Research On The Melting Treatment Technique Of Municipal Solid Waste Incinerator Residues

Incineration of municipal solid waste (MSW) can cause secondary pollution because of the contamination of MSW Incinerator residues. Thus the treatment of MSW incinerator (MSWI) residues has become one of the urgent problems to be solved which related to both environmental and social considerations. Melting treatment of MSWI residues especially fly ashes have been concerned more and more.In this paper, the physical-chemical properties and the melting characteristics of bottom ash and fly ash from two MSW incinerating plants in east China were analyzed. The cold-state simulation and simplified hot-state simulation of the melting furnace we designed were performed by using the CFD software-FLUENT.The chemical compositions of bottom ash and fly ash were obtained by X-ray fluorescence (XRF). Furthermore, the element composition of fly ash was acquired by X-ray energy dispersive microanalysis (EDX, EDS) and the microstructure by scanning electron microscope (SEM) respectively.Experiment of melting treatment of bottom ash and fly ash were performed on a tubular heater. Influence of temperature on the melting characteristics of bottom ash was analyzed by SEM. Experiment results indicate that better effect of melting was obtained at the temperature of 1400℃. Influence of time, temperature, different additives and the amount of additives on the melting characteristics of fly ash was analyzed from different points of view such as ignited loss, transfer of heavy metals and microstructure. According to the results, the fly ash can be completely melted after heated for 90 minutes at the temperature of 1400℃. Better melting effect of fly ash were obtained by adding certain amount of SiO2 additive compared to adding CaO or Al2O3. There has an optimum amount of SiO2 addition because superfluous SiO2 decreases the stabilization rate of Cr, Ni, Cu, As in melting products.The coal-gasification-cyclone-furnace technique was conceived and the melting furnace for experiment was designed. The cold-state simulation and simplified hot-state simulation of the furnace were carried out by using FLUENT. The different influence of the position of secondary air inlet and the measure of the inlet on cold-state fluid field were discussed. Simulation results indicate that secant inlet do not have significant effect on the fluid field in the furnace compared to tangent inlet. The hot-state simulation results show that the fluid in the furnace can not form rotation because of the effect of both the increased viscosity of hot air at high temperature and the small size of the furnace.