A process and an apparatus for drying of a material in the form of a paste or a filter cake in a spin flash dryer. Particles are separated by a classifier (6) in the chamber (1) in such a way that oversize fraction is withheld in the chamber (1) and the desired fraction is removed (3, 9). A possible undesired undersize fraction is strained off and recycled (4, 10, 11) externally back to the dryer chamber (1). The spent drying gas is recycled to the dryer chamber (1). In either, the energy in the spent drying gas may be made use of in a heat exchanger and there is no or only little emission to the environment. Products preferably dried according to the invention are fruit and beet pulps, destillers residues, pesticides, pigments, dyes, ceramics, active coal, sludge and zeolites.