REACTORS: IDEALIZED CHEMICAL REACTORS - Biomass as a Sustainable Energy Source for the Future - page 175

28L∙min -1 28L∙min -1 28L∙min -1

V=1L

V=1L

Unpopped
popcorn

Popped
popcorn

1L∙min -1
unpopped

1L∙min -1
unpopped

1L∙min -1
unpopped

FIGURE 6.7 Production of popcorn. For the same values of τ , the residence times t are
different in each case. Based on Levenspiel (1998).

In the three cases shown in Figure 6.7, the inlet and outlet flows are the same; the
only difference is the point inside the reactor where the corn pops. In the first case,
most of the corn pops close to the outlet of the reactor. In the second case, the corn
pops as soon as it enters the reactor. In the third case, it pops somewhere across the
reactor.
The time τ needed to convert a volume of reactor (1 L) of raw corn is the same in all

three cases:

τ 3 = V
φ V 0

τ 1 = τ 2 = = 1 min

However, in the first case, the corn moves slower than in the second case. The
residence times are

t 1 = V
φ V 1

1L
1L

=

min −1 = 1 min

t 2 = V
φ V 2

1L
28 L

=

min −1 '

2s

2s<t 3 <1min