基于可视化大尺寸快速升温热重分析装置的混合固废热解和燃烧特性的实验研究

Experimental study on pyrolysis and combustion characteristics of mixed MSW using a visualized fast heating macro TGA

城市固体废弃物(municipal solid waste,MSW)的燃烧依次经历干燥和热解、挥发分燃烧、焦炭燃烧三个阶段,描述样品热解、燃烧动力学特性的主要参数包括样品质量、温度、尺寸和点火特性等。实际固废焚烧处理过程的主要特征包括升温速率高(400 K/min以上)、样品尺寸大、组分复杂和样品体积收缩等。然而,常规用于测量固废热解、燃烧的实验设备如TGA、macro TGA和沉降炉等存在升温速率或样品尺寸受限、难以同时获取样品的质量和温度及图像信息等缺陷。为此,搭建了可视化大尺寸快速升温热重分析装置,测量了打印纸、PET塑料、松木和厨余垃圾及其混合样品在慢速升温(10 K/min,15 K/min,25 K/min)和快速升温(约500 K/min)工况下热解和燃烧的质量、温度和图像信息。结果表明:升温速率对混合样品的热解和燃烧动力学特性影响较大。慢速升温模式下,混合样品燃烧DTG曲线呈现多峰特征,且这些峰的出现时间与其四种组分的燃烧DTG曲线峰值具有对应关系;快速升温模式下,混合样品各组分的热解区间趋于重叠,燃烧DTG曲线的峰减少为一个。温度和图像信息表明,15 K/min慢速升温模式下,混合样品内部和表面的点火时间基本一致,点火时样品中心温度为191℃,燃烧发生在样品表面。快速升温模式下,升温开始后样品表面可以立即观察到挥发分的燃烧火焰,随后燃烧逐步向样品内部扩展。随着燃烧的进行,样品尺寸持续收缩,直至燃尽。

The combustion of municipal solid waste(MSW)goes through three stages:drying,pyrolysis and volatiles combustion,and char combustion.Key parameters describing the pyrolysis and combustion kinetics of samples include sample mass,temperature,size,and ignition characteristics.The primary features of the actual solid waste incineration process include high heating rate(above 400 K/min),large sample size,complex composition,and volume shrinkage of the sample.However,conventional experimental equipment used for measuring the pyrolysis and combustion of solid waste,such as TGA,macro TGA,and drop tube furnace,have limitations in terms of heating rate or sample size,making it difficult to simultaneously obtain information on the sample’s mass,temperature,and image.A visualized fast heating macro thermogravimetric analysis device(referred as macro TGA)was built to measure the mass,temperature,and image information of paper,PET,pine,kitchen waste,and their mixed samples under slow heating(10 K/min,15 K/min,and 25 K/min)and fast heating(approximately 500 K/min)conditions.The results showed that the heating rate has a significant impact on the pyrolysis and combustion kinetic characteristics of the mixed sample.In slow heating mode,DTG curve of the mixed sample exhibits multiple peaks,and the occurrence time of these peaks correspond to the peak of DTG curves of its four components.In rapid heating mode,the pyrolysis ranges of the components in the mixed sample tend to overlap,and the number of peaks in DTG curve decreases to one.Temperature and image information indicate that under slow heating at 15 K/min,the ignition time of the mixed sample’s internal and surface regions is basically the same,and the center temperature of the sample during ignition is 191℃,with combustion occurring on the sample surface.In rapid heating mode,volatile combustion flames are immediately observed on the sample surface after heating initiation,followed by gradual expansion of combustion into the sample’s interior.As the combustion progresses,the sample size continuously shrinks until it is completely burned.