1 mixing mill

The fine grinding action of the agitating mill is achieved by applying a power directly to the grinding medium by means of a stirrer. Compared with ball mills, ordinary ball mills and vibratory mills need to rotate or vibrate the bulky cylinders including grinding media; the full input power of the agitator mill is directly used to agitate the grinding media, and the energy utilization rate is generally increased by 10 to 20 times. The purpose of high efficiency and ultrafine pulverization of materials.

Among various ultra-fine grinding equipments, the agitating mill has become a hot research topic at home and abroad due to its high efficiency, low energy consumption, easy operation and ultra-fine powder with an average particle size of less than 1 μm and uniform particle size distribution. In recent years, foreign countries have made great breakthroughs in ultra-fine pulverizing equipment. The typical ones are: (1) the former Soviet Union's "Yile crusher"; (2) the JIYU crusher in Western Europe; (3) Alpine Germany The company's fluidized bed reverse jet mill (AFG); (4) Japan's MICROS ultrafine mill, MF fine mill and PJM jet mill. When the structure and conditions are reasonable, these materials can pulverize the material to below 5μm, even 2μm ultra-fine powder. The corresponding materials are classified into dry type (circulating gas flow classification, centrifugal mechanical classification, selective gas classification) and wet (hydraulic rotation). Flow, spiral centrifugal grading) classification.

2 Development of superfine grinding technology for mixing mill
In 1928, klein and Szegvari proposed the basic principle of agitating mills. Natural sand was added to the mixing tank, and then artificial grinding media (ceramic balls, glass balls, steel balls, etc.) were applied, and the material was ground with a stirrer to open the stirring mill. history. They used agitator and spherical media to complete the fine-grained wet grinding for the coatings industry, and established UP (Unio nProcess lnc), specializing in the design, manufacture and promotion of mixing mills.

In 1939, the US Mines Bureau designed a grinder to clean the mineral surface before flotation. The grinder consists of a rotor and a stator mounted in a vertical cylinder. The relative motion between the rotor and the stator produces friction between the particles to clean the surface of the mineral. The device is found to be a very effective fine grinding machine. equipment. The late 50's to early 60's, the US Bureau of Mines to the mill fine grinding done a lot of research, and for large-scale processing of kaolin and titanium oxide.

In 1948, DuPont developed a high-speed mixing mill Sandmill-sand mill, which was mainly used to produce pigments in the paint industry and became a major turning point in the development of agitator mills. 50's by the river end of Japan's heavy wins KubotaTowerMill Dr developed a new type of stirred mill - tower mill, spiral mixer, for metallurgy, mining and processing of coal, cement, industrial minerals and a variety of sulfide ore, and exported to the US ,Australia. This type of tower mill has achieved significant benefits in the field of ultrafine grinding and chemical processing (Table 1).

Table 1 Some products of tower grinding

In 1956, Szegvari invented another type of agitator mill that used a stirrer consisting of elongated iron rods and a cold water jacket on the outside of the body. The grinding was carried out in a vertical cylindrical vessel. The ore size is from 40μm to 1mm, the product size can reach 10~20μm, the grinding medium is stainless steel, tungsten carbon steel, ceramic or gravel, and the medium size ranges from 3 to 6mm. The continuous operation of the Szegvari fine grinding machine was patented in 1964. From 1965 to 1967, Engels changed the open top of the mixing mill to a closed type, which helped to further increase the speed of the mixing mill. In 1970, Wilhelm added a stirred mill media separator to handle materials with a grinding viscosity of 5 Pa·s.

In the early 1970s, the Swedish MatterPartnerAG company developed the TRZK (dry) and NRZK (wet) type agitating mills, mainly for the processing of coal water slurry. In the mid-1970s, the mining equipment of the agitator mill was improved to increase the speed of the agitator. In 1976, the horizontal agitating mill was invented by Durr. The energy of this agitating mill is highly concentrated, the wear is reduced, and the grinding efficiency is greatly improved.

In 1979 the company introduced a Japanese American MPSI tower mill patented product to produce vertical stirred mill, and applied to the industrial sector lead zinc ore, gold and so on.

In the 1980s, Fryma of Germany developed a double-cone sander and improved the agitator; the development of the Attritor agitator in the United States has been widely used in the processing of ceramic raw materials.

In the early 1990s, the American Aquaflne Company and the British Joy Company developed a trough-type horizontal mixing mill; the Swedish Sala company's new bottom feed mixing mill, energy saving 60%. In recent years, Mitsubishi Sanchi Co., Ltd., UP Company of the United States, NETZSCH of Germany, and Torrance & Son of the United Kingdom have used batch and circulating agitating mills, which have been widely used in fine ceramics, abrasives, powder metallurgy, hard alloys, magnetic materials, In the fields of paint and non-metallic minerals, the fineness of the product can reach 1μm.

Table 2 Some products of agitated grinding

At present, agitating mills have been applied to pigments, ceramics, paper fillers and complex minerals. Table 2 is a product processed by agitating mill. With the rapid development of industry, the importance of ultra-fine powder has been gradually recognized, and its demand is increasing.

Since the 1980s, China has started to use the foreign technology to start the production of mixing mills. Zhengzhou Dongfang Machinery Manufacturing Plant, Suzhou Non-Metallic Mining Industry Design and Research Institute, Changsha Mining and Metallurgy Research Institute and other units have successively developed various types of mixing mills, and in the chemical industry, non-chemical The metal ore, coating and powder metallurgy industries have been initially applied. However, as a whole, the variety is small, the structure needs to be improved, and the basic work lags far behind the foreign level. Due to the needs of the application, the basic research work on the superfine pulverization of the agitating mill is mainly focused on the wet fine grinding. This is because the wet superfine pulverization can be continuously carried out, easy to achieve automation, and good dispersion compared with the dry method. To prevent dust pollution and other advantages.