Abstract: In a self-supporting stirrer for mixing a bed of free-flowing solids, the lower end of the stirring device, facing the bottom of the stirred vessel, passes into a hub. The hub is located on a vertical drive shaft which extends through the bottom of the stirred vessel and consists of shaft sections detachably joined to one another. The drive shaft itself is carried in a cage attached to the bottom of the stirred vessel and can be adjusted vertically by means of a lifting device. This opens or closes an annular gap between a centering cone, provided at the bottom of the stirred vessel, and a conically recessed ring, inserted in the hub. In this way, the need to empty the vessel, for example when carrying out maintenance or repair work, is avoided.

Abstract: A spiral stirrer unsupported at one end, for mixing and stirring free-flowing solids, especially in continuous gas phase polymerization. The stirrer comprises a plurality of turns formed from hollow profiles. The botton end of the spiral, facing the bottom of the stirred vessel, is attached to a hub seated on a drive shaft. In the vicinity of the transition from the hub to the first turn of the spiral, a distributor spiral is provided to avoid flowless zones in the hub region. Uniform distribution of the gas entering at the bottom of the vessel is also achieved.