Helena Lopes M, Abelha P, Lapa N, Oliveira J S, Cabrita I, Gulyurtlu I
INETI-DEECA, Estrada do Paço do Lumiar, 22, 1649 -038 Lisboa, Portugal.
Waste Manag. 2003;23(9):859-70. doi: 10.1016/S0956-053X(03)00025-4.
Co-combustion tests of dry sewage sludges with coal were performed in a pilot bubbling FBC aiming at the characterization of ashes and determining the behaviour of heavy metals in the process. The tests showed compliance with the regulatory levels as far as heavy metal emissions were concerned. The bottom ashes, which accounted for about 70% of the total ash production, were obtained in a granular form, with diameters ranging from 0.5 to 4 mm. The heavy metals were distributed in ashes obtained from different locations of the installation and their concentrations were found to vary depending on the location of capture. The increase in heavy metals content in bottom ashes was not found to lead to higher leachability and ecotoxicity compared to sewage sludges, suggesting that there could be opportunities for their further use. Mercury suffered vaporisation inside the reactor, thus leaving bottom ashes free of contamination by it. However, there was observed a strong retention of mercury in cyclone ashes due to the presence of unburned carbon which probably acted as an adsorbent. The effluent mercury was also found to be mostly associated with the particulate fraction, being less than 20% emitted in gaseous forms. The results suggested that the combustion of the sewage sludge could successfully be carried out and the amount of unburned carbon leaving the combustor but captured in cyclone was large enough to ensure substantial retention of mercury at low temperatures, hence could contribute to an improvement of the mercury release which still remains an issue of great concern to resolve during combustion of waste materials.
在中试鼓泡流化床中进行了干污水污泥与煤的共燃烧试验，目的是对灰分进行表征并确定该过程中重金属的行为。试验表明，就重金属排放而言，符合监管水平。占总灰分产量约70%的底灰呈颗粒状，直径范围为0.5至4毫米。重金属分布在装置不同位置获得的灰分中，发现其浓度因捕集位置而异。与污水污泥相比，未发现底灰中重金属含量的增加导致更高的浸出性和生态毒性，这表明它们有进一步利用的机会。汞在反应器内发生汽化，因此底灰中没有汞污染。然而，由于存在未燃尽碳，在旋风灰中观察到汞有很强的保留，未燃尽碳可能起到了吸附剂的作用。还发现流出物中的汞大多与颗粒部分相关，以气态形式排放的不到20%。结果表明，污水污泥的燃烧可以成功进行，离开燃烧室但在旋风分离器中捕集的未燃尽碳量足够大，足以确保在低温下大量保留汞，因此有助于改善汞的释放，而汞的释放仍是燃烧废料过程中亟待解决的重大问题。
