COMMINUTION AND CRUSHING
“ This allows higher grinding pressures to be applied to produce a finer product and enables faster roll rotation speeds for higher throughput ,” he said .
Another advantage of using oil is that it helps to remove abrasive impurities from the lubrication fluid .
The rating life factor is a rough indicator of the service life of bearings , with oil lubrication enabling the rating life factor to be doubled , according to Schroers .
Mackert added : “ The HPGR Pro concept allows operators to choose between single- and multiple-use wear-protection tyres to guarantee the most economical application at any one time .”
“ Single-use tyres are thinner , significantly lighter than returnable versions and disposed of after one use . They are a sensible solution if the workshop capacities required for multiple-use tyres are not available close to the HPGR installation .
“ Multiple-use tyres are thicker and more expensive but can be reused multiple times with an increasingly thinner diameter , or reprocessed to a new diameter through re-weldings on the worn surface .”
These innovations mean the new-generation thyssenkrupp HPGR Pro can take grinding to a higher performance level , according to Mackert , who highlighted up to 20 % more throughput , even better product quality , lower production costs , longer-lasting rolls and higher machine availability .
“ Put succinctly , the HPGR Pro is designed to enable optimised output at the optimum operating point ,” Mackert summarised .
This is even before considering the HPGR ’ s CO 2 emission reduction benefits .
Remmers explained : “ Up to now , a reduced carbon footprint was mainly perceived due to the fact that HPGRs are more energy-efficient than SABC circuits – and lower energy consumption naturally means fewer CO 2 emissions .
“ However , another advantage of the HPGR Pro is that it enables a significant reduction in equivalent CO 2 emissions as a result of the elimination of the embodied energy linked to grinding media and steel liner consumption in SAG mills .”
The specific energy in SAG mills can vary between 4 kWh / t and 12 kWh / t in gold or copper plants , which means around 50 % fluctuations in throughput , according to Remmers . The specific energy for tertiary crushing with HPGRs , however , is only around 2.6 kWh / t and does not typically vary by more than around 0.3 kWh / t in similar applications .
Like Weir ’ s Lundquist , Mackert sees a larger variety of HPGR flowsheets in the future . “ Beside the classical HPGR / ball mill flowsheets , HPGR finish grinding circuits without the use of ball mills – in dry grinding as well as wet grinding – are expected ,” he said . “ Furthermore , the combination of HPGRs and vertical mills could be seen in the main material stream in addition to being used without ball mills .”
Speaking of vertical mills , thyssenkrupp Mining Technologies recently received its first order for four of its velix ® vertical-helix stirred media mills for a large iron ore project in Uzbekistan . velix is an efficient solution for the fine grinding stage in the main material stream of large concentrators , according to Stephan Vilbusch , Product Manager for velix , explaining that the mills consume up to 50 % less energy than a conventional solution with a ball mill . velix is the result of a long cooperation agreement with Germany-based Eirich , combining Eirich ’ s many years of expertise in vertical milling with the TowerMill and thyssenkrupp ’ s expertise on large and innovative comminution equipment , Vilbusch mentioned .
“ Eirich products range up to their ETM 2000 HP , while our product range covers velix 3500 , 4500 and 6000 ,” he said .
Vertical considerations
As the focus has shifted towards more energyefficient flowsheets , the discussion around the use of vertical mills continues to grow .
Swiss Tower Mills Minerals was founded in 2011 to introduce the fine grinding technology of industrial minerals to the mining industry . Today , it has more than 200 grinding mills operating in the industrial minerals sector with , it says , truly minimised energy requirements . At the same time , over 30 units are currently operating ( and more than 70 units have been sold ) in the hardrock processing industry .
The company was recently awarded an order for the delivery of four energy-efficient VRM50000-6500 grinding mills for a large greenfield copper project in Russia . This came on top of an order for one VPM10 vertical stirred grinding mill for the Navachab gold mine plant expansion in Namibia .
The scope of the Russia project , awarded in the June quarter of 2021 with expected deliveries in 2022 and 2023 , included the design , manufacturing and delivery of four Vertical Regrind Mills ( VRM ), each complete with a 6,500- kW variable speed drive package and control system .
Each regrind circuit will process up to 500 t / h of flotation concentrate , Maarten van de Vijfeijken , Sales Manager at Swiss Tower Mills said , explaining that they would be “ by far ” the largest and most powerful stirred mills in the world .
Cobre Panama engaged Schenck Process to deliver multi-slope banana screens as part of plans to increase throughput at the mine to 100 Mt / y , from 85 Mt / y . The screens recently left Western Australia on their way to Panama
In Namibia , meanwhile , STM ’ s scope includes the design and delivery of one VPM10 vertical stirred mill using ceramic grinding media , complete with control system and 1,600-kW drive system . The duty of the VPM mill is to grind 140 t / h of gold concentrate from 2 mm to a P70 of 75 μm .
Expected to start up later this year , the mill will provide several advantages such as a low specific grinding energy value combined with high power intensity , simple flowsheet with no recirculating loads , and flexibility in process variables , the company said .
Sustainable screening
As more companies consider the use of dry or energy-efficient comminution circuits , the importance of screening solutions that can handle the varied grinding outputs will grow .
Last year , Schenck Process said it achieved a major mining milestone in the Americas with the installation of a newly developed elliptical motion screen capable of handling fluctuations in material properties . This screen , it said , outperformed competitors ’ efficacy by up to 50 %.
The Americas mining market has proven fruitful for the company in recent years , with the largest banana scalping screens ever built set for the First Quantum-owned Cobre Panama operation in the region .
Over the last few years , the operation has commissioned some of the largest mineral processing equipment ever built for the operation , and the Schenck Process banana screens are no different .
Cobre Panama engaged the vibrating
34 International Mining | APRIL 2022