Search

Elephant grass (Pennisetum purpureum Schum.) is one such resource with a great amount of carbohydrate and lignin polymers that together represent high volatile content of biomass suitable for conversion into bio-oil by fast pyrolysis. However, the high ash content inhibits the realization of its full potential as a pyrolysis feedstock as the ash reduces product yields and changes chemical pathway toward undesired product selectivity including oxygenated compounds that are known to result in bio-oil instability. In this study, elephant grass was pretreated prior to pyrolysis using liquid hot water (LHW) and acid solution washing (AW) to explore whether reduction in ash content could improve its physical properties, energy density and pyrolysis products selectivity. Upon characterization of compositional analyses, chemical ash composition by X-ray fluorescence, Fourier-Transform Infrared Spectroscopy and cellulose crystallinity Index (CrI) before and after demineralization treatments we found that washing pretreatment processes were efficient in ash removal increasing HHV and the volatile content, and decreasing fixed carbon and moisture. The use of the pretreated biomass as feedstock for pyrolysis performed at 600 °C in a micro-pyrolyzer 5200 HP-R Py-GC/MS reveals interesting product distribution. While many oxygenated compounds were identified as pyrolysis products for both raw and pretreated elephant grass significant changes were observed in the products of the pretreated biomass, such as an increased yield of levoglucosan (LG) for LHW washed biomass, which presented the lowest CrI, an evidence that cellulose content and its structure influences the pyrolysis product distribution. [ABSTRACT FROM AUTHOR]

Microalgae have a great potential to produce biofuels, but the cost is still too high mainly due to the biomass production. Mixotrophic cultivation has been pointed as microalgae cultivation mode for biomass/bioenergy production with lower cost. The proposals of this work were to cultivate S. platensis in autotrophic and mixotrophic medium using molasses as source of organic carbon and investigate the thermal behavior of obtained biomass by means of thermogravimetric analysis and pyrolysis (Py-GC/MS). The kinetics models proposed by Flynn and Wall and model-free kinetic were used to determine the activation energy. These data are important to projection of design, operation and modeling of thermochemical conversion system for microalgae. The use of molasses as supplement in culture medium for the growth of S. platensis was a good way to increase the biomass productivity and decrease the protein content. The Flynn–Wall and model-free kinetic methods were adequate to calculate activation energy on the conversion range of 0.20 to 0.80. The activation energies were 168–229 kJ mol−1 (Flynn and Wall), 177–238 kJ mol−1 (model-free kinetic) for mixotrophic biomass and 174–220 kJ mol−1 (Flynn and Wall), 181–229 kJ mol−1 (model-free kinetic) for autotrophic biomass. The compositions of volatile compounds produced by S. platensis biomass pyrolysis were different due to cultivation method that influenced the composition of biomass. Hydrocarbons, oxygenated and nitrogenated compounds were produced with different quantities. The volatile compounds content of phenols, oxygenated and nitrogenated increased and non-aromatic and aromatic hydrocarbons content decreased for pyrolysis of mixotrophic biomass. However, the mixotrophic cultivation has a great influence on the microalgae biomass production and should be a factor considered in thermal degradation project for microalgae. [ABSTRACT FROM AUTHOR]

Mn-based solid oxygen carriers supported on MgAl2O4 were prepared by the microwave-assisted combustion method followed by wet impregnation of the active phase. The oxygen carriers were characterized by X-ray diffraction, temperature-programmed reduction and scanning electron microscopy with energy-dispersive spectroscopy of the surface. The study aimed to evaluate the influence of the thermal treatment on the structure and reactivity of the oxygen carriers. Reactivity tests using coal as fuel were carried out in a thermobalance at temperatures of 750–850 °C to evaluate the behavior of the carriers. The results revealed that oxygen carriers, which were subjected to only a heat treatment after the impregnation step (MnC1), showed more reactive surfaces presenting a greater number of non-reactive and irreversible phase and thus displaying lower oxygen transport capacity as well as poorer reactivity. The carriers prepared by heat treating the support after the combustion reaction and again after the impregnation step (MnC2), showed higher oxygen transport capacity and greater reactivity with coal at 850 °C. The better reactivity is associated with the formation of Mg6MnO8 and Mn2O3 phases. [ABSTRACT FROM AUTHOR]

The use of agricultural wastes for energy conversion has been widely studied as renewable and carbon neutral energy sources. This paper aims to evaluate the energetic potential of six agricultural wastes—sugarcane bagasse, bean pods, corn stover, pineapple crown leaves, white cotton and natural coloured cotton stalks, through their characterization and pyrolysis kinetic study. The energetic potential of biomasses was evaluated by ultimate and proximate analysis, higher heating value (HHV), apparent density, and kinetic parameters of conversion and apparent activation energy (Ea) determined by Model-Free kinetics though thermogravimetric analysis data. The results indicate energetic density for dry basis biomasses, such as moisture content less than 7%, volatiles higher than 77% and moderate ash content. The HHVs were higher for the biomass with low O:C ratio. The Ea values increased with increasing O:C ratio and were also influenced by the biomass ash content. Among the studied biomasses, PCL are less explored for energy application, although the results confirm its potential for application in thermochemical processes such as pyrolysis or combustion. [ABSTRACT FROM AUTHOR]