Impeller for aerating sewage sludge - has hub with tubular vanes supporting flat ring with tangential ribs

摘要

A hollow hub fitted with radially projecting tubes, along the generating lines of which slot-like outlets are provided for the escape of air sucked in by the impeller, is assembled on a hollow shaft to form a device for aerating sewage sludge. On the tubes, on the side of the hollow shaft, a flat ring is assembled coaxially with the hub, leaving an annual gap. Between each pair of adjacent tubes, on the surface of the flat ring, a rib is provided which runs at a tangent to the inner edge of the ring. The end of the rib at the periphery extends into the zone of the flow from the outer ends of the tubes rotating with the impeller, in front of the ribs. Pref. the distance between the outer ends of the rib and the outlet of the tube it approaches is one fifth of the distance between the axes of the two adjacent tubes along the arc joining their ends. The outer dia. of the flat ring is the same as that of the impeller. The breadth of the ribs measured below the flat surface is three quarters of the outer dia. of the tubes. The impeller may be inclined to the hollow shaft at an angle of 75-85 degrees. This provides an aerating arrangement for dispersed solid matter in sewage in which a more intensive evacuation of the air sucked in, from between the impeller tubes, is ensured.