Energy Consumption in Copper Sulphide Smelting

Transcription

1 Energy Consumption in Copper Sulphide Smelting Pascal Coursol, Phillip Mackey (Consultants-Extractive Metallurgy, Xstrata Process Support) and Carlos Diaz (Consultant and Adjunct Professor, ) Presented at the Copper 2010 Conference June 7th, Hamburg, Germany 1

2 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 2

3 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, MJ/t Cu The present study focuses on energy in sulphide smelting 3

4 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 Fossil Fuel Total (MJ/tonne anode) (MJ/tonne anode) (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 4

5 Methodology Used in this Study Adopted basic approach of Kellogg and Henderson Selection of four modern flowsheets to compare energy consumption and CO 2 emissions Developed four new METSIM models for heat and mass balance Compared energy results amongst the modern and older technologies 5

6 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 Fe 3 O 4 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 6

7 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 % Online time Isasmelt/PS converters: 1.2Mt/year % Online time Mitsubish-S, C and CL furnaces: 0.75Mt/year % Online time Noranda/Teniente/PS Converters: 0.85Mt/year % Online time Waste heat recovery on smelting vessels, PS converters but not on anode furnaces 7

8 Outokumpu Flash Smelting + Kennecott-Outokumpu Flash Converting 8

9 Isasmelt Smelting + Pierce- Smith Converting 9

10 Mitsubishi Continuous Smelting Process 10

11 Noranda/Teniente Continuous Bath Smelting + Pierce-Smith Converting 11

12 Fossil Fuel Main Aspects Considered in Energy Balance 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 12

13 Results Compared to Kellogg and Henderson (KH1976) Processing Route Electric Energy Fossil Fuel Total (MJ/tonne anode) (MJ/tonne anode) (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 Present work 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 The Flash-Flash, the Isasmelt and the Mitsubishi flowsheets have very similar energy consumption The Noranda/Teniente processes have a somewhat higher energy consumption. Kellogg 76 13

14 Difference Between this Study and the Data from Chilean Smelters Opportunity? The difference in energy consumption represents many millions $US per site!! 14

15 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 15

16 Differences in Electrical Portion for the Four Flowsheets Highest fuel, lower electricity Highest electricity, lower fuel 16

17 Main Assumptions to Calculate the Total CO 2 Emissions for Each Flowsheet Different countries have different ways to produce electricity (hydro, coal, natural gas, fuel oil, ), leading to different CO 2 emissions per MWh. In our analysis (next slide), we assumed two different scenario The Chilean scenario 0.54t CO 2 per MWh (Average for the two main energy grids in Chile employing different energy mixes) The 100% Coal scenario 0.96t CO 2 per MWh (all power from coal) 17

18 Calculated CO 2 emissions for copper smelting according to type of fuel employed at the power plant 18

19 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 19

20 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. 20

21 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 21