Gasification of metallurgical coke in CO2-CO-N2 with and without H2
The reaction kinetics of the gasification of a metallurgical coke was investigated using a thermogravimetric analyzer (TGA) in the temperature range of 1173–1873 K, particle size of 200–2000 μm, and CO2 content of 5–20 vol% in CO2-CO-N2 and CO2-CO-H2-N2 gas mixtures. The gasification rate in the presence of H2 is significantly higher than that without H2 at lower temperatures. The enhancing effect of H2 diminishes with temperature increase. Two temperature zones corresponding to chemical reaction controlled regime and diffusion controlled regime are identified. The reaction transitions from chemical reaction control to diffusion control at 1467 K for gasification without H2 in comparison to 1364 K with H2. It indicates that diffusion becomes the controlling step at a lower temperature in the H2-containing gas mixture due to the generation of H2O through water-gas shift reaction. With increasing gasification rate with temperature, the gasification becomes controlled by the diffusion of CO2, which is further demonstrated by the decreasing reaction rate with increasing particle size and the increasing reaction order as temperature increases.