Effect of CaO/Fe2O3 on ash fusibility during petroleum coke gasification and combustion

Abstract

Ash fusibility is closely related to ash melting, sintering and slagging, which is commonly used to guide the utilization of petroleum coke in boiler and gasifier. Calcium (Ca) and iron (Fe) show significant influence on the ash fusibility of petroleum coke. To quantify the influence of CaO/Fe2O3 mass ratio on petroleum coke ash fusibility, ash fusion temperatures (AFTs) analysis, X-ray diffraction (XRD), and FactSage were applied to investigate the characteristics of petroleum coke ash fusibility with various CaO/Fe2O3 mass ratios. The results showed that AFTs were closely associated with the CaO/Fe2O3 ratio and showed different performances in different atmospheres. In the reducing atmosphere, with the increasing of CaO/Fe2O3 ratio, the AFTs presented in turn a rapid decrease (from 0 to 2) and a smooth region (from 2 to ∞). The rapid decrease of AFTs was mainly attributed to the disappearance of high-melting point coulsonite (FeV2O4) and the formation of low temperature eutectics anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO2). The formation of high-melting point calcium orthosilicate (Ca2SiO4) inhibited the formation of CaAl2Si2O8/Ca2Al2SiO2 to keep the AFTs at a stable level. In the oxidizing atmosphere, with the increasing of CaO/Fe2O3 ratio, the AFTs presented in turn a rapid decrease (from 0 to 1), a smooth region (from 1 to 5), and a fast decrease once again (from 5 to ∞), respectively. The decline of AFTs was attributed to the substitution of NiFe2O4 by fusible minerals (Ca2V2O7/CaAl2Si2O8). The synergy effect of the refractory SiO2 and fusible minerals prevented the further decline of the AFTs.