Negatively Catalyzed Gasification Characteristics of Metallurgical Coke and its Implication for Ironmaking Process

Abstract

Boric acid as a negative catalyst can decrease the coke reactivity, and increase coke strength after reaction which is essentially important for high efficient utilization of coke and stable operation of blast furnace. CO₂ gasification was conducted to investigate the gasification characteristics and kinetics of H₃BO₃ treated metallurgical coke with different loading amount and loading method. After 2.0 wt% H₃BO₃ sprayed, the thickness of coke pore walls increased from 132.41 µm to 162.34 µm, and the porosity decreased from 46.76% to 42.16%. Gasification reaction was suppressed obviously by introducing 0.5 wt% H₃BO₃. This effect is slightly increased with further addition of H₃BO₃. As characterized by reactivity index, reactivity of coke without H₃BO₃ was 9.72 × 10⁻³ min⁻¹ at 1473 K, while it decreased to 7.19 × 10⁻³ min⁻¹ when 2.5 wt% H₃BO₃ loaded. Unreacted core model was used to establish the corresponding kinetic relationship and analyze the rate-limiting step in gasification process. Internal diffusion resistance reduced as temperature increased, and rose alongside carbon conversion rate. Results from reactivity and strength analysis proved that a certain amount of H₃BO₃ sprayed onto coke surface can significantly improve the coke strength after reaction and reduce the generations of coke fine.