Effect of additives in increasing ash fusion temperature during co-firing of coal and palm oil waste biomass

Biomass has the potential to cause slagging and fouling during combustion due to its high potassium and high chlorine contents, as well as its low ash melting temperature. This study aims to identify suitable additives for co-firing of coal with palm oil waste. Magnesium, aluminosilicate, aluminum, silicate, calcium, and potassium-based additives were tested at a dosage of 6 wt%. The results indicate that magnesium-based additives significantly increase MgO content, while aluminum-based additives considerably decrease the SiO₂/Al₂O₃ ratio. Both of these effects contribute to an increase in the ash fusion temperature (AFT) of the four samples, with an average percentage increase in the ash fusibility index (AFI) above 25 %. Additionally, additives like CaHPO₄, CaO, kaolin, and K₂CO₃ consistently raise the AFT, although the average percentage increase in AFI is lower than 25 %. However, further investigation is required to determine optimal dosage of additives and address other issues, such as corrosion tendency.