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UBC Theses and Dissertations

Oxygen transfer in a stirred tank Liu, Ming-Shen


Microbiological leaching of sulfide minerals in fermenters is believed to have commercial potential. The oxygen transfer rate has been assumed to be one of the most important factors affecting the leach rate. The mass-transfer rate at various solution pH's was studied by using an unsteady gassing out process. The sulfite-oxidation process was also studied in an attempt to explain the absorption mechanism. A 7.5 inch I.D. methyl methacrylate tank with 4 baffles and a 4-inch diameter paddle type impeller were used. The impeller was driven by a motor mounted on a dynamometer which allowed measurement of the power used in agitation. All the experiments were carried out under highly turbulent conditions and covered the liquid temperature range 25°C to 40°C. The results showed that pH had no effect on mass-transfer coefficient. The values of K[subscript L]a increased as temperature increased. The relationship between K[subscript L]a, power input and superficial gas velocity was found to be of the form: K[subscript L]a = c(HP/V)[superscript x] (V[subscript s])[superscript y] A comparison of the K[subscript L]a observed in an unsteady gassing out process and that in a sulfite-oxidation process showed that the interfacial area/unit volume of liquid, a, is directly proportional to (V[subscript s])º‧⁵º which coincides with Calderbank's result.

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