What are the common types of spray dryers?

Spray dryer is a kind of equipment that completes drying and granulation at the same time. It is mainly composed of slurry supply system, atomizer, drying tower, hot air system, exhaust gas discharge and dust removal system, discharge and powder conveying system, etc.

How spray drying works
Spray drying is a process in which the material liquid is dispersed into fine droplets by an atomizer, and the solvent is quickly evaporated in a hot drying medium to form a dry powder. The general spray drying is divided into four stages: a. The material liquid is atomized; b. The atomization group is contacted and mixed with the hot drying medium; c.
The raw material liquid can be a solution, an emulsion or a suspension, or it can be a liquid form that is transported by a pump such as a melt or a paste.

Common spray dryers
The dilute liquid is sprayed into mist droplets and dispersed in the hot air flow, so that the moisture can be quickly evaporated to obtain a solid product. The drying time is generally only a few seconds to tens of seconds. The sprayer is a key part of spray drying, mainly centrifugal, pressure and airflow sprayers.

1. Pressure spray dryer
The liquid material (filtered liquid material) is sent to the pressure atomizer to be atomized into small liquid droplets through high pressure, and the atomized liquid droplets (with a large surface area) are fully contacted with hot air, and the drying is quickly completed within 10-30 seconds. Process to separate and obtain finished products of powder particles.

2. Centrifugal spray dryer
The air passes through the filter and heater, and enters the air distributor at the top of the centrifugal spray dryer, and the hot air enters the dryer evenly in a spiral shape. The material liquid is pumped from the material liquid tank through the filter to the centrifugal atomizer at the top of the dryer, so that the material liquid is sprayed into extremely small mist droplets. The finished product is dried in a short time, the finished product is discharged from the bottom of the drying tower and the cyclone separator, and the waste gas is discharged from the blower.

3. Airflow spray dryer
Mainly, the air or water vapor is sprayed out of the nozzle at high speed, and the material and liquid are separated into fine droplets by friction, so that the droplets are in complete contact with the hot air to form heat exchange, and the whole process takes less than half a minute. It has a good effect on viscous materials, which is unmatched by other spray dryers, and is easy to operate.

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