Sparger Type Influence on the Hydrodynamics of the Draft Tube Airlift Reactor with Diluted Alcohol Solutions

Abstract

The objective of this work was to investigate the influence of normal aliphatic alcohols (from methanol to n-octanol) and the gas sparger type (single orifice, perforated plate, and sinter plate) on the hydrodynamics of a draft tube airlift reactor. The results showed that the presence of alcohols led to both an increase in the gas holdup and reduction of the downcomer liquid velocity, in comparison to the values obtained in water. The type of gas sparger also changed the hydrodynamic behaviorthe gas holdup increased with dispersion effectiveness, from single orifice to sinter plate, while the effect on the downcomer liquid velocity was in conjunction with the liquid phase properties. Simple correlations were developed to predict the gas holdup and the downcomer liquid velocity. Beside the gas superficial velocity, the proposed correlations include the surface tension gradient, as a unique parameter which represents the liquid phase properties, and sparger related variables: the ratio of the sparger’s total openings area and the draft tube cross-sectional area and also orifice (pore) size of the sparger.

Influence of the Sparger Type and Added Alcohol on the Gas Holdup of an External‐Loop Airlift Reactor

“…They reported that the sparger design has a noticeable effect on the gas holdup at low gas velocities (< 0.025 m s -1 ) and low solids loading (< 2 %), but only a slight effect at high gas velocities (> 0.030 m s -1 ) and high solids loading (> 3 %). Similar observations were reported by Šijački et al [7]. At lower gas velocities, they reported the highest gas holdup values in a two-phase ILAR, obtained with a sinter plate, compared to perforated-plate and single-orifice spargers.…”

“…To apply the model that covers the whole range of ELAR sizes (see Tab. 2), the geometrical parameter A d /A r must be included. In previous investigations, we successfully fitted experimental values with these parameters by using correlations [4,12,13,37]. The general form of the applied power law correlations was:…”

“…Freitas and Teixeira [10] and Miyahara and Nagatani [5] found that the only property of alcohol solutions that differed considerably from water was their surface tension. Also, it was observed that the gas holdup, and therefore the mass transfer coefficient, increased with increasing number of carbons in the alcohols and the concentration of the alcohols [11][12][13]. Further, alcohol solutions have been used to simulate the liquid phase in coal liquefaction and in bioreactors due to the presence of non-coalescing organic mixtures [14].…”

“…However, in the range of relatively low gas velocities, the gas holdup for singlehole plates with a large hole diameter was quite small. Correlations for the prediction of the gas holdup in airlift reactors have been proposed in various forms, based on investigations on different gas-liquid systems [7,14,17,[19][20][21][22][23]. The equations are based on empirical models, the energy balance, the momentum balance in the reactor, or the drift flux model.…”

Gas holdup, bubble size distribution, and mass transfer in an airlift reactor with ceramic membrane and perforated plate distributor

“…After that, researchers further compared the performance of the reactors equipped with micro‐bubble spargers and millimetre‐sized bubble spargers. [ 55–58 ] Wang et al explored the differences in the mass transfer characteristics of the oxygen‐water system between the micro oxygen bubbles and millimetre‐sized oxygen bubbles in a co‐current bubble column. [ 55 ] They found that micro‐bubbles can provide a larger interfacial area in comparison to the millimetre‐sized bubbles, and therefore, the volumetric oxygen mass transfer coefficient with micro oxygen bubbles increased significantly.…”