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

rphilippe@hatch.cl

Hatch Ingenieros y Consultores Ltda, Chile