COMMINUTION
bespoke solution , the Gold Fields team chose to go with a Sandvik modular plant .
Gold Fields Manager – Processing , Tristan Freemantle , explained : “ We needed a circuit that was simple , low maintenance and reliable , but also wanted the best crushers and screens that we could get . Sandvik showed a willingness to work with us within our parameters . Initially , it was just the crushers and screens , but in the end , they presented a complete plant design , which was modular and comparable with the bespoke designs that we were considering .
“ Sandvik was also able to accommodate our desire to manage our own electrical and process control design .”
A key to the successful implementation was Sandvik ’ s expertise in crushing and modular plant design combined with the screening knowhow of Schenck Process ( now part of Sandvik Rock Processing Solutions ).
The scope of supply included a Sandvik reciprocating plate feeder , grizzly screen , jaw crusher and two cone crushers , as well as a Schenck Process double-deck banana screen fitted with Screenex screening media . Sandvik also provided bins , chute work , associated wear protection and conveyors .
The plant design eliminated the need for two screening stations and associated conveyors when compared with other proposed designs , according to the OEM .
A significant challenge for the project team was that Gold Fields needed the new plant to be installed in parallel with the old one so that , ideally , there would be zero downtime .
“ Agnew can ’ t afford to be down for two or three weeks ,” Radford said . “ The mill is pushed to its limits , so it has little ability to catch up . Solving this problem – where we could build the new circuit and how to tie it in – was a good part of the success story . Commissioning on time and within budget , with limited downtime , was a very important part of the brief .”
To accommodate this requirement , the team decided to move the run-of-mine ( ROM ) pad and build the new circuit on the site of the old ROM pad . While this achieved the brief of zero downtime , it introduced a new challenge : the geology of the ROM pad was untested , and some contractors argued that a substantial concrete foundation would be required to support the crushing and screening plant , greatly increasing both the build time and cost .
In the end , working with Gold Fields Geotech consultants , Sandvik ’ s design team resolved this by delivering a support structure for the new circuit that was strong and rigid enough to reduce the concrete foundations required .
The new crushing and screening plant has been running for more than 12 months and the Gold Fields team is very happy with its performance , with Freemantle saying the Schenck screen has been performing well , while the Sandvik crushers ’ automation system has proven easy to integrate into the process control system the site uses .
The new plant was designed for a 2 Mt / y throughput , which is oversized for the current throughput of 1.3 Mt / y .
“ This means the crushers can be run tighter , producing smaller product ,” Freemantle said . “ During the design stage , the crusher output was set at 8 mm , but it is now regularly producing less than 6.5 mm . The finer feed has improved downstream mill performance , increasing the maximum throughput rate from 155 t / h to 170 t / h .”
A comminution crushing and grinding survey completed in October 2023 indicated the new circuit is around 18 % more energy-efficient than the previous one , according to a survey from Gold Fields .
“ Also , we were able to centralise the control room duties , where we now have one operator in one control room , and the crushers run pretty much automatically with extensive CCTV around the circuit ,” Freemantle added . “ Previously , the crushers had their own control room , and the operator relied heavily on visual line of site monitoring .”
Safety has also improved considerably with the simpler design , modern instrumentation and improved automation , while the design of the new circuit has reduced dust generation and improved water drainage around the plant , according to Radford .
“ The new circuit has fewer conveyors and transfer chutes , and improved water sprays and belt scrapers ,” he said . “ We aimed to improve housekeeping and access to make things easier for our maintenance and operations staff . Comparing the two plants is like comparing chalk and cheese .”
Including a fine ore bin tied into the main mill feed conveyor reduced dust emissions , reduced freshwater consumption from sprinklers and improved site drainage through an improved plant layout , Sandvik added .
The new modular crushing and screening
In the solution Metso is supplying for the Reko Diq project , the feed particle size capability of the Vertimill will be combined with the fine grinding and particle conditioning of the HIGmill to create a complementary solution , Christoph Hoetzel says
circuit has delivered minimum annual savings of A $ 1.5 million ($ 922,030 ) by increasing throughput at a reduced crushed product size , improving downstream efficiencies and introducing a fully centralised control room , which has eliminated the need for a permanent second crusher control process technician . Combined with capital savings , this led to a three-year payback period .
The Gold Fields team feels that the teamwork between all those involved has greatly contributed to the success of the project , as Radford indicated .
“ Sandvik ’ s ability to work with multiple teams was a highlight , delivering a project to spec , and always listening ,” he said . “ The Sandvik team really pushed themselves to deliver the project and helped us achieve what we needed despite the challenges – many of which were out of their control .”
Metso and application-specific solutions
The continued expansion of Metso ’ s comminution offering – both hardware and software – is allowing the company to serve clients in a new way , looking at the specific application and finding a suitable solution as opposed to just pushing available products , Christoph Hoetzel , SVP Grinding , says .
“ Our focus always has to be on the application and looking holistically from this point ,” he told IM . “ It ’ s no longer about saying to the customer , ‘ Your problem is a nail , because I happen to have a great hammer .’
“ To remain competitive in this sector , we need to look across the field of solutions on offer and collaborate with the client to examine the application and the specifics that need to be addressed with a solution .”
For Metso , this could be looking outside of the standard semi-autogenous ball mill crusher circuit to flowsheets involving vertical grinding
12 International Mining | MARCH 2025