Controlled Pyrolysis Of Waste Printed Circuit Boards Assisted By Microwave

With the rapid development of information technology,the upgrading of electronic products is continuously accelerated,which results in a large number of e-waste.As a typical e-waste,the number of waste printed circuit boards(PCBs) is also increasing rapidly.How to dispose and recycle this kind of waste properly is a growing challenge to researchers all over the world.In this thesis,a microwave pyrolysis process for disposal and recycling of PCBs has been proposed.The feasibility of control final pyrolysis temperature by mixing with different microwave absorbing materials is discussed.A material used for controlling microwave pyrolysis temperature was designed,which was used in the experiments of microwave assisted pyrolysis of wasted printed circuit boards,in an attempt to recover high melting point metal balls and low melting point metal balls separately.The effects of pyrolysis conditions including microwave power,microwave heating time and particle size were investigated.Based on that, the technology conditions of Microwave assisted controlled-pyrolysis of waste PCBs was determined.Simultaneity,GC,FT-IR,XRF,EPMA and GC/MS etc.were used to characterise the pyrolysis products.The results showed that microwave heating temperature was able to be controlled successfully by adding microwave-inert materials in strong microwave absorbing material (SIC).The mass ratio changed with the microwave-inert materals added in SiC when it was controlled to the same final temperature.And the pyrolysis temperature was still able to be contolled at 700-800℃with the same temperature-controlled tube when the type of PCBs was different.The pyrolysis products of waste PCBs were composed of gas,liquid and solid residues.And the yields of pyrolysis products were different between the two type of PCBs.The produce from Singe-side CCL pyrolysis were approximately 10%-16%(mass ratio) of gas,37%-43%of oily liquid,43%-48%of solid.And the pyrolysis products of Multi-layer CCL were composed of 8-13%of gas,10-14%of liquids and 76-79%of solid residues.The gas products were both rich in CO,CO₂,H₂ and hydrocarbon of C₁-C₄,in which the flammable gases were about 75%and could be used as fuel gas.The liquid(pyro-oil) included water and oil,and the oil could be used as chemicals since it was mainly composed of phenolic compounds(mainly monophenol) such as above 50%of phenol.About 22%(mass ratio) metal balls were obtained in solid residues from pyrolysis of Multi-layer CCL.The rest were glass fibers and a small amout of carbon(about 7%) and higher purity glass fibers could obtained by burning.There was about 30%metal balls obtained from Single-side CCL pyrolysis solid residues.The rest of which was mainly coke-like solid.And the carbon content of which was higher than 85%and they could be activated and used as absorbing material.So it was suitable to recycle the waste PCBs of different types in classification.The metal has been concentrated by controlling the pyrolysis temperature.