2014-11-24
Conveyors www.kmg.agh.edu.pl
Department of Mining, Dressing and Transport Machines AGH
Properties Bulk Solids Piotr Kulinowski, Ph. D. Eng. Piotr Kasza, Ph. D. Eng. (
[email protected] 12617 30 92 B-2 ground-floor room 6
consultations: Mondays 11.00 - 12.00 ©
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Properties of Bulk Materials www.kmg.agh.edu.pl
Types of transported cargoes General cargo
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…some examples
Bulk cargo
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Properties of Bulk Materials www.kmg.agh.edu.pl
General cargo – single objects (boxes, containers, packages, machines, etc…). Classified according to their dimmensions, shape, weight and others, such as: inflammability, toxicity, explosivness, corrosivity, fragility, humidity resistance etc… Bulk cargo – grainy or dusty bulk material (coal, ore, gravel, sand, cement, flour etc…). Bulk materials are characterized by: • • • • • • • • • • • •
granulation or dustiness, density, natural angle of repose, internal friction, static and kinetic friction, hardness, attrition, crushing sensivity, change of properties due to vibrations, temperature, water or humidity, adhesion, plasticity, electrostatic properties.
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Properties of Bulk Materials www.kmg.agh.edu.pl
Granulation – numerical definition of material particles according to their size. The size of a single particle is defined by the maximum value of dimension measured by diagonal of cuboid as a contour of the particle. Transpotred material is: • sorted, when:
amax 2.5 amin
a*
amax amin 2
• unsorted, when:
amax 2.5 amin
a* amax
a* 3 a1 a2 a3
where: a* - average size of a particle
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Properties of Bulk Materials www.kmg.agh.edu.pl www.kmg.agh.edu.pl
According to particle size cllasification is as follows: • massive a* > 300 mm • lumpy 160 < a* < 300 mm •
middling lumpy 60 < a*< 160 mm
•
fine lumpy 10 < a*< 60 mm
•
grained 2 < a*< 10 mm
•
fine grained 0.5 < a*< 2 mm
•
powdery 0.05 < a*< 0.5 mm
•
dusty a*< 0.05 mm
Granulation is characterized by particle size distribution chart ©
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Properties of Bulk Materials www.kmg.agh.edu.pl
Bulk Density – mass of a cubic meter freely poured bulk, contains some leeks. ρ [kg/m3] According to bulk density cllasification is as follows: • light: 0,6 t/m3 • average: 0,6 1,1 t/m3 •
heavy: 1,1 2,0 t/m3
•
very heavy: 2,0 t/m3
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Properties of Bulk Materials www.kmg.agh.edu.pl
Angle of Repose – angle between the surface of a piled-up bulk material and the horizontal plane. statical
φ
dynamical
0 (0.5 0.7)
1m
φ0 ©
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Angle of repose and surcharge www.kmg.agh.edu.pl
The angle of repose of a material is the acute angle which the surface of a normal, freely formed pile makes to the horizontal. The angle of surcharge of a material is the angle to the horizontal which the surface of the material assumes while the material is at rest on a moving conveyor belt.This angle usually is 5 degrees to 15 degrees less than the angle of repose, though in some materials it may be as much as 20 degrees less.
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Properties of Bulk Materials www.kmg.agh.edu.pl
Some examples…
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Properties of Bulk Materials www.kmg.agh.edu.pl
Friction External
Static
Internal Friction between bulk particles inside layer as a result of acting forces.
Kinetic
Bulk friction coefficient against walls or conveyors surface can be static mst or kinetic mkin
tg m st
α Values of external and internal friction coefficients must be obtained in experimental tests. ©
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Properties of Bulk Materials www.kmg.agh.edu.pl
Shearing Test
mobile frame
Pσ
sample
Pτ
fixed frame
dynamometer
a)
b)
Pσ
sample
mobile frame
Pσ
Pτ
shearing surface
Pτ
plate
fixed frame
m ©
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P P
arctan
P P
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Properties of Bulk Materials www.kmg.agh.edu.pl
Internal friction shearing force chart: 1 – black coal with sand, 2 – dry coal, 3 – polytroksane, 4 – dusty lignite
External friction shearing force chart ©
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Definitions and Symbols www.kmg.agh.edu.pl
Angle of repose - angle between the surface of a piled-up bulk solid and the horizontal plane (r). Effective angle of internal friction - angle between the abscissa and the tangent of the curve representing the relationship of shearing resistance to normal stress (i). Static angle of internal friction - the angle at which the bulk solid will begin to slide on itself when subjected to stress acting onto the shearing surface (st). Surcharge angle - dynamic angle of the material conveyed (, ): - [ISO] angle formed with the horizontal by the tangent to the material cross - section at the intersecting point with the belt in motion - [DIN] equivalent surcharge angle ( = 0.67)
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Flowability–angle of surcharge–angle of repose www.kmg.agh.edu.pl
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Characteristics of BuIk Solid Materials - CEMA www.kmg.agh.edu.pl
Material Characteristics
Code
Size
Very fine—100 mesh and under Fine—1/8 inch and under Granular—Under 1/2 inch Lumpy—containing lumps over 1/2‘ inch Irregular—stringy, interlocking, mats together
A B C D E
Flowability Angle of Repose
Very free flowing—angle of repose less than 19° Free-flowing—angle of repose 20° to 29° Average flowing—angle of repose 30° to 39° Sluggish—angle of repose 40° and over
1 2 3 4
Abrasiveness
Nonabrasive Abrasive Very abrasive Very sharp—cuts or gouges belt covers
5 6 7 8
Miscellaneous Characteristics (Sometimes more than one of these characteristics may apply)
Very dusty Aerates and develops fluid characteristics Contains explosive dust Contaminable, affecting use or saleability Degradable, affecting use or saleability Gives off harmful fumes or dust Highly corrosive Mildly corrosive Hygroscopic Interlocks or mats Oils or chemical present—may affect rubber products Packs under pressure Very light and fluffy—may be wind-swept Elevated temperature
L M N P 0 R S T U V W X V Z
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Example: A very fine material that is freeflowing, abrasive, and contains explosive dust would be designated:
Class A26N.
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Material characteristics and weight per cubic foot - CEMA www.kmg.agh.edu.pl
Material
Average weight (lbs/cu ft)
Angle of repose (degrees)
Recommended maximum inclination (degrees)
Code
Ashes, fly
40-45
42
20-25
A37
Cement, Portland
72-99
30-44
20-23
A36M
60
35
18
B35TY
Coal, lignite
40-45
38
22
D36T
Copper ore
120-150
30-44
20
*D37
Dolomite, lumpy
80-100
30-44
22
D36
Gravel, dry, sharp
90-100
30-44
15-17
D37
Coal, anthracite, river, or culm, ⅛ inch and under
Rice, hulled or polished
45-48
19
8
B15
100-110
30-44
22
D36
Salt, common dry, fine
70-80
25
11
D26TUW
Sandstone, broken
85-90
30-44
Wood chips
10-30
45
Rock, soft, excavated with shovel
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Characteristic
Particie Size
Powdery Granular: Fine Granular: Coarse Modular Lumpy Massive
Particle Size Variation (d = dmax)
< 10%: d to d/2; rest: < d/2 < 25%:d to d/2; rest:15%: d/10; rest d/10 to d/2 < 10%: d; rest: < d/10
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Characteristics of BuIk Solid Materials - ISO
Particle Shape
Flowability / Cohesion
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ISO Code Code
Description dmax 60
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Characteristics of BuIk Solid Materials - ISO
Characteristic
ISO Code Code
Description
Abrasiveness
Non-/sIightly abrasive Mildly abrasive Moderately abrasive Extremely abrasive
o o o
A1 A2 A3 A4
Corrosiveness
Non-corrosive Mildly corrosive Highly corrosive
p p
Cl C2 C3
Non-dusty Very dusty Harmful to life SusceptibIe to explosion
t t r
Dl D2 D3 D4
Dust
Low Tendency to degrade Medium or weather High
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q
G1 G2 G3
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Properties of Bulk Materials www.kmg.agh.edu.pl
DEM – DISCTERE ELEMENT METHOD A discrete element method (DEM), also called a distinct element method is any of family of numerical methods for computing the motion and effect of a large number of small particles. Though DEM is very closely related to molecular dynamics, the method is generally distinguished by its inclusion of rotational degrees-of-freedom as well as stateful contact and often complicated geometries. With advances in computing power and numerical algorithms for nearest neighbor sorting, it has become possible to numerically simulate millions of particles on a single processor. Today DEM is becoming widely accepted as an effective method of addressing engineering problems in granular and discontinuous materials, especially in granular flows, powder mechanics, and rock mechanics.
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Properties of Bulk Materials www.kmg.agh.edu.pl
DEM Solutions
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Properties of Bulk Materials - DEM www.kmg.agh.edu.pl
Transfer Chutes
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DEM - applications www.kmg.agh.edu.pl
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