Corin Holmes - Jenike & Johanson - Digging Deeper - Don’t become a case study!

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


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


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!


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…?


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


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


Common flow problems

! Arching (bridging) ! Ratholing ! Erratic flow ! Flooding ! Limited discharge rate

Material won’t flow! … Or, it flows uncontrollably!


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?


Ratholing

! Caused by cohesive strength – results in stagnant “non-moving” material

Limited live capacity

Worker safety?


Erratic flow

! Occurs with arching or ratholing

Arching Ratholing


Flooding

! Common with fine materials (< 150 µm)

Compact

Fluidised


Limited discharge rate ! Discharge rate affected (related to permeability) ! Can cause erratic flow

Discharge rate

Ideal

Actual

Feeder speed


Segregation

! Separation of particles by size, shape or chemical properties

Sifting segregation


Funnel flow

! Some material is moving while the remainder is stagnant

! First in – last out flow sequence

Flowing material

Stagnant material


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


Mass flow

! All material is in motion whenever any is discharged ! First in – first out flow sequence

All material moving


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


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


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


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


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)


Flow properties testing

! Used to characterise a material ! Provides an understanding of flowability ! Used for design and selection


Jenike Shear Tester

! Cohesive strength and wall friction -  ASTM standard D6128


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


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


Compressibility

! Bulk density range ! ASTM standard

D6683

! Used for rate, strength, and load calculations


Permeability

! Flow of air through particles at different bulk densities

! Used to determine the critical discharge rate


! 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


! 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


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.


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


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


! 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


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


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


! 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

Corin Holmes - Jenike & Johanson - Digging Deeper - Don’t become a case study!

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