Abstract: A method and apparatus for decomposing a sodium aluminate liquor supersaturated with alumina, obtained from alkaline action on bauxite by the Bayer process, is initiated by introduction of alumina trihydrate seed, thereby forming a suspension. The suspension is fed in at the top of a non-agitated reactor described as a "decomposer", and removed from the bottom of the decomposer; the speed at which the suspension moves downwardly is regulated at 1.5 to 10 meters per hour. The apparatus comprises a cylindrical-conical reactor which is fitted with an arrangement for feeding in the suspension at the top, and with an arrangement for taking out the suspension at the bottom. In one embodiment of the apparatus the suspension is taken from the base of the decomposer through an internal tube, with air injected into the bottom of it, is raised to the level of the top of the decomposer and is then sent downstream.

Abstract: The invention concerns a method and apparatus for decomposing a sodium aluminate liquor supersaturated with alumina, obtained from alkaline action on bauxite by the Bayer process, decomposition being initiated by introduction of alumina trihydrate seed to trigger the decomposition, thereby forming a suspension. In this process the suspension is fed in at the top of a non-agitated reactor described as a "decomposer", and removed from the bottom of the decomposer; the speed at which the suspension moves downwardly is regulated at 1.5 to 10 meters per hour. The apparatus comprises a cylindrical-conical reactor which is fitted with an arrangement for feeding in the suspension at the top, and with an arrangement for taking out the suspension at the bottom. In one embodiment of the apparatus the suspension is taken from the base of the decomposer through an internal tube, with air injected into the bottom of it, is raised to the level of the top of the decomposer and is then sent downstream.