The effect of feedstock origin and temperature on the structure and reactivity of char from pyrolysis at 1300–2800 °C

Abstract

This study reports the effect of feedstock origin, residence time and heat treatment temperature on CO 2 and O 2 reactivities, nanostructure and carbon chemistry of chars prepared at 1300, 1600, 2400 and 2800 • C in a slow pyrolysis reactor. The structure of char was characterized by transmission electron microscopy and Raman spectroscopy. The CO 2 and O 2 reactivity of char was investigated by thermogravimetric analysis. Results showed that the ash composition and residence time influence the char reactivity less than the heat treatment temperature. The heat treatment temperature and copyrolysis of pinewood char with biooil decreased the CO 2 reactivity approaching that of metallurgical coke. Importantly from a technological standpoint,

Electrical Resistivity of Carbonaceous Bed Material at High Temperature

“…The current investigation showed that decreasing electrical resistivity was primarily correlated to heat treatment temperature, bulk density, and temperature profile inside the bulk, whereas prolonging the residence time did not affect electrical resistivity. At 1600 • C, the charcoal structure comprises amorphous and nanocrystalline graphite, in which prolonging residence time to 12 h led to the formation of ring graphitic structures [21]. However, the increase in crystallite growth is compensated by a decrease in excess electrons [1], which resulted in a quasi-constant electrical resistivity.…”

“…The molar H/C and O/C ratios decreased by the thermal decomposition and release of volatile oxygenates, such as organic acids, alcohols, and phenols as well as hydrogen, methane, carbon monoxide, and carbon dioxide [39,40]. Dehydrogenation reaction at high temperature can form small aromatic cluster in the carbon matrix [20,21], in which the increased number of clusters result in an enhanced aromaticity of the solid residue. Ultimate analysis verified results from proximate analysis that solid residue is composed of carbon and inorganic matter.…”

“…Previous studies have shown that charcoal properties can be improved by increasing the heat treatment temperature. For example, CO 2 reactivity of charcoal approaches that of fossil reducing agents at a heat treatment temperature higher than 1600 • C [20,21]. Thus, it is crucial to understand the properties of charcoal at high temperatures to provide a stable operation of the furnace.…”

Characterization of renewable reductants and charcoal-based pellets for the use in ferroalloy industries

“…The results showed that co-pyrolysis and distillation of charcoal with tar significantly increase the solid char yield in the entire process and thus, emphasize the potential use of biocarbon-based reductants in ferroalloy industries. It was found that the maximum reaction rate of charcoal from additional pyrolysis at 1300 and 1600 • C was shifted to temperatures about 40 • C lower than for charcoals from primary pyrolysis at 1300 • C. The TEM analysis showed that the mean separation distance of oak char graphene layers was similar to graphite, whereas spruce char contained different types of amorphous carbon structures [31]. However, in the present study the CO 2 reactivity of spruce and oak charcoal samples was similar after the additional heat treatment.…”

Structural and Thermal Characterization of Novel Organosolv Lignins from Wood and Herbaceous Sources

“…The main difference in O 2 and CO 2 reactivity of lignin samples was observed in the higher maximum temperature of PL compared to other lignin samples due to the shift of the DTG peak to the higher temperatures. The DTG curves show a double broad peak that indicates a heterogeneous lignocellulosic mixture with respect to O 2 and CO 2 reactivity [50,51].…”