Pollutant Emission Behavior And Control Technology In The Process Of Sintering Collaborative Treatment Of Water-washed Fly Ash

Municipal solid waste incineration fly ash（HW18）contains a large number of toxic and harmful components such as heavy metals and dioxins,which brings great hidden dangers to human health and environmental safety.Its harmless treatment is of great significance to prevent and control environmental pollution and improve the quality of ecological environment.In this thesis,the raw municipal solid waste incineration fly ash（MSWI fly ash）pretreated by water washing was taken as the research object.Based on the systematic study of the basic physicochemical characteristics of raw MSWI fly ash and water-washed fly ash,this paper studied the law and mechanism of the effect of adding raw MSWI fly ash and water-washed fly ash on sintering;The emission behavior of heavy metals,dioxins and other pollutants in the process of sintering co-treatment of MSWI fly ash was found out;On this basis,the dioxins emission control technology in sintering process was developed.The main conclusions were as follows:（1）The influence law of water-washed fly ash on sintering was revealed:compared with the addition of raw MSWI fly ash,when adding water-washed fly ash,the tumbler index increased;the productivity and sintering speed change little,but the yield decreases.With the increase of the addition proportion of water-washed fly ash,the productivity of sinter,tumbler index and yield showed a downward trend,the change of sintering speed was not obvious,and the appropriate addition proportion was no more than 1.0%.The reason was that the metallogenic reaction ability of high calcium fly ash was weaker than that of calcium containing flux.Increasing its addition ratio was not conducive to the formation of calcium ferrite binder phase.Under suitable conditions,the reduction pulverization indexes and reduction degree of sinter increased,the softening range widened and the droplet range narrowed.（2）The emission behavior of pollutants in the process of sintering co-treatment of water-washed fly ash was found out:compared with the addition of raw MSWI fly ash,the content of heavy metals in sinter increased and the removal rate decreased when water-washed fly ash was added;The concentration of dioxins in sintering flue gas and sinter decreased by 76%and 12%respectively,and the concentration of PCDDs decreased mainly;With the increase of the proportion of water-washed fly ash,the content of heavy metals in sinter showed an increasing trend,especially Pb and Zn elements.The concentration of dioxins in sintering flue gas and sinter increased.Under the condition of appropriate addition proportion,the concentration of dioxins in flue gas was still higher than the benchmark.（3）The dioxins emission control technology in the process of sintering co-treatment of water-washed fly ash was developed:after molding pretreatment of water-washed fly ash,dioxins in flue gas decreased from 1.44 ng I-TEQ·Nm^-3 to 1.04 ng I-TEQ·Nm^-3.The reason was that molding pretreatment reduced the dispersion of water-washed fly ash particles in sintering materials,which can effectively reduce the contact between chlorine and carbon and catalyst and inhibit the occurrence of de novo reaction;On this basis,by coating calcium containing additives on the surface of water-washed fly ash pellets,adsorbing and fixing HCl and Cl₂,deacon reaction and chlorination reaction were inhibited,and the concentration of dioxins was further reduced to 0.62 ng I-TEQ·Nm^-3,which was lower than the sintering standard(0.69 ng I-TEQ·Nm^-3).