Centrifugal air classifiers without rotating classifying blades are frequently used in present-day coal-fired power stations. For economical reasons, these obtain the coal to be burnt from different sources so that the pulverized-coal furnaces are operated with coals of varying quality. In this arrangement, it is disadvantageous that, when coals of particularly low quality are burnt, this classifier is not capable of supplying the fineness of pulverized coal required for proper combustion. The invention has the object of creating a centrifugal air classifier of the type initially mentioned which provides the possibility of proper combustion of several types of coal in a pulverized-coal furnace. This object is achieved when, in the feed duct for the mixture of material to be classified and carrier gas, a jacket is arranged which surrounds the coarse-material collecting hopper at a distance and which leaves open an annular gap, which can be more or less closed by adjustable deflecting plates, to the feed duct, and when, at the lower end of the annular space formed by the coarse-material collecting hopper and the jacket a spin-generating ring of regulating flaps is arranged.