Abstract: Granular solid material is dried in a vertically extending annular chamber formed between inner and outer cylindrical walls by a current of high temperature inert drying gas of high humidity passed downward through the material. Material enters the chamber under gravity through a slot in the inner wall, which slot extends round the full periphery of the inner wall, and is removed from the bottom of the chamber by a variable speed discharge system, the rate of entry through the slot being governed by the rate of discharge from the bottom of the chamber so that the top of the column of material is of frusto-conical form. The spent drying gas stream, less a quantity which is discharged, is used to dilute the products of a fuel in air, the high temperature mixture thus formed constituting the drying gas. The quantity discharged has a mass equal to that of the fuel and air forming the products of combustion. An upward current of cooling air may be passed through the lower portions of the column of material.

Abstract: In a pneumatic dryer, a material which gives off an odorous exhaust during drying is dried in a first dryer section by a stream of hot gas, the major part of the spent gas stream being re-heated by the addition of air and burning fuel under pressure to form the said stream of hot gas. The excess spent gas in the first dryer section is passed through an incinerator to pyrolyze the odorous content of the spent gas stream, and the pyrolyzed gases are used to dry a second wet material in a second dryer section and are then passed to atmosphere. The second wet material does not give off an odorous exhaust. In a modified method a wet material which gives off an odorous exhaust when the moisture content of the material falls below a critical value during drying is dried in the second dryer section to a moisture content having a value above the critical value and is then dried to completion in the first dryer section.