ORE SORTING
The second sensor – for particle size distribution – could also have an impact on the mineral processing side of the business , with the data translated to optimise the downstream crushing and grinding circuit .
Initially being lined up as an addition to the company ’ s ShovelSense system later this year , More said there was potential for these two new sensors to also be incorporated in future BeltSense installations .
Finishing with a question on the company ’ s 2021 aims , More revealed that the company was expecting to have commercial ShovelSense or BeltSense systems at eight mines by the end of the year .
“ That would mean over 15 systems in the field , roughly speaking ,” he said . “ I ’ m hopeful we can beat that .”
Heterogeneity realities
IMA Engineering is making its own bulk ore sorting assessments as early as the exploration stage .
With sophisticated XRF analysis of drill core at its disposal , the company can potentially start to provide advice on whether the orebody is suited to bulk ore sorting before any process flowsheet is locked in .
This is particularly useful in greenfield projects where there is no option to stick a sensor above a conveyor belt to assess the inherent heterogeneity after initial crushing .
Such analysis is combined with pilot crushing and pilot bulk ore sorting tests in a lab environment to assess detection limits and gain confidence in what a commercial solution could offer . Follow-on trial mining scenarios can be conducted to test and re-assert these initial findings .
One of the companies to have benefitted from this type of XRF analysis is Sotkamo Silver , which has a silver operation in central Finland . Early analysis of the company ’ s drill core in 2014 , using the OSSCORE solution , outlined a potential increase in ore reserves with the use of ore sorting in the process flowsheet .
IMA Engineering ’ s latest pilot project has seen it trial the use of XRF sensors in the pit and underground with its IMA XRF-Bucket Scanner
Ilpo Auranen , Chairman of IMA , said the company has also worked with Outokumpu ’ s Kemi chromite mine in Finland on a similar study as part of an Oulu Mining School-backed study . This saw about 1,500 m of drill core analysed .
The study has not yet led to a confirmed ore sorter order , but it has highlighted the Kemi orebody ’ s heterogeneity , according to Auranen .
“ The study identified a big variation in ore and waste ,” he told IM . “ We anticipated a big grade variation , but the reality was even bigger .
“ This is pretty much what we have seen in all ore studies we have done to this point .”
The company is currently engaged in several bulk ore sorting system ( BOSS ) projects in Africa ( South Africa ) and South America ( Chile and Brazil ), with capacities ranging from 500-8,000 t / h and average grade reporting every 10 to 30 seconds , Auranen said .
Most of these brownfield installations were commissioned remotely during the COVID-19 pandemic in 2020 .
“ Further , we are working with several Fast Conveyor Analyser ( FCA )/ BOSS sensing projects in the same regions ,” Auranen said .
IMA ’ s online FCA is used to sense coarse primary crushed and / or fine crushed ore before it enters the grinding mills and concentrator . Its BOSS technology , meanwhile , sorts ore and waste rock and / or different grades of ore by analysing the mill feed on primary crushed ore conveyors in short time batches .
The company says it recently found the FCA belt analyser to be feasible for optimising preconcentration in concert with dense media separation ( DMS ). This was witnessed during a trial in Africa where the FCA was able to analyse the DMS system ’ s feed , sinks and floats on conveyor belts . In mineral sands applications , FCA online analysis has also been found to shorten the ramp-up time in concentrator start-ups , according to Auranen .
On top of this , IMA is looking into sensorfusion ore sorting solutions where two or several sensors could be used in combination .
The layout of the bulk ore sorting plant at a PGE mine site trial installation the Cooperative Research Centre for Optimising Resource Extraction ( CRC ORE ) was involved in . This setup saw a Caterpillar 992 wheel loader drop material off to a system using a combination of grizzly , feeder , sizer , conveyors , diverter , stackers and associated equipment from MMD , used in conjunction with an ore sensing system equipped with both PGNAA and XRF sensors to continuously measure the elemental composition . The PGNAA sensor provided a “ penetrative ” analysis calculation whereas XRF provided a “ surface ” sensing calculation , CRC ORE ’ s Principal Geologist , Jon Rutter , told the IPCC Virtual event crowd in early February
“ In some cases , adding laser induced fluorescence and infrared and spectral mineral analysis methods to the main XRF method could help improve the accuracy of ore and waste rock sorting ,” Auranen explained .
The company got even closer to the mining face – where heterogeneity is highest – with its latest pilot project where it has trialled the use of XRF sensors in the pit and underground with its IMA XRF-Bucket Scanner .
This sees a sensor solution positioned at a specific place in the pit or underground where LHDs and wheel loaders can check the grades of their bucket loads by positioning said bucket underneath the sensor .
Piloted at a mine in Finland , Auranen said an XRF analyser was positioned in a protected environment on the tunnel ceiling . Not only were operators able to know the average grade of the material in the bucket – through an in-cab display – supervisors and mine management could also associate the grade with the machine ’ s location data .
“ You will know the source and destination when the system is employed alongside a location device ,” Auranen explained . “ This could enable you to know when you hit the ore-waste boundary , allowing you to amend your operations accordingly .”
He added : “ We also had a wired alarm on mobile phones to indicate when the mined grade went below a certain level . This ensured they didn ’ t take ore to the waste section and viceversa .”
54 International Mining | MARCH 2021