Experimental Study On The Melting Of Municipal Solid Waste Incineration Fly Ash

Due to reduce, resource, harmless, Incineration is an increasingly adopted technology for the WSM all over the world. The incineration fly ash brought by refuse incineration power plant is listed as hazardous substance for its heavy metals with highly leaching toxicity and relative compounds, so it should be particularly treated. Melting treatment technique is gradually becoming the new spot of the solid waste treatment area because it can efficiently control the heavy metals.MSWI fly ash used in this study was from the Chongqing Tongxing MSW Incineration Plant. The fundamental research of incineration fly ash melting technique was done. Firstly, the properties of fly ash, such as chemical characteristics,physical characteristics,micro-morphology,mineralogical characteristics, leaching toxicity and so on, were analyzed. The results show that: the appearance of incineration fly ash is loose and overlapped as sphere,ellipse and flake; the specific surface area of incineration fly ash is large and its chemical composition is complicated: CaO,SiO2 and Al2O3 are the principal components, and the content of heavy metals such as Cr,Mn,Cu,Zn,Pb,Hg,Cr is very little. And most of the heavy metals existed as their oxides and the concentration of Cr, Zn, Pb, Cd in leaching solution exceeded badly the national standard.Through the incineration fly ash direct melting experiment; the effect of melting temperature, melting period, basicity on melting characteristics of fly ash and the migration characteristics of heavy metals was studied. The experimental results show that: the migration characteristics of heavy metals differ a lot with the different elements during the process of fly ash direct melting. Cr, Mn, Cu are difficult to volatilize while Zn, Pb, Cd, Hg are easy to volatilize. The optimal conditions of fly ash direct melting were achieved based on serial experiments : 1350℃melting temperature,25min melting period,1.1 basicity.Heavy metals behavior between slag phase and iron phase was studied during molten iron bath. We can see almost all higher boiling point heavy metals, such as Cr,Mn,Fe,Cu were in iron phase, moreover, Fe,Mn,Cr,and Cu content up to 90%,60%60%and70% respectively. Therefore,the conclusion could be proposed when melting temperature was 1350℃,melting time was 25min,the basicity is 1.1, iron/slag ratio was 1:1, effect is the best. After the direct melt and molten iron bath of incineration fly ash: the production of ash and slag reduce a lot; microstructure turns to be more impact and the concentration of the leaching toxicity goes under the standard; the heavy metals would turn into iron phase and become alloy in the stabilization of fly ash molten iron bath, so it is feasible for molten iron bath to be applied in metallurgy area.