Influence of water-washing pretreatment on ash fusibility of biomass

As the carbon-neutral fuel, biomass has shown great potential to partially substitute fossil fuels. However, the application of biomass combustion in boiler was restricted by the biomass compositions. To improve the ash fusibility performance of biomass, water washing pretreatment was proposed. The influences of water washing on ash composition, ash fusion temperatures (AFTs), and ash dynamic behavior during fusion process were investigated through experimental methods and thermodynamic equilibrium calculations. The results show that water washing could increase the initial deformation temperature of biomass ash by removing alkali metals. The K2O removal efficiency is within 69%-90% for six biomass fuels. Traditional fouling and slagging indexes could be employed to predict the ash fusibility of corn stalk, wheat straw, rice straw and rice hull. But these indexes are not suitable for that of candlenut wood or cotton stalk. Furthermore, a convenient and effective method to study the dynamic behavior of biomass ash during fusion process is proposed. It could reveal the interaction of solid and liquid phases in ash. The effect of water washing on AFTs could be explained by thermodynamic equilibrium calculations. Finally, 30 degrees C is recommended as the water washing temperature to adjust the ash fusibility of biomass.

Automated summary

Biomass has the potential to partially replace fossil fuels as a carbon-neutral fuel. Water washing pretreatment can improve the ash fusibility performance of biomass, and the effect of water washing on ash fusion temperatures can be explained through thermodynamic equilibrium calculations. Additionally, a convenient method to study the dynamic behavior of biomass ash during fusion process is proposed.