(2010) Experimental research on microwave induced thermal decomposition of printed circuit board wastes

Zhang Z., Zhao X., Kwon E., Calstaldi M.J.

(American Society of Mechanical Engineers) 18th Annual North American Waste-to-Energy Conference, NAWTEC18 DOI: 10.1115/nawtec18-3536

As a result of electronic industry development in China, significant amount of Printed Circuit Board (PCBs) wastes are generated. The thermal decomposition via combustion or pyrolysis/gasification is considered to be a feasible disposal way for PCBs. To understand the consequences of pyrolysis, gasification or combustion in WTE facilities, thermogravimetric analysis (TGA) has been carried to characterize the thermal decomposition mechanisms and extract the kinetic parameters in various atmospheres (N₂, CO₂ and air) to simulate different regions in WTE applications. TGA tests in N₂ atmosphere showed there was only one significant reaction in the low temperature range of 270~350°C, which was the decomposition of epoxy resin in PCBs. The behavior in CO₂ atmosphere was similar with that in N₂. However, the PCBs oxidation process in air atmosphere showed two thermal decomposition steps. One was the thermal decomposition similar to the volatilization in N₂ atmosphere and the second step showed oxidation behavior. Some pre-processing was investigated to explore possible benefits in WTE combustion. PCBs waste was pyrolyzed using a microwave tubular furnace. The liquid product were collected and then identified by means of gas chromatography-mass spectrometry (GC-MS). Most of the Br contained in PCBs was released into non-condensable gas in the form of HBr. The liquid product contained a large amount of phenolic compounds, bisphenol A and other aromatic compounds that can be used to produce related chemical products or used in WTE facilities. The experimental results including the thermal kinetic parameters and microwave induced pyrolysis indicate the complex mechanisms that take place during the pyrolysis of PCBs wastes. © 2010 by ASME.