What is High-shear Homogenizer?

The high-shear homogenizer uses the high-speed rotation of the rotor to produce strong shearing effect to break the particles. The high-shear homogenizer has the following advantages compared with the separated pressure homogenizer. First, the high-shear homogenizer has low energy consumption because of the low working pressure of the high-shear homogenizer. Practice shows that the energy consumption is only 50% of the high-pressure homogenizer. Secondly, the material requirements of the high-pressure homogenizer are not as high as those of the high-pressure homogenizer, and the service life of the parts is higher than that of the high-pressure homogenizer, so high shear The manufacturing cost of the homogenizer is low. Third, the high-shear homogenizer has a wide range of applications and a large processing capacity. It can be used for high and low viscosity fluids, and can also be used for homogeneous or immiscible liquids containing short fiber liquids. Liquid-liquid mixing. The type of high shear homogenizer can be divided into batch type and continuous type.

(1) Intermittent high-shear homogenizer

Figure 7-22 is a schematic diagram of the structure of a high-shear homogenizing pot, and Figure 7-23 is a schematic diagram of its work. The homogenizing head is composed of a stator and a rotor. The gap between the rotor and the stator is very small, generally less than 1mm. When the rotor rotates at high speed, negative pressure is formed inside the homogenizing head. The liquid is sucked in from the lower part of the homogenizing head. Under the action of centrifugal force, the liquid is thrown to the inner wall of the rotor and enters the gap through the holes or slots in the wall. The strong shearing, impacting and grinding action enables the material to be crushed and refined in an instant, and finally the liquid is ejected through the hole or groove on the stator, which is mainly shearing for the homogenization of the material.

(2) Continuous high shear colloid mill

A tiny gap is formed between the colloid mill stator and rotor and can be adjusted. When working, the material passes through the annular gap between the stator and the rotor. Because the rotor rotates at high speed, the material attached to the surface of the rotor has the highest speed, while the speed of the material on the stator surface is zero. A great speed gradient is generated during the process, and the material is crushed, dispersed, ground, refined and homogenized by the combined force of shear force, friction force, impact force and high-frequency vibration.

The colloid mill has two structural forms: horizontal and vertical. The horizontal arrangement of the shaft of the colloid mill is called a horizontal colloid mill; the vertical arrangement of the shaft of the colloid mill is called a vertical colloid mill. The structure of the horizontal colloid mill is shown in Figure 7-24. The gap between the stator and the rotor is generally 50~150um, and the size can be adjusted by the horizontal displacement of the rotor. The speed of the rotor is 3000~15000r/min. Horizontal colloid mill is suitable for materials with low viscosity. The colloid mill is mainly composed of a feed hopper, a shell, a stator, a rotor, and a regulating device.

(1) Stator and rotor. Both stator and rotor are made of stainless steel, and the hardness after heat treatment is required to reach 70HRC. The shape of the rotor and the inner cavity of the stator are both truncated cones, and the taper is about 1:2.5. There are teeth on the working surface, and the teeth lines are arranged from coarse to dense according to the direction of material flow, and have a certain inclination. In this way, the degree of refinement of the material is determined by factors such as the inclination of the tooth pattern, the width of the tooth, the gap between the teeth and the residence time of the material in the gap.

(2) Adjusting device.The colloid mill can be adjusted according to factors such as the nature of the material, the degree of refinement and the discharge. When adjusting, by turning the adjusting handle, the adjusting ring drives the axial displacement of the stator to change the gap, ranging from 0.005 to 1.5mm. In order to avoid collision between the stator and the rotor, a limit screw is arranged under the adjustment ring, and the adjustment can no longer be carried out when the adjustment ring hits the screw. Due to the high speed of the colloid mill, in order to achieve the ideal homogenization effect, the material generally needs to be ground several times, which requires a backflow device.

The backflow device of the colloid mill uses the discharge pipe to be changed to the feed pipe, and a butterfly valve is installed on the pipe, and another pipe is connected to the inlet of the butterfly valve just before the pipe. When multiple cycles of grinding are required, close the butterfly valve and the material will flow back repeatedly. When the requirements are met, the butterfly valve can be opened to discharge.

For the homogenization and grinding of heat-sensitive materials or viscous materials, it is often necessary to remove the heat generated in the grinding in time to control the temperature rise. Water cooling can be provided through cooling liquid holes in the periphery of the stator.

Reference: https://www.chinakedun.com/products-9-21-p.html