The iron mineral changes occurring in lignite coal during gasification

摘要

Representative lignite and gasified material samples were retrieved form a cooled down gasifier. The samples were taken at various heights in the gasifier that operated on lignite, under stable conditions. The proximate analyses, ash composition and temperature in the gasifier were determined according to standard procedures. The main minerals found in the present investigation were bassanite, illite, quartz, kaolinite, calcite and the only iron bearing mineral was found to be pyrite. The trend in the estimated particle surface temperature profile shows an increase in the drying, pyrolysis, gasification and combustion zones from about 300 °C to just over 900 °C. About 1/3 down the gasifier, an average particle temperature of about 400 °C and particle surface temperature of about 600 °C was measured where pyrite conversion started. About 2/3 down the gasifier, where an average temperature of about 700 °C and particle surface temperature of about 900 °C was measured, all the pyrite was converted and in the bottom part of the gasifier, oxidation of the iron started to play a role and hematite and an iron containing glass formed at an average temperature of > 800 °C and surface temperature of 900 °C.