Research On Classification Of Superfine Powder By Turbineclassifier

With the extensive application of superfine powder, there are higher requirements for the purity, size and other aspects of superfine powder, as well as the equipment of crushing and classification. This paper designed a high speed mechanical impact crusher for crushing experiment material. The effects of the operating parameters of turbine classifier and the rotor cage blades number of turbo air classifier on the flow field of classifier were studied by using the computational fluid dynamics software (Fluent). To study the effects of operation parameters on the classification performance by the classification experimental of crushing power. The main research and results of the thesis are as follows:1. The high speed mechanical impact crusher was designed by using the impact crushing principle. Using the counter-rotating of the two crushing plate increased impact velocity to improve crushing effect. The wear-resistant ceramic liner of internal structure of crusher was used to ensure the purity of the product. The suitable feed particle size of the crusher was 2～3mm and the crushing size was about 50～150μm.2. The numerical simulation of gas-solid two phase flow was used to analysed the flow state of the internal flow and materials in the FTW-350 type of the turbine classifier. The variable of the operation parameters in turbine classifier was one of the speed of classifier wheel, feeding speed and outlet pressure, the rest of the two operating parameters remain unchanged.The distribution of dynamic pressure, the turbulent kinetic energy, tangential velocity, radial velocity and axial velocity were analysed. The results showed that:within the speed range of 6000-7000r/min, the greater the the classifier wheel speed was, the more uniform to the dynamic pressure, turbulence kinetic energy and the velocity distribution were in the flow field. This showed that the flow field is relatively stable.When the feeding speed increased, the pressure difference between the classification area and fine powder outlet raised, and the turbulent kinetic energy and the velocity decreased. The increasing amount of the outlet pressure, the turbulent kinetic energy and the velocity was small when the outlet pressure increases in a low range. The pressure and each component velocity of the flow field increased sharply and the distribution was not uniform when the outlet pressure is increased to -3500Pa. So it is not conducive to the stability of flow field.3. The kaolin powder prepared by the new crusher was used for the classification experiment in the FTW-350 type of the turbine classifier, and the particle size of the product was tested by the laser particle size analyzer to get the distribution curves of the cumulative volume distribution and frequency. The results showed that:the increasing of the classifier wheel speed is good for enhancing the content of fine powder and reducing the distribution range of particle size. But the effect on classification size was smaller when the rotational frequency increases to 75Hz. The raise of the feeding speed within a certain range can improve the content of fine powder, and the influence was smaller in a high speed.4. For the single-phase flow state in turbo air classifier, the dynamic pressure, tangential velocity and radial velocity of flow field were analysed under 12,24,36,48,60 and 72 six groups of blades number. The analysis showed that:with the number of blades increased from 12 to 48, the uniformity of the pressure and velocity distribution of the classification flow increased, and the vortex flow decreased continuously.The airflow vortex of the blade clearance was relatively small when the blades number was 48. The dynamic pressure and velocity distribution of flow field was more uniform than the others. It showed that the flow field was relatively stable to achieve the optimal classification results.