A drum dryer comprises a drying drum which is arranged for a gas to flow through it to be dried from a first end of the drum to its opposite second end, and a housing in which the drum is located with a space around the drum between the internal wall of the housing and the external surface of the drum. Gas can be directed into the space through a housing inlet, to flow in the space to the first end of the drum where it can be admitted into the drum for drying.