Abstract: Inner and outer cylinders are mounted for rotation about a common horizontal axis. Powder is fed into one end of the inner cylinder to produce granules by coagulation as the cylinder rotates. The inner cylinder is open at the other end to provide an outlet for the granules, and has a perforated (mesh) wall portion towards its outlet end through which uncoagulated powder falls into the outer cylinder. The diameter of the latter increases towards the inlet end of the inner cylinder so that the uncoagulated powder travels back down the surface of the outer cylinder as it rotates. On reaching the end thereof adjacent the inlet end of the inner cylinder, the powder is lifted by scoops on the inner surface of the outer cylinder to fall into an open-topped duct by which powder is fed into the inner cylinder.