固体添加剂对污泥焚烧过程中重金属迁移行为的影响

Effects of Adsorbents on Partitioning and Fixation of Heavy Metals in the Incineration Process of Sewage Sludge

利用高温固定管式炉研究了4种固体添加剂(CaO、Al2O3、粉煤灰和高岭土)对污泥焚烧过程中6种重金属(Pb、Cd、Cu、Cr、Ni、Zn)在底渣中的迁移行为与固化残留特征的影响.结果表明,污泥焚烧过程中4种固体添加剂(CaO、Al2O3、粉煤灰和高岭土)的加入有利于重金属固定并且残留在焚烧底渣中,并且随着固体添加剂添加比例的增多,重金属的残留率也逐渐增加.焚烧温度对固体添加剂吸附重金属的效果有很大影响,其中重金属自身熔点、沸点及重金属在污泥中的赋存形态是决定其挥发性的一个重要因素.不同固体添加剂对不同重金属迁移的抑制效果有很大差异,从控制重金属挥发角度来看,固体添加剂高岭土和CaO要优于其他固体添加剂.固体添加剂活性中心与重金属化合物分子的相互作用取决于这些活性位的分布及重金属的化学性质.

Experiments were carried out on laboratory-scale electrically heated tube furnace sewage sludge combustion with different adsorbents. Four solid adsorbents （calcium oxide, Alumina, fly ash and kaolin） were used to control the emission of heavy metals （Pb, Cd, Cu, Cr, Ni, Zn） during the sewage sludge incineration. The results showed that the heavy metals tended to be fixed and left over in the incineration bottom ash with the addition of calcium oxide, Alumina, fly ash and kaolin. With the increase of the solid adsorbent ratio, the residual rate of heavy metals in the bottom ash also increased. Incineration temperature had a great influence on the heavy metal adsorption effect of the solid adsorbent. The forms, melting point and boiling point of the heavy metals were found to be important factors that determined its volatility. There was huge difference in the inhibitory effect of different adsorbents on heavy metals migration. From the view of controlling heavy metal evaporation, the adsorbents kaolin and CaO were superior to the other adsorbents. The interaction between the active center of the solid adsorbent and the molecules of the heavy metal compounds depended on the distribution of these active sites and the chemical properties of the heavy metals.