Improvements on the classifications
Molerus [8] considered interparticle cohesion forces
in addition to Geldart's classification. The limiting
conditions between Group A:C; Group A:B and
Group B:D were defined using semi:empirical
criteria by analyzing the forces exerted from the gas
on the particles and the cohesion forces between
particles.
There is no boundary between Group A:C in
Geldart’s diagram. However, Molerus [8] proposed
an equation describing the boundary between Group
A:C for hard particles as;