Spray drying requires that the material and liquid be d […]
Spray drying requires that the material and liquid be dispersed into very fine droplets, so that the material liquid can form a large specific surface area, so that the mist droplets and the hot air produce a dramatic heat and mass exchange, quickly eliminating material moisture in seconds to tens of seconds. And get dry. Spray drying is the use of different sprayers to spray the suspension or viscous liquid into a mist, and the heat and mass transfer between the hot air and the drying process occur. The finished product sinks to the bottom of the drying chamber as a powder and is discharged continuously or intermittently from the unloader.
Drying temperature is low. Although higher temperature hot air is used, the surface temperature does not exceed the wet-bulb temperature of the heated air due to the large amount of moisture contained in the droplets, which is generally 5o to 60oC, and the residence time of the material in the desiccator is short. The final temperature will not be too high and it is very suitable for the drying of heat sensitive materials.
The product has good dispersibility and solubility, and the finished product has high purity. However, the volume drying intensity of spray drying is small, the volume of the drying room is large, and the heat consumption is large. Generally, evaporating 1 kg of water requires about 6000 kJ of heat, which is equivalent to the consumption of 2.5 to 3.5 kg of steam.
The key to spray drying is the atomization of feed liquid, which is related to the technical and economic indicators of spray drying and product quality. The ideal sprayer requires uniform spray particles, simple structure, large output, and low energy consumption.
There are three kinds of atomizers: pressure sprayer, air sprayer, and centrifugal sprayer. The pressure spray drying tower, air spray drying tower and centrifugal spray drying tower spray drying equipment are formed. In the bio-industry, two types of spray drying equipment are used more frequently.