discharge chamber 7 are interconnected in the transition zone between the cylindrical part 2 and the conical part 3 via openings 12 in the chamber walls 5 a screw conveyor 13 which is mounted rotatably in a discharge pipe 14 is located at the bottom of the discharge chamber 7 the upper portion of the cylindrical part 2 of the apparatus is provided with a corresponding screw conveyor 15 located in a feed pipe 16 debouching into the upper portion of the first drying chamber 6 a pipe heat exchanger 20 fills the central portions of the cylindrical part 2 the conical part 3 and in part the top part 4 the heat exchanger being connected to a pipe 21 for supplying superheated steam which as explained below is passed from the top part 4 to the bottom part 1 of the apparatus via a large number of heat exchanger pipes 22 while at the same time being heated by the superheated steam supplied through the pipe 21 furthermore the heat exchanger 20 is connected to a pipe not shown for discharging condensate from the area around the pipes of the heat exchanger 22 the top part 4 is divided into a central chamber 31 and a transfer chamber 32 by means of a plate 30 a stationary filling element 33 is provided in the central chamber.