Blast Fragmentation Management and its Impact on Gold Mining Process

SAIMM Drilling and Blasting School JUNE 2005

FJ Fourie and T Zaniewski

Agenda

Why optimize u/g blasting Source of the gold losses Cost implication of the gold losses Some steps into gold loss research Possible methods to reduce gold losses Impact of explosives on fragmentation Fragmentation evaluation and test results Optimizing fragmentation Future work Conclusions and recommendations

Why Change ?

z Inconsistent drilling and blasting disciplinez Gold embedded in 2 - 5 mm thick bottom layer of

carbonaceous reefs (Vaal Reef)z Gold occurs in small particles ( - micron size)z During the blast gold is liberated and can be lostz Low MCF 58 % - 70 %, average 67.30 %z Improved safetyz Lets accept that we lose 30% of goldz We need better gold carrier

Reef Appearance

2-5 mm

VAAL REEF CARBON VAAL REEF CARBON SEAMSEAM

5 mm5 mm

Scanning Electron Scanning Electron Microscope ImageMicroscope Image

Gold association

50m

Au

resin

50m

Au

resin

OccludedOccluded

Au

py

25m

Au

py

25mLiberatedLiberated

100m

Au

qz

resin

py

100m

Au

qz

resin

py

AttachedAttached

Past Projects Aimed in Gold Recovery Improvement

The mining method

Reason for failure

1 Diamond Saw Cutting High cost, bulky equipment and complicated logistics

2 Diamond Wire Cutting High cost and jamming of the wire

3 Selective Blasting Mining Contamination of the reef with waste too high

4 Rock Splitter High cost and low reliability, efficiencies low

5 PCF High cost, and high dust and gas concentration

6 Threshold Blasting High dust concentration, stope drill rigs needed for accurate drilling.

Objectives

To control the blast that gold particles are not liberated

To improve MCF To reduce amount of fines during the blast To find a more effective transport medium for

gold from face to gold plant To eliminate gold migration into cracks To obtain uniform fragmentation of blasted

rock To improve safety

The past

Powderised rockAnfo blastPowder Factor = 3.45 kg/m

Blast damage Overcharging with Anfo

Implication of Gold Loss

May-05R' 000 Mine per year

Mine Gold kg-04 MCF-04 1.00% 5.00% 10.00% 15.00% @ 10 %GNM 2,060 67.35 2,599,852 12,999,258 25,998,515 38,997,773 311,982,183Kopanang 1,258 69.55 1,537,455 7,687,275 15,374,551 23,061,826 184,494,608Tau Lekoa 760 80.87 798,813 3,994,065 7,988,129 8,252,401 95,857,549Mponeng 1,136 85.75 1,126,064 5,630,321 11,260,641 8,252,401 135,127,697Tautona 1,472 79.44 1,575,025 7,875,126 15,750,252 15,996,363 189,003,021Savuka 408 84.02 412,759 2,063,794 4,127,589 4,637,205 49,531,064Anglogold Total R/mth 8,049,968 40,249,838 80,499,677 99,197,969Anglogold Total R/yr 96,599,612 482,998,061 965,996,122 1,190,375,624 965,996,122

Gold Price R/kg 85,000

Blast Optimisation Project - Potential financial gain due to improved MCF

Percentage improvement

Initial trails and test indicate a potentialfor blast optimization to influence at this level

Assumed gold price R 85 000/kg

Project Stages

AEL Power Sieve Tests Thumb Blocks Gold dispersed in mining water and ventilation ducts Screening and grading of the blasted rock (SGS

Lakefield Research) Gold deportment study Digital images fragmentation distribution analysis RFID tags (CSIR) Explosives testing Kubela, R 100 G, Rioflex

Power Sieve Test

Anfex Anfex Powergel PowergelTamping 813 810

Images 48 9 43 12 Xc 75.17 100.08 76.59 62.39 n 0.94 1.01 1.09 1.19

mm mm mm mmP20 Size 14.29 19.98 22.70 25.96P50 Size 46.24 73.25 61.92 60.66P80 Size 127.65 157.90 104.57 103.10Top Size 282.69 332.09 191.67 181.31

Xc mean fragmentation size

n uniformity index

P20 mean size at 20% passing

Kopanang requirementsX = 125 mmN =, > 1.2

FragmentationUniformity Factor

n = 0.75 n = 1.50

n = 1.0

Digital imaging for Power Sieve

Non - uniform fragmentation with high content of fines

Power Sieve

Based on digital images of fragmented rock

AEL POWERSIEVE FRAGMENTATION DISTRIBUTION

0.00

20.00

40.00

60.00

80.00

100.00

0 2 7 13 27 53 100

250

750

2000

Size mm

%

p

a

s

s

i

n

g

AnfexPG 813PG 810

Increasing uniformity reduces oversize and fines

After AEL

0 2 5 10 20 40 80 160

10

0

20

30

40

% R

etained on sieve

0 2 5 10 20 40 80 160

n=0.75

n=1.00

n=1.50

Sieve size, X cm

Uniformity,n

Xc

Gold dispersed in mine water

Determine whether gold is getting lost through water as used underground

Determine whether gold is getting lost through airways

Try and quantify the losses Real losses are the focus,

not apparent losses

Gold unaccounted for (28.6%)

Recovered Gold (69%)

Real losses (0.4%)

Air Borne Dust Migration during the Blast

AU concentration and distribution in ventilation air directly after the blast

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

3.5 5.6 6.4 7.0 8.5

Distance from face, m

m

g

/

m

0.0E+00

1.0E-05

2.0E-05

3.0E-05

4.0E-05

5.0E-05

6.0E-05

7.0E-05

g

r

a

m

s

AU in area (g)AU concetration

Total AU in air directly after blast

Assumptions:Air flow - 8 m/secBlast duration - 24 secDust air born - 10 min after blast

Bulk Fragmentation Sampling

Collection of samples for Fragmentation and Gold Analysies

3.0 m

Pan position during the blast

Pan position after the blast

Legend Prop

Camlock

Air hoist

Plank

By T Zaniewski

Monorope

Pack marked for AUsampling

Collection of samples for Fragmentation and Gold Analysies

3.0 m

Pan position during the blast

Pan position after the blast

Legend Prop

Camlock

Air hoist

Plank

By T Zaniewski

Monorope

Pack marked for AUsampling

Taking Sample forPhysical Screening and Grading

High accuracy Trusted results as screening

and grading is done by third party

3 D representation

/ High cost/ Labour intensive/ Long waiting time for the results

Bulk pan sampling method

Done in conjunction with SGS Lakefield Research Laboratories

Gold Deportment Study

Anfo vs Kubela -75 um

01020304050607080

Screening and grading cont

Explosives Fines < 1.0 mm, % Au, %

Anfex 9.7 24.0R100 G 7.9 17.5Powergel 5.7 14.0Kubela 420 4.2 7.5

Gold balance in fines vs. explosives type

Explosives type

AU liberated

%

AU Occluded

%

AU Attached

%

AU in Floats%

Anfex 34.6 13.1 16.9 35.4Kubela 420 19.6 21.0 7.6 51.9

Gold balance in fines cont

If mines gold called for is 1676 kg per month than:

Explosives type

AU in < 1.0 mm%

AU in < 1.0 mmkg

AU potential at loss , kg

Anfex 24.0 401% of AU at risk

162.8

Kubela 420 7.5 126% of AU at risk

29.2

Kubela 420 Conversion ResultsTarget Achieved

Fines production < 5 % 4.2 %

7.5 %

19.6 %

1.2

12.94 R/m

&&&

Safer than Anfo - no explosives related incidents

0 0

Gold contents in fines after blast < 10 %

Gold liberation ?

Fragmentation distribution N > 1

Explosives Cost R/mNo wastage

Neutral < 12.5 R/m

Ease to use User friendly

Acceptance by the crew high

Implementation process Within 1 month

Results with the Kubela 420

Conversion complete in Sep 04 2000 boxes of explosives per month less Powder factor down from 3.45 kg/m to 2.2 kg/m Production up - 6 % Fragmentation changed in right direction Stope grade down Belt grade up MCF up from - 67 % to - 71% avg. Gold plant lower consumption of the steel balls and

further optimization of the milling process

Fragmentation Down Stream Benefits

Area Mined M

20000

25000

30000

35000

40000

45000

m

m 32010 41512 38880 39985 38962 41914 40107 38103 39719 43275 42972 42223 40193 43266 37437 36838 43439

J04 F04 M04 A04 M04 J04 J04 A04 S04 O04 N04 D04 J05 F05 M05 A05 M05

Jan Aug 04 avg 38 479 Sep 04 May 05 41 040 Improvement 6.7 %

Fragmentation Down Stream Benefits

Mine Call Factor 2004/2005

50.00

55.00

60.00

65.00

70.00

75.00

80.00

P

e

r

c

e

n

t

a

g

e

MCF 60.90 70.19 67.61 66.78 64.10 67.90 73.60 67.13 67.68 69.99 71.43 74.41 67.01 76.53 70.49 70.47

F04 M04 A04 M04 J04 J04 A04 S04 O04 N04 D04 J05 F05 M05 A05 M05

Feb Jul 04 avg 67.30 % Aug 04 May 05 Avg 70.92%

Var 3.6 % (5.3 % improvement)

Fragmentation Down Stream Benefits

Total Cost R/m

500

700

900

1100

1300

1500

R

/

m

R/m 1396 1139 1222 1180 1188 1125 1165 1226 1135 1053 1053 1019 1144 1069 1050 1136 990

J04 F04 M04 A04 M04 J04 J04 A04 S04 O04 N04 D04 J05 F05 M05 A05 M05

Jan Aug 04 avg 1205 R/m Sep 04 Apr05 Avg 1072 R/m

Improvement 11 %

Fragmentation Down Stream Benefits

Kopanang - Mill Balls Consumption G/Ton vs Tons Milled

10

210

410

610

810

1,010

1,210

1,410

J '04 F M A M J J A S O N D J'05 F M A M J J A S O N D

B

a

l

l

s

G

/

T

o

n

0

50

100

150

200

250

300

350

Note: Mill Balls = 9% of total Treatment cost

T

o

n

s

(

T

'

0

0

0

)

Kop Balls G/ton

TL Balls G/tonKop T '000

TL T'000

Log. (Kop T '000)

Log. (Kop Balls G/ton)Log. (TL Balls G/ton)

Jan - Aug 04 480 Sep - May 05 440

Var % 8.7%

Fragmentation Down Stream Benefits

M e ta llu rg y T re a tm e n t C o s t R /T o n - K o p a n a n g v s T a u L e k o a

10

15

20

25

30

35

J '04 F M A M J J A S O N D J'0

5 F M A M J J A S O N D

R

/

T

o

n

M

i

l

l

e

d

0

5 0

1 0 0

1 5 0

2 0 0

2 5 0

T

o

n

s

(

T

'

0

0

0

)

K o pTL

K o p T '0 0 0TL T '0 0 0

L o g . (K o p )

L o g . (TL )

K op t d

Jan - Aug 04 25.26 R/tSep - May 05 24.00 R/t

Var % 5.00 %

R 2.7 M saving/year

Explosives Efficiencies

Kopanang Mine Explosives Efficiencies 2005

-5.00

10.0015.0020.0025.0030.0035.0040.0045.0050.0055.0060.00

R

/

m

Others 0.60 0.16 0.26 0.80 0.317 0.43

Tamping 0.87 0.65 0.86 1.00 1.081 0.89

Init Sys 36.80 39.40 26.63 34.01 38.34 33.885 34.45

Expl 12.55 13.31 10.99 13.68 11.99 14.524 12.90

2004 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec YTD

R/m2004 49.352005 47.14Var 2.21Var % 4.5 %Saving/year R1.03 M

From Anfex to Kubela 420

Rock blasted with ANFO PF 3.45 kg/m Rock blasted with Kubela 420 PF 2.2 kg/m

On line fragmentation monitoring

Status System operational Pictures in real time to surface Wipfrag computer on surface

Objectives Control tool Monitor changes due to

blasting malpractice Warning system Optimization of the milling

process

Analog vs. digital

Analog Quality 0.5 Mp Resolution > 2.0 mm Cost R 50 K

Digital Quality 6 Mp Resolution < 0.6 mm Cost R 20 K

2.0 mm 0.6 mm

Benefits on Line Fragmentation Monitoring

Through intensive on line and in real time monitoring of the blasting parameters and fragmentation it is possible to make beneficial adjustments to blasting practices and achieve significant improvement in operating cost by: Reduction of explosives cost Increased production rates Lower steel ball and power consumption in the milling

process

Improved Mine Call Factor

Forward planning

Interface TRICON ore flow monitoring system with WIPFRAG on line fragmentation monitoring system

Interface WIPFRAG system with gold plant controls Collect Kubela 420 calibration belt sample - June 05 Assess ore degradation during scraping, tramming

and transport process

Conclusions

Successful project (R 100 M ) Money well spent on research (R 0.7 M) Mine Call Factor on the right path Explosives change impacted on many

aspects of the mining process Safer conditions in working place

Wheel of change

Acknowledgement

AnglogoldAshanti Kopanag Mine Team AMT UEE-Dantex AEL SGS Lakefield Research CSIR