Page 44 - Elements of Chemical Reaction Engineering 3rd Edition

16 Mole Balances Chap. 1
1 Rearranging gives

1 Using the conditions at the entrance of the reactor that when V = 0, then CA = CAo,

I A-B
(El-3.4)

This equation gives

(El -3.5)
1 Substituting CA,, CA, uo, and k in Equation (El-3.5), we have

10 dm3/min In--- - lo dn13 In 10 = 100 dm3 (i.e., 100 L; 0.1 m3)
0.23 min-’ O.lCAo 0.23
We see that a reactor volume of 0.1 m3 is necessary to convert 90% of species A
entering into product B.

In the remainder of this chapter we look at slightly more detailed draw-
ings of some typical industrial reactors and point out a few of the advantages
and disadvantages of each.

1.5 Industrial Reactors
A batcfi reactor is used for small-scale operation, for testieg new processes that
When is a hatch
reactor used? have not been fully developed, for the manufacture of expensive products, and
for processes that are difficult to convert to continuous operations. The reactor
can be charged (i.e., filled) throughihe holes at the top (Figure 1-8). The batch
reactor has the advantage of high conversions that can be obtained by leaving
the reactant in the reactor for long periods of time, but it also has the disadvan-
tages of high labor costs per batch and the difficulty of large-scale production.

Liquid-Phase Reactions. Although a semibatch reactor (Figure 1-9) has
essentially the same disadvantages as the batch reactor, il has the advantages of
good temperature control and the capability of minimizing unwanted side reac-
tions through the maintenance of a low concentration of one of the reactants.
The semibatch reactor is also used for two-phase reactions in which a gas is
usually bubbled continuously through the liquid.
What are the A continuous-stirred tank reactor (CSTR) is used when intense agitation
advantages and
disadvantages of a is required. A photo showing a cutaway view of a Pfaudler CSTRhatch reactor
CSTR? is presented in Figure 1-10. Table 1-1 gives the typical sizes (along with that of

Chem. Eng., 63(10), 211 (1956). See also AIChE Modular Instruction Series E, Vol.
5 (1984).