Transcript Effects of Mixing on Adipic Acid Crystallization

Effects of Mixing on Adipic
Acid Crystallization
Susan Philyaw,
Kathryn Baker, Randal Nelson, Jessica Moffitt,
Joy Sroykum and Dr. Terry Ring
Outline of Talk
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Introduction- What is Adipic Acid?
Background- Purpose for Study.
Previous Research- Comparison.
Experimental System- Equipment.
Experimental Procedure- How we did it.
Results- What we found
Conclusions
Introduction
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Adipic acid = 2 Billion tonne /yr.
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Adipic acid is a natural product found in some plants
Adipic acid is produced by an oxidation reaction
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Adipic acid used in Nylon Manufacture
WH. Carothers’ at Dupont discovered Nylon in 1930’s
oxidation of cyclo-hexane
oxidation of phenol (minor route).
Other uses
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Resins, Polyurethanes, and Plasticizers
Background
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Purpose of study: Increase Quality Control
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Adipic acid is crystallized from an aqueous solution
by cooling.
Aggregation/Agglomeration
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Advantages:
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Easy to Filter
Challenges:
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Difficult to control crystal size distribution
Adheres to the reactor walls and other parts
Aggregates trap impurities/solvent in the voids of
particles
Previous Research
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Rene David’s Paper
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Stirred tank with cooling
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Batch with cooling
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Aqueous Solution of Adipic
Acid
Ethanol Solution of Adipic
Acid
A. Meyerson’s Paper
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Batch with cooling
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Tulock’s Paper
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Aqueous Adipic Acid
Solution
S. Derenzo’s Paper
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Alcohol Solution of Adipic
Acid
Batch with cooling
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Cesar and Ng
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Batch with cooling
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Aqueous Adipic Acid
Solution
Aqueous Adipic Acid
Solution
Williams-Seton, et. al.
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Batch with cooling
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Aqueous Adipic Acid
Solution
Experimental System
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Reactor- Continuous Stirred Tank (CSTR)
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Operating Condition
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Volume: 1.243 liters
Impeller RPM: varied 400 to 800 rpm
Flow rate: held constant 120.0 ml/min
Reactor Temperature T=15 C.
Solution Properties
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Concentration and Temperature
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18.2 gm/liter at 22.0 C.
Solubility
Adipic Acid Solubility
100
90
80
gm/liter
70
60
50
40
30
20
10
0
0
5
10
15
20
25
30
Temperature (C)
35
40
45
50
On-Line Analysis – Computer
Data Logging
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Feed Flow Rate
Product Flow Rate
Reactor
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Temperature - 
Stirrer RPM - 
Stirrer Torque - 
Heat Balance - 
Tank Internals
Off-line Analysis
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Steady State Sample
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Yield
Particle Size Distribution
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Beckman Coulter LS-230 (40 nm to 2000µm)
Particle Morphology
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SEM
Residence Time
Measurements
T,C
Time(min)
T=(To-Tin)exp(-t/tau)+Tin
T,C
Time(min)
Residence Time
Measurements
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Pulse Addition to Steady State CSTR
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Visual – Blue Dye
Salt – Conductivity
Hot – Temperature
Acid – pH converted to H+ concentration
Done Simultaneously
All the results are similar!
GOOD vs BAD MIXING
0.0025
0.0025
0.002
0.002
0.0015
H+
0.0015
H+
0.001
0.001
0.0005
0.0005
0
0:00:00
0:07:12
0:14:24
0:21:36
0:28:48
Time
20 RPM
0:36:00
0:43:12
0:50:24
0
0:00:00
0:07:12
0:14:24
0:21:36
0:28:48
300 RPM
0:36:00
0:43:12
0:50:24
Mean Residence Time Results
Comparison of tm with different flow rate & mixer rpm
0:20:10
127ml/min_01
Mean Resident Time (t m)
0:17:17
127ml/min_02
243ml/min_01
0:14:24
243ml/min_02
0:11:31
359ml/min_01
359ml/min_02
0:08:38
475ml/min_01
0:05:46
475ml/min_02
591ml/min_01
0:02:53
591ml/min_02
0:00:00
0
100
200
Mixer rpm
Vreactor ~ 1280 ml
300
400
RDT Variance Results
Comparison of Sigma/tm with different flow rate & mixer rpm
1.1
127ml/min_01
1.05
127ml/min_02
1
243ml/min_01
0.95
Sigma/tm
243ml/min_02
0.9
359ml/min_01
0.85
359ml/min_02
0.8
475ml/min_01
0.75
475ml/min_02
0.7
591ml/min_01
0.65
591ml/min_02
0.6
0
100
200
Mixer rpm
300
400
Experimental Procedure
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Experimental Procedure
Saturated Solution of Adipic acid feed to CSTR
Mean Residence time of 10 minutes
Steady state time of 50 minutes
Flow rate constant 120 ml/min
Rpm of impeller varied - 400, 800 rpm
Samples taken at steady state
Sample filtered, dried weighed to get yield
PSD, Beckman-Coulter LS 230 small volume
particle distribution unit
Particle Morphology - SEM
Results-2 – 400 rpm
Results 2 - 800 rpm
50 micro meters
500 micro meters
Results-3
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Yield
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400 rpm
800 rpm
64±5%
61 ±5 %
Particle Size Distribution
Particle Size Distribution
Differential Volume Vs. Particle Size
7
Differeintial Volume%
6
Diff Volume 800
Diff Volume 400
5
4
3
2
1
0
1
10
100
Particle Size (micro meter)
1000
10000
Conclusions
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Mixing speed must be greater than 200
rpm
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Ideal Mixing in Stirred Tank
Mixing speed controls the aggregate
size
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Smaller aggregates give less impurities
Smaller aggregates are more difficult to
filter
Acknowledgement
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DOE/OIT
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Industries of the Future Research Program