Page 491 - Elements of Chemical Reaction Engineering Ebook

462 Steady-State Nonisothermal Reactor Design Chap. 8

TABLE 8-3. (CONTINUED) PFRlPBR ALGORITHM FOR HEAT EFFECTS
Vyiable Coolant Temperature 3. Stoichiometry (gas phase, no AP):
rB = rA (T8-3.12)
rc = 2rA (T8-3.13)
FA To
c, = c, - - (T8-3.14)
FT
c, = c,, - - (T8-3.15)
0

FB '
Fr T
Fc To
c, = CT0 - - (T8-3.16)
Fr T
4. Energy balance:
(T8-3.17)
If the coolant temperature T,, is not constant then the energy balance on the coolant fluid gives
(T8-3.18)

where is the mass flow rate of the coolant (e.g. kg/s., and C, is the heat capacity of the cool-
ant, (e.g., JnCg-K). (See the CD ROM for the examples in lectures 15 & 16 and the Polymath
Libary' for the case when the ambient temperature is not constant.)
k,, E, R, Cm, T,, To, Ti, Tz, K,, OB, CpA, Cpsq Cpc, ua
Example Problem Pb T-8.3
Enter intial values: FAO, Fm, Fm, Fm, To and final values : V, =
Use ODE solver.

Example 8-7 Production of Acetic Anhydride

Jeffreys? in a treatment of the design of an acetic anhydride manufacturing facility,
states that one of the key steps is the vapor-phase cracking of acetone to ketene and
methane:

CH,COCH, + CHZCO + CH,

He states further that this reaction is first-order with respect to acetone and that the
specific reaction rate can be expressed by

Ink = 34.34 - - (E8-7.1)
34,222
T
where k is in reciprocal seconds and Tis in kelvin. In this design it is desired to feed
8000 kg of acetone per hour to a tubular reactor. The reactor consists of a bank of
1000 1-inch schedule 40 tubes. We will consider two cases:
1. The reactor is operated adiabatically.

G. V. Jeffreys, A Problem in Chemical Engineering Design: The Manufacture of Ace-
tic Anhyride, 2nd ed. (London: Institution of Chemical Engineers, 1964).