1

University of TorontoUniversity of Toronto

Energy Consumption in Copper Sulphide Smelting

Pascal Coursol, Phillip Mackey (Consultants-Extractive Metallurgy, Xstrata Process Support)

andCarlos Diaz

(Consultant and Adjunct Professor, University of Toronto)

Presented at the Copper 2010 ConferenceJune 7th, Hamburg, Germany

2

University of TorontoUniversity of Toronto

Presentation Outline

• Trend in energy consumption – Discussion of previous similar studies

• Methodology and assumptions • Description of the case studies

– Outokumpu-Kennecott – Isasmelt – Mitsubishi– Noranda-Teniente Bath Smelting

• Results and discussion • Suggestions for further energy reduction in copper

sulphide smelting

3

University of Toronto

Energy Consumption in Cu Smelting Trend over the Last Four Centuries (as MJ/t Cu - feed to metal)

•Energy consumption steadily decreasing

•Since 1900 energy consumption has dropped by a factor of about 30 times

•Energy at present time ~ 12,000-15 000 MJ/t Cu

The present study focuses on energy in sulphide smelting

4

University of Toronto

Previous Studies on Energy Consumption in Sulphide Smelting

• Studies selected for comparison • Kellogg and Henderson (1976), Cochilco

(2009), Piret (2009) and Marsden (2008)• Results from Kellogg and Henderson

(similar to our approach)

Processing Route Electric Energy

(MJ/tonne anode)

Fossil Fuel

(MJ/tonne anode)

Total

(MJ/tonne anode)

Hot Calcine Reverb [Kellogg76] 2,173 15,935 18,108

KH-Outokumpu Flash [Kellogg76] 7,477 6,760 14,237

KH-Mitsubishi [Kellogg76] 6,904 9,306 16,210

KH-Noranda [Kellogg76] 9,045 5,220 14,265

5

University of Toronto

Methodology Used in this Study

• Adopted basic approach of Kellogg and Henderson

• Selection of four “modern” flowsheets to compare energy consumption and CO2emissions • Developed four new METSIM models for heat

and mass balance• Compared energy results amongst the modern

and older technologies

6

University of Toronto

Some Features of the METSIM Models

• Proper definition of concentrate and flux mineralogies • Proper thermodynamic properties for molten slag and

matte • Some thermodynamic data imported from the

FactSage software into METSIM• Solubility of FeS in Slag

– Important for heat balance in smelting vessel • Fe3O4 solubility in slag and Matte

– Important for heat balance in smelting and converting• Key recycle streams included

• Slag concentrate, dust and reverts are important for heat balance of the smelting and converting units

7

University of Toronto

Some Key Assumptions Used for the Case Studies

• Standard concentrate and flux used • Double absorption acid plant adopted• Annual concentrate throughputs used:

• Outokumpu/Flash convert: 1.2Mt/year – 161 tph @ 85% Online time

• Isasmelt/PS converters: 1.2Mt/year – 161 tph @ 85 % Online time

• Mitsubish-S, C and CL furnaces: 0.75Mt/year– 111 tph @ 85% Online time

• Noranda/Teniente/PS Converters: 0.85Mt/year – 126 tph @ 85% Online time

• Waste heat recovery on smelting vessels, PS converters but not on anode furnaces

8

University of TorontoUniversity of Toronto

Outokumpu Flash Smelting + Kennecott-Outokumpu Flash Converting

9

University of TorontoUniversity of Toronto

Isasmelt Smelting + Pierce-Smith Converting

10

University of TorontoUniversity of Toronto

Mitsubishi Continuous Smelting Process

11

University of TorontoUniversity of Toronto

Noranda/Teniente Continuous Bath Smelting + Pierce-Smith Converting

12

University of Toronto

Main Aspects Considered in Energy Balance

• Fossil Fuel • Natural gas and coke for heat balance or process

requirements (local reduction)• Electricity

• Acid Plant, oxygen production, matte and slag grinding, blowers, secondary gas handling, auxiliary equipments,…

• The power plant efficiency was assumed to be 38%. This factor was applied to convert the electrical energy to thermal energy in the energy balance.

• Steam credits were applied when excess steam was produced

13

University of Toronto

Results Compared to Kellogg and Henderson (KH1976)

Processing Route Electric Energy

(MJ/tonne anode)

Fossil Fuel

(MJ/tonne anode)

Total

(MJ/tonne anode)

Flash-Flash (Present work) 9,266 1,518 10,784

Isasmelt (Present work) 6,903 4,175 11,078

Mitsubishi (Present work) 8,508 2,498 11,006

Noranda-Teniente (Present work) 10,088 2,657 12,746

Hot Calcine Reverb [Kellogg76] 2,173 15,935 18,108

KH-Outokumpu Flash [Kellogg76] 7,477 6,760 14,237

KH-Mitsubishi [Kellogg76] 6,904 9,306 16,210

KH-Noranda [Kellogg76] 9,045 5,220 14,265

Kellogg 76

Presentwork

The Flash-Flash, the Isasmelt and the Mitsubishi flowsheets have very similar energy consumption The Noranda/Teniente processes have a somewhat higher energy consumption.

14

University of Toronto

Difference Between this Study and the Data from Chilean Smelters

The difference in energy consumption represents many millions $US per site !!

Opportunity ?

15

University of Toronto

Difference Between the Ideal Condition and Data from Chilean Smelters

• Our calculations do not account for all “real life” aspects in the energy balance, hence our estimates may be slightly low.

• A part of the difference is due to “ideal conditions” used in our calculations (high throughput, steam drying, benchmark oxygen and acid plants,…)

• It is considered that an important part of the difference may be due to plant inefficiencies• An energy audit can help in identifying the best

opportunities to lower energy consumption

16

University of Toronto

Differences in Electrical Portion for the Four Flowsheets

Highest fuel, lower electricity

Highest electricity, lower fuel

17

University of Toronto

Main Assumptions to Calculate the Total CO2 Emissions for Each Flowsheet

• Different countries have different ways to produce electricity (hydro, coal, natural gas, fuel oil,…), leading to different CO2 emissions per MWh.

• In our analysis (next slide), we assumed two different scenario• The “Chilean” scenario

– 0.54t CO2 per MWh (Average for the two main energy grids in Chile employing different energy mixes)

• The “100% Coal” scenario

– 0.96t CO2 per MWh (all power from coal)

18

University of Toronto

Calculated CO2 emissions for copper smelting according to type of fuel employed at the power plant

19

University of Toronto

Conclusions

• The Flash-Flash, the Isasmelt and the Mitsubishi flowsheets have similar low energy consumption compared to the Noranda/Teniente flowsheet

• Our work appear consistent with the study from Kellogg and Henderson published in 1976• Today, higher oxygen enrichment are used and

more heat recovery was assumed in our cases• This type of modeling can be used to prepare

energy audits at smelter sites and identify the opportunities for improvements

• Fuel and electricity cost will significantly impact the optimal technology selection for a greenfield project

20

University of Toronto

Discussion

• Better copper recoveries were obtained in flowsheets including slag slow cooling and flotation.

• Our models can be modified to mix converting, slag cleaning and recycling options to obtain the best configuration for a given site.

21

University of Toronto

Suggestions for Further Improvements in Energy Efficiency

for Copper Sulfide Smelting

• Build smelters at optimal size to minimize energy consumption

• Lower the energy consumption for acid and oxygen production

• Develop good use for excess steam from waste heat boilers

• Utilization of higher oxygen enrichment• Tuyere/lance/concentrate burner design • Keep lowering the energy required for oxygen production

• Waste heat recovery from anode furnaces and converters • Reduce infiltration and improve waste heat boiler design to allow

higher efficiency and low maintenance