Determination of ash forming characteristics and fouling/slagging behaviours during gasification of masson pine in a fixed-bed gasifier

Abstract

In this paper, fly ash and bottom ash produced from the gasification of pine sawdust in a fixed bed gasifier were compared in details to investigate the ash forming characteristics and fouling/slagging behaviours. For this purpose, a detailed comparison of fly ash and bottom ash was carried out. It was found that compared with the ash composition of raw pine sawdust, gasification ashes showed higher contents of alkali metals (K, Na) and Cl. S. Both the bottom ash and fly ash were strongly crystalline, with calcite as the prevailing phase. The ash fusion temperatures for fly ash were higher than those for bottom ash, while the interval between the deformation temperature and softening temperature for bottom ash (88 °C) was larger than that for fly ash (73 °C), suggesting the higher fouling/slagging propensity of bottom ash. The Si/(Ca + Mg) ratio for the bottom ash (1.10) was lower than that for fly ash (1.29), further indicating the low melting of bottom ash. From a mineralogical standpoint, the major difference between fly ash and bottom ash was that the former possessed a higher content of potassium-rich salts that facilitated the adhesion of small particles to larger particles during biomass gasification process. • This study reported ash forming characteristics in biomass fixed-bed gasification. • A detailed comparison of fly ash and bottom ash in terms of ash slagging was given. • The composition and micro-morphology of bottom ash and fly ash were both analyzed. • The Si/(Ca + Mg) ratio of bottom ash (1.10) was lower than that of fly ash (1.29). • The ash fusion temperatures for the fly ash were higher than those for bottom ash.