温度对污泥流化床焚烧飞灰重金属迁移的影响
Effect of temperature on migration of heavy metals in fly ash in a fluidized bed incinerator for sewage sludge

通过在城市污泥流化床焚烧炉炉膛出口及对流受热面处进行高温飞灰在线取样,以及对布袋除尘器飞灰在水平管式炉上进行不同温度下的煅烧试验,研究温度对焚烧飞灰中Cr,Mn,Ni,Cu,Zn,As,Cd和Pb 8种重金属迁移富集特性的影响.试验结果表明,飞灰的主要化学成分为SiO2,Fe2O3,CaO,Al2O3和P2O5.在流化床焚烧温度范围内,Mn,Cu,Cr,Ni和Zn没有经历挥发-冷凝,主要通过夹带富集于飞灰颗粒,它们在尾部烟道不同温度区域飞灰颗粒上的富集程度相当;在炉膛内挥发的Cd,As及其化合物在500~700 ℃和500~800 ℃之间大量富集于飞灰颗粒.Pb在焚烧炉内因生成氧化铅和铅酸盐等比较稳定的化合物而少量挥发.Zn的化合物与飞灰基体中的化合物发生反应,生成硅酸锌和铝酸锌等稳定的化合物,在一定程度上阻止Zn的挥发.
In order to examine the effect of temperature on migration and enrichment characteristics of heavy metals, including Cr, Mn, Ni, Cu, Zn, As, Cd, Pb, high-temperature fly ash sampling was carried out at the outlet of incinerator and convection heating surface of a fluidized bed incinerator for municipal sewage sludge. And the calcination of the bag filter ash was conducted in a horizontal tube furnace at different temperatures. Experimental results show that the main components of fly ash are SiO2, Fe2O3, CaO, Al2O3 and P2O5. In the temperature range of the fluidized bed incinerator, Mn, Cu, Cr, Ni and Zn do not experience the process of volatilization and condensation, and enrichments of these five heavy metals are approximately the same at different temperature ranges. Volatilized Cd, As and their compounds in the furnace are enriched in fly ash particles in 500 to 700 ℃ and 500 to 800 ℃. A small part of Pb volatilize in the incinerator since Pb mainly form stable substances such as lead oxide and plumbite. During the incineration of municipal sewage sludge, Zinc compounds react with compounds in the matrix of fly ash and form stable compounds such as zinc silicate and zinc aluminate, which prevent the volatilization of Zn to a certain degree