Volatilisation of alkali and alkaline earth metallic species during the pyrolysis of biomass: differences between sugar cane bagasse and cane trash

Sugar cane bagasse and cane trash were pyrolysed in a novel quartz fluidised-bed/fixed-bed reactor. Quantification of the Na, K, Mg and Ca in chars revealed that pyrolysis temperature, heating rate, valence and biomass type were important factors influencing the volatilisation of these alkali and alkaline earth metallic (AAEM) species. Pyrolysis at a slow heating rate (∼10 K min−1) led to minimal (often <20%) volatilisation of AAEM species from these biomass samples. Fast heating rates (>1000 K s−1), encouraging volatile-char interactions with the current reactor configuration, resulted in the volatilisation of around 80% of Na, K, Mg and Ca from bagasse during pyrolysis at 900 °C. Similar behaviour was observed for monovalent Na and K with cane trash, but the volatilisation of Mg and Ca from cane trash was always restricted. The difference in Cl content between bagasse and cane trash was not sufficient to fully explain the difference in the volatilisation of Mg and Ca.