COMMINUTION AND CRUSHING
released and are making double the wear life a new reality ,” he said .
Both Metso Outotec and FLSmidth also use a rotable top shell concept to speed up the relining of primary gyratory crusher shells and improve machine uptime by cutting maintenance time .
Enrnst Bekker , Product Specialist at Multotec , says his company has invested in simulation packages to help design the most effective mill liners . These tools incorporate particle size distribution to determine the best design to maximise energy transfer inside a mill .
“ Earlier packages only considered ball trajectories inside the mill and , although still used , the incorporation of particle size distribution allows for a more exact prediction to maximise the mill performance under higher throughput demands ,” Bekker said .
He said the evaluation of specialised designs based on specific process requirements are an ongoing process , with Multotec ’ s custom-made mill liners aiming to achieve the balance between liner life , cost , grind efficiency and the structural integrity of the liner by considering the complete grinding circuit and process parameters .
The trade-off
Most vendors in this space are having to walk this throughput , power and availability tightrope while carrying an expectation of being able to lower mining companies ’ carbon footprint and greenhouse gas emissions .
This task is , however , not only in line with mining companies own sustainability targets ; it also speaks to the OEM ’ s own ‘ green ’ goals .
Metso Outotec ’ s Christoph Hoetzel says the company ’ s customers should not have to choose between sustainability and total cost of ownership with its mineral processing equipment .
“ Within the comminution area , our motto is to combine the best of both worlds and to not trade off sustainability against low cost of ownership , but to combine both ,” he said .
“ The combination of the previous companies ( Metso and Outotec ) now enables us to extend our systems capabilities , looking into processisland solutions that are modularised , balance the equipment and minimise the overall
Through the VAES ( Value-Added Engineering Services ) program , ME Elecmetal says it helps customers optimise processes , extend the lifespan of wear parts , reduce operational risks and increase profitability .
In 2018 , a Chilean copper mine customer and ME Elecmetal jointly identified an improvement opportunity on a 36 ft ( 11 m ) x 19 ft ( 5.8 m ) SAG mill discharge head – specifically in the 73 mm slotted grates and semi-grates . The customer ’ s objective was to increase the slot opening to process greater tonnage .
A few conceptual designs for different slot sizes for the grates and semi-grates were presented to key stakeholders at the mine site to define some parameters .
ME Elecmetal ’ s basic proposal introduced different slot sizes ( 78 mm and 80 mm ) to quantify how many more tonnes per hour could be processed and what impact it could potentially have on downstream lines , such as pre-crushing , while also sharing a national benchmark on slot sizes .
The project objectives included boosting throughput , reducing peening and maintaining reliability and availability so the design change did not disrupt operations .
ME Elecmetal ’ s technical department developed and presented two proposals to the mine stakeholders to help them reach a decision on the optimal design for their operations . Proposal A was a 78 mm slotted grate and semi-grate design , with Proposal B being an 80 mm slotted grate and semi-grate design . Proposal A increased the free area by 7.4 % and lowered the total weight by 1 %, compared with the mine ’ s current design , while Proposal B increased the free area by 8.1 % and lowered the total weight by 1.2 %.
Having moved forward with Proposal A , the ME Elecmetal team worked on upgrading the design on the 78 mm grates and semi-grates with builtin lifters . This consisted of vulcanising the areas where pieces were spliced to prevent plastic deformation , thereby shortening torching times during major maintenance work .
The results were impressive , ME Elecmetal said , with the 78 mm slot size SAG mill generating an 11.1 % tonnes per hour throughput improvement when compared with the previous 73 mm slot size design . This was mainly due to two factors : the hardness of the ore being fed and the size of the 78 mm slots , which resulted in a shorter residence time of the load and greater ore treatment .
The 78 mm slotted grates and semi-grates came with a longer wear life by 6.4 months , without causing issues for the operational continuity of SAG mill , the company said .
The anti-peening design was successful since no clogging was observed in the grates or semi-grates during the two intermediate early
The details of the two proposals put forward by ME Elecmetal
alert analyses , ME Elecmetal said .
A second set of 78 mm grates and semi-grates have since been installed in the SAG mill , both of which are currently in operation . According to early projections , the parts should reach the end of their service life at about six months .
“ ME Elecmetal is currently the sole supplier of 73 mm and 78 mm slotted grates and semi-grates for the SAG mills at the mine site ,” it said . “ As an operational strategy , the mine managers have decided to maintain 78 mm slotted grates and semi-grates in the SAG mill .”
18 International Mining | APRIL 2021