This disclosure concerns embodiments of an annealing device and a method for annealing flowable, finely divided solids, such as annealing granular silicon to reduce a hydrogen content of the granular silicon. The annealing device comprises at least one tube through which flowable, finely divided solids are flowed downwardly. The tube includes a heating zone and (i) a residence zone below the heating zone, (ii) a cooling zone below the heating zone, or (iii) a residence zone below the heating zone and a cooling zone below the residence zone. An inert gas is flowed upwardly through the tube. The tube may be constructed from two or more tube segments. The annealing device may include a plurality of tubes arranged and housed within a shell. The annealing device and method are suitable for a continuous process.