Simultaneous recycling of Si and Ti from diamond wire saw silicon powder and Ti-bearing blast furnace slag via reduction smelting: An investigation of the effects of refractories on recycling

Abstract

The industrial wastes diamond wire saw silicon powder (DWSSP) and Ti-bearing blast furnace slag (TBFS) are important Si and Ti secondary resources, respectively. During the industrial application of recycling DWSSP and TBFS via reduction smelting, the refractories can dissolve into the molten slag, which can change the composition of the slag and influence the extraction of Si and Ti. Unfortunately, few studies on the reduction smelting of DWSSP and TBFS related to refractories have been reported, making such studies urgently needed. Therefore, the main purpose of this work was to reveal the dissolution mechanism of refractories (alumina and magnesia bricks) and the effect of refractory dissolution on Si-Ti alloy preparation. The results show that during the reduction smelting, the dissolution of alumina and magnesia bricks changed from direct dissolution into the molten slag to indirect dissolution, and the amount of magnesia bricks dissolved was less than that of aluminum bricks. Al³⁺ (aluminum brick) entering the slag could replace Si⁴⁺ in [Si_nO_2n] to form [Al_xSi_n-xO_2n]^x-, increasing the viscosity of the slag. The O^2- (magnesia brick) entering the slag could dissociate [Al_xSi_n-xO_2n]^x-, decreasing the viscosity of the slag. Therefore, compared with alumina bricks, magnesia bricks can promote slag-alloy separation and improve the extraction ratios of Ti and Si. In the case of magnesia bricks, the maximum reduction ratio of TiO₂ was 98.4 %, and the maximum extraction ratio of Si was 95.8 %. This work provides essential experimental data for the Si-Ti alloys prepared via recycling DWSSP and TBFS.

Keywords: Extraction and Separation; Refractories; Si reduction; Si-Ti alloys; Waste recycling.