Process Energy Optimisation on Fully Autogenous Mills René Coetzee Southern African Energy Efficiency Convention 12 November 2015
AGENDA 1 2 3 4 5 6 7 Palabora Mining Company (PMC) Ensight Energy Solutions - Energy Leadership Program (ELP) FAG Mill Operations at PMC Process Energy Optimisation Project MineralScan MillSlicer Project Performance Summary Q&A
Palabora Mining Company is South Africa s only producer of refined copper Located in town of Phalaborwa, Limpopo Province. Bordering Kruger National Park sharing environment with Big Five Game roaming freely on mine. Started-off as open-pit operation in 1965. Transitioned into an integrated underground copper mining, concentrating, smelting & refining complex. Producing ~60,000 tonnes per year. R9.3-billion development project (Lift II) 2015 to 2033. PMC partnered with Ensight in 2012 Energy Leadership Program (ELP)
ELP Realise sustainable, long-term energy cost savings and environmental impacts Identifying, developing, implementing and sustaining energy cost saving projects. Started off with 117 saving opportunities evaluated against cost, NPV, technical, production and safety criteria resulting in 29 energy cost saving projects implemented. 15 Management of Change projects and 14 Minor Capital Projects. 12 Projects receiving Eskom funding All energy commodities considered part of the ELP scope
Internal & External M&V and Governance Structures put in place to ensure real, auditable savings
ELP Reached R110-million energy saving Sep 2015
Process Energy Optimisation Project on FAG Mills
FAG mills are link between Underground and Concentrator operations
FAG mills have installed capacity of 14MW FAG Mill Specification 9.75m diameter vessel/drum 2 x 3.5MW, fixed speed, induction motors per mill ROM grinding @ 750 tons per hour (no balls/rods) Rotating in both clock and anti-clockwise directions Mono-block mill liners made-up of high chrome material Fed with 3 x variable speed vibrating feeders Grinding ore from 200mm to <300µm (80% passing)
FAG mills considered bottleneck of mine in 2013 Operating at ~600 tons per hour compared to design capacity of 750 tons per hour Frequent exceedances of mill bearing pressure and power trip limits Frequent backlashing caused by over-filled mill Operating well below mill trip limits for most of time to avoid tripping Operating on manual control for most of time resulting in high operator workload Operating at higher specific energy consumption [kwh/t] Lift II plans to increase daily production from 28 000 tons per day to 33 500 tons per day
MillScan system is a comprehensive mill vibration, monitoring, analysis and control system MineralScan MillSlicer (MillScan) technology uses vibration sensors around mill s structural points as well as mill shell to obtain real-time mill fill levels and charge strike angle Mill fill level and charge strike angle be used for: Automated control (basic or expert control), or Informative to assist operators in monitoring and controlling their mills manually Advantages of the system: Increased grinding efficiency resulting in reduced kwh/ton Reduced liner damages Reduced output particle size standard deviation No cross-talk between two adjacent mills (unlike acoustic systems) Easy integration with existing SCADA and control systems
First ever installation of MillScan system on FAG mills in the world done in Oct 2013
Project performance was M&V d as per IPMVP Option B Baselines established for both mills individually: 9 months production and energy consumption data used 30-minute intervals Baseline adjustments done as per IPMVP to account for fluctuations in production Performance assessments done on daily as well as monthly basis: Daily to pick-up on any abnormalities and to fine tune PID control Monthly to consolidate on performance of project Project trialed over 45 day period and once proven, made permanent
Project showed combined kwh/t improvement of 12% on average over past 24 months FAG Mill 1: Baseline: 8.8 kwh/ton Post-Imp: 8.2 kwh/ton Impact: 0.6 kwh/t (7%) FAG Mill 2: Baseline: 10.3 kwh/ton Post-Imp: 8.6 kwh/ton Impact: 1.7 kwh/t (17%) Combined Impact: Baseline: 9.6 kwh/ton Post-Imp: 8.4 kwh/ton Impact: 1.2 kwh/t (12%)
Accumulated energy cost saving of R10-million achieved since ITD R 6.88- million forecasted R 11.82- million forecasted
Summary Project Improvements Reduction in specific energy consumption by: 1.2 kwh/ton (12.1%) equating to R10-million since ITD Maintained grinding KPI of 80% passing 300µm Reduced operator workload Mills capable of running closer to design specification without risk of tripping or backlashing No negative impact on liner wear noticed to date Unlocked bottleneck plant Next steps: Continuous daily and monthly performance tracking to sustain savings Cross belt magnetic separator metal removal from mill feed conveyor without stopping Ore sorter removing hard dolerite from milling circuit instead of recirculating it back into the mill