(133d) Large-Scale DEM-CFD Method for an Industrial Fluidized Bed

Numerical simulations of fluidized bed are often performed for the better understanding of complex phenomena. In these numerical simulations, Eulerian-Lagrangian approach [1] is often employed, where solid and fluid phases are modeled by discrete element method (DEM) and computational fluid dynamics (CFD), respectively. Indeed, the DEM-CFD method is applied to various solid-fluid coupling problems. Adequacy of the DEM-CFD method is proven not only in a gas-solid flow system such as a fluidized bed [2,3] but also a wet ball mill [4,5]. Although the DEM-CFD method seems to be established, there is a couple of critical problems such as substantial limit of number of calculated particles and difficulty for stable computation for a gas-solid flow in a complex-shaped boundary. In order to solve these problems, we develop a new methodology that is referred to as DEM-CGM-CDF-SDF-IBM method. In the DEM-CGM-CFD-SDF-IBM method, signed distance function (SDF) [6] and immersed boundary model [7] are used for boundary wall of solid and fluid phases. The coarse grain model (CGM) [8] of the DEM is employed as the scaling law model, where a model particle represents a group of original particles. To show adequacy of the DEM-CGM-CDF-SDF-IBM method, a validation test is performed in a fluidized bed. In the simulation, 200,000 spherical particles whose density, original particle diameter and coarse grain ratio are, respectively, 2500 kg/m³, 0.1 mm and 5. Experiments are performed under fair conditions of the numerical simulations. It is shown that the DEM-CGM-CDF-SDF-IBM method can simulate the bed height and pressure drop obtained from the oroginal system accurately through the validation test. Consequently, we conclude that the DEM-CGM-CDF-SDF-IBM method can simulate industrial scale fluidized bed, and hope that our method becomes standard in numerical simulation method in industrial systems.

References

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