碩士 / 淡江大學 / 化學工程與材料工程學系碩士班 / 100 / Dynamic microfiltration with a rotating-disk is used for the separation of microalgae from harvest suspension in this study. The effects of operating conditions, such as disk rotating speed, suspension feed rate, transmembrane pressure on the filtration rate, membrane fouling, cake properties and microalgae rejection, are discussed both experimentally and theoretically. Since the shear stress acting on the membrane surface may be increased by increasing the disk rotating speed, the filter cake is reduced and the filtration rate is increased by using rotating-disk dynamic microfiltration.
A 99.9% microalgae rejection can be achieved in the microfiltration using a 0.1μm mixed cellulose ester membrane. The main source of filtration resistances is the highly compressed filter cake with a compressibility factor of 0.66. The cake mass and thickness decrease with increasing the feed velocity and disk rotating speed. Therefore, increasing the shear stress on the membrane surface by increasing the disk rotating speed or decreasing the transmembrane pressure leads to a higher pseudo-steady filtration rate. In addition, the mean particle size of microalgae on the membrane surface may decrease by increasing the shear force. Measuring the functional groups of the materials in the filter cake using Fourier transform infrared spectroscopy indicates that the original functional groups in microalgae become unobvious under higher shear stresses. This is attributed to the leaving of extracellular polymeric substances from the algae surfaces.
In this study, the flow fields in the rotating-disk dynamic microfilter are simulated by a computational fluid dynamics software, FLUENT. The shear forces on the membrane surface are calculated to understand the effects of operating conditions on the cake formation and filtration rate. According to the theoretical model analysis, the relationships between pseudo-steady filtration rate and operating conditions are established. Substituting the regressed empirical constants and operating conditions into theoretical calculation, the relative deviation of filtration rates between estimated results and experimental data is less than 15%. It can be expected that the relationship between the local shear stress and pseudo-steady filtration rate can be extended to apply in module scale-up.
| Identifer | oai:union.ndltd.org:TW/100TKU05063016 |
| Date | January 2012 |
| Creators | Syuan-Jyun Lin, 林炫君 |
| Contributors | Kuo-Jen Hwang, 黃國楨 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 115 |
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