Page 92 - Elements of Chemical Reaction Engineering 3rd Edition

64 Conversion and Reactor Sizing Chap. 2

P2-8B Figure P2-8a shows cAo/-rA versus XA for a nonisothermal, nonelementary,
multiple-reaction liquid-phase decomposition of reactant A.

t r l l l . I l r r
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0,8 0.9
Conversion, X
(a 1

)--t-X =0.7
;
X? = 0.3

(bl X =0.7
Figure P2-8

(a) Consider the two systems shown in Figure P2-8b in which a CSTR and
plug-flow reactor are connected in senes. The intermediate conversion is
0.3 and the final conversion is 0.7. How should the reactors be arranged
to obtain the minimum total reactor volume? Explain.
(b) If the volumetric flow rate is 50 L/min, what is the minimum total reac-
tor volume? (Ans. V = 750 dm3)
(e) Is there a better means (Le., smallest total volume achieving 70% conver-
sion other than either of the systems proposed above? (Am.: 512 L)
(d) At what conversion(s) would the required reactor volume be identical for
either a CSTR or a tubular PFR? (Am.: X = 0.45, and X = ?)
(e) Using the information in Figure P2-8a together with the CSTR design
equation, make a plot of t versus X. If the reactor volume is 700 L and
the volumetric flow rate 50 Wmin, what are the possible outlet conver-
sions (Le., multiple steady states) for this reactor?