O2/CO2气氛下污泥/煤混燃中半挥发性重金属的释放特性

Release properties of semi-volatile heavy metals in sewage sludge/coal co-incineration under O2/CO2 atmosphere

    摘要
  • 摘要: 在固定床焚烧实验装置上，采用正交实验法研究了焚烧温度（tc）、污泥掺混比（Xs）、O2体积分数（φO2）、初始含水率（φH2O）、焚烧时间（τ）和含氯量（φCl）六个因素对O2/CO2气氛下污泥/煤混燃中半挥发性重金属（Zn、Pb、Cd、Cu、Ni和Cr）释放特性的影响。结果表明，六种因素对重金属释放率影响程度排序为tc >> Xs > φH2O > φO2 ≈τ > φCl。相同焚烧工况下，Zn释放率最大，Pb和Cd次之，Cu、Ni和Cr较小。提高温度会促进重金属释放，且高温（1000-1100 ℃）对重金属释放的影响显著强于低温（700-900 ℃）。随着温度由700 ℃升高至1100 ℃，Zn和Pb释放率分别由36.1%和12.2%上升至70.9%和63.5%，Cd在900 ℃下达到40.0%的最大释放率，而Cu、Ni和Cr释放率大都维持在20.0%以下，温度对重金属释放率影响程度排序为Pb > Zn > Cd > Cu > Cr > Ni。重金属释放率随着污泥掺混比增加逐渐下降，却随着初始含水率增加呈现波浪式变化趋势，且在30%O2体积分数下重金属释放率取得最小值。焚烧时间和含氯量对Pb释放的影响程度显著强于其他五种重金属。O2/CO2气氛下污泥/煤混燃的最佳工况为：焚烧温度为900-1000 ℃、污泥掺混比为25%左右、O2体积分数为30%、初始含水率小于10%，并尽可能的缩短焚烧时间。

     

    Abstract: The effects of six factors involving incineration temperature (tc), sludge blending ratio (Xs), O2 concentration(φO2), initial moisture content (φH2O), incineration time (τ) and chlorine content (φCl) on the release properties of semi-volatile heavy metals (SVHMs) (such as Zn, Pb, Cd, Cu, Ni and Cr) in co-incineration of sewage sludge and coal under O2/CO2 atmosphere were investigated in a fixed-bed incinerator based on orthogonal experiment. The results indicate that the influence of six factors on the release fraction of SVHMs is ordered as tc >> Xs > φH2O > φO2 ≈ τ > φCl. The release fraction of Zn is the largest, followed by Pb and Cd, and the release fractions of Cu, Ni and Cr are the least at the same co-incineration condition. Increasing temperature is helpful for SVHMs release, and the promotion at high temperatures of 1000-1100 ℃ on SVHMs release is significantly stronger than that at the low temperature of 700-900 ℃. The release fractions of Zn and Pb increase remarkably from 36.1% and 12.2% to 70.9% and 63.5% with increasing tc from 700 to 1100 ℃, respectively, and the release fraction of Cd achieves the maximum of 40.0% at tc=900 ℃, however, the release fractions of Cu, Ni and Cr mostly keep below 20.0%. The influence of incineration temperature on the heavy metal release fraction is ordered as Pb > Zn > Cd > Cu > Cr > Ni. The release fractions of SVHMs decrease with increasing sludge blending ratio, but present a wave-like trend with increasing initial moisture content. The lower release fraction of SVHMs is achieved at φH2O=0 or 40%. O2 concentration has a certain influence on SVHMs release, and the lowest release fraction of SVHMs is achieved at φO2=30%. The influence of incineration time and chlorin content on the release of Pb is significantly stronger than that of other five SVHMs. The suggested optimal conditions of co-incineration of sludge and coal in O2/CO2 atmosphere are: the incineration temperature is 900-1000 ℃, the sludge blending ratio is about 25%, the O2 concentration is 30%, the initial moisture content is less than 10%, and the incineration time is reduced as far as possible.

     

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