Combustion and inorganic bromine emission of waste printed circuit boards in a high temperature furnace |
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Authors: | Ni Mingjiang Xiao Hanxi Chi Yong Yan Jianhua Buekens Alfons Jin Yuqi Lu Shengyong |
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Affiliation: | a State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, PR China b Chemistry & Chemical Engineering School, Hunan University of Science & Technology, Xiangtan, PR China |
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Abstract: | High temperature combustion experiments of waste printed circuit boards (PCBs) were conducted using a lab-scale system featuring a continuously-fed drop tube furnace. Combustion efficiency and the occurrence of inorganic bromine (HBr and Br2) were systematically studied by monitoring the main combustion products continuously. The influence of furnace temperature (T) was studied from 800 to 1400 °C, the excess air factor (EAF) was varied from 1.2 to 1.9 and the residence time in the high temperature zone (RTHT) was set at 0.25, 0.5, or 0.75 s.Combustion efficiency depends on temperature, EAF and RTHT; temperature has the most significant effect. Conversion of organic bromine from flame retardants into HBr and Br2 depends on temperature and EAF. Temperature has crucial influence over the ratio of HBr to Br2, whereas oxygen partial pressure plays a minor role. The two forms of inorganic bromine seem substantially to reach thermodynamic equilibrium within 0.25 s. High temperature is required to improve the combustion performance: at 1200 °C or higher, an EAF of 1.3 or more, and a RTHT exceeding 0.75 s, combustion is quite complete, the CO concentration in flue gas and remained carbon in ash are sufficiently low, and organobrominated compounds are successfully decomposed (more than 99.9%).According to these results, incineration of waste PCBs without preliminary separation and without additives would perform very well under certain conditions; the potential precursors for brominated dioxins formation could be destroyed efficiently. Increasing temperature could decrease the volume percentage ratio of Br2/HBr in flue gas greatly. |
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Keywords: | Waste printed circuit boards Combustion Inorganic bromine Emission |
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