[Study on vitrification of simulated medical wastes by thermal plasma].

The simulated medical wastes with different feed compositions were vitrified in a thermal plasma reactor, the core of which was a DC double anode plasma torch. The purpose of this study was directed towards the mobility characteristics of heavy metals contained during the vitrification process, the leaching behavior of heavy metals in the vitrified slag and the effectiveness of vitrification were investigated. Results indicated that the morphology of vitrified slag was amorphous state which showed the mostly glassy slag of SiO2 and the microstructure of slag was very compact. This thermal plasma could be effectively utilized for encapsulation of heavy metal in wastes, as the vitrification ratio was between 68.5% - 89.4%. Toxicity characteristic leaching procedure results showed that the slag had an excellent resistance against leaching of heavy metal ions. Except that the leaching concentration of Cd was lower than the detecting limit, those of Ni, Cr, Zn, Cu and Pb were much lower than that specified in relevant national standards. These results indicate that, with the proper feed compositions, the thermal plasma disposition is an alternative technology with a highly efficiency to dispose medical wastes.

Destruction of PCDD/Fs by gliding arc discharges.

PCDD/Fs have been become a serious issue because of their toxicological effects and associated adverse health implications. In this study, the gliding arc plasma was tested for treatment of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), which was synthesized from pentachlorophenol in atmospheric condition at 350 degrees C with or without the catalysis of CuCl2. From the experiment, we found that the destruction efficiency of PCDD/F homologues after gliding was discharge ranged from 25% to 79%. This result demonstrates that gliding arc plasma is an effective technology to decompose PCDDs/Fs in flue gas. A plausible degradation mechanism for PCDD/Fs by gliding arc was discussed. Finally, a multistage reactor structure of gliding arc was proposed to upgrade removal efficiency for PCDD/Fs.