coal; low-temperature oxidation; inhibition; calorimetry

Interactions in the system ?coal - chemical additive - oxygen? were studied at temperature 30°C with the aim to recognise inhibitors of coal oxidation process that are able to modify coal surface in chemical way. Three coals of different rank were tested. As possible inhibitors, 14 aqueous solutions (10 wt%) of both inorganic (chlorides, sulphates, nitrates, phosphates, sulphites) and organic (formates, acetates, urea, thiourea) substances were examined. Action of additives on coal was evaluated from heat effect during immersion of the coal in the additive solution. It was found that the most of the studied substances proved immersing heats quite comparable with that of pure water. However, rather chemical action was ascertained for sodium sulphite, phenol, urea and/or thiourea with heat effects several times exceeding heats for pure water.