(G = 0.126
kg·m-2·s-1, L = 15
kg·m-2·s-1)
Figure 6 shows the effect of the solid flow rate on the dynamic liquid
holdup at different liquid mass flow rates in the three-phase moving
bed. As evident in these figures,
the
dynamic liquid holdup increases with the liquid mass flow rate. On the
contrary, the dynamic liquid holdup decreases with the gas mass flow
rate because of the displacement of the liquid phase by the gas phase.
Such trends are in agreement with the observation in the trickle bed by
Larchi et al.42. It should be noted that the dynamic
liquid holdup all decreases with the solid flow rate at any given gas
and liquid mass flow rates. In other words, the dynamic liquid holdup is
noticeably influenced by the value of the solid flow rate under the
operating conditions near the flow regime boundary. Therefore, when the
bed is operated in the pulse flow regime and the particles start to
move, the dynamic liquid holdup will decrease to a steady value lower
than that to initiate the pulse flow. In details, the liquid film on the
particles, which is proportional to the dynamic liquid
holdup43, is too thin to collapse in the interstices
between the particles, so no pulses can be formed any more. The
influence of the solid flow rate on the dynamic liquid holdup gives us a
qualitative explanation for the transition boundary shift in Figure 4.