Inhibition of spontaneous combustion of coal

This report describes laboratory studies conducted to evaluate the effectiveness of 10 additives to inhibit the self-heating of coal. Aqueous additive solutions were applied to a bituminous coal with a high spontaneous combustion potential, and the minimum, self-heating temperatures (SHT's) of the dired coal-additive mixtures were determined in the Bureau's adiabatic heating oven. The relative effectiveness of the additives was determined by the observed changes in the minimum SHT's of the mixtures or by the time required for the sample temperature to reach 150{degrees}C, compared with the untreated coal and coal-water blank. Sodium nitrate, sodium chloride, and calcium carbonate were found to be the most effective inhibitors, followed by ammonium dihydrogen phosphate, calcium chloride ammonium chloride, sodium acetate, and potassium chloride. Two additives, sodium formate and sodium phosphate, promoted the self-heating process. Differential scanning calorimetry experiments on the coal-additive mixtures show that reactions occured between the coal and some of the additives, but these reactions did not infuluence the self-heating process.