Structural features and gasification reactivity of coal chars formed in Ar and CO 2 atmospheres at elevated pressures

Exploring the potential of petrographics in understanding coal pyrolysis

“…The allocation of the inertinite group maceral into reactive and inert sub-categories has been shown to have reasonable impact on coal conversion processes. Malumbazo et al [13] demonstrated that the higher content of inertinite resulted in low reactivity of coal. Based on the report of Malumbazo et al [13], and from the data in Table 2, it is expected that the lignite coal with the least inert inertinite content would be the most reactive and the anthracite coal with the highest inert inertinite content and least volatile matter content would be the least reactive.…”

“…1e6). Malumbazo et al [13] has reported that the effect of heat becomes visible petrographically in the drying zone of a gasifier in the temperature region of about 200 C, in agreement to an earlier work by Bunt et al [3]. The vitrinite component (in addition to the few percentage of liptinite present in the coal) is likely to exhibit de-volatilizing behavior at lower temperature than the inertinite when exposed to increasing temperatures due to volatiles components being driven off, which leads to the changes in colour viewed optically [6].…”

“…Therefore, the assessment or prediction of coal performance during pyrolysis (particularly combustion behaviour) should not be based on coal rank and particle size alone, but rather, great consideration should be given to the maceral composition of the coal since it determines the char morphology [11] and reactivity [12]. Coal technical performance also depend on amount, size and distribution of minerals [13], the degree of liberation of pyrites in coal's grinding studies [14], the quality of the feed coals and residues in the conversion process [15], and vital energy resources as in coal discards [16]. However, Murchison [17] differs from this view when he concluded from the investigation on petrographic aspects of coal structure: reactivity of macerals in laboratory and natural environments, that, coal reactivity is type and rank-dependent, with the maceral groups showing markedly different responses to the same set of operating conditions during coal utilization.…”

Spectroscopic Elucidation of the Links between Char Morphology and Chemical Structure of Coals of Different Ranks

“…Evidence from other works reported this demonstration of the transition from amorphous aliphatic fraction to a more condensed aromatic fraction to be attributed to the loss of components having higher proportions of oxygen, hydrogen and disorganized carbon as the transition progress from low to high temperatures [4] [29]. Moreover, the structural significance of this relationship cannot be over-emphasized in the interpretation of the reactivity of coal char, even when the fundamental physical parameters does not change in a straightforward way as graphitization proceeds (increase in aromaticity).…”

“…The role played by char in coal utilization processes has created a need for high quality; hence it is important to determine its chemical properties to ensure smooth operation [2] and high productivity of such processes as in fixed bed gasification [3]. The physical properties of coal which impact on coal conversion processes relate to those processes which results in charge of particle size [4] and surface morphology (density, pore size, pore size distribution) [5]. The chemical properties of coal which impact on the conversion processes are those which effect a change in the chemical constitution and these in turn may lead to changes in the physical properties such as the surface area [6].…”