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    Title: 以膜過濾系統分離生質酒精發酵槽產品之最佳化設計
    Other Titles: Optimum design on membrane filtration system for separation of bioethanol fermentation broth
    Authors: 辜建諭;Ku, Chien-Yu
    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: 掃流過濾;生質酒精;分離效率;Cross-flow filtration;bioethanol;Separation efficiency
    Date: 2012
    Issue Date: 2013-04-13 11:52:07 (UTC+8)
    Abstract: 本研究以酵母菌、葡萄糖、酒精配置成三成份之懸浮液來模擬生質酒精發酵槽產品,利用掃流過濾系統分別回收酒精發酵槽之產物,將分離程序分成兩階段,第一階段利用微過濾薄膜(MCE 0.45微米)將酵母菌細胞濃縮,降低酒精濃度以減少抑制酵母菌活性,第二階段利用超過濾膜(RC 5kDa)濃縮葡萄糖基質,以回收再利用,並探討操作條件對濾液通量、過濾阻力、濾餅性質及分離效率之影響。
    MCE微過濾主要的阻力是酵母菌在濾膜表面堆積形成的濾餅阻力,增加過濾壓差會增加濾餅量並壓縮濾餅,因此增加過濾壓差無法提升濾液通量。增加掃流速度能降低濾餅量,使濾餅阻力大幅降低,因此能有效的提升濾液通量。RC超過濾主要影響濾速衰退的阻力有葡萄糖在膜面堆積形成濾餅、各溶質於膜孔道內部阻塞及濃度極化層造成的阻力,增加過濾壓差及掃流速度皆會使各阻力增加,特別是增加掃流速度會造成阻力大幅提升、使濾液通量減少。此外,增加過濾壓差及掃流速度皆會使MF及UF的各溶質阻擋率提升,但掃流速度對各溶質阻擋率的影響較大,在壓差100 kPa下,MF與UF之掃流速度若從0.1提升至0.5m/s,其葡萄糖阻擋率分別從4.7%與24%提升至7.6%與40.9%。
    本研究對MF與UF進行理論分析,推導操作條件與濾液通量及溶質阻擋率之關係,利用實驗數據回歸各參數後,將參數代入各方程式進行計算,所得之理論值符合實驗之趨勢。本研究並嘗試最佳操作的分析,若控制操作條件在掃流速度0.5 m/s及壓差在100 kPa下,MF會有最大的濾液通量,UF會有最高的葡萄糖阻擋率,而UF的濾液端酒精收集通量可達60 kg/m2day。
    The use of a two-step cross-flow filtration system for the purification of ethanol from bioethanol fermentation tank is studied. The suspensions used in experiments are prepared using yeast cells, glucose and ethanol. In the first step, yeast cells are retained by the filter membrane during a microfiltration (MF), while most ethanol and glucose permeate through the filter cake and membrane into the filtrate. In the second step, ethanol and glucose are separated using a cross-flow ultrafiltration (UF). The yeast cake properties, the rejection coefficients of glucose and ethanol and the filtration flux under various operating conditions, such as cross-flow velocity and filtration pressure, are measured and analyzed theoretically.
    The filter cake plays the major role in determining the filtration resistance in MF. An increase in filtration pressure leads to cakes with more mass and compressible. The cake thickness and filtration resistance decreases with increasing cross-flow velocity, as a result, the filtration flux may be effectively enhanced by increasing cross-flow velocity. The glucose may deposit on the membrane surface, foul in the membrane pores and form a concentration polarization layer near the membrane surface to result in filtration resistance and decline the filtration flux during UF. An increase in cross-flow velocity or filtration pressure causes higher filtration resistance, especially the effect of cross-flow velocity. The glucose rejection increases with increasing cross-flow velocity or filtration both in MF and UF. When cross-flow velocity increases from 0.1 m/s to 0.5 m/s under a fixed pressure of 100 kPa, the glucose rejection increases from 4.7% to 7.6% in MF and from 24% to 40.9% in UF, respectively.
    Theoretical models based on the resistance-in-series model, the force balance model for particle deposition, the concentration polarization model and the standard capture equation for depth filtration are derived for predicting the filtration flux and the observed glucose rejection directly from operating conditions. The agreements between calculated results and experimental data demonstrate the reliability of the proposed models. A numerical program is established to simulate the filtration fluxes and solute rejections in MF and UF. The optimum conditions are solved as a cross-flow velocity of 0.5 m/s and a filtration pressure of 100 kPa.
    Appears in Collections:[化學工程與材料工程學系暨研究所] 學位論文

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