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Optimising Parameters and Measuring Improved Gold Recovery in a Copper-Zinc Flotation Circuit Myra Falls Operation Trev PowerPoint Presentation
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Optimising Parameters and Measuring Improved Gold Recovery in a Copper-Zinc Flotation Circuit Myra Falls Operation Trevor Yeomans NVI Mining. 4000 mtpd copper/zinc flotation mill with gold/silver. Historical Gold Recovery Gravity circuit – 2-5% Copper concentrate – 20-30%

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slide1

Optimising Parameters and Measuring Improved Gold Recovery in a Copper-Zinc Flotation Circuit Myra Falls OperationTrevor YeomansNVI Mining

slide2
4000 mtpd copper/zinc flotation mill with gold/silver
  • Historical Gold Recovery
    • Gravity circuit – 2-5%
    • Copper concentrate – 20-30%
    • Zinc concentrate – 13-23%
    • Overall – 35-58%
gravity circuit
Gravity Circuit
  • Installed in 1992, two Knelson CD-30
    • CD-30 on “A” Circuit
    • CD-30 on “B” Circuit
  • Gravity concentrate shipped offshore
  • One of the first sites in the world using automated Knelsons
  • Unusual upgrading step
    • Cleaning of rougher conc, using CD-30
myra falls upgrading step historical
Myra Falls Upgrading Step-Historical
  • Primary Knelsons operated on 6 hour concentrating cycles
  • Concentrate stored in two concentrate hoppers, one for each grinding circuit
  • Upgrading step:
    • Once per week, the “A” circuit Knelson was taken off line
    • The concentrate stored in each concentrate hopper was individually pumped to the A circuit Knelson
    • This “cleaned” product was decanted, dried, and shipped
    • The goal was to reduce the mass and increase the grade
    • No data on efficiency of this process
initial changes
Initial Changes
  • Myra Falls staff thought that shorter cycles and more frequent cleaning would improve results
  • Change made
    • Start decreasing primary cycle time from 6 to 1 hour
    • Start increasing frequency of cleaning step, to once every 12 hours
  • Result
    • Significant increase in gravity recovery
    • Positive influence on overall gold recovery
question
Question?
  • Why such an increase?
  • Was this due to…..
    • Ore change?
    • Short cycles?
    • Frequent cleaning?
  • How can we measure?
knelson gravity circuit audit goals
Knelson Gravity Circuit Audit - Goals
  • What is the effect of Knelson concentrating cycle time on gravity recovery
  • What are the losses associated with the unusual upgrade step
  • What alternatives for upgrading are feasible
    • Tabling
    • Intensive Leaching
  • How to maximize primary gravity recovery with the existing Knelson Concentrators
  • What is the upper limit of gravity recovery, and what additional equipment might be needed

Once results of sampling completed, circuit can be modeled

gravity circuit audit sampling
Gravity Circuit Audit - Sampling
  • Grinding Cyclones
    • Characterize for GRG recovery to underflow
    • Characterize GRG in COF before and after upgrading
  • Primary Knelson recovery – characterize for unit GRG recovery
    • KC con
    • KC tails
  • Upgrade system – recovery characterization
    • KC feed grade during upgrade
    • KC tails grade during upgrade
audit results grinding cyclones
Audit Results – Grinding Cyclones
  • GRG partition curve typical for finer grind circuits
  • Some coarser GRG exiting the circuit
audit results cyclone overflow
Audit Results– Cyclone Overflow
  • Significant increase in

GRG exiting during

upgrading

audit results upgrading
Audit Results- Upgrading
  • Significant increase in grade of tails in only a few minutes
  • This was with the already reduced cycle time and more frequent cleaning
old vs new upgrade frequency
Old vs New Upgrade Frequency

Previous Current

  • Primary cycles: 6 hours 1 hour
  • Cleaning: Weekly 12 hours
  • Gravity recovery 2-5% 15-20%
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RESULT OFCHANGES

GRAVITY Recovery increase ~12%

modelling outcomes
Acacia pilot study carried out

Excellent recovery

No copper solubility issues

Sensitive site for cyanide use (BC Park)

Table selected as being a reliable upgrade option

Table purchased and installed, Operational April 2006

Modelling - Outcomes
tabling upgrade circuit
TABLING UPGRADE CIRCUIT
  • NEW ‘FLAKE’ CONC @ 65% GOLD TO DORE
  • TABLE ‘MIDDLINGS’, WITH NO ‘FLAKE’

SOLD AS HISTORIC GRAVITY CONC. @ 10000 G/T

  • TABLE TAILINGS SENT DIRECTLY TO COPPER CONCENTRATE
  • NOTE 100% UPGRADING RECOVERY
overall outcomes and conclusions
OverallOutcomes and Conclusions

KNELSON OPERATING CHANGES:

  • Gravity recovery was increased to 15%, from 2-5%.
  • Overall Recovery Increase maybe?
  • Very simple operating changes made to gravity circuit.
  • Inexpensive test program, confirmed gain, and modelling predicted further possible gains.
slide28

OverallOutcomes and Conclusions

TABLING UPGRADING CHANGES:

100% stage recovery

Gravity recovery decrease ~ -5%

Copper conc increase ~ + 12%

Overall Recovery Increase YES, ~ + 10%

Mill tailings Decrease 0.3 g/t.