Oxidation kinetics of MgO–C in air with varying ash content

MgO–C refractories are extensively used in metallurgical vessels in the steel industry. The graphite plays a vital role owing to its non-wettability with slag. Though quality is very important for graphite, little published data is available on the effect of varying ash content on oxidation. Since MgO–C bricks manufactured from graphite with different ash contents are regularly used for lining converters and steel ladles at SAIL plants, a study has been conducted to select an optimum graphite with low cost. Graphites with 2·8, 4·4, 12 and 20% ash content were used to make MgO–C samples in the laboratory, and oxidation properties were evaluated using an electrically heated tube furnace. Kinetic analysis shows that a chemical reaction mechanism operates in the earlier part of oxidation, followed by a diffusion mechanism in the latter part. MgO–C manufactured from graphite with 4·4% ash content was observed to have the best oxidation resistance, with an activation energy of 43·4 kJ mol−1 during the earlier stage followed by 34·2 kJ mol−1 in the latter.