Prof. Dr.-Ing. habil. J. Tomas – chair for Mechanical …PPPS/Fig...pelletizing A – feed material (for agglomeration), Q heat flow b) press agglomeration (compaction) in partially

Fig_PC&P_6 Lecture Product Characterization and Processing of Pharmaceutical Particulate Solids, flow promotion devices, Jürgen Tomas 31.05.2013

Figure 6.0 Prof. Dr.-Ing. habil. J. Tomas – chair for Mechanical Process Engineering 6. Design and selection of flow promotion devices 6.1 Flow additives (glidants and lubricants) 6.2 Size enlargement (agglomeration) 6.3 Flow promotion devices …


Figure 6.1 Prof. Dr.-Ing. habil. J. Tomas – chair for Mechanical Process Engineering

Measures and Flow Promotion Devices to avoid Bridging and Chanelling

Flow promotion devices objectives

Increas-ing flow channel

Avoid channel-

ling

Avoid bridging

Improve flowability of powder

Flow additives (anti-caking agents, glidants, lubricants…)

X X X

Size enlargement (agglomeration, pelletizing, tabletting)

X X X

Wall liners and coatings

Slippery paints, wall coatings X X - Rigid plates X X - Flexible walls (X) (X) X

Rigid inserts Cone, roof, beams, grid, bin X X - Pneumatic flow promo-tion devices

Continous aeration (pneumatic bottom or bin)

X X X

Bin cushion, aeration tube, box, whistle

- (X) X

Rapid aeration in batch (nozzles, lance, cannon)

- X X

Gas shocks waves by explosions - X X Oscillating devices

External vibrator, rapper, knocker - (X) X Internal vibrating grid or cone (X) (X) X Soil penetration rocket - - X Oscillating bins X X X

Rotating devices

Flexible arm agitator - (X) X Beam, arm, plough, plate agitator (X) - X paddle shaft (X) - X

Feeders with flow promotion function

Arm agitators in convergent or divergent hoppers

X X X

Rotary plough feeder (bunker dis-charge wagon)

X X X

Transverse driven screw feeder X X X (X) partially effective


Figure 6.2 Prof. Dr.-Ing. habil. J. Tomas – chair for Mechanical Process Engineering 6.1 Flow additives (glidants and lubricants)

Effect of flow additive on heap formation of a technical herbicide

Herbicide with 0.3% Aerosil Herbicide with 0.9% Aerosil

Consolidation functions σc = f(σ1) and time consolidation function of herbicide

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Eina

xial

e D

ruck

fest

igke

it σ

c[k

Pa]

Verfestigungsspannung σ1 [kPa]

0,3 Ma.-%

0,3 Ma.-% (24h)

0,9 Ma.-%

0,9 Ma.-% (24h)

ffc = 1

ffc = 2

ffc = 4

ffc = 10

ffc = σ1/σc flow function acc. to Jenike

Estimation of optimal guest particle size and their content:

Adhesion force ( )

⋅+

⋅+⋅= 2

0

g2

0g

hsls,H0H a

d2a2d

d24

CF

Guest particle size at FH0,min

0)d(d

dF

g

0H = →

−⋅= 2

adad 3

0

h0min,g

Load of guest particle at FH0,min

⋅−

⋅

ρ⋅

ρ⋅π=

⋅

⋅=µ

h

0

3/2

h

0

h,s

g,s

h

ggg d

a2da

2m2mn



6.2 Agglomeration - Size Enlargement

Operation principles of agglomeration processes: a) tumble agglomeration (growth or agitation agglomeration)

pelletizing

A – feed material (for agglomeration), Q heat flow

b) press agglomeration (compaction) in partially open or closed die

• continuous sheets (ribbon)

• solid forms (tablets, briquettes)

c) sintering (thermal process)



Tumble Agglomeration (Pelletizing) 1. Balling drum and balling pan

a) balling drum b) balling pan A feed material P green pellets W water



Press Agglomeration Operation principles of press agglomeration : a) b) c)

a) in a closed die

b) in a open die

c) by roller pressure

A feed

B agglomerate

FP compaction or press force

FR wall friction force in the die

channel

h punch stroke length

l filling level (not compacted)

s thickness of compacted

material

k compaction (k=l/s)

β1 half of nip angle

1 punch

2 pressing die



pp

d) Plastic deformation of particles to create large contact areas

f) Plastic deformation of entire tablet

e) Breakage of edges, particle breakage, pore filling

p

p

b) Elastic-plastic contact deformation

a) Feed of loose packing

c) Pore filling by fine particles

p

h0

h(t)

h(t)

h(t)

h(t)

h(t)

Microprocesses and deformation mechanism at powder press agglomeration (compaction)

Compaction function of cohesive powder

com

pact

stre

ngth

lg(

σ T i

n M

Pa)

compaction pressure lg(p in M Pa)10-3

Tablet, briquette or ribbon strength σT

unia

xial

com

pres

sive s

tren

gth

σc

consolidation stress σ10

σc = a1 · σ1 + σ c,0

For hopper design

σT= f(p)


Figure 6.7 Prof. Dr.-Ing. habil. J. Tomas – chair for Mechanical Process Engineering 6.3 Flow promotion devices

Lining of BinsMaterial data of ultrahigh-molecular weight polyethylen

fastening

rounded edge profiles promote mass flow

no bulging bolts or edges!



Rigid Hopper Inserts

a) before

b

Θ

ΘG, con

b) Plate insert

b

bmin

Θ

c) Cone insert

ΘG

bmin, wedge

bmin, con

ΘG, wedge

d) Bin insert ("Binsert")

bmin, wedge

2 · ΘG, con

bmin, con

ΘG, con

ΘGΘG

ΘG hopper angle limit of the flow zone

flow zone

deadzone



Pneumatic Flow Promotion Devices

Druckluft

Druckluft

Druckluft

Druck-luft

Ruhe-stellung

Druckluft

Ruhe-stellung

Druckluft

Druckluft

poröser Boden

Druckluft

a) Fluidisation of whole bin b) Aeration bottom

c) Aeration box d) Bin wall cushion

e) Porous aeration tube f) Aeration whistle

g) Movable air lance h) Air cannon

porous bottom compressed air

compressed aircompressed air

compressed air

compressed air

compressed air

at rest

at rest



Air Pressure Shock Device (Air Cannon)

channelling piping (ratholing) bridging in hopperr in shaft

filling

compressed air

shock waveoutflow

rapid releasing valve

Arrangement of air cannons:



Vibrating discharge aids

a) Unbalanced motor at hopper wall (dashed lines: wall oscillations at high-frequency excitation f > 100 Hz)

b) Silo with flexible connected vibrating

hopper and conical deflector (Δx < 4 mm, f < 25 Hz)

Additional options for convex deflector and/or oscillating inserts (rods, cages, screens, flexible grids):

c) Matcon-Bules as

“valve” with low-ered cone (left) and with lifted and vi-brating cone by pneumatic excita-tion as discharge aid (right)

Kollmann, Th.: Schwingungsinduziertes Fließen feinstkörniger, kohäsiver Pulver, Diss. Otto-von-Guericke-Universität Magdeburg 2002



Arrangement of Discharge Aids at Time Consolidations

1. Minimum discharge width versus storage time at rest

bmin(tmax)

bmin(t1)

bmin,0

b2

0 t1 tmaxstorage time t

outle

t wid

th b

min

bmin(t) = bmin,0 + b∞· [1 - exp(- )] tt63

_

b) discharge aid necessary for t > t1

bmin(tmax)

bmin(t1)a) no discharge aid necessary

bmin(tmax)

2. Outlet design

no bridging for t < tmax

0

bmin(t1)

bmin(tmax)

bmin,0

b2

no bridging for t < t1

no bridging for t = 0

bridgingho

pper

hei

ght

y

bmin,0

bmin(tmax)

bmin(t1)c) discharge aid necessary for t > 0

b2

bmin(tmax)

bmin(t1)

bmin,0

d) discharge aid necessary for t > 0

e) discharge aid always necessary

see Schulze, D., Austragorgane und Austraghilfen, Chem.-Ing.-Techn. 65 (1993) 48-57

Documents

Prof. Dr.-Ing. habil. J. Tomas – chair for Mechanical …PPPS/Fig...pelletizing A – feed material (for agglomeration), Q heat flow b) press agglomeration (compaction) in partially