Swirling Melting Characteristics of Fly Ashes from Co-Firing of MSWI in China

Melting treatment is an efficient for heavy metal stabilization in MSW fly ash. The fly ashes from co-firing of municipal solid waste and coal incinerator were melted in the swirling melting furnace system under various temperatures. The melting characteristics and behavior of heavy metals of fly ashes were investigated in detail under different melting temperatures. The results showed that the melting temperature was important factor on the melting characteristics of fly ashes. The melting temperature should exceed the fusion point of fly ashes between 50°C to 80°C. Heavy metals of low boiling points were readily emitted into flue gas during swirling melting treatment. The sample happened to sintering reaction or part melting reaction at the lower range melting temperature between 1250 to 1300°C. The fly ashes samples would be transformed to the glassy state at the higher melting temperature 1400°C. The melting temperature range is between 1250 to 1400°C, the fixation rates of nickel, chromium, copper, cobalt, and manganese are slowly increased with melting temperature enhancement during melting process. These results indicated that the swirling melting would remarkably boost the fixation rates of non-volatile heavy metals when the melting temperature is above 1350°C. The changes of melting temperature have marked affect on the fixation rates of arsenic, lead, cadmium, and zinc. Samples are melted treatment at 1350°C while the maximum fixation rate of lead would be up to 41.5%. The fixation rate of cadmium would reach the highest value 33.3% at 1300°C. The leaching test on melted slag samples showed that the fly ashes were successfully detoxified to meet of the limits toxicity characteristic leaching procedure (TCLP) in China and United States.