Studies on kinetic and reaction mechanism of oil rolling sludge under a wide temperature range

Oil rolling sludge (ORS) is a kind of hazardous secondary energy and pyrolysis is an effective technology to recover oil with little secondary pollution. Extant research focused on the pyrolysis of petrochemical sludge (PS) under low-medium temperature (<900 K), few research was about ORS. Therefore, the pyrolysis behavior of ORS was investigated under a wide temperature range (300-1270 K) by thermogravimetric analyzer (TG/DTG) and X-ray diffraction spectrometer (XRD) in this research, which showed that the pyrolysis process could be divided into four stages: desorption of moisture and adsorbed gas, decomposition of light oil, cracking of heavy oil and coke formation, and interaction of mineral and coke. In addition, the model-free Starink and the Malek methods were applied to calculate kinetic triplets and determine the most probable mechanism of stage-2 to stage-4 based on various mechanism formulas. The results showed that the apparent activation energy varied from 44.77 to 196.36 kJ/mol and increased with the increase of conversion rate, while pre-exponential factor changed irregularly with heating rate. The stages 2-4 complied with the 0.7-level chemical order reaction model, random nucleation and nuclear growth reaction model and phase boundary reaction model, respectively. This study provided a theoretical support for the optimization of process conditions, prediction of product distribution and design of industrial equipment.

Automated summary

This study investigated the pyrolysis behavior of oil rolling sludge (ORS) using thermogravimetric analysis and X-ray diffraction, revealing that the process can be divided into four stages. By applying kinetic analysis methods, the study determined the activation energy, pre-exponential factor, and mechanisms for each stage, providing theoretical support for process optimization and product distribution prediction.