What Is a Fluid Bed Dryer?

Fluidized bed dryer is a kind of agitator dryer with special form of steelmaking equipment which is stirred by fluid.

Fluidized bed dryer

The drying speed of the fluidized bed dryer is very fast, the temperature in the fluidized bed is uniform and easy to control and adjust, and the time is relatively easy to choose, so it can obtain dry materials with extremely low moisture content.

There are three main types of fluidized bed drying equipment: continuous, semi-continuous, and intermittent production. According to the structure, there are many forms such as single-layer, multi-layer, horizontal multi-chamber pulse, cone, and spray, vibration and inert carriers. When this kind of dryer is used to dry ammonium oxide, the exhaust temperature is 50-60, the operation is negative pressure, the particle size of the material is 250 ~ 420, and it stays in the machine for 120S.

Fluidized bed dryer is to place powdery, granular, paste-like (even suspension and solution) and other fluid materials on air distribution plates such as perforated plates, and send the drying medium with a considerable speed from the lower part. When the velocity of the medium is low, the gas flows between the particles of the material, and the entire material layer does not move; gradually increasing the air velocity, the material layer begins to expand, and the gap between the particles increases; when the air velocity is increased, a considerable part of the material is suspended. It forms a gas-solid mixed bed, that is, a fluidized bed. Because the suspended material in the fluidized bed is like a boiling liquid, it is also called an ebullated bed, and it presents fluid properties in many aspects, for example, it has an obvious upper interface. And keep the level; if you increase the airflow velocity, almost all the particles are taken away by the airflow, and it becomes a gas transport. Therefore, the airflow speed is the most fundamental control factor of the fluidized bed dryer, and the appropriate airflow speed should be between the fluidization of the material layer and the carrying out of the material.

Heat exchange in a fluidized bed can be through an outer jacket or an in-bed heat exchanger. When using the heat exchanger in the bed, in addition to the requirements of the general heat exchanger, it must also consider its impact on the material flow in the bed, that is, the form and installation of the heat exchanger should be as conducive to the normal flow of the fluid as possible. . Practice has proved that when using a tube heat exchanger, the tube is placed at a distance of 2/5 from the center of the equipment, and it is difficult to disperse and fluidize the mud-like material with high viscosity and high moisture content. Put some inert carriers at the bottom of the dryer (such as quartz sand, alumina, oxidized pellets, granular salts, etc.). When they are fluidized by a certain flow of air, they will stick wet materials on their surface. It then becomes a dry shell. Because the inert carriers collide with each other, the dry shell will fall off and be taken away by the medium flow; and the carrier itself will contact the new wet material to form a dry shell. In this way, the fine wet sticky material can be fully dried in a fluidized bed dryer.