| dc.description.abstract | Municipal incinerator fly ash (MSW fly ash) and electric arc furnace dust (EAF dust) account for the main stream of the industrial hazadrous wastes in the past decade. Their proper treatment and/or disposal remain a risky, costly, and unsolved issue. This study investigated the feasibility of melting such wastes by using a waste derived thermite (WDT) prepared from the reactive constituents in these wastes. The typical thermite reaction between aluminum dross/scrap and oxides such as Fe2O3 and ZnO in EAF dust can not only contribute to the energy required in melting process but also help activate the melting process from the interior of the ash and dust mixture, thus resulting in a slag of good quality.
The results indicate that a ratio of 2.15 of EAF dust to dross by weight will result in the highest energy generated from unit mixture of the WDT, taking into the consideration of the effects of the inert in the mixture. Furthermore, the WDT thus prepared will allow to treat up to 40% (w/w) of MSW fly ash within a range of melting temperature. The melting temperature deceases from 2067℃～1670℃ with an increase in MSW fly ash from 0~40 %(w/w), dependent on the insulation of the reactor wall and the axillary heating. The main species identified in the retrieved slag include Al2O3, ZnO, Fe, CaAl4O7 and Ca2Al2SiO7. Modification of the mixture with SiO2 results in slag with the formation of SiO2 species, instead of CaAl4O7 and Ca2Al2SiO7. The retrieved alloy contains 89~99%(w/w) of Fe as a major species. From the standard tests conducted on size grading, bulk density, absorption and Mohs’’ scale of mineral hardness, it appears that the slag is potentially suitable as recycled aggregates in concrete. Thus as demonstrated in this study from both the material-recycling and energy efficiency points of view, the EAF dust stabilization technology, using waste-derived thermite energy, is both feasible and compelling. | en_US |