Some recent advances in the understanding of the pyrolysis and gasification behaviour of Victorian brown coal

The brown coal in the Latrobe Valley, Victoria, Australia, has many unique structural features and properties. The brown coal has a very low ash yield and contains highly dispersed alkali and alkaline earth metallic (AAEM) species, either as carboxylates forming part of its organic matter or as NaCl dissolved in its moisture. Owing to its unique structural features and properties, the brown coal behaves very differently from many other solid fuels such as biomass, bituminous coals and anthracites. For example, the highly reactive nature of its volatiles, the vulnerable nature of its nascent char and the presence of finely distributed AAEM species mean that the volatile–char interactions, a common phenomenon in all gasifiers, especially in the fluidised-bed gasifiers, would influence almost every aspect of its pyrolysis and gasification behaviour. Some recent progress in the understanding of the pyrolysis and gasification behaviour of Victorian brown coal will be reviewed in this paper. After a brief account of the effects of AAEM species on the pyrolysis yields, the factors influencing the volatilisation of AAEM species will be summarised. This will be followed by the discussion of the factors influencing the reactivity of brown coal char and the catalytic reforming/cleaning of volatiles and gasification products by char-supported catalysts. The effects of dewatering/drying on the pyrolysis behaviour of Victorian brown coal and the conversion of pollutant-forming elements will be mentioned briefly. The progress in the fundamental understanding of the pyrolysis and gasification behaviour of Victorian brown coal has laid solid foundation for the further development of advanced gasification technologies for the clean and efficient utilisation of this cheap but important resource.