Formation of calcium aluminates in the lime sinter process. [Extraction of alumina from fly ash]

Technical Report · Sat Mar 01 04:00:00 EST 1980

DOI:https://doi.org/10.2172/5721351· OSTI ID:5721351

Chou, K. S.

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., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5721351
• Report Number(s): IS-T-875
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010800* -- Coal
Lignite
& Peat-- Waste Management
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320305 -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Industrial Waste Management
AEROSOL WASTES
ALKALINE EARTH METAL COMPOUNDS
ALUMINATES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CALCIUM SILICATES
CARBONATE ROCKS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
FABRICATION
FLY ASH
KINETICS
LIMESTONE
MANAGEMENT
MATERIALS RECOVERY
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PROCESSING
REACTION KINETICS
RECOVERY
RECYCLING
RESERVOIR ROCK
ROCKS
SEDIMENTARY ROCKS
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SINTERING
WASTE MANAGEMENT
WASTE PROCESSING
WASTE PRODUCT UTILIZATION
WASTES