Role of an additive in retarding coal oxidation at moderate temperatures

Analysis on the Governing Reactions in Coal Oxidation at Temperatures up to 400°C

“…The major absorption peaks and their corresponding species (organic functional groups) were identified and labeled. The observed species usually contain O-H, C-H, C=C, C-O, and C=O bonds [15] [16]. Changes in the functional groups on the sample surfaces were further examined by subtracting FTIR spectra collected at various temperatures (Figure 4).…”

“…Changes in the functional groups on the sample surfaces were further examined by subtracting FTIR spectra collected at various temperatures (Figure 4). The curve a in Figure 4, which is the subtracted FTIR spectra for a sample at room temperature from those obtained after heating to 275˚C in nitrogen, indicates that a coal sample mainly experiences the water removal and hydroxyl decomposition in an inert atmosphere [14] [16].…”

“…T c2 is the peak temperature at the mass increase stage, whereas T c3 is the second transition temperature of the exothermic peak in the DTA curve (Figure 5(a) & Figure 5(b)). The percentage of mass increase at ~275˚C is determined by subtracting the minimum sample mass at ~150˚C from the maximum mass between 150˚C and 300˚C, and divided by the minimum sample mass at ~150˚C [16]. The amount of heat evolved in association with the sample mass increase is obtained by integrating the exothermic peak area of the DTA curve between T c1 and T c3 (Figure 5(b)).…”

Synchronous thermal analyses and kinetic studies on a caged-wrapping and sustained-release type of composite inhibitor retarding the spontaneous combustion of low-rank coal

“…For instance, suction salts such as CaCl 2 , NaCl, Mg(Ac) 2 [6], fly-ash stabilized foams [7], foamed hydrogels [8], and polymer emulsions [9] have been demonstrated to play the role of insulating the active sites on coal surface from oxygen with a physicallybased principle of forming an isolation layer, which precisely determines low efficacy and poor environmental stability of this class of inhibitors. On the other hand, the chemically-based inhibitors [10][11][12][13][14] have also been described, aiming at either interrupting the free radical reactions or restraining the formation of reactive species. Ionic liquids such as imidazolium-based species [11] and phosphonium-based species [12] were added in coal samples proceeding to spontaneous combustion, which have been demonstrated to be effective on dissolving the reductive groups, delaying the decomposition of aliphatic hydrocarbon groups and the formation of carbonyl groups during coal oxidation.…”

“…Ionic liquids such as imidazolium-based species [11] and phosphonium-based species [12] were added in coal samples proceeding to spontaneous combustion, which have been demonstrated to be effective on dissolving the reductive groups, delaying the decomposition of aliphatic hydrocarbon groups and the formation of carbonyl groups during coal oxidation. Zhan et al [13] reported the effects of Na 3 PO 4 on inhibiting coal oxidation. This inorganic salt was discussed to take effect by promoting the conversion from hydroxyl into ether linkages, which improved the thermal stability of the coal.…”