Formation of calcium aluminates in the lime sinter process. [Extraction of alumina from fly ash]
A study of the formation of several calcium aluminates from pure components in the lime sinter process was undertaken to determine the kinetics of formation and subsequent leaching using a dilute sodium carbonate solution. The composition CaO 61.98%, SiO/sub 2/ 26.67%, and Al/sub 2/O/sub 3/ 11.53% was used. Isothermal sintering runs of 0.2 to 10.0 h were carried out at 1200, 1250, 1300, and 1350/sup 0/C. When the sintering temperature was below the eutectic temperature (1335/sup 0/C), the ternary mixture behaved like two binary systems, i.e. CaO-Al/sub 2/O/sub 3/ and CaO-SiO/sub 2/. Only one compound, 3CaO.SiO/sub 2/, was formed between CaO and SiO/sub 2/. With lower sintering temperature and shorter sintering time, the ..beta..-phase was dominant. However, when both temperature and time increased, more and more of the ..beta..-C/sub 2/S was transformed into the ..gamma..-phase. Several different aluminates were formed during the sintering of CaO and Al/sub 2/O/sub 3/. The compounds CaO.Al/sub 2/O/sub 3/ and 3CaO.Al/sub 2/O/sub 3/ were observed at all tested sintering temperatures, while the 5CaO.3Al/sub 2/O/sub 3/ phase was found only at 1200/sup 0/C and 12CaO.7Al/sub 2/O/sub 3/ at 1250/sup 0/C or higher. The first compound formed between CaO and Al/sub 2/O/sub 3/ was probably 12CaO.7Al/sub 2/O/sub 3/, but the amount did not increase immediately with time. The first dominant compound between CaO and Al/sub 2/O/sub 3/ was CaO.3Al/sub 2/O/sub 3/. When the calcium ion diffused through the product layer of CaO.Al/sub 2/O/sub 3/, 3CaO.Al/sub 2/O/sub 3/ was formed. If unreacted Al/sub 2/O/sub 3/ were present after the formation of CaO.Al/sub 2/O/sub 3/, CaO.2Al/sub 2/O/sub 3/ would form. Subsequent leaching of the sinters showed that the extractable alumina in the products increased with both sintering temperature and time, reaching a max of about 90%. These extraction data corresponded very well to the quantities of aluminates in the sinters. 59 figures, 13 tables.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5721351
- Report Number(s):
- IS-T-875
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
ALUMINIUM OXIDES
MATERIALS RECOVERY
CALCIUM OXIDES
PHASE STUDIES
FLY ASH
RECYCLING
SILICON OXIDES
ALUMINATES
CALCIUM COMPOUNDS
CALCIUM SILICATES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
LIMESTONE
SINTERING
WASTE PRODUCT UTILIZATION
AEROSOL WASTES
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CARBONATE ROCKS
CHALCOGENIDES
FABRICATION
KINETICS
MANAGEMENT
OXIDES
OXYGEN COMPOUNDS
PROCESSING
REACTION KINETICS
RECOVERY
RESERVOIR ROCK
ROCKS
SEDIMENTARY ROCKS
SILICATES
SILICON COMPOUNDS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
010800* - Coal
Lignite
& Peat- Waste Management
320305 - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Industrial Waste Management