The working process of the flash dryer is divided into four stages: crushing, gas-solid contact, drying, and classification, which are:
1. When the material enters the dryer, it is broken by the stirring blade and the high-speed airflow, so as to maximize the dispersion of the material and the surface area of the wet material per unit volume.
2. After the material is crushed, it is blown up by the hot air flow generated by the high-speed rotation, forming a fluidized layer. In the drying process of mass transfer and heat transfer between the material and the hot air, most of the water evaporates at this stage. After the material is further broken and the water evaporates, the buoyancy is greater than the gravity, and the material starts to move upwards and is discharged out of the dryer after passing through the classification.
3. The stirring paddle of the flash dryer breaks the material and produces a dispersion effect. At the same time, the air entering the dryer is also in a debugging turbulent state, and the gas-solid mixture is quickly reached. The block material falls downward under the action of gravity. Because the bottom of the dryer has an inverted cone structure, the airflow speed is very large, which can ensure that the block material is in a good fluidized state and is surrounded by hot air.
4. The classifier is a ring-shaped baffle mounted on the top of the dryer. Under the action of centrifugal force, when the material rises with the airflow, the radius of rotation of bulky and undried materials increases. When the radius of rotation is greater than the radius of the grading ring, it is blocked. In the drying chamber, the dryer cannot be discharged through the classifier until the requirements are met. However, the large particles in the outer layer are continuously crushed and dried, and after the centrifugal force becomes smaller, they also move toward the inner ring, and are carried out by the gas when the moisture meets the requirements.
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