Comparative Study of Combustion Properties of Five Energy Crops and Greek Lignite

Solid biofuels from energy crops are widely considered as an attractive alternative for power production in dedicated combustion or cofiring applications. The aim of this work is to present fuel and ash characterization along with thermogravimetric investigations of pyrolysis and combustion behavior for five crops (cardoon, Miscanthus, Paulownia, willow, and poplar) compared with Greek lignite. Devolatilization is well modeled by three independent parallel reactions and reaches higher rates than lignite; char reactivity of woody biomass and Miscanthus was high, whereas cardoon char resembled more closely that of lignite. High potassium concentration and low melting temperatures were found for all biomass ashes; therefore, a severe/high slagging or agglomeration potential is expected. Overall, cardoon appears to be the most problematic of the investigated biomass fuels, due to high ash content, low ash melting temperature, a slower char combustion rate, and risk of chlorine corrosion; cofiring with lignite appears to be a better option for this fuel.