Investigation On Vitrification Of Simulated Medical Wastes By Thermal Plasma

MW (medical wastes)are infectious, toxic and harmful, the disposal of MW with volume and weight reduction has become more and more important. The types of MW have a dramatic impact on the selection and performance of technologies for treatment. For instance, the conventional incineration is not suitable for treating non-combustible waste. Thus, pre-sorting of waste is required. In addition, the ash residue from incineration needs further consolidation prior to proper landfill disposal.The emergence of thermal plasma technology in recent years has received a great deal of interest for its many advantages when used for treating mixed forms of waste due to its energy intensity and high temperature.In this paper, with the analysis of the thermogravimetric behaviour and gas production characteristics of MW, a double arcs DC plasma torch was developed to vitrify MW. The mobility characteristics of heavy metals contained during the vitrification process, some physical and chemistry characteristics of vitrified slags and the leaching behavior of heavy metals in the vitrified slag were investigated. Besides, in order to study the effect of additives on physical and chemistry characteristics of vitrified slags, CaO with the different proportion were mixed into MW. And it established bases on vitrification of MW and resource utilization of slag.With the application of TG-FTIR, the thermogravimetric behaviour and gas production characteristics of typical medical waste components and simulated combustible medical wastes were analyzed in both pyrolysis and burning condition. From the study, an in-depth understanding about pyro lysis-incineration characteristics of MW was obtained.With the main components of MW in our country, the simulated medical wastes with different feed compositions were vitrified in a thermal plasma reactor. Then a Scan Electron Microscope, an X-ray diffractometer, EDS, Differential thermal analysis and the Archimedes Method were taken to investigate physiochemical properties of the vitrified slag, such as exterior appearance, morphology, elements characteristic, thermal stability and density. TCLP analysis was employed on vitrified slag in order to analyze the metals leachability. Results indicated that the morphology of vitrified slag was amorphous state which showed the mostly glassy slag of SiO2and the microstructure of slag was very compact. The slag density increased as a result of increased metallic feeds. Besides, the density and mechanical properties of slag are similar with that of the glassy materials. The vitrification ratio indicated that thermal plasma could be effectively utilized for encapsulation of heavy metal in the wastes. Toxicity characteristic leaching procedure results showed that the slag had an excellent resistance against leaching of heavy metal ions. The leaching concentrations of heavy metals were much lower than that specified in relevant national standards. CaO was used to improve the effect of vitrification of MW. The results showed that CaO could promote melting, and the slag had better thermal stability. These results indicate that, with proper feed compositions, the thermal plasma disposition is an alternative technology with high efficiency to dispose MW.