THE WOLFSON CENTRETHE WOLFSON CENTRE
Transcript of THE WOLFSON CENTRETHE WOLFSON CENTRE
THE WOLFSON CENTRETHE WOLFSON CENTREfor Bulk Solids Handling Technologyfor Bulk Solids Handling Technology
B66: Direct On-Line MeasurementB66: Direct On-Line Measurementof Wall Friction of Coal as anof Wall Friction of Coal as anIndicator ofIndicator of HandleabilityHandleability
J RJ R PillaiPillai
ObjectiveObjective
To develop an on-line measuring instrument to give aTo develop an on-line measuring instrument to give acontinuous readout of wall friction of coal, to assess itscontinuous readout of wall friction of coal, to assess its‘‘handleabilityhandleability’’
To Prove or disprove whether there is a:To Prove or disprove whether there is a:–– consistent link between changes in wall failure and internalconsistent link between changes in wall failure and internal
failure properties based on moisture content,failure properties based on moisture content,–– correlation between on-line and off-line wall frictioncorrelation between on-line and off-line wall friction
measurements.measurements.
Why?Why?
Variation in Flow properties
Blockages in bunkers & chutes
Unscheduled downtime
Process stoppages
TrainingTime Money
Off-linemeasurement
Wall friction tester - SetupWall friction tester - Setup
JenikeJenike type walltype wallfriction testerfriction tester
150
100 95
2518
‘Skid’ plate (SS 304‘Skid’ plate (SS 3042b) finish2b) finish
On-line test rigOn-line test rig
Continuous & rapidContinuous & rapidstatus monitoringstatus monitoring
No samplingNo samplingNo manual operationNo manual operationSimple and ruggedSimple and rugged
sensorssensorsCost effectiveCost effective
W(cg)
Pivot
Direct i on of mat eri al fl ow
Li nkageDead weight
Sl i der Pl at e
HV
d
Load cell
Schematic of linkage & skid plate assemblySchematic of linkage & skid plate assembly
Test conducted
Jenikewall friction
On-line Trials
CrushedGlass
CoalEC2101(RuM3)
Load0.42 kg,2.7 kg,4.7 kg
Speed0.01m/sec0.1 m/sec1 m/sec
CrushedGlass
CoalEC2101
CleanPlate
UncleanPlate
CleanPlate
UncleanPlate
From eachbatch
Angle of wall friction as a function of shearAngle of wall friction as a function of sheardisplacement on crushed glassdisplacement on crushed glass
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
Distance [m]
Fri
ctio
na
ng
le[d
eg]
0.1m/sec
1 m/sec
0.01m/sec
Crushed Glass
Crushed glassCrushed glass
Starting with a clean plate the trend measuredStarting with a clean plate the trend measuredon crushed glass can be broken down into 3on crushed glass can be broken down into 3stagesstages
An initial lead-in region, where the measuredAn initial lead-in region, where the measuredangle of wall friction was approximately constantangle of wall friction was approximately constant(0 – 50m)(0 – 50m)
••A transient condition, where the measured wallA transient condition, where the measured wallfriction increases, at a rate dependent on speedfriction increases, at a rate dependent on speed
••A final steady state wall friction value, obtainedA final steady state wall friction value, obtainedafter relatively large shear displacementafter relatively large shear displacement(~150m)(~150m)
Unlike crushed glass, the initial lower stable value for coal is notUnlike crushed glass, the initial lower stable value for coal is notwell definedwell defined
Gradual increase towards a higher steady state value at allGradual increase towards a higher steady state value at allspeed.speed.
Influence of velocity is negligible unlike with crushed glass.Influence of velocity is negligible unlike with crushed glass. More consistent result compared to crushed glassMore consistent result compared to crushed glass
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
Distance [m]
Fri
ctio
nan
gle
[deg
]
0.01m/seccoal
0.1m/seccoal
1 m/seccoal
Angle of wall friction as a function of shearAngle of wall friction as a function of sheardisplacement on coal (RuM3)displacement on coal (RuM3)
Comparison between failure loci obtained fromComparison between failure loci obtained fromon-line &on-line & JenikeJenike (“clean” & “unclean” Plate) for(“clean” & “unclean” Plate) for
crushed glasscrushed glass
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
Normal Stress [kPa]
Sh
ear
Str
ess
[kP
a]
0.01 m/sec {Initialvalue}
~0.01 m/sec {Finalvalue}
0.1 m/sec {Initialvalue}
0.1 m/sec {Finalvalue}
Jenike (clean)
Jenike (unclean)
Final value
Initial value
“Unclean”
“clean”
Comparison between failure loci obtained fromComparison between failure loci obtained fromon-line &on-line & JenikeJenike (“Clean” & “Unclean” Plate) for(“Clean” & “Unclean” Plate) for
coal (RuM3)coal (RuM3)
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
Normal force [kg]
Sh
ear
forc
e[k
g]
0.01 m/sec2% mois ture
0.01 m/sec(initialvalues )
unclean -2.4%mois ture
clean tes t3s t - 2.8%mois ture
Final values Initial values“unclean”
“clean”
–– TheThe JenikeJenike wall friction loci obtained from the “clean”wall friction loci obtained from the “clean”plate tests were similar & comparable to the lociplate tests were similar & comparable to the lociobtained from the initial stable values measured onobtained from the initial stable values measured onthe on-line wall friction testerthe on-line wall friction tester
–– TheThe JenikeJenike wall friction loci obtained from thewall friction loci obtained from the“unclean” plate tests showed significantly higher“unclean” plate tests showed significantly highershear force (than the clean plates) but lower valuesshear force (than the clean plates) but lower valuesthan the final stable value measured on the on-linethan the final stable value measured on the on-linewall friction testerwall friction tester
For both the crushed glass and the coal samples…For both the crushed glass and the coal samples…
Plausible causesPlausible causes
Effect of particle size and distribution in the on-line wallEffect of particle size and distribution in the on-line wallfriction testerfriction tester
In on-line tester ‘Skid’ plate is sheared over a large shearIn on-line tester ‘Skid’ plate is sheared over a large sheardisplacementdisplacement
Dynamic effect on the on-line wall friction tester withDynamic effect on the on-line wall friction tester withrespect to speed and load unlikerespect to speed and load unlike JenikeJenike type wall frictiontype wall frictiontestertester
By comparison in theBy comparison in the JenikeJenike wall friction testwall friction testthe powder sample used is very small andthe powder sample used is very small andmay not be representative samplemay not be representative sample
Effect of particle size onEffect of particle size on JenikeJenike type walltype wallfriction testerfriction tester
Results suggest that as the maximum particle sizereduces the wall friction increases
Angle of wall friction- Jenike - Coal EC2101 Particle size comparison
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5
10
15
20
25
30
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5
Normal load (kPa)
An
gle
ofW
allf
rictio
n(d
eg)
<1mm - samp 1[5%]
<1mm - samp 2[4%]
2~1mm - samp 1[5%]
2~1mm - samp 2[5%]
3~2mm - samp 1[5.3%]
3~2mm - samp 2[5.3%]
<1mm - samp 3[4.5%]
<1mm - samp 4[4.5%]
<1mm - samp 5[4.4%]
Interim ConclusionsInterim Conclusions
There is a significant difference in the angle of wallThere is a significant difference in the angle of wallfriction of a “clean” and “unclean “ surfacefriction of a “clean” and “unclean “ surface
Surface wear on the “skid” plate does not have aSurface wear on the “skid” plate does not have asignificant effect on the wall friction measurementsignificant effect on the wall friction measurement
The rate at which the wall friction increases is bulk solidThe rate at which the wall friction increases is bulk soliddependent, the glass showing a gradual transitiondependent, the glass showing a gradual transitionwhereas the coal increases rapidlywhereas the coal increases rapidly
From the tests carried out both theFrom the tests carried out both the JenikeJenike and the onlineand the onlinetester shows the same trend, though there are sometester shows the same trend, though there are somevariation seen quantitativelyvariation seen quantitatively
JenikeJenike wall friction testerwall friction tester
–– Test varying the moisture content on coalTest varying the moisture content on coal
Test on Annular shear cell varying the moisture contentTest on Annular shear cell varying the moisture content
Existing Online TesterExisting Online Tester
–– Add moisture to coal to find if it can sense the differenceAdd moisture to coal to find if it can sense the difference–– Test by introducing Pre-consolidation plateTest by introducing Pre-consolidation plate
Development of a separate pilot scale rig with trough shape beltDevelopment of a separate pilot scale rig with trough shape belt Other option considered for comparisonOther option considered for comparison
–– HopperHopper flowabilityflowability testertester
Proposed workProposed work
Schematic of on-line test unitSchematic of on-line test unit
Winch for up & downmovement
Roller forhorizontalmovement
Linkage
Materialflow
Enclosure
Loadcell set-up
‘Skid’Plate
Conveyor belt
Frame
Thanks .…Any Questions??Thanks .…Any Questions??