The elutriation of fine particles (Group C or A particles in Geldart's classification) from a fluid bed of mixed fine and coarse particles is investigated in a steady state. Al(OH)(3) and alumina and TiO2 powder of 0.5-32 mum were used as fines. FCC, alumina, Al(OH)(3), limestone, silica sand, SiC particles of 44-97 mum were used as coarse particles. The paper investigates the effect on the elutriation rate constant of both fine powders and coarse particles (i) of the weight fraction of Geldart C powders in the bed, (ii) of the superficial gas velocity, and (iii) of the size of C powder and size of coarse particles in the bed. The elutriation rate constant of group C or group A particles is not only affected by the properties of the elutriated powders or particles and gas velocity, but also by both the weight fraction and size of C powder in the bed. This finding differs from the elutriation result of A or B particles from a fluidized bed. (C) 2004 Elsevier Ltd. All rights reserved.