Zhang Zhenrong, Huang Yaji, Zhu Zhicheng, Yu Mengzhu, Gu Liqun, Wang Xinyu, Liu Yang, Wang Ruyi
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China; Huaneng Hunan Corporation, Changsha, Hunan, 410000, China.
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu, 210096, China.
Environ Pollut. 2022 Nov 1;312:120024. doi: 10.1016/j.envpol.2022.120024. Epub 2022 Aug 24.
Serious pollution is caused by heavy metals (HMs) emission during sludge combustion treatment, but the addition of minerals has the ability to alleviate the migration of HMs to the gaseous state. In this study, HMs (As, Cr, Zn and Cu) behavior, speciation, and environmental risk during sludge combustion with CaO and montmorillonite (MMT) additive was investigated in the lab-scale tube furnace. The results showed that the sludge combustion was mainly determined by volatile matter. In general, CaO inhibited the volatilization of Cr, Zn, and Cu, but promoted As volatilization. MMT inhibited the volatilization of HMs, but the effect was not obvious at high temperatures. Besides, the improvement of retention effect was not found for Cr and Cu with the increase of CaO at 1000 °C, there might exist threshold value for CaO on HMs retention process. Meanwhile, CaO increased acid-soluble fraction of As significantly at high temperatures, decreased residual fraction of Cr by oxidation, converted Zn and Cu to residual fraction. MMT increased the acid-soluble fraction of As and residual fraction of Cr. In view of the HMs environmental risk in ash, the combustion temperature of sludge was necessary to control under 1000 °C and minerals additive amount was needed to manage above 1000 °C.
污泥燃烧处理过程中重金属（HMs）排放会造成严重污染，但添加矿物质能够缓解HMs向气态的迁移。本研究在实验室规模的管式炉中，研究了添加CaO和蒙脱石（MMT）时污泥燃烧过程中HMs（As、Cr、Zn和Cu）的行为、形态及环境风险。结果表明，污泥燃烧主要由挥发物决定。总体而言，CaO抑制了Cr、Zn和Cu的挥发，但促进了As的挥发。MMT抑制了HMs的挥发，但在高温下效果不明显。此外，在1000℃时，随着CaO含量增加，未发现对Cr和Cu的保留效果有所改善，CaO在HMs保留过程中可能存在阈值。同时，CaO在高温下显著增加了As的酸溶态比例，通过氧化降低了Cr的残渣态比例，将Zn和Cu转化为残渣态。MMT增加了As的酸溶态比例和Cr的残渣态比例。鉴于灰中HMs的环境风险，污泥燃烧温度需控制在1000℃以下，在1000℃以上则需要控制矿物质添加量。
