(60m) Investigation of Flow Regimes in a Gas-Liquid-Solid Three-Phase Moving Bed Reactor

The trickle bed reactor is
a typical three-phase reactor widely used in chemical industries. Compared with other
three-phase reactors, trickle beds have a larger catalyst loading, which are
especially suitable for those large-scale processes. However, some disadvantages, including
the low catalyst utilization rate, serious diffusion resistance, and poor heat
transfer performance exist apparently in trickle bed reactors. In this work, a
gas-liquid-solid three-phase moving bed reactor was proposed on the basis of
typical trickle beds to supply a potential solution for some of those problems. In multi-phase
reactors, several
hydrodynamic and transport parameters such as pressure drop, liquid holdup,
interphase mass and heat transfer coefficients and interfacial area are
considerably related to the flow regime. Therefore, investigation on the flow
regime is regarded as one of the fundamentals to develop the gas-liquid-solid
three-phase moving bed reactor, which is just the target of this work.

In this work, a cold model
experimental device of the three-phase moving bed reactor was established, and
the flow regime in it was studied by image analysis taking the flow regime in
the trickle bed as a basis. The constructed flow regime map was shown in Figure
1. Results showed that as the particle velocity increased, the trickle flow
regime and transition zone increased, while the bubble flow regime decreased.
Taking the trickle flow as the initial flow regime, the flow channels of gas
and liquid were more obvious as the particle velocity increased. When the
initial flow regime was pulse flow, the alternation of the gas-rich zone and
liquid-rich zone was more obvious with the moving particles at low particle
velocities and the pulse-to-trickle flow transition occurred at high particle
velocities. When the initial flow regime was bubble flow, the bubble
coalescence occurred with the moving particles and the bubble-to-pulse flow
transition occurred at moderate-to-high particle velocities.

Figure 1. The
flow regime map in the three-phase moving bed. (a) Flow regime map, (b) u_S = 0 m/s,(c) u_S = 0.01 m/s, (d) u_S = 0.02 m/s.