Introduction to the working principle of high speed disperser
High Speed Disperser1. Overview
High speed disperser, as the name suggests, its main working part is the high speed operation of the dispersion plate, and the most commonly used stirring part of the high-speed disperser used in our daily production is the serrated disc impeller (commonly known as the dispersion disc, dispersion blade, etc.), the dispersion disc is driven by the high-speed rotating dispersion shaft.
The high-speed rotation of the dispersion disc causes the paint paste in the cylinder to show a rolling circulation, and the power-sufficient equipment will produce a large whirlpool. The powder or pigment floating on top of the paint paste will soon descend to the bottom of the vortex with a spiral. In the area of 2.5-5 cm at the edge of the dispersion disc, a turbulent flow zone is formed. In this area, the powder particles are subjected to strong shear and impact, allowing them to quickly disperse into the paint paste. Outside this area, the upper and lower two streams of the stroke allow the paint paste to be fully circulated and turned. If there is a laminar flow state under the dispersion disc, the interaction between the liquid layers at different speeds is called the viscosity shear force, which can play a good dispersion effect.
In summary, the high-speed dispersing machine plays both mixing and dispersing functions. In the initial stage of the high-speed disperser operation, the pigment is still piled on the paint, which is suitable for mixing at low speed, first let the vortex suck the powder to the bottom, which can effectively prevent dust flying and material splashing, and then increase the speed and increase the dispersion capacity. When the circumferential velocity (i.e. linear velocity) at the end of the dispersion disc must reach more than 20 meters per second, the material can obtain a more satisfactory dispersion effect. Only when dispersing the expanded paint paste, the linear speed can be appropriately reduced, about 15 meters per second. However, the linear velocity of the dispersion disk can not be too high, too high will lead to material splashing, all over the ground, and will make the dispersion disc too much exposure to the outside leading to mixed air, destroying the laminar flow state that has been formed below the dispersion disc to reduce the dispersion efficiency, low efficiency not to mention waste of electricity. Therefore, we generally recommend that customers use the speed to control to the right time, do not blindly pursue the higher the speed is the better, etc., it is recommended that the line speed be controlled in the range of 25-30 meters per second.
2. Conditions for generating laminar flow in the lower part of the dispersion disc
In order to allow the lower part of the dispersion disk to reach the laminar flow state, on the one hand, the linear velocity of the dispersion disc cannot be excessively increased, on the other hand, the viscosity of the material should be appropriately increased, and the position of the dispersion disc should be reduced. Under the conditions of our outlet speed and material viscosity, we can know that the dispersion disc should be inserted at a reasonable depth, or under the condition of knowing the linear speed of the dispersion disc and the insertion depth of the dispersion disc, we know how to formulate the reasonable viscosity of the material.
3. The size and position of the dispersion plate, and the appropriate size of the dispersion cylinder
The diameter of the dispersion cylinder and the diameter of the dispersion disc and the reasonable position of the work directly affect the dispersion effect and dispersion efficiency, normal we recommend that the customer disperse the dispersion disc appropriately offset the center of 3-5 cm in the early stage of dispersion, and then the powder can be adjusted to open the high speed when the powder is sucked into the lower laminar flow. In actual production, we can adjust the height of the feeding and the insertion depth of the dispersion disc according to the viscosity of the material and the speed of the dispersion shaft. In the process of high-speed operation of the dispersion disc, the material will form a deep whirlpool, to prevent the material from spilling out of the edge of the dispersion cylinder.
The dispersion disc has a reasonable ratio to the diameter of the dispersion cylinder, and the purpose is to make the material circulate better. Even with the same line speed, in general, the effect of small dispersion discs is worse than that of large dispersions. However, the power consumed by the large dispersion disc is much larger than that of the small dispersion disc, the same power 22kw high-speed disperser, the dispersion disc with a diameter of 300mm and the dispersion disc with a diameter of 350mm The effect and energy consumption are very different, because the stirring power is proportional to the 5th power of the diameter of the dispersion disc and the cubic of the speed. In order to make the circulation better, the dispersion cylinder generally does not have a baffle, and there should be no dead angles, so it is a saucer bottom as well.
Generally speaking, the instruction manual of the high-speed disperser requires the dispersion disc to be placed in the center position, because from a purely mechanical point of view, this is indeed no problem, because the dispersion shaft bias will bring additional loads to the shaft, and will increase the power consumption, one is power consumption, and the other is that the motor loss is too easy to cause frequency conversion protection. However, from the perspective of chemical processes, proper biasing of the shaft is a good thing, which is beneficial to improving the dispersion efficiency, and can also prevent the liquid from swirling, reduce the depth of the vortex, and improve the circulation effect. Therefore, as I said earlier, the distance of shaft bias should not be too large, generally not more than 2 times the diameter of the dispersed shaft, to avoid the operation is not affected as well.