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Lecture 22. Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place. Today’s lecture. Blowout Velocity CSTR Explosion Batch Reactor Explosion. Last Lecture.

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lecture 22

Lecture 22

Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place.

today s lecture
Today’slecture
  • Blowout Velocity
  • CSTR Explosion
  • Batch Reactor Explosion
energy balance for cstrs2
Energy balance for CSTRs

Solving for X

Solving for T

energy balance for cstrs3
Energy balance for CSTRs

Increasing T0

R(T)

Variation of heat removal line with inlettemperature.

T

slide9

Energy balance for CSTRs

κ=∞

R(T)

κ=0

T0

Increase κ

Ta

T

Variation of heat removal line with κ (κ=UA/CP0FA0)

slide10

1) Mole Balance:

2) Rate Law:

slide17

Heat Effects

Isothermal Design

Stoichiometry

Rate Laws

Mole Balance

slide18

Isothermal Design

Heat Effects

Rate Laws

Stoichiometry

Mole Balance

example b liquid phase cstr
Example B: LiquidPhase CSTR

Same reactions, rate laws, and rate constants as example A

NOTE: The specificreaction rate k1A is defined with respect to species A.

NOTE: The specificreaction rate k2C is defined with respect to species C.

example b liquid phase cstr1
Example B: LiquidPhase CSTR

The complexliquidphasereactionstakeplace in a 2,500 dm3 CSTR. The feed is equal molar in A and B with FA0=200 mol/min, the volumetric flow rate is 100 dm3/min and the reationvolume is 50 dm3.

Find the concentrations of A, B, C and D existing in the reactoralong with the existingselectivity.

Plot FA, FB, FC, FD and SC/D as a function of V

example b liquid phase cstr2
Example B: LiquidPhase CSTR

Solution

Liquid CSTR

MoleBalances:

(1)

(2)

Net Rates:

(3)

(5)

(4)

selectivity
Selectivity

Ifonewere to write SC/D=FC/FD in the Polymath program, Polymathwould not executebecause at V=0, FC=0 resulting in an undefinedvolume (infinity) at V=0. To get around this problem we start the calculation 10-4 dm3 from the reactorentrancewhere FDwill not be zero and use the following IF statement.

(15)

selectivity1
Selectivity

Stoichiometry:

(16)

(17)

(18)

Parameters:

(19)

(20)

(21)

(22)

slide26

Example 1: Safety in Chemical Reactors

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

rearranging
Rearranging:

Additional information (approximate but close to the real case):

complete conversion f a 0
Complete conversion FA = 0
  • Batch Reactors with Heat Effects
      • Single Reactions
      • Multiple Reactions
  • Risk Rupture
keeping mbas away from chemical reactors
Keeping MBAs Away From Chemical Reactors
  • The process worked for 19 years before they showed up!
  • Why did they come?
  • What did they want?
nitroaniline synthesis reaction

NO2

NO2

Cl

NH2

+ 2NH3

+ NH4Cl

ONCB + Ammonia Nitroanaline + Ammonium

Chloride

Nitroaniline Synthesis Reaction
nitroaniline synthesis process

NH3 in H2O

ONCB

Autoclave

175 oC

~550 psi

NH3

Separation

Filter

Press

O-Nitroaniline Product Stream

“fast” Orange

Nitroaniline Synthesis Process

To Crystallizing Tanks

nitroaniline synthesis reactor

Old

3 kmol ONCB

43 kmol Ammonia

100 kmol Water

V = 3.25 m3

Nitroaniline Synthesis Reactor
nitroaniline synthesis reaction1

NO2

NO2

Cl

NH2

+ 2NH3

+ NH4Cl

ONCB + Ammonia Nitroanaline + Ammonium

Chloride

Nitroaniline Synthesis Reaction

Batch Reactor, 24 hour reaction time

Management said:TRIPLE PRODUCTION

mba style nitroaniline synthesis reactor

New

9 kmol ONCB

33 kmol Ammonia

100 kmol Water

V = 5 m3

MBA Style Nitroaniline Synthesis Reactor
temperature time trajectory

400

Temperature oC

Cooling Restored

Isothermal

Operation

200

175

9:55

t = 0

10:40 10:50

midnight 12:18

Temperature-time trajectory

fuse