Effect Of Additives On High Temperature Melting Of Waste Incineration Fly Ash

Increasing production of garbage has gradually become a hot topic,incineration treatment is a good harmless means.The fly ash in the process of incineration is hazardous waste,which contains dioxins,heavy metals and other toxic substances.By melting at high temperature,dioxins can be completely decomposed,and heavy metals can be dissolved in the slag.But the melting temperature of fly ash is higher than1400?.The melted slag can be used as paving bricks and building materials.Under the above background,the effects of five additives?CaO,Al₂O₃,SiO₂,glass and coal ash?on the melting point,weight loss and volume reduction of fluidized bed fly ash and grate fly ash during high temperature melting were studied.Firstly,the physical characteristics,chemical structure characteristics,leaching characteristics of heavy metals and heat treatment characteristics of two kinds of fly ash were investigated.The results show that the main metal elements in fly ash are Ca,Si and Al,and there are a lot of chlorine elements in fly ash,which cause a lot of volatilization during heating.The leaching concentration of Cd and Pb in fly ash exceeded the limit.Secondly,five kinds of additives?CaO,Al₂O₃,SiO₂,glass and coal ash?were mixed with fly ash at the ratios of 5%,10%,15%,20%and 25%,and compared with fly ash without additives.The variation rules of ash melting point,weight loss rate and volume reduction rate were analyzed.It is found that SiO₂,glass and coal ash have good effects on reducing the melting temperature of the two kinds of fly ash.When the alkalinity is close to 1,the influence on the flow temperature,weight loss rate and volume reduction rate of fly ash is the greatest.Finally,analyze the law of fly ash melting and select the best additive to analyze the molten glass.There is a correlation between meltability and weight loss rate and volume reduction rate.Comprehensive analysis shows that fluidized bed fly ash with20%glass and and grate furnace fly ash with 25%coal ash have the best ash fusibility.It was found that Ca,Si,Al and O are the main elements in vitreous body,which are CaO-SiO₂-Al₂O₃ eutectic.The toxic leaching of heavy metals meets the national standards.