水洗预处理对垃圾掺烧污泥焚烧飞灰中重金属高温挥发特性的影响

Effects of water washing on volatile characteristics of heavy metals in fly ash from a MSW and sewage sludge co-combustion plant

对某垃圾掺烧污泥焚烧厂焚烧飞灰进行采样,在研究重金属形态分布的基础上,重点研究飞灰水洗前后重金属(Cu、Zn、Pb、Cd)高温处置过程中的挥发特性。研究结果表明:飞灰中重金属酸可交换态中Cd的比例最大,其次为Zn,而重金属Cr,Ni和Mn主要以残渣态存在。高温处置过程中,飞灰中Pb表现出最易挥发的特性,其挥发率超过80%,而Cu挥发性较小,其挥发率<30%,4种重金属的挥发性从大至小依次为:Pb,Cd,Zn,Cu。水洗飞灰中Zn的挥发率最高,超过20%,而Cu挥发性最小,水洗飞灰中重金属的挥发性从大至小依次为:Zn,Pb,Cd,Cu。在受热时间为120 min、加热温度为900℃条件下,飞灰水洗后Zn,Pb,Cd和Cu的挥发率分别降低了6.87%,70.24%,34.73%和9.52%,其中水洗脱Cl是重金属挥发率降低的主要原因。

Fly ash samples were collected from a MSW and sewage sludge co-combustion plant and the chemical forms of heavy metals were determined. The volatilization of heavy metals Pb, Cd, Cu and Zn was investigated. The effect of using water-washing as a pre-treatment on volatilization of heavy metals was also studied. The results show that the largest proportion of extraction of acid soluble/exchangeable fraction is the element Cd, followed by Zn, while the heavy metals Cr, Ni and Mn mostly remain in the residual fraction. The volatilization of heavy metals is very different in the volatilization rate, following the order of Pb, Cd, Zn, Cu, in which the volatilization rate of Pb is more than 80% and that of Cu is less than 30%. After water washing, the volatilization of heavy metals shows differences in volatilization rate when compared to non-water washing ones, with the volatilization rate following the order of Zn, Pb, Cd, Cu, in which the volatilization rate of Zn is more than 20% and the volatilization rate of Cu is the lowest. After water washing the fly ash, the evaporation of Pb, Cd, Cu and Zn is reduced by 70.24%, 34.73%, 9.52% and 6.87% at a temperature below 900 ℃ with a heating time of 120 min, which contributes to dechlorination through water washing.