Green pyromet/hydromet pathways

The Challenge

DRI production is set to grow from 8% to 24% pf iron production by 2050 (the MRIWA green steel report 2023). To make this production economic higher grade iron ores will be required. An increasing proportion of mined iron ore in Western Australia will not be of suitable grade for DRI.

Key Findings

By exploring which combined low- to mid-temperature pyrometallurgical-hydrometallurgical, pyrometallurgical-dry magnetic separation (DMS), and low-temperature fluidised-bed magnetisation roasting (FBMR)-hydrometallurgical and FBMR-DMS flow sheet options powered by renewables have the potential to upgrade Pilbara BID, CID and DID fine iron ores to >65 % Fe and preferably >67% Fe.

The performance of a novel thermally assisted beneficiation process at pilot-scale, combining a drop tube reactor 522 (DTR, flash heating) with wet-high intensity magnetic separation (WHIMS), was reported for a low-grade iron ore 523 powder (initial Fe of 54.8%wt.), together with an in-depth analysis of the impact of flash heating on ore 524 conversion, and associated changes in ore mineralogy and chemical-physical characteristics. The main findings 525 from the experimental investigation are summarized as follows: 526

The proposed process can produce a hematite-rich concentrate with moderate heating at 400–500°C, 527 demonstrating effective ore upgrade performance. Notably, an iron upgrade and recovery of up to 528 60%wt. Fe and >90% respectively was achieved, together with a high specific surface area (SSA) of up to 529 five times the initial SSA value of the untreated ore. 530

Ore conversion, mineralogy, and chemical-physical changes due to heating were significantly impacted by 531 both the heating rate and particle residence time; samples heated under conditions relevant to flash 532 heating in the DTR exhibited different thermal decomposition behaviors to those heated under slow 533 heating rates in a TGA. This resulted in differences in mineralogy and chemical-physical properties of the 534 products, such as the measured SSA values and SSA-conversion trends. Additionally, it was found that the 535 degree of conversion (calcination) was lower in samples heated in the DTR compared to those heated in a 536 TGA.

Benefits to WA

This project will allow iron ores from western Australia to be upgraded more easily and will further allow the use of typical goethite ores in the Pilbara for further processing including pellets and green iron. A follow up project has been approved to look at the application for the current iron ore industry in WA.