Yu Hongdi, Lin Fawei, Guo Xuan, Luan Chujun, Li Jiantao, Li Rundong, Che Lei, Tian Wangyang, Chen Guanyi
School of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, PR China.
School of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, PR China.
J Hazard Mater. 2024 Dec 5;480:136014. doi: 10.1016/j.jhazmat.2024.136014. Epub 2024 Sep 30.
Thermochemical treatment of oily sludge (OS) has been demonstrated to be an effective approach for resource and energy recovery. However, the migration and emission of potential pollutants have limited its further development. In this study, the environmental impacts, including aromatic compounds in liquid products, N-, S-, and Cl-containing pollutants in gaseous products, and residual organic matter and heavy metals in solid residues, during the pyrolysis, gasification, and combustion processes of OS are comparatively investigated. The results indicate that the aromatics in the liquid products obtained from pyrolysis and gasification are primarily hydrocarbons with 10, 14, and 16 carbon atoms, and the corresponding degree of unsaturation is between 7 and 16. By contrast, the aromatics produced during combustion are mainly hydrocarbons with 10-12 carbon atoms and an unsaturation degree of 7. The liquid products from gasification of OS contain aromatics with more carbon atoms and a higher degree of unsaturation, suggesting potential issues of recalcitrant aromatics and tar by-products during the gasification process. The release behaviors of N-, S-, and Cl-containing pollutants during the thermochemical treatment of OS are closely related to the specific thermochemical technology and treatment temperature. At 550 °C, these pollutants are gradually released from the OS. By contrast, at 950 °C, they are released over a narrow temperature range with significantly higher concentrations. Furthermore, compared with the peak concentrations of SO and HCl during thermochemical processing at 550 °C, these values increase by 1-2 orders of magnitude at 950 °C. With the increase in treatment temperature, the loss on ignition (LOI) of residues from pyrolysis or gasification of OS gradually decreases and stabilizes around 0.5 %. On the other hand, the LOI from combustion fluctuates around 1.0 %. In addition, the removal rates of total organic carbon in the residues from all three thermochemical processes exceed 98.89 %. However, the potential ecological risks associated with heavy metals in the residues from thermochemical treatment of OS also increase to some extent. Cr, Cu, and Zn are found to evaporate and escape into liquid and gaseous products, while Pb is retained in the residues. Notably, the residue from combustion poses the highest environmental risks among the three processes.
油泥（OS）的热化学处理已被证明是一种有效的资源和能源回收方法。然而，潜在污染物的迁移和排放限制了其进一步发展。在本研究中，对OS在热解、气化和燃烧过程中的环境影响进行了比较研究，包括液体产物中的芳香族化合物、气体产物中含N、S和Cl的污染物以及固体残渣中的残留有机物和重金属。结果表明，热解和气化得到的液体产物中的芳香族化合物主要是含10、14和16个碳原子的烃类，相应的不饱和度在7至16之间。相比之下，燃烧过程中产生的芳香族化合物主要是含10 - 12个碳原子且不饱和度为7的烃类。OS气化产生的液体产物含有更多碳原子和更高不饱和度的芳香族化合物，这表明气化过程中存在难降解芳香族化合物和焦油副产物的潜在问题。OS热化学处理过程中含N、S和Cl污染物的释放行为与特定的热化学技术和处理温度密切相关。在550℃时，这些污染物从OS中逐渐释放。相比之下，在950℃时，它们在较窄的温度范围内释放，且浓度显著更高。此外，与550℃热化学处理过程中SO和HCl的峰值浓度相比，950℃时这些值增加了1 - 2个数量级。随着处理温度的升高，OS热解或气化残渣的烧失量（LOI）逐渐降低并稳定在0.5%左右。另一方面，燃烧的LOI在1.0%左右波动。此外，所有三种热化学过程残渣中总有机碳的去除率均超过98.89%。然而，OS热化学处理残渣中重金属相关的潜在生态风险也在一定程度上增加。发现Cr、Cu和Zn蒸发并逸入液体和气态产物中，而Pb保留在残渣中。值得注意的是，燃烧残渣在这三个过程中带来的环境风险最高。
