team 4 final presentation

7/30/2019 Team 4 Final Presentation

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Yousef Ghotok Joseph Havelin

Wednesday, 23rdApril 2008

Chemical Reaction Engineering

Dr. Robert P. Hesketh

Dr. Concetta LaMarca


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Outline

Background, Process Reactions, and Rate Expressions

Initial Calculations

Case I Reactor Volume Using Simple Reaction Rate Expression

Case II Pressure Drop and Reactor Configuration

Case III Multiple Reactions

Case IV Energy Balance for Multiple Reactions

Case V Optimization of Reactor Design


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Background, Process Reactions, and

Rate Expressions

Maleic anhydride is a cyclic organic chemical with formula C4H2O3.

Primary Use: Synthesis of Unsaturated Polyester Resins N-butane is the most common feedstock used in production of

maleic anhydride.

Bergman and Frisch discovered synthesizing maleic anhydride from

n-butane by catalyzing the oxidation reaction.

By 1985, all commercial producers of maleic anhydride in the US

used n-butane as their feed.

Worldwide Production: 1,359,000 tons per year

US Production: 273,800 tons per year


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Rate Expressions

The partial oxidation of n-butane at the surface of the catalyst

produces maleic anhydride and water, and side reactions produce

carbon monoxide, carbon dioxide and water.

Catalyst used is vanadium-phosphorus oxide ((VO)2P2O7).

Reactor Type Fixed-Bed Reactor

Advantages: easy use and low maintenance demand

Disadvantages: hot spots and pockets of diluted butane


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Rate Expressions

Balanced Stoichiometric Equation: Cases I and II

C4H10 + 3.5O2 C4H2O3 + 4H2O

Rate Equation: Cases I and II

rM

= k1

CB

Pseudo-First Order Rate Constant: Cases I and II

k1= 8.1048 106 exp(-15649/T) [m3/kgcat-sec]

Reactions From the Oxidation of N-Butane: Cases III, IV, and V


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Rate Expressions

Reaction Pathway Diagram: Cases III, IV and V

Reaction Rate Expressions: Cases III, IV and V

Rate Constants and Parameters


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Assumptions:

Open system at steady state

Negligible changes in kinetic and potential energy

Negligible work

14 days worth of downtime per year Inlet gas 1.7 mol% n-butane

80% conversion rate; side reactions not considered in this

preliminary stage

25,000 tons/year production rate

Reference temperature = 25 C = 298 K


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Stoichiometric Tables:

Molar Stoichiometric Table

Mass Stoichiometric Table

Species Initial (kmol/s) Change (kmol/s) Final (kmol/s)

H2O 0 0.03362 .03362

C4H10 0.01051 -0.00841 .00210

O2 0.12758 -0.02942 .09816N2 0.47993 0 .47993

C4H2O3 0 .00841 .00841

Total 0.61802 .00042 .62222

Species Initial (kg/s) Change (kg/s) Final (kg/s)H2O 0 0.60568 .60568

C4H10 0.61065 -0.48852 .12213

O2 4.08231 -0.94133 3.14099

N2 13.44455 0 13.44455

C4H2O3 0 0.82417 .82417

Total 18.13751 0 18.13751


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CaseI

Additional Assumptions: Isothermal Reactor Model to Estimate

the Reactor Volume

Isothermal Temperature = 673 K

Bulk Density = 900 kgcat/m3

Void Fraction = 0.44

Particle Diameter = 5 mm

Inlet Pressure = 1.5 bar


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CaseI

Polymath: Isothermal Packed

Bed Reactor Model

Results

Stream Flows

Species

Initial

(kmol/s)

Final

(kmol/s)

H2O 0 0.0336C4H10 0.0105 0.0021

O2 0.1276 0.0982

N2 0.4799 0.4799

C4H2O3 0 0.0084

Variable Value

Conversion 0.8000043

Catalyst Wt. 57675 kg

Bulk Density 900 kgcat/m3VRXTR 64.08333 m

3

Aspen Plus: RPLUG Reactor

Stream Flows

Substream: MIXED FEED PRODUCT

Mole Flow (kmol/sec) VAPOR VAPOR

BUTANE 0.0105 2.08E-03

OXYGEN 0.1276 0.0981338MALEI-01 0 8.42E-03

WATER 0 0.0336756

NITROGEN 0.4799 0.4799


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CaseI

Polymath: Isothermal Packed Bed Reactor Model

Effect of Catalyst Weight and Temperature on Conversion

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10000 20000 30000 40000 50000 60000

Conversionofn-butane

Catalyst Weight (kg)


350C

375C

400C

425C

450C


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CaseII

Additional Assumptions: Pressure Drop in the Fixed-Bed Reactor

Must not Exceed 1/10 the Initial Pressure

Pressure drop along the length of the reactor


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CaseII


Bed Reactor Model

Results

Stream Flows

Variable Value


Catalyst Wt. 60500 kg

Bulk Density 900 kgcat/m3

VRXTR 67.2222 m3

Species

Initial

(kmol/s)

Final

(kmol/s)

H2O 0 0.0336371

C4H10 0.0105 0.0020907

O2 0.1276 0.0981675

N2 0.4799 0.4799

C4H

2O

30 0.0084093


Stream Flows for Single Tube Reactor

Stream Flows for Multi-Tube Reactor



BUTANE 0.0105 2.02E-03

OXYGEN 0.1276 0.097918

MALEI-01 0 8.48E-03

WATER 0 0.0339223

NITROGEN 0.4799 0.4799



BUTANE 0.0105 2.07E-03

OXYGEN 0.1276 0.0981009

MALEI-01 0 8.43E-03

WATER 0 0.0337133

NITROGEN 0.4799 0.4799


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CaseII



0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10000 20000 30000 40000 50000 60000

Conversionofn-butane

Catalyst Weight (kg)


623K

648K

673K

698K

723K

623K Old

648K Old

673K Old

698K Old

723K Old


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CaseII


Effect of Length on Pressure Drop

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7

PressureDrop%

Length of Reactor (m)

Effect of Length on Pressure Drop

Dp=7mm

Dp=14mm


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CaseII

Comparison of Three Models

# of

Tubes Po (Pa) Pf(Pa) T (K)

Pressure Drop

%

Polymath 1 150000 135500 673 8.961

Aspen Single Tube 1 150000 136543.8 673 8.97

Aspen Multi-Tube 37220 150000 136546.8 673 8.97


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CaseIII

Additional Assumptions:

Side reactions and byproducts are taken into consideration


Bed Reactor Model

Results

Stream Flows

Variable ValueConversion 0.80742

Catalyst Weight 212000 kg


VRXTR 235.5556 m3

SpeciesInitial

(kmol/s)Final

(kmol/s)

C4H10 0.023 0.0044292

O2 0.2793 0.194784

N2 1.05065 1.05065

C4H2O3 0 0.0084034

H2O 0 0.0884504

CO 0 0.0219674

CO2 0 0.0187201



Stream Flows for Single Tube Reactor

Species

Initial

(kmol/s)

Final

(kmol/s)

C4H10 0.023 0.00440319

O2 0.2793 0.1946679

N2 1.05065 1.05065

C4H2O3 0 0.00841679

H2O 0 0.0845672

CO 0 0.0219936

CO2 0 0.0187264

Species

Initial

(kmol/s)

Final

(kmol/s)

C4H10 0.023 0.00440171

O2 0.2793 0.1946573

N2 1.05065 1.05065

C4H2O3 0 0.00841548

H2O 0 0.0845759

CO 0 0.0219996

CO2 0 0.0187316


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CaseIII


Effect of Reaction Temperature on Selectivity of Maleic

Anhydride

0.203

0.204

0.205

0.206

0.207

0.208

0.209

0.21

0.211

0.212

623 633 643 653 663 673 683 693 703 713 723

Selectivity

Temperature (K)

Effect of Reaction Temperature on Selectivity of Maleic Anhydride


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CaseIII


Effect of Reactor Length on Molar Flows

0

0.05

0.1

0.15

0.2

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0.3

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

MolarFlows(kmol/s)

Reactor Length (m)

Effect of Reactor Length on Molar Flows

n-butane

Maleic Anhydride

Water

Carbon Monoxide

Carbon Dioxide

Oxygen


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CaseIII

Comparison of Three Models

# of

Tubes Po (Pa) Pf(Pa) T (K)

Pressure Drop

%

Polymath 1 150000 137400 673 8.4

Aspen Single

Tube 1 150000 137336 673 8.442666667

Aspen Multi-Tube 99200 150000 137336 673 8.442666667


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CaseIV

Additional Assumptions:

Non-isothermal

Energy Balance taken into consideration

Heat exchanger with constant coolant temperature, Ta = 673 K

Overall Heat Transfer Coefficient = 105 J/(m2*K*s)


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CaseIV

Polymath: Non-Isothermal

Packed Bed Reactor Model

Results

Stream Flows

Variable Value


Catalyst Weight 173500 kg


VRXTR 192.7778 m3

Species Initial (kmol/s)

Final

(kmol/s)

C4H10 0.023 0.0043884

O2 0.2793 0.1945189

N2 1.05065 1.05065

C4H2O3 0 0.0084033

H2O 0 0.0846545

CO 0 0.0219682

CO2 0 0.0188649



Species

Initial

(kmol/s)

Final

(kmol/s)

C4H10 0.023 0.00438659

O2 0.2793 0.1945099

N2 1.05065 1.05065

C4H2O3 0 0.00840391

H2O 0 0.0846631

CO 0 0.0219706

CO2 0 0.0188673


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CaseIV


Effect of Varying Ta On Hot Spot

650

660

670

680

690

700

710

720

730

0 0.5 1 1.5 2 2.5 3 3.5 4

Temperature(K)

Reactor Length (m)

Effect of Varying Ta on Hot Spot

Ta=673 K

Ta=663 K

Ta=683 K

Ta=653 K


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CaseIV

Comparison of Isothermal and Real Reactor Models:

Polymath

Aspen

To (K) Ta (K)

FMAN

(kmol/s) Selectivity Conversion

Real 673 673 0.0084033 0.2057963 0.8091979

Isothermal 673 NA 0.0077919 0.206338 0.7492456

To (K) Ta (K)

FMAN

(kmol/s) FCO (kmol/s)

FCO2

(kmol/s) Selectivity

Real 673 673 0.00840391 0.02197067 0.01886732 0.2057866

Isothermal 673 NA 0.00780377 0.02042879 0.01739411 0.2063239


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CaseV

Optimal Reactor Conditions:

To (K) 673

Ta (K) 673

Po (Pa) 1.70E+05

DOverall (m) 6.95

dIndividual Tube

(m) 0.0254

Length (m) 4.158975

Number of Tubes 74870

VRXTR(m3) 157.778

Catalyst Wt (kg) 142000

Selectivity 0.204517

Criteria Met:

Minimal reactor size

Minimized cost

Constant selectivity throughout

runs

Gain < 2

Pressure Drop < 10%

team 4 final presentation

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