Process for the continuous production of alumina from bauxites containing monohydrates using the bayer process
US4647439A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 19, 1986 |
| Grant date | Mar 3, 1987 |
| Priority date | — |
| Expiry date | May 19, 2006 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01F7/47
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
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: (1) the bauxite is put into suspension by crushing in a sodic liquor (aqueous solution of caustic soda); (2) the suspension is raised to a temperature of from 90.degree. to 108.degree. 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; (3) The suspension is then subjected to steam heating by passing through a tube-type heat exchanger under pressure at a temperature which is at least equal to 160.degree. C. and preferably is from 160.degree. to 230.degree. C., with a speed of rise in temperature of from 2.degree. to 12.degree. C./minute and with a speed of flow in the tubular reactor of from 0.4 to 7 meters per second; (4) by heat exchange with …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.