Spray drying equipment technology has been widely used in pharmaceuticals. In the field of solid preparations, this technology is often used in the drying process of highly heat-sensitive drugs, liquid material concentration, and easily decomposed drugs. During use, different materials will have different requirements on spray drying equipment. How to make the spray process achieve these requirements? What details should we pay attention to during this period?

Cleanliness requirements: Some raw material drug production processes need to be carried out in a 100,000-level clean environment. Spray drying equipment is an important process for raw material quality control. In order to ensure the quality of medicines, the parts of the spray dryer that contact the materials need to be made of stainless steel. For materials with strong acid corrosiveness, stainless steel can be used. The drying chamber, cyclone separator, filter and other parts that are in direct contact with the material should have smooth inner walls, no dead corners, and be easy to disassemble and clean. Because the spray drying equipment is too large, it cannot be placed in a clean area as a whole. Air flow dryers often only place the part where materials are collected in the clean area. In this case, the system requires good sealing performance to prevent external contamination of the system.

Wall-sticking phenomenon: During the spray drying process of solid preparations (especially traditional Chinese medicines), wall-sticking phenomenon is an important problem that prevents the normal operation of the spray dryer. Material sticking to the wall is not only detrimental to collection operations, but as time goes by, sensitive wall-sticking materials will degenerate and become unqualified materials. From a process perspective, solutions include: selecting appropriate solvents, adding excipients, and changing process parameters. However, these methods have little adjustment effect, so a basic solution is sought from an equipment perspective.

In recent years, domestic and foreign experts have conducted a series of studies on wall sticking and caking problems that occur during the drying process of spray drying equipment. They believe that the cause of wall sticking is wall temperature, and have summarized 5 measures to avoid wall sticking:
* Adopt a sandwich-wall drying tower and use air cooling to keep the wall temperature below 50°C;
* The secondary air is introduced tangentially through the cyclone blades on the tower wall to cool the tower wall;
* Install an air broom consisting of a row of nozzles near the wall of the tower and make it roll slowly along the tower wall;
* An air hammer is added to the tower wall, and the material stuck to the wall is forced to break away after being struck by the air hammer;
* To increase the precision of processing, polishing the inner wall of the tower can also reduce wall sticking.