Predicting the vanadium speciation during petroleum coke gasification by thermodynamic equilibrium calculation

Abstract High temperature gasification has been considered as one of the most promising routes for the clean and efficient utilization of high-sulfur petroleum coke (petcoke). However, petcoke usually contains high content of vanadium (V). It has been proven that V element in petcoke can lead to fouling or corrosion problems in the process of combustion, which captures the attention to the fate of V during petcoke gasification. In this paper, thermodynamic equilibrium calculations based on the FactSage were used to investigate the reaction mechanism of V with the main associated mineral elements (Si, Ca, Al, Fe, Ni and Na) during petcoke gasification. The influence of gasification temperature and atmospheres on the V species equilibrium composition was also evaluated. The results indicate that V reacts with the mineral elements of Ca, Fe and Na to form V-containing species (CaO) 3 V 2 O 5 (s), FeV 2 O 4 (s), (Na 2 O) 3 V 2 O 5 (s) and (Na 2 O) 2 V 2 O 5 (l), respectively. The presence of H 2 S(g) suppresses the reactions of V with Ca and Fe due to the formation of sulfides (CaS and FeS). In addition, it is verified that V does not participate in the reactions with Si, Al and Ni. However, the associated mineral elements may have remarkable co-effects on V species equilibrium composition. Ca reacts with Si or Al easily to form the Ca-containing minerals (CaSiO 3 (s), Ca 3 Si 2 O 7 (s), Ca 2 SiO 4 (s), CaAl 4 O 7 (s), CaAl 2 O 4 (s)), impeding the formation of (CaO) 3 V 2 O 5 (s). Na combines with Al to generate Na-containing minerals (NaAlO 2 (s), Na 2 Al 12 O 19 (s)), inhibiting the formation of (Na 2 O) 3 V 2 O 5 (s) and (Na 2 O) 2 V 2 O 5 (l). When all of the main associated mineral elements are present, the V-containing species formed in the whole process of gasification are V 2 O 3 (s), FeV 2 O 4 (s) and a small amount of VO 2 (g).