Steam gasification reactivity of chars from heavy oil residue

The gasification reactivity of heavy oil residue chars in steam atmosphere was studied by Thermal Gravimetric Analyzer (TGA) and micro-crystalite of the char was analyzed by X-ray diffraction (XRD). The effects of heating rate, pyrolysis temperature, residence time, gasification temperature and the partial pressure of steam were evaluated separately. The results show that at 950℃ and 60% partial steam pressure, gasification reactivity of chars formed at slow heating rate is lower than that formed at fast heating rate. With increasing pyrolysis temperature and residence time, the reactivity of char decreases. Gasification temperature is the main factor influencing the gasification rate. From 900 to 1 050℃ the gasification time is almost halved with the increasing temperature of 50℃. The increasing of steam partial pressure can improve the gasification rates greatly until the partial pressure comes to 60%, and after that it has no significant effect. The homogeneous model and the shrinking core model were used to characterize the gasification kinetic parameters. The later model is better and the apparent activation energy is 195.0 kJ/mol, the preexponentiol factor A₀ is 2.6×10⁷min^-1.