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Wim 2010 Raymond Philippe Sal Or Desal

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Sal or Desal: Seawater supply options for the mining industry

Sal or Desal: Seawater supply options for the mining industry

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Wim 2010 Raymond Philippe   Sal Or Desal Wim 2010 Raymond Philippe Sal Or Desal Presentation Transcript

  • SAL OR DESAL SEAWATER SUPPLY OPTIONS FOR THE MINING INDUSTRY Raymond Philippe, Richard Dixon and Silvana Dal Pozzo Hatch Ingenieros y Consultores Ltda, Chile
  • Decision Seawater Saline - desalinated • Is not (should not be): – CAPEX Saline = CAPEX desalinated – CAPEX desal plant + corrosion compensation – Trade-off based on SWOT analysis (qualitative) • Depending on the mining project, water supply may represent up to 10-30% of CAPEX of the overall project • Requieres engineering to get to a project feasibility estimate
  • Contents • Experience use of seawater in mining • Identification of differences salt vs. desalinated seawater – Chemical aspects – Conveyance – Aspects on the use of seawater in mining processes • Conclusions View slide
  • Characteristics Chilean Mining Project • Norte Chile (desert), water scarcity • High volumes (500 -10000 m3/h) • Project altitude (1500 – 4500 masl) • Distance to ocean (80-200 km) • Copper mining (Copper/moli, copper/gold) • Copper flotation – Greenfield – Technology conversion from oxides to sulphides processing View slide
  • Experience seawater usage • Desalinated seawater – Escondida, Chile 2002-2011 Installed SWRO Capacity 5,000,000 1400 – Cerro Lindo, Peru 4,500,000 1242 MGD 1200 1057 MGD 4,000,000 3,500,000 898 MGD 1000 • Potable water (SWRO) Capacity (M 3/d) 3,000,000 740 MGD 800 2,500,000 584 MGD 600 2,000,000 454 MGD 418 MGD 1,500,000 400 312 MGD Total Chilean mining 1,000,000 281 MGD Water consumption 500,000 200 65 MGD 0 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Annual Installed SWRO Capacity
  • Experience seawater usage • Salt water (seawater/ saline well water) • Michilla, Chile • Las Luces, Chile • Mantos de la Luna, Chile • BHP Nickel, Australia • Texada Mines, Canada • Batu Hijau, Indonesia • Esperanza, Chile (under construction)
  • Mantos de la Luna Michilla Las Luces Lipesed
  • Batu Hijau (Indonesia) Texada (Canada) All existing direct salt seawater usage is in mining projects at short distance and relatively low altitudes compared to the majority of the actual mining projects in Chile • Simple and economical conveyance systems • Water conveyance costs do not require process optimization (recirculation, thickened tailings)
  • Components Seawater supply system Minesite Pretreatment Altitude (masl) Desal plant Pumping Stations Intake/ Outfall Electrical Supply Distance (m)
  • Seawater Differences @15°C Saline Desalinated TDS mg/l 36000 205 Cl mg/l 20175 119 SO4 mg/l 2590 4 BOD5 mg/l variable <5 Viscosity m2/s.106 1.18431 1.13902 Specific Gravity kg/l 1.026 1.000
  • Salt vs desalinated seawater Possible impact differences in: • Seawater intake (outfall) • Pretreatment • Desalination plant • Conveyance system • Mineral Processing • Environment • Financing
  • Salt vs desalinated seawater Seawater intake and outfall • Intake volume capacity • Outfall from desalination plant • Permitting/Studies • Coastal space availability and concessions
  • Salt vs desalinated seawater Desalination plant • CAPEX – Mayor capital investment – For saline water: eventual requirement of smaller desal plant at minesite • Operation costs – Desalination well understood, global experience – Specialized personnel, due to distance, difficult to integrate with minesite
  • Salt vs desalinated seawater Pretreatment – Desalination process requires pretreatment – But salt water conveyance also requires pretreatment – Chemicals handling/storage – On site personnel – Effluent and solids generation – Organic matter • Removal instead of destruction • Red Tide events
  • Salt vs desalinated seawater Conveyance differences • Gravity (Difference 3%) • Viscosity (Difference 5 %) • Corrosion – Materials selection pipes + pumps – Pipe thickness (steel,corrosion compensation) • Corrosion velocity (mpy, mm/y) • Oxidation ≠ Chloride pitting – choose correct testprocedures – Pipe protection (cathodic, liners, coating)
  • Conveyance -Genijev criterium Pipe internal roughness as a function of time and fluid εt = ε0 + a t Genijev Roughness 9 – Salt water <a> = 0.51 8 – Desalinated water <a> = 0.025 7 6 Roughness (mm) 5 Desalinated 4 Saline 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Year Generally used Formula of Colebrook-White does not consider time or fluid dependency of pipe roughness
  • Salt vs desalinated seawater Conveyance Should consider and compensate for • Project life time • Required availability of water supply system • Difference in minimum pipe thickness requirements • Difference in pressure drop between desalinated and salt water L ρ – Piping design (include time dependency) ΔP = λ v2 – Number and position of pumping stations D 2 ** Avoid risk of underestimating pump capacities for salt water
  • Salt vs desalinated seawater Environment • Environmental – Desalination plant outfall – Contamination – Leakages – Tailings pond infiltration – Emergency systems (containment ponds) • Community issues – Desal plant location + size – Desalination plant outfall
  • Salt vs desalinated seawater Corrosion handling Materials selection (base case: carbon steel) • Desalination plant • Conveyance system • Concentrator OPEX • Antiscalant/Anticorrosion reagents • Spare parts (2% CAPEX/yr)
  • Salt vs desalinated seawater Copper Mineral Processing Consideration: Most processes were developed based on industrial experience with “good” water quality, not salt water • Sulphide processing (flotation), differences in – Tailings (conventional and thickened) – Molibdenum recovery – Concentrate quality – Carbonate/Gypsum scaling – Corrosion • Leaching – Oxides – Sulphides (bioleaching)
  • Salt water Tailings management • There is global industrial experience in conventional tailings deposits using salt water, however, there is none using thickened tailings • Thickened tailings with salt water behavior – Sedimentation velocity • Difference specific gravity • Capillary forces – Transport • Viscosity differences? • Salt precipitation (scaling)
  • Salt water Molibdenum recovery • Poor recovery of molibdenum in selective flotation step – Requires good quality water • Requires small desalination plant to wash rougher concentrate (CAPEX/OPEX) • Additional installations – Washing ] (2-3 steps) – Thickening ] – Eventually Filtering • Salt water requires higher dosification of reagents – Costs – Corrosion/scaling risk
  • Salt water used as Process Water • High concentrations of Cl y SO4 • Salt water recirculation costs (OPEX) • Higher reagents consumption • Build-up of salts in process water – Evaporation losses – Desalination at site: reject to process water • Molibdenum • Potable water • Concentrate humidity • Result: Process water may have even higher scaling and corrosion potential than fresh salt seawater
  • Salt water Reagents and consumables • Extra process modifications required – pH control – Flotation reagents efficiency – Pyrite depression – Organic reagent degradation due to chloride contact • Flocculants • Flotation reagents • Evaluate anticcorrosives (phosphates) interference in flotation processes • Higher steel consumption in ball mills
  • Salt vs desalinated seawater Electrical energy requirements • Seawater desalination – Reverse Osmosis (Chile) 4-5 kWh/m3 • Conveyance – Pipeline length – Project altitude – Pumping stations In general (new projects Chile): Energy consumption for conveyance >>> desalination
  • Salt vs desalinated seawater Financing Desalination plant financing • EPC as package within EPCM contract • BOO/BOT,… • US$/m3 Advantages • Take investment off of balance sheet • Lower OPEX? Disadvantages • Control • Supply assurance
  • Execution Program Mining projects • Conceptual Engineering – Definition water requirements – Trade-off salt vs desalinated water • (Pre)feasibility studies • EIA • Basic Engineering (acquisition major equipment) • Detailed Engineering and Construction
  • Execution program Seawater supply system Indicative timing • Preliminary Engineering 3-6 months • Base line studies 6-12 months • EIA/Permits/Rights of way 6-18 months • Acquisitions and delivery 10-14 months • Construction 6-12 months • Mining vs water supply project: – Velocity/timing differences – Pressure on water project – Influence sal/desal definition
  • Analysis salt vs desalinated water • CAPEX (water supply + mine) • OPEX (water supply + mine) • Costs/Penalties/Opportunities (water supply + mine) • Risks (water supply + mine) • Environment and Community aspects • Minelife Based on cuantitative analysis and differences, mining company can base it’s decision
  • Conclusions Salt vs desalinated seawater • Economic evaluation for both cases should consider not only differences in water supply systems but also associated costs to the overall mining project. • Industry experience: In general not all relevant aspects for the alternatives evaluation are being considered • Both alternatives should be developed to at least prefeasibility level (quantified) before decision is taken – Impact on CAPEX – Compatibilize execution programs