GB1453834A - Method of and apparatus for drying particulate materials s - Google Patents

Abstract

1453834 Drying BARR & MURPHY Ltd 29 Jan 1974 [23 Feb 1973] 9140/73 Heading F4G The invention comprises a method of drying material and the apparatus therefor. The method comprises the steps of circulating a drying gas and material around a circuit, feeding moist material to be dried into the gas in the circuit at a feed point where the gas is at a lower temperature than a critical temperature of the material, introducing hot drying gas at a temperature higher than the critical temperature of the material into a zone in the circuit in such manner that the hot gas is introduced into an inner region of the zone, the cooler circulated gas being introduced into an outer region of the zone surrounding the inner region, and continuously withdrawing spent gas carrying dried material from a withdrawal point in the circuit. The apparatus comprises an endless circuit through which drying gas and material may circulate, a manifold 1 defining a zone in the circuit, the manifold having a first inlet 15 on its axis for introduction of hot gas to an inner region of the zone, a second inlet 6 which is offset from the axis of the manifold and at the same end thereof as the first inlet for introducing previously circulated gas containing material to be dried into an outer region of the zone, an outlet 4, and a gas circulator, and feeder 7 for introduction of moist material to the circuit and an exhaust for removing spent gas and dried material from the circuit, the exhaust being connected between the outlet 4 and the feeder 7. A heater 12 is at the entrance to a duct 13 which opens into the manifold 1 through the inlet 15 which has vanes 14 to produce rotary flow of the incoming gas. The hot gas is surrounded by cooler gas carrying the material to be dried, the hot gas cooling as the material is dried. At the outlet 4 a baffle 40 separates the dried from the undried material, the lighter dried material is conveyed to a collector 9 and gas is drawn off through an exhaust fan 10, the heavier undried material passes into a duct 3 for recirculation. The material to be dried may be polypropylene with melting point 150‹ C., air at 225‹ C. enters the inlet 15 and emerges from the exhaust fan 10 at 75‹ C. The drying gas may be nitrogen or combustion gases from a fuel gas.