leinster nickel mine

Project Category: Optimisation
Location: Western Australia
Capacity: 3.0 Mtpa
Commodity: Nickel

Scope of Work

Orway’s scope of work was to assist with optimisation of the grinding circuit to ensure maximum throughput was being achieved through the existing plant.

Flowsheet

The flowsheet comprise a primary jaw crusher (Jaques Terex 6048H, 150kW) followed by a single stage SAG mill (7MW, ø 9.60 x 4.86m EGL) without recycle crushing. The SAG cyclone underflow stream reports to flash flotation before returning to the SAG mill feed. An additional ball mill (1.65MW, ø 4.57 x 4.75m EGL) installed alongside the SAG circuit receives feed from a portion of the flash flotation tails which is bled across to the ball mill discharge hopper. The ball mill operates in closed circuit with a dedicated cluster of cyclones.

Notable Feature

The SAG mill was operating with minimal automated control making it difficult for operators to stabilise the circuit.  The instability in turn made diagnosis of the main circuit constraints difficult.  Throughput varied significantly over a set of liners.

Outcome

An updated process control strategy was implemented to stabilise the cyclone pressure and SAG mill weight.  With the new control loops running, the circuit stability improved.  By removing the operating noise, the performance of the SAG mill grate design was identified as potential constraint.

Changing the SAG grate design to utilise a combination rubber and hardox segments resulted in 15% increase in plant throughput whilst maintaining the cyclone overflow product size and significant improvements in both throughput and grinding efficiency.  This further stabilised the circuit performance over the life of a set of liners with very consistent performance across the whole life.