A microscale investigation of liquid bridges in the spherical agglomeration process

Spherical agglomeration is an industrial process traditionally used to separate or recover fine solids dispersed in a liquid suspension through the addition of a second immiscible liquid (binder) which presents an affinity for the solids and is capable of forming small liquid bridges that hold the particles together. Under appropriate physico-chemical conditions, the desired particles can be selectively agglomerated and removed from the slurry. ecently, the spherical agglomeration technique has been used for the manufacture of high value products, such as crystalline pharmaceutical drugs, and is attracting increasing attention in the bioprocessing area. However, spherical agglomeration has yet to reach widespread commercialisation beyond the minerals industry. This is despite the simplicity of the process, the low cost of installation required and the possibility of agglomerating particles down to a few microns in size and is probably due to the lack in understanding of the controlling mechanisms involved. s paper, a microscale approach to investigate the mechanisms that lead to spherical agglomeration is presented. The geometry and the strength of liquid bridges formed between pairs of particles with diameters in the range 80–130 μm, submerged in a second liquid, are analysed and compared with values predicted by theory.