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Carrie Hartford delivered the presentation at 2014 Bulk Materials Handling Conference. The 11th annual Bulk Materials Handling Conference is an expert led forum focusing on the engineering behind the latest expansions and upgrades of bulk materials facilities. This conference will evaluate the latest engineering feats that are creating record levels of throughput whilst minimising downtime. For more information about the event, please visit: http://www.informa.com.au/bulkmaterials14
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Evaluating Transfer Chutes with Increased Throughput Bulk Materials Handling Conference 2014
Carrie Hartford Senior Engineer
Perth Western Australia [email protected]
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SCIENCE ⏐ENGINEERING ⏐DESIGN
WE ARE: A specialized engineering firm focusing on
providing clients solutions to material handling applications
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SCIENCE ⏐ENGINEERING ⏐DESIGN
COMPANY PROFILE
� Incorporated in 1966 by Dr. Andrew Jenike � World’s largest firm specializing in materials flow � About 80 personnel world-wide � Offices in Australia, Brazil, Canada, Chile, USA � 7,500+ projects world-wide � Over 11,000 bulk materials tested � 650+ man-years experience
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SCIENCE ⏐ENGINEERING ⏐DESIGN
OUR MISSION
To create value by assisting clients to improve the efficiency, reliability, and safety of their operations by preventing, eliminating, or
reducing problems related to bulk materials flow, storage, or processing.
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SCIENCE ⏐ENGINEERING ⏐DESIGN
OUR APPROACH
We use a scientific approach, based on the characteristics of the materials handled and
process requirements.
It is not a trial & error approach!
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SCIENCE ⏐ENGINEERING ⏐DESIGN
OUTLINE
� Review common transfer chute designs � Discuss typical transfer chute problems � Evaluate increasing throughput with existing
infrastructure � What about different material handled through an
existing system?
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SCIENCE ⏐ENGINEERING ⏐DESIGN
VARIOUS CHUTE DESIGNS
For free-flowing rocky material: � Rock box � Micro ledges
Minimise wear.
For fine, sticky material: � Hood and spoon � No ledges
Prevent plugging and minimise buildup.
What if the material is rocky and fine and sticky? � Prevent plugging and minimise wear
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SCIENCE ⏐ENGINEERING ⏐DESIGN
ROCK BOX CONFIGURATIONS
Use rock boxes only if material is free-flowing
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Cement Clinker Iron Ore
SCIENCE ⏐ENGINEERING ⏐DESIGN
ROCK BOX CONFIGURATIONS
Rock box with sticky bauxite leads to frequent head box plugging
Heavy residual left in head box
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SCIENCE ⏐ENGINEERING ⏐DESIGN
HOOD AND SPOON DESIGN
� Developed in early 1980’s by Jenike & Johanson (US Patent 4,646,910 - August 1985)
� Design reflects novel approach to controlling the material
� Minimises dust generation, centers the load on the receiving belt
� Minimises wear of the receiving belt by giving the load a velocity in the direction of the receiving belt
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SCIENCE ⏐ENGINEERING ⏐DESIGN
HOOD AND SPOON DESIGN
Sticky fines on impact plate leading to frequent plugging
Proper stream capture with hood (low impact angle)
Proper stream control with spoon
US Patent 4,646,910
Rhino horn
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SCIENCE ⏐ENGINEERING ⏐DESIGN
COMMON CHUTE FLOW PROBLEMS
� Plugging � Wear of chute surface � Spillage � Buildup � Dust generation � Excessive belt wear
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Plugging
SCIENCE ⏐ENGINEERING ⏐DESIGN
EXAMPLE CHUTE FLOW PROBLEMS
Wear of chute surface
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SCIENCE ⏐ENGINEERING ⏐DESIGN
EXAMPLE CHUTE FLOW PROBLEMS
Spillage
Buildup 14
SCIENCE ⏐ENGINEERING ⏐DESIGN
IMPACT ANGLE & SLIDING FRICTION
V2 = Velocity along chute after impact
V1 = Impact velocity θ = Impact angle φ’ = Wall friction angle
θ
V1
V2
V2V1= cosθ − sinθ tan "φ
Impact angle and sliding friction is critical in chute design: If θ + φ’= 90°, no resultant velocity
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SCIENCE ⏐ENGINEERING ⏐DESIGN
QUESTIONS ASKED TO MAXIMISE USAGE OF EXISTING PORT INFRASTRUCTURE
� Can we increase the throughput of the same material through the existing design? Consider: � Belt sizing and speed � Loads on the belt � Support structure � Material flow through the chutes
� Can we put a different material through the existing transfer chutes? � Example: handling magnetite concentrate in iron ore transfer chutes
� What are the implications? � Will material flow through the chutes?
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SCIENCE ⏐ENGINEERING ⏐DESIGN
CASE STUDY
� Iron ore export terminal in South Africa � Belt width: 1650 mm wide � Belt speed: 5.5 m/s � Flow rate: 10,000 tph � Right angle transfer chute
� Rock box used to minimize wear
� Client needed to increase throughput.
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SCIENCE ⏐ENGINEERING ⏐DESIGN
CASE STUDY
� By using rock boxes, the chutes did not wear, but as the flow rate increased, the chute began to plug frequently leading to: � Cascading shutdown of upstream conveyors � Belt tracking problems � Spillage � Dusting � Inability to obtain desired throughput
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SCIENCE ⏐ENGINEERING ⏐DESIGN
Increase in fines, mc, & flow rate
Buildup in the chute (eventual plugging)
Changed the flow
path through the
chute
Changed the way material
exited the chute
Spillage, dusting, & premature belt wear
PROGRESSION OF PROBLEMS
Iron Ore
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TO ANALYSE AND DESIGN CHUTES
• Bulk density • Coefficient of sliding friction • Particle size • Particle density • Chute tests
• Angle of repose • Drawdown angle • Wear tests • Angle of internal friction
Flow properties tests needed:
Angle of repose Drawdown angle
SCIENCE ⏐ENGINEERING ⏐DESIGN
Wear results vary and are dependent on material characteristics such as particle size, shape, and abrasiveness of particles
WEAR TESTS
AR 500
Test results are for example only
Alumina Ceramic
Arcoplate
Wear ratio (wear/
distance moved)
Pressure
Adjustable force
Bulk material In hopper
Collecting Drum
Screw Feeder
Wear coupon mounted in rotating head
Proprietary J&J wear testing apparatus
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SCIENCE ⏐ENGINEERING ⏐DESIGN
DEM ANALYSIS OF IRON ORE CHUTE
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SCIENCE ⏐ENGINEERING ⏐DESIGN
HOOD AND SPOON DESIGN
Proper belt loading with spoon
Proper stream capture with hood
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SCIENCE ⏐ENGINEERING ⏐DESIGN
HOOD AND SPOON DESIGN
Other benefits: � Minimal downtown – chute went 2.5
years before changing out the head chute, still not much wear in the spoon.
� Eliminated belt tracking problems � No spillage � Reduced dusting significantly � Obtained desired throughput
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SCIENCE ⏐ENGINEERING ⏐DESIGN
OTHER ISSUES FROM INCREASED FLOWRATE
� Example: Material flies over the head chute
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Head chute height was set based on cross sectional area of material on
belt and material
trajectory.
Belt speed and cross-sectional area of material
on the belt increased to
increase throughput.
Caused some material to fly over the head chute. Chute was also fuller than designed
for.
Resulted in increased
spillage and higher plugging
potential.
SCIENCE ⏐ENGINEERING ⏐DESIGN
CHANGING MATERIAL
� Example: Using magnetite in hematite handling systems with rock boxes
� Cycle times of fine, sticky material versus lump ore needs to be evaluated
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SCIENCE ⏐ENGINEERING ⏐DESIGN
CONCLUSION
� Increasing throughput and/or handling different material through existing infrastructure can have significant financial benefits.
� Material testing and DEM are good predictive tools to analyse the feasibility of a usage change.
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QUESTIONS?
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Carrie Hartford Senior Engineer
Perth Western Australia [email protected]
www.jenike.com