冷冻对脱水污泥干燥与燃烧特性的影响

Effect of freezing on drying and combustion characteristics of dewatered sludge

为了研究冷冻对脱水污泥干燥与燃烧特性的影响,考察了不同冷冻温度对污泥干燥效果的影响.利用同步热重分析仪(TG-DTA)研究了不同冷冻温度和升温速率对脱水污泥燃烧特性的影响,并进行了污泥燃烧动力学分析.结果表明:与原泥相比,冷冻将脱水污泥变成了可进行破碎的硬质结构,当温度降到-20℃时,破碎污泥的干燥速率提升了41.46%,干燥时间缩短了41.67%.冷冻后的脱水污泥在燃烧过程中有3个失重阶段:水分的析出、挥发分的析出与燃烧、部分挥发分与固定碳的燃尽.随着冷冻温度的降低,污泥着火点升高,挥发分释放特性指数、可燃指数、燃尽指数和综合燃烧特性指数增加.通过对污泥燃烧动力学分析发现,峰前反应级数取n=0.9,峰后反应级数取n=1.1.污泥冷冻后的表观活化能比原泥高,并且表观活化能随着冷冻温度的降低而增加.

This work explored the effect of freezing operation on the drying and combustion characteristics of dewatered sludge and different freezing temperatures on the characteristics of the drying process for the sludge.In addition,the effect of different freezing temperatures and heating rates on the combustion characteristics of dewatered sludge were investigated by thermogravimetric analysis(TG-DTG).Then the dynamics analysis was carried out.The results indicated that compared with the original sludge,freezing turned the dewatered sludge into a hard structure that can be crushed,and when the temperature was dropped to -20℃,the drying rate of the crushed sludge was improved by 41.46%,and the drying time was shortened by 41.67%.Three degradation stages,dehydration,combustion of volatile and combustion of the fixed carbon were identified in the combustion process of the freezing dewatered sludge.As the temperature decreased,the ignition point,the volatile releasing index,the flammability index,the burnout index,and the general combustion index increased.According to the dynamics analysis,the reaction order of pre-peak was 0.9 and post-peak was 1.1.The apparent activation energy of the frozen sludge was higher than that of the original sludge,and as the temperature decreased,the apparent activation energy would decrease.