The economics of seawater use in the Chilean mining industry. Doug Aitken, SMI-ICE Chile

Transcription

1 The economics of seawater use in the Chilean mining industry Doug Aitken, SMI-ICE Chile

2 THE CONTEXT

3 The rise in the use of seawater is almost certain Montes, C (Chilean Copper Commission) Water Use in Copper Mining: Trends of a critical input, Expomin, 2016

4 But not expected to fully replace freshwater Cochilco, 2017 Primary concern cost Fundación Chile, 2017

5 The industry is becoming more efficient with its water use Montes, C (Chilean Copper Commission) Water Use in Copper Mining: Trends of a critical input, Expomin, 2016

6 But lower ore grades mean an increase overall demand Fundación Chile, 2017

7 Desalination remains expensive Wood Mackenzie, Consejo Minero, 2013 Fundación Chile, 2017

8 Contributing factors to desal cost Cost breakdown Unit water cost by plant capacity Wedeles, C Huehmer et al. 2011

9 Historic desalination cost reductions Water Reuse Association, 2012

10 Costs should reduce to some degree Gao et al. 2017

11 Costs should reduce to some degree International Water Association, 2017

12 Changing electricity market should have impact Fundación Chile, 2017

13 Changing electricity market should have impact $21.5/MWh Nov Feb 2018 $96/MWh

14 Electricity demand and the impact of seawater Fundación Chile, 2017

15 REDUCING THE COST OF SEAWATER SUPPLIES

16 Reducing costs through partial desalination Salinity (sodium chloride concentration) not a problem for the flotation of copper minerals and their byproducts. The negative effect of seawater is the content of magnesium ions that precipitate, inhibiting molybdenite flotation, at the high ph required. Removal of these ions, prior to concentration, pre-treated seawater is as good, or better, for the recovery of copper and byproducts as fresh water. Additionally the removal of calcium and magnesium drastically reduces fouling pipes and pumps. Concha, F., Castro, S., and Vergara, M. 2017

17 Seawater supply costs considering elevation Water Production Cost, USD/m CAPEX Treatment OPEX Treatment CAPEX Conveyance OPEX Conveyance SWRO Elevation, m.a.s.l. 100,000 m 3 /day 160 km distance SWRO: 3 kwh/m 3 Electricity cost: 0.15 USD$/kWh Life time 25 years Water Cost, USD/m Reverse osmosis Precipitated with lime Raw seawater Elevation, m.a.s.l. Concha, F., Castro, S., and Vergara, M. 2017

18 Treatment and conveyance treatment comparisons SWRO PRE-TREATED SEAWATER RAW SEAWATER Concha, F., Castro, S., and Vergara, M. 2017

19 Treatment and conveyance electricity cost comparisons $0.15/kWh $0.06/kWh $0.02/kWh Concha, F., Castro, S., and Vergara, M. 2017

20 Cost reduction through increased water recovery Key model parameters 150,000 tonnes/day 160 km distance from intake SWRO: 3 kwh/m 3 Electricity cost: 0.15 USD$/kWh Life time 25 years Discount rate: 8% Basic tailings treatment (32%) v Advanced thickening (60%) v High pressure filtration (83.5%) Aitken et al. 2017

21 Mine water footprint and losses Process Road dust suppression 10,560 Human consumption 174 Raw water evaporation 6.6 Process water tank evaporation 10.2 Primary crusher 1080 Stockpile 360 Flotation cell 20.1 Concentrate thickener 3.6 Final concentrate 267 Tailings storage facility 96,076 Tailings thickener - Total losses 108,558 Base case - S1, S2 & S3 (m 3 /day) Onsite water losses Aitken et al. 2017

22 Reduction in operational water use Water footprint of a model copper mining operation (solids content - 60%) (solids content %) Process Base case - S1, S2 & S3 (m 3 /day) Scenario 4 - Thickening (m 3 /day) Scenario 5 - Filtration (m 3 /day) Road dust suppression 10,560 1,620 1,620 Human consumption Raw water evaporation Process water tank evaporation Primary crusher Stockpile Flotation cell Concentrate thickener Final concentrate Tailings storage facility 96,076 78,036 29,164 Tailings thickener Total losses 108,558 90,570 32,706 17% 70% Assuming high recovery rates. Not necessarily applicable to all sites due to tailings characteristics Aitken et al. 2017

23 Net present cost without enhanced water recovery SWRO PRE-TREATED SEAWATER RAW SEAWATER Aitken et al. 2017

24 Net present cost with filtration SWRO PRE-TREATED SEAWATER RAW SEAWATER Aitken et al. 2017

25 Net present cost improvement without water recovery SWRO RAW SEAWATER Sensitivity analysis of dewatering performance, discount rate and life span had little impact High recovery rates from tailings and good water use efficiency are essential at high levels of elevation to minimise costs

26 Costs of a seawater pipeline network - Antofagasta The objective: Determine the potential cost savings of sharing of desalination and supply infrastructure between mines Maya Senzano, M, Keir, G, McIntyre, N. 2015

27 Optimising pipeline routes

28 Example scenarios Maya Senzano, M, Keir, G, McIntyre, N. 2015

29 Pipe operation ($M/yr) Pipe Construction ($M) Desal. plant construction ($M) Desal. plant operation ($M/yr) Total ($M/yr)

30 Shared reservoir Mines

31 Optimising within mine clusters - Calama cluster Intake point Shared reservoir Mines Maya Senzano, M, Keir, G, McIntyre, N Mine number Flow [L/s] Mine 1 50 Mine 2 78 Mine 3 77 Mine Mine 5 915

32 [USD] [USD/year] Optimising within mine clusters - Calama cluster $ Pipeline cost $ Annual energy cost $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $0 Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 $0 Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 Maya Senzano, M, Keir, G, McIntyre, N. 2015

33 [USD/year] [USD] Optimising within mine clusters - Calama cluster Operational savings by year Investment savings $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $0 Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 $0 Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 Maya Senzano, M, Keir, G, McIntyre, N. 2015

34 Continuing research Quantifying financial risk of investing in seawater Economic costs and practical issues of shared water supply networks Improved water recovery from tailings facilities Improved water accounting and water use efficiency

35 A FEW THOUGHTS

36 A few thoughts The industry is likely to become very reliant on seawater due to environmental circumstances and legislation. This shift will have considerable impact on the energy demand and likely the cost of producing copper, particularly for operations at high elevation.

37 Improving water recovery is essential, particularly where operations are underperforming. Filtered tailings is an interesting option where applicable. Seawater networks and infrastructure costs sharing will be very important to reduce costs and environmental impacts. The changing energy market will have a profound impact on the costs and environmental impacts of the shift to seawater.

38 Doug Aitken SMI-ICE Chile