A型分子筛对WPCBs燃烧特性的影响

EFFECTS OF A ZEOLITE ON PYROLYSIS CHARACTERISTICS OF WASTE PRINTED CIRCUIT BOARDS

利用热重分析法研究不同气氛(空气和N_(2))、添加不同催化剂(4A和5A)下,废电路板非金属粉末(WPCBs)的燃烧特性,计算各类综合燃烧特性曲线,并建立燃烧动力学方程。结果表明:空气气氛下,WPCBs燃烧曲线存在3个明显失重峰,即挥发分析出与热解、难燃有机物分解以及固定碳热解;而N_(2)气氛下,WPCBs燃烧曲线存在1个明显失重峰和1个次失重峰,即挥发分析出与热解、难燃有机物分解。加入催化剂(4A和5A),WPCBs燃烧特性曲线的水分析出失重峰明显加强,挥发分析出与燃烧和难燃有机物分解失重峰强度明显减弱。在N_(2)气氛下,WPCBs燃烧具有较高的挥发分释放特性指数D、可燃指数C和综合燃烧特性指数S,而燃尽指数Cb较小。利用Coats-Redfern积分法计算得到不同气氛及催化剂条件下WPCBs燃烧的平均表观活化能Eav,其中Eav约为227.29 kJ/mol(空气或N_(2))、72.35~115.99 kJ/mol(空气/N_(2)+4A/5A)。修正后的质量平均表观活化能E_(m)为76.38 kJ/mol(空气)、115.09 kJ/mol(N_(2))、≤47.26 kJ/mol(空气/N_(2)+4A/5A)。WPCBs热解的挥发分1峰前反应过程拟合方程为f(α)=(1-α)^(0.5);而其峰后、挥发分2和固定碳燃尽阶段反应过程拟合方程为f(α)=(1-α)2。

In this article, thermogrmetric analysis was used to study the pyrolysis characteristics of waste printed circuit boards(WPCBs) under different atmospheres(air and nitrogen) and with different catalysts(4 A and 5 A). Various comprehensive pyrolysis characteristic curves were calculated, and the pyrolysis kinetic equations were established. The experimental results indicated that there are three obvious weight loss peaks in the pyrolysis curve of WPCBs under air atmosphere, corresponding to the volatile emission and pyrolysis, the decomposition of refractory organic matter and the fixed carbon pyrolysis respectively. Then, the two obvious weight loss peaks appeared in the WPCBs combustion curve under air atmosphere, corresponding to the volatile emission and pyrolysis and the decomposition of refractory organic matters. In the atmosphere of air and nitrogen, with the addition of catalyst(4 A and 5 A), the weight loss peak of water precipitation in WPCBs pyrolysis characteristic curve was significantly enhanced, and the strength of volatilization analysis and weight loss peak of pyrolysis and decomposition of refractory organic matter was significantly reduced. Under nitrogen atmosphere, WPCBs pyrolysis had higher volatile characteristic index D, flammability index C and comprehensive combustion index S, while the burnout index Cb was smaller. Nevertheless, the apparent activation energy(E_(av)) of WPCBs pyrolysis under different atmosphere and catalyst conditions was calculated by using Coats-Redfern integral method. The E_(av) was 227.29 kJ/mol(air or nitrogen) and 72.35~115.99 kJ/mol(air/nitrogen+4 A/5 A). After correction, the average mass apparent activation energy E_(m) was 76.38 kJ/mol(air), 115.09 kJ/mol(nitrogen), ≤47.26 kJ/mol(air/nitrogen+4 A/5 A). Consequently, the reaction mechanisms of the pre-peak of the first volatile stage could be described as f(α)=(1-α)^(0.5), while the post-peak of the first volatile, the pre-peak and post-peak of the second volatile stage and the fixed carbon combustion stage could be described as f(α)=(1-α)2.