Lecture 22 Thursday 3/27/08

Blowout VelocityCSTR Explosion

Batch Reactor Explosion

CSTR with Heat Effects

Energy Balance for CSTRs

Equation (8-9)

       (page 476)

(page 593)

dT

dt

FA0

N iCPi

G T R T

G T rAV H Rx

R T CPS1 T T0 Ta

At Steady State

dTdt

dNA

dt0

rAV FA0X

G T R T 0

HRx FA0X FA0 iCPiT T0 UA T Ta 0

Solving for X

Solving for T

X iCPi

T T0 UAFA0

T Ta

HRx XEB

T FA0X HRx UATa FA0 iCPi

T0

UAFA0 iCPi

dT

dt

FA0

N iCPi

G T R T

G T rAV H Rx

R T CPS1 T T0 Ta

Mole Balance

A B

V FA0X rA

rA kCA

CACA0 1 X

V FA0XkCA0 1 X

CA00XkCA0 1 X

k X1 X

Rate Law

Stoichiometry

Combine

V FA0XkCA0 1 X

CA00XkCA0 1 X

k X1 X

X k1 k

Ae E RT

1Ae E RT

G T X HRx Ae E RT

1Ae E RT HRx

Mole Balance

Rate Laws

Stoichiometry

Isothermal Design

Heat Effects

Mole Balance

Rate Laws

Stoichiometry

Isothermal Design

Heat Effects

H2O

N2O

Gas

200°F

510°F

Liquid

X

Ta0

NH4NO3 N2O 2H2O

Ta

T0 200FmA0 310lb h

17%H2O

83%NH4NO3

NH4NO3

M 500 lb

P

Safety in Chemical Reactors

H2O

N2O

Gas

200°F

510°F

Liquid

X

Ta0

NH4NO3 N2O 2H2O

Ta

T0 200FmA0 310lb h

17%H2O

83%NH4NO3

NH4NO3

M 500 lb

P

Then rearranging Equation (9-8)

dTdt

rAV HRx

Qg FA0 i Hi Hi0 UA T Ta

Qr

NiCPi

Qg Qr

NiCPi

Complete conversion FA = 0

Ý Q FA0CPAT T0 FA0B HB g HB0 rAVHRx FAHAvap NACPA

dT

dt

rAV HRx Qg

FA0 CPAT T0 B HB g HB0

Qr1 FAHVap UA T Ta

Qr 2

NACPA

dT

dt

Qg Qr1 Qr2 NACPA

dTdt

Batch Reactors with Heat Effects

Single Reactions

Multiple Reactions

Risk Rupture

dTdt

Qg Qr

NiCPi

Qr1 UA T Ta

Qg rA HRx

Qg rA HRx

Qr2 Ý m vapHvap

Reactor Mole Balance Summary

Keeping MBAs Away From Chemical Reactors

The process worked for 19 years before they showed up!!

Why did they come????

What did they want????

NO2

NH2

NO2

Cl

+ 2NH3 + NH4Cl

ONCB + Ammonia Nitroanaline + Ammonium Chloride

Nitroaniline Synthesis Reaction

To Crystallizing Tanks

Autoclave175 oC

~550 psi

NH3 Separation

FilterPress

NH3 in H2O

ONCB

O-Nitroaniline Product Stream

“fast” Orange

Nitroaniline Synthesis Process

Old

3 kmol ONCB43 kmol Ammonia

100 kmol WaterV = 3.25 m3

Nitroaniline Synthesis Reactor

Batch Reactor, 24 hour reaction time

Management said: TRIPLE PRODUCTION

NO2

NH2

NO2

Cl

+ 2NH3 + NH4Cl

ONCB + Ammonia Nitroanaline + Ammonium Chloride

Same Nitroaniline Synthesis Reaction

New9 kmol ONCB

33 kmol Ammonia

100 kmol WaterV = 5 m3

MBA Style Nitroaniline Synthesis Reactor

Monsanto Accident

9:55t = 0

10:40 10:50 midnight 12:18

Isothermal Operation

Cooling Restored

200

175

400

Tem

pera

ture

o C

Temperature-time trajectory

fuse

pWWpBBpAA

rxA

CNCNCN

DHVrTTUA

dt

dT

00

0 ))(()(

p

rg

NC

QQ

dt

dT

9:55t = 0

10:40 10:50 midnight 12:18

Isothermal Operation

Cooling RestoredQr = 0

200

175

400

Tem

pera

ture

o C

Temperature-time trajectory

fuse

CSTR multiple reactions

))((

:reactions multiplefor

0)()())((

0 )( :27-8 Eq

))(1(CR

))((-G

0)(R-G

0)(1

:NLE Ae1

Ae

00

Q

0

P0

/

/

g

rxijijg

Q

aPiirxA

AASa

C

rx

RTE

RTE

HVrQ

TTUATTCFHVr

VrXFWTTUAQ

TTk

XH

tf

Xfk

kXX

r

- =0

Example

Mole balance)

Rates) net rates, relative rates, rate laws…..

Stoichiometry)

Energy Balance)

)())(

)(

exp

exp

)(

)(

)(

)(

32 )2(

2 )1(

000

2211

0000

1

2

11222

1

1

11111

0

0

0

0

2

1

aPBBPAAr

ArxAArxAg

rg

DD

CC

BB

AA

TTR

E

CC

TTR

E

AA

DDDD

CCCC

BBBB

AAAA

Arx

Arx

TTUATTCFCFQ

VHrVHrQ

QQtf

FC

FC

FC

FC

kk

kk

VrFFFf

VrFFFf

VrFFFf

VrFFFf

ΔHDCA

ΔHCBA

FA0

FI0 A

)()()(

))((

gasses) are CB, in vat,A (only

2 02

000

000

2234

aBBBPAAr

rxAAg

PAA

rg

Pii

rg

CCCC

BBBB

AAAA

TTUAHHTTCFQ

HVrQ

CN

QQ

CN

QQ

t

T

VrFFt

NVrFF

t

NVrFF

t

N

CBAONHNONH

If the flow rate shut off, the temperature will rise (possibly to point of explosion!)