Advanced biofuels : oxidation kinetics of methyl pentanoate and life cycle assessment of triacetin
(2018)
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- Abstract
- Biofuels are a part of our current and future energy mix. Bioethanol and biodiesel are blend with our current fuels and despite the strong interest in electric cars, liquid fuels are still needed for heavy transport and aviation. A biofuel is sustainble as less Green House Gases (GHG) are emitted by it use and production compared to fossil fuels and no hazardous molecules and particles are formed by its combustion. In this thesis two advanced biofuels are investigated: methyl pentanoate (MPE) and triacetin. Both are esters and MPE can be used in gasoline engines without any adjustment. While triacetin can be coproduced with biodiesel and can act as a fuel additive in diesel engines. The combustion kinetics of MPE are investigated in this work. Investigating which molecules are formed by its combustion. Premixed laminar flat flames with different equivalence ratios were stabilized on a Botha-Spalding burner at a pressure of 55 mbar. The mole fraction profiles of stable species were measured with GC-FID/TCD and the temperature of the flame with a fine wire thermocouple. Radiation losses during the temperature measurements were corrected with both the Electrical Compensation Method (ECM) and a Heat Transfer Method (HTM) method. The corrected temperature profiles obtained with the HTM were used for simulation of the laminar flat flames. A kinetic model for the oxidation of MPE, proposed by Dayma et al., is used for the simulations. The kinetic mechanism is composed of 206 species and 1792 reactions. The OpensMOKE software is used for the simulations. Overall a good fit between experimental and simulated mole fraction profiles was found for the rich and stoichiometric MPE flames. The performance of the mechanism for other combustion configuration is also assessed and in the end some improvements for the kinetic mechanism are suggested. In the second part, a life cycle assessment for the coproduction of biodiesel and triacetin is made regarding energy and GHG emissions. The system boundaries are set around the production reaction(s) and the production and recovery of the reactant. Data about energy needs and GHG emissions of the processes are extracted from the EcoInvent database. Four scenarios are compared with each other: the biodiesel production from algal oil (BD), and three triacetin coproduction routes: the catalytic interesterification reaction of algal oil with methyl acetate (IRc), the enzymatic interesterification reaction (IRe) and the biodiesel production followed by the esterification of glycerol with acetic acid (ER). The BD scenario scores best in terms of energy and GHG emissions compared to the coproduction scenarios. The main reason is the production of the needed reactants. The production of the reactant used in the coproduction routes consumes more energy and emits more GHG than the production of methanol. Nevertheless, the energy needed for production is less than the energy content of the fuel formed. For the IRe and IR scenarios Enery Return of Investment (EROI) greater than unity is found. Also no waste glycerol is formed with the coproduction reactions and more biofuels is formed, making the coproduction of triacetin a viable process.
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Citations
Van Damme, S. (2018). Advanced biofuels : oxidation kinetics of methyl pentanoate and life cycle assessment of triacetin. https://hdl.handle.net/2078.5/52941