SGS Bateman’s scope of work at the project will ensure the plant maintains its 12 Mtpa capacity – comprising 2 Mtpa from the existing ROM1 feed to the plant, plus an additional 10 Mtpa from the ROM2 and ROM3 feeds.
The modification will enable the plant to treat harder transitional and primary ore which could not have been processed optimally with the old plant, project manager Bradley van der Merwe tells Laura Cornish.
The mine plan sees the Siguiri mine progressing deeper into the current open pit in order to access transitional and primary ore from the first quarter of 2018 as the currently-mined soft oxide material depletes, Van der Merwe states.
Maintaining existing throughput and recoveries after the mine transitions to the harder ore requires some major modifications to the existing process plant.
Having undertaken the pre-feasibility study in 2014 and the feasibility study in 2015, SGS Bateman moved into project execution early in 2016. SGS Bateman spent the last year completing detailed engineering and design as well as procuring long lead items.
“We have travelled a long road with AngloGold Ashanti and built up and maintained a healthy relationship with the client over the years which stand us in good stead as we move the project into full construction execution,” Van der Merwe states.
The ROM1 and ROM2 feeds are soft oxide ore, while the ROM3 feed is hard transitional and primary ore. Currently the plant is processing 12 Mtpa of primary crushed oxide ore through a 2.5 MW scrubber and double deck screen to remove clay, followed by a 6 MW ball mill in reverse closed circuit with a cyclone cluster.
In future the plant will process 12 Mtpa of a 50:50 soft:hard blend. The hard ore requires three stage crushing and increased comminution power. Another requirement is to minimise “preg-robbing” by converting existing leach tanks to carbon-in-leach (CIL). This will involve moving the existing trash screens from carbon-in-pulp (CIP) to CIL.
[quote]Although the total tonnage to the plant will remain unchanged, most of the operations will be affected.
The project includes the installation of new primary, secondary and tertiary crushers, an additional ball mill in closed circuit with cyclones and conversion of the leach to carbon-in-leach (CIL).
Additional mill process water pumps, gravity circuit water pumps, gland service pumps and reagent pumps will be installed. There are also infrastructure upgrades to the electrical supply grid and a 120-man construction camp.
The existing ROM1 primary crusher will operate at reduced throughput and the scats circuit will be re-designed to return crushed scats to either ball mill.
The new mill will have a similar gravity circuit (Knelson Concentrators and Gekko ILR) to the existing circuit. The existing carbon-in-pulp (CIP) circuit will be unchanged to create a hybrid CIL/CIP circuit. A new tower crane will be required to service CIL.
The existing AARL elution process will be converted to the AARL split elution process. This increases the elution plant capacity in order to separately elute CIL carbon and CIP carbon.
An additional 35 MW HFO power plant is also being installed by AngloGold Ashanti to handle the requirements of the new plant, Van der Merwe notes.
The project is on track to start mobilising construction people to site for the main civil works in May this year after which the full-scale build will commence. The new plant is due for completion and cold commissioning towards the middle of 2018.
“Not only does the Siguiri project demonstrate our strong technical skills and capabilities but also showcases our West Africa work experience. This includes recent work on an iron ore project in Sierra Leone. As a result of the incorporation of Bateman into SGS minerals, we will be able to leverage SGS’s supplementary skills and local footprint in Guinea. The local analysis and test work business will continue to support the Siguiri project team with global equipment inspections as required,” Van der Merwe notes.
“We are proud of our relationship with AngloGold Ashanti, which also extends to other project studies we’ve undertaken for the company across the African continent stretching from West Africa to Central and Southern Africa as well. We hope this continues into the future,” Van der Merwe concludes.
All images courtesy of SGS Bateman
Feature image: A digital rendering of AngloGold Ashanti’s Siguiri Combination Project in Guinea.