EVOLUTION OF THE ORGANIC SULFUR AND OTHER COMPONENTS DURING NITRIC-ACID LEACHING OF MEQUINENZA COAL

In this work, desulfurization by nitric acid leaching is studied in Me quinenza coal, whose characteristics are very low contents of sulfide and sulfate sulfurs in comparison with a very high content of organic sulfur that allows the selective attack on organic sulfur with regard to carbon to be clearly determined. Organic matter is made soluble at high temperatures and there is a threshold temperature for the same. T he reaction involves an increase of nitrogen and oxygen, and a decreas e of carbon contents. These variations reach a limit as the solubility of the organic matter progresses. The attack on inorganic sulfur is v ery fast, producing an initial leap as in the attack on organic sulfur , while the solubilization of organic matter is slower, because of whi ch shorter times should be applied for the purpose of desulfurization. (C) 1997 Elsevier Science Ltd.