Extension of Geldart classification based on the magnitude of interparticle forces

The boundary between Geldart groups A and C is formulated based on the magnitude of interparticle forces (IPFs). It was postulated that the transition from group A to C happens if the interstitial gas velocity at minimum fluidization exceeds the particle terminal velocity. The proposed model led to novel equations correlating the magnitude of IPFs and the corresponding agglomerate size at this boundary to the bed voidage at minimum fluidization. The proposed boundary was validated by experimental data from literature, including those under an enhanced level of IPFs. The transition between Geldart groups A and C typically occurs when minimum fluidization voidage is 0.6-0.7, corresponding to IPFs about an order of magnitude greater than the weight of a particle and agglomerates about three times larger than the particle size. A comparison of the weight of particles at the boundary between groups A and C and between groups A and B suggests that IPFs are about an order of magnitude smaller than the weight of a particle for the latter. It was shown that, for a given material, particle diameter at the boundary between Geldart groups A and C is proportional to the cube root of interparticle forces. The variation of the boundary between groups A and C with IPFs were presented in a 3D graph.

Automated summary

The boundary between Geldart groups A and C is determined based on the magnitude of interparticle forces. Experimental validation shows that the agglomerate size increases with the increase of interparticle forces, supporting the proposed boundary.