Influence of internals on counter-current bubble column hydrodynamics: Holdup, flow regime transition and local flow properties

The effect of Alcanivorax borkumensis SK2, a hydrocarbon-metabolising organism, on gas holdup in a 4-phase bubble column bioprocess

To design bioprocesses utilising hydrocarbon-metabolising organisms (HMO) as biocatalysts, the effect of the organism on the hydrodynamics of bubble column reactor (BCR), such as gas holdup, needs to be investigated. Therefore, this study investigates the first use of an HMO, Alcanivorax borkumensis SK2, as a solid phase in the operation and hydrodynamics of a BCR. The study investigated the gas holdup in 3-phase and 4-phase systems in a BCR under ranges of superficial gas velocities (U_G) from 1 to 3 cm/s, hydrocarbon (chain length C₁₃-₂₁) concentrations (H_C) of 0, 5, and 10% v/v and microbial concentrations (M_C) of 0, 0.35, 0.6 g/l. The results indicated that U_G was the most significant parameter, as gas holdup increases linearly with increasing U_G from 1 to 3 cm/s. Furthermore, the addition of hydrocarbons into the air-deionized water -SK2 system showed the highest increase in the gas holdup, particularly at high U_G (above 2 cm/s). The solids (yeast, cornflour, and SK2) phases had differing effects on gas holdup, potentially due to the difference in surface activity. In this work, SK2 addition caused a reduction in the fluid surface tension in the bioprocess which therefore resulted in an increase in the gas holdup in BCR. This work builds upon previous investigations in optimising the hydrodynamics for bubble column hydrocarbon bioprocesses for the application of alkane bioactivation.

Study of the Impact of Tube Configurations on the Local Heat Transfer Coefficient in Mimicked Fischer-Tropsch Bubble Column Reactor

An experimental investigation was conducted to examine, for the first time, the influences of using different designs of tube arrangements on the local heat transfer coefficient (LHTC) in a bubble column (with a diameter of 0.13 m) equipped densely with a bundle of tubes. The effect of using two different designs of tube arrangements has been examined for a broad range of gas flow rates using a sophisticated heat transfer technique. The obtained results indicate that the LHTC increases significantly with increasing the gas velocity, regardless of the design and installation of the tubes in the column. Additionally, the shape of the LHTC’s profiles alters considerably by the presence of a bundle of tubes and their arrangements. Moreover, the results indicate that the square tube pitch arrangement provides uniform heat transfer profiles, which enhance the performance of the bubble column reactor by 30%. Furthermore, the heat transfer profiles were found to be varied with the axial height of the column. The new experimental results obtained in this investigation will provide experimental reference data for creating and validating a mathematical model for predicting LHTCs. In addition, this will facilitate this kind of reactor’s design, scale-up, and operation.