The resulting granules are then mixed with finely ground drug substances and, if necessary, with auxiliary substances not introduced in the suspension; atomization of solutions or suspensions consisting of drug and auxiliary substances. If it is necessary to obtain granules from liquid starting substances (spray granulation), the particles in the fluidized bed do not undergo agglomeration, but are covered with layers again and again until a grain of the desired size (the structure of the “bulb”). Spray granulation in a fluidized bed is the drying of liquids (solutions, suspensions, melts) while simultaneously forming granules. Crystallization centers for granules can be created in advance (introduced nuclei) or formed in the fluidized bed during abrasion and fracture (crystallization centers that are inoculums from the material being crystallized).

The sprayed liquid covers the crystallization centers with subsequent drying. Compared to agglomerates, spray granules are denser and stronger. Modern equipment for the granulation and spray drying process has been developed by Glatt. In such a plant, the feed material in liquid form is subjected to drying while simultaneously forming granules. The AGT 2700 Glatt has a circular vortex bottom. The entire fluidized bed is continuously stirred. The gas feed rate in the machine is high, which enables the pelletization of adhesive materials as well. The resulting dust is precipitated on external filters and returned to the process. The product is discharged in the middle of the process compartment through a discharge pipe. All areas of the working chamber are equidistant from the outlet and the lumps formed are removed in a timely manner.