Separation of Iron and Calcium from a BSSF Steelmaking Slag Through Acid Leaching

Abstract

Considering the BSSF steelmaking slag generated in a Brazilian steelwork, it would be worth to separate iron and calcium from it, with the objective of increasing its iron content, or producing Fe₂O₃ and CaO by selective precipitation from cations in aqueous solution. In this way, materials could be produced and used in-house, e.g., sintering plant. This possibility was explored through acid leaching for an industrial sample. A possibility to increase concentration of iron of the slag is to leach it with a 2 mol.L^-1 HCl solution; in this condition, 63.6% of the CaO is extracted from the slag to the aqueous solution, and Fe content of the slag increases from 27.4 to 37.1 wt%. Another possibility is to use HCl 5 mol.L^-1; in this condition, 86.8% of the Fe and 90.7% of the CaO are transferred to the liquid solution. Then separation of iron and calcium can be achieved by selective precipitation: firstly, adding ammonia to precipitate Fe(OH)₃, and then calcinating it to produce Fe₂O₃ (~ 200 °C); in the following, adding sodium carbonate to precipitate CaCO₃, which in turn can be calcinated to produce CaO (~ 900 °C). In this way, Fe₂O₃ and CaO could be produced.

Keywords:
Steelmaking; BSSF; BOF slag; LD slag; leaching; slag valorization