Experimental apparatus and
methods
The schematic of the experimental apparatus is shown in Figure 1a, which
mainly consists of two parts, a three-phase moving bed and a silo. The
three-phase moving bed is made of Plexiglass with an
inner
diameter of 129 mm and a bed height of 1100 mm. A gas distributor and
four liquid nozzles are installed at the top of the bed to ensure
uniform distribution of gas and liquid. The bed has a conical bottom
formed by the 2-mm mesh screen, and
a discharge pipe with an inner diameter of 30 mm is installed in the
center of the bottom. During the experiments, gas and liquid can flow
out of the bed through both the mesh screen and the discharge pipe,
while the particles can only flow out through the central discharge
pipe. A collector is equipped at the bottom of the bed to facilitate the
measurement of liquid distribution over the cross-section of the bed, as
shown in Figure 1b.
It
can be seen from the figure that the collector consists of three annular
rings dividing the cross-section of the bed into four annular sections,
and the dimensions of the annular areas and annular fractions are given
in Table 1. The rings extend into the
bed with different lengths to prevent the liquid from migrate radially
on the screen and form a 45-degree tapered slope to facilitate the
catalyst withdrawal. The upper edge of the rings is beveled to a fine
line to reduce the disturbance to the flow distribution caused by the
collector rings. Each annular section is filled with catalyst particles
to prevent overflow of liquid from one annular section to an adjacent
section.
Preliminary
measurements show no overflow within the range of gas and liquid mass
flow rates studied. Each annular section contains four discharge tubes
located symmetrically in the bottom plate. The discharge tube is
connected to a vessel which is open to the atmosphere to vent the air.
The liquid mass flow rate through each section is measured by sampling
and weighing within 15 s. A silo with an inner diameter of 1400 mm and a
height of 1200 mm is installed directly above the three-phase moving bed
to ensure a continuous and steady flow of particles during the
experiment. In order to balance the pressure of the system and ensure
the stable flow of the particles, the bed and the silo are connected by
a balance tube.