FAQ & Glossary

Spray drying is a continuous, single-step process — droplet formation, drying, and particle collection happen within seconds — which shortens processing time compared with batch methods such as Freeze Drying, and supports high throughput. The process also scales predictably, since the same atomization and drying principles apply from bench-scale units (evaporation rates in the order of a few kg/h) up to pilot and production-scale equipment (tens of kg/h).

Spray drying accepts a wide range of feed materials — solutions, suspensions, and emulsions — and produces microparticles with uniform size distribution and structural characteristics (morphology, density, porosity) that can be tuned to the target application. Compared with other microencapsulation techniques, it typically has a lower cost per kilogram of product and integrates easily with upstream or downstream unit operations. Running the process inside an isolator further limits the risk of cross-contamination and operator exposure.

The liquid feed must be homogeneous and physically and chemically stable throughout the entire process. Viscosity needs to ensure efficient droplet formation and the target particle size, and every formulation component must withstand the process conditions (temperature, shear). Solids content also has to be set so the process meets the required specifications in terms of yield and residual moisture.

Typical microparticle size ranges from 5 to 100 µm. The particle dimensions depend on the formulation, the atomizer/equipment configuration, and the process conditions used.

Yes, but this requires careful design and process parameters set up. Excipient selection should protect the active from thermal stress during drying — for example, adding stabilizers such as sucrose or trehalose, leucine for protein-based actives. The choice of atomizer also matters: published studies reported in the literature show that an ultrasonic nozzle can raise the droplet temperature during atomization, causing an additional thermal stress that a two-fluid nozzle does not introduce, and that can measurably reduce the activity of heat-sensitive active molecules. Process parameters — inlet/outlet temperature, gas flow rate, feed rate, and the active's residence time in the drying chamber — must then be set to keep the particle's thermal conditions within the compound's degradation limits.

Yes. Running the spray dryer inside a dedicated isolator keeps the process in a closed environment, containing powder dispersion and protecting both the operator and the surrounding environment from exposure to the active ingredient. Schedio's high-containment configurations combine HEPA-filtered ventilation with isolator designs engineered around the specific Occupational Exposure Limits (OELs) required for the compound being processed.

Two-fluid nozzles, rotary atomizers, pressure nozzles, and ultrasonic nozzles are the available atomizers. Two-fluid nozzles use compressed gas to break the feed into droplets, while rotary atomizers use a high-speed spinning wheel; both are useful across lab, pilot, and production-scale equipment. For applications that require a narrow, uniform particle size distribution, pressure nozzles and rotary atomizers are generally preferred.

Scaling up is not simply a matter of increasing batch size: formulation and process parameters need to be re-evaluated together at each scale. Elements that change between lab and pilot/production equipment include the maximum evaporative capacity, the maximum inlet temperature, the atomizer/nozzle configuration, and the construction material (typically glass at lab scale, insulated stainless steel at pilot/production scale), which changes heat transfer behavior. As a general rule, powder recovery yield tends to improve moving from lab to pilot scale — increases of 10-30% are commonly observed — while particle size typically increases, since pilot-scale equipment favors larger droplet formation. Because process behavior does not scale linearly, inlet/outlet temperature, feed rate, and atomizer settings all need re-verification rather than direct transfer from lab conditions.

Yes. Spray dryers can work in a closed-loop, nitrogen-purged configuration, to create an inert atmosphere, which is required both for oxygen-sensitive actives and for safely processing flammable organic solvents. In validated trials, nitrogen purging reduced the internal oxygen concentration from ambient levels (21%) to below 1% within approximately 40 minutes, and oxygen was then maintained below 2% throughout processing without affecting drying performance or final particle quality.

Freeze-drying is currently the industry standard for stabilizing biopharmaceuticals as solid products, but it has recognized limitations: long cycle times (often 24-48 hours or more), high energy and vacuum-related operating costs, and limited control over particle size and morphology. Spray drying is increasingly explored as an alternative, since it is a continuous, single-step process, and the rapid drying combined with a self-cooling effect from solvent evaporation reduces the risk of thermal degradation — making it applicable even to heat-sensitive biologics when formulation and process parameters are properly optimized. Even if freeze-drying remains today the main choice for many biologics, in the near future spray drying could be a viable alternative.