Dissolution rate and mechanism of solid MgO particles in synthetic ladle slags

Four types of slag with different basicity, MgO and Al2O3 content were used to simulate the synthetic ladle slag. The dissolution behavior of MgO particles was then investigated using the direct dissolution method. The results show that the dissolution rate of MgO particles strongly depends on the slag composition and temperature. At the initial stage, the dissolution rate shows a good linear relation with time. Once spinel product forms around the MgO core, the dissolution rate decreases remarkably. The formation and function of the inner slag layer between the MgO core and the spinel product were investigated in detail. The inner slag layer is possible to act as a transfer passage for Mg element from the MgO core to the spinel product. The rate-limiting step of MgO dissolution is determined by the diffusion of spinel product toward the bulk slag.

► Dissolution rate shows a good linear relation with time only at the stage.
► The inner slag layer is defined firstly.
► The inner slag acts as a transfer passage from MgO core to the spinel product.
► The rate-limiting step of MgO dissolution is decided by the spinel diffusion.