team #2: kyle lynch david teicher shu xu the partial oxidation of propylene to generate acrolein
TRANSCRIPT
Team #2:Kyle Lynch
David TeicherShu Xu
The Partial Oxidation of Propylene to Generate Acrolein
Project Objective Process Background Material Balance Simple Kinetics and Rate Expressions Pressure Drop and Reactor Configuration Multiple Reactions Energy Balance Optimization and Conclusions
Design a Fixed Bed Reactor (FBR) for the production of acrolein by the partial oxidation of propylene
Produce 75,000 metric tons acrolein per year
Optimize the reactor design to minimize cost
Literature Review ◦ Research information on raw materials and products◦ Investigate catalysts and reaction kinetics
Reactor Design◦ Develop mole balances for multiple reactions◦ Implement pressure drop & energy balance equations◦ Optimize reactor
Acrolein◦ Raw material used for the production of pyridine, β-picoline, and some essential amino acids1
◦ Used for cleaning irrigation ditches, and other derivatives can be made into rubbers, glues, and polymers2
◦ Anti-microbial behavior Biocide in oil well to suppress the growth of bacteria2
◦ 100-500 million pounds produced in the U.S. in 20022
CH2=CH-CHO
Industry produces acrolein by the partial oxidation of propylene using oxygen and steam
The reaction is carried out in a catalytic FBR ranging between 350-450 °C1
Gaseous products leave and are quenched by cold water, then enter absorption column for product recovery3
CH2=CH-CH3 + O2 CH2=CH-CHO + H2O
Design 1-Preliminary mass and energy balance
Design 2-Reactor volume using simple reaction rate expression
Design 3-Pressure drop and reactor configuration
Design 4-Multiple reactions
Design 5-Energy balance on multiple reactions
Final Design-Optimization
A total of two weeks each year are allotted for scheduled shutdowns
All reactants and products are vapors
Air is used as an oxygen source
A 1:11 ratio of propylene:oxygen is outside the flammability limits4
The inlet pressure is 1 atm5
Negligible kinetic and potential energy losses
Isothermal, T=623.15 K5
SpeciesFeed Rate to Reactor
(kgmol/s)Change in Reactor
(kgmol/s)Effluent Rate
(kgmol/s)
Propylene, C3H6 0.05190 -0.04412 0.00779
Oxygen, O2 0.57090 -0.04412 0.52679
Nitrogen, N2 2.14768 0 2.14768
Acrolein, C3H4O 0 0.04412 0.04412
Water, H2O (v) 0 0.04412 0.04412
Total 2.77048 0 2.77048
• Material balance for annual production rate of 75,000 metric tons
*Design specification for acrolein production rate is 0.04412 kmol/s
CH2=CH-CH3 + O2 CH2=CH-CHO + H2O
All Design 1 assumptions
A conversion of 0.85 will be achieved3
1000 kg/m3 is Catalyst bulk density6
Reactor is at steady state
Ideal gas law applies
Simple kinetics6
To simulate the FBR being designed, a Polymath® model was developed.
The Polymath® reactor was created as a function of catalyst weight
Aspen Plus® used to examine the relationships between temperature, reactor volume, and conversion
PP rW
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Developed an isothermal reactor model as function of catalyst weight using Polymath® and ASPEN ®
* Higher temperatures require smaller reactors for same conversion
V = 167,000 m3
All Design 2 assumptions – Inlet pressure is 3 atm6
Catalyst void fraction of 0.46
Particle diameter of 5 mm7
Inlet viscosity is that of pure steam4
Schedule 40 pipe used for multi-tube reactors8
Implemented Ergun pressure drop equation into design
Optimized reactor so pressure drop is less than 10%
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V = 8,643 m3
* Pressure drop decreases conversion
Reactions are carried out in a catalytic FBR with temperatures ranging between 350-390°C
Acrolein is desired product
Major by-products9
◦ Water◦ CO and CO2
◦ Acetadehyde
OHCOOHC 22263 335.4
OHCOOHC 2263 333
OHCOHC 42263 634
C3H6+ O2 C2H4O + H2O
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Symbol SpeciesChemical Formula
A Propylene C3H6
B Oxygen O2
C Acrolein C3H4O
D Water H2O
E Carbon Oxides COx
F Acetaldehyde C2H4O
G Nitrogen N2
HCarbon Dioxide
CO2
ICarbon
MonoxideCO
All Design 3 assumptions – 2830 kg/m3 is catalyst particle density10
Tan et al. reaction kinetics representative9
CO2 reaction rate independent of temperature
Modified the reactor to include multiple reactions Used approved reaction kinetics to calculate species flow
rates
V = 287.5 m3
Temperature (K)Acrolein OutletFlow (kmol/s)
Carbon Oxides and Acetaldehyde Total
Outlet Flow (kmol/s)Acrolein Selectivity
623 0.04412 0.05937 0.74
633 0.04949 0.05438 0.91
643 0.05401 0.04922 1.10
653 0.05760 0.04430 1.30
663 0.06032 0.03991 1.51
673 0.06227 0.03621 1.72
IHF
CFHIC FFF
FS
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*Selectivity of acrolein increases with temperature
All Design 4 assumptions
227 W/m2-K is heat transfer coefficient6
Heat capacities are constant
Heats of reactions are constant
Coolant temperature is constant at 618.15 K6
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An energy balance across the reactor was introduced to further validate the model as a suitable representation of the actual reactor
Incorporated energy balance into reactor design Compared isothermal reactor and reactor with constant
coolant temperature
The Effect of Coolant Temperature on Temperature Profile
*Coolant temperature effects severity of hotspot
V = 281.3 m3
“Gain” measures the dynamic stability of the reactor
A “Gain”< 2 is desired
Coolant Temperature (K)Polymath® Model
Hotspot Temperature (K)Aspen Plus® Model
Hotspot Temperature (K)
658.15 674.12 674.11
659.15 675.24 675.24
GAIN 1.12 1.13
coolant
HS
T
TGain
The catalyst void fraction is 0.46
Catalyst bulk density is 1698 kg/m3 for α-Bi2Mo3O12 10
The inlet pressure is 3 atm6
The inlet temperature is 663.15 K9
The coolant temperature is constant at 658.15 K6
FEED
PRODUCT
B1
Specification Value
Feed Conditions
Temperature 663.15 K
Pressure 3 atm
Propylene:Oxygen Ratio 1:11
Propylene Conversion 85%
Catalyst
Bed Voidage 40%
Particle Diameter 5 mm
Bulk Density 1698 kg/m3
Bed Weight 185047.25 kg
Bed Volume 108.98 m3
Reactor
Length 2.40 m
Overall Reactor Diameter 7.60 m
Tube Diameter 0.0259 m
Number of Tubes 86,304
Heat Transfer Coefficient 227 W/m2-K
Coolant Temperature 658.15 K
Pressure Drop 9.54%
Species Annual Production (Metric Tons)
Propylene, C3H6 12,363
Oxygen, O2 613,288
Nitrogen, N2 2,269,470
Acrolein, C3H4O 75,008
Water, H2O 36,226
Acetaldehyde, C2H4O 6,783
Carbon Dioxide, CO2 25,779
Carbon Monoxide, CO 2,421
1John J. McKetta. “Acrolein and Derivatives” Encyclopedia of Chemical Processing and Design. 2Toxicological Profile for Acrolein, U.S. Department of Health and Human Service, Agency for Toxic
Substance and Disease Registry (August 2007). 3“Acrylic Acid and Derivatives.” Kirk-Othmer Encyclopedia of Chemical Technology. 4th Edition. 4Chemical Database Property Constants. DIPPR Database [Online]. Available from Rowan Hall 3rd
Floor Computer Lab. (Accessed on 1/26/08). 5L. D. Krenzke and G. W. Keulks, The Catalytic Oxidation of Propylene: VIII. An Investigation of the
Kinetics over Bi2Mo3O12, Bi2MoO6, and Bi3FeMo2O12. The Journal of Catalysis Volume 64 (1980) p. 295-302.
6Dr. Concetta LaMarca 7“Reaction Technology.” Kirk-Othmer Encyclopedia of Chemical Technology. 4th Edition. 8Perry, Robert. Perry's Chemical Engineers' Handbook. 7th. New York: McGraw-Hill, 1997. 9H.S. Tan, J. Downie, and D.W. Bacon, The Reaction Network for the Oxidation of Propylene Over a
Bismuth Molybdate Catalyst, The Canadian Journal of Chemical Engineering Volume 67 (1989) p. 412-417.
10Cerac Incorporated. “MSDS Search” 25 March 1994. Accessed: 8 April 2008. <http://asp.cerac.com/CatalogNet/default.aspx?p=msdsFile&msds=m000443.htm>