US Patent 7343699 Method and apparatus for drying

The method of removing moisture from a material contained within a dryer (3) comprises heating a first stream of gas (A3); passing the heated stream of gas through a dryer (3) to extract moisture from the material to be dried; returning a first portion (E3) of the used gas from an outlet of the dryer (3) to the heater (2), re-heating the second stream of gas (E3) in the heater (2); and passing the heated second stream (B3) back into the dryer (3), wherein the first stream of gas (A3) is atmospheric air from which at least a proportion of the nitrogen present therein has been removed, to thereby increase the percentage by volume of oxygen in the first stream of gas (A3).