The pyrolysis and oxy-fuel combustion characteristics of petrochemical wastewater sludge (PS) were studied in air (O-2/N-2) and oxy-fuel (O-2/CO2) atmospheres using non-isothermal thermogravimetric analysis (TGA). Pyrolysis experiments showed that the weight loss profiles were almost similar up to 1050 K in both N-2 and CO2 atmospheres, while further weight loss took place in CO2 atmosphere at higher temperatures due to char-CO2 gasification. Compared with 20% O-2/80% N-2, the drying and devolatilization stage of PS were delayed in 20% O-2/80% CO2 due to the differences in properties of the diluting gases. In oxy-fuel combustion experiments, with O-2 concentration increasing, characteristic temperatures decreased, while characteristic combustion rates and combustion performance indexes increased. Kinetic analysis of PS decomposition under various atmospheres was performed using Coats-Redfern approach. The results indicated that, with O-2 concentration increasing, the activation energies of Step 1 almost kept constant, while the values of subsequent three steps increased. (C) 2015 Elsevier Ltd. All rights reserved.