Transformation behavior of vanadium in petroleum coke during high temperature CO2-gasification

Abstract

The transformation of Vanadium (V) during thermal conversion of petroleum coke (petcoke) is responsible for ash-related operational problems, such as fouling, corrosion, and deposition. In this paper, The V volatilization behavior and V compounds in ashes were investigated during petcoke gasification at the temperature range of 1100–1500°C. The occurrence modes of V in raw petcoke and their gasification residues were determined using the method of sequential chemical extraction. With increasing gasification temperature, staged volatility of V is observed. From 1100 to 1200°C, almost no gaseous V releases, while it increases from 1300 to 1500°C. It should be noted that the V volatility is strongly dependent on the occurrence modes of V in petcoke. More than 96% of V in three petcoke is associated with organic matter and stable forms. Organic-bound V shows a certain volatile behavior during gasification, and the volatile V species is believed to be VO2(g) according to thermodynamic equilibrium calculations. The stable forms of V are hardly volatilized due to their thermal stability. The residence time has an insignificant effect on V volatility because most volatile organic-bound V has been released rapidly in the initial stage of gasification. During petcoke gasification, the decomposition of organic-bound V enlarges the content of V occurring in water soluble and ion exchangeable, carbonates, and Fe-Mn oxides, which can suppress the volatility of V. Moreover, new thermally stable forms of V are also formed above 1300°C. These forms may be derived from the interaction of V with its coexisting mineral matters during gasification. Crystalline phases of vanadium trioxide (V2O3) and coulsonite (FeV2O4) are clearly present in gasification ashes.