Results of melting treatment of fly ash from municipal solid waste incinerators are described, and safety and an effective use of slag discharged from the melting treatment are studied. The fly ash has an average particle size of 22 mu m and a melting fluidity point of 1280-1330 degrees C and was able to be melted by using a Kubota melting furnace without any additives. Eighty-eight percent of the fly ash was turned to slag and 12% to dust, which contained a lot of heavy metals such as Pb and Zn. Dioxins in the supplied fly ash were 10 ng TEQ/g, originally, and 99.98% was decomposed by the melting treatment. Dioxin concentrations of slag, fly ash and flue gas from the melting treatment were 0.00, 0.00 and 0.25 ng TEQ/m(3) N, respectively. A leaching test was conducted to confirm the safety of slag. Leaching level of heavy metals from slag was significantly lower than compared to those of bottom and fly ashes from municipal solid waste (MSW) incinerators. It was found that leaching is influenced by pH and the specific surface area of the materials. Furthermore, using slag as a ceramic material, slag was ground and burned at a relatively low temperature (900-1100 degrees C) into a ceramic with strength equal to or more than that of general ceramic tiles. (C) 1997 Elsevier Science Ltd.
