城市污泥流化床焚烧炉飞灰中重金属迁移特性

Heavy Metal Migration Characteristics of Fly Ash in Fluidized Bed Incinerator for Municipal Sewage Sludge

对120 t/d城市污泥循环流化床焚烧炉飞灰中重金属迁移富集特性进行试验研究,对污泥、飞灰及不同温度、取样点的飞灰中Cr、Mn、Ni、Cu、Zn、As、Cd和Pb 8种重金属迁移富集特性进行了分析。试验结果表明:飞灰、底渣及入炉污泥中主要化学成分为Si O_2、Fe_2O_3、Ca O、Al_2O_3和P_2O_5,"Si0_2-Ca O-Al_2O_3-金属氧化物"体系构成了重金属吸附的载体,也为不同形态重金属的吸附提供了活性空间。Cd、As为易挥发性重金属,在炉膛内挥发的Cd、As及其化合物蒸气在503℃和475℃时几乎全部富集于飞灰颗粒;Cr、Mn、Cu、Zn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,为难挥发性重金属。

In order to examine the heavy metals migration and enrichment characteristics,high-temperature fly ash was sampled at the outlet of incinerator and convection heating surface of a 120 t/d fluidized bed incinerator for municipal sewage sludge. The sludge characteristics,fly ash behavior and the migration and enrichment characteristics of Cr,Mn,Ni,Cu,Zn,As,Cd,Pb in fly ash with different temperature at sampling points were studied. Results showed that the main materials of fly ash,bottom ash and sewage sludge are SiO_2,Fe_2O_3,CaO,Al_2O_3 and P_2O_5. 'SiO_2-CaO-Al_2O_3-metal-oxide'is the carrier of heavy metals in fly ash and provides active space for absorption of differ-ent heavy metals. Cd and As are volatile heavy metal. Cd,As and their steam compounds condense in fly ash particles at 503 ℃ and 475 ℃,respectively. Cr,Mn,Cu and Zn are hard to volatilize and enrich in fly ash particles through entrainment at different temperatures in the tail flue.