Process for recovery of silica followed by alumina from coal...

Details Process for recovery of silica followed by alumina from coal... Process for recovery of silica followed by alumina from coal...

2011-01-18

2011-01-18

Mayes, Melvin C (Department: 1793)

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Group iiia metal or beryllium

Reexamination Certificate

active

07871583

ABSTRACT:
A process for recovery of silica and alumina from fly ash, in which, Si is leached out from the fly ash in the form of Na2SiO3using a NaOH solution of NaOH >40% (w/w), followed by separation to obtain a Na2SiO3solution and a residue having Al—Si ratio ≧2; vaporizing the solution to obtain Na2SiO3solutions of various concentrations, or producing silica by carbonation, and producing Al2O3by prior art methods from residues obtained after alkali-leaching, ultimately producing filler or cement from the residue after the recovery of Al. The method permits recovery of Al2O3directly from fly ash by removing Si before recovering the Al, which raises the Al—Si ratio of the residue after alkali-leaching and thus simplifies the recovery of Al2O3and raises the rate of Al recovery from fly ash. The invention further includes calcining high Al coal gangue, kaolinite and middle-low-class bauxite at 900-1100° C.

REFERENCES:
Lin et al, the complex chemical treatment of alumina-silica-containing materials, 1998, journal of materials synthesis and processing, vol. 6 No. 1.
Blanco et al, variation in fly ash properties with milling and acid leaching, 2005, fuel, 84, pp. 89-96.

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