Hatch Water PRM10

17
SAL OR DESAL SEAWATER SUPPLY OPTIONS FOR THE MINING INDUSTRY Raymond Philippe Hatch Ingenieros y Consultores Ltda, Chile

Transcript of Hatch Water PRM10

Page 1: Hatch Water PRM10

SAL OR DESAL

SEAWATER SUPPLY OPTIONS

FOR THE MINING INDUSTRY

Raymond Philippe

Hatch Ingenieros y Consultores Ltda, Chile

Page 2: Hatch Water PRM10

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

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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)

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Mantos de la Luna Michilla

Las Luces Lipesed

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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)

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Components

Seawater supply system

Distance (m)

Altitude (

masl)

Intake/

Outfall

Pretreatment

Desal plant

Minesite

Pumping

Stations

Electrical

Supply

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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

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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

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Salt vs desalinated seawater

Possible impact differences in:

• Seawater intake (outfall)

• Pretreatment

• Desalination plant

• Conveyance system

• Mineral Processing

• Product differences

• Environment

• Financing options

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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)

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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

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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

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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

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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

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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

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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

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SAL OR DESAL

SEAWATER SUPPLY OPTIONS FOR THE

MINING INDUSTRY

Raymond Philippe

[email protected]

Hatch Ingenieros y Consultores Ltda, Chile