Abstract
Barbotage reactors such as airlift reactors (ALR) and bubble column reactors (BCR), due to their two-phase flow systems, were investigated in many research papers. In their basic design variants, they are typically used to lift, mix, and aerate liquids, while, when equipped with additional elements in hybrid variants, their individual properties, i.e., lifting, mixing, and aeration of liquids, can significantly change with the same reactor geometry. The object of this study was to develop a hybrid barbotage reactor in various structural design variants. The structure consisted of a barbotage column of 50 mm in diameter, used to transport a water–air mixture outside the reactor (so-called external loop). The installation was additionally equipped with a nozzle in order to improve mixture aeration and circulation efficiency. The nozzle was mounted at various heights of the column pump segment. Additionally, the reactor was equipped with s moving bed in two variants (20% and 40% reactor capacity) in order to determine its effect on the mixture aeration and circulation conditions. Based on the measurement results, aeration curves were prepared for various structural design and column packing variants of the reactor. Properties of the two-phase mixture were determined for both parts—ALR and BCR. Technological and energy parameters of the aeration process were calculated, and the results obtained for the individual structural design variants were compared. It was found that, for the most advantageous design, in terms of aeration efficiency, the aeration nozzle should be placed in the mid-length of the pump segment of the barbotage column, irrespective of the hybrid reactor packing rate with the moving bed. The reactor packing with the moving bed resulted in a decreased mean water velocity in the reactor. For most analyzed structural design variants, the respective packing with the moving bed had no significant effect on aeration efficiency. Only for one structural design variant did the lack of packing significantly improve oxygen levels by as much as approximately 41%.
Highlights
Various factors influence water aeration processes, both directly and indirectly
The term barbotage refers to the flow of many gas bubbles through the liquid layer. This phenomenon is found in airlift reactors (ALR), airlift pumps (ALP), bubble column reactors (BCR), etc
The aim of this study was to determine the effect of structural design variants and the moving bed packing in a barbotage hybrid reactor on hydraulic conditions and aeration efficiency
Summary
Various factors influence water aeration processes, both directly and indirectly. Oxygen solubility in water depends mainly on water temperature and the intensity of mixing, rather than atmospheric pressure and salinity [1,2,3]. An increase in water temperature causes a significant decrease in the amount of oxygen dissolved in water. An increase in circulation (mixing) intensity supports aeration and oxygen transfer [4,5]. The term barbotage refers to the flow of many gas bubbles through the liquid layer. This phenomenon is found in airlift reactors (ALR), airlift pumps (ALP), bubble column reactors (BCR), etc
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