(267h) Validation Study on an Eurerian-Lagrangian Method in a Circulating Fluidized Bed

A circulating fluidized bed (CFB) is one of typical gas-solid flow systems in chemical engineering. For better understanding of mechanism in the CFB in industries, numerical simulation is indispensable. In the CFB, the flow characteristics is regarded to be extremely complex, since dilute and dense solid particle regions are appeared simultaneously. An Eurerian-Lagrangian approach becomes promising when the complex gas-solid flow is numerically simulated, where solid and gas phases are modeled by the discrete element method (DEM) and computational fluid dynamics (CFD). Although the DEM-CFD method was well employed in the gas-solid flows, it had critical problems from a viewpoint of restriction of calculated particles and arbitrary shaped boundary. In order to solve these problems, we applied a coarse grain model of the DEM, sign distance functions (SDF) for wall boundary model in the DEM and immersed boundary method (IBM) in the CFD in the existing DEM-CFD model. This numerical approach makes it possible to simulate a complex shaped system such as the CFB with a simple algorithm. In this study, validation tests were performed to show adequacy of the new computation technology. The validation system was quite large, namely, number of the solid particles were about 4 x 10⁸. Through the validation tests, particle spatial location and pressure drop were shown to agree between the simulation and experimental results. Consequently, we conclude that our method could simulate large-scale circulating fluidized bed accurately.

Acknowledgement: This study was financially supported by JSPS KAKENHI Grant Number JP17H03451.