power point del aa

7/28/2019 Power Point Del AA

1/32

Team 1

Michael GlasspoolSarah Wilson

Nicole Cosgrove


2/32

Production Goals Produce 30,000 Metric Tonnes / year

Operate for 350 days / year

Produce acrolein at 0.0177 kmol / s


3/32

Allowable Process Conditions1,2

Process typically run between 320 390C

Run between atmospheric pressure and 303.975 kPa (3

atm) Use air as an oxygen source

Typical Conversion between 65 90 %

Propylene flammability range 2 11.1 %


4/32

Process Optimization Process was optimized in a series of reports

Modeling started off simple and became more

complex Pressure drop calculations and energy balances were

added over the course of the semester to accuratelymodel the system


5/32

Material BalanceAssume an 80 % propylene conversion Flow enough air to stay below LFL of 2%

C3H6 + O2 C3H4O + H2O

Species NameChemical

Formula

Inlet Molar

Flow rate

(kmol/s)

Inlet Mass

Flow rate

(kg/s)

Outlet Molar

Flow rate

(kmol/s)

Outlet Mass

Flow rate

(kg/s)

Propylene C3H6 0.0221 0.9308 0.0044 0.1862

Oxygen O2 0.2433 7.7864 0.2256 7.2202

Nitrogen N2 0.9154 25.6304 0.9154 25.6304

Acrolein C3H4O 0.0000 0.0000 0.0177 0.9921

Water H2O 0.0000 0.0000 0.0177 0.3188

Total - 1.1808 34.3476 1.1808 34.3476


6/32

Preliminary Energy Balance This model assumes a single reaction

Adiabatic and Isothermal cases were modeled

Variable Isothermal Adiabatic

Inlet Temp (K) 623.15 623.15

Outlet Temp (K) 623.15 777.84

Hrxn (J/s)x10-6

-6.02 0

Heat Duty (J/kmol reacted)x10-6

-340 0


7/32

Simple Kinetic Expression3

Rate expression was first order in propylene and half

order in oxygen

sec/212 catOp kgkmolCCkr

2

1

336 sec/)/5.16206exp(101778.5

mkmolkgmTk catrxtr


8/32

Simple Kinetics ResultsAssuming steady-state, isothermal plug flow, the

reactor was modeled in POLYMATH and Aspen Plus

Number of Tubes 1

Tube Diameter (m) 10

Tube Length (m) 759.89

Reactor Volume (m3) 59681.87

Catalyst Bulk Density (kg/m3

rxtr) 1000

Catalyst Weight (kg) 59681870

Catalyst Void Fraction 0.4Reactor Temperature (K) 623.15

Reactor Pressure (kPa) 101.325

Heat Duty (W) -6014660

Calculated Heat Duty (W) -6020000

Residence Time (s) 395.3


9/32

Simple Kinetics Results

0

10

20

30

40

50

60

70

80

90

100

0.00E+00 1.00E+04 2.00E+04 3.00E+04 4.00E+04 5.00E+04 6.00E+04

PropyleneConversion(%)

Reactor Volume (m3)

723 K

713 K

703 K

693 K

683 K

673 K

663 K

653 K

643 K

633 K

623 K


10/32

Major Findings The reactor volume was too large

Increasing the temperature can drastically decrease

the reactor volume Reactor temperature would be raised to 663.15 K, the

maximum temperature


11/32

Pressure Drop CalculationA pressure drop calculation was added using the ErgunEquation, assuming an isothermal plug f low reactorwith a catalyst void fraction of 0.40 4

To

T

o

o

bulkc

o

F

F

T

T

P

P

AdW

dP

GDD

G

ppo

o 75.1)1(150)1(

3

c

i

Woi

A

MF

Gi

,


12/32

Pressure Drop Results By increasing the inlet pressure to 3 atm, the reactor

size was minimized and pressure drop was more easilymodeled

Reactor Temperature (K) 663.15

Initial Pressure (kPa) 303.975

Catalyst Weight (kg) 2628582

Catalyst Density (kg/m3) 6350

1

Reactor Volume (m3) 752.6362

Reactor Diameter (m) 17

Reactor Length (m) 3.31587

Pressure Drop (kPa) 0.2965

Percent Pressure Drop (%) 0.0975

1 Perry, Dale L., and Sidney L. Phillips. Handbook of Inorganic Compounds. CRC Press, 1995.

Number of Tubes 509668.7

Number of Reactors 6

Tubes per Reactor 84945

Total Flow Rate (kmol/s) 1.1808

Flow Rate per Reactor (kmol/s) 0.1968

Total Catalyst Weight (kg) 2628582

Catalyst per Reactor (kg) 438097

Total Reactor Volume (m3) 752.637

Volume per Reactor (m3) 125.4395


13/32

Reaction Kinetics Real reaction kinetics were found as modeled by Tan et

al 5


14/32

Kinetic Development Rate constants were given at different temperatures

Temperature (C) 350 375 390

ka 5.28 x 10-5

9.99 x 10-5

1.46 x 10-4

k12 (2.19 0.14) x 10-4 (3.86 0.37) x 10-4 (5.38 0.35) x 10-4

k13 (2.70 0.18) x 10-4

(2.94 0.31) x 10-4

(2.70 0.27) x 10-4

k14 (2.73 0.21) x 10-5

(4.52 0.55) x 10-5

(6.28 0.71) x 10-5

[ka] = (mol*m3)

1/2/(kg*s)

[kij] = m3/(kg*s)

1/T (1/K) ln(ka) ln(k12) ln(k14) ln(kCO2) ln(kCO)

0.001605 -9.849 -8.426 -10.509 -8.237 -12.149

0.001543 -9.211 -7.860 -10.004 -8.183 -11.1280.001508 -8.831 -7.528 -9.676 -8.346 -10.327


15/32


16/32

Kinetic Modeling Assumptions The reaction was assumed to take place in a steady

state, isothermal plug flow reactor

The catalyst void fraction was assumed to be 0.45 witha bulk density of 1565.5 kg/m3 6


17/32

Kinetic Modeling Results The new kinetics reduced the volume necessary to

produce an 80 % conversion

This allowed the reaction to take place in only onereactor

The best acrolein selectivity was found at the higherend of the temperature range (390C)


18/32

Molar Flow Rate throughout

Reactor


19/32

Acrolein Selectivity


20/32

Incorporation of an Energy BalanceAn energy balance was added to account for

temperature changes throughout the reactor

Molten salt (Ua = 227 W/m2-K) was used as a coolantto prevent a runaway reactor temperature7


21/32

Energy Balance Assumptions The flow rate of coolant was kept high enough to

maintain a constant coolant temperature of 658.15 K

Heat capacities and heats of reaction were assumed tobe constant


22/32

Energy Balance Results The addition of the energy balance reduced the overall

volume necessary to reach 80 % conversion

The pressure drop was also reduced from 10.64 % to9.98 %


23/32

Reactor Temperature Profile The temperature throughout the reactor was modeled

to determine the reactor hotspot

The effect of changes in the inlet and coolanttemperatures were also explored

For the base case, the reactor hotspot occurred at thebeginning of the reactor and reached a temperature of

672.5 K


24/32

Reactor Temperature Profile


25/32

Reactor Gain The reactor gain was analyzed to determine the

thermodynamic stability of the reactor 7

For a 1C change in inlet temperature, the gain wasfound to be 0.0754

Inlet

HS

T

TGain


26/32

Reactor Gain Profile


27/32

Energy Balance Results The coolant temperature effected the selectivity of the

reactor

The highest selectivity was found when the coolanttemperature and the inlet temperature were equal

To

(K)

Ta

(K)

Facrolein

(kmol/s)

FCO2

(kmol/s)FCO (kmol/s)

Facetaldehyde

(kmol/s)Selectivity

663.15 658.15 0.017681 0.007796 0.001124 0.002031 1.615

663.15 663.15 0.018495 0.007347 0.001307 0.002107 1.719663.15 668.15 0.019248 0.006897 0.001511 0.002176 1.819

658.15 658.15 0.017646 0.007834 0.001114 0.002028 1.608

668.15 658.15 0.017718 0.007757 0.001135 0.002034 1.622


28/32

Final Reactor DesignVariable Value Units

Inlet Propylene Flow Rate 0.027213 kmol/s

Inlet Oxygen Flow Rate 0.299583 kmol/s

Inlet Nitrogen Flow Rate 1.12716 kmol/s

Overall Pipe Diamter 4.5 m

Tube Diameter 0.0258226 m

Number of Tubes 30228 -

Reactor Length 2.42366 m

Void Fraction 0.45 -

Inlet Pressure 303.975 kPa

Inlet Temperature 663.15 K

Coolant Temperature 663.15 K

Overall Heat Transfer Coefficient 227 W/m2-KCatalyst Bulk Density 1565.5 kg/m3

Catalyst Weight 59997.8 kg


29/32

Temperature Profile in Final

Reactor Design

662

664

666

668

670

672

674

676

678

680

0 10000 20000 30000 40000 50000 60000 70000

ReactorTemperatur

e(K)

Catalyst Weight (kg)


30/32

Flow Rate Profile in Final Reactor

Design

0

0.005

0.01

0.015

0.02

0.025

0.03

0 10000 20000 30000 40000 50000 60000 70000

FlowR

ate(kmol/s)

Catalyst Weight (kg)

Propylene

Acrolein

CO2

CO

Water

Acetaldehyde


31/32

References1) Guest, H.R.. "Acrolein and Derivatives." Kirk-Othmer Encyclopedia of Chemical Technology. 4th ed.2) Machhammer, et al. Method for Producing Acrolein and/or Acrylic Acid. US Patent 7,321,058. January 2008.

3) Dr. Concetta LaMarca. Memo 2: Simple Kinetics. 2008.

4) Fogler, H. Scott. Elements of Chemical Reaction Engineering. 4th Ed. Prentice Hall. 2006.

5) Tan, H. S., J. Downie, and D. W. Bacon. "The Reaction Network for the Oxidation of Propylene over a BismuthMolybdate Catalyst." The Canadian Journal of Chemical Engineering 67(1989): 412-417.

6) "Bismuth molybdate, powder and pieces." CERAC Online Catalog Search. CERAC Incorporated. 05 Mar 2008.

7) Dr. Concetta LaMarca. Memo 5: Energy Balance. 2008.


32/32

Any Questions?

REACTOR

FEED

PRODUCT

power point del aa

Documents