At present, the linear speed of shearing homogenizers commonly used in China is mostly 10～25 m/s. Practice has proved that its homogenization effect is not ideal. High-speed emulsification homogenizer refers to a shearing homogenizer with a linear speed of 40-66 m/s. Its main working parts are the stator and rotor with one or more stages of meshing with each other, and each stator and rotor has several layers of ring gears.
Working principle: The rotor has blades rotating at high speed to generate a strong centrifugal force field, forming a strong negative pressure zone in the center of the rotor, and the material liquid (liquid-liquid or liquid-solid phase mixture) is sucked from the center of the stator and rotor under the action of centrifugal force. , The material spreads from the center to the surroundings. In the process of spreading to the surroundings, the material is first stirred by the blades, and sheared in the narrow gap between the end of the blades and the inner side of the stator gear ring, and then enters the inner ring rotating tooth and the fixed tooth. In the small gap, under the action of mechanical force and hydrodynamic effects, great shear, friction, impact, and mutual collision and friction between materials are generated to break the dispersed particles or droplets. As the linear speed of the rotating gear gradually increases from the inner ring to the outer ring, the crushing environment continues to improve, and the material is subjected to more and more intense shear, friction, impact and collision during the movement of the outer ring, and the more it is crushed. The finer it comes to achieve the purpose of homogenization and emulsification.
At the same time, in the negative pressure zone in the center of the rotor, when the pressure is lower than the saturated vapor pressure (or air separation pressure) of the liquid, a large number of bubbles are generated. . At the moment of collapse, a micro jet is formed in the center of the bubble. The jet velocity is high and the strong pressure wave can crush soft and semi-soft particles, or disperse hard agglomerated fine particles.
From the analysis, it can be seen that the mechanism of the material being homogenized in the stator and rotor cavity is more complicated. The author believes that shear plays a leading role, followed by cavitation.
From the above analysis, it can be seen that the high-speed emulsification homogenizer is mainly due to the high shear effect generated by the relative high-speed movement between the stator and the rotor, and at the same time, it is accompanied by a strong cavitation effect to disperse, refine and homogenize the material particles; The high-pressure homogenizer mainly relies on the strong and sufficient cavitation effect and turbulence produced by the high-pressure fluid to break the particles in the dispersed phase of the fluid to achieve the purpose of homogenization. It is not difficult to understand that due to the extremely strong cavitation effect, the high-pressure homogenizer is more suitable for processing soft and semi-soft granular materials; research has found that the most effective force field for fiber pulverization is shear force and grinding force. At room temperature, the impact force is powerless to the fiber, and the high-speed emulsification homogenizer can produce a strong shear and grinding effect on the material. Hard granular materials.
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