solids handling in the chemical company -...

Solids Handling in The Chemical Company

Dr. Hermann J. Feise1)

DI Thomas Letzelter2)

1) Science Relations 2) Process Systems Engineering

124.09.2012

2Dr. Hermann J. Feise, GOH/C Science Relations and Innovation Management24.09.2012

Solids Handling

Bulk Solids Characterization

Flow properties

Shear testers

Design of Storage Silos

Gravity fed storage systems

Flow promoting devices

Conveying of Bulk SolidsScrew conveyors, pneumatic conveying

Storing and Conveying of Bulk Solids

Being an Engineer in IndustryThe phone call

4:30 pm a customer calls

A new factory for our product „Powdery White“

Can you design the handling and shipping facilities for us?

YES, ......

Oh, and we have two grades, the fine and the instant product.

What question do you ask?

…

…

…

…

…



Merrow (1986): “use of solids in a process is the most prominent factor causing delayed start-up”

Merrow (1998): “things did not get better”

delays of up to 18 month

process predictions of solids processes are inferior to fluid - processes

Particle technology is becoming increasingly important

The Role of Particle Technology


Characterization of Bulk Solids: Bulk Solids are NOT like liquids

Gravel Baking powder

Vitamin powder Cement

Flow under gravity

Surface

Liquid: level

Bulk solids: angle of repose

Flow

Liquid: incompressible

Bulk solids: dilatant

Storgae pressure

Liquid: hydro static

Bulk solids: Janssen - effect


Bulk Density – Bulk Solids Density

Flow properties, packaging

NOT a material constant

Depends on compaction, shaking, electro static conditions...

Tapped density / bulk density = Hausner number

Different countries – different standards – different bulk densities

Fülltrichter

Bodenklappe

MeßbecherPrüfgerät zur Schüttdichtebestimmung nach DIN 53466

Feed hopper

Knife valve

Graded cylinder

Device to determine the bulk density acc DIN 53466


Bulk Solid PropertiesJanssen - Effect

= lateral stress ratio = h/v

x = external or wall friction angle

U = circumference

A = cross sectional area

Janssen (1895)

v A

v + dv) A

g b A dz

w U dz

h U dzdz

z

vh

Hydro static

xhw

zA

U

tan

e1UA

x tan

x

bv tan

g4D

w


Reversion of frictional force!

v A

v + dv) A

g b A dz

w U dz

h U dzdz

z

v

1eUA z

AUx tan

x

bv tan

g

Bulk Solid PropertiesJanssen - Effect


250

200

150

100

50

00 100 200 300 400 500

Curve (1) Theoretical

Curve (2) ExperimentalMillet Vcon ? 30 mm/s

Forc

e -N

Column Length - mm

Force to Convey Millet seed Vertically through a 45 mm Acrylic Tube

© P. Arnold, U Wollongong


Bulk Solid Properties: Virtual Experiment

1

1

22

fc

fc

Cylindrical sample with fricitonless supports

Compaction with lateral support Consolidation stress

1

Bulk solid density b

‚shear‘ No lateral support Uni-axial compressive

strength fcConsolidation Shear


Bulk Solid Properties: Ringschergerät

Current industrial standard

Ring Shear Tester RST-01pc

Sample size: 200 bzw. 900ml

Automatic control

‚unlimited‘ travel

Several data points per sample

Suitable for products with x95< 4 mm

http://www.dietmar-schulze.de/fre.html

Lid

Tie Rod

Tie Rod

Guard Roll

Guard RollShear Cell

Cross Bar

Bulk Material

N

S

S


S

S

S

travel

travel

travel

Over-consolidated sampleMaterial flows under dilation

Well pre-sheared sampleMaterial flows under constand volume, no compaction

Under – consolidated sampleMaterial keeps compaction during shear

Shear test vs. Travel diagram

N =normal force, S = shear force

Shear Test


Test Evaluation acc. Jenike

2 fc

i e

c Cohesion

E

Internal friction angle

Sha

er s

tres c

1Normal stress

Plastic deformation

i = internal friction angle

e = effective angle of internal friction

fc = uniaxial compressive strength

1 = major principal stress (axial)

2 = minor principal stress (radial)


S

N Past industrial standard

Sample size: 600 ml

Material requirement: 3 - 15 Liter

Max. travel <= 5mm

Suitable for materials with x95< 4 mm

Bulk Solid Properties: Jenike Shear Cell

N = normal force, S = shear force


Bulk Solid Properties: Walker Ring Shear Cell

Walker Ring Shaer Tester

Sample size: 2 Liter

‚unlimited‘ travel

Several data points per sample

Suitable for products with x95< 4 mm

Probenbeheizung bis ca. 80°C

TI

N el. Beheizungu. Isolation

Deckel

S

Meßhebel (fest)

ProduktprobeRingzelleel. Beheizungu. Isolation

Antrieb


Compaction Shear

52.55

Lower PistonLower Punch

SampleShear Plane

Ledge

46.63

41.48

Die

Outer Piston

Inside Piston52.40

44.32

23*

Bulk Solids Properties: Johanson Hang-Up Indicizer


Flow Profiles and Flow Properties

Mass Flow Funnel Flow Arching Ratholing

Dead zone

Flow channel


1

1

Compaction with cohesive products

Jamming with coarse, non cohesive products

Types of Arching


Cost of Method [£]

Prob

ability of S

uccess [%

]

Phon

e call, letter

Book, jou

rnal

Seminar, sho

rt visit

Feasibility stud

y

Shear test

Pilot p

lant te

sting

Full scale testing

0

20

40

60

80

100

0,1 1 10 100 1000 10000 100000

Quelle: H. Wright, bulk solids handling, 8(1988)5, 627-628

Process Engineering Silo Design


Silo Pressure Profiles

Material element

D

H

h* 1= fckrit

dmin

1

1fc

1

Hydrostatic pressure of a liquid

fc, 1, 1

1 = major principal stress1 = embankment stressfc = uniaxial compressive

strength at 1


Silo Stresses

wa. b. w

wc. wd.

a. Filling stateb. Beginning dischargec. Mass flowd. Funnel flow

Quelle: J. Schwedes, TU Braunschweig 1985


Silo Design acc.to JenikeRepresentative sample

Operating Conditions

Wall material

Storage time

Storage temperaturehumidity

.

.

.

Silogeometry

Design for mass flow

or

Hopper angle

Silo shape

Storage volume

Mass flow angle

Sheartesting

Wall frictionµ = tan(x)

Bulk solids density

b

Friction anglee, i

Flow function, time flow function:fc ÷ 1

Hopper angle

Pressure distributionin hopper Critical stress conditions

Minimum outlet size against arching and ratholing

Jenike - Method(Bulletin 123)


Silo Design: Mass Flow – Funnel Flow Boundaries

Axial-symmetric Silo Plane Silo

Quelle: DIN 1055, Beuth Verlag 2005

Funnel Flow FunnelFlow

Mass Flow possible

Mass Flow possible

DIN 1055: 2005

Hopper inclanation

Hop

per w

all f

rictio

n co

effic

ient

h

= ta

n x

Hopper inclanation

Hop

per w

all f

rictio

n co

effic

ient

h

= ta

n x


Silo Design: Mass Flow – Funnel Flow Boundaries

DIN 1055: 1984

Quelle: DIN 1055, Teil 6; Beuth Verlag 1984

Axial-symmetric Silo Plane Silo


Silo Desgin: Silo Shapes

Dmin

ax

D

H

ax eben

H

B

Bmin

eben

H

B

Bmin

L > 3 * Bmin

L

Axial-symmetric pyramidal plane

steep Less steepsteep


*STUDY BY TERBORG OF 500 SAMPLES

Mass Flow Angle*

100

80

60

40

20

00° 10° 20° 30° 40°

Hopper angle (axial-symmetric hopper)

% p

ropo

rtion

odf

hop

pers

with

mas

s flo

w

axc

c


Flow Promotion – not this way

© BASF SE, 1999

Silo Design: Silo Discharge for Mass Flow

Flow properties

Storage time

Silo Shape


Dmin/D

ax

15°

30°

0,5

4m

Rotary valve

Vibrating hopper

Scraper

Live Bottom


Silo Design: Minimum Silo Outlet and Time consolidation

Mass Flow Silo

Maximum stoppage time: 3 days (week end)

Continuous discharge

Flow promoters

conveyor

Flow promoter, continuous

Flow promoter after prolonged stoppage

Alternative: Recycling

Dmin(3 d)

Dmin

DAus

Gravity flow

Flow promoters, short term

Discharge device

Conveyor


Mechanical Conveying: Screw Conveyors

Principle:

Screw helix moves through the material

50 - 200 rpm

Operational conditions

L < 6 m, no intermediate bearing

L < 60 m , intermediate bearing

Horizontal, vertical,

tilted (<30°)

Several feed or discharge ports

Closed system (inert atmosphere)

No bends (exception: flexible screw conveyors)

Single and multiple screws

Additional features

Heating, cooling, mixing, homogenizing, degassing …


Mechanical Conveying: Flexible Screw Conveyors

Screw without core (pig tail) rotates in a flexible casing (plastic hose)

Advantages Low investment cost Can manage one bend Horizontal or vertical

Disadvantage Low capacity (DN200: 40 m³/h) L < 15m; H < 12m High rotational speeds Wear of casing and helix

(Ermüdungsbruch) Incomplete discharge


Mechanical Conveying: Vibratory Conveyors

Models Electromagnetical vibratory conveyors

– Non balanced mounting– L < 6m

Isolated counterbalanced vibratory conveyor

– Heavy (balancing weights)– L = 6 - 30 m possible– Q > 100 to/h

Products Suitable for: hot, abrasive, dusty Nor sited for: cohesive, tacky

Design Several feed and discharge ports horizontal up to ±5° No bends


MaterialClass

1 2 3 4 5

Powder sluggish100 –300mesh

Powdersluggishadhesive (incl. class 1 when damp)

Powder sluggishfluidizes3 – 325mesh

Granualrfree-flowing>100 mesh> 25 Ib/ft3

Fibrous, flaky, floccu-lent

Large particlesSizes> 3˝

Abrasive solids

High temp-era-ture

Belt conveyor

Vibratory conv

Drag chain c.Redler conv

Plastic elevator

Screw conv.Flex screw converyor

Drag disc conv. AeroMech

Bucket elevator


Belt Conveyor

Drag chain conveyor

Drag disc conveyor

Screw conveyor

Vibratory conveyor

Aeromechanical conveyor

Flexible screw conveyor

Screw feeder without intermediate bearings

30 60Conveying distance [m] 100 150

Feed

er /

Con

veyo

r


Pneumatic Conveying Principle

Discharge air

Pressureizedair

Product

PI

Ambient air Feed port

Silo with filter unit


Geldard diagram of fluidization

10000

5000

2000

1000

500

200

10010 20 50 100 200 500 1000 2000 5000

Mean particle size dp [µm]

Den

sity

diff

ernc

e (

s– F

) [kg

\m

3 ]

Group C

Group AGroup B

Group DDiagram acc. to Geldart, boundaries acc. to Molerus


Pneumatic Conveying StatesHorizontal Conveying

Dichtstromförderung Dünnstromförderung

DruckförderungstabilerVollrohr-/Kolben-

Saug- oder Druckförderung

Instabiler stabiler FörderbereichKolben- / Dünen- / FlugförderungDünen-

ruhendeSchüttung

Gutdurchsatz

log (mittlere Gasgeschwindigkeit)

Leerlaufkurve

log

(bez

ogen

er D

ruck

verlu

st/L

änge

nein

heit)

vmin v *

c)d)

f)

e)

pmin

b)

a)

MS3MS2MS1MS0= 0MS = 0.

MS3 > MS2 > MS1. . .

. . . .

Dichtstromförderung Dünnstromförderung

DruckförderungstabilerVollrohr-/Kolben-

Saug- oder Druckförderung

Instabiler stabiler FörderbereichKolben- / Dünen- / FlugförderungDünen-

ruhendeSchüttung

Gutdurchsatz

log (mittlere Gasgeschwindigkeit)

Leerlaufkurve

log

(bez

ogen

er D

ruck

verlu

st/L

änge

nein

heit)

vmin v *

c)d)

f)

e)

pmin

b)

a)

MS3MS2MS1MS0= 0MS = 0.

MS3 > MS2 > MS1. . .MS3 > MS2 > MS1. . .

. . . .

Dense Phase Conveying Lean Phase Conveyingpressure‐ or vacuum conveying

Stable plug flow Instableplug flow

Solids conveying rate

Air only

Granular bed at rest

(log) mean gas velocity, v

(log) re

lative pressure drop, p/l

Stable dispersion flow


Pneumatic Conveying: Air flow controller

Dense phase conveyor (Roto-Conveyor or pressure vessel system)

Laval nozzle with variable nozzle geometry

Almost constant air flow rate (ideal pump characteristic) at all pressure levels up to the supply pressure

Suitable for explosion protection areas (no ignition sources)

Can supply systems with various discharge ports and conveying distances (routing and run length) Q [m³/h]

p

[mba

r]

VentilatorCompressorAir flow controller

Fa. Waeschle

Being an Engineer in IndustryThe phone call

4:30 pm a customer calls

A new factory for our product „Powdery White“

Can you design the handling and shipping facilities for us?

YES, ......

Oh, and we have two grades, the fine and the instant product.

What question do you ask?

Product Split, Production capacity

Product Data

Storage Volume, Storage Time

Packaging (bags, Super Sacks, loose)

What do you suggest to do?

…

…

…


solids handling in the chemical company -...

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