Interactions of sulfur-containing gas with magnesia-chromite refractory in nickel flash smelting furnace

As-received and spent magnesia-chromite refractories from a nickel flash smelting furnace were analyzed and compared to shed light on the interactions between the gas phase and the refractory material, a topic that has not received previous research effort. Based on the results, process-originated gaseous sulfur-containing species, such as SO₂ and SO₃, played a key role in the refractory reactions. In the absence of a surface deposit, the hot end of the refractory underwent attack by SO₂, resulting in sulfation of both the periclase and chromite phases, which has not been reported before. In the presence of a surface deposit, the sulfation of main phases in the near-surface regions did not occur, but sulfur-bearing species diffused deeper into the refractory material, where they reacted with MgO and CaO, forming MgSO₄ and CaSO₄. In addition to the detected sulfur penetration, impurity elements, e.g., As; K, and Pb, had diffused towards the cold end of the refractory. This suggests these elements could have entered the refractory as gaseous species and then condensed at low enough temperatures.