Browsing by Author "Kadzinga, Fadzai"

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    Venturi aeration of bioreactors
    (2015) Kadzinga, Fadzai; Harrison, STL
    Low solubility of oxygen has resulted in high bioreactor energy requirements in order to supply sufficient oxygen to aerobic bioprocesses. It is desirable to reduce energy consumption in bioreactors to benefit environmental sustainability as well as economic feasibility. This is particularly important with the resurgence of interest in bio-based commodity products. Some research has suggested that venturi aeration of bioreactors will reduce energy consumption by eliminating the need for air compression, while at the same time maintaining or improving oxygen transfer rates. On the other hand, there are findings that suggest venturi aeration has lower energy efficiency than conventional sparging and oxygen transfer rates achieved are too low sustain aerobic biological processes. A comparison of the aeration of geometrically-similar reactors using the same analytical methods to determine kLa is not available in the literature. This comparison should also address analysis of energy input including energy used for compressing gas sparged into a stirred tank reactor; the investigation of mass transfer rates at higher flow rates (vvm) in venturi-aerated reactors and resulting cell response to these higher flow rates. This is the topic of the dissertation presented. In this laboratory scale study, venturi aerators were characterised and energy consumption as a function of oxygen mass transfer rates compared with a geometrically identical aerated stirred tank reactor by evaluating the volumetric mass transfer coefficients (kLa). The kLa was investigated in varying reactor setups using the dynamic gassing-in method.