| Stirred media mill is one of the superfine comminution equipments which have high-energy utilization rate and application prospect Therefore, there are practical purport and spacious market outlook for developing a new-type superfine equipment and doing theoretical studies and experimental analysis for it.The stirred fluid and beads have multidimensional circulation motion and self-rotation for thestirrer rotation in the grinding chamber of a stirred media mill. High intensity motion is caused bymulti-direction displacement of fluid and beads. The powder is comminuted by compression caused by beads gravity and helical turn for rubbing, impacting and shearing.Based on the construction and operation principle of a new-type stirred media mill and combined with the theory of the Continuous Medium Mechanics, the mathematical model of the liquid is founded by using Navier-Stokes equations in the grinding chamber. Its solution approach and numerical calculations are presented. The flow pattern and energy distribution are discussed. According to the numerical calculation, two zones characterized by a high energy density exist. In these zones the local specific energy is larger than the mean specific energy. Based on the steady state of the flow field, the mathematical model of beads is also founded. The position of the trajectory depends on the ratio of bead-to-fluid density, the ratio of bead-to-disc radius and the Reynolds number which describes the operating conditions of the stirred media mill. By means of the beads motion in the calculation domain, the influence of different comminution operation parameters on comminution results is discussed. Those parameters mainly include the beads size, beads density, stirrer angular speed and liquid density and viscosity etc. Those parameters are optimized so that the comminution results are improved. According to the study results, some valuable conclusions are presented. These will provide valuable theoretical reference for the evaluation and optimization of the design of a stirred media mill. |
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