Toka Tindung

Project Category: Optimisation & Expansion
Client: Pt Meares Soputan Mining
Location: Northern Sulawesi, Indonesia
Capacity: 1.7 - 3.0 Mt/a
Commodity: Gold

Scope of Work

Orway’s scope of work was to audit the performance of the plant including a grinding circuit survey and optimising gold production with the existing equipment.  Then, using the obtained baseline data, model the expansion of the circuit to 3.0 Mt/a.

Flowsheet

The flowsheet comprised a primary gyratory crusher (42-65) followed by a SAG mill (4.1MW, ø 8.54 x 3.18m EGL) with recycle crushing and closed circuit with a 3 mm screen.  The -3 mm product feed and ball mill (2.6MW, ø 4.72 m x 7.32 m EGL). The ball mill operated in closed circuit with a dedicated cluster of cyclones.

Notable Feature

The SAG mill was not operating to load and was unstable with the motor power underutilised. The circuit was ball mill limited at the target grind, constrained by the cyclone control.  Analysis of the CIL circuit showed that the ore was much less grind sensitive than assumed.

An updated process control strategy was implemented to stabilise and run the SAG mill to weight.  Changes were also made to the cyclone control to improve stability and allow a slight increase in grind size.  The SAG mill ball addition was changed to a blend and the charge level increased. 

Analysis indicated that the SAG mill would not be the constraint up to 3 Mt/a when optimised.  The proposed most cost-efficient expansion option was to add a tertiary grinding stage to maintain the grind in combination with new leach tanks.

Outcome

These optimised changes combined, resulted in a 38% increase in throughput for a 14 micron increase in grind size, significantly improving the project economics without any capital expenditure. 

Later the proposed expansion option was successfully implemented, increasing the plant capacity to the target 3 Mt/a.