Patent ID: 6555076
Filing Date: 2003-04-29
Classification: C01F

Abstract:
A process line for use in a Bayer process installation for the treatment of bauxite wherein a slurry of bauxite ore in an alkaline aqueous medium is digested at temperature and pressure values to dissolve alumina as sodium aluminate and separated into solids and a pregnant liquor stream from which aluminum hydroxide is precipitated leaving aqueous medium, the process line to raise simultaneously the temperature and concentration of the aqueous medium for use in the bauxite ore digestion, including:a section of interconnected evaporator-flash tanks FT1 to FTn installed in series and through which circulates an aqueous medium coming from the bauxite ore digestion in a digester D; a section of interconnected heaters H0, H1 to Hn installed in series through which circulates the aqueous medium for use in the bauxite ore digestion, each evaporator FT1 to FTn flash tank being connected with each heater H1 to Hn directly associated with each flash tank FT1 to FTn between the flash tanks and the heaters for obtaining vapor circulation; an optional specific evaporation section P for eliminating by evaporation a quantity of water, additional to that removed in the evaporator-flash tank FT1 to FTn; at least one heater H0 connected to a source of live steam installed at the inlet of a mixing device and/or bauxite ore digester by means of the aqueous medium to raise the temperature of the aqueous medium coming from the outlet of the first heater H1 in the heater section H0, H1 to Hn to the temperature required for digestion; and a simultaneous heating and evaporation section for the aqueous medium used in the digestion.