Spray drying and Spray Congealing, also referred to as the globulation process, entail the atomization of hot melts, solutions, or suspensions to produce spherical particles or pellets. In both processes, the droplet size is maintained at a small scale to enhance the evaporation or congealing rate, resulting in the production of pellets that are typically very small in size.
Spray Drying: The pharmaceutical compounds in either solution or suspension are atomized, with or without the addition of excipients, into a stream of hot air to produce dry, highly spherical particles. Upon contact with the heated air, the evaporation of the solvent begins. This drying process progresses through several stages, during which the viscosity of the droplets steadily rises until nearly all of the solvent is eliminated, resulting in the formation of solid particles. Typically, spray-dried pellets exhibit a porous structure.
Spray Congealing: This method involves suspending particles in a molten coating substance and transferring the resulting slurry into a spray dryer where cold air is circulated. Upon contact with the air, the slurry droplets solidify. Typically, low melting materials like waxes are used as coating agents. The congealing process necessitates a higher ratio of coating agents to active material compared to spray drying, as only the molten coating agent forms the liquid phase.