corin holmes - jenike & johanson - digging deeper - don’t become a case study!
TRANSCRIPT
Mineral Sands Conference
Digging Deeper – Don’t Become a Case Study! 15 – 16th March 2016
Corin Holmes, MSc Eng
Project Engineer Perth Western Australia [email protected]
+61 8 9277 3303
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 2
We are: A specialised engineering firm focusing on
providing clients solutions and peace of mind in relation to materials handling applications
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 3
Company profile
! Incorporated in 1966 by Dr. Andrew Jenike ! World’s largest firm specialising 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
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 4
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!
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 5
Outline ! Material handling
! Rand Study ! Common flow problems
! Flowability ! Flow properties testing ! Design considerations
! Case study ! Testing and design ! Problem and cause ! Revisit and learnings A pile of mineral sand… simple to handle, right…?
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 6
Rand Study ! Time to market
! Equipment or process development, new material implementation, troubleshooting, start-up times
! Rand Study, 40 processing plants in North America over 6 years
05
101520
Liquid-gas Solids-refined Solids-raw
Average startup time,
months
Type of feedstock
Planned startup timeActual startup time
Refs.: Chemical Innovation; Jan. 2000, pg. 35 and Chemical Engineering; Oct. 24, 1988, Vol. 95, Issue 15, pg. 89
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 7
Impacts of poor material handling ! Operational costs
! Production rate, efficiency, processing systems, equipment types, labour requirements
! Material quality ! Specification, segregation,
chemical uniformity, operator-dependent results
! Worker safety ! Exposure to operators,
engulfment, intervention, re-initiating flow
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 8
Common flow problems
! Arching (bridging) ! Ratholing ! Erratic flow ! Flooding ! Limited discharge rate
Material won’t flow! … Or, it flows uncontrollably!
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 9
Arching (bridging)
! Caused by cohesive strength or interlocking – results in no flow
Arch at outlet
Cohesive arch
Interlocking arch (common with large particles) Break an arch?
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 10
Ratholing
! Caused by cohesive strength – results in stagnant “non-moving” material
Limited live capacity
Worker safety?
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 11
Erratic flow
! Occurs with arching or ratholing
Arching Ratholing
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 12
Flooding
! Common with fine materials (< 150 µm)
Compact
Fluidised
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 13
Limited discharge rate ! Discharge rate affected (related to permeability) ! Can cause erratic flow
Discharge rate
Ideal
Actual
Feeder speed
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 14
Segregation
! Separation of particles by size, shape or chemical properties
Sifting segregation
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 15
Funnel flow
! Some material is moving while the remainder is stagnant
! First in – last out flow sequence
Flowing material
Stagnant material
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 16
Funnel flow
! Suitable for: ! Coarse particles ! Free-flowing materials ! Non-degrading materials ! Segregation not
important All 4 criteria must be met to reliably handle a material in funnel flow
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 17
Mass flow
! All material is in motion whenever any is discharged ! First in – first out flow sequence
All material moving
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 18
Mass flow
! Suitable for: ! Fine materials ! Cohesive solids ! Degradable material ! Materials which segregate
Flow must occur along hopper walls to reliably handle a material in mass flow
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 19
Expanded flow
! Combination of a mass flow hopper beneath a funnel flow hopper ! Major advantage: headroom savings ! Stagnant material prevents wear on bin wall ! All material moving in hopper which
promotes steady discharge
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 20
Flow / no flow postulate
“Gravity flow of a solid in a channel will take place provided the yield strength which the solid develops as a result of the action of the consolidating pressures is insufficient to support an obstruction to flow.”
Material will flow when the stresses exceed the strength
* A.W. Jenike “Storage and flow of solids, bulletin 123”, 1964
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 21
Flowability
! “Flowability” is a function of the material AND the equipment ! “Poor flowing” material can be
handled easily in properly designed equipment
! “Easy flowing” material can present flow problems in poorly designed equipment
Material ßà Equipment
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 22
What affects flow properties?
! Particle size and distribution
! Particle shape ! Chemical
composition ! Moisture ! Time at rest ! Temperature ! Relative humidity 0.3% moisture 2.1% moisture
Rutile ore (-38 μm)
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 23
Flow properties testing
! Used to characterise a material ! Provides an understanding of flowability ! Used for design and selection
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 24
Jenike Shear Tester
! Cohesive strength and wall friction - ASTM standard D6128
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 25
Cohesive strength
! Flow function ! Used to determine minimum required outlet sizes to
overcome arching or ratholing.
Major Consolidating Pressure (σ1)
Cohesive strength (FC)
Flow Function
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 26
Wall friction
! Wall yield locus ! Used to determine hopper angles in a mass flow bin, to
ensure material is flowing on the wall and not itself.
φʹ
φ’ = Wall friction angle, degµ = Coefficient of friction = τ/σn = Tangent (φ’)
ShearStress (τ)
Normal Pressure (σn)0
Wall yield locus
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 27
Compressibility
! Bulk density range ! ASTM standard
D6683
! Used for rate, strength, and load calculations
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 28
Permeability
! Flow of air through particles at different bulk densities
! Used to determine the critical discharge rate
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 29
! Apply use of appropriate flow pattern ! Mass flow or funnel flow (or expanded flow)
! Understand material conditions ! Material, moisture, particle size, storage time at rest…
! Apply results ! Hopper outlet size ! Hopper angles ! Wall surfaces (wear liners…)
! Set design basis Material ßà Equipment
Flow properties testing ! design basis
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 30
! There are many feeder types and options available
! For reliable operation the feeder must be selected based on the properties of the material to be handled
Feeder selection
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 31
Design basis
! Bin capacity requirements ! Storage time requirements ! Size requirements ! Discharge rate ! Feeder selection ! Conveyor throughput ! etc… …each aspect needs to consider flow properties of the material to be handled.
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 32
Case study – sandy material
! Overview ! Static grizzly application
feeding hopper to downstream process
! Front-end of plant ! Fed from mine by dump
truck
Example image courtesy of www.eemllc.com
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 33
Case Study ! Testing was performed on a
“representative” material (Sample A) to achieve reliable design ! Understand material ! Rand study
! Tested conditions: -5mm size fraction, 9% and 14% moistures
! Design criteria set: ! ~50mm top size ! Grizzly aperture 150mm wide
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 34
! Actual Material: Digging Deeper ! Wetter/higher clay content material
being mined at lower levels ! Needed larger outlets to overcome
arching across grizzly bars
! Results ! Blocked grizzly ! Manual intervention
! Front-end loader used to push and scrape material through grizzly slots
! Reduced production
Case Study
Image taken from beneath grizzly
Image taken of truck dumping
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 35
Case Study
! J&J approach ! Conducted site visit to gather info ! Obtained “representative” material (Sample B) for testing –
from bottom layer of mining area (worst case material) ! Tested Sample B
! Results showed larger arching dimensions ~4x greater were required than Sample A
! Review of grizzly design ! Supplied options for process improvement
! Different methods of screening (trommel, scalper screen, etc.) ! Process and operational control
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 36
Case Study
! Learnings ! A representative material must be selected for material
characterisation ! Understand how material properties may change
over a mine’s life (early core sample testing etc.) ! Test results need to be applied holistically to suit
equipment and process ! Avoid being a statistic in Rand study
! Iterative process of equipment selection based on material properties and process Material "! Equipment determines Flow/No Flow
SCIENCE ⏐ ENGINEERING ⏐ DESIGN 37
! Understand your material ! Be aware of flow problems ! Conduct flow properties ! Apply flow properties to design
! Ensure Material "! Equipment connection
! Don’t become a statistic
Call to action: dig deeper don’t be a case study
Mineral Sands Conference
Digging Deeper – Don’t Become a Case Study!
Questions?
Corin Holmes, MSc Eng Project Engineer
Perth Western Australia [email protected]
+61 8 9277 3303