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The floatability of oxidized coal was investigated by means of electrokinetic studies, contact angle measurements and flotation tests. Electrokinetic measurements showed that the zeta potential of unoxidized and oxidized coal samples depends on pH. Hydroxonium and hydroxyl ions are potentially significant ions, both for oxidized and unoxidized coal. Increasing oxidation times decreased the measured...
Montana Rosebud coal and North Dakota lignite have been oxidized in a fluidized bed reactor at 200°C, with air at 0.2, 0.6 and 1 MPa for reaction times up to 4 h. Oxidized samples were analysed by reflected light microscopy to investigate the variation of reflectance, formation of rims and changes in maceral morphology. The most remarkable changes concerned the vitrinite. Exinite exhibited an increase...
The effect of oxidation on the macromolecular structure of four coals of rank 902 to 204 in the British Coal classification scheme was investigated. Various particle size ranges of the coals were oxidized in air at 200°C for 24 h. Oxidation led to an increase in the extent of swelling in pyridine, which indicates a decrease in the covalent cross-link densities of the coals. Unlike that of the initial...
The influence of the addition of SO 2 , Na 2 SO 3 or CaSO 3 1H 2 O to aqueous suspensions of Siersza coal-cleaning refuse on its chemical transformations during oxidative alkaline treatment was investigated. Experiments performed in a froth column under mild conditions (90°C, 0.1 MPa) resulted in (1) marked degradation of the coal to solubilized products including...
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