(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.