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Jet mill nozzle and crushing efficiency

Jet mill nozzle and crushing efficiency

发布时间 : 2021-06--24 点击量 : 0
Air jet pulverization is a device that uses the energy of high-speed airflow (300-500m/s) or superheated steam (300-400°C) to cause particles to collide, collide and rub each other, thereby causing particle smashing. The high-speed airflow is generated by the nozzles installed around the pulverizer, which rapidly expands after ejecting high-pressure air or high-pressure hot airflow. Due to the large velocity gradient near the nozzles, most of the pulverization occurs near the nozzles. The collision frequency between particles in the pulverizing chamber is much higher than the collision between particles and the wall, which means that the main pulverization effect of jet pulverization is the impact or collision between particles. The control of the particle size of the product by the jet mill mainly depends on the particle size of the raw material, the crushing pressure, the feeding pressure, and the feeding speed. The logical relationship between the jet mill and these parameters is specifically: the smaller the particle size of the raw material, the higher the crushing efficiency, on the contrary, the larger the particle size of the raw material, the relatively low crushing effect. When the crushing pressure and the feed pressure are constant, the product will be finer when the feed rate is reduced, and the product will become coarser when the feed rate is increased. In the case of a certain feed rate, the particle size of the product will be finer when the crushing pressure is increased, and the product will become coarser when the crushing pressure is reduced. Therefore, the particle size control is achieved by adjusting the parameters of the jet mill during the crushing process to achieve different crushing fineness. Before crushing, the relationship between the feed rate and the pressure needs to be measured and then the appropriate crushing parameters are determined to meet the customer's particle size requirements. . The advantage of the jet mill is that the ground material does not produce pollution. After crushing, the compressed supersonic air velocity decreases and the volume increases. It is an endothermic process and has a cooling effect on the material. It is especially suitable for ultrafine grinding. The jet mill uses supersonic airflow to accelerate the particle generation speed, collide with each other or collide with the target to grind the material to achieve the grinding effect. Several evenly distributed auxiliary nozzles are arranged around the main nozzle to accelerate the material particles around the main nozzle to enter the central area of ​​the main stream to obtain a larger collision velocity. A feed nozzle is arranged in the center of the main nozzle, and the fluidized particles in the fluidized bed are directly sucked into the center of the main nozzle to obtain a high collision velocity. There are five types of jet mills used in industry: flat type, circulating tube type, target type, opposing type, and fluidized bed type. Factors affecting the crushing effect of jet mill: It is understood that the pulverization effect of the jet mill is affected by the gas-solid ratio, feed particle size, working fluid temperature, working fluid pressure and crushing aids. (1) Gas-solid ratio If the gas-solid ratio is too small, the kinetic energy of the air flow will be insufficient, which will affect the fineness of the product. On the contrary, if the gas-solid ratio is too high, it will not only waste energy, but even deteriorate the dispersion performance of certain materials. (2) Feed size When crushing hard materials, there are also strict requirements for the particle size of the feed. For titanium powder, it is necessary to control 100-200 mesh when crushing the calcined material; the crushed material after surface treatment is generally 40-70 mesh, not exceeding 2-5 mesh. (3) Working fluid temperature When the temperature of the working fluid is too high, the flow rate of the gas will increase. Taking air as an example, the critical speed at room temperature is 320m/s. When the temperature rises to 480℃, the critical speed can be increased to 500m/s, that is, the kinetic energy increases by 150%. Therefore, increasing the temperature of the working fluid is beneficial to improve the crushing performance. effect. (4) Working fluid pressure The pressure of the working fluid is the main parameter that produces the jet flow velocity, and it is also the main parameter that affects the pulverization fineness. Generally speaking, the higher the working fluid pressure, the faster the speed and the greater the kinetic energy. The technical staff said that this mainly depends on the crushability and fineness requirements of the material. (5) Crushing aid In the pulverizing process of the jet mill, if the appropriate pulverizing aid is added, not only the efficiency of pulverization can be improved, but also the dispersion performance of the product in the medium can be improve
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Classification, principle and characteristics of jet mill

Classification, principle and characteristics of jet mill

发布时间 : 2021-06--24 点击量 : 0
What are the classifications of jet mills? The jet mills used in my country's industry mainly include the following types: spiral jet mills, fluidized bed counter-jet jet mills, circulating tube jet mills, and counter-jet jet mills Machine, target type jet mill. Among these types of jet mills, flat jet mills and fluidized bed counter-jet jet mills are widely used. What are the working principles and characteristics of the jet mill? 1. Working principle: The working principle of the jet mill is: compressed air is dried, and after drying, it enters the crushing chamber through the nozzle. In the crushing chamber, the high-pressure airflow enables the material to be crushed. Afterwards, the coarse and fine materials can be separated under the centrifugal force generated by the grading turbine. The particles that meet the particle size requirements enter the cyclone separator and dust collector and are collected, while the particles that do not meet the requirements continue to be crushed. 2. Performance characteristics: The performance characteristics of the jet mill are mainly as follows: (1) There is a vertical grading device inside, which can adjust the particle size of the product, and the pulverization particle size is good, and the particle size distribution is relatively narrow. (2) It can be used in series with a multi-stage classifier, so that multiple granularity sections can be formed at the same time. (3) The equipment is very convenient to disassemble and assemble, and it is easy to clean. There is no dead corner on the inner wall, so it can be cleaned thoroughly. (4) The operation is airtight, which makes the operation noise low, reduces the generation of dust, and is environmentally friendly. (5) The control system is easy to operate, and the equipment runs safely and reliably.
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Application characteristics of jet mill

Application characteristics of jet mill

发布时间 : 2021-06--24 点击量 : 0
Cyclone pulverization technology is a key method for the production and processing of micro-nano powder. It started in the mining and metallurgy industry and has deep scientific research in the preparation of ultra-fine metal materials or non-metal material powder equipment. In addition, in recent years, the separation of materials and the recycling of solid waste have gradually shown new development potential. According to the structure or working mode of the jet mill, it can be divided into: horizontal disc type (flat type) jet mill, circulating tube jet mill, opposite jet jet mill, target jet mill And circulating fluidized bed jet mill, etc. 1. Horizontal disc type (flat flat type) jet mill The horizontal disc type (flat flat type) jet mill is a popular jet mill that has been used in industrial production. 2. Circulating tubular jet mill Circulating tubular jet mills (column annular jet jet mills) are commonly used for pulverizing ductile and low-strength materials. Generally, they are divided into equal-circular cross-section and variable-cross-section circulating tube types based on the cross section. 3. Counter-jet jet mill The counter-jet jet mill, also known as the inter-collision jet mill or the reverse jet mill, is a machine with high energy efficiency, which is commonly used to pulverize hard, ductile, and viscous materials. 4. Target jet mill The target jet mill is also called a single jet mill, which is commonly used to pulverize coarser materials with high polymer materials, low melting point heat sensitivity, and fibers. 5. Circulating fluidized bed jet mill The circulating fluidized bed jet mill is a new type of jet mill, commonly used in the production of anti-corrosion coatings, urea-formaldehyde resins, pharmaceuticals, skin care products, porcelain, magnetic particle inspection and other materials.
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