Kinetic Analysis and Product Distribution of Co‐Pyrolysis of Oily Sludge and Walnut Shell: Effects of Temperature and Mixing Ratio

Co‐pyrolysis is potentially an effective treatment of oily sludge (OS) for oil recovery. The co‐pyrolysis behavior and product distribution of OS and walnut shell (WS) were systematically investigated. Thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG‐FTIR) and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) were employed to examine the effects of varying mixing ratios and temperatures on pyrolysis characteristics. The results revealed a clear synergistic interaction between OS and WS during co‐pyrolysis. FTIR results showed that the addition of WS altered the reaction path, reduced CO 2 emissions, and changed the distribution of volatile products, resulting in improved pyrolysis efficiency and environmental performance. Kinetic analysis demonstrated that the co‐pyrolysis was predominantly diffusion‐controlled, with the strongest synergy and best model fit observed at a 1:1 OS‐to‐WS ratio at an OS‐to‐WS ratio of 1:1. In terms of product distribution, the incorporation of WS significantly reduced the yield of heavy components, thereby enhancing the quality and conversion efficiency of the pyrolysis oil. Pyrolysis temperature had a notable impact on the composition of volatile products, where acid compounds were markedly suppressed due to synergistic effects at temperatures of 600°C and below.