Module Catalogue 2024/25

Pre Requisite Comment

N/A

Co Requisite Comment

N/A

Aims

We start by showing how material balances should be performed for the three fundamental reactor types used in reaction engineering, namely the plug-flow reactor (PFR), the continuous stirred tank reactor (CSTR) and the perfectly-mixed batch reactor. We will see how these material balances can be used to design (by this we primarily mean how to calculate their volume or residence time) reactors when one reaction is taking place. We will also compare the behaviour of the different reactors. We will proceed to look at how the design process must be modified when more than one reaction is occurring. Further, we introduce and discuss behaviour of non-ideal reactors; this is intended to illustrate the limitations of always assuming that reactors behave in an ideal manner. This will allow us to calculate the residence time and conversion of any reactions in real reactors. Finally, we will see that reactors need not be isothermal. Therefore, we need to look at how reaction rate depends upon temperature for different classes of reaction. Then we will formulate the energy balance for the simple reactor models to show importance of energy balance in reactor design.

At the end of the course the student’s attitude should move away from:
‘All reactors are too complex to model’ or ‘All reactors are either perfectly mixed or plug flow’,
Towards:
‘It is possible to describe chemical reactors using models. However, all models have limitations. It is an engineer’s responsibility to be aware of these limitations and to choose a model which is of sufficient complexity to give an answer of the required accuracy’.

Outline Of Syllabus

Reactors

Introduction to batch and continuous reactor operation, batch reactor design equation Plug flow reactor design equation

CSTR design equation Single reactions
Constant pressure and constant volume batch reactors Plug flow reactors
Problem class on PFRs CSTRs
Comparison of PFR and CSTR and CSTRs in series

Similarity between series of CSTRs and PFR Recycle reactor
Multiple reactions
Introduction to multiple reactions, parallel reaction of the same order, parallel reactions of different orders; Consecutive reactions

Non-ideal reactors

Non-ideal reactors, residence time distribution (RTD) Calculation of conversion from RTD
Effect of temperature on reaction rate

Energy balance for the reactors: brief introduction Energy balance problem class
Use of MATLAB to solve system of ODEs for reactor problems

Intended Knowledge Outcomes

At the end of the course the student should know

The difference between batch, semi-batch and continuous modes of operation (AHEP4 C2, C1);

The principles of perfect mixing and plug flow and how they relate to the three basic reactor models used in the course (AHEP4 C2, C1):

Perfectly mixed batch reactor Continuous stirred tank reactor(CSTR)
Plug flow reactor (PFR) (AHEP4 C1-C5);
;

That an infinite number of CSTRs in series behave like a PFR and that a PFR with infinite recycle rate behaves like a CSTR (AHEP4 C1-C5, C13);

That, for a first order reaction a PFR will give a greater conversion than a CSTR because of the higher effective working concentration of reactants (AHEP4 C1-C5, C13);

The definitions of selectivity and yield when multiple reactions occur (AHEP4 C1, C2, C13);

Qualitatively, how the concentrations of reaction intermediates in a series reaction may vary with reactor residence time (AHEP4 C1-C5);

In what manner reaction rates are influenced by changing temperature and composition.

Intended Skill Outcomes

At the end of the course the student should be able to

Perform mass balances for the basic reactor models so as to derive the appropriate design equation from first principles (AHEP4 C1-C5);

Apply the basic reactor models for the design of isothermal reactors given any set of reaction kinetics (AHEP4 C1-C5);

Perform energy balances for the basic reactor models as necessary (AHEP4 C1-C5);

Apply basic reactor models for the design of isothermal reactors when multiple reactions are taking place (AHEP4 C1-C5);

In the case of multiple reactions, find the optimum reactor type and residence time for given kinetic behaviour and economic constraints (AHEP4 C1-C5, C13);

Design more complex reactor networks, e.g. reactors in series and parallel (AHEP4 C1-C5, C13);
Generate more complex reactor models as necessary (AHEP4 M1-M5);
Critically evaluate the applicability and limitations of any reactor model for a given purpose (AHEP4 M1-M5, M13).

Teaching Rationale And Relationship

Lectures introduce theoretical concepts and MATLAB skills that will be practiced in tutorials and online quizzes. The formative assessment with MATLAB skills provides a tool to apply knowledge gained together with knowledge from other modules, to solve more complex, realistic problem not possible to solve analytically

Assessment Rationale And Relationship

Examination assesses the knowledge and skills gained on closed problems where all necessary information is supplied. The assignment allows students to develop crucial skills in using matlab to solve ODEs for the design of more complex reaction systems.

General Notes

N/A