Co-pyrolysis of paper-laminated phenolic printed circuit boards and calcium-based additives in fixed and fluidized bed reactors

This study compares the impact of the calcium-based additives and the pyrolyzer on the recovery and the halide content of the oil produced from the pyrolysis of paper-laminated phenolic resin printed circuit boards (FR2-PCB). The preliminary experiments showed that the maximum liquid recovery (40.6%) was achieved in a fluidized bed pyrolyzer containing a 50:50 mixture of CaO and Ca(OH)₂ operating at T = 620 °C and PCB-to-additive ratio (FR2/A) = 5.4 g/g for 22 min. Extra tests were then carried out under these conditions in fixed and fluidized bed pyrolyzers to separately explore the impact of CaO, Ca(OH)₂, and CaO + Ca(OH)₂ on the liquid recovery (L_R) and the halogen content of the non-solid products. In the fluidized bed, L_R in the presence of CaO, Ca(OH)₂, and CaO + Ca(OH)₂ was 34.5%, 41.2%, and 38.9 wt%, respectively. The fraction of phenolic compounds in the pyrolysis oil ranged from 86% to 93%, about 1-3% higher than the corresponding values in the fixed bed. Using additives led to lower halide content in the pyrolysis oil of the fluidized bed than that of the fixed bed. However, the opposite trend was observed in the absence of additives. Regardless of the type of pyrolyzer, Ca(OH)₂ was more successful than CaO in increasing L_R, whereas CaO was more effective than Ca(OH)₂ in pyrolysis oil dechlorination. Co-pyrolysis of FR2-PCB and CaO + Ca(OH)₂ in a fluidized bed reactor was identified as a practical approach to enhance the recovery of pyrolysis oil comprising only 5% of the original halogen content of the feedstock.