Download - Blast Fragmentation Management SAIMM
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Blast Fragmentation Management and its Impact on Gold Mining Process
SAIMM Drilling and Blasting School JUNE 2005
FJ Fourie and T Zaniewski
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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
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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
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Reef Appearance
2-5 mm
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VAAL REEF CARBON VAAL REEF CARBON SEAMSEAM
5 mm5 mm
Scanning Electron Scanning Electron Microscope ImageMicroscope Image
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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
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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.
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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
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The past
Powderised rockAnfo blastPowder Factor = 3.45 kg/m
Blast damage Overcharging with Anfo
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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
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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
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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
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FragmentationUniformity Factor
n = 0.75 n = 1.50
n = 1.0
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Digital imaging for Power Sieve
Non - uniform fragmentation with high content of fines
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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
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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
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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%)
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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
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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
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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
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Gold Deportment Study
Anfo vs Kubela -75 um
01020304050607080
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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
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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
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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
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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
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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
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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 %
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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)
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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 %
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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%
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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
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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
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From Anfex to Kubela 420
Rock blasted with ANFO PF 3.45 kg/m Rock blasted with Kubela 420 PF 2.2 kg/m
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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
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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
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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
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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
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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
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Wheel of change
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Acknowledgement
AnglogoldAshanti Kopanag Mine Team AMT UEE-Dantex AEL SGS Lakefield Research CSIR