1. Material Characteristics (Top Priority)
- Is the material heat-sensitive (enzymes, proteins, traditional Chinese medicine extracts, fruit and vegetable juices)? Spray drying is preferred, with controlled outlet temperature;
- Viscosity:
✅ Low-viscosity, clear solutions: Pressure nozzles / two-fluid
✅ High-viscosity, slurries, high solids content: Centrifugal atomization (LPG centrifugal), less prone to clogging
- Sugar-containing or sticky materials: Highly prone to sticking to the tower walls; select models with tower wall purging/vibration and large tower diameters; also assess whether low-temperature spray drying is required;
- Solvent type: water or organic solvents (ethanol, acetone). For organic solvents, **closed-loop circulation (CTSD)** systems must be selected—these are explosion-proof and allow for solvent condensation and recovery; open-loop conventional spray drying is not permitted;
- Corrosiveness: 304 stainless steel (general food applications), 316L (traditional Chinese medicine, acidic or alkaline solutions), Hastelloy (highly corrosive).
2. Production Capacity/Throughput (classified as small-scale, pilot, and production)
- Small-scale: 50 ml/h to 5 L/h; airflow-type two-fluid spray dryers; suitable for laboratory use, flexible, and convenient for formulation development;
- Pilot-scale: 5–50 L/h; small-scale centrifugal LPG;
- Industrial-scale production: 50 L/h and above; mainstream LPG centrifugal spray drying;
> Note: The stated evaporation rate refers to water evaporation, not feed rate—do not confuse the two! For example, a water evaporation rate of 100 kg/h does not mean a feed rate of 100 kg/h.
3. Target Powder Requirements
- For coarse particles with high bulk density: pressure nozzles;
- For fine powders with adjustable particle size and good flowability: centrifugal atomization;
- For ultrafine powders: two-fluid air atomization;
- GMP, cleanroom, and dust-free requirements: For pharmaceuticals and health supplements, internal and external polishing, no dead corners, and CIP (Clean-in-Place) are required.
4. Heat Source Conditions
- Steam available: Steam heater—lowest operating costs (preferred option)
- No steam: Electric heating (commonly used for small units; electricity costs are relatively high)
- Large-scale plants: Gas-fired hot air furnace
How to Select Supporting Systems
1. Powder Collection System:
General materials: Cyclone separator + rotary valve;
High recovery rate required for fine powders (no powder loss): Cyclone + bag filter;
Explosion-proof/organic solvents: Closed-loop + condensation + scrubbing.
2. Anti-adhesion: For sticky materials, **air purging and tower wall vibration** must be added;
3. Control:
Pilot-scale: Simple temperature control;
Mass production/pharmaceuticals: PLC touchscreen, automatic interlocks, temperature curve recording, alarms.
