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Pyrolysis of arsenic-bearing gypsum sludge being substituted for calcium flux in smelting process
Journal of Analytical and Applied Pyrolysis ( IF 6 ) Pub Date : 2018-03-01 , DOI: 10.1016/j.jaap.2018.02.002 Xun Li , Xing Zhu , Xianjin Qi , Kongzhai Li , Yonggang Wei , Hua Wang , Jianhang Hu , Xinghuan Hui , Xin Zhang
Journal of Analytical and Applied Pyrolysis ( IF 6 ) Pub Date : 2018-03-01 , DOI: 10.1016/j.jaap.2018.02.002 Xun Li , Xing Zhu , Xianjin Qi , Kongzhai Li , Yonggang Wei , Hua Wang , Jianhang Hu , Xinghuan Hui , Xin Zhang
Abstract Arsenic-bearing gypsum (ABG) sludge, one of the biggest hazardous waste in the nonferrous metals industry, greatly threatens the ecological safety due to possible leakage and diffusion risks. However, the state-of-the-art techniques suffer great challenges for the disposal of ABG sludge due to its properties including worthless constituents, high arsenic leaching toxicity, and tremendous output. In this work, the pyrolysis of ABG sludge is studied aiming to propose a flexible and facile co-disposal method by using ABG sludge as calcium flux instead of limestone in smelting processes. The pyrolysis behavior and arsenic migration are investigated in the TG-FTIR and the fixed-bed reactor by means of XRD, chemical analysis, and Chinese standard leaching tests. The sludge can be converted into environmentally friendly residue via the both direct and reductive pyrolysises at the temperatures ≥800 °C due to the release of leachable arsenic in the form arsenic-bearing dust. The direct pyrolysis is favorable for the sulphur releasing through the transformation of CaSO4 → CaO/SO2. While this transformation is depressed in the anthracite-driven reductive pyrolysis because of the reducing agent and being largely replaced by the CaSO4/C → CaS/CO2 pathway. In addition, the arsenic releasing is significantly promoted in this reducing environment by the further reduction of arsenates. The proposed co-disposal model of ABG sludge being substituted for calcium flux in ISASMELT copper smelting process renders the good compatibility and flexibility.
更新日期：2018-03-01
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