(64e) Flow Regime Identification in Trickle Bed Reactor By Gamma Densitometry

Trickle bed reactors are packed beds in which gas and liquid reactants flow concurrently down. These reactors are very flexible with respect to varying the gas and liquid flow rates to get the trickling and pulsing flow regimes. The ratio of liquid to solid is small, which is advantageous in preventing homogeneous side reactions. Unfortunately, trickle beds can suffer serious drawbacks such as liquid mal-distribution, which reduces the expected conversion and can lead to hot spots. To address such problems, detailed studies to enhance the understanding of the hydrodynamics in the trickle bed reactor are still required. In this work, the possibility of flow regime identification and monitoring and phase holdup determination by use of gamma densitometry was examined in trickle bed reactor. The experimental work was carried out in 0.14 m diameter Plexiglas column for an air-water system flowing over a packed bed of glass bead solids. The trickle bed reactor was scanned by a gamma radioactive source of Caesium-137 and detected by a NaI(Tl) detector. The scan was conducted in various axial and radial positions with the superficial liquid flow rate in the range 0.004 - 0.014 m/s and superficial gas flow rate in the range 0.03 - 0.22 m/s covering the trickling flow regime through pulsing flow regime. Various types of liquid inlets such as single inlet in the center, single inlet near the column wall and a full shower inlet were used. In addition, the phase holdup studies were also conducted. The results obtained show that the gamma densitometry technique can be used to monitor and indentify the flow regimes in a trickle bed reactor and to determine the phase holdup.