Abstract: A draft tube mixer is disclosed particularly adapted for use with digestion processes and apparatus wherein a vertical shaft (13) is driven by motor (15) through a suitable drive (14) to rotate a ragless propeller (12). The propeller (12) has a series of three lobes or blades (40-42) which are concentrically arranged at 120.degree. apart positions so that the minimum diameter of the blades are at the ends of a hub (43) from which the blades integrally extend. The blades extend over the length of the hub over about a 360.degree. of rotary motion helix. The blades (40-42) are symmetrical from their ends to the mid points on the vanes from either direction top or bottom so that the propeller is reversible without loss of efficiency.

Abstract: A draft tube mixer is disclosed particularly adapted for use with digestion processes and apparatus wherein a vertical shaft (13) is driven by motor (15) through a suitable drive (14) to rotate a ragless propeller (12). The propeller (12) has a series of three lobes or blades (40-42) which are concentrically arranged at 120.degree. apart positions so that the minimum diameter of the blades are at the ends of a hub (43) from which the blades integrally extend. The blades extend over the length of the hub over about a 360.degree. of rotary motion. The blades (40-42) are symmetrical from their ends to the mid points on the vanes from either direction top or bottom so that the propeller is reversible without loss of efficiency.