Keywords and Phrases
Printed Wire Boards (PWBs); Combustion; Pyrolysis; Green Recycling
The availability of cheaper and better electronic products as a result of the rapid innovation in technology in past decades has driven the production of e-waste forward. Printed wiring board (PWB) is a component made of one or more layers of insulating material with electrical conductors. The existing processes of recycling PWBs use pyrometallurgical or hydrometallurgical methods, which generate atmospheric pollution. Green recycling has obvious benefits to decrease the amount of PWBs. Green recycling includes two features, 1) little or zero pollution of toxic gases and heavy metals, and 2) efficient (quick and economical) recycling.
The aim of this work is to investigate green thermal treatment of PWB wastes in laboratory scales. For small scale experiments, PWB powders were combusted and pyrolyzed using TG/DTA, and the emitted gases were measured using MS. The suitable combustion conditions: 15 °C/min heating rate, >125 ml/min gas flow rate, above 600 °C top temperature, and the holding time is not important for combustion process; The suitable pyrolysis conditions: 15-20 °C/min, >100 ml/min gas flow rate, above 900 °C top temperature, and longer holding time. In combustion experiments, CaCO₃, NaOH, NaHCO₃ and Na₂CO₃ were mixed with PWB powders with a mass ratio of 1:1 to control toxic gas emission like HBr. In pyrolysis experiments, additives such as CaCO₃, CaO, Fe₂O₃, ZSM-5, Y-Zeolite were mixed with PWB powders with mass ratio of 5:1 to control toxic gas emission and enhance the pyrolysis reaction. CaCO₃ was the best additive to efficiently control toxic emitted gas during the combustion process, and Fe₂O₃ was the best choice to control toxic emitted gas and enhance the reaction speed during pyrolysis experiment. For large scale experiments, PWB samples were pyrolyzed to solid, liquid and gas products in a tube furnace. Liquid products were analyzed by FTIR. For pyrolysis of PWB without additives, averagely there were 47% solid products, 20% liquid products and 33% gas products. The yield (47%) of solid products in the tube furnace was far more than the yield (36%) in TG/DTA experiments. The results also showed that pyrolyzing smaller PWB powders produced more solid products--Abstract, pages iii-iv.
Zhang, Lifeng (College teacher)
Schuman, Thomas P.
Schlesinger, Mark E.
Materials Science and Engineering
M.S. in Materials Science and Engineering
National Science Foundation (U.S.)
Missouri University of Science and Technology. Materials Research Center
Missouri University of Science and Technology. Intelligent Systems Center
Missouri University of Science and Technology
xii, 92 pages
© 2010 Xiangjun Zuo, All rights reserved.
Thesis - Open Access
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Link to Catalog Recordhttp://laurel.lso.missouri.edu/record=b10717947~S5
Zuo, Xiangjun, "Experimental study on thermal treatment of used printed wiring boards (PWBS)" (2010). Masters Theses. 7358.