Granulation of enzyme powders in a fluidized bed spray granulator

In order to improve the handling properties of a fine enzyme powder the increasing of particle size by granulation was studied. Enzyme powders were granulated in a fluid bed granulator. Sodium chloride powder was used as a filler material, but in some cases no filler was used. In the first part of the study the granulation properties of the fine sodium chloride powder were studied. The particle size of the salt granules obtained was increased by three process parameters: increasing the concentration of the binder in the spraying solution, increasing the spraying rate of the binder solution and lowering the temperature of the fluidizing air. When an enzyme powder was granulated it was observed that the largest granules were obtained when the filler material was mixed with the dry powder. The mean particle size in these types of granulated powders ranged from 135 to 200 μm. When the filler was added to the enzyme concentrate prior to drying the increase in particle size during the granulation process was negligible and the mean particle size was only slightly greater than 60 μm. The flowing properties of the enzyme granules were more easily improved than their wettability. The decrease in bulk density as a consequence of granulation was between 20 and 40%.