Meso-scale structure is key to gas-solids fluidization modeling.Traditional two-fluid model is not suitable for describing multiscale behavior in fluidized beds.In contrast

the structure-dependent multi-fluid model (SFM)

which is based on the energy-minimization multi-scale (EMMS) method

takes into account the heterogeneous structure within local space (or

sub-grid structure) and hence its prediction is only weakly dependent on grid resolution

reducing greatly computing load.Based on the structural characterization of SFM

we proposed an EMMS based mass transfer model to explain why literature data scatter up to several orders of magnitude.These models were integrated into a whole set of multiscale computational fluid dynamics (CFD) method

with which we predicted the typical S-shaped axial profile of volume fraction and further revealed the "choking" mechanism and the reason why scale-up of a fluidized bed was so difficult.Currently

3D

whole-loop

transient

reactive simulation of an industrial circulating fluidized bed could be made possible.In prospect

to realize the shift of research mode from simulation to virtual process engineering

we still need breakthrough in understanding meso-scale structures.