Key Laboratory of Advanced Civil Engineering Materials Ministry of Education, Tongji University, Shanghai 201804, China.
Key Laboratory of Advanced Civil Engineering Materials Ministry of Education, Tongji University, Shanghai 201804, China.
Waste Manag. 2018 Jul;77:537-544. doi: 10.1016/j.wasman.2018.05.001. Epub 2018 May 7.
The aim of this work was to investigate the migration and transformation of sulfur in the municipal sewage sludge during disposal in cement kiln, and better understand the emission of the sulfur related pollutants in this process. In consideration of the temperature conditions in the practical operation, municipal sewage sludge was pre-dried at 105 °C, and then dried at 210, 260 and 310 °C, co-combusted with cement raw mill at 800, 900 and 1000 °C, and 1350, 1400 and 1450 °C respectively in the laboratory. X-ray photoelectron spectroscopy (XPS) was used to determine the S2p spectral lines of the municipal sewage sludge treated in the different process. Besides, The Thermal Analysis-Thermogravimetry (DTA-TG), Back Scattered Electron (BSE) and Energy Dispersive Spectrometer (EDS) were also employed to explore the mechanism of sulfur subsistence at 1450 °C. The results indicate that sulfide, thiophene, sulfone and sulfate are mainly sulfur compound in the municipal sewage sludge dried at 105 °C. Sulfoxide, a new sulfur compound, appears after it is further dried at 210 °C. The relative contents of sulfide and thiophene are continuously declined as the drying temperature increases due to their evaporation, decomposition and transformation in this process. The transformation of sulfide and thiophene makes the relative contents of sulfoxide and sulfate accordingly increased. However, the relative content of sulfone experiences an elevating-lowering process while the dry temperature elevated from 210 to 310 °C. This case is related to its evaporation and decomposition, as well as its production for the transformation of sulfide and thiophene. In the co-combustion process, sulfide, thiophene and sulfone are entirely vanished for their evaporation, decomposition and transformation. Sulfone is still contained at 800 °C, but when the temperature unceasingly rises, it is completely decomposed or evaporated and sulfate is the only sulfur compound. The microstructures left by the gas release are also observed in the mixtures sintered at 1450 °C, however sulfate still exists even at 1450 °C. The BSE and EDS results show that the melt phase is the important contribution to the appearance of sulfate at the high temperature. These results will sever as a theoretically reference for the pollution control of the sulfur related pollutants in the disposal process of the municipal sewage sludge in cement kiln.
本工作旨在研究城市污水污泥在水泥窑处置过程中的硫迁移和转化，更好地了解该过程中硫相关污染物的排放。考虑到实际操作中的温度条件，将城市污水污泥在 105°C 下预干燥，然后在 210、260 和 310°C 下干燥，分别在实验室中与水泥生料磨在 800、900 和 1000°C 以及 1350、1400 和 1450°C 下共燃烧。X 射线光电子能谱（XPS）用于确定在不同工艺处理的城市污水污泥的 S2p 谱线。此外，还采用热分析-热重法（DTA-TG）、背散射电子（BSE）和能谱仪（EDS）在 1450°C 下探索硫的生存机制。结果表明，在 105°C 干燥的城市污水污泥中，主要的硫化合物为硫化物、噻吩、砜和硫酸盐。在进一步干燥至 210°C 时，出现了新的硫化合物亚砜。由于蒸发、分解和转化，随着干燥温度的升高，硫化物和噻吩的相对含量不断下降。硫化物和噻吩的转化使亚砜和硫酸盐的相对含量相应增加。然而，当干燥温度从 210°C 升高到 310°C 时，砜的相对含量经历了一个升高-降低的过程。这种情况与它的蒸发和分解以及它在硫化物和噻吩转化过程中的产生有关。在共燃烧过程中，由于蒸发、分解和转化，硫化物、噻吩和砜完全消失。亚砜在 800°C 时仍然存在，但随着温度的不断升高，它完全分解或蒸发，硫酸盐是唯一的硫化合物。在 1450°C 烧结的混合物中也观察到气体释放留下的微观结构，但即使在 1450°C 下，硫酸盐仍然存在。BSE 和 EDS 结果表明，熔体相是高温下出现硫酸盐的重要贡献。这些结果将为水泥窑处理城市污水污泥过程中硫相关污染物的污染控制提供理论参考。
