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HIGH PRESSURE GRINDING

AT VASILKOVKA GOLD

F.P. van der MeerA. RomanchenkoB. S.Ibrayev

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Location: Akmola Oblast, North-East Kazakhstan

Plant Capacity: 9-11 Million tonnes per year

ca 1,400 tonnes per hour

Ore Type/Mineralogy: Sulphide-rich quartzitics, granodiorite,

complex gold occurrence, from free gold to

ultrafine inclusions in sulfides.

UCS 180 MPa

Gold Production: Planned 13-15 tonnes per year (2011)

Processing Scheme: Includies gravity separation, HPGR, flotationstirred mill ultrafine grinding,

Leachox TM intensive leaching

VASILKOV GOLD J.V. (VasGold GOK, Kazzinc)

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VASGOLD PROCESS FLOW SHEET

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HPGR ADVANTAGES

High Capacity 1500 t/h per unit (specific throughput 250 ts/hm)

Low specific energy 1.6 kWh/t

3rd / 4th Stage Crushing product < 5 mm without need for screening

Ball mill work index reduced by 15 % from 16.5 kWh/t to 13.3 kWh/t

Micro-cracks enhanced gold liberation and leach recovery

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Two HPGR units in parallel, each treating 1,500 t/h

(400-500 t/h fresh feed, 1,000-1,100 t/h recycle)

HPGR APPLICATION SUMMARY

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HPGR SECTION FLOW SCHEME

Arrangement of HPGR in closed circuit

with partial product recycle.

Recycle load 150-250 % of fresh feed.

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VASILKOVKA applies a PARTIAL PRODUCT RECYCLE by EDGE CUTTING

Recycle of edge material and a proportion of centre material.

Main advantages: Generation of a fine product, suitable as ball mill feed,

without need for installing a screening plant and associated desagglomeration facilities

E ll t

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IN-PLANT TEST RESULTSEFFECT OF PRESSURE ON PRODUCT SIZE

E ll t

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IN-PLANT TEST RESULTSSIGNIFICANT EFFECT OF MOISTURE ON PRODUCT SIZE

E ll t

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IN-PLANT TEST RESULTSEFFECT OF MOISTURE ON SPECIFIC THROUGHPUT AND SPECIFIC ENERGY

E ll t

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FLAKES in HPGR DISCHARGEResult from

high pressure

compression

of the ore

Vasilkovka flakes(here apparent as

coarse material

on the HPGR

discharge conveyor)

represent about20 % of discharge

and are relatively

weak

Excellent

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VASILKOVKA FLAKES from TEST WORK

Excellent

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HPGR FEED SEGREGATION

Strongly affects:

- roll surface wear

- roll positioning

and

- grinding result.

Excellent

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SEGREGATION ON A CONVEYOR BELT

Excellent

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SEGREGATION ON A CONVEYOR BELT

Coarse Fine

Excellent

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ROLL SURFACE WEAR

Optimized moisture ensures a competent autogenous roll coatingPresently projected roll surface wear life to exceed 12,000 operating hours

Excellent

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VASILKOVKA HPGR SECTION LAY-OUT

Lay-out of conveyors,

intermediate feed bin,

tramp material bypass chute,

variable speed feeder,and small HPGR feed chute

were arranged to optimize

feeding conditions and

minimize segregation

Excellent

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AUTOMISED CONTROL SYSTEM for ROLL ALIGNMENTwith long-life oil lubricated cylindrical roller bearings and

Specially designed force distribution system.

Excellent

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CONCLUSIONS and OBSERVATIONS

Vasilkovka HPGRs were installed and commissioned successfully,

for reducing 50 mm top size gold ore to an 80 % < 5 mm product.

Metallurgical test programs identified critical operating parameters

such as pressure and moisture content, and optimized operation.

A well designed plant feed circuit enabled to minimize feed segregation, with

a dynamic hydraulic control system to maintain optimum process conditions.

HPGR design minimizes downtime for rolls exchange to near 24 hours

with a minimum of auxiliary maintenance facilities.

Projected roll surface wear life is presently anticipated

at near 12,000 operating hours

Excellent

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ACKNOWLEDGEMENTS

We would like to extend our gratitude to the whole team at Vasgold and Kazzink

in Kazakhstan and TOMS in Irkutsk for their willingness to provide information

and contribute to a successful HPGR application.

THANK YOU FOR YOUR KIND ATTENTION.

If you have any questions,I would be happy to answer these.