Study On High Temperature Melting,Fluidity And Control Methods Of Fly Ash From Domestic Waste Power Plants

With the accelerated development of urbanization in China,the urban population is rapidly increasing,and the production of household waste is huge and still growing.Practice has proven that incineration power generation is a good method for harmless treatment of household waste,and it is rapidly developing nationwide.The fly ash generated during the process of waste incineration for power generation,which contains a large amount of dioxins and heavy metals,is a toxic and harmful substance and has not yet been properly disposed of.Plasma melting technology can decompose dioxins in municipal solid waste incineration（MSWI）fly ash and solidify heavy metals to achieve harmless treatment effects.It has been proven to be a reliable and safe method,but its high cost hinders the promotion and application of this technology.This article studies the method of reducing the melting temperature of fly ash to reduce the cost of plasma melting.This article uses MSWI fly ash from a power plant in Beijing as raw material to study the effects of water leaching,ammonium chloride solution leaching,and hydrochloric acid solution leaching on the chemical composition and melting temperature of MSWI fly ash.The mineral transformation process and mechanism of MSWI fly ash at high temperatures are simulated using FactSage software.The results showed that water leaching can remove soluble salts and Ca（OH）₂ from fly ash,while ammonium leaching can remove soluble salts and Ca（OH）₂ from fly ash.Acid leaching can remove soluble salts,Ca（OH）₂,and CaCO₃ from fly ash.The melting temperature of the acid leached ash obtained by acid leaching is the lowest,within the temperature range of 1200-1250℃.Mechanism research has found that the above phenomenon is mainly the result of changes in CaO content in fly ash,and a decrease in CaO content in fly ash leads to a decrease in melting temperature.This article further studies the factors affecting the high-temperature fluidity of fly ash,as plasma melting liquid slag removal not only requires low melting point of fly ash,but also good fluidity.The high-temperature fluidity of fly ash pretreated with three solvents was studied using FactSage.The results showed that although the melting temperature of acid leached ash was low,the range of slag discharge temperature was narrow and the operability was poor.The fluidity of ash samples obtained by mixing different contents of quartz sand,limestone and power plant slag into acid leaching ash was further studied.It was found that the addition of quartz sand and slag can improve the slag discharge temperature range of acid cleaning ash samples and meet the operation requirements.Mechanism research has found that the viscosity of high-temperature melting is mainly affected by its chemical composition.The higher the content of SiO₂ and Al₂O₃,the higher the viscosity;The higher the CaO and other oxides,the lower the viscosity of the ash sample.