The spray dryer is a drying device for directly drying a solution or a suspension into solid particles, which can save unit operations such as evaporation, crystallization, separation, and pulverization, and can be continuously and automatically produced, and the operation is stable. With this drying method, the gas-solid two-phase contact surface area in the spray dryer is large, and the drying time is short, generally 5 to 30 s, which is suitable for drying the heat sensitive material. The product obtained by drying has good performance, and particles of 30 to 50 mm can be obtained, and the product has good fluidity and fast solubility. The disadvantage is that the dryer has a large volume and a low heat transfer coefficient, resulting in low thermal efficiency and high power consumption.
There are many classification methods for spray dryers. According to the flow direction of gas and liquid, it can be divided into parallel flow, counter flow and mixed flow; according to the installation method of atomizer, it can be divided into upper spray type and lower spray type; The structure can be divided into centrifugal type, pressure type, and air flow type; according to whether the heating gas is circulated, it can be divided into open type, partial circulation type and closed type.
First, the spray dryer stick wall generally has the following three conditions:
1. The semi-wet material sticks to the wall: the reason is that the sprayed droplets have already contacted the wall before they reach the surface drying, so they stick to the wall, and the position of the sticky wall is generally the droplets sprayed against the atomizer. On the plane of the motion trajectory, and the structure of the atomizer, the hot air is related to the motion state in the tower;
2. Hot-melt sticky wall of low-melting material: The reason is that the material reaches the melting point at a certain temperature and begins to melt and become sticky and adhere to the wall;
3, the surface adhesion of dry powder: dry powder in the limited space will always have some touch on the wall, this is unavoidable, but such a sticky wall is generally not thick, as long as the air is blown or gently tapped Can be shaken, the simple solution is to polish the inner wall, which can solve this problem to some extent.
Second, the following list of five ways to prevent sticking:
1. Use a wall-mounted drying tower with air cooling to keep the wall temperature below 50 °C;
2. Introducing a secondary air cooling tower wall through the tangential direction of the tower wall cyclone;
3. Install an air broom consisting of a row of nozzles near the wall of the tower and slowly rotate it along the tower wall;
4, the tower wall increases the air hammer, through the impact of the air hammer, forcibly make the sticky wall material detach;
5. Increase the processing precision of the spray dryer, and the inner wall polishing of the tower can also reduce the sticking wall.
The above knowledge about the spray dryer and precautions for use are organized and shared by the fruit dryer machine manufacturer. I hope I can help you with the spray dryer problem. If you intersted in learning more information about Fruit Drying Machine , please visit: https://www.gf-machine.com/solution/freeze-drying-solution/