Diagnostic of novel atmospheric plasma source and its application to vitrification of waste incinerator fly ash

The characteristics of a novel atmospheric plasma source generated by a dc double-anode plasma torch have been investigated by measuring its emission spectra and heat flux. The original plasma torch design has been proven to be effective in enhancing the aerodynamic stability and luminous intensity of the plasma arc, as well as the jet length. As an application, a vitrification process based on the double-arc argon plasma has been employed to convert toxic incinerator fly ash into a harmless, stable, and chemical durable product. The vitrified slag exhibits a homogeneous, highly dense, and amorphous glassy structure, which is further confirmed by scanning electron microscopy and X-ray diffraction. The leaching concentrations of the target heavy metals in the slag are decreased significantly and are much lower than the current regulatory thresholds of China and U.S., which reveals that the contaminants have been sufficiently immobilized in the silicate network matrix. It is also determined that the vitrification contributes to the predominant reduction of the specific surface area of the fly ash and to the improvement of the slag hardness. Furthermore, the total concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are also appreciably reduced through the plasma vitrification process with a high decomposition rate of 99.97% in PCDD/Fs and 99.94% in I-TEQ. These results indicate that the vitrified product with good quality has great potential to be used as a viable alternative for construction or geotechnical applications. The vitrification process based on the double-arc plasma technology has been demonstrated to be effective and reliable for the stabilization, detoxification, and recycling of waste incinerator fly ash.