invent
introduce
The development of a new geometrical blast fragmentation model and its application to
Grade Engineering®
David La RosaPrincipal Mining EngineerCRC ORE
STEP-CHANGE INNOVATIONS THAT DELIVER WHOLE-OF-MINE VALUE
CRC ORE:A NEW APPROACH
OUR PARTICIPANTS
ResearchersMETSMINING
Taking a New View of Ore Deposit Heterogeneity
Sustaining Whole of System Value and Execution
Selecting Effective Coarse Separation Technologies
Mapping Economic Benefit Over Life of Mine
Grade Engineering®
CRC ORE 4
Novel coarse separation technologiesSeparating mineral from non-valuable rock at the earliest part of the process.
CRC ORE 5
Naturalgrade
deportmentby size
Induced deportment
through differential
blasting
Sensorbased bulk
sorting
Sensorbased stream sorting
Coarsegravity
separation
Five coarse separation levers of Grade Engineering®
NATURAL DEPORTMENT
CRC ORE 6
88% of the metal has deported into 36% of the mass(-19mm fraction)
INDUCING DEPORTMENT
The block below contains;200kt @ 0.68% Cu
Same block now contains;60kt @ 0.28% Cu
140kt @ 0.85% CuCOG = 0.40%
Process 200 kt for 1360 t of copper• Process 140 kt for 1190t of copper• Save costs processing 60 kt sub-economic material and free
up capacity in concentrator
Inducing deportment has the potential to increase head grade , save energy and optimise resource extraction
EXPLOITING INDUCED DEPORTMENT
INDUCED DEPORTMENT - EXAMPLE
April 2011
1 5 10 15 20 25 30
Gra
de g
/t
0.00
2.00
4.00
8.00
10.00
12.00
6.00
Grad
e (g
/t)
INDUCED DEPORTMENT - EXAMPLE
Grade uplift of ~ 100%
1 5 10 15 20 25 30
Gra
de g
/tG
rade
g/t
0.00
2.00
4.00
8.00
10.00
12.00
6.00
Grad
e (g
/t)
April 2011
MOTIVATION FOR A GE AWARE FRAGMENTATION MODEL
In a perfect world, perfectly bi-modal size distributions (low grade = coarse and high grade = fine) will maximise the potential of induced deportment, alas we don’t live in a perfect world.
Screen Size
EMPIRICAL MODELS AND LIMITATIONS
• Significant operational experience with Crushed Zone Model (better the devil you know!)
• BUT blast-centric (e.g. burden x spacing is consistent)
• For induced deportment evaluations, PSD and grade, on a hole by hole basis is necessary.
• This would allow rockmass characteristics to be considered spatially when modelling the response of the rock mass to blasting.
THE HYPOTHESIS
Can the Crushed Zone fragmentation model be further augmented by applying the radial cracks to the insitu rock mass structure?
BREAKAGE MECHANISMS
Rock mass characterised by:• UCS• T• Block Size (2D)• Fines size distribution• E• ν• P and S wave velocities
Explosives characterised by:• VOD• Blast hole diameter• Charge length
Fines created in the crushed zone
Radial cracks break existing in-situ structure for the coarse portion of the PSD
No allowance for timing
THE BREAKAGE ‘STAR’
Defined by:• n cracks• CZ Diameter• Crack extension• Tip angle (set at 2°)
Creates fines and breaks insitu structure (described by a 2D collection of polygons)
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Can be defined by:
• Actual hole location (preferred)• Burden x Spacing x rows x hole
per row
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Explosives per hole:
• VOD• Density• Length
• used to proportion breakage to the entire bench
• Calculate volume of fines
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Will be able to eventually use Geotechnical block model to adjust rock mass characteristics on a hole by hole basis.
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Can be:• Regular sized• Gaussian distribution in x and y
directions (defined by σ and sd)
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Extends crack tips to next boundary to preclude odd shaped particles.
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Fines
Unbroken block
Broken block
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
Fines
Post blast blocks
In-situ blocks
MODELLING FLOW
Create Holes
Load Holes
Create CZ and radial cracks
Overlay in-situ structure
Extend cracks
Break in-situ structure
Add fines and coarse fragments
Fit curves and report
RR Fit
Swebrec fit
Raw PSD
CASE STUDIESParameter Case 1 Case 2 Case 3Orebody type Greenstone Gold Iron Oxide Copper Gold Copper PorphyryBench Height (m) 10 15 15Burden and Spacing (m) 3.5 x 4.5 5.7 x 6.5 9.5 x 10.5Sub-drill (m) 1.0 1.5 1.5Hole diameter (mm) 152 311 270Explosive Type Emulsion Emulsion EmulsionExplosive Length (m) 7.5 11.5 9.5Explosive Density (kg/m3) 1200 1250 1000VOD (m/s) 5000 5200 3700
Parameter Case 1 Case 2 Case 3UCS (MPa) 170 240 24T (MPa)* 17 20 2.4E (GPa)* 84 40 31Vp (m/s) 5000* 6731 5000*Rock Density (kg/m3) 2700 3700 2700Poisson's Ratio* 0.25 0.25 0.25Gamma* 3 3 3Pressure decay factor* -1.5 -1.5 -1.5In-situ block size 0.3 +/- 0.3 0.89 +/- 0.25 0.2 +/- 0.2Fines x50 5 5 5Fines n 0.7 0.7 0.7Crushed zone diameter (m) 1 2.2 3.2Number of cracks 7 10 14Crack extension (m) 1.7 3.2 4.4
Blast Design
Rock mass
CASE STUDY RESULTS
Adjusted parameters
In-situ structure - mean was obtained from the top-size of the available image analysis PSD, with adjustment to the SD
Fines Distribution – same for all three cases, P50 ~ 5mm
CASE 3 HISTOGRAM
In-situ blocks
CZ
The main drivers for the final distribution are the fines generated around the blast hole and the breakage of the in-situ rock mass structure.
APPLICATION IN THE GE® CONTEXT
• Limitation of CZM is that it results in a blast wide PSD
• Concept of the Roxel (sure there are other names for it but this is what I use)
• Automates the calculation of the volume of rock around each blast hole.
Finer High Grade Roxel
Coarser Low Grade Roxel
A SIMPLE EXAMPLE
0.09% 0.59%
0.29%Parameter Value
Processing Cost $12.26 $/t
Recovery 87.7%
Sale Price 6000 $/t
$527,401
Parameter Value
Processing Cost $12.26 $/t
GE® Cost $0.30 $/t
Recovery 87.7%
Sale Price 6000 $/t
$588,231 (+11.5%)
-90mm
+90mm(leach or waste)
0.28% CuHELE
Traditional Mining
Exploiting Induced Deportment
@ -31.9% feed tonnes+15.4% feed grade
Profit
FUTURE WORK and CONCLUSIONS
Future Work• More validations• Block model integration to assign hardness
and grade characteristics to each roxels worth of broken rock,
• Deterministic calculation of fines distribution from comminution parameters (Dwi, Axb)
• Incorporate inter-hole timing (?)
Summary• The hypothesis that this model was founded on appears to have some validity based on the
assumptions and data presented in this paper.
invent
introduce
Thank you!
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