Section IISection II Bulk Material Basics and Bulk Material Basics and

Their Influence on Their Influence on Equipment SelectionEquipment Selection

Sharon NowakK-Tron

Global Business Development Manager, Food and Pharmaceuticals

AgendaSession I - Corporate Introduction

Session II - Bulk Materials Basics (K-Tron)

Session III - Pneumatic Conveying Technology and Product Overview (K-Tron)

Session IV – Feeding Technology and Product Overview (K-Tron)

Session V – Advances in Twin Screw Compounding (Coperion)

Session VI (Coperion)

Session A: Food Extrusion on Twin Screw Extruders

Session B: New Developments in the Compounding of Plastics

Session VII (K-Tron)

Session A: Selecting the Right Feeder for Food/Pharmaceuticals

Session B: Selecting the Right Feeder for Plastics

Session VIII Pneumatic Conveying (K-Tron)

Session A: Pneumatic Conveying Systems for Food/Pharmaceuticals

Session B: Pneumatic Conveying Systems for Plastics

                                                               

Moist, sticky materials

                                       

Friable materials Large particles

                                                               

Blends or Masterbatch

Abrasive materials

Non-Free Flowing products

Free-flowing materials

Contamination Sensitive Products

Materials that Fluidize or liquefy

Products that pack, plug, cake or smear

Hazardous materials

Bulk Solids Definition

Where do they come from?

OrganicCocoa Powder

Flours

Sugar

InorganicCalcium carbonate

Titanium dioxide

Silica

Flowability Influencers

Material Characteristics & Tests

Material Characteristics which contribute to poor flowability

High Aspect Ratio

Wide PS & PSD

Compressibility and Cohesiveness

Bulk Densities Comparison

Compacted(CBD)

Loose(LBD)

Aerated(ABD)

10%

10%

Loose Bulk Density (LBD)

• Mass per volume of “loose” powder, gm/cm3

• In Carr series of measurements, a sieve with a mesh size greater than D100 of sample is used to control the flow of the material being analyzed. 100 CC

Sieve

Funnel

Sample

Slide courtesy of Hosokawa Micron Powder Systems, Summit, NJ

Tapping Unit

Packed or Compacted Bulk Density (CBD)

• Mass per volume of “packed” powder, gm/cm3.

• In Carr Series of measurements , fill container to top of retainer wall, typically the same size as the cup.

• Tapping Unit raises and drops container automatically.

Carr Standard:

18 mm 180 taps

100 CC

Sieve

Funnel

Retainer

Sample

Slide courtesy of Hosokawa Micron Powder Systems, Summit, NJ

Bulk Density Affects…

Inorganic:Bulk Density of Calcium Carbonate

LBD 0.3 g/cm3

CBD 0.4 g/cm3 LBD 1.38 g/cm3

CBD 1.47 g/cm3

CaCO3 (95% pure) CaCO3 (99% pure)

Organic:Bulk Density of Sugars

LBD .88 g/cm3

CBD 1.06 g/cm3 LBD .68 g/cm3

CBD .95 g/cm3

Particle Shape

Aspect Ratio

Sample Sieve Analysis of Powdered Sugar

Particle Size

Code A

Code C

Code B

Particle Size & PSD%

Pas

sin

g

Particle Size (mm)10 1 0.1

Sieve Number

10

20

30

40

50

60

70

80

90

1001/4 31/2 5 10 20 30 40 60

2468 0.20.40.60.8

80 100

Broad Distribution

Narrow Distribution

Top Cut

d50

Particle Hardness

Hardness Methods

Rockwell

Brinell

Vickers

Knoop

Shore

Mohs

Barcol

Mineralname Hardness (Mohs) Hardness (Vickers)

kg/mm2

Graphite 1–2 VHN10=7–11

Tin 1½ VHN10=7–9

Bismuth 2–2½ VHN100=16–18

Gold 2½ VHN10=30–34

Silver 2½ VHN100=61–65

Chalcocite 2½–3 VHN100=84–87

Copper 2½–3 VHN100=77–99

Galena 2½ VHN100=79–104

Sphalerite 3½–4 VHN100=208–224

Heazlewoodite 4 VHN100=230–254

Carrollite 4½–5½ VHN100=507–586

Goethite 5–5½ VHN100=667

Hematite 5–6 VHN100=1,000–1,100

Chromite 5½ VHN100=1,278–1,456

Anatase 5½–6 VHN100=616–698

Rutile 6–6½ VHN100=894–974

Pyrite 6–6½ VHN100=1,505–1,520

Bowieite 7 VHN100=858–1,288

Euclase 7½ VHN100=1,310

Chromium 8½ VHN100=1,875–2,000

Particle Interactions…

Particle – ParticleVan de Waals ForcesElectrostatic ForcesCapillary ForcesSintering ForcesCollisions

Particle – EquipmentFrictionShear Strength

Particle – EnvironmentHumidityTemperaturePermeabilityVibrationTime

Moisture Content

Increase cohesivenessInter-particle liquid bridge formation

Substantial effect on frictional properties of materials

Effects of Moisture on Flow in a Bin

0

2

4

6

8

10

0 10 20 30

Percent Moisture

Arc

hin

g D

imen

sio

n -

ft

Particle – Particle Interactions

Capillary Forces Sintering Process

Liquid Bridges! Solid Bridges!

Fc = 2πRγ ε n = ktR

Particle – Particle Interactions

Fνω = AR / 12a2

Fνω = hŵ 1+ hŵ__ 8πa2 8πa2H

Fνω =1 to 10eV (most solids)

Gravity Defiance!

van der Waals Forces

Particle – Equipment Interaction

Friction

InternalSolid particles flowing against each other

Angle of internal friction

WallSolid particles sliding along a surface

Wall friction angle

V = KΔФ A

σA

ζA

FR

Particle – Equipment Interactions

Particle – Environment Interactions

Particle – Environment Interactions

Time ConsolidationIncrease in strength when stored at rest under compressive stress for a long time interval

• Sintering• Plastic deformation at particle contacts• Interactive Forces!

σvA σcA

Stresses in Bulk Solids

Not a Newtonian Fluid!

Shear stresses can be transmitted even at rest

Shear stresses are different in different cutting planes

State of stress in a bulk solid cannot be completely described by a single numerical value

Compressibility

CohesionX

Y

Z

dy

dz

dx

σzz

ζzy ζzx

ζ xz

ζxy σxx

ζ yz

σ yy ζyx

σ = Stressζ = Shear

Permeability

Ability of gas to pass through the material

Gas Permeability

A measure of how easily gas flows through standing material

Relates to particle size, shape, and density

Why is important?Tendency for the bulk material to fluidize or “flood”

Pellets have high gas permeability and thus don’t easily flood

Fine fumed silica has poor gas permeability thus will flood easily as the sub-micron, light weight particles become entrained in the air stream

Compressibility

• The ability of the powder to be compressed within a specified container

• (NOTE: Carr used a 100 cc container

• The value is determined by calculating subtracting the Aerated from the Packed Bulk Density Measurements.

100 x100 x( Packed - Aerated )( Packed - Aerated )

Packed Bulk DensityPacked Bulk Density= % Compressibility= % Compressibility

Slide courtesy of Hosokawa Micron Powder Systems, Summit, NJ

Additional Laboratory Tests

Angle of Repose

Poured Angle

Angle of Spatula

Can Velocity

Terminal Velocity

Bulk Velocity

Fluidizability

Conveyor Equipment Manufacturers Association Guidelines CEMA Standard 550, March 26, 2009

Angle of Repose

PE pellets Shredded PS

Sugar Cycloserine

4.5 m.

Added Height58 cm.

3.9 m.

3 m. Dia.

3 m. Dia.

22 cu.m.

4 cu.m.

26 cu.m.

2 cu.m.

2 cu.m.

Water Fill Volume of this

bin28 cu. m.

Water Fill Volume of this

bin33 cu. m.

Angle of Repose (loose)

Intro here picture of pileWith angle of reposeConvert all these to metric

Can Velocity Can Velocity –the gas velocity within a specific

area

Can Vel = CFM/ABH

CFM = Gas volumeABH = Cross sectional area (of receiver housing, bag

house, etc)Interstitial Velocity – The apparent velocity of a gas as it passes by a filter bag matrix.

It is found by dividing the collector gas volume by its cross sectional area, after the cross sectional of the bags have been subtracted from the collector cross sectional area.

55.0%

0.0%

17.7%

89.0%99.7%

100.0%

0%

20%

40%

60%

80%

100%

0 100 200 300 400 500

Below 100 FPM

Can Velocity

Kinematic Angle of Surface Friction

Particle to Wall Friction

’

Pressure or Force

Kinematic Angle of Friction

F┴

F║

Loose Drained Angle

Calculate the volume of the inverted cone created during discharge.

Determine silo effective usable space, from low level signal

Determine where the low level indicator should be located

Usable refill area.Placement of low level indicator.

Four Basic Categories of Flow TypesFloodable

When mixed with air/gas become highly charged like a fluid

Difficult to handle. Flows freely

Flows across conveyor belts and screws faster than the speed

CohesiveCompressible material. Packs easily

Sticky

Hygroscopic

Easy flowingFree-flowing. Does not stick together

Uniform particle size and shape

Does not absorb air/gas and become fluidized

Difficult flowingMaterial tends to mat together (strings)

Non-uniform particle size and shape

Fragile

Coarse or abrasive

Over the years, in an effort to reduce human subjectivity while performing the Carr methods, instruments have gone from strictly manual to computer assisted operation.

Powder Tester for Flowability

Slide courtesy of Hosokawa Micron Powder Systems, Summit, NJ

Flowability as per the Ralph Carr series of Indices

41

Slide courtesy of Hosokawa Micron Powder Systems, Summit, NJ

Floodability as per the Ralph Carr series of Indices

42

Slide courtesy of Hosokawa Micron Powder Systems, Summit, NJ

Summary: General Scale of Flowability

Flow Characteristic Compressibility Index (%)

Hausner Ratio

Excellent ≤ 10 1.00 – 1.11

Good 11 - 15 1.12 – 1.18

Fair 16 - 20 1.19 – 1.25

Passable 21 - 25 1.26 – 1.34

Poor 26 - 31 1.35 – 1.45

Very Poor 32 - 37 1.46 – 1.59

Very, very poor > 38 > 1.60

Source: Carr. R.L. Evaluating Flow Properties of Solids. Chem. Eng. 1965, 72, 163 – 168

Questions?