Characterization and Sulfuric Acid Leaching of Ferrochrome Converter (CRC) Dust

Abstract

A ferrochrome converter (CRC) is used for removal of silicon and carbon from ferrochrome in stainless steel production. The raw materials are molten ferrochrome and stainless steel scrap, and the process produces a raw material for argon-oxygen-decarburization (AOD). The zinc content prevents the utilization of CRC dust (CRCD). The objective of this work is characterization and sulfuric acid leaching of CRCD and evaluation of formation mechanisms and the effects of mineralogy and microstructure on the hydrometallurgical treatment. CRCD contains critical (Cr, fluorite) and economically important (Fe, Zn) materials. The mineralogy and microstructure of CRCD are complex. The dust has been formed by many mechanisms. Lime and ferrosilicon prove that take-off of solid particles during charging is important. Also, ejection of liquid droplets is considerable because ferrochrome and slag spheres are common. The highest Zn dissolution is 93–94% and at the same time 5–15% of Cr is leached. The existence of zincite explains the high dissolution of zinc. The encapsulation, e.g., magnesiochromite enclosed into glass, explains the low chromium dissolution. The best selectivity for Zn extraction over iron, chromium, and nickel is achieved with 0.5 M, at 30 and 60 °C with both L:S 10 and L:S 20.