On Multi-Source Sludge Smoldering Process

Abstract Smoldering, as an emerging technology, exhibits significant potential for the efficient disposal of organic solid waste with high moisture content; however, theoretical models targeting multi-source blended fuels remain scarce. This work systematically investigates the smoldering characteristics and kinetic behaviors of municipal sludge (MS) and electroplating sludge (ES) under different airflow rates. The aim is to provide theoretical insights and model support for applying smoldering technology to various sludge feedstocks. An experimental smoldering reactor was constructed to examine the smoldering of both individual and blended sludges. Kinetic parameters were extracted using the smoldering isothermal fitting method (SIFM), and the activation energy asymptotic (AEA) simplified model was employed to predict and validate the smoldering temperatures of different sludges. The results demonstrate that MS and ES can achieve stable smoldering at specific blending ratios, thereby facilitating the synergistic co-disposal of multi-source sludges. As the MS proportion increases, the smoldering temperature rises and propagation stability is enhanced. Kinetic analysis reveals that the activation energy of blended sludge decreases with increasing MS content. When these parameters are input into the AEA model, the predicted results show good agreement with experimental data, with minor deviations under certain airflow conditions. Overall, the smoldering kinetic parameters obtained via SIFM are more suitable for the AEA model than those from non-isothermal thermogravimetric analysis (TGA), with deviations within ±6%. This agreement validates the model’s applicability to smoldering processes of different sludge types.