Views: 81 Author: Site Editor Publish Time: 2022-07-07 Origin: Site
Spray drying is a method of obtaining a dry powder from a liquid by quick-drying with hot gasoline. This is a preferred drying strategy for many heat-sensitive materials such as food and medicine. Air may be a hot drying medium; however, if the liquid can be a flammable solvent that is sensitive to oxygen, nitrogen will be used.
All spray dryers use some type of nebulizer or spray nozzle to break up a liquid or slurry into droplets of a controlled size. The most common are high-pressure rotating discs and single fluid vortex nozzles.
Alternatively, bilinear nozzles or ultrasonic nozzles are used for some applications. Depending on the procedure requirements, discharge volumes from 10 to 500 m can be achieved with all relevant settings.
The most common applications are blocks with a diameter of 100 to 200 meters. Due to the large particle sizes, these powders are free-flowing. The fine particles obtained in the first drying stage can be recycled in a continuous flow, perhaps best in the chamber or at the bottom of the combined fluid bed.
Spray drying systems come in many shapes and sizes, and they may look very different, but they all work the same way. Spray drying is an evaporation process and the most common method of powder production, especially for heat-sensitive materials. The spray dryer mainly consists of a large chamber through which very hot air passes, a feed pump, and a sprayer. The resulting solid powder is usually collected in a helical drum.
The feed solution is fed into the spray dryer through a spray nozzle, which divides the feed solution into individual balls. A nozzle is usually used to make the droplets as small as possible, which increases the rate of heat transfer and the rate of water evaporation. Droplet sizes can vary from 20 to 180 micrometers depending on the nozzle. Upon initial contact with the hot gas, the visible powder particles solidify, forming a solid outer surface with a molten interior.
When the particle falls along the entire length of the chamber, contact with the hot air pulls the liquid from the rest of the particle. It is generally desirable to retain a small amount of moisture in the powder particles at the end of the process, known in commerce as residual moisture. The time it takes for the particle to fall along the entire chamber is called the residence time.
Powder drying can be completed on an external vibratory fluidized bed. Sparkling dried gasoline can be supplied in a combined stream or counter-stream towards the atomizer. The combined current flow allows the particles to have a shorter residence time within the system and the particle separator works more efficiently. The counter current strategy provides a longer particle residence time within the chamber and is often combined with a fluidized bed program.
Dry powder often flows freely. The most common spray dryers are known as single spray dryers because they make the best use of a single drying air with a drying chamber. As a rule, the air is blown parallel to the flow of the sprayed liquid. The powders obtained with the help of these dryers are of high quality, with a large amount of dust and poor fluidity.
To reduce dust generation and increase the flowability of powders, there has been a completely new generation of spray dryers for more than twenty years called multi-result spray dryers. Instead of drying the liquid in one stage, drying is carried out in two steps: the first in the front and a single or integrated static layer at the bottom of the chamber.
The incorporation of this fluidized-bed, by liquefying the powder in a humid environment, makes it possible to agglomerate large particles and obtain, as a rule, granules with an average particle size of hundreds to 300 microns.
Compared with other types of drying, the spray dryer allows you to dry the product very quickly. They also convert a solution or suspension into a dry powder in one step, which can be beneficial to maximize profits and simplify the process.
Telang is a leading spray dryer manufacturer in China, which has the advanced spray drying technology and expertise you need. Telang offers a mini spray dryer and a big-size spray dryer at the same site that can be used to conduct trials and make a variety of products.
As an expert spray dryer supplier, Telang knows the spray drying process inside and out through years of manufacturing for food manufacturers globally. Contact us today to learn more about the spray drying technology and how can we help you meet your goals.