lecture notes lecture 1

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 Dr. Eid Al-Mutairi

CHE 402

Kinetics & Reactor

DesignFall 2008

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CHE 402- Dr. Eid Al-Mutairi

Instructor 

Dr. Eid Al-Mutairi Off: 16-266

Email: mutairi@kfupm.edu.sa

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CHE 402- Dr. Eid Al-Mutairi

Students

Who you are? Why you become chemical engineer?

What does “kinetics & rector design” meanto you?

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CHE 402- Dr. Eid Al-Mutairi

Chemical Engineering Field

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CHE 402- Dr. Eid Al-Mutairi

Reaction Kinetics & Reactor

Design

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CHE 402- Dr. Eid Al-Mutairi

Course Contents

 Addressing basic concepts of chemical reactionskinetics

Conversion and Reactor Sizing

Isothermal reactor design Collection and Analysis of Rate Data

Multiple reactions

Non-Isothermal Reactor Design Catalysis and Catalytic Reactors

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CHE 402- Dr. Eid Al-Mutairi

Grading Policy

Homework 10% Quizzes 10%

Major Exams 40% Final Exam 40%

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CHE 402- Dr. Eid Al-Mutairi

Chapter 1: Mole Balances Define the rate of chemical reaction.

 Apply the mole balance equations to a

batch reactor, CSTR, PFR, and PBR.

Describe two industrial reactionengineering systems.

Describe photos of real reactors.

Describe how to surf the CD-ROM

attached with this text.

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CHE 402- Dr. Eid Al-Mutairi

Chemical Reactions

Examples Types

Our life and chemical reactions

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CHE 402- Dr. Eid Al-Mutairi

Chemical Identity

 A chemical species is said to have reacted whenit has lost its chemical identity. The identity of achemical species is determined by the kind ,number  ,and configuration of that species'

atoms .

Three ways a chemical species can lose its chemical identity

decomposition combination isomerization 

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CHE 402- Dr. Eid Al-Mutairi

Reaction Rate

Measures how fast a number of moles ofone chemical species are consumed toform another chemical.

CCl3CHO + 2C6H5Cl (C6H4Cl)2CHCCl3+H2O

 A + 2B C+D

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CHE 402- Dr. Eid Al-Mutairi

Reaction Rate The reaction rate is the rate at which a species looses its chemical

identity per unit volume. The rate of a reaction can be expressed as

the rate of disappearance of a reactant or as the rate of appearanceof a product. Consider species A:

 A B

r  A = the rate of formation of species A per unit volume

- r  A = the rate of a disappearance of species A per unit volume

r B = the rate of formation of species B per unit volume

The rate of reaction, - r  A, is the number of moles of A reacting

(disappearing) per unit time per unit volume

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CHE 402- Dr. Eid Al-Mutairi

Reaction Rate: Example I

If B is being created Sat 0.2 moles per decimeter cubedper second, i.e,r B = 0.2 mole/dm3/s

Then A is disappearing at the same rate:-r  A = 0.2 mole/dm3/s

For a catalytic reaction, we refer to -r  A', which is the rateof disappearance of species A on a per mass of catalyst

basis.

 A B

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CHE 402- Dr. Eid Al-Mutairi

Reaction Rate

Consider species j:

r  j is the rate of formation of species j per unit volume [e.g.mol/dm3*s]

r  j is a function of concentration, temperature, pressure, and the typeof catalyst (if any)

r  j is independent of the type of reaction system (batch, plug flow,etc.)

r  j is an algebraic equation, not a differential equation

We use an algebraic equation to relate the rate of reaction, -rA, tothe concentration of reacting species and to the temperature at

which the reaction occurs [e.g. -r  A = k(T)C A

2

].

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CHE 402- Dr. Eid Al-Mutairi

Reaction Rate: Example II

e.g. -r  A = 4 mole/dm3/s

r  A = -4 mole/dm3/s

-r B = 8 mole/dm3/s

r B = -8 mole/dm3/s

r C = 4 mole/dm3/s

CCl3CHO + 2C6H5Cl (C6H4Cl)2CHCCl3+H2O

 A + 2B C+D

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Reactors

Plug Flow Reactor (PFR) or TubularReactor 

Continuous Stirred Tank Reactor (CSTR)

Batch Reactor 

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CHE 402- Dr. Eid Al-Mutairi

Industrial Reactor 

Sasol Advanced Synthol (SAS) Reactor 

Reactor System Used at Amoco

Fixed Bed Reactor 

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CHE 402- Dr. Eid Al-Mutairi

Batch Reactors Batch reactors are the simplest reactors used in

chemical processes.

Reactants are first placed inside the reactor and thenallowed to react over time.

 Applications: typically used for liquid phase reactions.

When only a small amount of product is desired (process in

testing phase OR product is expensive)

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CSTR CSTRs are very well mixed►contents

have uniform properties (temperature,

density, etc) Reactants are continuously introduced

into the reactor, while products are

continuously removed.

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PFR (Tubular)Plug flow or tubular reactors consist of a hollow pipe or tube

through which reactants and products to flow through.

 Applications: wide variety of operations (gas or liquid

phases)

Gasoline production

Oil cracking

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CHE 402- Dr. Eid Al-Mutairi

General Mole Balance Equation

IN - OUT + GENERATION = ACCUMULATION

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CHE 402- Dr. Eid Al-Mutairi

Mole Balance on Different Reactor Types

 PBR 

 PFR 

 CST

R 

 Batc

h

 Integral AlgebraicDifferential

Reac

to

r 

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CHE 402- Dr. Eid Al-Mutairi

Batch Mole Balance General Mole Balance on System Volume V

No inflow or outflow-

 Assumptions

Well mixed

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CHE 402- Dr. Eid Al-Mutairi

CSTR Mole Balance

General Mole Balance on System Volume V

 Assumptions

Steady State

Well mixed

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CHE 402- Dr. Eid Al-Mutairi

PFR Mole Balance

General Mole Balance on System Volume V

Steady State

Differentiate with respect to V