Research On Pyrolysis Of Waste Printed Circuit Boards

With the development of the world economy and the advancement of technology,the penetration rate and replacement rate of electronic equipment have risen sharply.The huge wave of electronic waste is coming.Printed waste circuit boards are one of t he core dismantling products produced after the dismantling of waste electronic equip ment and electronic products.Due to the printed waste circuit boards include rich reso urce properties of valuable metals and the potential hazards of environmental risks dur ing the disposal process,and there efficient disposal and recycling have become a hot spot for researchers from all over the world.This article takes waste circuit boards as t he research subject,explores the technical scheme of pre-treatment before they are put into the furnace by using the copper pyrometallurgical production line,and mainly carries out the research of conventional pyrolysis and microwave pyr olysis to further promote its recycling.Based on the waste computer circuit boards an d waste TV circuit boards,the pretreatment of detinning,material pyrolysis characteri stics and kinetics,microwave dielectric constant and heating characteristics of waste c ircuit boards are studied.Under conventional pyrolysis and microwave pyrolysis cond itions,the effects of pyrolysis temperature and nitrogen flow rate on the yield distribut ion of pyrolysis products were investigated,and the composition and properties of soli d,liquid and gas pyrolysis products were studied.(1)Detinning pretreatment is beneficial to the recovery of tin and the enrichment of copper in solid products,and the recovery rates of detinning of waste computer circuit boards and TV circuit boards are 59.8%and 56.9%,respectively.The main pyrolysis weight loss stage of the material after detinning is 270-510℃,and the pyrolysis kinetic parameters such as activation energy at different heating temperatures are calculated.The microwave dielectric constant and heating curve of the material after tin removal have been measured,which shows that it has good microwave absorbing performance.(2)The results show that pyrolysis temperature and nitrogen flow rate have significant effects on the yield of solid,gas and liquid products from the pyrolysis of waste computer circuit boards.The pyrolysis temperature has a greater impact on the product yield,and the solid product yield decreases with increasing temperature,while the gas yield shows an upward trend as the temperature rises.In conventional pyrolysis,the liquid yield first increases and then decreases with the rise of temperature,and the liquid yield shows an upward trend with the rise of temperature in microwave pyrolysis.The composition and properties of the pyrolysis products were analyzed,and the optimal pyrolysis conditions were obtained as follows:conventional pyrolysis temperature 600℃,microwave pyrolysis temperature 500℃.Under conventional pyrolysis,the solid product yield was 75%,of which copper content was 22.67%,tin content was 1.87%and silver was 0.036%;under microwave pyrolysis,solid product yield was 81.8%,in which copper,tin and silver content were23.05%,1.85%and 0.025%,respectively,which realized metal enrichment and was conducive to subsequent recovery.(3)Pyrolysis temperature and nitrogen flow rate have obvious effects on the yield of solid,gas and liquid products from waste TV circuit board pyrolysis,which is similar to the influence trend of waste computer circuit boards.The composition and properties of pyrolysis products were analyzed.Under the optimized conditions,the solid product yield of conventional pyrolysis is 73%,in which the content of copper,tin and silver is 21.24%,0.90%and 0.02%,respectively;the solid product yield of microwave pyrolysis is 77%,in which the content of copper,tin,silver and other metals are 21.43%,0.94%and 0.017%,respectively,which realized the enrichment of the metal in the solid product.(4)Compared with the conventional pyrolysis oil,the content of phenol in the pyrolysis oil increased under microwave conditions,and the furan content decreased.Under the optimized pyrolysis conditions,waste computers and TV circuit boards are pyrolyzed,and their pyrolysis gas the calorific value has a calorific value of 18.78-21.23MJ/Nm~3,and the combustion value of pyrolysis oil is 15.44-20.15MJ/Nm~3,which can be used as fuel.