Macrostrength and Pore Structure of Coke Subjected to Gasification and Annealing under Blast Furnace Conditions

Metallurgical cokes were subjected to gasification by CO-CO2-N2 gas with blast furnace-like composition-temperature profile to 1400 °C and annealing under N2 to 2000 °C. The degradation of cokes strength after reaction and annealing was characterised using I-drum tumbling and tensile testing. The I-drum tumble strength of the cokes after processing was considerably higher than that measured in standard CSR/CRI tests. Pore structure of cokes was examined using image analysis. Porosity and pore size were both enlarged by gasification and annealing; The pore structure change during gasification was mainly as a result of Boudouard reaction; the pore structure development upon annealing was attributed to the reactions of mineral matters with carbon and transformation within the carbon framework. The pore structure of all cokes after annealing and gasification, showed a decrease in average pore roundness and an increase in the area fraction of low roundness pores suggesting an increase in pore connectivity. Increasing volume of connected pores during annealing and gasification was a major factor causing the degradation of cokes under the simulated blast furnace conditions.