Title: Process for continuously producing alumina using bayer process from 1 hydrate bauxite
Application Number: 85107051 Application Date: 1985.09.26
Publication Number: 1005251 Publication Date: 1986.11.26
Approval Pub. Date: 1990.01.24 Granted Pub. Date: 1990.01.24
International Classifi-cation: C01F7/06
Applicant(s) Name: Aluminum Pechiney Co. Address:
Inventor(s) Name: Jan Lippitit
Attorney & Agent: QUAN JING WU DAJIAN
Abstract:
    A process for the continuous production of alumina by means of the Bayer process by alkaline attack in reactors on bauxites which primarily consist of aluminum monohydrates and contain silica in a free state or combined in the form of aluminum silicate, the essential aim of which is to delay scaling of the reactors by deposits of sodium silico-aluminate on the reactor walls. The process comprises the following steps: the bauxite is put into suspension by crushing in a sodic liquor; the suspension is raised to a temperature of from 90 DEG to 108 DEG C and held at that temperature for a period of time sufficient to convert at least 75% of the aluminum silicate contained in the bauxite into insoluble sodium silico-aluminate; The suspension is then subjected to steam heating by passing through a tube-type heat exchanger under pressure at a temperature which is preferably is from 160 DEG to 230 DEG C and preferably from 230 DEG to 290 DEG C and maintained at that temperature so as to solubilize at least 90% of the extractible alumina; and the suspension is returned to atmospheric pressure by successive expansion operations, with recovery of the steam.
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