A Study On The Debromination Of Waste Printed Circuit Board Powder In Pyrolysis Process

Printed circuit board, as the core member, comprises a variety of valuable metals (such as gold, silver, copper, aluminum, iron, and lead, etc), and non-metallic substances (such as glass fiber and epoxy resin, etc). Waste printed circuit board recycling is a research subject of a widespread concern at home and abroad. But the pyrolysis oil, one of pyrolysis products, contains much halogen especially bromine, which restricts the comprehensive recycling of pyrolysis oil. Therefore, it’s an urgent need to study the mechanism of the removal of the halogen and develop a technology that can efficiently remove the halogen from pyrolysis oil.Waste printed circuit boards (WPCBs) powder as the research object, was separated the value metal in physical separation process.There are three main contents in this study:The effect of pyrolysis conditions on the compositon of the vacuum pyrolysis oil; The effect of various oxides on the bromie distribution from the pyrolysis products; Selecting the oxide which is best in removing the bromine, studying the mechanism of debromination and the effect of the amount on the debromination.First, this study is focused on the effect of final temperature (400℃,500℃and600℃) and heating rate (5℃/min,10℃/min and15℃/min) on the composition of printed circuit board vacuum pyrolysis oil by using GC-MS. Analysing the optimal experimental conditions, it is desirable to improve the utilization value of the pyrolytsis oil by controlling both two impact factors. The results indicate that the pyrolysis oils contain22to28compounds with the carbon number of6to18, especially the substances C6-C9with low carbon number. Phenol,4-(1-methylethyl) phenol and bisphenol A as main components, are more than65%in pyrolysis oils. From the yield of pyrolysis oil and results of GC-MS, it is concluded that sufficient pyrolysis (high content of C6-C9in pyrolysis oil) with high quality of utilizations can be attained at a heating rate of10℃/min and a constant temperature of500℃for1hour.Second, the debromination tests of epoxy WPCBs powder were carried out at the optimal experimental conditions through adding three types of oxides (Fe-based, Ca-based and Al-based) in the vaccum pyrolysis process. The effect of the oxide additives on to the distribution of organic bromine and inorganic bromine in three phases (solid, liquid and gas) of pyrolysis products was studied by ion chromatography and oxygen bomb combustion method. The results indicate that Fe3O4and CaCO3display the better in the debromination, compared to the other Fe and Ca oxides. The efficiency of transfering organic bromine into inorganic bromine increases from46.42%without any oxide to82.25%and92.13%with the Fe3O4and CaCO3respectively. At the same time, the distribution of bromine in the pyrolysis oil reduces from72.10%to8.91%and7.69%.Finally, Fe3O4as the final selection of additives, displaying the best in debromination in Fe-based oxides, was studied the effect of amount on the distribution of bromine in the pyrolysis products and subsequently analysed the optimal amount. Fe3O4causes the bromine from the gas and liquid transfer to the solid phase. The bromine in pyrolysis liquid reduced87.30%with the ratio of1:1.