Abstract
Existence of sulfur compounds in coal limits its industrial application due to environmental as well as technical problems. In an extensive work, attempts have been made to desulfurize high sulfur Iranian coals for coke making for the steel industry. For this purpose, several physical, biotechnological and chemical methods for upgrading these coals before combustion are used. This paper attempts to demonstrate the potential of supercritical methanol/water and methanol/NaOH solvent mixtures for the removal of sulfur from an Iranian coal with total sulfur of 3.1%. Supercritical fluids have unique capability in enhancing the solubility of organic components. A batch reactor, 7 liters, equipped with an agitator was used in this study. The effect of methanol and caustic concentrations, reaction temperature and reaction time on removal of ash and sulfur, plastometry properties and recovery percent was investigated. The effect of each variable on the desulfurization of the coal was evaluated by measuring the sulfur content, the ash yield and the coal yield. Depending on the desulfurization conditions, the total sulfur reductions were varied from 7.45% to 30%. Desulfurization rate has been enhanced by increasing temperature and reaction time. It was found that sulfur removal increased with an increasing concentration of NaOH. In fact, NaOH can break the C-S bonding in coal, which enables greater penetration of methanol.
