JPH04210257A - grinding system - Google Patents

Abstract

PURPOSE:To improve the crushing efficiency of the crushing system by classifying the powder with a flash classifier into fine powder, intermediate powder and coarse powder and returning the coarse powder to a precrusher and the intermediate powder to a main crusher through respective pipelines. CONSTITUTION:The newly fed material is passed through a hopper 100, precrushed by a precrusher 200 such as a roll press and a vertical roller mill, sent to a main crusher 300 of a rotary cylinder-type ball mill and crushed. The crushed material is collected by a cyclone 310 and sent to a flash classifier 710 through a conveyor 400, a bucket elevator 500 and a conveyor 600. The fine powder passed through the cyclone 310 is freed from the coarse powder in a cyclone 320 and air-floated to the cyclone 800 of a product line or a bag filter 900. Meanwhile, the particulate matter introduced into the classifier 710 is separated into fine powder, intermediate powder and coarse powder, and the fine powder is passed through the cyclone 800 and bag filter 900 and collected as the product. The intermediate powder is returned to the main crusher 300, and the coarse powder is joined to the newly fed material in the hopper 100 and returned to the precrusher 200. The unit power requirement is reduced in this way.

Description

[Detailed description of the invention]

[0001]

[Industrial Application Field] The present invention is applicable to cement raw materials and coal. The present invention relates to a pulverization system for pulverizing raw materials such as chemicals, and particularly to a pulverization system designed to improve pulverization efficiency. [0002]

[Prior art] In order to finely grind granules such as cement raw materials, coal, chemicals, etc. into fine powder, a conventional rotating cylindrical ball mill and a fine powder are used to grind the pulverized granules to the required particle size. A pulverization system that combines a closed circuit with an airflow classifier that separates fine powder into coarse powder with a larger particle size has been widely used. FIG. 5 is a flow sheet of a conventional crushing system, in which powder and granules crushed by a 9-turn cylindrical ball mill 300 are collected by a cyclone 310 and a cyclone 320, and then collected by a transporter 400. packet elevator 500
It is fed into an air classifier 700 via a transporter 600, where it is classified and separated into fine powder and coarse powder.The fine powder is passed through a cyclone 800 or a bag filter (or an electrostatic precipitator).
It is collected at 900 and made into a product. On the other hand, the coarse powder is re-supplied together with the pulverized raw material to the rotary cylindrical ball mill 300 and pulverized. Reference numerals 810 and 910 are suction fans. [0003] The crushing process is generally a power-intensive process, and energy saving measures by increasing the efficiency of the crushing process have become an extremely important issue.Therefore, in recent years, the crushing process has been equipped with a grinder immediately before the main crusher. As shown in the flow sheet of FIG. 6, crushing systems incorporating roll presses, vertical roll mills, etc. have come to be used as preliminary crushers. In this pulverization system, coarse powder after being classified by an air classifier 700 is divided into a preliminary pulverizer 200 and a main pulverizer 300 in an appropriate ratio.
The grinding system is such that the coarse powder after 9 classifications and the grinding raw material of New Feed are fed to the pre-pulverizer 200 after being combined in the hopper 100, as shown in Figure 5. It is true that the power consumption rate for crushing is improved compared to the previous one. [0004]

[Problems to be Solved by the Invention] However, when the pulverization system shown in FIG.
Regardless of the particle size distribution, the powder is simply divided mechanically and re-supplied to the preliminary crusher and main crusher respectively, and the coarser powder of the returned powder is selectively supplied to the preliminary crusher. Therefore, even in this grinding system, there was a limit to the improvement in grinding efficiency, that is, the energy saving effect. [0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the crushing system of the present invention comprises a crushing device in which a rotating cylindrical ball mill as a preliminary crusher and a main crusher are arranged in series, and the main crusher. In a crushing system configured in a closed circuit with an air classifier that classifies the material to be crushed, the air classifier is a classifier that can classify fine powder (fine powder), intermediate powder, and coarse powder. The grinding system has a transport route for re-feeding powder to the preliminary grinder and re-feeding the intermediate powder to the main grinder. [0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below based on nine drawings. 1 to 4 show embodiments of the present invention.9 FIG. 1 is a flow sheet of the crushing system of the present invention. FIG. 2 is a schematic side sectional view of an air classifier.9 FIG. 3 is a plan view of the air classifier. 9. FIG. 4 is a cross-sectional plan view taken along IV-IV in FIG. 2. [00071 In the figure, 100 is a hopper, 200 is a preliminary crusher, and 300 is a main crusher, and in this embodiment, a rotating cylindrical ball mill is used. 310 and 320 are cyclones, 400 is a transport aircraft, 500 is a packet elevator, 6
00 is a transport aircraft, transport aircraft 400 and transport aircraft 600
A belt conveyor or screw conveyor can be used. 7
10 is a two-stage classification type airflow classifier, 800 is a cyclone for collecting the product (fine powder), 900 is a pack filter (or electric dust collector), and 810 and 910 are suction fans. [00081] Next, the structure of the two-stage classification type airflow classifier 710 will be explained based on FIGS. 2 and 3. The classification air flow introducing pipe 1 is arranged at one or more places around a plurality of guide vanes 7 which are integrally formed with the upper spiral casing 4 and arranged in an inverted truncated conical shape. The secondary classification blade 9 is attached to the upper rotating shaft 14 located at the center via the upper mounting frame 15, and the plurality of secondary classifying blades 11 are attached to the lower rotating shaft 12 via the lower mounting plate 13. The centers of the upper rotating shaft 14 and the lower rotating shaft 12 are on the same vertical line, and the guide vanes 7, primary classification spaces 8, 1
The secondary classification blade 9, the secondary classification space 10, and the secondary classification blade 11 are constructed in the shape of a concentric inverted truncated cone centered on the rotation axis. The air rate type overflow distributor 2 is installed in an annular manner at the upper part of the upper spiral casing, and uniformly distributes and supplies the classified raw material from one or more raw material supply air slides 3 to the primary classification space over the entire circumference. It is for the purpose of The equalizer 22 is for making the level of the classified raw material from the air slide 3 uniform over the entire circumference of the air rate type overflow distributor 2, and the dispersion aileron 20 is a component of the air rate type overflow distributor 2. This is for completely dispersing the raw material uniformly overflowing from the overflow side plate 21 into the airflow and introducing it into the primary classification space 8. Fine powder gathering chamber 16 and fine powder uI
The outlet pipe 17 undergoes primary classification in the primary classification space 8, and further undergoes secondary classification.
The fine powder, which has finally undergone secondary classification in the secondary classification space 10 and is entrained in the first classification airflow, is transferred to the next cyclone 800. This is for leading to a bag filter (or electrostatic precipitator) 900. An annular air slide 18 for discharging coarse powder is connected to the lower circumference of the inverted truncated conical lower casing 5 and the truncated conical lower inner casings 6 and 9, which are approximately the same height as the lower casing 5.
is for collecting and discharging the coarse powder falling from the lower part of the primary classification space 8. Similarly, for collecting and discharging the intermediate powder falling from the lower part of the secondary classification space 10, the lower casing 5 and the truncated cone-shaped lower inner casing 6a having approximately the same height as the lower casing 5 are installed inside the lower casing 5. and 9 Annular intermediate powder discharge air slide 1 connected to the lower circumference of both
8a is provided. Reference numeral 19 is a transportation air slide connected to the coarse powder discharge air slide 18 at an appropriate position. 23 and 24 are support plates for suppressing vibration of the primary and secondary classification blades, respectively. [0009] The operation of the above classification device will be explained next. The classification airflow supplied at an appropriate speed through the classification air introduction pipe 1 flows into the primary classification space 8 due to the spiral shape of 1 and the guide vane 7, and flows inward in the radial direction at a speed commensurate with the amount of air passing through 9. Turn with power. On the other hand, the 9-class raw material passes through the raw material supply air slide 3 and is input into the air rate type overflow distributor 2. The air rate type overflow distributor 2 is arranged circumferentially in the upper part of the classification space 8, and the campus 25
The one-class raw material is partially fluidized by high-pressure air supplied through the overflow side plate 21, and uniformly overflows over the entire circumference from the overflow side plate 21. The equalizer 22 is arranged for the purpose of making the overflow layer thickness uniform over the entire circumference of the classified raw material from one or more raw material supplying air slides 3. This method overcomes the drawbacks of the prior art and allows for a uniform and stable input into the classification space that is low in energy, low cost and independent of operating conditions. The raw material overflowing from the overflow side plate 21 is completely dispersed into the airflow by the dispersion auxiliary vane 20 attached to the upper mounting frame 15 of the primary classification blade 9 rotating nine times and located directly above the primary classification space 8. It falls into the next classification space 8. [00101 The primary classification blade 9 is fixed to the upper rotating shaft 14 via the upper mounting frame 15, and the outer peripheral speed of the primary classifying blade 9 is controlled by a motor (not shown) connected to the upper rotating shaft 14. It is rotated at a speed somewhat higher than the circumferential velocity component of the classified airflow flowing in from 7, and is applied to the classified material swirling in the primary classification space 8 through the swirling airflow caused by the primary classification blade 9 or directly. The impact provides an outward force in the circumferential direction. The classification effect is strengthened by the so-called centrifugal force effect. The raw material that has fallen into the upper part of the primary classification space 8 is continuously subjected to primary classification by the 9-classifying air and the primary classification blade 9, that is, part of the fine powder and coarse powder is continuously removed, and the raw material itself is While decreasing the amount, in other words, decreasing the concentration, it swirls and falls, passing through the primary classification space 8. On the other hand, 1
Coarse powder that cannot pass through the next classification space 8 is transferred to the air slide 18. By constructing the primary classification space 8 into which the classified raw material is introduced from the top in a truncated cone shape with the upper and lower diameters decreasing and increasing at an appropriate ratio with respect to the middle part in the vertical direction, In areas of high concentration. By reducing the rotation radius of the classification blade, the centrifugal force effect on the particles of the classification blade is reduced, and in the lower concentration area, the classified particle size becomes larger. This migration is prevented by increasing the centrifugal force effect on the particles of the classification blade by increasing the rotation radius of the classification blade.1 Figure 13 conceptually shows the effect of the conventional technology in comparison with the effect of the conventional technology. As a result, it is possible to match the classified grain size in the middle part with the distance between the paths, and as a result, it is possible to provide sharp primary classification performance with almost the same classification point regardless of the height direction. [0011] On the other hand, the fine powder and some coarse powder that have been classified into 2 in the primary classification space 8 and taken by the 9-class airflow and passed through the primary classification blade 9 are transferred to the guide vane 7, the primary classification space 8, It flows into the secondary classification space 1o sandwiched between the primary classification blade 9 and the rotating secondary classification blade 11, which are provided concentrically inside the primary classification blade 9, and rotates. The secondary classification blade 11 is attached to the lower rotating shaft 12 via a lower supporting plate 13, and the lower rotating shaft 12
9, the circumferential speed of the secondary classification blade 11 is rotated by another connected prime mover (not shown) at a speed that is somewhat faster than the circumferential speed of the classified airflow flowing into the secondary classification space 1o. A centrifugal force effect is applied to the secondary classified raw material entrained by the classification airflow to strengthen the classification action. [0012] The secondary classified raw material that has flowed into the secondary classification space 10 is sequentially subjected to secondary classification from the position where it flows in, that is, fine powder is continuously removed, and the secondary classified raw material that is located below the position where it flows is removed. While merging with the rest of the
It passes through the next classification space 10. [0013] On the other hand, coarse particles that cannot pass through the secondary classification space 10, ie, the intermediate powder, fall downward and move to the air slide 18a. [00141 In the air classifier 710 capable of two-stage classification according to the present invention as described above, fine powder and coarse powder having a desired particle size or less and intermediate powder having a particle size intermediate between the fine powder and the coarse powder are used. can be taken out separately. [0015] In this way, the method of arranging 9 classifications in series and performing coarse classification in the first stage and final classification in the second stage is such that in the first classification at a relatively high supply amount, in other words, the concentration is relatively high, the average classification The particle size is made several tens of percent larger than the target average classified particle size, and the classification is performed in a low division area, and in the secondary classification, 1
By performing classification to obtain the desired average classified particle size in a state where the concentration is reduced in the next classification, it is possible to achieve a sharp classification with fewer divisions in the overall classification performance.

Next, the operation of the crushing system of the present invention will be explained according to the flow sheet shown in FIG. After being crushed, it is sent to the main crusher 300, which is a 9-turn cylindrical ball mill, and is crushed. The raw material after pulverization is collected by a cyclone 310 and transported by a transporter 400. Packet elevator 500. It is sent to the pneumatic classifier 710 via the transporter 600. The fine powder that has passed through the cyclone 310 is transferred to the cyclone 320
After the coarse powder is separated, it is transported by air to the product line's cyclone 800 or bag filter (or electrostatic precipitator) 90.
Head towards 0. [0017] On the other hand, the granular material entering the airflow classifier 710 is separated into fine powder, intermediate powder, and coarse powder, and the fine powder is collected toward the cyclone 800 and the bag filter 900 and made into a product. Further, the intermediate powder is re-supplied to the main pulverizer 300, and the coarse powder is combined with the pulverized raw material of New Feed in the hopper 100 and then re-supplied to the preliminary pulverizer 200. [0018] As described above, in the crushing system of the present invention, the coarse powder with a relatively coarse particle size is sent to the pre-pulverizer 200 from among the powder particles (returned powder) after the 9 classifications, and the coarse powder with a relatively small particle size is Since the system is used to selectively re-supply intermediate powder to the main pulverizer, the pulverization efficiency is improved and sharp fine powder with a narrow particle size distribution can be obtained as refined powder. [0019]

Effects of the Invention The pulverizing system of the present invention achieves high pulverizing efficiency, thereby reducing the electric power consumption of the pulverizing process, and at the same time, it is possible to obtain a high-quality product with a narrow particle size distribution.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of a grinding system illustrating an embodiment of the present invention.

FIG. 2 is a schematic side sectional view of an air classifier showing an embodiment of the present invention.

FIG. 3 is a plan view of an air classifier showing an embodiment of the present invention.

FIG. 4 is a cross-sectional plan view taken along line IV-IV in FIG. 2;

FIG. 5 is a flow sheet of a grinding system showing a conventional example.

FIG. 6 is a flow sheet of a crushing system showing another conventional example.

[Explanation of symbols]

100 hopper 200 Preliminary crusher 300 Main crusher 310 Cyclone 320 Cyclone 400 Transport aircraft 500 Packet elevator 600 Transport aircraft 700 Airflow classifier 710 Airflow classifier 800 Cyclone 900 Bag filter or electrostatic precipitator

[Figure 3]

Claims (1)

[Claims] Claim 1: A crushing system configured in a closed circuit of a crushing device in which a rotating cylindrical ball mill as a preliminary crusher and a main crusher are arranged in series, and an airflow classifier for classifying the material to be crushed by the main crusher. , the airflow classifier is used to classify fine powder (fine powder).
A crushing system having a classification device capable of classifying into intermediate powder and coarse powder, and a transportation route for re-supplying the coarse powder to the preliminary crusher and re-supplying the intermediate powder to the main crusher.