CFD-DEM Simulation on Gas-Solid Separation and Sphere Packing Behaviors in a Storage Bin of the Small Absorber Sphere System

Abstract The small absorber spheres system is one kind of shutdown system in the pebble-bed High Temperature Gas-cooled Reactor (HTGR or HTR). Vertical pneumatic conveying of small absorber spheres in pebble-bed HTGR is a special application of pneumatic conveying technique. The whole process consists of several sub-processes, e.g., the granular discharge from the sphere storage bin into the boring, granular discharge from the side reflector boring into the feeder, particle entrainment in the feeder, sphere conveying in the transport pipeline, and gas-solid separation in the storage bin. The Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) coupling simulation has recently been extended and used to investigate particle vertical conveying in the small absorber sphere system in our previous work. In this study, we further investigate the gas-sphere separation and sphere packing behaviors in a storage bin of the small absorber sphere system by CFD-DEM coupling simulation, to make a better understanding of the gas-solid flow and particle flow behaviors in the small absorber spheres system. The influence of operation parameters is considered, including gas velocity, particle velocity and solid flow rate. The effect of gas and solid properties are also considered, including media type (high pressure Helium and ambient air) and friction coefficient of the sphere and wall. Attention is paid to the sphere motion behaviors and heap up characteristics of the spheres in the storage bin, to gain more knowledge of the evolution of heap up surface for the design of sphere level indicator.