Lecture 21
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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

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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

Unsteady State Energy balance

Neglect

Using


Lecture 21

Unsteady State Energy balance

We obtain after some manipulation:

Collecting terms with and high coolant flow rates,and


Unsteady state energy balance1

Unsteady State Energy balance


Unsteady state energy balance2

Unsteady State Energy balance


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


Lecture 21

Energy balance for CSTRs

κ=∞

R(T)

κ=0

T0

Increase κ

Ta

T

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


Lecture 21

1) Mole Balance:

2) Rate Law:


Lecture 21

3) Stoichiometry:

4) Combine:


Lecture 21

Multiple Steady States (MSS)

Variation of heat generation curve with space-time.


Lecture 21

Multiple Steady States

Finding Multiple Steady States with T0 varied


Lecture 21

Multiple Steady States

Finding Multiple Steady States with T0 varied


Lecture 21

Multiple Steady States

Temperature ignition-extinction curve


Lecture 21

Multiple Steady States

Stability of multiple state temperatures


Lecture 21

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

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


Lecture 21

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

For a first order irreversible reaction

Parameters

Thenplot G and R as a function of T.


End of lecture 21

End of Lecture 21


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