Abstract:

In this study, biochars produced from three different particle sizes of sewage sludge (d≤0.15 mm, 0.15 mm <d ≤0.27 mm, and d>0.27 mm) using the fixed bed reactor at a temperature of 500℃. Pyrolysis characteristics of sludge and the heavy metals distributions in sludge and its biochar were investigated, respectively. Moreover, the leaching toxicity of heavy metals in sludge and its biochar were assessed applying toxicity characteristics leaching procedure (TCLP) method. The experimental results showed that with the increase of sludge particle size, the biochar and gas yield obtained from pyrolysis process decreased, while tar yield was an opposite trend. During the pyrolysis process of sludge, the most heavy metals in the sludge were accumulated in biochar except As and their relative enrichment factors were all higher than 90%. The contents of Cu, Zn, and Ni in the sludge increased and decreased for the contents of Cr and Pb with augmenting of particle size. Although the leaching pattern of the heavy metals was different between biochars obtained from the different particle sizes of sewage sludge, the pyrolysis technology significantly suppressed the heavy metals leaching from biochars. The TCLP-leaching rates of most heavy metals except As and Zn from biochar were all lower than 3.0%.

Key words: sewage sludge, pyrolysis, particle size, biochar, heavy metals

摘要：

以3种不同粒径污泥为原料，采用固定床反应器在500℃下制备生物炭。考察了3种不同粒径污泥的热解特性及其生物炭中重金属的分布特征，并运用TCLP对污泥及其生物炭的重金属浸出毒性进行了系统研究。结果表明，随着污泥粒径的增大，热解生成的生物炭和热解气产率均有所降低，而焦油产率则逐渐升高；在3种不同粒径污泥热解过程中，重金属除As外主要富集在固体产物生物炭中，相对富集系数均高于90%。随着污泥粒径的增大，污泥中Cu、Zn和Ni的含量增加，而Cr和Pb的含量则减少；虽然3种不同粒径污泥制备的生物炭中重金属的浸出规律不一致，但是污泥热解可以有效抑制重金属的浸出。生物炭中除As和Zn外其他重金属元素的浸出率均低于3.0%。

关键词: 污泥, 热解, 粒径, 生物炭, 重金属