Programme:
Total of 36 hours lectures, 3 x 2 hours laboratories.
Starting knowledge required:
It is expected that all students have at least entry university level knowledge of mathematics in order to be comfortable with the use of differential calculus in various situations and to be able to perform simple mathematical analytical and numerical derivation/integration.
The students should have been previously exposed with the concepts of material and energy balances and should be able to apply these in unfamiliar circumstances. The students should also have some knowledge of fluid dynamics and thermodynamics for an appreciation of fluid flow, reaction equilibria, heats of reaction, and energy balances.
Scope:
This course consists of two main parts:
1. In the first part of this course, all reactions are presented as being homogeneous reactions and reaction rates are always presented as being volume specific.
As some students may not have come across reaction kinetics before, this part will start with a short introduction, which, will give a definition to the three fundamental reactor types used in reaction engineering and show how material balances should be performed for them. We will investigate how these material balances can be used to design reactors by calculating their volume or residence time. During the course, 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. We will understand that reactors do not need to 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 given reactors and use this to investigate the variation of temperature and therefore reaction rate with time or position in the reactor. As a result, this will be used to allow us to calculate reactor volumes and residence times for a given duty. We will discuss non-ideal reactors; this is intended to illustrate the limitations of always assuming that reactors behave in an ideal manner. This section includes the calculation of the residence time required for attaining the desired conversion of solid reactant in a PFR and CSTR with a simple distribution of particle sizes.
2. In the second part of this course, all reactions are presented as being heterogeneous reactions, which is in turn divided into main sub-categories: catalytic and non-catalytic. In the case of catalytic reactions, the reaction rates are presented in different expressions but mainly being specific to the mass of catalyst used.
This part will start with a short introduction to define a heterogeneous reaction and explain its types. Conversion between different bases used for reaction rate expressions is essential to derive the overall rate of reaction for an in-series linear process and to explain the difference between the true and overall rate of reaction. Following this introduction, the course will proceed with explaining the seven steps in a heterogeneous catalytic reaction. This includes the inter-dependence interaction between mass transfer & reaction, rate limiting step, and development of mass balance over a catalytic pore.
The calculation part starts with modelling internal and external steps in heterogeneous catalysis and estimating Thiele Modulus and internal effectiveness factor in a single pore of catalyst for a first order reaction. Once the main formulae being derived, it can be further extended to cover the concentration gradient in the entire catalyst particle and to apply the generalized Thiele Modulus. We will explain how non-isothermal behavior (exothermic or endothermic) affects the rate of heterogeneous catalytic reactions.
Advantages and disadvantages of different types of heterogeneous reactors will be discussed to perform calculations of conversion in a packed bed, fluidized bed, continuously stirred and batch reactor. In this frame, applications of Carman-Kozeny equation and Ergun equation will be presented to describe laminar and turbulent flow through randomly packed particles. This explanation will help to calculate particle size and specific surface area of particles, rate of flow of fluid through a packed bed, pressure drop to drive fluid through a packed bed, the superficial liquid velocity at incipient fluidization, and minimum and maximum flow rate in a fluidized bed, reactor diameter and height for fluidization operations.
We shall define the activity of a catalyst and explain the different mechanisms behind catalyst deactivation and which are reversible through catalyst regeneration. The calculation part here includes the catalyst deactivation rate, and how this affects reactor performance, the conversion of a reactant in presence of deactivation and the run time for one cycle of catalyst deactivation. We shall also contrast and compare models to describe fluid-solid non-catalysed reactions.