IMPROVING EFFICIENCIES: THE ROLE OF PROCESS AUDITS

Transcription

1 IMPROVING EFFICIENCIES: THE ROLE OF PROCESS AUDITS MINE AFRICA BREAKFAST, PDAC 2015 Mike Hallewell B.Sc., C.Eng. Business Development Manager

2 COMMITMENT TO SERVICING AFRICA s NEEDS Mines in Africa SGS in Africa 2

3 TYPICAL PLANT ISSUES n Plant management are pinching our gold!!?? n Our recovery is bad, must be the ore type!!?? n We cannot achieve recovery or concentrate grade!!?? n We cannot make throughput concentrate grade or recovery!!?? n Poor manual sampling, sample preparation at mine and plant Installed automatic samplers and adapted metallurgical accounting systems to back calculate head assay. n Found level controllers on flotation cells defective. Redesigned level controller measurement n Found ore type had changed mineralogically Introduced new Operational Practices. n Plant Design Infrastructure NOT as Feasibility Study recommended Capex Savings Subsequently Retrofitted at much greater cost to business due to metal losses incurred. 3

4 GLOBAL TREND WHY INCREASE EXISTING OPERATIONAL EFFICIENCIES? n This downturn is different n Financial support, specifically for greenfield projects is at an all time low n Mining industry performance is being scrutinised financially like never before n Risk mitigation is increasing mine development costs and timelines. n The global industry is forced to maximise return on investment n Post feasibility optimisation programs now occurring n Mining sector needs to innovate n Maximisation of metal recoveries and minimisation of costs is vital n Measurement of appropriate operational metrics is essential n The skills available in the next 10 years will be in shorter supply n This is why improving efficiencies is a key focus today SGS have significant skills in this area which compliment our current strong On site laboratory business which is very strong in Africa Commercial geochemical, metallurgical/mineralogical and trade business in Africa 4

5 WHAT IS A PROCESS AUDIT? 1. Review of feasibility study flowsheet design and testing 2. Review of metallurgical accounting 3. Metallurgy and mineralogy 4. Efficiency & metallurgical benchmark testing 5. Review of throughput, power usage and plant downtime 6. Review of instrumentation and process control 7. Review of operational practices 8. Review of health and safety 5

6 OPERATIONAL BEST PRACTICES In remote areas- Keep it simple!! n Critical points n Key measurements and KPI s n Data tracking and reporting n Communications up down and across n Design systems so that the easiest way to operate is the correct way. n Efficient plants are generally easy to operate. n One common operating strategy for all shifts NOT different strategies for each shift!! USGS Core Repository - Denver Plants run 24hrs a day not 8hr shifts!! 6

7 IMPROVED PROCESS CONTROL & AUTOMATION The future is advanced system control where applicable n Throughput and Recovery with lower grade deposits is key to project success Advanced control enables the process to self optimise itself 24/7. Always adds value to grinding circuit constrained operations n Real time measurement of KPIs is increasingly vital to ensure project success. n Data is required quicker and faster to speed up decision making processes where automation can not be applied. n Removes sensitivity of operations from human resources especially in remote geographically challenging areas. 7

8 MUPANE GOLD MINE, BOTSWANA 8

9 INITIAL FLOWSHEET n In Summary Crush Grind Float Carbon In Leach (CIL) Carbon elution, regeneration and EW Gold pour Tailings 9

10 THE (FORMER) ISSUE AT MUPANE The situation n 10% Increase in Tonnes 2010 n Pseudo CIP Circuit 2010 n Ore changes (oxide to sulphide) The problem n High soluble gold losses n Poor carbon elution The investigation n Diagnostic approach Carbon activity very poor (less than 10% mid-circuit & only 40% after regeneration) n Small scale testing and CIL modelling Simulate plant, model CIL performance Assess n Plant testing Organic poisoning of the carbon? Perhaps by flotation reagents? Regeneration efficiency? Bypass flotation for test case Improve kiln (higher temp, longer res time) 10

11 SGS CIP-CIL MODELLING METHODOLOGY n Rheology testwork to optimize pulp density n Determine gold leaching kinetics n Determine kinetics of gold adsorption on carbon n Model data-fitting Plug kinetic leaching and adsorption equilibrium constants (k s, k, K) into the rate and mass balance equations n Results Gold concentration profiles in the ore, on the carbon and in solution across multi-stage adsorption circuits. Plant design optimization based on metallurgical performance for various plant design and operating scenarios. 11

12 MODEL PARAMETERS INPUTS n Plant throughput (tonnage, pulp density, gold head grade). n Leach and adsorption constants. n Number and size of leach and adsorption tanks. n Desired concentrations of gold Barren solution On Loaded carbon, and on Eluted carbon. OUTPUTS n Amount of carbon needed for each stage. n Loaded carbon advance rate to elution and regeneration. n Gold lock-up in the plant on the carbon. n Concentration profiles of gold in solution in solids and on the carbon in each stage of the multi-stage circuit. 12

13 CIL PLANT PERFORMANCE 2009/2010 Analyzed Gold in solution (mg/l) Gold on carbon (g/t) (carbon activity) Gold in the ore (g/t) (feed grade) Q1/09 flotation Q2/09 no flot 2010 no flot Q1/09 Q2/ Q1/09 Q2/ CIL feed CIL CIL CIL CIL CIL CIL Recovery,%

14 BENEFITS n Sensitivity Analysis shows that a 12.5% decrease in processing costs increases the pretax NPV by about 6%. Reagent and power costs decreased because flotation pre-concentration was no longer used. n Gold recovery increased from 76% to 80.4% n $2.9 million to the bottom line year on year no capex costs n No flotation Plant - Opex savings increasing NPV 14

15 PROCESS AUDITS PROVIDES COMPETITIVE EDGE n Thinking globally n Acting locally n Using best practices n Cutting Edge Technologies n Enhancing Quality n Improving Productivity n Ensuring Compliance n Reducing Risk 15

16 n THANK YOU! 16