continuous crystallisation is right here and right no crystallisation is right here and right now...
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Continuous crystallisation is right here and right now
Professor Xiong-Wei Ni, BSc, PhD, CEng, CSci, FIChemEProfessor Xiong-Wei Ni, BSc, PhD, CEng, CSci, FIChemENiTech Solutions Ltd
10 Cammo Place, Edinburgh, Scotland
www.nitechsolutions.co.uk
Paris, 3rd October 2010
Structure
1. Crystallisation science
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2. Challenges in industrial crystallisation
3. Continuous oscillatory baffled crystalliser
4. Case studies
5. Forward remarks
Detail from an 1850 drawing of the London sugar refineries of Messrs. Fairrie and Co showing a copper crystallising pan for sugar.
The worker to the right of
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The worker to the right of the pan is holding a mallet that was used to bang on the pan to induce nucleation of the crystallisation process –Book of Joel
• Crystallisation is a relatively simple process
• But the governing science is not well understood
• In industrial scales, operators’ experience still plays a major part
Under-saturated
Solubility
Metastable Zone (MSZW)
Concentration
Supersolubility
Labile
Crystallisation “pathway”
1. Crystallisation Science1. Crystallisation Science
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part
Supersolubility is thermodynamically not found and kinetically not well defined, depending on:
Temperature
• Temperature profile• Rate of generating supersaturation• Solution history• impurities• Fluid dynamics
Scale dependent parameter
Ulrich & Strege, J. of Crystal Growth, Vol.237, p2130-2135, 2002
Science
Supersaturation
Concentration
Temperature
Cooling profile
Mixing
Solvent/additives
Seeding
Crystal size and shape
Morphology
PurityProcess
ProductProduct
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Nucleation mechanism
Nucleation rate
Growth mechanism
Growth rate
Seeding
Science
Functionality (materials)
Bio-availability (drugs)
Surface activity (catalysts)
Texture (foods)
• Secondary nucleation
– attrition, seeding
Nucleation•What initiates primary nucleation?
• not well understood
• 3-D assembly of molecular clusters on nm scale
• very fast kinetics On-set nucleation
• very fast kinetics
• not easy to detect Tsat
On-set dissolution
nucleation
Tcry
crysat TTMSZW −=
Detection of post-nucleation
concentration = 30 g/L, cooling rate = 0.5 oC/min
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MetastableMetastable zone width (MSZW) zone width (MSZW) MSZW depends on reactor, scale and operating conditions
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concentration = 45 g/L, f = 2 Hz, xo = 10 mm
• Dissolution – a thermodynamic process
• Crystallisation –a kinetic process
•Mass transfer control (mixing dependent ) or surface integration control (less mixing dependent)
• Crystal growth phase must take place within the MSZW
Crystal growth
Metastable
Crystallisation “pathway”
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• Nucleation dominates ���� small crystals
• Growth dominates ���� large crystals
Under-saturated
Solubility
Metastable Zone (MSZW)
Temperature
Concentration
Supersolubility
Labile
• Nucleation via collision breeding:
• Walls of vessel
• Free surface of liquid
• Internals, e.g. stirrer, baffle
• Impurities, e.g. particulates,
Mixing affects
0
5
10
15
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25
30
35
0 5000 10000 15000
Reynolds Number, Re o [-]
MS
ZW [
oC
]
30g/L 0.5°C/min
35g/L 0.5°C/min
30g/L 2.0°C/min
35g/L 2.0°C/min
200
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• Impurities, e.g. particulates, seeds
• Crystal/crystal & crystal/vessel collision
• Inhomogeneities due to mixing
0
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60
80
100
120
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180
200
0 5000 10000 15000 20000 25000 30000
Reynolds Number, Re o [-]
Cry
stal
Siz
e [
µµ µµm]
30g/L 2.0°C/min
35g/L 2.0°C/min•MSZW
• Crystal size distribution
Crystal Size
Supersaturation
MSZW
PolymorphicForm
ProcessConditions
Shape
Crystal Size
Polymorphic
Supersaturation
Shape
MSZW
Growth Kinetics Nucleation Kinetics
PolymorphicForm
ProcessConditions
Shape
Hydrodynamics Heat Transfer
Chemicals Behaving Badly (CBB)Chemicals Behaving Badly (CBB)
Crystal Size
Supersaturation
MSZW
Growth Kinetics Nucleation Kinetics
FTIR
USSUV Vis
PolymorphicForm
ProcessConditions
Shape
Hydrodynamics Heat Transfer
VideoMicroscopy
PIV/LDAReactionCalorimetry
Flow thruXRD
CFD
Courtesy of Dr White, Heriot-Watt University
• Simultaneous multi-technique measurements during a crystallisation process
• Have promoted better understanding of crystallisation in lab scale
Lab scale batch crystallisation
• Promoted better operation of crystallisation in small scale
• Linear cooling identified as one of the key operational parameters
• Data rich
• Lack of correlations between data
• Disturbing flow conditions
• Our understanding in scaling up STR is limited
• There is no agreed rule or parameter on scaling
2. Challenges in industrial crystallisation
− Tip velocity of impeller− Mean velocity− Averaged shear− Ratio of diameter to height
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− Ratio of diameter to height− Geometric direct− RPM− STR Reynolds number− Power density− CFD
• Velocity gradient or non-homogeneity increases with scale
•Mixing gradient leads to temperature and mass gradient
ScaleScale--up of stirred tanksup of stirred tanks
Laboratory
Industrial scale
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Mixing cannot linearly be scaled in STR
Kinetic control
Mass/heat transfer control
Heat Transfer on ScaleHeat Transfer on Scale--UpUp
Volume (m3) Area (m2) Area / unit Volume (m2/m3)
Typical 90 litre STR
0.09 0.9 10
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Specific heat transfer area decreases with scale
Typical 6500 litre STR
6.82 15.8 2.3
Industrial batch crystallisation
Inconsistent morphology
Wide size distribution
Mixing
gradient
Concentration
gradient
supersaturtion
gradientpolymorph
MSZWConcentration
∆∆∆∆C
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Temperature
gradient
MSZW and
Crystallisation path
nucleation
& growth
Polymorph
& size
Wide size distribution
Difficult to filter
Temperature
∆∆∆∆
∆∆∆∆T
Practical issues
• Linear cooling (oC/min) is difficult to achieve in large STR
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• Implementation of lab measuring techniques is practically impossible in industrial scale
i) consistent product quality can only be achieved in plug flows;
ii) it is very rare to obtain plug flow conditions in
From the viewpoint of fluid mechanics
3. Continuous crystallisation
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ii) it is very rare to obtain plug flow conditions in batch STR!
iii) Plug flow conditions can only be attained in continuous operation.
a) Use a series of CSTRs
…
b) Employ a tubular reactor
The conventional ways to achieve plug flow include
© NiTech Solutions Ltd, 2010
…
..
Plug flow is achieved when the number of CSTRs goes to infinite
Significant increase in inventory, running & capital costs, yet far from plug flow
Near to plug flow is obtained operating at turbulent flows
Significant high flow rates lead to very long reactor length, very short reaction time and high costs
Oscillatory baffled reactor (OBR)
Demonstration of radial mixingDemonstration of radial mixingwith good dispersionwith good dispersion
Reo = 1250 (xo = 4 mm, f = 1 Hz)
Real system 3-D CFD simulation
NiTech’s Continuous OBR (COBRTM)
Tracer
Conductivity probes
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Oscillation
Out
liquid
Probe 13.7 meters away from injectionProbe 27.9 meters away from injectionProbe 310.1 meters away from injection
D = 0.00007~0.003 m2/s
• Mixing is not controlled by net flow
• Plug flow achieved at laminar flows
Key differences from other tubular devices on the market
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laminar flows
• Excellent heat & mass transfers
• No concentration gradients
• Good with solids
Equipment Selection - Reactor TechnologyE
xoth
erm
Many reactions fall into the band of exothermagainst reaction timeMicro
reactorsSpinning
disc reactors
Compact reactors
Reaction time
Exo
ther
m
ms secs mins hrs
Static mixer reactors Oscillating flow reactors
CSTR
Continuous oscillatory baffled crystalliser
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baffled crystalliser (COBCTM)
Heat Transfer on Scale-Up
Volume (m 3) Area (m 2) Area / unit Volume (m 2/m3)
Typical 90 litre STR
0.09 0.9 10
Typical 6500 litre STR
6.82 15.8 2.3
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COBC™ has larger specific surface area for HT
Typical 72m long 100mm
diameter COBCTM
0.56 22.6 40
COBC offers
� Consistent fluid mechanical conditions for nucleation and growth
� Different mixing mechanism in comparison to traditional stirring
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traditional stirring
� Excellent heat transfer characteristics
� Easy operation, e.g. cooling/heating at different sections
Control over cooling profile
90-10 oC Flow Rate 0.3 L/min Cooling Rate 2.0 oC/mi n
y = -1.7118x + 81.031
R2 = 0.993460
70
80
90
80-10oC Flow Rate 0.945 L/min Cooling Rate 6.5oC/mi n
y = -6.5517x + 83.727
R2 = 0.9918
y = -6.5524x + 83.696
R2 = 0.9916
y = -6.5657x + 83.8
R2 = 0.9919y = -6.5541x + 83.668
R2 = 0.9917y = -6.5629x + 83.699
R2 = 0.9919
0
10
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30
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70
80
90
0 2 4 6 8 10 12
Time (min)
Tem
p (o
C)
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R2 = 0.9934
y = -1.7103x + 80.986
R2 = 0.9935
y = -1.7106x + 80.97
R2 = 0.9933
y = -1.7112x + 80.972
R2 = 0.9933
y = -1.7121x + 81.032
R2 = 0.9936
0
10
20
30
40
50
60
0 10 20 30 40 50
Time (min)
Tem
p (o
C)
Any cooling profile, e.g. linear, parabolic, non-continuous, step-wise and etc, can be obtained along COBCTM
Any lab monitoring techniques can directly be implemented along COBCTM without modification
a) Pharma API
4. Case studies
The residence time in the COBCtranslates to 12 minutes, compared to a batch cycle time of 8 hours, demonstrating a significant potential improvement in throughput relative to a batch manufacturing facility.
Product performance
�All continuously generated material filters very well–Material specific resistance ~106 m/kg
––Typically 107 – 109 m/kg for APIs in manufacture
�Agglomerated / Aggregated material appears compressible
�Rods appear relatively uncompressible following cake consolidation
Conceptual Flowsheet
�We could incorporate continuous dissolution and crystallisation
into an overall continuous pures process
An Alternative Process Design (2)Particle Engineering to remove milling step
Capital Costs (new builds) would be approx 50% lower
�Operating Team could be reduced by about a further 1/3rd
�Solvent consumption reduced�Solvent consumption reduced
�Overall impact on Cost of Goods–Reduced Depreciation costs
–People £622k/year
–10% solvent consumption reduction ~ £400k/year
–No losses in milling operation
Organic Process Research & Development, 2009, 13, 1357-1363
b) Filtration index for a pharma product
COBCTM deliver� Product characteristics/performance� Consistent filtration index of 25
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STR COBCTM
c) Crystal moisture contents
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Moisture content:50% 73%
Crystallisation achieved in 1/8th of the time
OBC STR
d) Filtration rate vs crystal size
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Filtration rate (L/m 2.hr)
648.9 2125 24610
Purity by HPLC (%)
99.26 99.44 99.37
Yield by HPLC (%)
98.31 99.07 98.80
e) Fractionation of edible oils
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� Two stage cooling (17 and 0.3 oC/min)
� Consistent IV achieved0
5
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20
25
0 50 100 150 200
Process Time (min)
Filt
ratio
n ti
me
(m
in)
Benchmark
T05C
T08C
T10C
T11C
T12C
T13C
T14C
T16C
• Significant reduction of crystallisation time
• Improved filtration time
f) Crystallisation for purification
� Purity increased from 91.2% to 97.8%
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to 97.8%� Customer’s
benchmark: 95.5%
g) Extended Operation 24 hrs a day for 7 days
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Vanisal sodium data
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Time (hour)
Van
isal
Sod
ium
(m
g/m
l)
Valve a
Valve f
As pirin tes t
0
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300
0 50 100 150 200
Time (hour)
Ace
tyls
alic
ylic
Aci
d (m
g/m
l)
Valve a
Valve b
Valve c
Valve f
Aspirin run
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SEM of crystals
Cycle 16Cycle 12 Cycle 24
Cleaning
Washing data for Aspirin
Cleaned during 3rd wash
1st order kinetics
a) How did nucleation take place in OBC without seeding, while seeding was essential in benchmarking cases?
b) Why did OBC have higher nucleation temperature &
Some interesting findings
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b) Why did OBC have higher nucleation temperature & narrower MSZW than traditional crystallisers?
c) Why/how did OBC allow consistent crystal morphology?
d) Why/how did OBC achieve the same/better purities at faster cooling rates, while impurities increase with cooling rates in benchmark cases?
a) GSK led initiative with industrial companies, e.g. Pfizer, AZ
b) Supported by universities (Bath, Edinburgh, Glasgow, Heriot-Watt, Loughborough and Strathclyde)
Continuous Manufacturing And Crystallisation (CMAC)
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Heriot-Watt, Loughborough and Strathclyde)
c) Supported by Scottish Government and UK funding bodies
d) A global “one-stop” shop for continuous crystallisation and manufacturing
• Plug flow tubular crystallisation technology, such as COBCTM, can be used for both pilot and industrial scale crystallisation operations
• Any lab scale monitoring techniques can directly be fitted along the COBCTM
4. Forward remarks
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fitted along the COBCTM
• COBCTM can be incorporated into existing plants
Continuous crystallisation using COBCTM is not the future, but it is right here and right now.
Dr Gayle De Maria, Chemistry Today
Acknowledgement
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Colleagues from NiTech