Mineral matter effects in lignite gasification

Greek lignite samples with different mineral contents were gasified after drying, without any other treatment, in H2 and CO2 atmospheres, in order to study mineral matter effects on lignite gasification. Tests were performed in a fixed-bed reactor operating at ambient pressure. The alkali index (AI) was calculated for each lignite sample in an effort to correlate it with the gasification rate. The inorganic constituents in Greek lignite seem to play a controlling role in determining gasification reactivity. A reasonably good correlation exists between the alkali index and the gasification rate, which, in the studied region of alkali indices, varied almost linearly with the alkali index. For both H2 and CO2, gasification rate increased proportionately to Ca concentration, but such correlation was not evident for Na and K, possibly due to the low content and the chemical form of these elements in the organic structure. An initial increase and a subsequent decrease of gasification rate with Mg concentration was found for both H2 and CO2 gasification. As for the Fe, hydrogasification rate seems to be almost unaffected (a slight decrease is actually observed with Fe concentration), while no correlation was evident for CO2 gasification.