Pyrolysis Kinetics Using TGA and Simulation of Gasification of the Microalga Botryococcus braunii
2019
Arbeláez, Andrés A. | Giraldo, Néstor D. | Pérez, Juan F. | Atehortua, Lucia
Microalgal biomass has been widely investigated as a source of renewable energy, but currently, some alternatives are not economically competitive. Thermochemical conversion of biomass is an alternative way to transform their organic compounds into liquid and gaseous fuels. The aim of this work is twofold; first, the pyrolytic process of the microalga Botryococcus braunii (BB) by thermogravimetric analysis, as well as the relevant reaction kinetic constants and related activation energies, is assessed. Secondly, a sensitivity analysis of the biomass gasification process with air using a thermochemical model was conducted to predict the composition of a syngas as a function of the biomass moisture content and the biomass/air ratio. The results showed that BB biomass is composed mainly of carbon (62.4 wt.%) with volatile solids of 84 wt.%, while the fixed carbon represents around 7 wt.%. Additionally, observed values for heating (27.86 MJ kg⁻¹) and activation energy (~ 110 kJ mol⁻¹) were different from other algal feedstocks due to the capacity of accumulation of liquid hydrocarbons of this. On the other side, the gasification process showed it was found that the moisture content in the biomass and biomass/air ratio variables are key parameters for reaction temperature and producer gas composition. Accordingly, with a suitable combination of these variables, it is possible to obtain a syngas composed of gaseous species with high energy content (CO, 18 vol.%; H₂, 17 vol.%; and CH₄, 2 vol.%.), which can be transformed through processes such as Fisher-Tropsch process into liquid biofuels such as kerosene or gasoline.
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