污泥与煤泥混烧对重金属固留特性的影响

Effect of sewage sludge mixed with coal slime on heavy metal retention characteristics

针对污泥与煤泥混烧时重金属(Pb、As、Cu、Cr、Cd)的迁移特性以及在混烧条件下矿物质对重金属固留效果的影响,利用电热管式炉并结合电感耦合等离子体质谱(ICP-MS)、X射线衍射(XRD)等表征分析手段,研究不同燃烧条件下污泥与煤泥单独燃烧及多比例混烧过程。结果表明:污泥单独燃烧时,As的挥发率随温度升高而上升,Pb、Cu、Cd、Cr的挥发率在700℃时达到顶峰,在700~900℃时随着温度升高而下降。对于煤泥,Pb、Cr的挥发率随温度升高逐渐上升,Cu的挥发率随温度升高呈现先下降后上升的趋势,700℃时达到最低点,Cd的挥发率则相反。对于污泥-煤泥耦合燃烧过程,污泥-煤泥在5∶5掺混比条件下重金属固留率相比于2∶8及8∶2掺混比条件有所提升,5∶5掺混比条件下900℃燃烧温度时污泥-煤泥中矿物质交互作用对Pb、As、Cu、Cr和Cd实际残留率相比理论值分别提高了148.9%、5.8%、28.6%、112%和75.7%。混烧过程中重金属的固留主要受到矿物组分之间所发生的交互作用的影响。其中,对于单组分燃烧条件,SiO2、Al2O3、Fe2O3易与重金属反应生成难挥发化合物并在灰渣中赋存;而混烧过程可以促进硅铝酸盐及含铁化合物的分解,进而在大量生成SiO2等化合物的基础上,促进重金属残留率的提升。

To investigate the migration characteristics of heavy metals(Pb,As,Cu,Cr,Cd)and the influence of minerals on the heavy metal retention effect in the mixed combustion conditions,the combustion of sludge and coal slime alone and the co-combustion in multiple proportions were studied under different combustion conditions using an electric tube furnace and by means of ICP and XRD characterization analysis.The results showed that when sludge was burned alone,the volatilization rate of As increased with the increase of temperature,and the volatilization rates of Pb,Cu,Cd and Cr peaked at 700℃and decreased with the increase of temperature at 700—900℃.For the combustion of coal slime,the volatilization rates of Pb and Cr gradually increased with the increase of temperature,the volatilization rate of Cu showed a trend of decreasing and then increasing with the increase of temperature and reached the lowest point at 700℃,while the volatilization rate of Cd was the opposite.For the coupled sludge-coal slurry combustion process,the retention rate of heavy metals in sludge-coal slurry at 5∶5 blending ratio was higher than that at 2∶8 and 8∶2 blending ratios,and the actual residual rates of Pb,As,Cu,Cr and Cd from mineral interactions in sludge-coal slurry at 900℃combustion temperature at 5∶5 blending ratio increased by 148.9%,5.8%,28.6%,112%and 75.7%,respectively,compared with the theoretical values.The retention of heavy metals in the mixed firing process was mainly influenced by the interaction between mineral components,in which,for single-component combustion conditions,SiO2,Al2O3,and Fe2O3 were prone to react with heavy metals to form compounds that were difficult to volatilize and fused in the ash,while the mixed firing process could promote the decomposition of silica-aluminate and ironcontaining compounds to form SiO2 and other compounds in large quantities,which enhanced the heavy metal residual rate.