Effect of water vapor on the oxidation of heavy fuel and vacuum residue oil in a TGA

Abstract

The effect of water on the oxidation of two residual fuel oils (heavy fuel oil (HFO) and vacuum residual oil (VRO)) was investigated in a thermogravimetric analyzer (TGA). The oxidation process in humid atmosphere was investigated by monitoring the mass loss profiles in a wide range of conditions. The TGA experiments cover temperatures range from ambient to 800 °C, heating rates of 5, 10 and 15 °C min−1, and various oxygen and water vapor concentrations were studied. The results show a noticeable effect of humidity on the oxidation process of the two fuels, especially in the fuel deposition region, where the presence of water increased the mass decay. Kinetic analyses were performed using a model-based method, Coats and Redfern to investigate the reaction schemes in different temperature regimes. First order, 1-D diffusion and assumed random nucleation and growth mechanisms were found to capture the oxidation of HFO and VRO in different temperature regimes. Apparent kinetic parameters estimated also exhibited a noticeable effect of water vapor on the oxidation of both fuels. The interpretation of the data obtained from mass loss profiles aided in understanding the physical processes that can contribute to the efficient utilization of HFO and VRO.