Direct Determination of Organic Sulfur in Raw and Chemically Desulfurized Coals

摘要

An electron beam technique has been developed for the direct determination of organic sulfur in coal. The technique utilizes a scanning electron microscope (SEM) coupled with an energy-dispersive x-ray (EDX) analysis system with quantitative data reduction capabilities. The direct measurement of organic sulfur is performed on a number of particles of the maceral vitrinite, previously located within the mounted coal sample by reflected light microscopy. The particles are first examined by SEM at about 5000x magnification to allow proper identification of most mineral inclusions and to avoid these areas during analysis. The x-rays generated from an area about 3 mu m in diameter are monitored quantitatively by EDX for sulfur and iron, as well as for calcium, aluminum, and silicon. In the absence of the other elements which ensures the lack of mineral phase inclusions at the point of analysis, the sulfur value obtained is taken as a measure of the organic sulfur in coal since it represents sulfur occurring apart from any mineral phase. In addition to the average organic sulfur value, the results obtained by this technique allow also an estimation of the intra- and inter-particle variation in the organic sulfur level. Since about 12 particles are tested at 2 points each, statistical methods can be used to construct confidence bands about the mean sulfur levels and estimate standard deviations in sulfur levels within the particles and between the particles. (ERA citation 08:050528)