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Lecture 21. 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. CSTR With Heat Effects Multiple Steady States Ignition and Extinction Temperatures.

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Lecture 21

Lecture 21

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

  • CSTR With Heat Effects

    • Multiple Steady States

    • Ignition and Extinction Temperatures


Cstr with heat effects
CSTR with Heat Effects

Courtesy of Pfaudler, Inc.



Unsteady State Energy balance

We obtain after some manipulation:

Collecting terms with and high coolant flow rates, and




Unsteady state energy balance3
Unsteady State Energy balance

If G(T) > R(T) TemperatureIncreases

If R(T) > G(T) TemperatureDecreases


Steady state energy balance for cstrs
Steady State Energy balance for CSTRs

At Steady State

Solving for X.


Steady state energy balance for cstrs1
Steady State Energy balance for CSTRs

Solving for X

Solving for T


Energy balance for cstrs
Energy balance for CSTRs


Energy balance for cstrs1
Energy balance for CSTRs


Energy balance for cstrs2
Energy balance for CSTRs

Increasing T0

R(T)

Variation of heat removal line with inlettemperature.

T


Energy balance for CSTRs

κ=∞

R(T)

κ=0

T0

Increase κ

Ta

T

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


1) Mole Balance:

2) Rate Law:


3) Stoichiometry:

4) Combine:


Multiple Steady States (MSS)

Variation of heat generation curve with space-time.


Multiple Steady States

Finding Multiple Steady States with T0 varied


Multiple Steady States

Finding Multiple Steady States with T0 varied


Multiple Steady States

Temperature ignition-extinction curve


Multiple Steady States

Stability of multiple state temperatures


MSS - Generating G(T) and R(T)

Need to solve for X after combining mole balance rate law and stoichiometry.


MSS - Generating G(T) and R(T)

For a first order irreversible reaction

Parameters

Thenplot G and R as a function of T.



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