Properties Bulk Solids

2014-11-24 Conveyors www.kmg.agh.edu.pl Department of Mining, Dressing and Transport Machines AGH Properties Bulk Solids Piotr Kulinowski, Ph. D. E...
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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 © [email protected], [email protected]

Department of Mining, Dressing and Transport Machines AGH

tel/fax +48126335162

Properties of Bulk Materials www.kmg.agh.edu.pl

Types of transported cargoes General cargo

© piot[email protected], [email protected]

…some examples

Bulk cargo

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2014-11-24

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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Department of Mining, Dressing and Transport Machines AGH

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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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2014-11-24

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 © [email protected], [email protected]

Department of Mining, Dressing and Transport Machines AGH

tel/fax +48126335162

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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2014-11-24

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 © [email protected], [email protected]

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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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2014-11-24

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. © [email protected], [email protected]

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2014-11-24

Properties of Bulk Materials www.kmg.agh.edu.pl

Shearing Test

mobile frame



sample



fixed frame

dynamometer

a)

b)



sample

mobile frame





shearing surface



plate

fixed frame

m © [email protected], [email protected]

P P

  arctan

P P

Department of Mining, Dressing and Transport Machines AGH

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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 © [email protected], [email protected]

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2014-11-24

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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tel/fax +48126335162

Flowability–angle of surcharge–angle of repose www.kmg.agh.edu.pl

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2014-11-24

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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E45WY tel/fax +48126335162

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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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2014-11-24

Properties of Bulk Materials - DEM www.kmg.agh.edu.pl

Transfer Chutes

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Department of Mining, Dressing and Transport Machines AGH

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DEM - applications www.kmg.agh.edu.pl

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