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.