Analysis Of The Mixed Airflow Movement In Vertical Mill Cavity

Vertical mill is a kind of production equipment integrated by the roles of grinding,crushing, drying, and transport with the advantages of good energy-saving effect, greatability of grinding, high efficiency, small occupied area, light weight, efficient drying, longservice life and large abrasive particle size which has been found an increasingly wideapplication in social production such as cement, electric power, metallurgy, chemicalindustry non-metallic mineral industry, etc. However, there are a lot of problems inproduction, for example, violent vibration of grinding machine, low efficiency, excessivescale of grinding resulting in more energy-consuming features and low output. Theseproblems remain to be solved. The motion analysis of mixed flow in the vertical grindingcavity is an impactful method to deal the trouble of low powder-transporting and–selecting efficiency of vertical mill.The internal structure of vertical mill cavity is complex, and the coupling andtransport of powder particles are completed by the mixing airflow in it. Thus, its flow fieldis directly related to the production efficiency and the operating stability of the vertical mill.In this paper, a type of large vertical mill cavity is the study object, and the numericalsimulation of computational fluid dynamics is processed by the workbench platformanalyzing the influence of the internal structure of vertical mill on movement of mixingairflow in it. The study mainly involves the following three parts:Firstly,analysis model of mixing airflow motion in the vertical mill is established bythe3-D mechanical designing software SolidWorks. According to the principle ofcomputational fluid dynamics, the following suggestions should be paid attention to:1)The mixing airflow movement area should be built as the entity model.2) The area that themixing airflow won’t cover is supposed to be removed.3) Considering the convenienceand practicability of the mesh without affecting the motion of the airflow, small size, roundcorners and chamfering are better to be smoothened or removed. Secondly,the motion model is processed by the workbench platform and the boundaryconditions are named following by regulating the global and local grid parameters meetingthe demand of the Fluent software for numerical analysis.Finally,according to the principle of the vertical mill and the computational fluiddynamics, the Mixture model of multiphase flow model of Fluent software and thestandard k-epsilon model in the turbulence model are adopted to analyze the flow field ofmixing flow in the vertical grinding cavity. The study indicates that the air flow in thevertical grinding chamber spirals from the bottom of the chamber under the action ofrotating mill, roller and the inner wall. And it is coupled with fine powder particles in millwind ring exchanging a lot of energy to filter the particles for the first time, with most ofthe airflow with fine powder particles getting into the grinding chamber at the top of thechamber for the final selection of particles. The mixing flow is intensely turbulent near themill and roller resulting in the eddy current phenomenon. With the rise of airflow, velocityvector of the mixing flow is regular, and the velocity vector at the edge of the classifierwall area are uniform with the tangent direction benefiting screening of classifier. Thepressure is biggest in the air intakes, while it is smaller in the materials import and windring. The condition of material circulation in grinding cavity can be judged from thedifferential criterion, and the stable differential shows that the input is consistent with theoutput. Reasonable cycle of grinding materials could avoid vibration of the vertical ground.In the process of production, it is critical to control the reasonable air input and thegrinding materials import to guarantee the stability of grinding chamber pressuredifference to realize efficient and continuous continuity production.