Severe sticking to the walls occurs during the spray drying process
Thread Content
May I ask, which expert can tell me what factors might affect the sticking of materials with high sugar content during spray drying, and what are some solutions to this problem? At present, the relevant factors that I have found online are as follows: the amount of feed is too large, preventing sufficient evaporation ； The drying chamber was not heated sufficiently before the spraying began ； When starting spraying, the material feed flow rate was adjusted too high ； The added liquid solution is unstable. To address the various causes of the aforementioned problems, the following measures can be taken in sequence: appropriately reduce the feed amount ； Appropriately increase the inlet and outlet temperatures of the hot air ； At the start of spraying, the flow rate should be low, and it should be increased gradually until an appropriate level is reached ； Check whether the pipeline is blocked, adjust the solid content of the material to ensure the fluidity of the slurry.
First, I need to know what kind of material it is, what sugars it contains, and what the proportions of each component are. Only by identifying the main factors affecting drying can the problem be solved； Different sugar drying conditions result in varying component ratios, and thus different operating conditions as well. There are many different operating conditions for functional oligosaccharides, for example.
I don’t know what the structure of your spraying device is. Is the rotor of the rotary spray unit controlled in terms of speed using variable frequency? It is possible to confirm whether the actual rotational speed matches the speed displayed by the DCS.
If sticking to the wall still occurs even after adjusting the process parameters, consider adding a vibration device
Sugar-containing materials differ from other materials mainly because sugar is in a semi-melted state at high temperatures. There are 2 effective solutions. 1. Change material properties 2. Change the speed and structure of the atomizer
During the spray drying of solid formulations (especially traditional Chinese medicines), wall sticking is a prominent problem that hinders the proper operation of the spray dryer. Materials sticking to the walls not only hinders collection operations, but over time, such sticky materials can deteriorate and become substandard. From a process perspective, solutions include selecting appropriate solvents, adding auxiliary materials, and changing process parameters; however, the margin for adjustment with these methods is limited, so fundamental solutions must be sought from an equipment standpoint. In recent years, experts at home and abroad have studied the problems of sticking to the walls and caking during the drying process. They believe that the main cause of sticking to the walls is the wall temperature, and thus five measures to prevent this phenomenon have been identified: using a dryer with wall cooling, whereby air is used to keep the wall temperature below 50°C ； Secondary air is introduced tangentially through the swirl vanes on the tower wall to cool the tower wall ； An air broom composed of a row of nozzles is installed near the wall of the tower, and it is made to rotate slowly along the tower wall ； Air hammers are added to the tower walls; through the impact of these hammers, the material stuck to the walls is forced to come loose ； Increasing the precision of processing, as well as polishing the inner wall of the tower, can also reduce sticking to the walls.
Simply changing the slurry factor is not a viable approach, especially when drying organic substances. I firmly support LS’s idea of starting by examining the objective factors one by one.
If you have tried all the methods mentioned above and still cannot solve the problem, I suggest you consider the source of the incoming air; you can carry out dehumidification of that air, a practice commonly used in spray drying.
This post was last edited by nglcx2003cn on 2011-7-11 at 12:42. For the spray drying of sugar-containing materials, the material is in a thermoplastic state inside the tank; in fact, the tower should primarily serve to cool and granulate the material. Therefore, if the temperature is too high, the material will melt again at the bottom of the tower, leading to caking. Another possible solution to the problem of sticking to the wall is to apply more powder. The principle is to first break the material that is sprayed down into small particles, and then introduce these particles into the spray tower. Under the action of wind, the material forms a layer on the walls of the tower; as a result, the newly sprayed material does not stick directly to the walls. The layer on the walls has a loose structure, which makes it easy to remove it using a pneumatic hammer. Therefore, powder needs to be replenished continuously during the spraying process. Previously, with our vitamin spray drying process, the layer formed on the walls was 20 cm thick, resulting in very little finished product. The problem was solved after installing the powder return system. I believe your question is exactly the same as our previous one. If it’s solved, remember to give more points; it’s even better if it’s attractive :)