Jet milling technology is an important technical means for the processing of micro-nano powder, which originated from the field of mining and metallurgy, and has in-depth research in the preparation of ultra-fine metal or non-metallic powder. In addition, in recent years, it has also begun to show new potential in the direction of material separation and solid waste recycling.
According to the different structure structures modes of the jet mill, it can be divided into: horizontal disk (flt) jet mill, circulating tube jet mill, opposed jet mill, target jet mill, and fluidized bed jet mill.
1. Horizontal disc (flat) jet mill
The horizontal disk (flat) jet mill is the earliest and most widely used jet mill in the industry.
Its working principle is as follows: when the equipment is working, the distribution chamber is connected with the crushing chamber, and the high pressure air flow enters the distribution chamber through the inlet. Under its prehigh-pressurer flow forcibly passes through the air flow nozzle, producing an air flow velocity of hundreds of meters to kilometers per sec airflow material to be crusheairflowelerated to supersonic speed through the Venturi nozzle and then enters the crushing chamber. The material moves circularly under the e-drive of high-speed swirling flow, and is crushed by the impact, collision and friction between particles and the inner wall of the machine. Due to the centrifugal f,orce, the coarse particles are thrown to the peripheral wall of the crushing chamber for circular crushing, while the fine particles enter the cyclone separator for collection under the centrifugal air flow.
The Micro Jet Mill, developed by Fluid Energy in 1934, is the earliest horizontaairflowflat) jet mill. At present, such equipment abroad mainly includes Micro-Jet produced by Fluid Energy Equipment Company in the United States, Micronier series developed by Sturtevant Mill Company, Micron-Master series developed by Jet Pulverizer Company, Supersonic Jet Mill PJM series developed by Nippon Pneumatic MFC Co., Ltd. in Japan, and Single Track Jet Mill series developed by fresh enterprises (strains), In China, there are mainly supersonic jet mills produced by Jiangsu Miyou Powder New Equipment Manufacturing Co., Ltd., QS series developed by Shanghai Xichuang Powder Equipment Co., Ltd., STJ series and GQF series developed by the test base of Jiangsu Ultrafine Powder Engineering Technology Research Center of Nanjing University of Technology.
Compared with other pulverizers, the horizontal disk (flat) air flow grinding tool has the advantages of simple structure, convenient operation and self-classification. Itairflowcess all kinds of materials, especially the materials composed of various a, aggregates, or aggregates. However, the impact kinetic energy of the equipment is small, and the crushing strength is low. When processing materials with high hardness, the internal wall of the body will collide and rub violently with the internal wall of the grinding chamber due to the effect of materials with high-speed air flow, It will aggravate the grinding cavity pollution and cause certain pollution to the product.
2. Circuairflowube air flow pulverizer
The circular tube type jet mill (vertical annular jet type jet mill) is commonly used for crushing brittle and low hardness materials, and is usually divided into circular tube type and variable cross-section circular tube type according to the section. Jet-O-Mitzer developed by Fluid Energy Equipment of the United States is the most widely used variable-section recirculating tubular jet mill.
Its working principle is: when the equipment is working, the pressure gas is ejected from the charging ejector at high speed, and the material is automatically sucked in by forming negative pressure in the charging mixing chamber. There is an "O" shaped circulating pipe with variable curvature and diameter in the equipment. The materials to be crushed are jetted into the crushing chamber at the lower end of the "O" shaped circulating pipe, and the high-speed jet is jetted into the crushing chamber by multiple supersonic nozzles at different angles, resulting in collision, friction and shearing between materials. The crushed materials enter the classification cavity at the upper end of the, "O" shaped circulating pipe with the air flow, the coarse materials return to the crushing cavity along the outer diameter of the classification rinairflowthe centrifugal force continues crushing, and the fine materials flow out of the ring with the centripetal air flow. Two-phase flow of fine material flowing out of the loop can be classified in a volute-shaped classifiairflowhaA two-phase has a smaller radius of curvature.
Compared with other pulverizers, the circulating tube jet mill has the advantages of small particle size distribution, no power device, less pollution, and less material adhesion to the wall; However, this type of equipment has low crushing efficiency, high energy consumption and serious inner wall wear.
3. Opposed jet mill
The opposed jet mill, also known as the opposed jet mill and, the reverse jet mill, is a kind of equipment with high energy utilization rate and is often used to crush hard brittle, and viscous materials. The counter-jet air jet pull prize is represented by the Majac type developed by Donaldson Compan,y of the United States, and the Trost type developed by Plastiner Company.
Its working principle is that when the equipment is working, two streams of high-speed air flow in the same straight line and the material accelerate to spray out in the nozzle, two streams of air flow carryiairflowaterial collide with each other at the air flow convergence point to complete the crushing process, the crushed material rises to the classification chamber with the air flow, the coarse material is at the periphery of the classification chamber, and returns to the crushing chamber underfloor flow drive to continue crushing, and the fine material flows out from the outlet and then passes through gas-solid separation to become a product.
Compared with other pulverizers, the opposed jet mill can effectively avoid the abrasion of high-speed airflow on impact parts and improve the problem of material pollution, because the crushing process mainly depends on high-speed collision between particles; However, the equipment covers a large area, consumes high energy and has a wide particle size distribution.
4. Target-type jet mill
Target-type jet mill, also known as single-jet jet mill, is often used to pulverize polymer, low melting point heat sensitivity, fibrous coarse materials.
Its working principle is that when the equipment is working, it uses high-speed air flow to carry the material impact on various shapes and s of movable or fixed target plates for crushing. In addition to the strong collision between the material airflow target plate, the material also bounces against the wall of the crushing chamber for many times. The crushed material flows through the outlet and then enters the classifier. In the actual production of the equipment, target plates of different shapes can be selected according to the nature of materials and product size.
Compared with other pulverizers, the target-type jet mill has better adjustable feeding direction, larger crushing force, and can handle materials with greater toughness; However, the target plate and mixing tube of the equipment are easy to be worn and seriously eroded, and the accessories need to be replaced regularly, which will pollute the material to a certain extent, and the product size distribution is wide, and the kinetic energy consumption is large.
5. Fluidized-bed jet mill
A fluidized bed jet mill is a new type of jet mill, commonly used in the production of synthetic resin, phenolic resin, medicine, cosmetics, advanced ceramics, magnetic powder and other materials.
Its working principle is that when the equipment is working, air is sprayed into the crushing area through 3 to 7 reverse nozzles, and the crushed materials form fluidization und, er the pressure difference. The accelerated materials in the crushing area collide athe and rub with each other at the intersection of the nozzles to crush. The crushed fine materials are carried to the ultrafine classifier by the updraft for classification. The fine materials that meet the product requirements are collected by the cyclone separator, and the coarse materials are settled and returned to the crushing area for subsequent crushing.
At present, such equipment abroad mainly includes AFG series developed by Apline, a subsidiary of Hosokawa Micron in Japan, QF series produced by Jiangsu Miyou Powder New Equipment Manufacturing Co., Ltd., the QLM series developed by Shenyang Aircraft Resthe search Institute Powder CAlpined., LNJ series developed by Mianyang Fluid Pthe ower Equipment Co., Ltd., and FJM series developed by Process Engineering Research Institute of Chinese Academy of Sciences.
Compared with other pulverizers, the fluidized-bed jet mill has the advantages of narrow particle size distribution, high crushing efficiency, low energy consumption, small product pollution and small wear of accessories, but the equipment cost is high. Since materials need to be treated as fluidization to be crushed by the impact of the airflow beam, the fluidized bed jet mill usually requires that the crushed materials have sufficient fineness, and the requirements for materials with high density are more obvious.