The influences of alcohol adding and three different gas spargers (single orifice, perforated plate, and sinter plate) on the gas holdup in an external-loop airlift reactor were studied. The experimental results show that the gas holdup can be increased by mutual influence of both the alcohol adding and the sparger type. The presence of small amounts of normal aliphatic alcohols caused an increase of the gas holdup compared to the air-water system, due to their coalescence-inhibiting nature. The sinter plate was the most efficient sparger, followed by the perforated plate and the single orifice. A proposed artificial neural network (ANN) has the potential to predict gas holdup values in airlift reactors for various alcohols and types of gas spargers.
-The objective of this study was to investigate the hydrodynamics of an external-loop airlift membrane reactor (ELAMR). The ELAMR was operated in two modes: without (mode A) and with bubbles in the downcomer (mode B), depending on the liquid level in the gas separator. The influence of the gas distributor's geometry and various alcohol solutions on the hydrodynamics of the ELAMR was studied. Results for the gas holdup and the downcomer liquid velocity are commented with respect to an external-loop airlift reactor of the same geometry but without the membrane in the downcomer (ELAR). Due to the presence of the membrane in the downcomer, acting as the local hydrodynamic resistance, the gas holdup in the riser of the ELAMR increases maximally by 16%, while the liquid velocity in the downcomer decreases up to 50%. The values of the gas holdup and liquid velocity predicted by the application of empirical power law correlations and a feed forward back propagation neural network (ANN) are in very good agreement with experimental values.
The effects of the inserted membrane in the downcomer of an external-loop
airlift reactor, the gas sparger type (single orifice and sinter plate) and
added alcohol (ethanol, n-butanol, or n-hexanol) on the volumetric gas-liquid
mass transfer coefficient (kLa) were studied. Due to the presence of the
membrane in the downcomer, kLa did not change significantly; the differences
were smaller than 10%. The highest values of the kLa were obtained using the
sinter plate. It was found that the addition of small amounts of alcohol
increased the mass transfer. Using our experimental results and the data of
other authors, the feed-forward back propagation neural network for
prediction of kLa in external-loop airlift reactors with alcohol solutions
was proposed. [Projekat Ministarstva nauke Republike Srbije, br. 172025]
This paper is concerned with numerical study of fluid flow through a pair of corrugated platest. The aim was to observe and understand the behavior of the flow and vortex formation through channels where the fluid is subjected to a periodic increase and decrease in cross-section area. The plates modeled for the study had sinusoidal profiles. A pair of plates with 180° phase shift was simulated in two-dimensional spaces. The Reynolds number was a function of the average plate spacing (Havg) and the laminar flow velocity and it was in the range between 200 and 1000
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