Process for the precipitation of aluminum trihydroxide from a supersaturated sodium aluminate solution

Abstract

A process for the precipitation of aluminum trihydroxide from a supersaturated sodium aluminate solution, comprising the steps of (a) supplying a stream of supersaturated sodium aluminate solution and a first stream of aluminum trihydroxide particles as seed particles to a first reaction circuit, (b) maintaining the sodium aluminate stream containing the stream of seed particles in the first reaction circuit under conditions mainly resulting in precipitation and agglomeration of aluminum trihydroxide, (c) passing the stream thus obtained to a second reaction circuit in which the stream is maintained under conditions mainly resulting in precipitation and growth of aluminum trihydroxide particles, (d) passing the stream obtained in the second reaction circuit to a separation/classification unit to separate the stream into a first aluminum trihydroxide product stream comprising the coarser particle size portion, a second aluminum trihydroxide product stream comprising the finer particle size portion and a spent liquor stream, (e) supplying a second stream of aluminum trihydroxide particles to spent liquor and dissolving at least part of the aluminum trihydroxide in the spent liquor and introducing the stream thus obtained into the sodium aluminate solution containing the first fraction of aluminum trihydroxide particles in the first reaction circuit.

Dependencies are inferred from the claim text.