Partitioning of K, Cl, S and P during combustion of poplar and brassica energy crops

Abstract K-, Cl-, S- and P-release from a herbaceous (brassica) and a short rotation coppice (poplar) cultivated in the Mediterranean region, have been investigated under combustion conditions [500–1100 °C]. Contrary to brassica, Cl- and S-release from poplar were substantial for all temperatures tested. Low-temperature [500–700 °C] Cl-release from the high-Cl brassica appeared to be primarily limited by the fuel chemical composition and secondarily by interactions of the ash-forming elements with the fuel organic matrix. Below 700 °C, Cl-release was nearly 50%, whereas complete dechlorination resulted around 800 °C. S-release from brassica was up to 40% at low temperature. Above 1000 °C, additional S-release was observed presumably by sulfate dissociation. K-release was linked to Cl-release around 700 °C and, gradually increased afterwards. At 1100 °C, nearly 60% of K in poplar was retained, whereas around 40% of K and S remained in brassica ash. P-release was not significant for both energy crops at tested conditions.