Study On The Influence Of Water Washing Pretreatment And Additives On The High Temperature Melting Of Fly Ash

Waste incineration technology has been widely promoted due to its advantages in capacity reduction rate and resource utilization.However,in the process of high-temperature incineration of waste,part of fly ash will be produced.The fly ash contains heavy metals such as Pb,Cd,Cu,Zn,etc.,and has high leaching concentration,which indirectly threatens human health.Therefore,in the current laws and regulations of China,there are documents that make sure that the fly ash is classified as hazardous waste.It is necessary to study the fusibility of fly ash and find an effective way to reduce its melting temperature.In this paper,the influence of water washing pretreatment and additives on the fusibility of fly ash,as well as the material change in the process of high temperature melting are studied.Try to understand the changes of elements and compounds composition of fly ash after water washing pretreatment,as well as the changes of melting temperature and melting process after water washing.The results show that after the fly ash is pretreated by water washing,the main elements of which are Cl,Ca,K and Na.The melting temperature is 43 ? 100 ? lower than that without pretreatment.The weight loss rate of the fly ash in the washing process is 21.79%.Secondly,five kinds of single additives?calcium oxide,aluminum oxide,silicon dioxide,iron oxide and magnesium oxide?were added into the fly ash respectively in different proportion,and the influence of five additives on the high temperature melting of fly ash are studied and analyzed.It is found that the other four additives,except Mg O,can reduce the flow temperature of fly ash in a certain range.Compared with before adding five additives,the volatilization rate of fly ash melting decreased to a certain extent.Adding appropriate additives can promote the vitrification process of fly ash and inhibit the volatilization of substances to a certain extent.Finally,the orthogonal experiment is designed to study the proportion of several additives with better control effect.The experimental data are compared and analyzed to prepare composite additives,so as to minimize the temperature required for fly ash vitrification products.In order to judge whether the vitrified products can meet the relevant standards,XRF element analysis,XRD crystal image analysis,heavy metal element content and toxicity leaching characteristics of the vitrified products after melting fly ash and additives were tested.It is found that the change of Si O₂ content has the greatest influence on the high-temperature melting temperature of fly ash,Al₂O₃ and Fe₂O₃ have the similar influence on reducing the melting temperature of fly ash,and Cao has the lower influence on reducing the melting temperature of fly ash.The mixture of 30% Si O₂,5% Al₂O₃,10% Fe₂O₃ and 5% Ca O can reduce the melting temperature of fly ash to an ideal state,and the heavy metal content and leaching characteristics of the vitrified products after melting can also meet the national standards.