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Regarding spray dryers
As its name suggests, a spray dryer is device that produces powder by drying liquids.
It can quickly produce dried products by spraying liquids as fine mists and effectively bringing them into contact with hot air to evaporate moisture.
It can turn a variety of liquids into powder, for example, if milk is sprayed, it produces powdered milk, and if coffee is sprayed it produces instant coffee.
Drying is defined as evaporating moisture contained in substances, to convert the substances to a dry state.
Drying improves preservability by preventing moisture adsorption and solidification, and can be expected to improve transportability by reducing weight.
What kinds of things can be dried?
Food:Amino acids, miso, soy sauce, glucose, caramel, coffee, powdered oil, etc.
Pharmaceuticals:Pharmaceuticals, pesticides, inorganic medicines, enzymes, antibiotics, vitamins, etc.
Ceramics:Alumina, zirconia, titanium oxide, tungsten carbide, etc.
Chemical products:Organic catalysts, surfactants, vinyl chloride, pigments, dyes, etc.
What are the advantages and disadvantages of spray dryers?
1. Process simplification Recommended! Moving from shelf drying + crushing to spray dryers
To obtain dried products from liquid stock solutions, the solutions must pass through three processes, drying, pulverizing, and granulating.
Spray dryers can do all three in via one process.
2. Note prone to heat effects Recommended! Moving from vacuum cooling and drying to spray dryers
Since spray dryers dry instantaneously, they cause little heat stress, which allows food to keep its flavor
3. Continuous operation Recommended! Moving from shelf drying and fluidized bed drying to spray dryers
Capable of continuous product production as long as the process provides a continuous supply of stock solution as the product is obtained in the same one process.
4. Enables adjustment of product particle size and bulk density
Product particle size and moisture can be adjusted by adjusting operational conditions.
Heating efficiency is not the best because hot air is discharged after drying, but discharged energy can be recovered by installing a waste heat recovery device.
What kind of powder can they produce?
Although it depends on the characteristics of the liquid to be sprayed, spherical products with good fluidity can be produced.
Inorganic substances, such as ceramics, etc. become products with sharp PSD, uniform particle size and good fluidity, and organic substances, such as food, etc. become porous products with easily soluble hollow particles.
What is the spraying method?
Devices that spray liquids are called “atomizing devices,” and are the most important parts of spray dryers.
Atomizing devices are largely divided into nozzle method and rotary disc method (disc method) devices.
Disc-type devices rotate discs as high speeds, atomize liquids via centrifugal forces, and spray them from the circumferences of the discs.
Pressurized-nozzle type devices atomize by pressurizing liquids, and then spraying the liquids from a nozzle tip in the form of a spray.
How are disc type nozzles different?
Generally speaking, pressurized nozzle type devices are best for producing large quantities of relatively large particles (around 80 μm or more), and disc type devices are best for producing small to medium quantities of relatively small particles.
Furthermore, disc type devices are best for multiple-product production because, with them, particle size can be controlled by changing rotational speeds.
First, as a major premise, spray dryers can only dry liquids (solutions and slurries).
Drying even of liquids can be difficult if they are highly viscous and thus cannot be atomized.
Substances that do not dry, such as oils, can be dried by turning them into micro capsules, and then using a device called a cooling and granulating device.