Introduction Many products are manufacturing through compaction of - - PowerPoint PPT Presentation
Charley Wu Chemical and Process Engineering University of Surrey, Guildford, UK 0 @charleywu @ C.Y.WU@surrey.ac.uk Introduction Many products are manufacturing through compaction of dry powders, involving powder flow into a confined space.
Charley Wu Chemical and Process Engineering University of Surrey, Guildford, UK
Many products are manufacturing through compaction of dry powders, involving powder flow into a confined space.
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·Pharmaceutical ·Catalyst
·Chemical , •Ceramic , ·Magnetic ·Food
UNIVERSITY OF
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Upper punch
compacts I
I
Lower punch I
..........................
Die Filling Compaction Ejection
Any problem during die filling will have a direct impact on the quality
Failure during die filling can lead to
functionality
as sintering.
"If your doctor prescribed half a tablet a day, which half would you want to take? "(Malvern Instruments} 2008).
D A combined experimental and numerical approach was employed to understand the die filling process. D A model die filling system was developed. D Die filling behaviour was visualised using a high speed video system. D Quantitative analysis was also performed using
mass.
D Mechanistic analysis was performed using DEM-CFO
SUNUIVERRRSITYEYOF
High speed video
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Air pressure sensor
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Mass pressure sensor
32 34 38 38
Time (s)
(Positron Emission Particle Tracking)
30 trajectories of individual particles
UNIVERSITY OF
Spherical microcrystalline cellulose ( Celphere, CP102 )
Initial position of the shoe
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6
Wu, C.-Y., X.F. Fan, F. Motazedian, J.P.K. Seville, D.J. Parker, A.C.F. Cocks, (2010). A Quantitative Investigation of Powder Flow during Die Filling Using Positron Emission Particle Tracking (PEPT). Proceedings of the Institution of Mechanical Engineers, Part E, Journal of Process Mechanical Engineering. 224(3): 169-175.
The flow of particles is modelled using DEM.
The interaction between particles are rigorously modelled using theoretical contact mechanics:
elastic particles
The interaction between air and particles is considered. The flow of air is modelled using CFO. Particle equations of motion: 8(Epf)
at
8(Epfu) + '\7.
fUU )=
at
Epfg
D Validation of DEM models is important. D Qualitatitive validation is easy, is it convincing? D Case-to-case quantitative validation is difficult.
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8 •
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Experimental DEM-CFO
JOURNAL, 59 (4), pp. 1075-1087
D Multi-sphere -> approximate particle shapes using clumped spheres. D Utilize the rigorous contact laws for modelling particle-particle interaction
Real crystal DEM approximation
3 , dP =50 µm
06~0
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0.50 0.40 0.30- 0.20 0.10 0.09
According to Beverloo equation, M* is in the range of 0.55-0.65.
.A. In vacuum ~
ln air ]Group 1
1-n air
}Group 2
e In vacuum
Q In air
)Group3
T In vacuum }
\J Jn air
Group 4
......... Constant in vacuum
1~
10
4
I ~10
6
I~
10
8
At<P
p
Normalised mass flowrate
Normalised particle density
<I>
= Ps
P
Pa
Archimedes Number
Pa gi p
r
1]2
This is in excellent agreement with Berveloo constants obtained experimentally (C is in the range of 0.55-0.65, for spherical particle c~0.58, see Seville et al. 1997).
Guo Y., Kafui K.D., Wu C.Y., Thornton C. and Seville J.P.K., (2009), A coupled DEM/CFO analysis of the effect of air on powder flow during die filling. A/CHE Journal, 55
(1 ): 49-62.
0.70~ 06~0
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.... ~
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....
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0.50 0.40 0.30 0.20 0.08 3
10
Air sensitive
!:;::. Jn air }Group I
0 In air
}Group 2
e In vacuum
0 ln air
}Group 3
T In vacuum }
'7 1
. Group4
v n atr
......... Constant in vacuum
Ar" </J
p Air inert
Guo Y., Kafui K.D., Wu C.Y., Thornton C. and Seville J.P.K., (2009), A coupled DEM/CFO analysis of the effect of air on powder flow during die filling. A/CHE Journal, 55
(1 ):
49-62.
(Fine sand, Vshoe=300 mm/s) (MCC, Vshoe=50 mm/s)
In Air ,.-~
,In Air ~-=-
V=35 mm/s V=70 mm/s
0.8
~
0.6
.....
~ ;...,
.......... ..........
~
0.4
0.2 I I
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0 In air
8 =(99 .33/v )1 68
shoe
/
8 =(4 7 .26/v )
119 shoe
50 100 150 200 Shoe speed v 1 (nun/s)
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D There is a critical filling speed during die filling, above which the die cannot be completely filled. D The critical filling speed is a function of powder properties, and process system parameters D For a given process system, the critical filling speed is dominated by powder
used to assess powder flowability.
C11t1cal Ftllu1c Spet-!d •
nu11 ~ •
200
CP30:'
Flo\'\' Ftu1ction 50 .
.\.ng.J.e of
repose
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Good flowability Poor flowability
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Mix2 Mix3
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Model
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~a
Mt
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10 100
D
100
200
300 400 500
200 400
600
800 Filling speed (mm/s) Fiming speed (mm/s)
(a) (b)
60 40
so
Model
Ga 40
30
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...,
ftl ftl
::!: 20 ::!:
10
200
400
600
D 50
l!.00
150
200 250 Flllng speed (mm/s) Filling speed (mm/s)
(c) (d)
The variation of the deposited mass with the filling speeds for a) Silibeads 300; b) Cenopheres 500; c) Mannitol and d) Alumina 4.
300 250 200
S300
>
100
I C500
so
Mann1to9
MCCOG
11
1.E+o3
1.E+o4
1
.. E+os
1.E+06 1.E+07
1
.. E+o8
1.E+o9 1.E+lO
The critical filling speed obtained in the closed die experiments as a function of~
(=Ar.<J>)
Ar= PaPsgd;
<I>= PP
')
rr
Pa
D Powder into a confined space depends upon powder properties, die geometry and filling conditions. D The influence of air presence can be significant. D DEM-CFO is capable of capturing the major features during die filling. D Critical filling speed could be used to characterise powder flowability. D Based on air sensitivity classification obtained by Guo et al. (2010), a model was developed to predict the deposited mass and the critical filling speed.
EPSRC IFPRI AstraZeneca Sanofi Pfizer
Engineering and Physical Sciences Research Council