使用旋轉盤微過濾分離微藻懸浮液

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Title:	使用旋轉盤微過濾分離微藻懸浮液
Other Titles:	Separation of microalgae suspension using rotating-disk dynamic microfilter
Authors:	林炫君;Lin, Syuan-Jyun
Contributors:	淡江大學化學工程與材料工程學系碩士班黃國楨;Hwang, Kuo-Jen
Keywords:	旋轉盤微過濾;微藻;薄膜分離;生質柴油;rotating-disk dynamic microfilter;microalgae;Membrane Filtration;biodiesel
Date:	2012
Issue Date:	2013-04-13 11:52:26 (UTC+8)
Abstract:	本研究以旋轉盤薄膜微過濾進行微藻懸浮液之分離，提升微藻之採收與分離效率。利用旋轉盤造成之高剪切力降低濾餅之生成與過濾分離。以實驗與理論分析並行，探討旋轉盤轉速、進料速度與透膜壓差對過濾濾速、結垢阻力、濾餅性質與微藻粒徑大小之影響。由實驗結果發現，對微藻粒子之阻擋率可達99.9 %，主要阻力來源為微藻形成之濾餅，而此濾餅具高壓縮性，壓縮係數為0.66。而增加進料速度與旋轉盤轉速，皆可提升膜面剪切力，掃除膜面濾餅與降低濾餅層厚度；故以低透膜壓差與高膜面剪切力之操作條件，即可得到最高的擬穩態濾速。隨著剪切力的上升，膜面殘留粒子之粒徑減小；以傅立葉紅外光譜儀測量濾餅之官能基，發現操作於高剪切力之下的微藻官能基變得較不明顯，證明微藻的胞外聚合物質會脫離粒子表面。本研究亦利用計算流體力學軟體模擬旋轉盤過濾系統的流場，分析膜面之剪切力，以分析操作條件對濾速之影響。並藉由理論模式之運算，迴歸擬穩態濾速與操作條件之關係式，套入實驗常數與操作條件加以計算，所估算的濾速其相對誤差皆在15 %以內；並找出局部剪切力與擬穩態濾速之間的關係，可用於推估模組放大之穩定濾速。 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.
Appears in Collections:	[Graduate Institute & Department of Chemical and Materials Engineering] Thesis

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