The principle and characteristics of sand mill
The sand mill is a wet stirring and pulverizing equipment, which can be used for primary or secondary pulverization of pigment-type titanium dioxide. The grinding body is divided into upper and lower parts. Container, top diameter 1981mm, height 762mm. The bottom of the sand mill is equipped with a feed pipe of ?102mm, and five impellers are installed on the drive shaft. The impellers are made of polyurethane rubber. Each impeller is 445mm in diameter and 38mm in thickness. When the impeller rotates, the slurry produces a rotary motion, and the impeller is driven by a 47.5-horsepower motor.
When working, the calcined product is slurried with water to a concentration of about 600g/L containing TiO2, and an appropriate amount of dispersants such as sodium hexametaphosphate and sodium silicate are added. Put 1t of sand grains in the container, and the sand grains are preferably made of glass beads, SiO2, ZrO2 and Al2O3, etc. The sand grain diameter is between 250 and 2500 μm. The impeller speed is 560r/min. The TiO2 slurry enters from the feeding pipe, and the feeding volume per hour is 1.8m3. The ratio of sand to slurry, which is usually the same volume, can also vary between 35:65 and 65:35.
As the slurry rises into the upper container, the water is fed through the water inlet pipe to adjust the slurry concentration to 450g/L. Since the upper container is conical, the flow rate gradually slows down during the upward movement of the slurry, and the sand particles gradually settle down and return. inside the container. The slurry finally overflows from the overflow pipe, and the sand content in the slurry is 10-6g/L. This method can avoid the problem of screen breakage caused by the separation of mortar in general sand mills. Four vertical baffles with a height of 280mm are installed in the upper container of the sand mill to reduce eddy currents and make the separation effect better.