Thermally induced changes in microstructure and reactivity of biogenic and fossil fuel particles

Review of Carbonaceous Annealing Effects on O2 and CO2 Coal Reactivity

“…Recent work showed that lignocellulosic biomass undergoes thermal annealing upon heat treatment, with the development of graphitic order and the loss of reactivity. 68 Some researchers suggest that kinetic models of thermal annealing developed for coals can be applied to biomass, but some others showed that the picture of the lignocellulosic biomass matrix is more complex than that for coals because of the coexistence of multiple components (cellulose, hemicellulose, lignin, etc.) with different propensities to undergo pyrolysis, thermal annealing, and combustion.…”

High-temperature rheological behavior and non-isothermal pyrolysis mechanism of macerals separated from different coals

“…By offline or online observation of morphology and structure of coal-based materials, previous studies have observed that their carbon ordering [31], expansion [32], and permeability during coking are mutable [33], with different degrees of variability for various coal types. It was further revealed by thermogravimetric analysis that the thermal stability of metaplast generated from different coals differed substantially [34], which combined with mass spectrometry uncovered that the aliphatic content endowed in the coal appeared to show a positive correlation with the persistence of the metaplast presence [35][36].…”

Extension of the Thermal Annealing Concepts Developed for Coal Combustion to Conversion of Lignocellulosic Biomass

“…Here, very high temperatures (>1500 K) are reached in a very short residence time (in the order of 0.1 s). The high heat flux at the particle surface (>100 W m –2 ) generated swollen spherical char particles with large cavities or the opposite, irregularly shaped, shrunk, and even fragmented particles. , Morphological and dimensional aspects are known to play an important role in determining the flow pattern and mass and heat transfer, but severe changes also occur in the chemical and fine structure, which can significantly affect the char reactivity. − …”

“…Thermal annealing of lignocellulosic biomass has mainly been addressed by material scientists within the context of the production of bio-based nano-structured and graphenic materials thus far. The topic has received comparatively little attention in the context of combustion science. ,,,− Recently, Septien et al and Senneca et al showed that the reactivity of biomass chars decreases sensibly after high-temperature post-pyrolysis treatments in parallel with the development of graphitic order [observed via high-resolution transmission electron microscopy (HRTEM) or Raman microscopy]. However, the paucity of data on the relations between thermal treatment and reactivity of biomass chars to date does not allow us to say if the concepts and the modeling approaches developed within the combustion community for thermal annealing of coal can be extended to biomasses.…”

“…However, the paucity of data on the relations between thermal treatment and reactivity of biomass chars to date does not allow us to say if the concepts and the modeling approaches developed within the combustion community for thermal annealing of coal can be extended to biomasses. Recently, Kreitzberg et al highlighted the similarity of thermal annealing of a biomass and a lignite and successfully applied available kinetic models of thermal annealing , to both fuels, for heat treatments carried out between 1023 and 1173 K in a fast heating rate fluidized bed.…”