不同粒径垃圾焚烧飞灰重金属分布和浸出性质

对烟气净化系统飞灰(以下简称飞灰)按粒径进行分级,研究了飞灰重金属含量、形态分布和浸出毒性随粒径的变化,讨论了不同粒径的飞灰对重金属总量和浸出总量的贡献率.结果表明:飞灰中粒径>154 μm和<30 μm的颗粒较少,粒径为38.5～74 μm的颗粒约占总量的50%.除Ni和Cr外,重金属含量随飞灰粒径的减小呈增加趋势,且主要表现在酸溶态Cd,Zn,Pb,Cu和有机结合态Pb以及晶形氧化铁态Pb,Zn含量的增加.随着飞灰粒径的减小,Cr,Ni,Zn,Hg和Pb的浸出量也呈逐渐增加趋势,其中Zn,Hg和Pb的表现尤为突出.尽管细颗粒上的重金属对飞灰的重金属总量贡献不大,但高浸出率使细颗粒飞灰对重金属浸出总量仍具有较大贡献,尤其是Pb,Zn和Hg,在占飞灰质量8%的粒径<30 μm的飞灰中,富集了约40%的水溶性Pb,Zn和Hg. 

Heavy Metals Distribution and Leaching Characteristics in MSWI APC Residues with Various Particle Sizes

The air pollution control (APC) residues from municipal solid waste incinerator(MSWI) were classified by sizes; the heavy metals contents, speciation and their water-leaching toxicity in the size-classified fractions were analyzed; and the contribution of heavy metals content and leachable amount in various fractions to the raw APC residues was discussed. It is concluded that fractions of >154 μm and <30 μm were minor parts in the APC residues, while particles of 38.5～74 μm accounted for about 50%. Concentration of heavy metals, except Ni and Cr, were greater in fine particles, and acid soluble Cd, Zn, Pb and Cu, organically bound Pb, as well as crystalline iron oxide occluded Pb and Zn took up most of the increase. The leaching of Cr, Ni, Zn, Hg and Pb increased with decrease of particle size, especially for Zn, Hg and Pb. But the enrichment of heavy metals in fine particles was not much in evidence. The much higher heavy metals leaching ratios of fine particles made this section a bigger contributor to heavy metals leaching from raw APC residues. Especially for Pb, Zn and Hg, about 40% of their leachable sections were enriched in the fraction of <30 μm, which accounted for only about 8% of the APC residues.