The Discrete Element Method (DEM) is often employed in various granular and multi-phase flows in industries [1]. Although the DEM becomes an established approach, there is a critical problem from a viewpoint of limit of number of the calculated particles. When the DEM simulation is performed on a single PC, number of the calculated particles becomes at most millions. On the other hand, over billion particles are generally required in industrial powder systems. In order to solve this problem, the authors’ group developed a scaling law model of the DEM, which is referred as coarse grain model [2]. In previous studies, the authors’ group proved the applicability of the coarse grain model in fluidized beds [3,4] and a pneumatic conveying system [2]. In this study, the coarse grain model was applied to solid mixing in a spouted bed. In the calculations, DEM-CFD method was employed to simulate the gas and solid phases in the spouted bed. When the mixing state was examined, Lacey’s mixing index was used in the current study. In this study, 4 cases of the verification tests were performed to show the adequacy of the coarse grain model, namely, original particle system, coarse grain model systems (coarse grain ration was 2.0 and 3.0) and simply triple size particle system (without the coarse grain model). The macroscopic properties such as pressure drop and velocity distribution were in good agreement between the original particle system and coarse grain systems, though double and triple sized particles were used in the coarse grain model systems. As far as the mixing state was considered, it also well agreed in the original and coarse grain model systems. Consequently, applicability of the coarse grain model of the solid mixing is shown through this study.
Acknowledgement
This study was financially supported by the Initiatives for Atomic Energy Basic and Generic Strategic Research by the Ministry of Education, Culture, Sports, Science, and Technology of Japan.
References
[1] M. Sakai, "How should the discrete element method be applied in industrial systems?: A review," KONA Powder and Particle Journal, 33, 169–178 (2016)
[2] M. Sakai and S. Koshizuka, “Large-scale discrete element modeling in pneumatic conveying,†Chem. Eng. Sci., 64, 533–539 (2009)
[3] M. Sakai, H. Takahashi, C.C. Pain, J-P Latham, J. Xiang, "Study on a large-scale discrete element model for fine particles in a fluidized bed," Adv. Powder Technol., 23, 673–681 (2012)
[4] M. Sakai, M. Abe, Y. Shigeto, S. Mizutani, H. Takahashi, A. Vire, J.R. Percival, J. Xiang, C.C. Pain, "Verification and validation of a coarse grain model of the DEM in a bubbling fluidized bed," Chem. Eng. J., 244, 33-43 (2014)
