Beneficiation of coal fly ashes by oxygen chemisorption

Senneca, Osvalda; Salatino, Piero; Sorrenti, R.

doi:10.1016/j.expthermflusci.2012.03.022

Cited by 4 publications

(2 citation statements)

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“…Indeed, the beneficial role of preoxidation has already been highlighted in previous studies, where it was indicated as a measure to reactivate and enhance the combustion rate of carbon with intrinsic low reactivity, such as residual carbon in ash from pulverized fuel (PF) boilers. 18,19 The proposed interpretation is in agreement with results of DFT models on epoxy configurations and stability on the hexagonal grid. Theoretical calculations in fact showed that, on small graphene patches, epoxy groups form aligned rows and, as a result of the cumulative strain exercised on the underlying C−C bonds, tend to unzip, being ultimately incorporated into the C basal plane.…”

Section: ■ Discussionsupporting

confidence: 85%

“…This finding can be explained by assuming that the rearrangement of epoxy during preoxidation goes together with activation of less reactive carbon sites, which, in the absence of peroxidation, would require overcoming higher energy barriers and, hence, higher temperatures, to decompose into CO and CO 2 . Indeed, the beneficial role of preoxidation has already been highlighted in previous studies, where it was indicated as a measure to reactivate and enhance the combustion rate of carbon with intrinsic low reactivity, such as residual carbon in ash from pulverized fuel (PF) boilers. , …”

Section: Discussionmentioning

confidence: 99%

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Mechanism and Thermochemistry of Coal Char Oxidation and Desorption of Surface Oxides

et al. 2017

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The present study investigates the coal char combustion by a combination of thermochemical and X-ray photoemission spectroscopy (XPS) analyses. Thermoanalytical methods (differential thermogravimetry, differential scanning calorimetry, and temperature-programmed desorption) are used to identify the key reactive steps that occur upon oxidation and heating of coal char (chemisorption, structural rearrangement and switchover of surface oxides, and desorption) and their energetics. XPS is used to reveal the chemical nature of the surface oxides that populate the char surface and to monitor their evolution throughout thermochemical processing. XPS spectra show the presence on the carbon surface of three main components. It is shown that the most abundant oxygen functionality in the raw char is epoxy. It decreases with preoxidation at 300 °C and even more at 500 °C, where carboxyl and ether oxygen functionalities prevail. The rearrangement of epoxy during preoxidation goes together with activation of the more stable and less reactive carbon sites. Results are in good agreement with semi-lumped kinetic models of carbon oxidation, which include (1) formation of “metastable” surface oxides, (2) complex switchover, and (3) desorption into CO and CO2.

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Section: ■ Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%