A study of the water vapour/coal system has shown that oxidized coal readily reacts at 523, 423 and 313 K to evolve almost exclusively CO, (according to the rank in the 10(-6)-10(-5) mol g-1 range). In contrast, with unoxidized anthracite a drastic reduction in CO2 evolution is observed. When a C2H2 soot is substituted for the coal, the same behaviour is observed, showing that the water vapour interaction involves the organic part rather than the mineral part of the coal. Similar behaviour has been observed with other carbonaceous materials such as activated carbon and carbon black. In the light of these results, the role of natural or added moisture is examined: for the case of wet treatment of coal (milling or demineralization) and also its storage under inert gas. Special attention is focused on the multiple roles of water vapour in the weathering of coal.
