Corrosion Mechanism Of Refractories During High Temperature Melting Of Municipal Solid Waste Incineration (MSWI) Fly Ash And Recipe Optimization

Municipal solid waste incineration（MSWI）fly ash contains a large amount of toxic and harmful substances such as heavy metals and dioxins.The content of chlorine in the fly ash is high,up to 20 wt%.At the same time,the fly ash contains a large amount of alkaline substances,belonging to hazardous waste.Improper treatment can cause harmful substances to enter groundwater and soil,thereby endangering human health.High temperature melting technology can effectively solidify the heavy metals in fly ash and completely decompose the dioxins in MSWI fly ash,which is one of the effective methods for harmless treatment of fly ash.However,the melting process of fly ash can lead to varying degrees of damage to the refractories lining in the furnace,affecting stable production.At present,there is no detailed research on the erosion mechanism of high chlorine and alkali MSWI fly ash on refractories,Hindering the further development of high-temperature melting processing technology.Therefore,this article focuses on five types of refractories namely corundum and non aluminum oxide,to explore the erosion mechanism of domestic waste incineration fly ash on refractories.At the same time,the research results are applied to melting processes to ensure that the erosion of furnace lining refractories can be reduced while achieving harmless treatment of fly ash and reaching the standard of heavy metal leaching.The specific research results are as follows:（1）According to slag resistance experiments,corundum refractories have poor corrosion resistance,while non aluminum oxide refractories have better corrosion resistance,among which magnesium chromium refractories are the best;At the same time,the erosion of fly ash on refractories is more severe than that of CaO,indicating that other components in fly ash besides CaO can also cause erosion of refractories.（2）Based on the analysis of the erosion mechanism of corundum refractories,it is found that the main reasons for corrosion are:on the one hand,CaO and SiO₂in fly ash react with the main component Al₂O₃of the refractories to generate calcium aluminosilicate,calcium silicate,and other substances;on the other hand,the chlorine element in fly ash reacts with Al₂O₃in the test refractories to generate gaseous substances,resulting in a decrease in aluminum content.（3）Through the analysis of the erosion mechanism of high chromium refractories,it is found that the reason for their better corrosion resistance is that the Al element in high chromium refractories mainly exists in the form of calcium aluminate and less in the form of Al₂O₃.At the same time,through the analysis of the FactSage ternary phase diagram,it can be seen that when the content of chromium oxide is high,the system is stable in the form of Cr₂O₃without reaction,further explaining the reason for the excellent performance of high chromium refractories.（4）Based on the analysis of the erosion mechanism of magnesia chrome refractories,it is found that the low melting substances CaMgSiO₄,Mg₂SiO₄,and MgSiO₃formed by the reaction of SiO₂and MgO in fly ash are the main reasons for refractories erosion.At the same time,for repeatedly calcined magnesia chrome refractories,the key factor causing corrosion is the migration of refractories due to loose structure.The presence of CaO can inhibit the formation of forsterite and magnesium silicate phases,and with the increase in the alkalinity of fly ash,the erosion and penetration of the refractories decreases.（5）Fly ash melting and solidification experiments were conducted on fly ash from five formulations,and it was found that when the fly ash from Formula 1（fly ash is 50%,Al₂O₃is 40%,CaO is 10%,SiO₂is 0%）and Formula 2（fly ash is 50%,Al₂O₃is 35%,CaO is 10%,SiO₂is 5%）were subjected to high-temperature melting treatment,it is the optimal formula that can achieve fly ash solidification,meet heavy metal leaching standards,and reduce erosion of refractory materials.This paper explores the erosion mechanism of high chlorine and alkali content MSWI fly ash on different refractories,providing theoretical support for the selection and application of refractories.At the same time,applying the research results to the melting process ensures that the curing of fly ash and the leaching of heavy metals can be achieved while reducing the erosion of furnace lining refractories,further promoting the development of high-temperature melting technology.