Oxygen transfer in hydrocarbon-aqueous dispersions and its applicability to alkane bioprocesses: A review

Accumulation of alkane by-products from gas to liquid fuel processes presents an attractive feed stock opportunity with potential for bioconversion to a wide variety of valuable commodity products. This review highlights the need to address the complexities of the oxygen transfer rate and overall volumetric oxygen transfer coefficient (K(L)a) in hydrocarbon bioprocesses so that this potential can be realised. Three markedly different K(L)a behavioural trends have been identified in hydrocarbon-aqueous dispersions and characterised according to the hydrocarbon type and concentration, operating conditions and geometric constraints. A fundamental conceptual understanding of the mechanisms which define the exact behaviour of KLa in response to changes in turbulence and fluid properties is provided. Further, the behaviour is quantified in terms of the parameters which underpin this response viz. bubble diameter, gas-liquid interface rigidity, gas hold up, surface tension, viscosity and diffusivity. Consideration is given to existing predictive correlations for interfacial transfer area, bubble diameter, gas hold up, oxygen transfer coefficient and K(L)a. It is envisaged that through the elucidation and quantification of the parameters which shape the behaviour of K(L)a, these correlations may be successfully extended to predict the complex behavioural KLa trends in hydrocarbon-based bioprocesses. (c) 2007 Elsevier B.V. All rights reserved.