Something You Should Know About Spray Drying
This article will show you spray drying advantages and disadvantages, and modes of spray drying atomization as well.
Spray drying advantages and disadvantages
1. Due to the large surface area of the droplet group, the drying time required for the material is very short (in seconds).
2. In high-temperature airflow, the temperature of the wet-surface material does not exceed the wet-bulb temperature of the drying medium. Due to rapid drying, the final product temperature is not high. Therefore, spray drying is particularly suitable for heat-sensitive materials.
3. High production efficiency and few operators. Large production capacity and high product quality. The spray volume can reach several hundred tons per hour.
4. The flexibility of spray drying operation can meet the different quality standards of the dryer, such as particle size distribution, product shape, product properties (without dust, fluidity, wettability, instant solubility), product color, fragrance, flavor, biological activity and moisture content.
5. The technological process is simplified. The solution can be directly made into powder products in the drying tower. In addition, spray drying is easy to achieve mechanization and automation, reduce dust flying, and improve the working environment.
Spray drying advantages and disadvantages can give us an explicit idea of the spray drying technology and provides us references when we want to dry something and are thinking of which drying method should be used. Mentioned paragraphy is the advantage part of spray drying advantages and disadvantages, and the following is the disadvantage part.
Disadvantages of spray dryer:
1. When the air temperature is lower than 150C, the volumetric heat transfer coefficient is low [23~116W/(m3.K)], and the volume of the equipment used is large.
2. There is a high requirement for the separation of a gas-solid mixture, and generally, two levels of dust removal are required.
3. The thermal efficiency is not high, for the general downstream tower type, the efficiency is 30%~50%, and the countercurrent tower type is 50%~75%.
4. The equipment is relatively complex, covering a large area, and a large investment at a time.
5. The price of the atomizer and powder recovery device is relatively high.
6. A large amount of air is required to increase the power consumption of the blower and the capacity of the recovery device.
Modes of spray drying atomization
There are three conventional modes of spray drying atomization
1. Modes of spray drying atomization — rotary atomization
The characteristics of rotary atomization: large single-machine production capacity (maximum spray volume up to 200t/h), easy-to-control feed amount, large operation flexibility, and wide application.
2. Modes of spray drying atomization—pressure atomization
This type of atomization is characterized by being able to produce coarse particles and easy maintenance. Because the nozzle hole is small and easily clogged, the feed liquid must be strictly filtered. Nozzle holes are easy to wear and must be made of wear-resistant materials. Pressure nozzles also have a new structure called pressure-airstream nozzles. Its characteristic is that the center is a pressure type nozzle, and the surrounding environmental gap is an airstream-type nozzle. The atomization is divided into two stages: the pressure nozzle first forms a liquid film, and this liquid film is atomized by the airstream for the second time to make the droplets finer.
3. Modes of spray drying atomization—airstream atomization
Spray dryers with airstream atomization, Hawach’s airstream small spray dryer, for example, are mainly used in the laboratory and intermediate factory manufacturers. The material liquid that can not be atomized by the first two can be atomized by this type of spray dryer. High-viscosity pastes and filter cake materials can be atomized using a three-fluid nozzle. The disadvantage is the large power consumption.