Surfactant adsorptivity of solid products from pulverized-coal combustion under controlled conditions

Strategies and Technology for Managing High-Carbon Ash

“…The results in this report help explain the origin of apparently contradictory reports of the effects of surface oxidation in the literature on fly ash carbon [8,9,12]. It is believed that the enhanced uptake of polar compounds from the vapor phase (acetone) [9] is driven by the increased surface energy and polarity of oxidized carbon surfaces, while the decreased uptake of surfactant from solution is related not to the magnitudes of the energies but to the increased polar/dispersive ratio.…”

“…Here the carbon is a contaminant and its undesirable adsorption of surfactant from the aqueous concrete paste reduces the surfactant's ability to stabilize sub-millimeter air bubbles that help improve freeze-thaw resistance in set concrete [10]. Previous studies [5,7,11,12] have related the extent of adsorption to four factors: (1) the amount of residual carbon in ash, (2) the total carbon surface area, (3) the accessibility of the surface as governed by pore and particle size distribution, and (4) the state of carbon surface oxidation. Oxidation of carbon surfaces by either air or ozone has been shown to reduce the extent of concrete surfactant adsorption [7].…”

Study of Activation of Coal Char

“…Results for chars produced under extremely high heating rates are seen in Figure 4. We had already reported that the differences in char morphology could be observed under laboratory burner conditions [14], but how important this factor was as an actual design parameter for production of activated carbons remained unclear. It may, however, quickly be seen from Figure 4 that the earlier noted differences in char morphology imprinted during pyrolysis can persist until the very final stages of burnout of the chars (all of the samples in Figure 4 have an equivalent char conversion of well over 99%).…”

Study of Activation of Coal Char

“…8 coal chars already discussed above, the plot also features data obtained from combustion of a Pittsburgh No. 8 coal sample in a laboratory flat flame burner [38].…”