Ashless herbaceous biomass for slagging and fouling reduction in solid-fuel boiler: Combustion and ash fusion characterizations

The use of herbaceous biomass as an alternative fuel for coal-fired power plants is a promising strategy for achieving carbon neutrality. However, it should be noted that herbaceous biomass contains a higher proportion of alkali metals in its ash than coal or wood pellets. This can give rise to a number of significant operational issues, including fouling and slagging, as well as environmental concerns, such as the emission of particulate matter (PM). In this study, ashless biomass technology, which selectively removes alkali metals under mild conditions, was applied to pretreat herbaceous biomass (kenaf). The combustion and emission characteristics of the pretreated biomass, including the unburned carbon (UBC), sulfur oxides (SOx), nitrogen oxides (NOx), and PM, and its slagging and fouling formation tendencies, including the capture efficiency (CE), viscosity, slagging and fouling index, and thermo-mechanical analysis, were then compared with those of coal and wood pellets using a drop tube furnace. The results demonstrated that kenaf treated with ashless biomass technology exhibited the most favorable combustion and emission characteristics (lowest UBC, SOx, NOx, and PM). Moreover, the tendency to form slagging and fouling was slightly reduced (nearly a 20% lower CE, a slightly higher viscosity, and a higher ash melting temperature than in raw kenaf). Consequently, ashless biomass technology can enhance combustion and emission characteristics by eliminating alkali metals and mitigate the formation of slagging and fouling, thereby enabling the partial utilization of herbaceous biomass as fuel in actual power plants.