In a rotating grate having a rotational-symmetrical shape having an axis of rotation which is inclined against a horizontal plane by more than 34.degree., and which encloses a combustion chamber for the combustion of slag-forming fuel, which is locked on a lower end and is open at an upper end and is defined by meridionally extending carrier arms that are hollow and are connected to a compression air source and are provided with blow openings directed into the combustion chamber, the combustion chamber has a spherical shape, or in the borderline case a cylindrical shape with a radially extending lower front side, the angle of inclination of the axis of rotation against the horizontal is between 36.degree. and 46.degree., the carrier arms in the combustion chamber are flush with the remaining grate surface, and the inner contour of the combustion chamber encloses an angle of 90.degree. with the axis of rotation in the area of the closed end. Thereby, an intense circulation of the combustible on the rotating grate is caused in operation, which avoids the formation of slag adhering to the grate.