Mechanism Of The Interaction Between Fine Particles And Heavy Metals In Sewage Sludge Incineration Flue Gas

As the by-product of sewage sludge incineration treatment,fly ash has the value of resource utilization.Meanwhile,with the presence of heavy metals in fly ash,it need to be safely disposal before utilization.Furthermore,fly ash is usually considered uniform size particles,but actually particle size distribution of fly ash is very wide.If we can get different particle size fly ash as our research object and clear the complex relationship of different particle size of fly ash and heavy metals and it will be a big push on the fly ash resource utilization process.This paper focuses on the physical and chemical proper ties of different particle size fly ash.A new integrated evaluation method of heavy metals used in this paper to have a risk assessment of different size particle.Based on the classification of fly ash by using high precision air classifier,fly ash digestion method and BCR four step sequential extraction were used in this paper.As a part of the integrated risk assessment method,two leaching method TC LP and HJ557-2009 were introduced in chapter 4.Combined with XRD and XRF,we analyzed the relationship between the main components of fly ash and the content of heavy metals in different particle size.Clear the mechanism of the formation of fly ash and heavy metals.The experimental results demonstrated that particles less than 1?m are the result of the agglomeration of smaller particles.O verall,with the increase of particle size,the heavy meta l content decreased,but there is a trend of growth in the last section.One reason was coarse particles were mainly unburned mineral particles;the heavy metal content was high.The other reason was the relatively high basic oxide content in particles more than 50?m and heavy metals are easily adsorbed with basic oxide.The presence of silicate in particles less than 1?m was found to be a sign of melting,which was the result of the reaction between SiO2 and other oxides at high temperature.The residual fraction in the different particle size segments were dominant,and the proportion of the acid soluble fraction became smaller and the residue increased with increasing particle size.According to the integrated assessment method,the toxicity of fly ash of less than 10 ?m is larger.Though the study,we can figure out the mechanism of different size particles and the heavy metal,providing support for the reasonable and safe disposal of fly ash and the utilization of resources.