| 摘要 |
Process for obtaining aluminium trihydroxide, of mean diameter adjusted on demand in the interval from 2 to 100 microns, of unimodal distribution and of low dispersion, comprising the hot decomposition of an supersaturated solution of sodium aluminate in the presence of a primer consisting of aluminium trihydroxide, and the separation of the resulting solid and liquid phases and the recovery of the solid phase comprised of the precipitated aluminium trihydroxide, said method being characterized in that, in a first step, the aluminium trihydroxide is subjected to a crushing up to the obtention of crushed aluminium trihydroxide having a specific surface BET generated by the crushing at least equal to 1 m<2>/g, and the crushed aluminium trihydroxide is introduced in a hot fraction of the supersaturated solution of sodium aluminate in a quantity such that the total surface of the crushed trihydroxide introduced is at least 10 m<2>/l of said fraction, and the suspension thus formed is agitated during a period of time leading to the precipitation of at least 10 % by weight of alumina present in the supersaturated sodium aluminate solution in the form of aluminium hydroxide particles constituting an auxiliary germ and, in a second step, the decomposition of the remaining fraction of the supersaturated sodium aluminate solution in the presence of the auxiliary germ is carried out, said decomposition leading to the precipitation of aluminium trihydroxide having the desired mean diameter by agitation of the suspension formed up to the obtention of a weighted dissolved Al2O3/caustic Na2O not exceeding 0.8. |
