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Grinding process is a unit operation with various purposes, such as milling, dispersion, and surface modification, and is an indispensable process in various industrial fields, such as food, pharmaceuticals, and cosmetics. Solid feed materials for milling have different physical properties such as strength, hardness, and particle size. Therefore, various types of mills are used depending on the material and the purpose of the milling. A cutter-type disk mill consists of disk-shaped rotating blades and fixed blades, and the rotating blades cause shearing force to the raw material. Therefore, they are used to crush solid materials such as resins, coffee beans, and rice, which are difficult to crush with a simple impact. Cutter-type disk mills are considered particularly effective for grinding plastics. However, it is necessary to optimize the geometry and operating conditions of the mill. This study aimed to evaluate the grinding performance of different blade geometries and particle physical properties in the cutter-type disk mill and to identify the melting factors of resins in the mill. To calculate the effect of the blade geometry and particle properties, the discrete element method (DEM) coupled with the computational fluid dynamics (CFD) and a breakage model was employed to simulate plastic particle breakage. Simulations were performed under conditions where the geometry of the grinding blade and particle physical properties were different. When using the model with angled blades, particle distribution had specific peak position and particles were intensively grinded in this region. On the other hand, the model with radial blades did not have a distribution peak and resulted in strong force and rapid grinding. In addition, it was confirmed that materials which likely to melt in the mill changes depend on the blade shape. Our results show that it is possible to evaluate the grinding performance under the different equipment conditions and with different particle properties, as well as the particle behavior inside the equipment, and that it is effective in improving the process. [Display omitted] • The DEM-CFD with a breakage model was applied to a cutter-type disk mill. • The effect of blade shapes and particle properties on grinding performance was evaluated. • Blade shape greatly affects the particle behavior in the mill. • Materials which tend to melt changes depend on the blade shape. [ABSTRACT FROM AUTHOR]

• Dispersion performance in bead mill investigated by DEM-CFD simulations. • Correlation between experimental and simulation results investigated. • High-collision energy during bead milling caused sample re-agglomeration. • High collision energy during bead milling should be reduced for good dispersion. • DEM-CFD is an effective tool for appropriate design of bead mills. A bead mill is commonly used to produce nanomaterials. The design of the bead mill rotor is an important factor in efficient nanomaterial production to avoid re-agglomeration. We investigated the effect of bead-mill rotor shape on the dispersion state using experimental tests and the discrete-element method (DEM) coupled with computational fluid dynamics (CFD) simulations. Experimental results using TiO 2 in the bead mill showed that the high rotor rotation speed caused TiO 2 particles re-agglomeration, and a sharp particle-size distribution was obtained by dispersion with a mill with a wide gap between the rotor and the chamber. To evaluate the dispersion performance, bead collisions were analyzed using the DEM-CFD simulation. The simulation results indicated that an increase in bead-collision energy lead to damage of the TiO 2 primary particles and re-agglomeration at a high rotation speed. A uniform dispersion was achieved when the frequency of high-energy collision between the particle and wall decreased and a small standard deviation of the collision energy frequency was obtained by the mill with a wide gap. These simulation results correlate with the experimental results. Therefore, this study shows that the DEM-CFD simulation could contribute to an appropriate rotor design for uniform dispersion. [ABSTRACT FROM AUTHOR]

[Display omitted] • The DEM-CFD with a breakage model was applied to a cutter-type disk mill. • The effect of the blade angle on grinding performance was evaluated. • The blade angle of 45° enabled the highest grinding performance. • The DEM-CFD with a breakage model is effective for evaluating the disk mill. In the recycling process of plastics, grinding is commonly employed as a pre-treatment method to facilitate molding by increasing the specific surface area. A cutter-type disk mill that mainly causes shear forces is expected to be the most efficient for grinding plastics. However, it is necessary to optimize the geometry and operating conditions of the mill. This study aimed to evaluate the grinding performance of different blade geometries in the cutter-type disk mill. To optimize the blade geometry, the discrete element method (DEM) coupled with the computational fluid dynamics (CFD) and a breakage model was employed to simulate plastic particle breakage. The simulations showed that the highest grinding performance was achieved with a grinding blade angle of 45°. Depending on the angle of the grinding blade, the effects of the power acting on the grinding blade and the force acting on the particles varied. According to these results, an appropriate blade geometry in the cutter-type disk mill can be proposed for grinding plastic. This study demonstrated that the DEM-CFD simulations are effective for evaluating the grinding performance and optimizing the blade geometry of the cutter-type disk mill. [ABSTRACT FROM AUTHOR]