carried out, and as a result of the fact that the partition walls of each grinding chamber are arranged at intervals according to the above relational expression, Synthetic shear force acts on the grinding media up to the point where the grinding medium is lifted up and dropped, making it even more active. Therefore, even if a small-diameter grinding medium is used to produce a slurry that exhibits a high viscosity state, the high viscosity state described above can be maintained. By overcoming this, the crushing action is promoted, and the crushing efficiency and performance can be significantly improved. [Embodiment] FIGS. 1 and 2 show an embodiment of the present invention. In Figures 1 and 2, 1 indicates a mill;
2 is the body of the mill, and 3 is a liner provided on the inner wall surface of the body. 4 indicates the inlet of the mill, and 5 indicates the outlet 5 of the mill. Inside the mill, a plurality of partition walls P ₁ , P ₂ , P ₃ , P ₄ , 6 are provided in the longitudinal direction of the mill, and the inside of the mill is divided into a plurality of grinding chambers C ₁ , C ₂ , C ₃ , C. It is divided into sections ₄ and _C5 . The length of the grinding chamber, that is, the spacing between the partition walls of the grinding chamber, is expressed by the distance between their center lines, and is expressed as l ₁ , l ₂ , l ₃ , l ₄ , and l ₅ from the inlet to the outlet of the mill. In each grinding chamber, the spacing is gradually reduced. Note that l ₁ indicates the distance from the outer peripheral edge of the inlet wall at the inlet end face of the mill to the partition wall P ₁ . Each grinding chamber is filled with grinding media, but the particle size distribution and average particle size of the grinding media are different, and the grinding chambers C ₁ , C ₂ , C ₃ , C ₄ , C ₅ and the mill The particle size distribution and average particle size of the grinding media are gradually reduced from the inlet to the outlet. That is, the grinding chamber _C1 on the inlet side of the mill is filled with a grinding medium having a particle size distribution with a large average particle size, and the grinding chamber _C5 on the outlet side of the mill has a particle size distribution with a small average particle size. Similarly, the grinding chambers C ₂ , C ₃ , and C ₄ are filled with grinding media having a particle size distribution in which the average particle size becomes smaller in order, so that the large-diameter grinding media is placed on the mill outlet side. It prevents you from moving to. The mill 1 rotates around its axis m, and when solid materials, liquids, and additives are supplied from the mill inlet 4 at predetermined supply rates, the solid materials are subjected to a crushing action. As it passes through the grinding chambers C ₁ , C ₂ , C ₃ , C ₄ , and C ₅ in order, it becomes finer and is discharged from the mill outlet with a concentration corresponding to the above-mentioned predetermined supply rate. FIG. 3 is a sectional view taken along the line I--I shown in FIG. 1, and the mill 1 is rotating in the direction of arrow A. Reference numeral 8 denotes a grinding medium. As the mill 1 rotates, the grinding medium 8 is lifted upward along the liner 3 and rises. After reaching a certain height, it falls under the action of gravity. The falling state is like a violent waterfall, and impact action and grinding action occur between the grinding medium and the solid material, causing the solid material to be crushed. 7 is a slit provided in each partition wall, and since the width of the slit is narrower than the diameter of the grinding medium 8, the grinding medium is prevented from moving to the adjacent grinding chamber, and only the slurry is passed through the slit in the partition wall. 7 and is discharged from the mill outlet 5. In addition, D is mil 1
indicates the effective diameter of The effective diameter of the mill is made constant in the longitudinal direction of the mill, and at least one of each of the milling chambers C ₁ , C ₂ , C ₃ , C ₄ , C ₅ contains a pulverizer with an average particle size in the range of 20 to 25 mm. Each grinding chamber C ₁ , C ₂ , C ₃ , C ₄ ,
The partition walls P ₁ , P ₂ , P ₃ , P ₄ , and 6 of C ₅ are calculated by the following formula l _i ≦d _i /(a√+b) where, l _i : Interval between partition walls (mm) d _i : Each crushing They are arranged at intervals according to the following: average particle size (mm) of the grinding media in the chamber, weight-based arithmetic mean diameter, D: mill effective diameter (mm) a: constant, -1.092×10 ^-4 b: constant, 0.01241. A comparison table of data for slurry production using a specific example of the mill according to the present invention described above and a mill according to the prior art is shown below. COM was used as the type of slurry.

〔Effect of the invention〕

As described above, in the mill for slurry production of the present invention, pulverization is performed in each pulverizing chamber by a pulverizing medium having an average particle size according to a particle size distribution according to the particle size as the pulverization of the solid material progresses, and further, in each pulverizing chamber. A synthetic shear force is applied to the grinding media from a close position to a remote position in contact with the partition walls on both sides of the mill, making the movement of the grinding medium even more active, so that the grinding along the liner as the mill rotates. Further motions of lifting and dropping the media can be added. Therefore, by intensifying the crushing action, including the impact action between the crushing media and the solid material, it is possible to produce a slurry with a high viscosity, thereby improving the crushing efficiency even when using a small-diameter crushing media. It is possible to significantly improve the grinding performance and grinding performance. Furthermore, since the uniform mixing of the dispersant and the mixed system and the dispersion effect due to surface adsorption are promoted, the viscosity state of the mixed system can be improved, which can also contribute to improvements in grinding efficiency and grinding performance. The effects are enormous.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a mill for slurry production according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line I-I in FIG. FIG. 4 is a cross-sectional view of a conventional slurry manufacturing mill. 1... Mill, 8... Grinding media, C ₁ , C ₂ , C ₃ ,
C ₄ , C ₅ ... Grinding chamber, l ₁ , l ₂ , l ₃ , l ₄ , l ₅ ... Spacing between partition walls.

Claims (1)

[Claims] 1. The mill is divided into a plurality of grinding chambers by partition walls provided in the longitudinal direction of the mill, and each grinding chamber from the inlet to the outlet of the mill has a particle size distribution, and the average particle size is gradually reduced. In a mill for slurry production filled with grinding media of
The chamber is filled with grinding media with an average particle size in the range of 20 to 25 mm, and the partition walls of each grinding chamber are defined by the following formula: l _i ≦d _i / (a√+b) l _i : Spacing between partition walls (mm ) d _i : Average particle size of the grinding media in each grinding chamber (mm), weight-based arithmetic mean diameter, D: Mill effective diameter (mm) a: constant, -1.092×10 ^-4 b: constant, arranged at intervals according to 0.01241 A slurry manufacturing mill characterized by the following: