Abm. Heesink et al., THE INFLUENCE OF PARTICLE RESIDENCE TIME DISTRIBUTION ON THE REACTIVITY IN FLUIDIZED-BED REACTORS, Chemical Engineering Science, 49(14), 1994, pp. 2243-2261
The influence of particle residence time distribution on the average c
onversion rate (or reactivity) of particles undergoing a non-catalytic
ps-solid reaction inside a continuously operated fluidized bed reacto
r is evaluated. A so-called beta-factor is defined as the ratio of the
actual reactivity in the reactor and the reactivity of a batch of par
ticles that react under similar circumstances and that all have a conv
ersion extent equal to the average conversion extent in the reactor. T
he beta-factor concept is elaborated for shrinking core conversion beh
aviour. According to Heesink et al. (1993), three extreme types of con
version behaviour are distinguished: core reaction limitation, product
-layer diffusion limitation and grain reaction limitation. For each ty
pe of behaviour a mathematical function is derived that expresses beta
as function of average particle conversion, maximum attainable conver
sion (with regard to pore plugging) and a new-defined expansion factor
, which is a measure for the expansion (or shrinking) of the reacting
solid during conversion. These functions can be easily incorporated in
fluidized bed reactor models,