Problems are often experienced when handling powdery and fine-grained bulk materials, such as flour, cement, pigments, soot, pesticides or fine plastic powders: storage, mixing and discharge are difficult, because these fine-grained powders do not flow freely. They tend to agglomerate and form bridges or tunnels around the silo outlet and, therefore, can only be removed effectively using some sort of discharge aid.
Fluidizing is a special application of modern fluidized bed technology for the treatment of bulk material of small particle size. Aim of this process is to loosen, mix and discharge powdery bulk materials with grain diameters between 10 and 200 µm by injecting air.
For fluidization, porous bottoms or aeration units are assembled at the inner surfaces of bins and silos. Air is blown into the bin through the whole area of these porous units to fluidize the stored bulk material, i.e. to set it into a liquidlike state.
When fitting-out large silo areas with aeration units, it is advantageous to divide them into sectors each of which can be inter-changeably aerated. In this way it is possible to aerate even large areas with relatively low air quantities. In many cases it is sufficient to compensate the pressures produced during storage of the bulk material by the inflowing air.