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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]

• Optimal agitator geometry in dry media stirred mill was investigated. • Orienting stirring arms in the same direction achieved rapid and fine grinding. • Inclined stirring arms achieved rapid grinding with broad particle distribution. • Adhesion of particles in the mill was lower in both optimized geometries. • Collision energies and numbers obtained by DEM explained grinding mechanism. Three different agitator geometries for a dry stirred media mill with a horizontal drum were studied experimentally and by DEM (discrete element method) simulation. Two optimized models, model A with stirring arms oriented in the same direction and model B with inclined stirring arms, achieved more rapid grinding with the lower adhesion of particles to the mill than the conventional stirring arms. Model A achieved the finest grinding with sharpest particle distribution. DEM simulation results suggested that rapid mixing, large collision energy, and a large number of collisions result in rapid grinding. DEM simulations of model A confirmed that the particle collision energy in this model was the highest of the models tested and resulted in the largest energy consumption and the largest temperature increase. In model B, DEM simulation results suggested that collision energy increased locally at the wall and resulted in a local temperature increase at the shaft. The high number of collisions in model B also resulted in rapid grinding but with a broad particle distribution. The decrease of the particle adhesion in models A and B was caused by a decrease in the collision energy between particles and the wall in the normal direction. [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]