Vitrinite maceral flotation kinetic constants are important in designing flotation columns to be used in separating this maceral group. This work shows the effect of pH, air speed and froth concentration on vitrinite maceral flotation kinetic constants by using two Colombian bituminous coals: El Cerrejón (Guajira) and La Jagua (Cesar). A 5 m high pilotscale flotation column was used in all runs. The samples were processed using 4-10 pH, 0.7-2.1 cm/s air speed and 2-6 ml/kg of coal froth concentration ranges. Both La Jagua and El Cerrejón coals showed high kinetic constants figures in acid conditions (0.692 min-1 at pH 4 and 0.559 min-1 at pH 5, respectively). The results showed that, generally, the best operating conditions for obtaining high vitrinite maceral kinetic constant values were having an acid medium and low air flow and froth concentration.

This work evaluated the char morphology of beneficiated and original coal (without beneficiation) from four Colombian coalmines: Cerrejón (La Guajira), La Jagua (Cesar), Guachinte (Valle del Cauca) and Nechí (Antioquia). Column flotation was used to obtain beneficiated coal, whereas a drop tube reactor at 1,000oC, 104 oC/s heating rate and 100 ms residence time was used to obtain char. The chars were analysed by image analysis which determined their shape, size, porosity and wall thickness. It was found that char morphology depended on coal rank and maceral composition. Morphological characteristics like high porosity, thinner walls and network-like morphology which are beneficial in improving combustion were present in vitrinite- and liptinite-rich lowest-ranking coals. Beneficiated coals showed that their chars had better performance regarding their morphological characteristics than their original coal chars.