Binderless granulation –

Its potential and relevant

fundamental issues

Binderless granulation –

Its potential and relevant

fundamental issues

Masayuki Horio Tokyo University of A&T

Koganei, Tokyo

7th Intl. Symp. on Agglomeration

Tuesday 29, May 2001

25 min from Shinjuku

Nice place to escape

Koganei ?

time[s] 0 7200

15s 1s ② Compaction

interval

① Fluidizing

interval

② Compaction

interval ① Fluidizing

interval

(a) Test apparatus (b)Operation scheme

f 0.108m

0.41m

Bag filter

Air

Pressure Swing Granulation Nishii et al., U.S. Patent No. 5124100 (1992)

Nishii, Itoh, Kawakami,Horio, Powd. Tech., 74, 1 (1993)

Typical examples of PSG granules

PSG granules: weak but strong enough!

Change in PSD of PSG granules in realistic conditions

PSG

granules

from ZnO

dp=0.57m

slide

gate

after

1st fall

2nd fall

3rd fall

Particle size [10-6m]

C

um

ula

tive w

eig

ht [%

]

compaction and attrition

bed expansion

bubbling

fines‘ entrainement

air (in bubbling period)

pulse (in reverse flow period)

① ②

cake

filter cleaning & reverse flow period:

Cakes and fines are returned to the bed cleaning-up the filter, and

bed is compacted promoting agglomerates’ growth and consolidation.

bubbling period:

Bed expansion de-agglomerates and compaction, attrition and solids revolution make grains spherical.

Fines are separated and re compacted on the filter.

①

②

What happens in PSG?

distributor

#16-1 #16-1#30-1 #30-1

#16-2#16-2#30-2#30-2

#16-1#30-1 #16-2#30-2

500m

ZnO

PSG granules split by a needle show

a core/shell structure

Fig.5

E

Superficial gas velocity [m/s]

Me

dia

n d

iam

ete

r [m

1

0-6

]

0.1 150

1.0

1000

500

0.5

Effect of fluidizing gas velocity on da

Bu

lk d

en

sity o

f g

ran

ule

s [kg

/m3]

Maximum pressure difference for compaction [Pa104]

0.6

1.0

0.8

1.2

2.0 6.0 4.0 0

Factors affecting PSG granule density

w=0.4kg

0.2kg

with gas velocity

and solids charge

Possibility of size control by surface

modification

Polar-polar interaction

between adsorbate molecules

Me

dia

n d

iam

ete

r [

10

-

6m

]

Absorption time [h]

500

Me

dia

n d

iam

ete

r [

10

-

6m

]

300

400

500

293K,

4kPa

0 3 6 9 12

Me

dia

n d

iam

ete

r [

10

-6m

]

300

400

200

573K,

13.3kPa

0 3 6 9 12 Absorption time

[h]

Absorption time [h]

400

500

600

293K,

4kPa

0 3 6 9 12

Absorption time [h]

300

400

500

Med

ian

dia

mete

r [

10

-6m

]

573K,

13.3kPa

0 3 6 9 12

(a) C2H5OH (b) NH4OH

Mean size of PSG granules from TiO2 (0.27x10-6m) after heat treatment and surface modification

heat treatment:at p<13.3Pa

523K, for 6 hrs

adsorption:

bed= f150x10mm

in a 0.03m3 vacuum

dryer

PSG: charge=0.0333 kg

u0=0.55 m/s RH: 40-

50%

fluidiz.:15 s comp.: 1 s

total cycles=450

adsorption at:

p(adsorbate):

Nishii & Horio (Fluidization VIII, 1996)

Notes: At 573K all

hydroxyl groups

on TiO2 are

eliminated

(Morimoto, et al.,

Bull. Chem. Soc.

JPN, 21, 41(1988).

Highest heat of

immersion at 573K

(Wade &

Hackerman, Adv.

Chem. Ser., 43, 222,

(1964))

No effect: desorbed

during PSG

No effect ??

Agglomerate 1

Powder 1 Powder 3 Powder 2

Agglomerate 2 Agglomerate 3

feed compositions

powd. dp(WC) WC Co wax*

x10-6m %wt %wt %wt

1 1.5 93.0 7.0 0.5

2 6.0 85.0 15.0 0.5

3 9.0 77.0 23.0 0.5

dp(cobalt)=1.3-1.5x10-6m

*) Tmp(wax)=330K

preparation: 1. grinding 2.5hr 2. vacuum drying PSG: Dt=44mm charge=150g u0=0.548 m/s P(TANK)=0.157 MPa total cylces=64 Hard Metal Application

SEM images of feeds and product granules

Application to hard metal industry

Improved strength of sintered bodies

PSG

method

convent-

ional

method

T

ransvers

e r

uptu

re s

trength

[N

/mm

2]

Co content [wt%]

L : E=1 : 0

500m

L : E=0 : 1

500m

L : E=3 : 7

500m

L : E=1 : 1

500m

L : E=7 : 3

500m

10m

L : E=0 : 1

10m

L : E=3 : 7

10m

L : E=1 : 1

10m

L : E=7 : 3

10m

L : E=1 : 0

top: PSG granules; second line: surface of agglomerate

(SEM)

Co-agglomeration of lactose and

ethensamide

0.01 0.03 0.1 0.3 1 3 10 30 100 10

20 30

50

100

200 300

500

1,000

Iwadate-Horio Chaouki et al.

Morooka et al.

u 0 =0.5m/s

0.3 0.5 1 2 3 5 10

20

50

100

200

500

1,000

2,000

5,000

u 0 =0.5m/s Morooka et al.

IHM

Chaouki et al.

0.01 0.03 0.1 0.3 1 3 10

20

50

100

200

500

1,000

2,000

u 0 [m/s]

0.01 0.03 0.1 0.3 1 3 0.005

0.01

0.02

0.03

0.05

0.1

Morooka et al.

IHM

Chaouki et al.

u 0 =u mf

bubbling bed

fixed bed

da [

m]

da [

m]

da [

m]

Da [

m]

(a) Effect of primary particle size

(b) Effect of Hamaker const.

(c) Effect of u0

dp [m]

Ha [J]

(IHM)

Comparison of model performances

Bubble size

Comparison of model predictions with observed data

d a,

ca

lc [m

]

0E+0

2E-4

4E-4

6E-4

8E-4

1E-3

1.2E-3

1.4E-3

0E+0

2E-4

4E-4

6E-4

8E-4

1E-3

1.2E-3

1.4E-3

Lactose

ZnO

L:E=7:3

L:E=1:1

L:E=3:7

d a,obs [m]

Model (IHM) works !

Ha=0.4x10-19J Ha=1.0x10-19J Ha=2.0x10-19JNon-cohesive*

Agglomerate: Fcoh>Frep, max

Collision: Fcoh<Frep, max

Numerically determined agglomerates Kuwagi-Horio(2001)

Particle pressure around a Davidson’s

bubble

dp=100m, p=3700kg/m3

u0=0.1m/s, Ha=1.0×10-19J

0.411s 0.430s 0.450s 0.469s 0.489s

High particle normal stress right below

a bubble (Kuwagi-Horio(2001))

Authors External force/energy

Ekinetic =mumf /22

shearElaminer =3umfda2

Fpp

Fcoh,rup

FGa

v=umf

expansion

Chaouki et al.

Morooka et al.

Iwadate-Horio

Cohesion force/energy

6

FGa = da

ag

3

Fexp =Dbag(-Ps)da

2

2nk

exp = - Ps

Fcoh,rup =24

2

Hada(1-a)

Model

FGa = Fpp

bubble

Fpp =16

2

hwdp1+[ hw

8 Hr

2 3 ]

Comments

Esplit =hw(1-a)da

2

32

adp

2

Esplit

Etotal

Etotal=(Ekin+Elam) =Esplit

Etotal=(Ekin+Elam)

Fexp = Fcoh,rup

No bubblehydrodynamiceffects included.

If 3umf <hw(1-a)

/(32dpa),negative da isobtained.

Force balance

Energy balance

Force balance

gravity force≒drag forcevan der Waals forcebetween primary particles

laminar shear + kinetic forceenergy required tobreak an agglomerate

bed expansion force cohesive rupture force

No bubblehydrodynamiceffects included.

Bed expansionforce caused bybubbles isequated withcohesive ruptureforce.

Comparison of previous model concepts

1E-6 3E-6 1E-5 3E-5 1E-4 3E-4 1E-3 3E-3

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

A

B

F coh,rup = H a d a (1- a )

24 2

F exp = 2n k

D b a g(-Ps)d a 2 ^

stable point

fluidized

unstable point

easy to

defluidize

(a) example force balance and

two solutions

log d a [m]

log

F[N

]

1E-6 3E-6 1E-5 3E-5 1E-4 3E-4 1E-3 3E-3

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

C

saddle point

(b) Limiting size of agglomerates

log d a [m]

log

F[N

]

The critical condition

Force balance of I-H model

and the critical solution