Effect of fines addition on heat transfer performance in gas-solid fluidized bed: An integrated experimental, simulation, and theoretical study

Efficient heat transfer is crucial in industrial fluidized beds, especially for highly exothermic or endothermic processes. In this study, the influence of adding fines on the heat transfer performance in fluidized bed is investigated through experiments, simulations, and theoretical analysis. Experimental results from a hot/cold-wall fluidized bed show that fines addition enhances the heat transfer performance. Notably, the bed-wall heat transfer coefficient presents a volcano-shaped curve with increasing fines proportion, with a discernible threshold at similar to 25 vol%. Our simulations and theoretical analysis reveal that the improved particle dispersion due to fines addition is responsible for such volcano-shaped phenomenon. Theoretical analysis based on kinetic theory further uncovers that fines addition leads to an increased difference between the solid volume fraction in fluidization state and that in packing state, creating more free-space for particle moving, thereby improving particle dispersion, and thus enhancing heat transfer in fluidized beds.