Petrographic controls on combustion behavior of inertinite rich coal and char and fly ash formation

Exploring the potential of petrographics in understanding coal pyrolysis

“…The low rank coals have reflectance values of 4.36% and 4.64% respectively for the lignite and subbituminous coals. Everson et al [3] and Varma et al [45] has observed in their investigations that the vitrinite reflectance and the total reflectance comes to almost the same values at higher temperatures of 700 C and above, implying that the total reflectance value could be used in evaluating and quantifying coals. This finding is in agreement with the work of Geurrero et al [44] that reported that the differences in the contribution to reflectance from both the vitrinite and inertinite macerals of coal becomes narrow at high temperatures (>600 C).…”

Unburned carbon from coal combustion ash: An overview

“…Furthermore, in contrast to coal, aliphatic C-H stretching bands at 2920 and 2854 cm − 1 are in UC of minor significance (it was estimated that it was about 55% reduction in comparison to original coal sample) [99]. A somewhat unusual aliphatic-ester band was identified by Varma et al [186].…”

“…The carbonyl absorption band was observed in [186]; Demir et al [92] even reported its increase related to the parent coal (probably due to C-H oxidation). However, the FTIR results reported by Maroto-Valer et al [155] did not lead to reliable identification of C_O band, concluding that O may be bound more likely in heterocyclic or ether linkages.…”

“…Varma et al [186] have observed a unique char type that was spherical in shape and showed incipient development of the vesicles. This char type has been referred to as "vitrosphere" and has related to intermediate stage of char formation.…”

“…FTIR spectroscopy is typically used for the study of surface functional groups -for their occurrence as well as changes in composition during incomplete combustion (and UC creation) [92,186,155,206]. Broad absorption bands typically present in most coals at 3200-3400 cm −1 (and assigned to hydroxyl groups) decreases during the combustion, and in UC it is nearly absent, indicating that alcoholic and phenolic groups were not so abundant there as in the parent coal [99].…”