Enhancing the Dissolution of Spent MgO-C Refractory in Steelmaking Slag: Towards Utilization as a Steelmaking Flux

Large amounts of spent MgO-C refractory are generated in steel plants annually. Compared to external recycling, internal recycling of spent refractory as a slag additive shows many advantages. However, the dissolution rate of spent MgO-C refractory in steelmaking slag is lower and small MgO-C particles are difficult to charge into the converter. To achieve its adequate dissolution and effective utilization, the spent MgO-C refractory was crushed to fabricate MgO-C briquette with a certain mechanical strength, and their dissolution behavior in steelmaking slag was investigated. The results showed that the compressive strength of MgO-C briquette increased significantly when the binder was added. The mechanical strength of MgO-C briquette can meet the requirement for transport and charging. The MgO-C briquette was readily broken to small pieces after it was added into the molten slag, and its dissolution occurred dramatically in the beginning, generating large amounts of foaming slag. The MgO-C briquette could be fully dissolved in each slag, and only some tiny MgO particles remained. The dissolution of MgO-C briquette resulted in an increase in the MgO content and a decrease in the FeO content in slag. It could provide more than 5% MgO to molten slag. Binder type had a little effect on the dissolution of MgO-C briquette in the molten slag. Decreasing slag basicity and increasing FeO content in slag facilitated the dissolution of MgO-C briquette, causing a higher MgO content in slag. This study confirmed that the complete dissolution of spent MgO-C refractory could supply heat and large amounts of MgO to the molten slag. It will not only reduce the consumption of steelmaking flux but also achieve the resource utilization of metallurgical wastes.

Graphical Abstract