CFD-DEM bidirectional coupling simulation and experimental investigation of particle ejections and energy conversion in a spouted bed

Fluidized bed has gained popularity in the renewable energy industry due to its superior thermochemical conversion efficiency. Investigating the flow patterns inside the fluidized bed is of great importance to obtain detailed knowledge of the energy conversion of biofuel and to further optimize the combustion performance. In this paper, the effect of different inlet gas flow rates on bed hydrodynamics parameters such as bed height, equivalent bubble diameter, and particle ejection were studied by the high-speed photography technology and numerical simulation methods. The results show that changes in the particle bed height and bubble area can be accurately predicted by numerical simulation. The mechanism of particle ejection is varied under different inlet flow conditions. At the low inlet flow rate of 300 L/min, the particles ejected into the freeboard region are only from the bursting bubbles. As the inlet flow rate increases to 400 L/min, the ejected particles are not only from the bursting bubble but also from the bubble wakes. Particle ejection is mainly caused by the bubble expansion rate. These findings could serve as the reference for the optimal design of fluidized beds to achieve higher combustion efficiency.