Transformation of the Fe-mineral associations in coal during gasification

The mineral matter associated with coal undergoes various transformations during the coal gasification process. Optimisation of the gasification process is necessary in the coal to liquids technology. The principle aim of this investigation was to determine the changes that the Fe-containing minerals and mineral associations undergo during gasification of coal. Due to the complexity of the counter-current coal-gas process used, a gasifier dissection was undertaken on one of the Sasol gasifiers. Detailed characterisation profiles of various properties of the coal were undertaken after a commercial-scale gasifier was shutdown for routine maintenance of which the Moessbauer spectroscopy technique will be described here. Representative samples from the gasifier were extracted after sufficient cooling was done to allow the safe turn-out of the gasifier. In the coal samples that entered the gasifier, pyrite was the abundant Fe-containing mineral, whilst the pyrite changed gradually to form, in conjunction with the SiO2 and Al2O3 present in the coal, a Fe-containing glass and hematite at the bottom, or ash grate of the gasifier.