Spray drying is a process that is widely used in the liquid process forming and drying industries. Zui is suitable for the production of powdered, granulated or bulk solid products from solutions, emulsions, suspoemulsions and pumpable paste liquid materials. Therefore, spray drying is an ideal process when the particle size distribution, residual moisture content, bulk density and particle loading of the finished product must meet precise standards. By adopting the 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.
The sticking phenomenon is a prominent problem that hinders the normal operation of the spray dryer, and the spray drying process of the solid preparation (especially the traditional Chinese medicine) is particularly obvious. The sticky wall of the material is not only unfavorable for the collection operation, but as time goes on, the sensitive sticky wall material will deteriorate into a non-conforming material. From a process point of view, the solution includes selecting the right solvent, adding the excipients, and changing the process parameters. However, there is not much room for adjustment of these methods, so a fundamental solution must be sought from the perspective of the equipment. Experts at home and abroad have studied the problem of sticking and agglomeration during the drying process. It is believed that the main cause of sticking is the wall temperature.
Spray dryer sticking walls generally have 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, the hot-melt sticky wall of the low-melting material: 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;
3, the surface adhesion of dry powder: dry powder in the limited space will always have some touch on the wall, this can not be avoided, but such sticky wall is generally not thick, as long as the air is blown or gently tapped Can be shaken, zui simple solution is the inner wall polishing, can solve this problem to a certain extent.
Here are 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 hammering of the air hammer, forcibly make the sticky wall material detach;
5. Increase the processing precision of the equipment, and the inner wall polishing of the tower can also reduce the sticking wall.
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.
The sticking phenomenon is a prominent problem that hinders the normal operation of the spray dryer, and the spray drying process of the solid preparation (especially the traditional Chinese medicine) is particularly obvious. The sticky wall of the material is not only unfavorable for the collection operation, but as time goes on, the sensitive sticky wall material will deteriorate into a non-conforming material. From a process point of view, the solution includes selecting the right solvent, adding the excipients, and changing the process parameters. However, there is not much room for adjustment of these methods, so a fundamental solution must be sought from the perspective of the equipment. Experts at home and abroad have studied the problem of sticking and agglomeration during the drying process. It is believed that the main cause of sticking is the wall temperature.
Spray dryer sticking walls generally have 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, the hot-melt sticky wall of the low-melting material: 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;
3, the surface adhesion of dry powder: dry powder in the limited space will always have some touch on the wall, this can not be avoided, but such sticky wall is generally not thick, as long as the air is blown or gently tapped Can be shaken, zui simple solution is the inner wall polishing, can solve this problem to a certain extent.
Here are 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 hammering of the air hammer, forcibly make the sticky wall material detach;
5. Increase the processing precision of the equipment, and the inner wall polishing of the tower can also reduce the sticking wall.
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