WORLD PROSPECTS
Rio trialling automated Scania trucks at Channar
There were some interesting comments from Rio Tinto recently in an article focussing on its transition to renewable transport in the Pilbara , specifically with regard to what is the right size haul truck for its operations – and that bigger is not always better for some applications , plus offering more electrification wins at an earlier stage .
The global miner stated : “ Across the mining industry , there ’ s been a long-held view that ‘ bigger is better ’. Enormous haul trucks provide economies of scale , allowing operations to move more material more quickly by leveraging the large trucks ’ power and carrying capacity . But we ’ re challenging our thinking on size and why size matters . Larger haul trucks , while already automated , consume more energy than current electric-vehicle power sources can generate . By exploring truck size , we want to assess how big and small trucks can both be a part of the solution to reduce our emissions in the Pilbara and find fit-for-purpose solutions in mining .” At its Channar iron ore mine in the East
Pilbara , Rio Tinto is now working with Scania to
The ability to leach primary copper sulphides has , on many occasions , proved a hurdle too much , with conceptual work in the laboratory or pilot scale falling down on subeconomic or volatile recovery rates when working out in the field .
This problem tends to result in one of two things : new capital-intensive concentrators are brought into process these sulphides , or brownfield oxide operations are drafted up that prolong existing leaching operations for a few more years when – hopefully – copper prices are higher .
Antofagasta has come up with an alternative option that leverages chloride-based reagents and 20-years of knowledge leaching secondary sulphides . Called Cuprochlor ® -T, the proprietary process has undergone five years of intense development leading to the point that the company is now open to talking about its potential . It leverages off the first iteration of leaching technology Antofagasta devised for secondary sulphides – Cuprochlor .
Cuprochlor , which is now working at the Michilla mine in Chile ( which Antofagasta sold in 2016 ), effectively binds together the particles of mineral – particularly fine in the case of Michilla – into a porous but manageable material that can then be heap leached . The agglomeration is achieved by mixing the mineral and leach solution with chloride salts and sulphuric acid , which react to form a plaster-like paste . Over the years , the trial smaller automated trucks that could more readily be electrified to reduce its carbon emissions , and could improve its zero emissions speed to market . The project builds on experience gained with autonomous Scania trucks dating back to 2018 at Rio Tinto ’ s Dampier Salt operation . Both projects involve the 40 t class Scania XT 8 4 model , with the XT trucks specifically aimed at tough construction and mining applications . The trials have also offered an opportunity to use a more open autonomy approach , where the AHS rollout does not restrict the operator to a particular truck OEM or fleet management system ; and on this Rio Tinto has been working closely with Wenco International Mining Systems .
These trucks could also reduce emissions and costs while improving mining practices across site infrastructure and operations . “ Smaller trucks can operate on narrower roads , allowing us to cut steeper pit walls and reduce vegetation disturbance . This reduces the amount of earth we need to move to access the ore , which means the smaller trucks don ’ t just produce lower or no
process has been refined , going on to consistently deliver recovery rates of around 90 %.
Sitting on an expansive base of primary sulphide resources – mainly chalcopyrite – and the success of Cuprochlor , Antofagasta , around five years ago , began a series of tests , adjusting variables such as temperature , reagent concentrations and particle size to see if the chloride leaching process could be adapted for the treatment of primary sulphides .
Temperature proved to be one of the keys , with tests showing that by elevating the temperature of the heap to around 30 ° C , Cuprochlor-T was able to stimulate the required chemical reaction for recovering copper from primary sulphides such as chalcopyrite . Another key differentiator between the two chloride leaching technologies is the “ reagent recipe ” and particle size distribution ( PSD ), Alan Muchnik , VP Strategy & Innovation for Antofagasta , told IM .
“ Providing a constant temperature throughout emissions – they also help reduce our overall energy usage while we ’ re constructing and operating our sites .”
Of course payload is king and Rio Tinto is also exploring options to further reduce emissions of larger trucks through its partnerships with Komatsu and Caterpillar . “ Working with Komatsu , we will pilot a fleet of their future 220 t + zero emissions autonomous haul trucks in the Pilbara . We ’ re also working with Caterpillar to advance development of their future 220 t + zeroemission autonomous haul truck , which we ’ re exploring the possibility of deploying at our Gudai-Darri smart mine .” www . riotinto . com ; www . scania . com
Antofagasta readies primary sulphide leaching options
the process is very important , but the real innovation is the approach we have used ,” he said . “ It involves a combination of factors , including , among others , the recipe for reagent concentrations and the required PSD .”
While not wanting to reveal the ‘ secret sauce ’, Muchnik said the PSD consideration goes beyond the usual P80 industry reference point . It is this balance that has landed the company with recoveries of over 70 % after approximately 200 days of leaching on the heap in test work .
Muchnik expanded on this : “ The Cuprochlor-T process , in simple terms , involves leaching in a chloride environment – where there are no passivation layer bonds . This allows for the copper , iron and chloride ions to react , which , at a controlled temperature , results in the economic production of copper .”
This is through three stages . First up is an agglomeration stage where the necessary reagents are added and are left to rest at a constant aeration and temperature . Second , the ore is irrigated intermittently with continued aeration , also maintained at a constant temperature . Finally , after 200 days , the ore completes the leaching cycle and allows the company to obtain recoveries of 70 % copper or more .
What started with laboratory testing and progressed to pilot testing and a “ semi-industrial ” test on several different heaps at Centinela has recently concluded with an industrial test of over
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4 International Mining | AUGUST 2022