污泥与煤、木屑燃烧过程中重金属排放特性研究

Volatility of heavy metals in co-combustion of sludge with coal and wood

为了考察燃料燃烧过程中重金属的迁移转化规律,对污泥、煤与木屑及其混合物在不同温度下氧气中燃烧灰渣中的重金属元素进行分析。结果表明,燃料中重金属在高温燃烧时表现出不同的挥发特性,大部分元素随着温度的升高挥发率增加,其中Cd、Pb和Zn元素挥发性较强,Cr、Cu和Ni挥发性较弱。污泥与木屑混合燃烧灰渣仍以污泥灰为主,重金属含量与污泥灰相近,污泥中混入煤后使灰中大部分重金属含量有所降低。燃烧过程会改变重金属存在形态,污泥与煤原料中以酸溶态和可还原态存在的重金属含量较高,具有较强的生物有效性和迁移性,而燃烧灰渣中酸溶态和可还原态含量显著下降,混合燃烧灰渣中除As外的其他重金属几乎全部以残渣态存在,其含量达到90%以上,焚烧过程有效降低了燃料灰渣中重金属的生物毒性。

In order to understand the volatility of heavy metals in the combustion of fuels, the combustion tests of sludge, coal , wood and the blends in oxygen under different temperature were performed. The results show that the heavy metal elements exhibited different volatile properties at high temperatures. Cd, Pb and Zn were volatile while Cr, Cu and Ni were more enriched in residues. The volatility of most heavy metals in sludge and coal increased with increasing temperature. The contents of heavy metals in ash of sludge/wood blends were similar to that in sole sludge ash. The heavy metals contents in ash decreased when sludge mixed with coal. Combustion process can change the speciation distribution of heavy metals in fuels. With the exception of As, other heavy metals were almost existed in the residue form （ 〉 90% ） whose latent migratory characteristics and phytotoxieity were low.