废电路板热解特性及其动力学分析

Study on the pyrolysis features and the kinetic analysis of the printed circuit board wastes

分别应用热天平和管式炉反应器对废电路板的热解行为进行实验研究。通过热重分析法,考察了在氮气气氛下,不同升温速率（10 K/min、15 K/min、20 K/min、40 K/min）对废电路板热解特性的影响。结果表明,升温速率对废电路板热解失重曲线有较大影响,反应起始温度,失重率最大时的温度和反应结束温度均随升温速率的提高而相应增加。热解动力学研究表明,废电路板热解反应符合一级反应动力学,反应活化能和指前因子均随升温速率的增大而呈上升趋势,活化能在110-180 kJ/mol,指前因子在2.0×10^7-1.2×10^13min^-1。此外,在管式炉反应器上,考察在同一升温速率（20 K/min）下不同热解终温（400℃、500℃、600℃7、00℃、800℃）对废电路板热解产物产率和气体成分分布的影响。结果表明,当温度在600℃以上时,固体残渣的产率变化不大,升高温度只是改变油气比;电路板热解气的主要成分是H2、CO、CO2、CH4、C2H4、C2H6、C3H6和C3H8,气体热值在11.24-15.21 MJ/m^3,焦油热值在24.5-27.5 MJ/kg范围内。热解后所得固体残渣是易碎的,其中玻璃纤维部分呈层状分开,很容易对残渣中的金属和玻璃纤维部分进行分离。

This paper is aimed at its authors＇ findings on their study on the pyrolysis features and the kinetic analysis of the printed circuit board（PCB） wastes.The experimental study has been done in a thermo-gravimetric analyzer（TG） and in a laboratory scale tubular furnace reactor,respectively.Kinetics analysis of PCB wastes were investigated under various heating rates（10 K/min,15 K/min,20 K/min,40 K/min） in the nitrogen atmosphere by means of thermo-balance.The results of our study indicate that the pyrolysis process of the PCB wastes is strongly influenced by the heating rates,for all the following temperatures,including the initial reaction temperature（Ts）,the DTG peak temperature（Tmax）（where the weight loss rate reaches the maximum value）,as well as the final reaction temperature（Te）,tend to increase with the increase of the heating rate.On the other hand,the application of the Arrhenius-type kinetic model helps to determine the activating energy（E） and the pre-exponential factor constant（A） for each heating rate.The activation energy and pre-exponential factor constant of the samples have also been found to increase with the increase of the heating rates.That is to say,the E values tend to increase from 110 to 180 kJ/mol while the A values would increase from 2.0×107 to 1.2×1013 min-1.Besides,a set of experiments performed in the above said furnace reactor has also been designed to evaluate the influence of the final pyrolysis temperature（FPT）（400 ℃,500 ℃,600 ℃,700 ℃,or 800 ℃） on the yields and the gas concentrations under the constant heating rate of 20 K/min.It can thus be concluded that when the FPT is above 600 ℃,the char yields would reach approximately the constant value,in which case the rise of FPT seems to lead to the change of the ratio of the oil and gas.According to the result of gas chromatography,the gas products mainly consisted of H2,CO,CO2 CH4,C2H4,C2H6,C3H6 and C3H8.Heating values of both gases and oils prove to be within the range of 11.24-15.21 MJ/m^3 and 24.5-27.5 MJ/kg,respectively.The solid pyrolysis residues prove to be friable with its glass fiber and metallic fractions separated easily.