Production of an iron ore concentrate from the iron-rich fraction of power plant fly ash

Conference · Thu Jan 01 00:00:00 EST 1981

OSTI ID:5621772

Dobbins, M S; Burnet, G

Removal of gangue materials, principally silica and alumina, from a magnetically-separated, iron-rich fraction of bituminous coal fly ash shows promise of yielding an iron ore grade concentrate. As separated, the iron-rich fraction contains 65 to 75 weight percent iron oxides or about 50% of the iron originally in the ash. Removal of the iron-rich fraction is a first step in several proposed processes for the recovery of aluminum, titanium, and other metals from fly ash. A hydrothermal caustic extraction followed by a mild acid wash has been found to give a residue containing as high as 95% iron oxides, a concentration that compares favorably with that found in taconite and other concentrate pellets used as feed to blast and electric reduction furnaces. The controlling step in the process is the caustic extraction which dissolves the highly insoluble silica and alumina from the fly ash matrix. As the extraction proceeds, aluminate and silicate compounds precipitate back onto the surface of the iron-rich particles and must be removed by a subsequent acid wash. The precipitate does not interfere significantly with the dissolution of silica and alumina by the caustic solution. Precipitation of compounds during the caustic extraction is not without benefit. During the extraction, the solution rapidly becomes saturated and, if it were not for the precipitation, dissolution of the gangue from the ash would cease. SEM photomicrographs show that the precipitate forms on the particle surfaces where it is readily removed by the acid wash with no significant attack of the iron oxides in the particles. The simultaneous dissolution-precipitation allows use of high solid to liquid ratios and reuse of the caustic as the extraction proceeds. A typical extraction residue contains, on a weight basis, about 65% Fe, 4% Al/sub 2/O/sub 3/, and 2% SiO/sub 2/. Pelleting and sintering should give an iron oxide product suitable for use in the manufacture of iron and steel.

• Research Organization: Ames Lab., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5621772
• Report Number(s): IS-M-357; CONF-8110137-2; ON: DE82004805
• Resource Relation: Conference: Symposium on resource recovery and environmental issues of industrial solid wastes, Gatlinburg, TN, USA, 28 Oct 1981
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
FLY ASH
MATERIALS RECOVERY
IRON OXIDES
EXTRACTION
ALUMINIUM
ALUMINIUM OXIDES
CHEMICAL COMPOSITION
DISSOLUTION
FOSSIL-FUEL POWER PLANTS
METALS
PELLETIZING
PRECIPITATION
PRODUCTION
REMOVAL
SILICON OXIDES
SINTERING
TITANIUM
WASTE PRODUCT UTILIZATION
AEROSOL WASTES
ALUMINIUM COMPOUNDS
ASHES
CHALCOGENIDES
ELEMENTS
FABRICATION
IRON COMPOUNDS
MANAGEMENT
MOLDING
OXIDES
OXYGEN COMPOUNDS
POWER PLANTS
PROCESSING
RECOVERY
RESIDUES
SEPARATION PROCESSES
SILICON COMPOUNDS
THERMAL POWER PLANTS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
320305* - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Industrial Waste Management