Application Of Ferrochrome Slag In Magnesium Tundish And Its Mechanism Of Action

Chromite slag is the waste slag produced in the smelting process of chromite alloy,because it contains soluble hexavalent chromium ion with collateral toxicity and is regarded as one of the hazardous waste,and chromite slag’s main chemical composition is Mg O,Al₂O₃,Si O₂,the main phase is magnesium peridot and magnesium aluminum spinel phase,high fire resistance,has a higher use value.With the increasing scarcity of mineral resources,land resources and environmental protection in China,how to effectively recover metal resources from these secondary resources,produce high value-added products and reduce environmental pollution has become a huge problem we are facing today.In this experiment,the precipitation amount of Cr⁶⁺was detected by soaking chromium iron slag in solution,and the precipitation amount of Cr⁶⁺was studied under the influence of different initial PH,particle size and soaking time.The results showed that the precipitation of Cr⁶⁺ions was inhibited when the initial PH was acidic,and promoted when the initial PH was alkaline.The precipitation amount of Cr⁶⁺ions in alkaline solution is always higher than that in acidic solution.Under the same PH,the finer the chromite slag particle size,the more Cr⁶⁺precipitation.When PH was 10 and particle size was 1.5-1.0,the precipitation of Cr⁶⁺was0.115 mg/L.At 0.045 mm size,the precipitation of Cr⁶⁺was 1.070 mg/L.More and more Cr⁶⁺ions are precipitated from ferrochrome slag with the increase of time.When soaking for 30days,the precipitation amount of Cr⁶⁺reached saturation,and no longer changed significantly with the increase of soaking time.When the size of ferrochrome slag does not exceed 0.074mm,the precipitation of Cr⁶⁺does not exceed the emission standard of GB8978-1996（c≦0.5mg/L）.The change of phase and microstructure of ferrochrome slag as the matrix of magnesia dry material during high temperature sintering was studied,and the solid solution of Cr⁶⁺was investigated.The study shows that the magnesium aluminum spinel in the chromite slag carried out secondary spinel,when the amount of chromite slag in the matrix is 10%,the development of the magnesium aluminum spinel crystal is relatively complete,and found that the secondary spinel of magnesium aluminum spinel has a solid solution of chromium ion.The Cr⁶⁺ion precipitation of matrix samples containing chromium iron slag was measured,and it was found that the precipitation of 0.380 mg/L at the limit particle size of 0.045 mm did not exceed the emission standard of GB8978-1996.The effects of ferrochrome slag on the physical properties and slag resistance of magnesia tunic dry material after high temperature heat treatment were studied,and the corresponding properties were compared with those of magnesia dry material without introducing ferrochrome slag.The results show that the line change rate of ferrochrome slag at3wt%is-0.5%,the volume density and porosity are 2.41 g/cm3 and 31.4%,respectively,the flexure resistance and pressure resistance at room temperature are 15 MPa and 41 MPa,respectively,and the penetration depth of slag is 4 mm.The high temperature line change rate of magnesia dry material introduced without ferrochrome slag is-2.0%,the volume density and porosity are 2.35 g/cm³ and 34.4%,respectively,the flexing-compressive strength is 12MPa and 34 MPa,and the penetration depth of slag is 6.5 mm.The comparison results show that the samples with 3%ferrochrome slag are better than those without.