| Summary: | 碩士 === 淡江大學 === 化學工程與材料工程學系 === 92 === The mechanism of centrifugal filtration of pure microbe and microbe/protein binary suspensions was investigated in this study. The suspensions of yeast and BSA are prepared and used for filtration in experiments. The effects of operating conditions on the performance of filtration, such as concentration and rotating speed, were discussed in this study. The characteristics of the filter cake, such as resistance and porosity, were measured under various conditions. Comparisons of filtration rate and protein rejection between pure microbe and binary suspension were carried out, and marked differences were observed in this study.
For the 5% pure yeast suspension, 2000 rpm is the optimum rotating speed, while the filtration performances under 4000 and 500 rpm were almost the same. This is because an increase in the rotating speed of centrifuge caused not only to higher filtration rate but to more compact cake as well. Therefore, the contrary effects of rotating speed on the driving force (P) and filtration resistance should be serious discussed. For the 2.5% pure yeast suspension, the permeate velocity under 4000 rpm was larger than those under the other rotating speeds. During a batchwise operation, the filtration resistance of cake increased with time due to the cake compression. Furthermore, the existence of protein resulted in lower filtration resistance and higher porosity of cake. As a result, the filtration rate of binary suspension was higher than that of pure yeast. The percentage of BSA retained was 10~20% for 5% and 2.5% binary suspension. The instant retention decreased with time due to the decrease of filtrate velocity. The cake of yeast was more compact so that the BSA passed through the cake toughly.
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