Process for the preparation of coarse aluminium hydroxide

摘要

A process for the crystallisation of aluminium hydroxide is to be developed which has a high liquor production and yields a coarse hydroxide whose fine content of < 45 mu m is less than 15%. This is made possible by carrying out the crystallisation in a crystalliser cascade which consists of 5-20 individual crystallisers, the purified liquor containing the suspended aluminium hydroxide first flowing through the crystallisers having relatively small volumes before it passes into the relatively large crystallisers, and the residence time of the liquor in all the crystallisers having a relatively small volume being 1/10 to 1/2 of the residence time in the entire cascade.