A comprehensive evaluation of cofiring biomass with coal and slagging-fouling tendency in pulverized coal-fired boilers

Cofiring coal with various biomasses has received much attention due to environmental factors and is considered a low-cost option. Although cofiring coal with biomass seems feasible, it potentially produces ash, which causes issues in boilers, such as fouling and slagging. This paper comprehensively investigates combustion performances and slagging and fouling behaviors during cofiring biomass and coal. A thorough examination is conducted to investigate the slagging-fouling tendencies employing ash indices. Thermogravimetry-differential scanning calorimetry and a pilot combustion experiment using a drop tube furnace (DTF) are performed to investigate the thermal behavior of the materials, including ash observation using scanning electron microscopy-energy dispersive X-ray analysis and X-ray diffraction systems. Results show that cofiring coal with 25% biomass (mixture of empty fruit bunch and palm frond) has the best combustion performance. It is found that cofiring coal with 25% biomass, either empty fruit bunch or frond, increases the risk of slagging with evidence of the decrease of ash fusion temperatures, deposition material, and sticky material in the probe. The results can provide useful information about cofiring behavior and slagging-fouling tendencies before being implemented into a real plant.