A direct fired system (10, 10') includes pulverizer means (14, 24), classifier means (12, 16, 18, 48, 76), burner means (16, 16') as well as a defined fluid flow path that serves to interconnect the pulverizer means (14, 24) and the classifier means (12, 26, 28, 48, 76) in fluid flow relation with the burner means (16, 16'). In accord with the mode of operation thereof, at the classifier means (12, 26, 28, 48, 76) a separation is had of the stream of the gaseous medium such that a portion of the gaseous medium is recirculated along with the oversize solid fuel particles back to the pulverizer means (14, 24) while the remainder of the gaseous medium is operative to convey the solid fuel particles that are of the desired size from the classifier means (12, 26, 28, 48, 76) to the burner means (16, 16') for burning, i.e., firing, in the latter.