Hawsons Iron Ltd (ASX:HIO) has completed another key milestone on the road to bankable feasibility study (BFS) activities and chosen its mineral process flow chart for the Hawsons Iron Project after finalising laboratory test-work on ore samples to verify key equipment sizing, mass balance and final product specifications.
Key equipment requirements were verified using a virtual pilot plant test-work approach, while the economic benefits of a final-stage flotation circuit still need to be evaluated.
The selected process will deliver high-grade concentrate for the ‘green steel’ supply chain.
While the completion of the process flow sheet was delayed, the extra time gave Hawsons the ability to fully consider different equipment technologies, the availability of all required pilot plant equipment and bottlenecks in test processing.
“The selected process will enable the company to produce a high-grade concentrate inclusive of a flotation circuit, however, our technical analysis confirms that we would still be able to produce a premium-grade product without this additional stage of processing,” HIO managing director Bryan Granzien said.
“Consequently, the company will evaluate the beneficial economic value of including the flotation stage against the pricing differentials in the final concentrate specifications we could take to market.”
Cost-effective program
HIO engaged specialists with requisite expertise to deliver a cost-effective, laboratory-based testing program to determine and verify the process flow sheet.
On this point, Granzien said, “Reputable organisations ALS and Bureau Veritas carried out the metallurgical test-work, effectively producing a virtual pilot plant testing regime which enabled us to avoid the capital costs and mine site approval requirements for construction of a physical plant onsite.”
The test-work was completed using laboratory test equipment and included the following:
- Bond Crushing Work index to enable sizing of the primary and secondary crushers.
- High Pressure Grinding Rolls (HPGR) testing to select optimum settings, measure HPGR product size and enable sizing of the HPGR equipment.
- Ball Mill Grindability test-work at different closing screen sizes to enable sizing of the ball mill.
- Dry Cobbing Assessment.
- Grind liberation assessment to enable mass balance calculations at the magnetic separation stages and flotation test work at various final grind sizes to enable prediction of final iron and silica content.
Preliminary results
Preliminary results received from the laboratory test-work confirmed that HPGR technology is suitable for processing Hawsons iron ore.
The first stage of magnetic separation will be optimal at a top size of 1mm with approximately 38% non-magnetic rejection.
Dry Cobbing provided limited benefit and was therefore not incorporated. Due to the fine-grained nature of the ore a final grind size at P80 of 25 microns is required to produce a high-grade magnetite concentrate and achievable through two stages of fine grinding.
Further test-work provided a Crushing Work Index (CWI) and measured Ball Mill Grindability (BMG) as shown below:
Granzien said the process to produce Hawsons Supergrade® had been selected and validated with all major equipment sized.
“Importantly, all this work confirms our ability to produce the necessary high-grade concentrate required to support ‘Green Steel’ production,” he said.