1. zero pollution conditions Based on the dispersing mechanism of the sand mill, the wear and tear strength of the micro bead on the crushing cavity and the mixing device in the cavity is also very strong when the particles are impacted and rubbed, so it is necessary to ensure that the material of the cavity and the agitator must have super high wear resistance; otherwise, the material is polluted because of its wear and tear. The service life is very short, and more importantly, the pollution source causes the dispersed raw materials to reunite again, so that the nanometer fineness and normal distribution requirement can not be achieved. 2. working condition requirements of low temperature Based on the dispersing mechanism of the sand mill, when the micro bead and material particles in the grinding chamber collide and friction each other, it will produce high heat. If the heat can not be taken away in time, the material will reunite again at a higher temperature, so that the nanoscale fineness can not be reached. 3. microspheres using the minimum size limit Generally speaking, the smaller bead grinder, the smaller the microbead used, the increase in the number of microspheres is increased, and the contact point of the geometric multiplier is increased, and the higher the grinding and dispersing efficiency is, and the smaller the larger the microspheres are, the lower the dispersion efficiency of the nanoscale grinding is, usually the sub micron grade is generally made. 0.2-0.6mm microspheres were used for grinding and dispersing, and used for nano scale grinding and dispersing of 0.05-0.1 beads. To supplement the energy shortage of microbeads, it can be supplemented by increasing rotational speed. Therefore, the speed of the nanoscale sand mill is usually several times that of the traditional sand mill. 4. using large flow circulating grinding and dispersing process In order to use the most reliable droplet separation device, not only the microspheres can not block the separator, but also the liquid paddle through the separator can be quickly passed through the separator, so that the smaller nano material particles will not absorb the excessive impact energy in the crushing chamber, and the temperature of the grinding cavity is reduced. 5. reasonable distribution of high energy density and energy density In the crushing chamber of the sand mill, the concept of energy density is introduced into the impact and friction strength of the microsphere. The energy density refers to the broken kinetic energy of the particles in a unit volume, which is provided to the material particles. The higher the energy density is, the higher the crushing efficiency is, but the rational distribution of the energy density is particularly important when the material particles change from submicron to nanoscale. In general, the best nanoscale grinder in the grinding chamber is regular in energy density. It regularized the area of high energy density to smash the particles with high energy density, to crush the smaller particles in the area with low energy density and to reduce the layers. Nanoscale particles with a very narrow distribution. The KLLn series vertical double shaft sand mill made by our company has made this happen.