Yukio Enda

Dynamic behavior of trace elements during pyrolysis of coals

Release behavior of sodium and potassium was followed during pyrolysis of coals in a nitrogen stream up to 1200°C. Sodium and potassium in coal and char were classified into five fractions by a serial dissolution method with H 2 O, CH 3 COONH 4 , HCl, H 2 SO 4 and HF solutions. Distribution of selenium in coal matrix and its release behavior were observed for density-separated samples during pyrolysis. The results showed that lower temperature release of potassium was observed during pyrolysis comparing to the sodium release. Fractions of H 2 O soluble and CH 3 COONH 4 soluble decreased, and fractions of H 2 SO 4 soluble increased with heat treatments for both alkali metals. Selenium was distributed unevenly in the coal matrix and its content was correlated well with pyritic sulfur content but not with organic sulfur content.

XANES analysis of sulfur form change during pyrolysis of coals

Three kinds of coal and their density separated samples were rapidly pyrolyzed in a free-fall reactor under a nitrogen stream at a terminal temperature of 1253 K. X-ray absorption near edge structure analysis was applied to directly determine the sulfur forms in the coal and pyrolysis char. The results showed that the low-density group contained sulfide and sulfoxide, which could contribute to the high extent of organic sulfur removal. Thermally stable thiophenic sulfur was observed in the higher density groups as a major form of organic sulfur.