High shear colloid millCompared to pressure homogenizers, colloid mills are primarily centrifugal equipment with the advantages of simple structure, easy maintenance, and suitability for materials with higher viscosity and larger particles. Its main drawback is also determined by its structure. Firstly, due to centrifugal motion, the flow rate of high shear colloid mills is not constant, corresponding to significant changes in flow rate for materials of the same viscosity. For example, the same equipment can have a flow rate difference of more than 10 times when handling viscous paint materials and thin dairy fluids; Secondly, the surface is more prone to wear, and after wear, the refinement effect will significantly decrease
The working principle of high shear colloid mill is that under the centrifugal force generated by the high-speed rotating rotor, the material is sucked into the working chamber from the top and bottom feeding areas from the axial direction. The weak centrifugal force throws the material radially into the narrow and fine gap between the stator and rotor, where it is subjected to strong high shear colloid mill, hydraulic shear, centrifugal extrusion, liquid layer friction, impact tearing, and turbulence. By centrifugal impact, shear and other forces between the stator and rotor, the material begins to emulsify. The colloid cutting mill uses the high-speed rotation of the homogenizer head connected to the engine to make the material more delicate and promote oil-water mixing. The material is continuously ejected from the radial direction at high speed, changing its flow direction under the resistance of the material itself and the container wall. Along with this, the upward and downward axial suction forces occurring in the rotor area create two intense turbulent flows of flipping. The material goes through multiple cycles and completes the process of dispersion, emulsification, and homogenization.
A high shear colloid mill is a liquid-solid mixture that has undergone pre dispersion and wetting treatment. The material is fed into the mill through a feeding valve at the bottom of the mill by a feeding pump, and the grinding medium inside the mill is stirred by a high-speed rotating disperser. The high shear colloid mill generates strong shear and impact between the solid particles in the material and the grinding medium, achieving the purpose of grinding fine particles and dispersing polymers. The liquid-solid suspension after grinding and dispersion flows out through a separator (screen separation) at the top of the mill.
The high shear colloid mill seal is divided into two parts: the dynamic ring and the static ring. The sealing surface friction pair materials include alloys, cobalt silicon carbide, graphite, glass fiber, ceramics, etc; The base material is made of stainless steel, polytetrafluoroethylene, etc., and its operation is completed through the relative high-speed operation of the dynamic and static rings. The surface accuracy of the dynamic and static rings is very high, usually reaching 0.8mmRa. Considering the structure and materials, before installing the high shear colloid mill seal, it is necessary to check whether there is any damage or crack on the contact surface of the dynamic and static rings, and wipe the surface of the dynamic and static rings clean with a clean soft cloth. When installing, first remove the scale and stains from the installation groove of the static ring, and then place the static ring smoothly into the installation groove. The high shear colloid mill ensures that the static ring is in full contact with the bottom of the groove, avoiding axial shaking of the static ring. At the same time, special attention should be paid to keeping its surface clean at all times during the installation of the static ring. Then slowly place the dynamic ring, gently rotate it left and right, and observe the surface contact between the dynamic and static rings. After confirming that the dynamic and static rings are in tight contact, place the impeller into the locking bolt to complete the installation of the colloid mill seal.
Operating procedures for high shear colloid mill
1. Make preparations before starting.
2. Check if each component is securely installed.
3. The rotation direction of each machine should be in the direction indicated by the arrow.
4High shear colloid millIs the cooling water unobstructed.
5. Triangle belt adjustment is suitable for restarting, and after working for 50 hours, adjust it again.
6. Add grinding medium from the top of the cylinder.
7. Start the feed pump of the high shear colloid mill first, input the material, and wait for the material to be discharged from the top screen before starting the main engine.
8. After a long period of parking, when restarting, the disperser is often "stuck" due to the settling of solid particles and grinding media in the material, especially for viscous materials at lower temperatures. The "braking" phenomenon is particularly serious. At this time, when the jog motor cannot be started, the high shear colloid mill should be assisted by hand turning on the main shaft pulley to input a small amount of solvent that can dissolve and loosen the material before restarting. In short, it should not be forcibly started to avoid damaging electrical appliances and components.
9. If the parking time is long, the dry material on the sieve should be cleaned.
10. The cleaning disperser can only rotate slightly and intermittently, as the high shear colloid mill disperser and grinding medium are prone to wear and breakage during rapid operation in the cleaning solution.
11. When using new grinding media, sieve to remove impurities, fragments, and other foreign objects.
After using or not using the high shear colloid mill for a short period of time, the inner cavity should be cleaned well to prevent rust, and dried with high-pressure air. Choose appropriate cleaning agents according to different materials during cleaning. But it should be ensured that the seal is not damaged (the seal material is nitrile rubber). When disassembling and assembling, attention should be paid to ensuring that all seals are not damaged, installed incorrectly, or lost. When replacing the pulley according to the required speed, first loosen the nut on the motor cover end, turn the tension screw to the left, and push the motor horizontally towards the grinding head to loosen the V-belt. Remove the base cover plate, lay down the machine, then unscrew the nut on the spindle and the fastening screw on the motor shaft, and remove the original pulley.High shear colloid millWhen replacing the required pulley, gently tap it in with a hand hammer, and do not use excessive force to avoid damaging the pulley and damaging the machine's accuracy. After replacement, tighten the machine with nuts and screws, and then gently stand it up.