Drying plant for pulverulent prods. e.g. for dried milk powder prodn. - in which preheated hot air is circulated and controlled so that its discharge temp. is practically constant

摘要

Hot air drying plant comprises a drying chamber, a hot air feed circuit with a pre-heater for the outside air, an evacuation circuit for the hot air charged with vapour and an air-to-air heat exchanger. The outside air is drawn by a fan through nozzles and the heat exchanger; it passes in turn through a battery of filters and a heater to reach the drying chamber via a pipe. The prod. to be dried, mixed with a solvent (generally water), is sprayed into the hot air current. The air gives up its heat and takes up vapour; any solid particles are removed by a cyclone and it is carried by a fan to the hot side of the heat exchanger before discharge to the atmos. The dried prod. is withdrawn from the base of the drying chamber and that of the cyclone for further treatment. As the outside air is preheated with heat that would otherwise be lost, less heat is required.