Thermogravimetric analysis and kinetic study on large particles of printed circuit board wastes

Abstract

Pyrolysis of large printed circuit board (PCB) waste particle was conducted on a specially designed laboratory-scale thermobalance (Macro-TG) with sample loading of 30 g under dynamic nitrogen atmosphere. The effects of heating rate (10, 15, 20 and 25 degrees C min(-1)) and particle size (1 mm x 1 mm, 5 mm x 5 mm, 10 mm x 10 mm and 10 mm x 20 mm) were examined. To compare the different decomposition behavior of fine and large one, the thermal decomposition of PCB waste powder (approximately 5mg) was also performed on a thermogravimetric analyzer (common TG) under various heating rates (10, 15, 20 and 40 degrees C min(-1)) and particle size ranges (0.198-0.165 mm, 0.165-0.074 mm, 0.074-0.055 mm and 0.055-0.047mm). Experimental results show that large particle has a pyrolysis reaction retardancy compared to fine one. The distributed activation energy model was used to study the pyrolysis kinetics. It was found that during pyrolysis process, values of frequency factor (k(0)) changed with different activation energy (E) values. On common TG, the E values range from 156.95 to 319.37 kJ mol(-1) and k(0) values range from 2.67 x 10(13) to 2.24 x 10(27)s(-1). While, on Macro-TG, the range of E was 31.48-41.26 kJ mol(-1) and of the frequency factor was 19.80-202.67s(-1).