Luženje in mineraloška kontrola kroma v žlindri nerjavnega jekla iz elektroobločne peči

Abstract

This study focuses on evaluating the leachability of chromium in Electric-Arc-Furnace stainless-steel slag (EAFS) from the perspective of mineralogical control. Mineral-phase identification results showed that EAFS mainly comprised merwinite, magnetite, dicalcium silicate, calcium aluminosilicate, eskolaite, spinel, and perovskite. The chromium in the EAFS was mainly present in the Mg-Cr spinel, Fe-Cr alloy, or distributed in the form of oxide in the matrix phase, merwinite. When undergoing leaching, the leachate of the EAFS was alkaline and reducing, and a portion of the chromium in the slag was released into the leachate and existed mainly in a trivalent state. In the early stage of leaching, the rapid dissolution of chromium-bearing silicate minerals led to a rapid increase in the concentration of trivalent chromium. However, in the middle and late stages (> 15 days) of leaching, the chromium concentration reached stable values. The geochemical model of chromium leaching from the EAFS demonstrated that the simulated values of the chromium concentration were consistent with the batch-leaching test values. The primary phase Cr2O3 in the EAFS controlled the chromium concentration in the leachate. After entering the leachate, trivalent chromium could be presented as Cr(OH)4– because Cr(III)-hydroxide was unstable in the alkaline leachate.