Phase changes in mineral matter of North Dakota lignites caused by heating to 1200 °C

摘要: Abstract Changes in structures of minerals taking place lignitic coals during combustion were investigated by first concentrating the mineral matter coal low-temperature ashing and then heating at 100 °C intervals from 200 °C–1200 analysing major phases X-ray powder diffraction. Samples high low sodium contents analysed to determine differences with varying contents. Quartz bassanite identified as all ten lignite samples, pyrite calcite eight samples. Kaolinite was only clay appeared nine Those samples a oxide content 8.56 wt % or greater, showed nitrate phase matter. When heated higher temperatures, quartz 1200 five stable 1000 Anhydrite 600 °C–800 °C, appearing some persisting 1100 Hematite found be seven having an overall temperature range 300 °C–1000 °C. Magnetite detected 800 hercynite forming phase, after magnetite, two The solid solution series gehlenite-akermanite although they 900 formed sulphates intermediate temperatures silicates temperatures. Low Sodium bredigite, calcium silicate,