Spray dryer working principle
Spray drying equipment is particularly suitable for drying materials with high initial moisture. Spray dryers are playing an increasingly widespread role in the food industry.
The working principle of spray drying:
Spray drying is a drying process in which raw materials are dispersed into droplets with an atomizer, and hot air (or other gas) is directly contacted with the droplets to obtain a powdery granular product.
After filtering and heating, the air enters the hot air distributor on the top of the dryer. The hot air enters the drying chamber in a spiral shape and uniformly. The material liquid passes through the high-speed centrifugal atomizer at the top of the tower body and rotates and sprays into extremely fine misty liquid beads. The droplets are in contact with the hot air, mixed and flowed at the same time for heat and mass transfer, and can be dried into a finished product in a very short time. The flow directions of the droplets and the hot air are cocurrent, countercurrent and mixed flow. The contact methods are different. The temperature distribution inside, the movement trajectory of the fog point (or particles), the residence time of the particles in the drying tower and the properties of the product have a great influence.
Most of the finished products are output from the bottom of the drying tower, and part of the fine powder is entrained in the exhaust gas, and the exhaust gas is discharged by the fan through the cyclone separator.
Features of spray drying:
The drying speed is fast, and the surface area of the material liquid is greatly increased after atomization. In the hot air flow, it can evaporate in an instant. Because the drying is completed in hot air, the product basically maintains a spherical shape similar to the droplets, and has good dispersibility. , Fluidity and solubility
Simple and stable operation, convenient adjustment and control, easy to realize automatic operation
The production process is simplified, and it is suitable for continuous control of the production of liquids with a moisture content of 40%-90%. It is dried into powder at one time, reducing crushing and screening and other processes. The operating environment has superior sanitary conditions and can avoid dust during the drying process.
The raw material liquid can be a solution, a slurry, an emulsion, a suspension, a paste or a melt, and even a filter cake can be processed.
The main purpose of spray drying:
Food industry: sugar, cocoa, coffee, spices, milk powder, condiments, etc.
Pharmaceutical industry: Chinese medicine extract, tablet granules, capsule granules, low-sugar or sugar-free Chinese patent medicine granules. Other industries: pesticides, feed, fertilizers, pigments, dyes, etc.
