Recycling of steelmaking slag fines by weak magnetic separation coupled with selective particle size screening

Abstract

Steelmaking slag fines are leftover materials generated in routine slag processing and their particle sizes are usually smaller than 12.5 mm. The steelmaking slag fines can include desulfurization (DeS) slag fines, basic oxygen furnace (BOF) slag fines, electric arc furnace (EAF) slag fines and ladle metallurgy furnace (LMF) slag fines. Low iron grades, high impurity concentrations and inappropriate particle sizes are major barriers for recycling of the steelmaking slag fines back into ironmaking and steelmaking processes. Current slag processors have failed to solve this problem in an economic way. As a result, steelmaking slag fines are either being disposed of at landfills or being stored on the ground in large quantities, not only adding a considerably heavy financial burden to steelmaking plants, but also causing enormous value losses and potential environmental liabilities. A recycling technology of weak magnetic separation coupled with selective particle size screening has been developed at ArcelorMittal Global R&D – East Chicago Laboratories, targeted at solving the problem in a cost-effective way. Samples of steelmaking slag fines from three ArcelorMittal Americas steelmaking plants were collected, characterized and tested with weak magnetic separation coupled with selective particle size screening. Test results show that existing slag processors' magnetic separators are ineffective in separating iron from steelmaking slag fines. Using the technology of weak magnetic separation coupled with selective particle size screening, steelmaking slag fines can be effectively separated to produce cleaner iron-rich products with sufficiently high iron contents and low levels of impurities to be reused.