Hatch Water PRM10
Transcript of Hatch Water PRM10
SAL OR DESAL
SEAWATER SUPPLY OPTIONS
FOR THE MINING INDUSTRY
Raymond Philippe
Hatch Ingenieros y Consultores Ltda, Chile
Characteristics
Chilean Mining Projects
• North Chile (desert), water scarcity
• High volumes (500 -10000 m3/h)
• Project altitude (1500 – 4500 masl)
• Distance to ocean (80-200 km)
• Copper mining (Copper/moly, copper/gold)
• Copper flotation
– Greenfield
– Technology conversion from oxides to sulphides processing
Seawater use in Mining
South America• Desalinated seawater
• Escondida, BHP, Chile
• Cerro Lindo, Milpo, Peru
• Candelaria, Freeport, Chile (Execution fase)
• Salt water (seawater/ saline well water)
• Michilla, Chile
• Las Luces, Chile
• Mantos de la Luna, Chile
• Lipesed (Chile)
• Esperanza, Chile (start-up)
• Several projects (Study fase)
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
• “Simple” and “economical” conveyance systems
• Water conveyance costs do not require process optimization
(recirculation, thickened tailings)
Components
Seawater supply system
Distance (m)
Altitude (
masl)
Intake/
Outfall
Pretreatment
Desal plant
Minesite
Pumping
Stations
Electrical
Supply
Seawater Conveyance
Aspects:
– Pipeline length
– Project altitude
– Pumping stations
– Water quality
In general (new projects Chile):
• CAPEX: Conveyance system >>> Desalination Plant
• OPEX: Conveyance system >>> desalination
Decision Seawater
Saline - desalinated• Is not (should not be):
– CAPEX desalinated = CAPEX Saline + CAPEX desal plant
(eventual corrosion compensation)
– Trade-off based on SWOT analysis (qualitative)
Depending on the project location, water supply may represent
up to 15 - 30% of CAPEX of the overall project
Salt vs desalinated seawater
Possible impact differences in:
• Seawater intake (outfall)
• Pretreatment
• Desalination plant
• Conveyance system
• Mineral Processing
• Product differences
• Environment
• Financing options
Salt vs desalinated seawater
Conveyance differences
• Gravity (Difference 3%)
• Viscosity (Difference 5 %)
• Corrosion
– Materials selection pipes + pumps
– Pipe thickness (bare steel,corrosion compensation) • Corrosion velocity (mpy, mm/y)
• Oxidation ≠ Chloride pitting – choose correct testprocedures
– Internal pipe protection (liners, coating)
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 1.184 1.139
Specific Gravity kg/l 1.026 1.000
Salt vs desalinated seawater Copper Mineral Processing
Consideration: Most mineral processes were developed based on
industrial experience with “good” water quality, not salt water
• Sulphide processing (flotation), differences in
– Tailings
– Concentrate quality and recovery
– Molibdenum recovery
– Carbonate/Gypsum scaling
– Corrosion
– Reagents consumption
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
• Result: Process water will have even higher scaling and
corrosion potential than fresh salt seawater
Execution program
Seawater supply systemIndicative timing
• Preliminary Engineering 3-6 months
• Base line studies 6-12 months
• EIA/Permits/Rights of way 12-18 months
• Acquisitions and delivery 14-18 months
• Construction 6-12 months
• Mining vs water supply project:
– Velocity/timing differences
– Pressure on water project
– Influence sal/desal definition
Sal – Desal Trade Off
• Trade off
– Intake/Outfall
– Desalination plant
– Conveyance system
– Corrosion management
– Mineral Processing differences
– Water requirements (quality and volumes)
– Project lifetime
Not always necessary to execute a complete trade-off!
• E.g. Does the Cu/Mo recovery difference pay the desalination process?
If so:
Probably desalinated seawater is more attractive than saline seawater
Conclusions
Salt vs desalinated seawater
• Existing salt water experience in mining industry not comparable
with most Chilean mining projects
• Economic evaluation for both cases should consider not only
differences in water supply systems but also associated costs and
opportunities to the overall mining project.
• Not always all relevant aspects for sal/desal evaluation are being
considered: Both alternatives should be developed (quantified) to at
least prefeasibility level before decision is taken
– Impact on CAPEX/OPEX
– Compatibilize execution programs
SAL OR DESAL
SEAWATER SUPPLY OPTIONS FOR THE
MINING INDUSTRY
Raymond Philippe
Hatch Ingenieros y Consultores Ltda, Chile