CFD-DEM modelling of mixing of granular materials in multiple jets fluidized beds

Jetting fluidized beds are widely used in industries for mixing of granular materials. The mixing efficiency is affected significantly by the number of jets and their locations. In this work, discrete particle model is used to simulate fluidized beds with different jet numbers, and the results are validated by physical experiments. Cases with different jet numbers (varying from one to five) but the same gas flow rates are compared in terms of the maximum bed pressure drop, bed height, mixing index, particle velocities and contact number. The results show that different jet numbers result in different flow patterns, which severely affect the mixing efficiency. The mixing efficiency in the one-jet case (spouted-bed) is 1.5–3 times higher than other cases due to a higher jet velocity and umbrella-type flow pattern. For the multiple jets, bubbles and vortex can form and promote particle mixing but not as efficient as the case of one jet. However, particle contacts in multiple jet cases is more uniform than the one-jet case. This implies that from the perspective of particle heat transfer, multiple jets can behave better than one jet.