The Bald Hill project is located 50km southeast of Kambalda, Western Australia. The project originated as a tantalum mine operated by Haddington Resources Ltd at design rates of 200kt/y ore and 145,000lb/y tantalite concentrate from 2001 to 2005. During this period, 1.35Mt of ore was processed and 820,000lb of tantalite concentrate was produced. The mine ceased operation in 2005.
In 2015 the tantalite processing plant was recommissioned under ownership of Alliance Mineral Assets Ltd (AMAL). In 2016, Tawana Resources NL acquired a 50% interest in the project with an aim to discover and produce lithium spodumene concentrate in joint venture with AMAL.
Project implementation included development of an open pit spodumene ore mine, a dense medium separation (DMS) spodumene processing plant, tailings dam, waste rock dump, water infrastructure, non-process infrastructure, and a camp. Project implementation commenced in August 2017 and first concentrate was produced in March 2018, seven months after completion of the feasibility study and maiden reserve announcement.
Primero was engaged by the Tawana Resources and Alliance Mineral Assets Limited joint venture (JV) to complete the design, procurement, construction and operation of the DMS circuit at Bald Hill.
Priorities for the JV were to gain first mover advantage over their peers and capitalize on heightened demand for spodumene concentrate by fast-tracking the project’s development. Primero was able to deliver on promise in meeting the challenging schedule, reaching practical completion and first concentrate production in March 2018 – just seven months from feasibility study and first ore reserve to completion of commissioning.
Two weeks after the production of first concentrate, Primero’s Operation & Maintenance team exceeded the nameplate production capacity of the plant and achieved an unprecedented 7% spodumene concentration. The initial results were achieved with low grade commissioning ore.
The Bald Hill lithium processing plant is designed to process 1.2Mt/y of spodumene ore at grades of up to 1.41% Li2O at a nominal throughput of 161 t/h and 85% annualised plant utilisation. At head grades of 1.41% the plant is designed to achieve an overall mass yield of 13.9% of plant feed and to achieve a product grade exceeding 6% Li2O spodumene concentrate 6% (SC6.0) at a rate of up to 167kt/y.
To benchmark mineral processing plant ramp-up success, McNulty suggests use of empirical ramp-up curves based on 81 actual process plant ramp-up profiles (throughput basis) to serve as a guide for plant ramp-up expectations (McNulty, 2014). Figure 4 outlines the six standard McNulty curves (dashed) and compares those curves to the Bald Hill ramp-up curve (solid) on a throughput basis.
The Bald Hill processing plant exceeded the McNulty 1A best in class ramp-up profile placing the operation in a class of its own for rapid ramp-up above nameplate. It is therefore a case study in ramp-up excellence where McNulty’s common contributors to reduced ramp-up performance (Series 2-5) (McNulty, 2014) (McNulty, 2004) were absent.
The Bald Hill lithium processing plant performed largely in line with pre-production forecast from start-up. The plant met or exceeded product grade requirements within the first month of operation, while the mass yield and concentrate production was aligned with feed grade. The demonstrated sustainable rate was above design capacity while also achieving the forecasted availability. The plant ultimately achieved 160% of design capacity by month twelve. The operation also performed admirably on safety measures with zero recordable injuries across all injury classifications.