Thermodynamic model and kinetic compensation effect of oil sludge pyrolysis based on thermogravimetric analysis

Abstract

Oil sludge is an organic solid waste in the petrochemical industry and improper treatment of oil sludge will cause environmental pollution. Pyrolysis is an effective way to realize its resource reuse. In order to understand the pyrolysis behavior and thermodynamic characteristics of oil sludge, four oil sludge samples from storage tanks were used as the research object, and pyrolysis experiments were carried out at heating rates of 5?, 10?, and 15? per minute under a nitrogen atmosphere. The kinetic parameters of pyrolysis of oil sludge are calculated by three equal conversion methods, Friedman method, Flynn-Wall-Ozawa method and Distributed activation energy model, and the most possible thermodynamic models for the main pyrolysis phase were analyzed and discussed by introducing the Malek method. The results show: high heating rate can promote the pyrolysis of oil sludge and in the pyrolysis stage, the apparent activation energy increases with the increase of the conversion rate. The apparent activation energy calculated by the Friedman method method is more reliable. The average apparent activation energies of the four oil sludge are 221.23, 84.71, 94.67, and 116.56 kJ/mol, respectively. The apparent activation energy and the pre-exponential factor are positively correlated, indicating that there is a kinetic compensation effect in the pyrolysis process. The thermodynamic models of the four oil sludge samples are all 3-D diffusion models, but their integral functions are different. The research results can provide theoretical support for the industrialization, harmlessness, and resource utilization of oil sludge pyrolysis.