-
John Meech1, Sepehr Sadrai2, and Bahador Mousavi Zadeh1
1 Norman B. Keevil Institute of Mining Engineering,The
University of British Columbia, Vancouver, BC, Canada, V6T1Z4
2 University of Queensland, Brisbane. Australia
Email: [email protected]
Presented at IPMM-2012, Foz do Iguacu, Brazil, September 2-3,
2012Presented at IPMM-2012, Foz do Iguau, Brazil, September 2-3,
2012
-
OutlineOutline
Introduction and Background High-Velocity Breakage Facility
Previous testwork Previous testwork Magnetite testwork Attrition
vs. Crack Propagation Rock on rock breakage Conclusions
-
Introduction and BackgroundIntroduction and Background
Comminution energy efficiency is low (~1-2%).Blasting energy
efficiency is about 10-20%.Previous work showed improvement with
higher Previous work showed improvement with higher
impact velocities. Tromans (2005) calculated
thermodynamically
the following breakage efficiency limits:
Under Tension 66%Under Compression 9%
-
High Impact Facility (Gas Gun)High Impact Facility (Gas
Gun)Bullet/SabotBullet/Sabot
Control ValvesControl Valves
Vacuum PumpVacuum Pump
Target ChamberTarget Chamber
Air CompressorAir Compressor
Valve ControllerValve Controller
-
High Impact Facility (Gas Gun)High Impact Facility (Gas Gun)
Sabot
Projectile
Flange
ReservoirQuick-
opening
valve
Vacuum
Launch Tube Velocity
Measurement
Device
Target
Sample
Chamber
Velocity Range = 50 to 500 m/s
-
Work with Quartz, Limestone and Rock SaltWork with Quartz,
Limestone and Rock Salt
S. Sadrai, J.A. Meech, M. Ghomshei, F. Sassani, and D. Tromans,
2006. Influence of impact velocity on fragmentation and the energy
efficiency of comminution. International J. Impact Engineering,
33(1-12), 723-734.
-
Properties of the Magnetite SampleProperties of the Magnetite
Sample
% Magnetite 76.0% Hematite 18.4% Pyrite 0.3% Oxide Rock 5.3%
Oxide Rock 5.3Particle Size Range (mm) - 2 + 1Specific Gravity
5.15Initial Bulk Density in tests 2.18 (~58%voids)Specific Surface
Area (m2g-1) 0.792Specific Surface Energy (Jcm-2) 6.45 *Bond Work
Index (kWht-1) 11.3
* Tromans and Meech, 2002
-
Base Case Base Case
10.0
100.0
C
u
m
u
l
a
t
i
v
e
P
a
s
s
i
n
g
(
%
)
1/2"St-10MagAD400
12.7 12.7 mm Steel Bullet and 10 g Target Sample (mm Steel
Bullet and 10 g Target Sample (--2 + 1 mm)2 + 1 mm)
0.1
1.0
30 120 480 1920
C
u
m
u
l
a
t
i
v
e
P
a
s
s
i
n
g
(
%
)
Particle Size (m)
1/2"St-10MagAD268
1/2"St-10MagAD201
1/2"St-10MagAD171
1/2"St-10MagAD148
1/2"St-10MagAD129
1/2"St-10MagAD72
-
Base Case Base Case 12.7 mm Steel Bullet and 10 g Target Sample
(12.7 mm Steel Bullet and 10 g Target Sample (--2 + 1 mm)2 + 1
mm)
Velocity
(ms-1)
Input
Energy (J)
P80
(m)
Bond
Energy
(J)*
Bond Energy
(% of Input)
- 37 m
(Wt. %)
- 150 m
(Wt. %)
0 0 1800 0 - 0 0.00 0 1800 0 - 0 0.0
72 29.6 1462 11 37 0.2 8.9
129 94.9 1265 18 19 0.3 16.2
148 126.6 1064 29 23 0.6 20.1
171 167.8 875 42 25 1.4 28.2
201 231.2 666 62 27 7.0 39.5
268 413.9 313 134 32 45.3 67.4
400 920.0 177 210 23 53.4 78.5
* Calculated from measured WI, P80, and F80
-
Base Case Base Case Bond Energy Analysis 1 Bond Energy Analysis
1 12.7 mm Steel Bullet and 10 g Target Sample (12.7 mm Steel Bullet
and 10 g Target Sample (--2 + 1 mm)2 + 1 mm)
-
Base Case Base Case Bond Energy Analysis 2 Bond Energy Analysis
2 12.7 mm Steel Bullet and 10 g Target Sample (12.7 mm Steel Bullet
and 10 g Target Sample (--2 + 1 mm)2 + 1 mm)
-
Base Case Base Case Suggested Breakage ModeSuggested Breakage
Mode 12.7 mm Steel Bullet and 10 g Target Sample (12.7 mm Steel
Bullet and 10 g Target Sample (--2 + 1 mm)2 + 1 mm)
-
Base Case Base Case Energy Efficiency vs. VelocityEnergy
Efficiency vs. Velocity
%Efficiency = 100 * New Surface Energy / Input Energy
-
P80 size vs. Velocity for P80 size vs. Velocity for
different F80 valuesdifferent F80 values
-
Energy Efficiency vs. Velocity for Energy Efficiency vs.
Velocity for
different feed size distributionsdifferent feed size
distributions
-
%Change in Specific Surface Area vs. Velocity%Change in Specific
Surface Area vs. Velocity
Increase in Surface Roughness (texture) plays a role
-
Efficiency vs. Speed for a Glass Bullet Efficiency vs. Speed for
a Glass Bullet
-
Comparison of Glass with Steel Comparison of Glass with
Steel
-
More important More important mass or velocity?mass or
velocity?
-
ReRe--evaluation of earlier testsevaluation of earlier tests
-
ConclusionsConclusions
1. 5% efficiency can be obtained by high-velocity impact.
2. Improvement due to both input energy and velocity.
3. Efficiency peaks at a velocity of about 250 ms-1.
4. Attrition breakage and crack propagation occur together.
5. Higher efficiency possible if compaction can be avoided.
-
ConclusionsConclusions
6. Trend in energy efficiency vs. velocity is conserved
regardless of target bed length, sample size distribution, or the
type of projectile.
7. Peak efficiency drops from 5% to 3% as F80 size drops
8. Mass appears to be more important than impact velocity.
9. For rock-on-rock impacts, trend in combined energy efficiency
is similar to a projectile that remains intact.
10. Future testwork will study redesigning the chamber to
enhance transfer of compression to tensile stresses.
-
Questions?
