How To Prevent The Wall Sticking Phenomenon Of The Spray Dryer?

The spray dryer uses the method of spraying to spray the material into mist and loosen it in the hot air. The material and the hot air contact each other in the form of parallel flow, countercurrent or mixed flow, so that the water evaporates quickly to achieve the purpose of drying. Using the method of spray drying can save unit operations such as concentration, filtration, and destruction, and the drying time is short, and the product has good fluidity and instant solubility, so it is widely used in industries such as medicine.

It is very important to operate the spray dryer correctly and understand the performance of all aspects of the equipment and possible problems. It is also the key to ensure the life of the equipment and the stability of the enterprise's operation. Among them, the wall sticking phenomenon is a prominent problem that prevents the normal operation of the spray dryer, especially in the spray drying process of solid preparations (especially traditional Chinese medicine). Material sticking to the wall is not only unfavorable to the collection operation, but also as time goes by, the sensitive sticking material will deteriorate and become unqualified material. In order to get rid of the phenomenon of wall sticking, many operators try to start from the process point of view. The solutions include selecting appropriate solvents, adding auxiliary materials, changing process parameters, etc., but there is not much room for adjustment in these methods, so it is necessary to start from the equipment. Viewpoint seeks the underlying solution. The wall sticking phenomenon of the spray dryer generally has the following three situations:

1. The semi-wet material sticks to the wall. The reason is that the sprayed droplets have been in contact with the wall before reaching the surface to dry, so they stick to the wall. The direction of sticking to the wall is generally on the plane of the trajectory of the sprayed droplets from the atomizer, and the fog The structure of the vaporizer is related to the movement state of the hot air in the tower;

2. Hot-melt adhesive wall for low melting point materials. The reason is that the material reaches the melting point at a certain temperature and begins to melt and become sticky, adhering to the wall of the vessel;

3. Surface adhesion of dry powder. When the dry powder moves in a limited space, there will always be some bumps on the wall of the container. This is unavoidable, but such sticky walls are generally not thick, and can be shaken off by blowing air or gently hitting it. The solution is to polish the inner wall, which can solve this problem to a certain extent.

After finding out the cause of the wall sticking phenomenon, five ways to avoid the wall sticking are listed:

1. Choose a double-wall drying tower, and cool it with air to keep the wall temperature below 50°C

2. The secondary air is tangentially introduced through the tower wall cyclone to cool the tower wall;

3. An air broom composed of a row of nozzles is installed near the wall of the tower, and it is rolled slowly along the tower wall;

4. An air hammer is added to the wall of the tower, and the material sticking to the wall is forcibly separated by the knocking of the air hammer;

5. Adding the processing accuracy of the equipment, the polishing of the inner wall of the tower can also reduce the sticking of the wall.