Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 w...Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 wt pct graphite were isothermally oxidized at 1000-1350℃. Weight loss data was compared with predictions of the model. A mixed 2-stage mechanism comprised of pore diffusion plus boundary layer gas transfer was shown to generally control the oxidation rate. Pore diffusion was however more effective, especially at graphite contents lower than 10 wt pct under forced convection blowing of the air. Model calculations showed that effective gas diffusion coefficients were in the range of 0.08 to 0.55 cm^2/s. These values can be utilized to determine the corresponding tortuosity factors of 6.85 to 2.22. Activation energies related to the pore diffusion mechanism appeared to be around （46.44±2） kJ/mol. The estimated intermolecular diffusion coefficients were shown to be independent of the graphite content, when the percentage of the graphite exceeded a marginal value of 10.展开更多
An investigation on the oxidation mechanism of the graphite in the MgO-C refractory materials is helpful to improving both the quality of these materials and to preventing and/or lowering of the adverse effects of the...An investigation on the oxidation mechanism of the graphite in the MgO-C refractory materials is helpful to improving both the quality of these materials and to preventing and/or lowering of the adverse effects of the high-temperature oxidation. In this research, the oxidation behavior of the MgO-C refractories containing 5～20 wt% graphite was studied via weight-loss method. Atmospheric air was used for oxidation at temperatures ranging from 900℃ to 1300°C and the experimental data were compared with those obtained from the dimensionless kinetic equations of the shrinking core model, in order to determine the oxidation mechanisms of the refractories. The best fit was achieved with the porous layer diffusion control regime. Oxidation mechanism tends, however, to slightly deviate from pure pore diffusion control to pore diffusion-external gas transfer regime in the samples having more graphite contents (e.g. 20%).展开更多
文摘Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 wt pct graphite were isothermally oxidized at 1000-1350℃. Weight loss data was compared with predictions of the model. A mixed 2-stage mechanism comprised of pore diffusion plus boundary layer gas transfer was shown to generally control the oxidation rate. Pore diffusion was however more effective, especially at graphite contents lower than 10 wt pct under forced convection blowing of the air. Model calculations showed that effective gas diffusion coefficients were in the range of 0.08 to 0.55 cm^2/s. These values can be utilized to determine the corresponding tortuosity factors of 6.85 to 2.22. Activation energies related to the pore diffusion mechanism appeared to be around （46.44±2） kJ/mol. The estimated intermolecular diffusion coefficients were shown to be independent of the graphite content, when the percentage of the graphite exceeded a marginal value of 10.
文摘An investigation on the oxidation mechanism of the graphite in the MgO-C refractory materials is helpful to improving both the quality of these materials and to preventing and/or lowering of the adverse effects of the high-temperature oxidation. In this research, the oxidation behavior of the MgO-C refractories containing 5～20 wt% graphite was studied via weight-loss method. Atmospheric air was used for oxidation at temperatures ranging from 900℃ to 1300°C and the experimental data were compared with those obtained from the dimensionless kinetic equations of the shrinking core model, in order to determine the oxidation mechanisms of the refractories. The best fit was achieved with the porous layer diffusion control regime. Oxidation mechanism tends, however, to slightly deviate from pure pore diffusion control to pore diffusion-external gas transfer regime in the samples having more graphite contents (e.g. 20%).
