PVC裂解过程中的形貌学特征参数及其对裂解过程的表征

Morphological parameters characterizing pyrolysis process of waste polyvinyl chloride plastics

研究了聚氯乙烯(PVC)裂解反应过程中的形貌学特征,利用高清红外摄像头记录PVC从常温升至500℃的裂解反应进程中的图像序列,并借助Image Pro Plus(v6.3)数字图像处理软件进行数字化处理,得到了能够表征反应进程的形貌学特征参数量化值:即考察区域(ROI)的总像素面积(PA)和泡率(BR)。同时研究了初始形态和杂质对该两项参数的影响。结果表明,PVC的裂解过程分为4个阶段:熔化,第一裂解段,准稳定段和第二裂解段。BR能够准确反映各阶段及反应快慢,PA则可以作为PVC脱氯结束的关键形貌信号。PVC初始形态对形貌学参数的影响仅体现在熔化段,杂质的引入促进了PVC的裂解,使得各形貌参数变化所对应的特征温度提前,BR峰值变大。研究得到的PVC裂解形貌学信息可为含PVC塑料预脱氯处理过程控制及裂解器的优化提供指导。

The morphological characteristics of waste polyvinyl chloride（PVC）plastics during its pyrolysis from ambient temperature to 500℃ were investigated with a purpose to obtain the morphological parameters characterizing reaction stages.PVC granules and films were used as typical waste PVC plastics for testing,and influence of impurities was also investigated.During experiments the image changes of PVC were recorded with a high-speed infrared camera,quantitative morphological parameters were explored with the help of a digital image processing software ＂Image Pro Plus（v6.3）＂.Two representative morphological signals describing the pyrolysis stages were obtained：pixel area（PA）and bubble ratio（BR）.Experimental results showed that plastics pyrolysis involved four stages：melting,two stages of decomposition and a quasi-stable stage in between.For both PVC films and granules,the BR curve could always reflect reaction stages and reaction intensity,while PA could be used as key signal of complete HCl release.The shape of original PVC materials only affected the melting stage.When impurities were involved,the BR curve showed that intense decomposition started earlier at a lower temperature, but overall morphological characteristics remained the same.The morphological signal obtained here could be used as a guide to control dechlorination process of waste PVC and to make a better reactor design.