This kind of grinding machine can be used for dry grinding and wet grinding; the common medium is long rod and the surface hardness is HRC51~55. The shape and size of the grinding media is typically selected based on the feedstock and product size. Figure 31 shows the type of grinding media that should be selected for different feedstock and product particle sizes. Under certain circumstances, for example, when the grinding product is required to be extremely fine, a certain "cushion" effect is generated in the mill. At this time, it is not appropriate to use a steel ball or a steel segment, and a steel bar should be used; in addition, a certain product in the product is required. Steel rods are also used as grinding media when the grade content is high. [next] The vibrating mill has the advantages of large output per unit volume, high grinding efficiency, small floor space, light weight of equipment and simple process. In recent years, with the special requirements of product fineness of powder metallurgy, chemical dyes, specialty ceramics and refractories and other high-level, vibration mill there are new rapid development. Improve the mill barrel to make it easy to seal, or add inert gas for ultra-low temperature protective grinding; these characteristics are suitable for ultra-fine grinding of solid materials such as flammable, explosive and easy to carbonize. When used in dry grinding, the vibrating mill can grind the material with a particle size of 1~2 mm to a particle size of 85~5 microns. For wet grinding, the product size can reach 5~0.1 microns. Fine particles. [next] In addition to the wet separation system, the dry tower mill has the same air separation system as the wet scrubber. The mill barrel, the spiral mixing blade and the spindle drive are exactly the same as the wet tower mill. Hot Melters,Hot Melters Equipment,Manual Adhesive Application Melter,Hot Melt Adhesive Scattering Machine Wahrheit Automation & Trading Co., Ltd. , https://www.wahrheitcn.com
Figure 29 shows the widely used Para-type vibrating mill produced by Humboldt Weid, Germany. The machine has two upper and lower grinding cylinders 1; the two grinding cylinders are connected by 2~4 transverse support plates 2; The support plate 2 is supported by the rubber spring 3 on the frame, and the main shaft 4 and the eccentric weight 5 are assembled in the middle of the support plate. The main shaft 4 is coupled to the motor through a universal joint. When the spindle rotates, the eccentric weight generates centrifugal force to vibrate the system. Each eccentric weight is composed of two small pieces. Adjusting the angle of the two can adjust the magnitude of the centrifugal force to adjust the amplitude. The cylinder of the Para-type vibrating mill has a length to diameter ratio of 12.5, a diameter of [next] of 200 to 650 mm, and a length of 1300 to 4,300 mm. One end of the vibrating mill cylinder is coupled to the feeding portion, and the other end is coupled to the discharge portion, and the feeding and discharging portions may be coupled in the middle portion as needed. Figure 30 shows several different barrel couplings. The grinding time of the material depends mainly on the length of the flow path. In Figure 30, a is a series system, the material has the longest grinding time, up to 1 hour, suitable for hard materials, or the feed size is large, or the product size is fine; b is a parallel system; c is a semi-parallel system, grinding time is only about 1 minute, for example, brown coal mill; d is 1/4 of the parallel system, the minimum grinding time, only about 0.5 minutes. It should also be noted that the coupling system of the Para-type vibrating mill can be changed at any time as needed, and the flexibility is strong. Another example is when grinding and mixing two materials of different hardness, the harder material is fed from the head end, and the softer material is fed at a point behind the barrel, so that the same fineness can be obtained. product. [next]
Vibration grinding also has some shortcomings, among which are: high mechanical requirements, especially large-size machines, in which springs and bearings are easily damaged, and it is difficult to grind some materials, such as tough materials and heat-sensitive materials. The requirements for moisture are strict, and the yield is greatly reduced when the water content in the raw material exceeds 4 to 5%. Due to the strict mechanical requirements, such mills are not manufactured to a large size like other mills; and with their low stand-alone output, they cannot meet the requirements of large-scale production.
(3) Medium agitating mill The barrel of the agitating mill is equipped with a blade type stirring device and a ball medium (ceramic ball, glass ball, steel ball, etc.), and the stirring device rotates to rotate the ball medium, thereby generating impact and shearing. The material is ground by cutting and grinding.
According to the structural characteristics of this type of mill, it can be divided into tower type, agitating tank type, flow tube type and ring type. Such a mill can be used as an ultrafine mill, a stirring mixer or a dispersing machine. According to the production method, it can be divided into dry and wet. In dry grinding, the pressure strength of the material particles increases, the surface energy of the particles increases, and aggregation occurs between the particles, which tends to adhere to the inner wall of the mill barrel. In the case of wet grinding, the surface energy of the particles is lowered due to the good particle dispersing performance, and the particles can be prevented from agglomerating. Therefore, wet grinding is preferred in the case of ultrafine grinding.
A Tower Mill The Tower Mill is actually a vertical cylindrical vertical ball mill . The mill is composed of a vertical cylinder, a spiral agitating blade, a classifying device and a driving device. The specification of the tower mill is expressed by the inner diameter and height of the cylinder, that is, D x H.
Tower mills are also available in both dry and wet types. Figure 32 is a diagram showing the closed production system of the wet lap mill. The main (vertical) shaft in the vertical cylinder is equipped with a spiral stirring blade (or agitator), and is driven by the driving device of the motor to perform a rapid rotating motion, thereby forcing the grinding medium and the material to be ground in the mixing cylinder to rotate strongly. The material is pulverized by grinding. The pulverized product flows into the classifier by the mill, and is classified by a hydrocyclone. The overflow is the grinding product, and the coarse particles are returned to the mill through the pipe and then ground. [next]
The basic grinding action of the tower mill is to strip and not impact, so the feed size can not be too large, generally less than 3 mm. The vertical installation of the grinding cylinder is mainly based on the following considerations: (1) The medium rotates in the horizontal plane under the action of the agitator, instead of acting in the vertical direction and parabolic motion like in the horizontal grinding machine, so that the grinding medium does not overcome Gravity works to save energy; (2) The tower mill has a small diameter and a large height, which increases the pressure of the grinding medium, and increases the grinding force on the material when the grinding medium rotates; therefore, this The equipment is suitable for fine grinding and ultra-fine grinding of materials. The pressure of the grinding medium has a suitable range in which the grinding efficiency is high and the power consumption is low; when it exceeds this range, the grinding efficiency can no longer be increased; therefore, the height-to-diameter ratio (H/D) of the tower mill There should be a suitable value. The tower mill is mainly used for grinding and stripping, so the size of the grinding ball should not be too large. Generally, the maximum ball diameter is about 25 mm. When it is ultra-fine grinding, the size of the grinding media should be smaller.
This type of mill first appeared in 1953 and was used to replace the ball mill as a medium mine re-grinding. Laboratory and industrial tests have been carried out on tower mills at home and abroad. U.S. e.g. copper plant in New Mexico (Copper Flats) installation of a tower mill for regrinding molybdenum concentrate. Marcassa, Ontario, Canada installed a 200 kW tower mill to simultaneously pulverize and leach the tailings of the gold. The mill's production capacity for the tailings is 12.2 tons / hour, the tailings Bond's work index is about 14.5 kWh / ton, the tailings - 325 mesh content is 45%, and the -325 mesh accounts for 95%. . The production test shows that the tower mill saves more than 60% of the electric energy compared with the general ball mill, and the investment is similar. The tower mill requires a small foundation and saves space, so the installation cost is much lower than that of the ball mill.
Comparison of results when grinding uranium ore with a ball mill and a soil tower mill. From the test results, it can be seen that the tower mill is more than twice as high as the ball mill, based on the energy consumed to produce one ton of material less than 200 mesh.
A comparison between the performance of a tower mill and a ball mill provided by a subsidiary of the US company Kopper. D is used in the re-grinding circuit of the Raka Mining Company in the Krand Lake. Based on the company's test results, the following insights are obtained:
Tower mills cannot replace conventional cylindrical mills, which are mainly used for re-grinding of mines. In addition, it can be used in the preparation of limestone slurry in flue gas desulfurization process, lime ripening, grinding and leaching in gold leaching circuit, mixing of water 6 coal and kerosene, and ultrafine grinding of coal or other materials. The tower mill feed should not be larger than 5 mm, otherwise the processing capacity and efficiency of the equipment will decrease. When the feed size is appropriate and the product size is less than 74 microns, the energy consumption is much less than that of a conventional mill. When the product size is required to be coarse, for example greater than 74 microns, the general tower mill does not save energy compared to the ball mill. [next]
The MQL-500 spiral stirring tower mill developed by the relevant units in China is also divided into dry and wet type. Wet tower mill in 1984 were more than half in the Shihe industrial test iron ore beneficiation plant, then later used as a flotation mill gold mine in Jinchang Yu gold, cyanide leaching step to meet the requirements under the plant. The plant uses a tower mill to grind 65.84% of the gold flotation concentrate less than 350 mesh to less than 350 mesh, accounting for 99.74%, and the mill utilization coefficient is 0.485 ton/ m3 . When the power consumption is 13.45 kW. / ton, steel consumption is 4.65 kg / ton.
In general, the advantages of tower mill and ball mill are: (1) suitable for superfine grinding; (2) simple structure, accounting for less plant area, no need for huge equipment foundation, saving installation Cost; (3) can be opened, closed, dry and wet, open circuit grinding can also obtain very fine products, which simplifies the process and operation; (4) smooth operation, low vibration, low noise, general Below 85 decibels, and ball mills are mostly in the range of 95 to 100 decibels; (5) the process of grinding and leaching of materials can be completed simultaneously in the tower mill, simplifying the process and improving the efficiency; (6) low.
The disadvantage of tower grinding is that the feed size is not too large and therefore not suitable for ore or coarse-grained grinding. Further, when the height of the mill is increased, the pressure of the grinding medium is also increased, and the grinding efficiency is improved, but the wear of the stirring member and the lining plate becomes a prominent problem. This limits the large-scale and large-scale application of tower mills.
The series of tower mills produced in Japan process a feedstock with a particle size of less than 3 mm and an average particle size of 10 microns (ton/hour).
B Stirred Groove Mill The structure of the mill is to have different shapes of stirring mechanism (such as spiral shape, disc shape, etc.) on the main shaft of the vertical cylinder, and use this structure to rotate into the cylinder. The grinding media (grinding balls, ceramic balls, etc.) produce agitating motion, causing the material to be crushed by strong shearing and grinding action. The mill barrel can be made of wear-resistant steel, stainless steel and other materials.
Agitated mills are typically wet open grinding.
Attritor agitator mills are available in three types: periodic, continuous and recirculating.
The periodic agitating mill (Fig. 33) is used to load the material to be ground into a circular cylinder whose outer circle is water (cold water or hot water), and to drive the cylinder due to the rotary motion of the round rod mounted on the vertical shaft. The body's grinding media is stirred vigorously to comminute the material. This mill can be used for ultra-fine grinding of tungsten carbide, ceramic materials, cobalt powder, and carbon black and inks that are difficult to finely grind. [next]
Figure 28 shows the MGZ-1 vibrating mill unit developed in China.
April 26, 2023