碩士 / 國立中興大學 / 生物產業機電工程學系所 / 98 / The purpose of this study was aimed at creating a microwave assisted extraction system of microalgal lipid, to shorten the extraction time and improve the extraction efficiency. Moreover, through the automatic control reduced the extraction progress, the efficiency of extraction would be raised. This research using dried chorella sp. powder purchased from market was comprised of Soxhlet extraction experiment, comparison of the extraction methods using water bath treatment and microwave treatment, traces analysis of lipid and center point design experiment. The Soxhlet extraction experiment used AOAC 920.39C standard lipid extraction method to extract lipid of microalgal. The result using liquid-solid ratio at 150 times of organic solvent and dried microalgal powder weights had shown that the saturation of average lipid contents was about 1.53% of dry weight. The fatty acid analysis had also shown that microalgal used in this research were suitable to make the biodiesel oil. Water bath and microwave treatment testing with liquid-solid ratio at 6 times obtained that the best time for the microwave extracting time was 7 minutes, while the temperature at 72.6℃, and the bottle still under the durable pressure. Moreover, the first extracting treatment reached 20.71% lipid extraction rate. But after extractions twice, the lipid extraction rate reached saturation at about 45.24%. However, water bath treatment obtained lower lipid content about only 10% at extracting time between 3 and 7 min. The trace analysis was based on Bligh and Dyer Method to compare with the lipid content of microwave treatment, ultrasound treatment and control set treatment. The result had acquired that microalgal lipid reached a saturation level of at 11.6% of dry weight. The microwave treatment needed 75 sec, but 1200 sec by ultrasound treatment; it was 16 times of the microwave treatment. The observation using the scanning electron microscope (SEM) demonstrated that the fold of microalgal cell shrunk unevenly through the microwave treatment. It was due to the rapid temperature rise and pressure increase by microwave treatment and resulted in the sudden expansion and burst of the cell thus increasing the lipid extraction ability. The fatty acid composition analysis acquired from the three groups were not significantly different; this also indicated that the microwave assisted extraction broke the cell more effectively, and increased lipid content, but would not decompose the composition of fatty acid. The experiment proved that the microwave assisted extraction method was suitable for use in the micro-algae oil extraction.
According to the result of the previous experiments, a microwave assisted extraction system of microalgal lipid was built. The optimal factor design center point design experiment was performed by using response surface methodology (RSM). The experimental results obtained that using extraction time 7 min and liquid-solid ratio 7 times, the best extraction rate at 44.59% could be held. However, the pressure rose in extractor due to the solvent heating from the microwave; the maximum temperature and pressure achieved were 14.37℃ and 0.38 kg/cm2 , respectively. The over temperature and pressure would make the system unstable, which was critical to ensuring safe operations. Further, the experiments with and without pressure increase had acquired that the extraction rate of extraction time 5, 6 and 7min under pressure increase experimental group were 29.22、40.71 and 44.59%,and with normal pressure less experimental group were 29.37、40.78 and 44.89%, respectively. After the statistical analysis, there were no significant differences between these two groups.
The experiment was set 7 min, liquid-solid ratio at 7 times and without pressure increase as the front experimental group to perform the path of steepest ascent experiment. The experimental results obtained that an extraction rate inflection point was 58.67% at extraction time 10min and liquid-solid ratio at 8.2 times. Based on the parameters of the previous experimental results, the center point design experiment was performed. The experiment found that the best extraction rate was 65.78% at extraction time 10 min 45sec and liquid-solid ratio at 8.3 times. Using these best results as the conditions of multi-stage extraction, the experiment obtained 94.96% of extraction rate at third extraction. It had the same total lipid content with Soxhlet extraction 12hr. The extraction speed was 22 times of Soxhlet extraction. The results had shown that optimal microwave assisted extraction parameters could extract microalgal lipid efficiently.
The final experiment was performed by combing the above experimental results to build an automatic microwave assisted extraction system. It had the central control unit to control the optimal parameters and held the function of sequential operation continuously such as input, extraction , and output to simplify the complicated extraction procedures and to improve the efficiency of lipid extraction to achieve the desired mass microalgal biodiesel production.
| Identifer | oai:union.ndltd.org:TW/098NCHU5415021 |
| Date | January 2010 |
| Creators | Yi-Ming Cheng, 鄭一鳴 |
| Contributors | 尤瓊琦 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 68 |
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