Quick Answer
Particle size affects flowability, dissolution rate, bulk density, dustiness, and reactivity of powders. Typical ranges: fine powders (10-50 μm) for pharmaceuticals and instant beverages; medium powders (50-150 μm) for food ingredients and chemicals; coarse powders (150-300 μm) for agglomerated products. Control particle size by adjusting feed concentration, atomizer type/speed, feed rate, and drying temperature.
Particle size distribution is one of the most critical parameters in powder processing. It affects everything from how your product flows and mixes to how quickly it dissolves and performs in its final application.
Why Particle Size Matters
The size of particles in your powder directly impacts several key properties:
- Flowability: Larger particles generally flow more freely
- Dissolution Rate: Smaller particles dissolve faster due to greater surface area
- Bulk Density: Particle size affects how much product fits in a given volume
- Dustiness: Finer particles create more dust, affecting handling and safety
- Reactivity: Surface area impacts chemical and biological activity
Factors Affecting Particle Size in Spray Drying
Several process parameters can be adjusted to achieve your target particle size:
Feed Properties
- Solids concentration – higher concentration produces larger particles
- Viscosity – affects droplet formation during atomization
- Surface tension – influences droplet size and stability
Atomization Parameters
- Atomizer type – rotary disk vs. pressure nozzle produce different distributions
- Atomizer speed or pressure – higher speed/pressure = smaller droplets
- Feed rate – affects droplet size and drying time
Drying Conditions
- Inlet air temperature – affects drying rate and particle morphology
- Air flow rate – influences residence time in chamber
- Chamber design – co-current vs. counter-current affects particle properties
Typical Particle Size Ranges by Application
Different applications require different particle sizes:
- Fine powders (10-50 μm): Pharmaceuticals, instant beverages, inhalable formulations
- Medium powders (50-150 μm): Food ingredients, industrial chemicals, detergents
- Coarse powders (150-300 μm): Agglomerated products, granules, tableting excipients
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