Heap leach op and water footprint

Heap Leaching and Water Footprint

Augusto Chung Ching, Rio Alto MiningOswaldo Tovar, Ingeniería de Recursos SRL

Overview

• Understand importance of water• Definition of Water footprint• Types of water• Water balance• Benchmark• Challenges• Proposal• Conclusions

Heap Leach & Water Footprint

• Understand your water in the mining industry:• Communicating water use is fundamental to maintaining

social license to operate• Water accounting is to focus on reducing your own

consumption• Water storage in heaps (iceberg) • Solution inventory (water and dissolved metals)• Permanent vs On-off pad• Water problems with communities and regulators• We license, take water, use, storage, recirculate as much

as possible, evaporate, treat, return to body water

Water Footprint

• Water footprint is the volume of fresh water used to produce a product summed over the various steps of the supply chain

• Water footprint goes on to:– Quantity of the volume– Consider the type of water used– Consider when and where the water is used

Examples of Water Footprint for…

• 1 cup of coffee, 150 liters of water• 1 kg refined sugar, 1500 liters• 1 kg of tomatoes, 180 liters• 1 sheet of A4 paper, 10 liters• 1 kg of meat, 15,500 liters• 1 kg of cotton, 11,000 liters• Treatment of 1 ton of Cu ore, 1050 liters• Treatment of 1 ton of Au ore, 1250 liters

Type of Water used

• Green water = rain water• Blue water = surface water, river, lakes,

underground water• Gray water = retreated water, polluted water

Green Water

Green Water (rain)

Impoundment

Incorporated into the heap or process

Evaporated

Blue Water

Blue Water(river, lake,Underground)

Evaporated volume

Returned to another catchment area or the sea

Incorporated to heap or process

Gray Water

Gray Water(volume ofpolluted water)

Bypassed

Treated and/or released into the water body

Consumed (incorporated to heap or process)

Water Footprint

• Measures fresh water appropriation• Actual, locally specific values• Always referring to full supply-chain• Focus on reducing own water footprint

Ground and surface water

rain

Runoffat field level

Non-productionrelated

evapotranspiration

Soil and vegetation

HEAP

process

Rivers, lakes

abstraction

Return flow

farms

Production-relatedevapotranspiration

Water-containedIn products

GREEN WF

evaporation

Water contained in products

Water to other catchment

BLUE WF

GRAY WF

Catchment area

Evapotranspiration• Evaporation is the process where liquid water is

converted into vapor water– Evaporation is predominant when crop is small and water loss is primarily by

soil evaporation, or under high frequency wetting when soil evaporation and evaporation of free water from plant surfaces can be high

• Evapotranspiration is vaporization of liquid water and plants / vapor removal from the atmosphere– ET is an energy controlled process requiring the

conversion of available radiation energy (sunshine) and sensible energy (heat contained in the air) into latent energy (energy stored in water vapor)

Some Global water footprint

• China, 2900 liters / person / day• India, 3000 liters / person / day• Indonesia, 3100 liters / person / day• Germany, 3900 liters / person / day• Saudi Arabia, 5100 liters / person / day• Australia, 6300 liters / person / day• USA, 7800 liters / person / day• Mongolia, 1000 liters / person / day

Water Footprint

• ISO 14046:2012“amount of all water flows –controlled and uncontrolled-consumed, used, evaporated, or contaminated to produce an output unit in”

m3/lb.Cu: for Cu leachingm3/oz.Au: for Au leachingm3/ton.Concentrate: for crush-mill-flotation

Perú included this KPI in production statistics since 2005

Benchmark

• We have to get agree for a common reference: – m3/input (m3/tpd)– m3/output– m3/area– m3/workforce

• Rates of consumption in: USA (copper mines in Arizona)

Source: Department of Mines and Mineral Resources of Arizona

m3/ton Cu fino

198544223

54200393

47

Adobe Acrobat Document

Adobe Acrobat Document

Benchmark

• Chile’ consumption

Source: Ministerio de Obras Públicas, Dirección General de Aguas, División de Estudios y Planificación

Adobe Acrobat Document

Benchmark

• Perú’ consumption

Source: Ministerio de Energía y Minas. Datos de Agosto 2010

Challenges

• Maximize recovery/revenues• Minimize water usage in the whole

process by zero discharge.• Which means:

– Eliminate unnecessary inputs– Ability to predict ionic concentrations en all

flows to avoid incrustations– Ability to recycle 100%– Identify sources of contamination in the

process

Proposal

Commitment to optimization

Philosophy of Water Management (“In Source Reduction”)

Comprehensive Survey (ionic)

Alternatives Analysis and Comparison

Decision Making

Output:1. Block diagram and mass balance2. Table of metallurgical parameters and simulation

criteria for each case3. Alternatives studied and simulated in Matlab-Simulink4. PFDs5. OPEX & CAPEX for decision making6. Risks and Opportunities for decision making7. Execution plan and schedule for next stages

Conclusions

• Standardization is pending task• Operations in desert (Chile, Nevada) are benchmark. Let’s support them

and then rely on their experience• Space for improvement in data management. • We need to internalize that water is a common economic resource.• This is not an only water/hydraulic problem. We have to understand about

metallurgic, kinetics, catalyst, cycles and optimize not only recovery but also water usage.

Q & A

Questions & Answers