Evolution Mechanisms of Gas-Solid Products in Multi-Source Sludge Pyrolysis: Synergistic Regulation by Temperature and Time Parameters

Pyrolysis, as an efficient thermochemical conversion technology, demonstrates substantial advantages in achieving reduction and resource recovery of landfill sludge (LS). This work systematically examined the effects of pyrolysis temperature, residence time, and sludge type on the yield and compositional transformation of pyrolysis gases, as well as the yield and structural characteristics of the derived biochar, using LS and four other types of sludge as subjects. The research results indicate that as the pyrolysis temperature increased from 300 to 900 °C, the total gas yield of the LS sample rose markedly from 11.0 to 139.8 L/kg. The biochar obtained at 600 °C possessed the highest specific surface area (26.327 m 2 /g), with pore sizes primarily concentrated in the range of 10–20 nm. Extending the residence time facilitated the continuous release of gaseous products but exerted minimal influence on the yield of the solid-phase products. The pyrolysis responses varied considerably among different sludge types. Municipal sludge (MS) exhibited the highest gas production yield (197.5 L/kg), whereas LS demonstrated a greater carbon retention rate (73.7%). This work, based on a systematic analysis of product conversion behaviors, elucidated the correlation mechanism between parameter regulation and product performance during the pyrolysis process, thereby offering theoretical foundations and data support for optimizing LS pyrolysis conditions and enhancing product utilization efficiency.