Optimum design on membrane filtration system for separation of bioethanol fermentation broth

• Main Authors: Chien-Yu Ku, 辜建諭
• Other Authors: Kuo-Jen Hwang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/46386404459366208719

碩士 === 淡江大學 === 化學工程與材料工程學系碩士班 === 100 === 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.