Impact of Oxidizing and Reducing Conditions on the Performance of Alumina-Chrome Refractories in Copper Refining Furnaces

Due to improved resistance to corrosion by copper oxide slags, alumina-chrome refractories have supplanted traditional magnesia-chrome refractories in the tuyere area in primary copper refining furnaces, allowing for significant extensions of furnace campaigns over the past decade. A recent field trial was conducted in a primary copper refining vessel to investigate if transitioning to alumina-chrome refractories would show similar improvements in other areas of the refining furnace. Results of the trial indicated that alumina-chrome bricks subjected to repeated, localized reducing conditions in addition to highly oxidizing conditions suffered accelerated corrosion compared to alumina-chrome bricks and magnesia-chrome bricks in the surrounding areas. To more closely investigate the mechanisms at play, a laboratory study was conducted to investigate the effects that oxidizing and reducing conditions have on alumina-chrome brick when exposed to copper oxide. Alumina chrome’s resistance to corrosion by copper oxide is driven by the formation of a reaction layer that inhibits further reaction between copper oxide and the alumina chrome refractory. It is expected that cyclical exposure to oxidizing and reducing conditions during operation reduces the corrosion resistance of the alumina-chrome refractory due to disruption of this reaction layer. The completed work improves our understanding of the current limitations of alumina-chrome refractory use in copper refining vessels and provides insight into how to improve this class of products to overcome those limitations.