Spin flash dryer and cabinet dryers are inherently more expensive to operate, require a larger footprint, more manpower, lower drying speeds, and much lower thermal efficiency. In comparison, the FLASH dryer, in its simplest mechanical form, is merely a hot air conveyor that can lower fairly liquid solids. The material is then spread out, exposing the maximum surface area to the drying process. This results in a very fast drying rate, with the time required expressed in seconds rather than minutes or hours. Because of the short residence time and rapid evaporation of moisture, the wet bulb temperature (WBT) is maintained until the surface moisture is gone, even when used at high temperatures. Therefore, high inlet temperatures of up to 700°C can be used without compromising quality, which could be degraded if the material is heat sensitive.
Why drying, decomposition, and spraying?
During the drying process, moisture inside the particles reaches the surface by capillary action and is removed from there. In other words, it is obvious that the smaller the particles are, the faster they dry. Therefore, if “quick drying” is also performed during the milling and fine grinding processes, the system as a whole will be very efficient.
In the normal milling and fine grinding process, if the moisture content of the raw material is high, chalking will occur in the milling process, resulting in a very low yield of raw material. If “rapid drying” is performed simultaneously with milling, the process is well improved. Moisture absorption of starting materials may be due to hygroscopic substances during transportation and storage, or may be inherent in the extraction stage.
Types of spin flash dryer:
Spin flash dryer systems are designed for specific applications and fall into one of the following categories
- Fast drying without disintegration or spraying.
- Fast drying with disintegration
- Fast drying with disintegration
Fast drying without disintegration or spraying.
If the material to be dried is sufficiently liquid, only instant drying without disintegration or spraying is possible. Figure 1 shows a system consisting of an automatic feeder, a ventally operated gas transport system into which the material is fed, and a cyclone separator installed to separate the dried product. It also requires the appropriate type of heating.
Rapid Drying with Collapse:
The system consists of a heater, conditioner, and disintegrator with cyclone separator. Disintegration is done with a “griffinmachinery” separator/hammer mill. Depending on the specific requirements, it may or may not include a conditioner and a dust collector. The product obtained with this equipment is not in a fine powder state.
It has excellent quick-drying and atomizing properties.
A high-speed impact sprayer with a cyclone dust collector feeding hot air is used. This system is cost-effective and can be easily and economically implemented when the end product requires pulverization. It replaces pre-drying systems in tunnel, rotary, and plate dryers. As with disassembled flash dryers, conditioners and/or dust collectors may or may not be included in the spray drying system.
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