Case Study - Los Bronces
The impacts of operational GEGrade Engineering on mining productivity was assessed by developing detailed Short-Ran GE mine plans for Los Bronces (taking a series of mining benchIndividual levels within an open pit.es within a Short-Range planning timeframe). This section describes the case study and the benefits of doing GEGrade Engineering and GE mine planning and summarises the impacts on equipment productivity identified.
Figure 5-5: benches had different sections of low grade to sub-grade material within an ore bench}
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The case study considered a similar production rate (total rock movement per week) based upon total equipment fleetAvailable equipment at a given operation (e.g. trucks, shovels, water trucks etc…). available. This allows for a value comparison but also provided some insight into the likely impacts on equipment fleetAvailable equipment at a given operation (e.g. trucks, shovels, water trucks etc…).s.
Benefits realised by the GEGrade Engineering mining schedule and approach:
Benefits realised by the GEGrade Engineering mining schedule and approach:
- Some wasteMaterial determined to be below a predetermined grade or economic threshold. blocks became economical and had a new destination which is the leach pad
- Low Grade ore screened and produced some high-grade direct mill feedMaterial entering a predetermined system. ore
- Overall 800kt less ore was sent to the mill (over 15 weeks) but the same metal was produced at the mill as the upgrade of ore from leach to mill and the screening of medium grade blocks (which originally might have been sent to the mill) is now sent to the leach pad
- More wasteMaterial determined to be below a predetermined grade or economic threshold. is produced as sub-grade and low-grade material (oversizeMaterial above a specific size (generally used to define material that is retained on a screen deck).) now reports to the in-pitWithin the confines of an active pit. wasteMaterial determined to be below a predetermined grade or economic threshold. dumps
- Revenue per total rock sent for processing improved which implies revenue to total effort ratio increases within the Short-range planning timeframe
- The GEGrade Engineering process and infrastructure assumed is reasonably simple without significant challenges imposed, particularly on what mining equipment would need to do differently as opposed to a non-GE mining operation (simple screening in the pit at locations near the wasteMaterial determined to be below a predetermined grade or economic threshold. dump and leachpad)
- When the non-GEmine plan mines less total rock it required one less truck but had 45% less value compared to the GE mine plan as the non-GE plan need to produce 800kt more mill ore for the same metal compared to a GE mine plan. The non-GE mine plan also produce less leach pad ore
- At the same total rock production, targeting the same mill metal, the non-GE mine plan needs to produce 800kt more mill ore and less wasteMaterial determined to be below a predetermined grade or economic threshold. rock (at lower grades) and therefore require and additional truck to haul the additional material to the mill/crusher for the same metal when compared to the GE mine plan. This means more mill ore at a lower grade with additional equipment required in this case when compared to the GE mine plan.
- The GE mine plan therefore sends better quality ore to the crusher/mill where the energy and cost is mostly expensed in the process flow and then increase in-pitWithin the confines of an active pit. dumping by early rejection of wasteMaterial determined to be below a predetermined grade or economic threshold. within ore parcels.
Key productivity Impacts:
- For similar total rock profiles less, ore needs to report to the mill for the same metal
- Some additional in-pitWithin the confines of an active pit. activities are required to enable Grade Engineering. These activities had a 7% impact on loading unit productivity by increasing loader movements and therefore increased the loading unit non-productive time.
- truck dispatchSystems for allocation of equipment plans (eg. Trucks, shovels etc…). and truck cycles are impacted as trucks will have to spot and reverse at new screen points. The benefit in this case was less ore had to be trucked to a longer haulageMovement of material from in-pit to ex-pit. destination so reduced truck requirement (for the GE mine plan). It should be noted that when the GE mine plan then increases total rock to still maintain the mill throughputMetric for overall tonnage moving through a system within a specified time. volumes similar to the non-GE mine plan one additional truck is then required for the GE mine plan with the loading units pushed to their maximum capacities. Each mine plan will be different and the overall impact on equipment cycles and productivities needs detailed analyses.
- Improved blockA spatially constrained unit within the resource model. value (in this case) significantly outweighed impact that GEGrade Engineering might have on opex and capex
- The loader productivities reduced but was found to still be within their required capability
- The GE mine plan required one less truck as less material needs to leave the pit (more wasteMaterial determined to be below a predetermined grade or economic threshold. tipped in the pit and more ore to leach pads) with better quality ore to the mill (best of screened material)
- Ore to mill have shown a marked grade improvement and less effort at the mill for the same metal content. The grade dropped at the leach pad, with the GE mine plan, but the overall blockA spatially constrained unit within the resource model. value was still significantly higher
Discussion
The case studies for planning with-and without GEGrade Engineering were valuable as it provided some context to the equipment requirements and allowed the simulation of potential impacts on existing equipment productivities and therefore impacts on equipment fleetAvailable equipment at a given operation (e.g. trucks, shovels, water trucks etc…). requirements. The GE-and non-GE mine plans included equipment simulations, calibrated to account for impacts on equipment cycle rates and therefore overall mine productivityMetrics representing overall perfomance of an operation. .
Based on this case study, the two mine plans were simulated on an equipment and consumables basis with findings depicting the key differences were in the number of trucks required (peak truck fleet required). In this case the GE mine plan required one less truck in most of the periods (weeks) largely due to the reduction in total rock leaving the pit (more in-pitWithin the confines of an active pit. dumping and less crush ore sent to the mill on surface) yet still producing the same mill metal, albeit lower mill tonnage but at better grades.
Generally, most projects might require additional equipment, but the key evaluations should be looking at the overall equipment productivity and the net value/revenue benefit yielded. If one or even two additional trucks are required, then the net economic benefit should significantly outweigh these additional equipment units and the associatedopex and even the refurbishment and replacement capex for these additional units. An important question always asked is if the existing equipment fleetAvailable equipment at a given operation (e.g. trucks, shovels, water trucks etc…). could be utilised better, more efficiently and if the mining activities could be sequenced to utilise the same equipment with a GE mine plan? The early part of the paper outlined the challenges faced by projects, particularly the declining productivities and that generally more Capital is expensed to try and meet the production targets and often new equipment technology is considered to offset the increased equipment and/or labour demand.
By improving grade and therefore being able to produce the same metal by GEGrade Engineering but by sending less ore through the liberation circuitGeneral term for a collection of comminution/flotation equipment. could impact equipment cycle timeTime taken for a single truck to go from shovel/dig face to destination.s and destinations plus rehandling of ore, but if well-planned these impacts on productivities might be managed or offset through smart mine sequencing and destination planning.
The most widely discussed new equipment technology, which may again improve equipment cycle timeTime taken for a single truck to go from shovel/dig face to destination.s (improve equipment and mine productivityMetrics representing overall perfomance of an operation.) and reduce labour requirements, is autonomous equipment technology. It has been proven (on more than one mine site and on several project analyses) that autonomous trucks have better cycle timeTime taken for a single truck to go from shovel/dig face to destination.s when compared to manually operated trucks on a like-for-like comparison. This largely comes into the spotting/sighting and reversing of the truck at key loading/dumping destinations. Also optimising the ramp haul speeds and breaking at strategic times greatly improves the overall truck cycle timeTime taken for a single truck to go from shovel/dig face to destination.. There are some important safety features including auto collision technology which is important as autonomous vehicles, where in-pitWithin the confines of an active pit. services include people in the working areas or in the vicinity of these autonomous vehicles, still require detailed systems and procedures to make sure the collective operations benefit and do not compromise safety.
When considering differential blasting as one of the GEGrade Engineering levers, the impact will likely be on number of drill rigs but also having a live database which enables the accurate modelling of the ore and the heterogeneity of the ore within a blast and to feedMaterial entering a predetermined system. this back so that the appropriate drilling and blasting patternsDifferent blast configurations used within different domains. are considered and the optimal Powder Factors (PF) are used within an ore block. These changes in drilling patterns might impact drill rig movements and number of setups within a shift which ultimately reduces the effective drilling time and therefore the drill meters achieved per shift. The conclusion with these impacts could mean that one or two more drill rigs might be required, but again if the value improvement is justified and the level of data accuracies and turn around times clearly shows the GEGrade Engineering benefits it should be a worthwhile consideration. GE mine planning would generally not rely solely on differential blasting (from experience in these GEGrade Engineering and non-GE mine planning evaluations) and is likely to be part of a combination of GEGrade Engineering levers.
The following impacts were determined for a GE mine plan (this case study) and compared to the non-GE mine plan:
Based on this case study, the two mine plans were simulated on an equipment and consumables basis with findings depicting the key differences were in the number of trucks required (peak truck fleet required). In this case the GE mine plan required one less truck in most of the periods (weeks) largely due to the reduction in total rock leaving the pit (more in-pitWithin the confines of an active pit. dumping and less crush ore sent to the mill on surface) yet still producing the same mill metal, albeit lower mill tonnage but at better grades.
Generally, most projects might require additional equipment, but the key evaluations should be looking at the overall equipment productivity and the net value/revenue benefit yielded. If one or even two additional trucks are required, then the net economic benefit should significantly outweigh these additional equipment units and the associatedopex and even the refurbishment and replacement capex for these additional units. An important question always asked is if the existing equipment fleetAvailable equipment at a given operation (e.g. trucks, shovels, water trucks etc…). could be utilised better, more efficiently and if the mining activities could be sequenced to utilise the same equipment with a GE mine plan? The early part of the paper outlined the challenges faced by projects, particularly the declining productivities and that generally more Capital is expensed to try and meet the production targets and often new equipment technology is considered to offset the increased equipment and/or labour demand.
By improving grade and therefore being able to produce the same metal by GEGrade Engineering but by sending less ore through the liberation circuitGeneral term for a collection of comminution/flotation equipment. could impact equipment cycle timeTime taken for a single truck to go from shovel/dig face to destination.s and destinations plus rehandling of ore, but if well-planned these impacts on productivities might be managed or offset through smart mine sequencing and destination planning.
The most widely discussed new equipment technology, which may again improve equipment cycle timeTime taken for a single truck to go from shovel/dig face to destination.s (improve equipment and mine productivityMetrics representing overall perfomance of an operation.) and reduce labour requirements, is autonomous equipment technology. It has been proven (on more than one mine site and on several project analyses) that autonomous trucks have better cycle timeTime taken for a single truck to go from shovel/dig face to destination.s when compared to manually operated trucks on a like-for-like comparison. This largely comes into the spotting/sighting and reversing of the truck at key loading/dumping destinations. Also optimising the ramp haul speeds and breaking at strategic times greatly improves the overall truck cycle timeTime taken for a single truck to go from shovel/dig face to destination.. There are some important safety features including auto collision technology which is important as autonomous vehicles, where in-pitWithin the confines of an active pit. services include people in the working areas or in the vicinity of these autonomous vehicles, still require detailed systems and procedures to make sure the collective operations benefit and do not compromise safety.
When considering differential blasting as one of the GEGrade Engineering levers, the impact will likely be on number of drill rigs but also having a live database which enables the accurate modelling of the ore and the heterogeneity of the ore within a blast and to feedMaterial entering a predetermined system. this back so that the appropriate drilling and blasting patternsDifferent blast configurations used within different domains. are considered and the optimal Powder Factors (PF) are used within an ore block. These changes in drilling patterns might impact drill rig movements and number of setups within a shift which ultimately reduces the effective drilling time and therefore the drill meters achieved per shift. The conclusion with these impacts could mean that one or two more drill rigs might be required, but again if the value improvement is justified and the level of data accuracies and turn around times clearly shows the GEGrade Engineering benefits it should be a worthwhile consideration. GE mine planning would generally not rely solely on differential blasting (from experience in these GEGrade Engineering and non-GE mine planning evaluations) and is likely to be part of a combination of GEGrade Engineering levers.
The following impacts were determined for a GE mine plan (this case study) and compared to the non-GE mine plan:
- drill rigs – there was not much planned in relation to differential blasting and therefore the drill fleet remained unchanged in this case
- Impact on Equipment – Loading units are required to relocate/position more times along a GEGrade Engineering blockA spatially constrained unit within the resource model. whereas the loading unit would have loaded the blockA spatially constrained unit within the resource model. in basic destination parcels in the non-GE mine plan. These additional shovel movements impacted the loaders/shovels by approximately 7%. The GEGrade Engineering planning and equipment calculations showed that the reduction of 7% on operating/loading time (non-productive loading time) was still within the loading fleet capacity.
- truck fleet – the overall truck cycle timeTime taken for a single truck to go from shovel/dig face to destination. calculated to be within a range of 49 to 52 minutes.
With the GE mine plan (in this case) the additional material sent to wasteMaterial determined to be below a predetermined grade or economic threshold. (in-pitWithin the confines of an active pit.) meant shorter overall truck haulageMovement of material from in-pit to ex-pit.. The mill and the leachpad had screens (for this analysis) and the additional truck cycle timeTime taken for a single truck to go from shovel/dig face to destination. added 3.5 minutes to each truck (compared to if they simply hauled rock to either the wasteMaterial determined to be below a predetermined grade or economic threshold. dump and tipped or the leachpad and tipped). The trucks now have queuing, slowing down to enter the screen area, another spotting/sighting time delay and then tipping and then slow acceleration away from the screening area. These additional truck cycle obstacles added 3.5 minutes to the truck haulageMovement of material from in-pit to ex-pit. cycle. The benefit of GEGrade Engineering (in this case) was that less material had to leave the pit on longer hauls which meant that the average fleet cycle timeTime taken for a single truck to go from shovel/dig face to destination. reduced. The overall saving on haulageMovement of material from in-pit to ex-pit. distance therefore offset the additional cycle timeTime taken for a single truck to go from shovel/dig face to destination. added with the GEGrade Engineering infrastructure and still had significant overall haulageMovement of material from in-pit to ex-pit. cycle timeTime taken for a single truck to go from shovel/dig face to destination. savings. The same logic would not apply to mines where the GEGrade Engineering infrastructure is outside of the pit so in these cases the trucks would all still haul the same total rock, possible more rock so that the mill maintains its feedMaterial entering a predetermined system. rate post GEGrade Engineering and this might indicate additional trucks or even loading units required. If the grade to the mill is increased by margins as low as 5% in medium to large open pit operations, it could likely justify additional equipment required to consider GE.