Fluidized bed dryer is suitable for drying and cooling of powdery and granular materials in chemical, pharmaceutical, food, dehydrated vegetables, grain, minerals and other industries. Such as: citric acid, monosodium glutamate, borax, ammonium sulfate, compound fertilizer, dill, silk, soybean meal, vinasse, seeds, slag, sugar and so on.
In a fluidized bed dryer, a fluid material such as a granule, a paste (or a suspension and a solution) is placed on a gas flow distribution plate such as a perforated plate, and a lower portion is supplied with a drying medium having a considerable speed. When the flow velocity of the medium is low, the gas flows between the particles of the material, and the entire material layer does not move; the gas flow rate is gradually increased, the material layer begins to expand, and the gap between the particles increases; and then the gas flow rate is increased, and a considerable portion of the material is suspended. Forming a gas-solid mixed bed, that is, a fluidized bed, because the suspended material in the fluidized bed is very similar to a boiling liquid, so it is also called a fluidized bed, and it exhibits fluid properties in many aspects, for example, has an obvious upper interface. And keep the level; if you increase the flow rate of the airflow, the particles are almost completely taken away by the airflow, and the gas is transported. Therefore, the gas flow rate is the fundamental controlling factor of the fluidized bed dryer, and the appropriate gas flow rate should be between the fluidization of the material layer and the take-up of the material.
The heat transfer of the fluidized bed dryer can be through an outer jacket or an in-bed heat exchanger. When using the in-bed heat exchanger, in addition to the requirements of the general heat exchanger, it must also consider its influence on the material flow in the bed, that is, the form and installation of the heat exchanger should be as beneficial as possible to the normal flow of the fluid. . Practice has proved that when the tube heat exchanger is used, the tube is placed at a distance of 2/5 from the center of the device, and the mud-like material with high viscosity and high water content is difficult to disperse and fluidize in the drying medium flow. Put some inert carrier (such as quartz sand, alumina, oxidized beads, granular salt, etc.) at the bottom of the dryer. When they fluidize under a certain flow of air, the wet material will adhere to the surface. It then becomes a dry outer shell. As the inert carriers collide with each other, the dry outer casing is detached and carried away by the flow of the medium; and the carrier itself is in contact with the new wet material to form a dry outer casing. This cycle allows the fine wet-adhesive material to be sufficiently dried in a fluidized bed dryer.
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