Basics of Spray Drying
There are a lot of basics of spray drying we shall know. Let me show you the basis to help you better understand this drying tech.
Basics of spray drying — concentration
The raw material is usually concentrated before being introduced into the spray dryer machine. In the concentration stage, the solid content is increased to reduce the energy consumption required in the evaporation process. Theoretically, it is not recommended to limit the solid content, but under normal circumstances, the material begins to exhibit a higher viscosity at a certain concentration, and the fluidity is not good as well, which poses unlimited challenges to the pump and spray drying process. Therefore, after the general concentration reaches a certain limit, the spray drying process is no longer applicable.
Basics of spray drying — Atomization
The spray dryer is characterized by the atomization of raw materials and the contact of the sprayed mist with hot air. The atomization stage aims to create the best conditions for evaporation and produce a dry product with the required characteristics. The range of dryers ranges from one nozzle to more than fifty.
Basics of spray drying — Contact between the water drop and air
Contact between the water drop and the air is one of the basics of spray drying. The element of the spray dryer is the spray drying chamber. In the chamber, the atomized liquid contact with hot gas, and more than 95% of the moisture inside is evaporated in a few seconds (or even milliseconds). The way the spray contacts the air in the dryer affects the behavior of the droplets during the drying phase and directly affects the properties of the dried product. The contact type between spray and air is based on the position of the atomizer relative to the air inlet. The atomizer nozzle tip is usually located on the top of the dryer and sprays downward. Therefore, the design of the spray dryer involves two core parameters related to the contact between the water drop and air: 1. The rationality of hot air distribution; 2. The atomized droplet diameter and size.
Basics of spray drying — Air filtration
Perhaps for many users who first use this drying system, there is no concept of air filtration, because most laboratorial or standard products are not designed with air filtration. However, in the actual application of spray dryers, the design of air filtration is inseparable. Air filtration generally refers to air filtration of heated air (heating medium), air filtration of atomizers. No matter what kind of gas is used, in actual production and application, especially for food, pharmaceutical, and fine materials, filtration is the configuration that must be carried out.
As one of the basics of spray drying, the working process is as follows: the gas is inhaled into the system through the filter. The efficiency of the filter depends on the product being dried. Generally, chemicals require less filtration, and some food and pharmaceutical processing requires very efficient filters.
Filters usually have two functions, the first is used to avoid contamination of the product being dried, and the second is used to prevent particles from passing through the hot air system and becoming possible sparks when they enter the chamber, which may be a fire and possible ignition source of the explosion.
Because of the particularity of the powder dryer machine, the selection and testing of the filter is a very important task, and the filter should be workable at room temperature and high temperature.