Combustion of microalgae Nannochloropsis oculata biomass: Cellular macromolecular and mineralogical content changes during thermal decomposition

摘要

The cellular macromolecular and mineralogical content changes during the combustion of Nannochloropsis oculatabiomass have been investigated. A Fourier transform infrared spectroscopy (FTIR) analyzer was used to investigate the cellularmacromolecular content changes of biomass at every stage of decomposition during heating to 1200 ?C. From ambient temperaturesto 190 ?C, similar spectra were obtained, indicating relatively little change in the chemical structure of the biomassmaterial. Changes in the spectra are very noticeable from 190 to 1200 ?C. The combustion process begins with thermal crackingof the ?OH groups of silanol that escape together with moisture at temperatures up to 190 ?C. Subsequent temperature increasedecreased intensity of the spectrum, indicating thermal degradation of the organic compounds derived from lipids, proteins, andcarbohydrates. These processes occur up to 800 ?C. The X-ray diffraction (XRD) results showed that the mineral constituents ofbiomass degraded during the combustion process, and a portion reacted to form new compounds such as melilite (Ca6Na2O15Si4).The SEM images show a morphological distinction between biomass and its residue at 1200 ?C, due to the decomposition andrearrangement of the mineral content during heating. Fragmentation of the samples also occurred during heating, characterizedby more uniform residue at 1200 ?C.