Idealidad En Cstr
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Ideality of a CSTR
Jordan H. Nelson Property of Beehive Engineering
Brief Overview Introduction – General CSTR Information Three Questions Experimental Conclusions
Property of Beehive Engineering
Schematic of the CSTR Item
Description
1
Mixing Point
2
Mixing Point
3
Mixing Point
4
Mixing Points
5
Water Bath Inlet and Outlet
6
Four Wall Mounted Baffles
7
Mixer Drive
8
Marine Type Impeller
9
CSTR Vessel
10
Water Bath Vessel
Property of Beehive Engineering
3 Questions
?
Where is the best mixing in the CSTR? What is τmean and how does it compare to τideal? What configuration of PFR-CSTR will produce the greatest conversion? Property of Beehive Engineering
Where is the Best Mixing?
Impeller selection
Food Dye Test
Dead Zones
Impeller Speed Property of Beehive Engineering
Flow Patterns of different impellers Rushton Impeller
Marine Impeller
Property of Beehive Engineering
τMean vs τIdeal
?
τMean – Measured mean residence time The amount of time a molecule spends in the reactor τIdeal – Ideal residence time is calculated from the following equation
τ ideal
V = νo
Property of Beehive Engineering
Experiment
Fill reactor with low concentration salt (baseline) Spike reactor at most ideal mixing Create spike concentration at least one order of magnitude larger than baseline Measure change in conductivity over time Run experiment at different impeller speeds Property of Beehive Engineering
Yikes! Plot of Concentration vs Time with Error 35 30 RPM 15 RPM Concentration NaCl(g/mL)
30
25
20
15
10 0
100
200
300
400
500
600
700
Time(s)
Property of Beehive Engineering
800
Measured Concentration over time in the CSTR. 26
Concentration NaCl(g/mL)
25 24
30 RPM 15 RPM
23
22 21
20 0
200
400
600
800
Time(s)
Property of Beehive Engineering
RTD Function E(t)
Measured concentrations are used to create the residence time distribution function
E (t ) =
C (t ) − C (t = 0) t end
∫ [C (t ) − C (t = 0)]dt 0
Property of Beehive Engineering
Plot of an ideal residence time distribution function
Property of Beehive Engineering
Residence time distributions 0.0023 0.0021 0.0019
E(t)
0.0017 0.0015 0.0013 0.0011 Ideal E(t)
0.0009
E(t) Conductivity 15 RPM E(t) Conductivity 30 RPM
0.0007 0.0005 0
20
40
60
80
100
120
140
160
180
200
Time(s)
Property of Beehive Engineering
Mean Residence Time
Using E(t) the following equations produce the mean residence time
t mean =
t end
tE ( t ) dt = τ mean ∫ 0
t end
σ = ∫ (t − t m ) E (t )dt 2
0
Property of Beehive Engineering
Comparison of Residence Times RPM
Mean Residence Time
Standard Deviation
Sigma
Sigma/ Tau
15
357.57
11.58
206.87
0.58
30
358.14
11.58
206.35
0.58
466.97
5.90
Ideal CSTR
Property of Beehive Engineering
Loss of Data
Over an hour of data was lost from Opto 22 Calculation of Reynolds number over 4000 2 (Turbulent)
ND ℜ= υ
Equation applies to a baffled CSTR RPM speed of 300 obtained full turbulence Property of Beehive Engineering
CSTR-PFR Configurations ?
Schematic of arrangements Levenspiel Plot Conduct saponification reaction in the reactor at different RPM’s Use Equimolar flow rates and concentrations of reactants Quench reaction with a HCl and titrate with NaOH Property of Beehive Engineering
Series Reactor with CSTR Before PFR.
Property of Beehive Engineering
Series Reactor with PFR Before CSTR.
Property of Beehive Engineering
Et − Ac + NaOH ↔ NaAc + Et − OH Levenspiel Plot for NaOh+EtOAc 8 Levenspiel Plot for NaOh+EtOAc
-1/ra
6 4 2 0 0
0.1
0.2
0.3
0.4
0.5
0.6
Conversion
Property of Beehive Engineering
CSTR-PFR Configurations ?
Schematic of arrangements Levenspiel Plot Conduct saponification reaction in the reactor at different RPM’s Use Equimolar flow rates and concentrations of reactants Quench reaction with a HCl and titrate with NaOH Property of Beehive Engineering
Measured Conversion for PFR-CSTR Configuration Speed (RPM)
Conversion (%)
Conversion Error (%)
30
19.7
+/-
4.30
60
21.7
+/-
3.91
200
21.2
+/-
4.00
400
24.3
+/-
3.48
875
24.7
+/-
3.41 Property of Beehive Engineering
Measured Conversion for CSTR-PFR Configuration Speed (RPM)
Conversion (%)
Conversion Error (%)
30
21.5
+/-
3.94
60
21.2
+/-
4.00
200
21.4
+/-
3.97
400
20.9
+/-
4.06
875
21.5
+/-
3.94 Property of Beehive Engineering
3 Questions
?
Where is the best mixing in the CSTR? What is τmean and how does it compare to τideal? What configuration of PFR-CSTR will produce the greatest conversion? Property of Beehive Engineering
Conclusions
Better mixing for a Rushton impeller is below the impeller The reactor is far from ideal at low impeller speeds The PFR-CSTR arrangement provided better conversions Run the PFR-CSTR reactor at RPM’s of higher than 300 Property of Beehive Engineering
Opportunities
Run the experiment again to obtain the lost residence time values Run the saponification reaction at higher temperatures Exit sampling stream should be at the bottom of the reactor
Property of Beehive Engineering
Acknowledgements
Taryn Herrera Robert Bohman Michael Vanderhooft Dr. Francis V. Hanson Dr. Misha Skliar
Property of Beehive Engineering
REFEREN CES De Nevers, Noel, Fluid Mechanics, McGraw Hill, New York N.Y. (2005) Fogler, H. Scott, Elements of Chemical Reaction Engineering, Prentice Hall, Upper Saddle River, N.J. (1999) Havorka, R.B., and Kendall H.B. “Tubular Reactor at Low Flow Rates.” Chemical Engineering Progress, Vol. 56. No. 8 (1960). Ring, Terry A, Choi, Byung S., Wan, Bin., Phyliw, Susan., and Dhanasekharan, Kumar. “Residence Time Distributions in a Stirred Tank-Comparison of CFD Predictions with Experiments.” Industrial and Engineering Chemistry. (2003). Ring, Terry A, Choi, Byung S., Wan, Bin., Phyliw, Susan., and Dhanasekharan, Kumar. “Predicting Residence Time Distribution using Fluent” Fluent Magazine. (2003). Property of Beehive Engineering
What to expect from your CSTR.
Property of Beehive Engineering
Question?
Property of Beehive Engineering
Design Equations
b − ra = k * Cao * (1 − X ) * Cbo(Θ b − X ) a
− ra = k * Cao (1 − X ) 2
2
FA 0 X
VCSTR =
2
kC Ao (1 − X )
V PFR = ∫
X
0
2
dX 2
kC A0 (1 − X )
2
Property of Beehive Engineering
Design Equations ∞
−t τ
(t − τ ) σ =∫ * e dt τ 0 2
2
Property of Beehive Engineering
Jordan H. Nelson Property of Beehive Engineering
Brief Overview Introduction – General CSTR Information Three Questions Experimental Conclusions
Property of Beehive Engineering
Schematic of the CSTR Item
Description
1
Mixing Point
2
Mixing Point
3
Mixing Point
4
Mixing Points
5
Water Bath Inlet and Outlet
6
Four Wall Mounted Baffles
7
Mixer Drive
8
Marine Type Impeller
9
CSTR Vessel
10
Water Bath Vessel
Property of Beehive Engineering
3 Questions
?
Where is the best mixing in the CSTR? What is τmean and how does it compare to τideal? What configuration of PFR-CSTR will produce the greatest conversion? Property of Beehive Engineering
Where is the Best Mixing?
Impeller selection
Food Dye Test
Dead Zones
Impeller Speed Property of Beehive Engineering
Flow Patterns of different impellers Rushton Impeller
Marine Impeller
Property of Beehive Engineering
τMean vs τIdeal
?
τMean – Measured mean residence time The amount of time a molecule spends in the reactor τIdeal – Ideal residence time is calculated from the following equation
τ ideal
V = νo
Property of Beehive Engineering
Experiment
Fill reactor with low concentration salt (baseline) Spike reactor at most ideal mixing Create spike concentration at least one order of magnitude larger than baseline Measure change in conductivity over time Run experiment at different impeller speeds Property of Beehive Engineering
Yikes! Plot of Concentration vs Time with Error 35 30 RPM 15 RPM Concentration NaCl(g/mL)
30
25
20
15
10 0
100
200
300
400
500
600
700
Time(s)
Property of Beehive Engineering
800
Measured Concentration over time in the CSTR. 26
Concentration NaCl(g/mL)
25 24
30 RPM 15 RPM
23
22 21
20 0
200
400
600
800
Time(s)
Property of Beehive Engineering
RTD Function E(t)
Measured concentrations are used to create the residence time distribution function
E (t ) =
C (t ) − C (t = 0) t end
∫ [C (t ) − C (t = 0)]dt 0
Property of Beehive Engineering
Plot of an ideal residence time distribution function
Property of Beehive Engineering
Residence time distributions 0.0023 0.0021 0.0019
E(t)
0.0017 0.0015 0.0013 0.0011 Ideal E(t)
0.0009
E(t) Conductivity 15 RPM E(t) Conductivity 30 RPM
0.0007 0.0005 0
20
40
60
80
100
120
140
160
180
200
Time(s)
Property of Beehive Engineering
Mean Residence Time
Using E(t) the following equations produce the mean residence time
t mean =
t end
tE ( t ) dt = τ mean ∫ 0
t end
σ = ∫ (t − t m ) E (t )dt 2
0
Property of Beehive Engineering
Comparison of Residence Times RPM
Mean Residence Time
Standard Deviation
Sigma
Sigma/ Tau
15
357.57
11.58
206.87
0.58
30
358.14
11.58
206.35
0.58
466.97
5.90
Ideal CSTR
Property of Beehive Engineering
Loss of Data
Over an hour of data was lost from Opto 22 Calculation of Reynolds number over 4000 2 (Turbulent)
ND ℜ= υ
Equation applies to a baffled CSTR RPM speed of 300 obtained full turbulence Property of Beehive Engineering
CSTR-PFR Configurations ?
Schematic of arrangements Levenspiel Plot Conduct saponification reaction in the reactor at different RPM’s Use Equimolar flow rates and concentrations of reactants Quench reaction with a HCl and titrate with NaOH Property of Beehive Engineering
Series Reactor with CSTR Before PFR.
Property of Beehive Engineering
Series Reactor with PFR Before CSTR.
Property of Beehive Engineering
Et − Ac + NaOH ↔ NaAc + Et − OH Levenspiel Plot for NaOh+EtOAc 8 Levenspiel Plot for NaOh+EtOAc
-1/ra
6 4 2 0 0
0.1
0.2
0.3
0.4
0.5
0.6
Conversion
Property of Beehive Engineering
CSTR-PFR Configurations ?
Schematic of arrangements Levenspiel Plot Conduct saponification reaction in the reactor at different RPM’s Use Equimolar flow rates and concentrations of reactants Quench reaction with a HCl and titrate with NaOH Property of Beehive Engineering
Measured Conversion for PFR-CSTR Configuration Speed (RPM)
Conversion (%)
Conversion Error (%)
30
19.7
+/-
4.30
60
21.7
+/-
3.91
200
21.2
+/-
4.00
400
24.3
+/-
3.48
875
24.7
+/-
3.41 Property of Beehive Engineering
Measured Conversion for CSTR-PFR Configuration Speed (RPM)
Conversion (%)
Conversion Error (%)
30
21.5
+/-
3.94
60
21.2
+/-
4.00
200
21.4
+/-
3.97
400
20.9
+/-
4.06
875
21.5
+/-
3.94 Property of Beehive Engineering
3 Questions
?
Where is the best mixing in the CSTR? What is τmean and how does it compare to τideal? What configuration of PFR-CSTR will produce the greatest conversion? Property of Beehive Engineering
Conclusions
Better mixing for a Rushton impeller is below the impeller The reactor is far from ideal at low impeller speeds The PFR-CSTR arrangement provided better conversions Run the PFR-CSTR reactor at RPM’s of higher than 300 Property of Beehive Engineering
Opportunities
Run the experiment again to obtain the lost residence time values Run the saponification reaction at higher temperatures Exit sampling stream should be at the bottom of the reactor
Property of Beehive Engineering
Acknowledgements
Taryn Herrera Robert Bohman Michael Vanderhooft Dr. Francis V. Hanson Dr. Misha Skliar
Property of Beehive Engineering
REFEREN CES De Nevers, Noel, Fluid Mechanics, McGraw Hill, New York N.Y. (2005) Fogler, H. Scott, Elements of Chemical Reaction Engineering, Prentice Hall, Upper Saddle River, N.J. (1999) Havorka, R.B., and Kendall H.B. “Tubular Reactor at Low Flow Rates.” Chemical Engineering Progress, Vol. 56. No. 8 (1960). Ring, Terry A, Choi, Byung S., Wan, Bin., Phyliw, Susan., and Dhanasekharan, Kumar. “Residence Time Distributions in a Stirred Tank-Comparison of CFD Predictions with Experiments.” Industrial and Engineering Chemistry. (2003). Ring, Terry A, Choi, Byung S., Wan, Bin., Phyliw, Susan., and Dhanasekharan, Kumar. “Predicting Residence Time Distribution using Fluent” Fluent Magazine. (2003). Property of Beehive Engineering
What to expect from your CSTR.
Property of Beehive Engineering
Question?
Property of Beehive Engineering
Design Equations
b − ra = k * Cao * (1 − X ) * Cbo(Θ b − X ) a
− ra = k * Cao (1 − X ) 2
2
FA 0 X
VCSTR =
2
kC Ao (1 − X )
V PFR = ∫
X
0
2
dX 2
kC A0 (1 − X )
2
Property of Beehive Engineering
Design Equations ∞
−t τ
(t − τ ) σ =∫ * e dt τ 0 2
2
Property of Beehive Engineering
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