Introduction and application of several powder mixers

The introduction and application of several powder mixers powder mixing refers to the process of mixing two or more different components of powder evenly Mixing is also a * step in the whole process of product preparation It is very important that the quality distribution of each component of the mixture is uniform, because the uneven mixture cannot be adjusted in the subsequent process The mixing mechanism of powder is the mutual diffusion, convection and shearing of powder particles At present, the commonly used mixing methods are: three-dimensional mixing, biconical mixing, ball milling mixing and double motion mixing The double motion mixing is to use the rotation of the barrel and the rotation of the internal blade of the barrel (the rotation speed is twice the barrel rotation speed) to force the powder to spread, convection and shear each other at the same time, forming a complex motion, so as to achieve the ideal mixing effect The factors that affect the mixing uniformity are as follows: (1) the powder with coarse particle size has good compressibility, but poor formability; the powder with small particle size has good formability, but poor compressibility, so the proper matching of the size particles can improve the filling type of the powder, improve the compressibility of the powder and improve the sintering performance of the powder However, the larger the particle size difference, the more difficult to mix The fine powder is easy to "bridge" and adhere to each other, which hinders the mutual movement of particles and is not easy to disperse evenly （2） Bulk density (specific gravity) the larger the bulk density difference, the more difficult it is to mix Light powder with small bulk density is easy to float When mixing, it always floats on the top It is difficult to mix it into the components of heavier powder, and it is not easy to mix evenly （3） The fluidity of the powder is poor, and the particles adhere to each other, which is not conducive to the interpenetrating movement and convection of the powder, and is not easy to mix other powders evenly （4） Particle properties particle properties include particle size and particle size distribution, particle shape, roughness, particle density, static charge, moisture content, brittleness, angle of repose, fluidity, agglomeration and elasticity For example, the shape of particles affects the fluidity of particles, and the density difference of particles will cause density segregation in mixing Introduction of several commonly used mixers: at present, the commonly used powder mixers mainly include: three-dimensional mixer, v-mixer, double cone mixer （1） Working principle of three-dimensional mixer: the loading can body is driven by the driving shaft, which makes the compound movement of circular, radial and axial direction, so as to realize the mutual flow, dispersion, accumulation and doping of various materials and achieve the purpose of uniform mixing Advantages of three-dimensional mixer: there is no dead angle in the barrel The disadvantages are: the loading rate is low, generally no more than 60%; for ultra-light powder and ultra-fine powder, it is not easy to mix evenly, it is easy to float above the barrel, and it is difficult to achieve full and even mixing between particles in microcosmic （2） Working principle of v-mixer: Based on the principle that the length of the two cylinder barrels of the mixer is not equal and the rows are not symmetrical, when the mixer is rotating, the materials will be decomposed to combination, from combination to decomposition, Push the material to carry out horizontal communication, and make part of the material flow from one barrel to another with each rotation of the horizontal force In this way, the material is mixed horizontally and radially, and the decomposition and combination are carried out mutually, so that the material can achieve a uniform mixing effect Advantages of v-mixer: when mixing materials with good fluidity and similar physical properties, better mixing effect can be obtained The disadvantages are: when the physical properties of the mixed powder materials differ greatly, the ideal mixture cannot be obtained generally; the energy consumption is large; the particles impact each other and rub against each other greatly, which is easy to change the basic characteristics of the powder components, such as: the particle size becomes smaller and the particle shape changes （3） Working principle of double cone mixer: add the powder into the double cone barrel, with the continuous rotation of the barrel, the powder material in the container carries out complex impact movement, to achieve uniform mixing Advantages of double cone mixer: it can realize fast mixing between powders The disadvantage is: when the rotating speed is too slow, the material is easy to roll in layers, unable to mix quickly and effectively, and easy to form spherical agglomerates Application of different mixers in different fields: (1) 3D mixers are widely used in medicine, chemical industry, food, feed, pesticide and other industries It is not only suitable for the mixing of ordinary powder materials, but also for the mixing of oil-containing, sugar containing, high viscosity, flammable, explosive, temperature curing, temperature softening materials Such as medicine, powder coating (premixed and finished product mixed), leveling agent, food additive, etc., and can be used with the production line （2） V-mixer v-mixer is suitable for the mixing of more than two kinds of dry powder and granular powder materials, especially for the micro additives It is widely used in pharmaceutical, chemical, food, plastic, cosmetics, ceramics, metallurgy and other fields （3） Double cone mixer the cone mixer is suitable for mixing solid and solid, solid and liquid, liquid and liquid It is widely used in chemical industry, dye, petroleum, metallurgy, building materials, rare earth and other fields The conical mixer will not overheat the heat sensitive materials, feed or grind the granular materials, and will not separate the chips when mixing the materials with great difference in weight and different particle size.