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Experimental and Theoretical Study of Biomass Conversion to Green Fuel by Using Supercritical Fluid

Mohamadzadeh Shirazi, Hamed | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48995 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, Cyrus; Karimi Sabet, Javad
  7. Abstract:
  8. Nowadays, one of the most basic human problem is how to manage energy resources for sustainable development and how to deal with problems caused by growing energy consumption. Various scenarios are being discussd that the most important of them can be considered research on finding alternative energy sources that are renewable and do not have common pollution. Thus, according to researches carried out until now, using sources such as wind, water, solar biomass, etc. have been proposed. However, due to problems in the development of each of these sources, biomass as the primary option has been introduced. because biomass has several subsidiaries, research shows microalgaes (as a subset) are the most important alternative sources because they do not interfere with other sectors, which food is the most important one, and have high potential for oil production. Overall production of biodiesel from microalgae consists of five main stages of cultivation, biomass separation, drying, extraction and production of fuel. Here, drying and oil extraction steps are the most original and most key stages affecting the project’s economy. In this study, the focus is on integration of oil extraction and transesterification reaction. Also, the effect of moisture on the efficiency of the biodiesel production is considered. The process of transesterification reactions in supercritical methanol conditions with different microalgal feed containing different percentage of lipid as a cost-effective method for the production of biofuels is proposed[84, 95, 97, 121]. This study is conducted in order to achieve the best operating conditions, economically and efficiently, for the production of biological and renewable diesel in sub/supercritical condition with dry or wet Spirulina Platensis microalgae as feed . Extraction of lipids from microalgae cell wall and then reaction with methanol in the range of critical conditions are two processes in the series that are involved in the production of biodiesel fuel. Effect of important parameters in the process of converting triglycerides in Spirulina algae to fatty acid alkyl esters in different situations involving temperature (〖200-300〗^0C), time (10-50 minutes), ratio of alcohol to dry microalgae (4:1-12:1 ml/g), ratio of hexane to dry microalgae (0-8:1 ml/g) and moisture content (0-80%) in a batch reactor in order to achieve the most suitable condition in terms of efficiency was evaluated and compared with reference Bligh&Dyer method. For this purpose, the central composited design and response surface experiments was used by employing Design Expert software. 32 tests were carried out according to the experiment design and different efficiencies in the range of 44/0% to 32/99% using gas chromotography-mass spectrometry analysis (GC-MS) were obtained . Quadratic model as well as three-dimentional graphs extracted from the test results show the positive effect of temperature, time and ratio of methanol to dry microalgae and negative influences of the presence of hexane and moisture. In addition, the Minitab software was used to analyze the sensitivity of each parameter and the result showed that the efficiency of biodiesel production is more affected by temperature and time than other parameters. To observe the structure of microalgae cells before and after the direct sub/supercritical process, scanning electron microscopy (SEM) was used and the photographed images represent the destruction of cell walls of microalgae after the direct supercritical process. The results indicate the potential of microalgae for use in direct transesterification reaction in sub/supercritical methanol with Spirulina microalgae for the production of biological and renewable diesel. Finally, the direct production of biodiesel from microalgae by the kinetic theory of first order reaction was modeled and valuesof 0.003404, 0.000678and 0.000393 were obtained for each of temperatures of 250, 275 and 300 ° C, respectively. The activation energy and frequency factor were calculated equal to 1.089134e5 (J / mol) and 3.9204e-14 (1 / s), respectively
  9. Keywords:
  10. Biodiesel ; Microalgae ; Transesterification Reaction ; Biomass ; Supercritical Fluid ; Lipid Extraction ; Supercritical Methanol

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