Page 115 - Elements of Chemical Reaction Engineering 3rd Edition

Sec. 3.3 Stoichiometric Table I 87

(3-24)

,
We further simplify these equations by defining the parameter Oi which
allows us to factor N,, in each of the expressions,for concentration:

@ -- (3-25)
NBO
B-
NAO

We need V(X) to We now need only to finc volume as a function of conversion to c,tain the
obtain C, h,(X) species concentration as a function of conversion.

3,,3.2 Constant-Volume Reaction Systems
Some significant simplifications in the reactor design equations are pos-
sible when the reacting system undergoes no change in volume as the reaction
progresses. These systems are called constant-volume, or constant-density,
because of the invariance of either volume or density during the reaction pro-
cess. This situation may arise from several causes. In gas-phase batch systems,
the reactor is usually a sealed vessel with appropriate instruments to measure
pressure and temperature within the reactor. The volume within this vessel is
fixed and will not change, and is therefore a constant-volume system. The lab-
oratory bomb reactor is a typical example of this type of reactor.
Another example of a constant-volume gas-phase isothermal reaction
occurs when the number of moles of product equals the number of moles of
reactant. The water-gas shift reaction, important in coal gasification and many
other processes, is one of these:
CO + H20 e
+
H,
C02