Volatile evolution during thermal treatment of oily sludge from a petroleum refinery wastewater treatment Plant: TGA-MS, Py-GC(EGA)/MS and kinetics study

[Display omitted] •The volatile evolution during thermal treatment of an oily sludge was discussed.•Internal diffusion had a great influence on the reaction rate during 120–360 °C.•The proportion of light and unsaturated hydrocarbons increased during 360–550 °C.•The evolution profiles of typical compounds in volatile were characterized. The volatile evolution during thermal treatment of an oily sludge derived from petroleum refinery wastewater treatment plant was investigated by in-situ pyrolytic and kinetic analysis. According to kinetic mechanism model, it was found that the internal diffusion had a great influence on volatile release during 120–360 °C, while the devolatilization rate during 360–550 °C would more depend on the concentration of remaining hydrocarbons. By Py-GC/MS, oils were trapped and analyzed respectively during 60–360 °C and 360–550 °C, and above 300 compounds were identified and semi-quantified of the volatiles. During 60–360 °C, the detected volatile was mainly composed of saturated aliphatics, accounting for 68.69%. More proportion of light chain aliphatic hydrocarbons and monoaromtics were observed during 360–550 °C, and the relative content of unsaturated aliphatics increased to 33.81%. From the evolution profiles of typical oil products, the volatile release during 120–360 °C would follow the order of molecular weight. But during 360–550 °C, as a result of increasing thermal-cracking degree, the release peaks of the different volatile species were corresponded to similar temperature. The gaseous and sulfur-containing compounds were also traced. Among them, CO2 was the main product above 550 °C for the decomposition of minerals, and sulfur-containing compounds were mainly generated during