Analysis of Fluidize Bed Granulation Process Using Steam-Water Two-Phase Binder

Fluidized bed granulation is a common operation to improve the dispersibility and solubility of powdered food including instant soup, as well as powdered instant beverages. In the fluidized bed granulation process of food powder, fine partic les are formed to large granule usually by spraying aqueous solution of polysaccharide as binder. The water added to the powder materials plays an essential role for the growth of granule, however, excessive moisture spoils the quality of granule products and elongate the processing time and successive drying period of the granule. This article summarizes a development process of new fluidized bed granulation technique using steam-water two-phase (SWTP) binder. This article firstly introduces a model to describe moisture content of fluidized bed as a function of time and binder spraying rate for the conventional granulation process using liquid binder. The model was consequently extended for the process using SWTP binder by considering condensation of steam to the powder materials and evaporation of binder droplets. The model developed in these studies was used to determine the binder spraying conditions for each binder to compare the granule growth at equivalent profile of moisture content. It was found that the SWTP binder decreased the amount of water used in the process to 40 ～ 84% comparing with conventional liquid binder.