Recycling

In iron-making and steel-making processes, many kinds of refractory are used. They are discharged as by-product after used and contain many recyclable valuable materials. However there are problems with recycle of these materials because there are impurity contaminations. Among many types of refractory, we focused on refractories used in blast furnace trough in this study. The refractories of blast furnace trough consist of silicon carbide and alumina which are valuable materials. About 40% of the construction amont is discharged as used refractories after use. The used refractories contain 5 ~ 10% of slag which adheres to surface of refractories during use. Calcium oxide, the main component of slag, causes a decrease in the performance of recycled refractories. For performance of recycled refractories, it is necessary to reduce the slag content to 2.0%. We focused on difference of density of the slag and the used refractory, and developed a new method using floating and sinking phenomenon in fluidized bed. This method uses only powder with adjusted density and air blowing from the bottom. Therefore, the environmental load of this method is lower than the conventional wet density separation method. We made continuous processing equipment and performed continuous separation test usin the fluidized bed which density is adjusted to the density between slag and refractory. As a result, we succeeded in reducing the slag content to 0.4% and achieved the target value.