coal; aerial oxidation; subaquatic oxidation; water dissolved oxygen; coal weathering

The oxidation behavior of three coal types towards molecular oxygen was investigated both in aerial and subaquatic conditions. The effects of time, temperature and coal grain size were studied and compared as basic parameters influencing the oxidation process. The obtained results showed that the influence of these factors can be similar both on aerial and subaquatic coal oxidation. Among the samples, subbituminous coal was primarily found to differ with respect to oxidation in aerial and subaquatic environment. A possible explanation for this is a change in its porous system when immersed in water. For aerial oxidation of the studied coal, oxygen consumption rates RO2 (40 °C, grain size 0.06–0.15 mm) in the range of 1·10−6 to 5·10−6 mol O2.(kg.s)−1 were found, which is approximately 2–4 times higher in comparison with RO2 for the subaquatic oxidation of the coalsamples.