Numerical Simulation Of Flow Field In Vertical Roller Mill

Vertical roller mill takes the advantage of material-layer grinding principle and integrates grinding, grading, drying, and air transport of powder, so it is simple flow of low noise, low pollution, convenient operation and high efficiency compared with the ball mill. As a grinding equipment, it is widely used in the cement industry. In the work process, the entire work efficiency of vertical mill is directly affected by powder particles transport and separation efficiency. Knowing well the rule of flow field distribution and the principle of powder separation, and seeking more reasonable geometric parameters of key structure parts in the mill, are playing an important role in improving the efficiency of the overall system.With the numerical simulation analysis for gas-solid two-phase flow field distribution characteristics in a vertical roller mill by computational fluid dynamics software STAR-CCM+with the realizable K-Epsilon model and the Eulerian-Lagrangian approach. Multiple reference frame technology is adopted to deal with the separator rotor’s revolving process of the mill during mesh building.The flow field of vertical roller mill mainly formed by the coupling flow which coupled by circumferential vortex and longitudinal vortex, and became very complex under the influence by wind ring, ash hopper and rotating grinding roller. The interaction of flow around a circular cylinder in a certain angle, sudden expansion flow and boundary layer separation and other flows were coupled to form the complex flow field in the filter-roller region; clockwise and forced vortex was presented in separation area, and between the partial separator stator blades generated the locally secondary vortex, the angle of the blades should be changed at the different position.The angle of wind-guide blade and wind-guide cone are also be intensive studied. Wind-guide blade α=30°is the optimum condition of solid particles transportation and primary separation; wind-guide cone β=30°, the role of the cone to lead the flow is obtain fully embodiment, flows through the wind-guide cone generated enough radial velocity to meet the requirements of reducing the wear of the wall and the size of the vortex.The adjustment radial angle y of stator blades can adjust velocity field distribution in separation region. The numerica simulation results show that the radial angle y changed at the different position along the circumferential direction, and the locally secondary vortex between the partial separator stator blades was eliminated, the tube bending effect caused by the outlet can be effectively avoided.