Spherical Agglomeration of Binary Mixture in Liquid Suspension

Abstract

The kinetics of the spherical agglomeration of the binary mixture composed of sand (76, 89 or 106μ) and calcium carbonate (3.8μ) in liquid suspension was investigated. By introducing some fine particles to a coarse particles system the agglomerate was compacted more closely during agglomeration than coarse particles alone. The compacting process of the agglomerate during agglomeration was expressed by the modified Kawakita's equation (2), relating the porosity of the agglomerate to the total agitation energy put into the suspension. The agglomeration rate increased with increasing the concentration of fine particles in the mixture until reaching to a critical value at which the agglomeration rate was maximum. An introduction of over-dose of fine particles into the system reduced the agglomeration rate or brought about the rapid secondary agglomeration which followed the ordinary slower agglomeration after a long induction period. The rate constant of agglomeration was maximum at the composition of the mixture corresponding to the closest binary packing in which fine particles just fill the interstices between coarse particles and to the case where fine particles just cover the surface of coarse particles. From the above results and the agreement of the agglomerate growth data with the coalescence model by Kapur, it was concluded that the ordinal slower agglomeration and the rapid secondary agglomeration may be controlled by preferential coalescence between fine and coarse particles and random coalescence, respectively.