Chemical Reaction Engineering (Homogeneous Reactions in Ideal Reactors) - Chapter 3. Ideal Reactors for a Single Reaction - Mai Thanh Phong, Ph.D

Nội dung text: Chemical Reaction Engineering (Homogeneous Reactions in Ideal Reactors) - Chapter 3. Ideal Reactors for a Single Reaction - Mai Thanh Phong, Ph.D

1. Chapter 3. Ideal Reactors for a Single Reaction 1. Material and energy balances The starting point for all design is the material balance expressed for any reactant (or product). Figure 3.1 Material balance for an element of volume of the reactor. Thus, as illustrated in Fig. 3.1, we have Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 2
2. Chapter 3. Ideal Reactors for a Single Reaction In this chapter we develop the performance equations for a single fluid reacting in the three ideal reactors shown in Fig. 3.3. We call these homogeneous reactions. Figure 3.3 The three types of ideal reactors: (a) batch reactor, or BR; (b) plug flow reactor, or PFR; and (c) continuously stirred tank reactor, or CSTR. Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 4
3. Chapter 3. Ideal Reactors for a Single Reaction n n n (3.2) By replacing these two terms in Eq. 3.1, we obtain n (3.3) Rearranging and integrating then gives n (3.4) If the density of the fluid remains constant, we obtain with (3.5) Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 6
4. Chapter 3. Ideal Reactors for a Single Reaction By selecting reactant A for consideration, material balance for a CSTR can be written as follows (3.7) As shown in Fig. 3.4, if FA0 = v0CA0 is the molar feed rate of component A to the reactor, then considering the reactor as a whole we have Introducing these three terms into Eq. 3.7, we obtain (3.8) Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 8
5. Chapter 3. Ideal Reactors for a Single Reaction More generally, if the feed on which conversion is based, subscript 0, enters the reactor partially converted, subscript i, and leaves at conditions given by subscript f, we have (3.10) For the case of constant-density systems XA = 1 – CA/CA0: (3.11) Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 10
6. Chapter 3. Ideal Reactors for a Single Reaction 4. Plug flow tubular reactor (PFTR) Figure 3.6 Notation for a plug flow tubular reactor. At the steady-state, the material balance for reactant A becomes (3.12) Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 12
7. Chapter 3. Ideal Reactors for a Single Reaction For the reactor as a whole the expression must be integrated. Grouping the terms accordingly, we obtain Thus (3.14) For a more general expression, we have (3.15) Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 14
8. Chapter 3. Ideal Reactors for a Single Reaction 3.14 3.16 Figure 3.7 Graphical representation of the performance equations for plug flow tubular reactors. Fig. 3.7 displays these performance equations and shows that the space-time needed for any particular duty can always be found by numerical or graphical Integration. Mai Thanh Phong - HCMUT Chemical Reaction Engineering 30-Dec-22 16