Heated process air is supplied to a special perforated distributor bed plate. Via the bed plate the hot air flows through the layer of solids at a velocity sufficient to support the weight of particles in a fluidized state. The heat in the air is used to evaporate moisture from the product. The drying air picks up moisture and cools down during the evaporation. This means that for example the supply air can be 90°C but as a result of the evaporation, the product temperature will stay at 60 °C. The bed plate is made of stainless steel and will have a temperature that is higher than the 60 °C. In some cases it essential not to overheat the product.
This is also in case of Copper Sulfate drying: The pentahydrate (CuSO4·5H2O), the most commonly encountered salt, is bright blue. If the blue pentahydrate is overheated, the Copper Sulfate turns into the anhydrous form which is white, while the water that was present in the pentahydrate form evaporates. Tema Process has developed a special system to control the temperature of the bed plate by using a COOLING system to cool the bed plate. Result is an accurate temperature control to prevent uncontrolled overheating of the blue pentahydrate (CuSO4·5H2O).