调理脱水污泥的热解特性及动力学分析

Pyrolysis characteristics and kinetics analysis of conditioned dewatered sewage sludge

利用TGA(Thermogravimetric analysis)热分析技术对污水处理厂原始污泥及调理脱水污泥进行了实验研究,获得了不同升温速率下污泥的TG(Thermogravimetric)和DTG失重曲线.实验发现,不同调理脱水污泥热解特性复杂,且热解动力学在不同转化率下对应的动力学反应也不同.并利用M-KAS(Kissinger-AkahiraSunose)模型和Discrete DAEM(Discrete distribute activation energy model)模型对不同调理污泥进行了动力学参数研究.结果表明,污泥的非等温热解过程包含3个失重阶段;升温速率影响污泥热解特征温度,随着升温速率的提高,失重曲线向高温区滑移.利用上述模型计算的动力学参数变化趋势表明所采用的Fenton及赤泥复合调理对污泥热解特性有很大影响,Fenton调理有助于污泥EPS(Extracellular polymeric substances)破坏,影响热解反应中的形核过程,进而影响热解动力学变化趋势;赤泥调理后,赤泥更容易与破坏的污泥细小颗粒结合,增加了污泥热解反应数量,影响整个污泥热解过程.从计算结果可以看出污泥热解由多步反应组成,整个热解过程动力学参数不断变化.

Raw and conditioned dewatered sewage sludges of sewage treatment plant were analysed by the TGA thermal analysis technique,and TG and DTG curves were obtained at different heating rates. Experimental results showed that the pyrolysis characteristics of different conditioned dewatered sludge were complex and pyrolysis kinetics with different conversion ratios corresponded to different kinetic reations. M-KAS model and Discrete DAEM model were also applied to analyze the kinetic parameters of different conditioned dewatered sewage sludge. The results showed that the non-isothermal decomposition process of dewatered sewage sludge contained three weight loss stages and the heating rate influenced the characteristic temperature zones of pyrolysis. With increasing heating rate,the weight loss curve slipped to the high temperature zone. The variations of kinetic parameters calculated by the above models showed that composite conditioning of Fenton and red mud had a great influence on the pyrolysis characteristics of dewatered sewage sludge. Fenton reagent can break the extracellular polymeric substances of sludge,thus affecting the nucleation process in the thermal decomposition reaction,thereby affecting the pyrolysis dynamics trend of sewage sludge. With red mud conditioning,red mud was easily combined with small sludge particles,increasing the number of pyrolysis reactions,thus improving the whole pyrolysis process. It can be concluded from the results that the pyrolysis reactions of dewatered sewage sludge were composed of several kinetic reactions with variable kinetic parameters.