Catalytic gasification studies of German brown coal containing iron species

Research on the catalytic conversion of brown coal into useful combustible gases (syngas, H2 and CO) is of world-wide importance, both economically and environmentally. After crushing, mixing and washing German brown coal with acid to remove all inorganics, iron species were added at 1.7, 4.4, 7.8 and 12.4 wt % (dry basis) in the form of iron hydroxyl species to the washed coal. Samples of acid washed coal, with and without added iron, were studied under inert gas over 200 – 900 °C. The iron, after these reactions, was present in the char as Fe2O3, Fe3O4 and reduced Fe. The weight loss for all samples during pyrolysis was similar. The coals with more added iron gave larger CO2:CO ratios because an intermediate iron carbonate is formed that is subsequently thermally decomposed into reduced iron species and CO2. Coals with 1.7 and 4.4 wt % added iron gave similar weight losses to the acid washed coal for steam gasification between 200 – 900 °C. However, those coal samples containing 7.8 and 12.4 wt % added iron gave similar weight losses at temperatures up to 600 °C, but above 700 °C, the weight losses were 20-40 wt % greater, with higher yields of H2, CO2, CO and CH4, compared to the acid washed coal. The results were analysed by XRD, XPS, EDX, SIMS, AAS, and GC, and showed that Fe at 7.8% and 12.4 wt % was a good catalyst for steam gasification of brown coal at the high temperatures (700 – 900 °C). The results from the catalytic steam gasification chemistry were consistent with the mechanisms examined with molecular modelling. This research demonstrated the ability of catalytic steam gasification of brown coal to increase the yield of hydrogen, pointing to the possible development of a practical and economic gasification process.

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the Department of Chemistry, School of Molecular Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora.