Flash evaporation dryer (also known as rotary flash evaporation dryer or instant dryer) is an efficient and continuous drying equipment widely used in chemical, pharmaceutical, food, mineral and other industries, especially suitable for processing paste like, filter cake like and high humidity mud like materials.
The entire work process is an integrated dynamic system of "fragmentation dispersion drying grading".
1. Feeding and preliminary crushing
Wet materials (usually in the form of paste or filter cake) are continuously and quantitatively fed into the bottom of the drying chamber through a spiral feeder.
At the bottom of the drying chamber, there is a high-speed rotating crushing and stirring blade (also known as a crusher) installed. As soon as the material falls, it is immediately violently crushed and sheared by this mixing blade to prevent the accumulation of large pieces of material.
2. Hot air contact and enhanced heat transfer
The high-temperature hot air generated by the hot blast stove (gas, oil, coal, or steam/electric heating) enters at high speed from the circular air duct at the bottom of the drying chamber in a tangential direction.
This tangential air intake design creates a strong rotating upward airflow of hot air in the drying room.
The broken small wet material particles are instantly mixed and in contact with the high-speed rotating high-temperature hot air. Due to the small particle size, large specific surface area, and high relative velocity with hot air, the heat and mass transfer process is rapidly enhanced.
3. Instant drying ("flash evaporation")
The surface moisture (free water) in the material evaporates in a very short period of time (usually 0.5-5 seconds).
During the drying process, the material particles rotate and rise with the airflow. The continuously dried particles accelerate their rise due to the decrease in density, and are further broken by the bottom crusher or collisions between particles, exposing new wet surfaces and enabling continuous and efficient drying.
4. Grading and Collection of Finished Products
At the top of the drying chamber, there is a classifier (also known as a "grading ring" or "elution ring").
Grading function: Dry and qualified fine particles (meeting moisture requirements), due to their small particle size and light weight, can overcome the centrifugal force generated by the classifier, pass through with the airflow, and enter the subsequent cyclone separator and bag filter for collection.
Coarse particles/partially dried particles: Those particles or clumps that have not been completely dried and have a larger mass will be subjected to stronger centrifugal force from the classifier, thrown towards the wall of the drying chamber, and fall back to the bottom of the drying chamber due to gravity, re participating in the crushing and drying process.
This "grading return" mechanism is a key design of the flash dryer, ensuring uniform moisture content and controllable particle size of the final product, and avoiding unqualified products from entering the finished product.
5. Gas solid separation and tail gas treatment
The airflow carrying dry products first enters the cyclone separator, where most (about 95% or more) of the dried products are separated and collected.
The exhaust gas containing extremely fine dust enters the bag filter (or wet filter) for deep purification to ensure that the dust emissions meet the standards.
The clean exhaust gas is discharged into the atmosphere by the induced draft fan.