Spray dryer is a continuous drying equipment that can quickly dry liquid materials (solution, suspension or slurry) into solid powder by contacting with hot air through atomization. Its core principles include atomization, hot air contact, evaporation drying, and powder collection, and are widely used in industries such as food, pharmaceuticals, chemicals, ceramics, etc.
Basic process of spray drying
The spray drying process can be divided into the following key steps:
Feed preparation
Liquid materials (such as milk, juice, medicinal liquids, ceramic slurries, etc.) undergo homogenization, filtration, and other pretreatment processes to ensure fluidity.
Some high viscosity materials need to be diluted or heated to reduce viscosity.
Atomization
The liquid is dispersed into tiny droplets (10-200 μ m) through an atomizer (nozzle or centrifuge disk), greatly increasing the surface area and accelerating evaporation.
Atomization method:
Pressure nozzle atomization (high-pressure liquid is sprayed through small holes, suitable for low viscosity liquids).
Centrifugal atomization (high-speed rotating disc throwing out liquid droplets, suitable for materials with high viscosity or high solid content).
Airflow atomization (compressed air assisted atomization, suitable for laboratory or small-scale production).
Hot air contact and drying
Hot air (usually 150-300 ° C, depending on the material) enters from the top or side of the drying tower and mixes with atomized droplets.
The water on the surface of the droplet evaporates rapidly, forming solid particles.
The drying process only takes a few seconds to tens of seconds, suitable for heat sensitive materials such as proteins and probiotics.
Gas-solid separation
The dried powder enters the cyclone separator or bag filter with the airflow for separation.
The exhaust gas is discharged after dust removal, and some systems can recover waste heat.
Powder collection
Dry powder is collected through the discharge valve and can be directly packaged or further processed (such as granulation, mixing).