Date of Award
Doctor of Philosophy
Chemical and Biological Engineering
The carbochlorination of alumina and fly ash slurried with carbon in a NaCl-AlCl(,3) fused salt using chlorine was investigated at temper- atures between 530 and 800(DEGREES)C. The chlorination rates for up to 85g of alumina or 25g of fly ash in 375g of fused salt containing as much as 45g carbon were determined. Alumina chlorination rates ranging from 2.1(10('-4)) to 1.7(10('-3)) g-moles min('-1) were observed at tempera- tures between 530 and 800(DEGREES)C using a carbon loading of 12.86g. Recoveries of 73% Al(,2)O(,3), 83% Fe(,2)O(,3), 60% TiO(,2) and 25% SiO(,2) were obtained by chlorinating fly ash for 1 hr at 750(DEGREES)C in a melt containing 40% AlCl(,3);The chlorination of alumina was found to be strongly influenced by temperature, and carbon loading. The reaction was gas-liquid mass transfer controlled above 650(DEGREES)C and was reaction controlled at the carbon surface below 600(DEGREES)C. A change in the reaction mech- anism at 650(DEGREES)C is attributed to the stability of phosgene. There was also evidence of a reduction in the carbon reactivity with time. At temperatures above 650(DEGREES)C the ratio of carbon to alumina influenced the gas-liquid mass transfer of chlorine;The chlorination of fly ash at 750(DEGREES)C using a melt containing 40% AlCl(,3) was found to selectively chlorinate alumina with respect to silica at a weight ratio of 5.46 compared to a 2.55 ratio using a melt containing 48% AlCl(,3). The chlorination of iron and titanium oxides was not affected by the melt composition;Based on the results of the study, a preliminary design was developed for the chlorination of 10('4) Kg fly ash hr('-1) in a bubble;column reactor operating at 2.25 atm with a total slurry volume of 21 m('3); * DOE Report IS-T-1220. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy, and sup- ported in part by the Iowa State Mining and Mineral Resources and Research Institute under U.S. Bureau of Mines Allotment Grants G1144119 and G1154119.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Michael Sean Dobbins
Dobbins, Michael Sean, "Carbochlorination of metal oxides using a fused salt slurry reactor " (1986). Retrospective Theses and Dissertations. 8240.