Properties Bulk Solids - kmg.agh.edu.pl · PDF fileProperties of Bulk Materials Angle of...

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© [email protected], [email protected] Department of Mining, Dressing and Transport Machines AGH tel/fax +48126335162

Conveyors

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

Types of transported cargoes …some examples

General cargo Bulk cargo

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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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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:

5.2a

a

min

max 2

aa*a minmax

where: a* - average size of a particle

• unsorted, when:

5.2a

a

min

max maxa*a 3321 aaa*a

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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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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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Angle of Repose – angle between the surface of a piled-up bulk material and

the horizontal plane.

φ

φ0

)7.05.0(01 m

statical

dynamical

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Angle of repose and surcharge

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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Some examples…

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Friction

External Internal

Static Kinetic

Bulk friction coefficient against walls or conveyors surface can be static mst or kinetic mkin

α

sttg m

Friction between bulk particles inside

layer as a result of acting forces.

Values of external and internal friction

coefficients must be obtained in

experimental tests.

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Shearing Test

Pσ

Pτ

dynamometer

sample

mobile

frame

fixed

frame

Pσ

Pτ Pτ

a) b) Pσ

mobile

frame

fixed

frame

plate

sample

shearing

surface

mP

P

P

Parctan

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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

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

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Characteristics of BuIk Solid Materials - CEMA

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

Example: A very fine material that is free-

flowing, abrasive, and contains explosive dust

would be designated: Class A26N.

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Material characteristics and weight per cubic foot - CEMA

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

Coal, anthracite, river, or culm, ⅛

inch and under

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

Rice, hulled or polished 45-48 19 8 B15

Rock, soft, excavated with shovel 100-110 30-44 22 D36

Salt, common dry, fine 70-80 25 11 D26TUW

Sandstone, broken 85-90 30-44 D37

Wood chips 10-30 45 27 E45WY

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Characteristics

of BuIk Solid Materials

- ISO

Characteristic Description ISO

Code Code

Particie Size

Powdery

Granular: Fine

Granular: Coarse

Modular

Lumpy

Massive

dmax <0.42 mm

< 3 mm

< 12 mm

< 40 mm

<200 mm

>200 mm

S1

S2

53

54

S5

S6

Particle Size

Variation

(d = dmax)

< 10%: d to d/2; rest: < d/2

< 25%:d to d/2; rest:<d/2

< 95%: d to d/2; rest: < d/10

< 10%:d to d/2; >15%: d/10; rest d/10 to d/2

< 10%: d; rest: < d/10

SV1

SV2

SV3

SV4

SV5

Particle Shape

Sharp edged - with three dimension similar

- with one dimension clearly greater

- with one dimension clearly smaller

Round edged — globular

Round edged—with one dimension clearly greater

lrregular - fibrous, stringy, curly, indescribable

I

II

III

IV

V

VI

E1

E2

E3

E4

E5

E6

Flowability /

Cohesion

Fluid-like flooding

Very free flowing

Free flowing

Ayerage flowing

Poor flowing, compact product

Sluggish, non-collapsible, entangled

0 < r < 30

30 < r < 45

45< r < 60

r > 60

1

2

3

4

5

6

F1

F2

F3

F4

F5

F6

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Characteristics

of BuIk Solid Materials

- ISO

Characteristic Description ISO

Code Code

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

Dust

Non-dusty

Very dusty

Harmful to life

SusceptibIe to explosion

t

t

r

Dl

D2

D3

D4

Tendency to degrade

or weather

Low

Medium

High

q

G1

G2

G3

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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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DEM Solutions

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Transfer Chutes

Properties of Bulk Materials - DEM

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DEM - applications

Properties Bulk Solids - kmg.agh.edu.pl · PDF fileProperties of Bulk Materials Angle of...

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