Co-pyrolysis of steel rolling oil sludge and peanut vine: kinetic analysis and synergistic iron resource recovery
摘要
This study investigated the co-pyrolysis characteristics of steel rolling oil sludge and peanut vine biomass, as well as the distribution of their by-products. Thermogravimetric analysis and tube furnace experiments were employed to examine the effects of mixing ratio, heating rate, and pyrolysis temperature. The pyrolysis process could be divided into three stages: water evaporation (room temperature− 130 °C), decomposition of organic components (130–490 °C), and reduction of iron oxides (490–900 °C). The addition of peanut vine significantly accelerated the pyrolysis reaction and lowered the activation energy; at a conversion of 0.8, the activation energy dropped from 153.13 kJ mol−1 for pure sludge to 21.79 kJ mol−1 for the 3:7 (sludge/vine) mixture, representing an 86% reduction. Kinetic analysis revealed that for the mixtures the activation energy increased with rising heating rate and conversion, whereas for pure sludge it decreased with heating rate; furthermore, higher peanut vine content markedly reduced the activation energy at elevated conversions. Examination of the solid residues showed that both the metallization rate and iron content increased with pyrolysis temperature. For the 5:5 mixture, the metallic iron content rose from 12.19 at 700 to 48.95% at 900 °C, although the metallic iron yield did not display a linear relationship with the sludge proportion. An appropriate biomass addition ratio can promote the efficient recovery of iron resources, while the presence of iron exerts a catalytic effect on biomass pyrolysis. This work provides a theoretical basis for the co-disposal of biomass and steel rolling oil sludge to achieve sustainable resource exploitation and hazardous waste reduction.